Bielersee, Switzerland Bielersee (47.10 N, 7.10 E, 429m above sea level) is an elongated lake, ca 14.5 km long and with an average width of ca 3km. There are at least seven inflow streams feeding the lake and an outflow from the northeast end (now canalised). The level of the lakes was lowered by ca 2.15m in 1872-4, resulting in the exposure of a spit of land (heidenweg) joining St. Peter's Island to the southwest shore. The average water level during the period between 1941 and 1955 was 429.14m. The catchment bedrock is Quaternary molasse, with morainic cover. The lake sediments provide a record back to ca 13,000 yr B.P. (Ammann-Moser, 1975). The stratigraphy has been reconstructed from a transect of 12 cores (H1, H2 ... H12) across the spit (Ammann-Moser, 1975). There are two additional cores (H13, H14) from the lake. Changes in water level have been reconstructed on the basis of changes in lithology, the occurrence of sedimentary hiatuses and the location of lake-marginal archaeological sites (Ammann-Moser, 1975; Ammann, 1982). The interpretation of lake status changes given here follows this reconstruction. There are no radiocarbon dates from the cores; the chronology is based on terrestrial pollen correlation with the regional pollen stratigraphy (Ammann-Moser, 1975). Although there are local differences, the cores all show the same basic stratigraphy. Relatively high lake levels during the Older Dryas, Bölling and Alleröd are shown by a high sediment limit. The absence of sediments dating to the Younger Dryas in Cores H5, H6, H7 and H8 indicates a major drop in lake level. Submerged shore terraces appear to date to this interval of shallower conditions. Sediments dating to the Preboreal and Boreal (ca 10,000 to 7500 yr B.P.) are only found in the deepwater cores (e.g. H13), suggesting that shallow conditions persisted into the early Holocene. However, archaeological evidence from the site at Twann seems to indicate that the lake had risen to ca 427m by shortly after 9000 yr B.P. A slight increase in water depth ca 6000 yr B.P. is shown by an increase in the sediment limit to between cores H10 and H11. A major increase in water depth is registered by sedimentation in all the cores after ca 4900 yr B.P. A return to shallower conditions during the Bronze Age is marked by an hiatus in sedimentation in the shallower-water cores. Lake levels started to increase again after ca 3000 yr B.P. In the status coding, low (1) is indicated by evidence of lake-levels below 425m; intermediate (2) by lake levels between 425-429m; and high (3) by lake-levels above 429m. References Ammann, B., 1982. Säkulare Seespiegelschwankungen: wo, wie, wann, warum? Mitteilungen der Naturforschenden Gesellschaft in Bern 39: 97-106. Ammann-Moser, B., 1975. Vegetationskundliche und Pollenanalytische Untersuchungen auf dem Heidenweg im Bielersee. Beiträge zur Geobotanischen Landesaufnahme der Schweiz 56, 76 pp. Coding 13000-10500 yr B.P. intermediate (2) 10500-7500 yr B.P. low (1) 8500-7400 yr B.P. intermediate (2) 7400-5100 yr B.P. low (1) 5100-1900 yr B.P. intermediate (2) 1900-0 yr B.P. high (3) Final coding: June 1989 Coded by: SPH Hobschensee, Switzerland Hobschensee (also known as Hopschusee, 46 15'N, 8 E, 2017m above sea level) is located in the Simplon pass, south of Brig. The lake is small (< 1 ha) with a diameter of 130m and a maximum depth of 3.25m. The lake is surrounded by Carex swamp and there is a well-developed fringe of floating-leaved aquatics (Sparganium and Potamogeton). The Simplon pass (2005m above sea level) is one of the lowest passes in the central Alps. High mountains with glaciers rise to the west and east of the pass. The bedrock is gneiss and schist. The pass was covered by ca 200m of ice during the last glacial maximum (Müller, 1984). The ice apparently melted early in the late glacial, leaving a typical glacial landscape of rounded bedrock hills and numerous small basins. Hobschensee is located in one of these basins. A SW-NE transect of nine cores across the basin provides information on the stratigraphy of the bottom deposits (Lang and Tobolski, 1985). Two cores, HO1 from littoral peat swamp and HO2 from the deepest part of the lake, have been used for macrofossil analyses (Lang and Tobolski, 1985). The HO2 core is 6.55m long and HO1 is 4.45m long. There are three additional cores (Bohrung I, Bohrung II, Profile SH) from the marginal zone. Bohrung I was taken 18m away and Bohrung II 27m away from the western shore (Welten 1982). Bohrung I was taken on a lake terrace which is one meter higher than the site of Bohrung II. Profile SH (Küttel, 1979) is a littoral profile in the southwest of the basin. There is no information about the topmost part (1.69m) of this core. Bohrung I, Bohrung II and Profile SH were taken a few metres northeast of the HO1 core (Lang and Tobolski 1985). Changes in water depth are reconstructed from changes in lithology, aquatic pollen and macrofossils, and diatoms (Lang and Tobolski, 1985; Welten, 1982; Küttel, 1979; Marciniak, 1988). Diatom analysis is available only for the bottom of the HO2 core. The different cores are correlated by terrestrial pollen assemblages. The chronology is provided by seven radiocarbon dates from the Bohrung II core and a single date from the Profile SH core. There are two additional dates from near the base of Bohrung II, but these yield anomalous ages (Welten, 1982). The late Pleistocene chronology is based on the regional pollen chronostratigraphy (Welten, 1982; Küttel, 1979; Lang and Tobolski, 1985). The basal unit is a mineral deposit, variously described as clay/silt (Küttel, 1979; Lang and Tobolski, 1985) or grey sandy loam (Welten, 1982). Diatoms are rare (Marciniak, 1988). The unit is dated on the base of the pollen stratigraphy to the Bölling (pre 12000 yr B.P., Küttel 1979, Welten 1982). The overlying unit is a fairly mineral-rich gyttja, described variously as a medium brown clay gyttja (Lang and Tobolski, 1985; Küttel, 1979) and as an olive/grey coloured gyttja (Welten, 1982). The increase in organic content suggests shallower conditions, as pointed out by Lang and Tobolski (1985). The aquatic assemblage contains Nitella and Ranunculus, consistent with shallow conditions. The diatom assemblages vary abruptly (Marciniak, 1988), although Fragilaria spp. are extremely abundant (80-85%). Both the dominance of Fragilaria and the highly variable nature of the assemblages are consistent with shallow conditions. Cladocera are also extremely abundant (Lang and Tobolski, 1985). Two samples from this unit have been radiocarbon dated to 10430±250 yr B.P. and 12580±200 yr B.P. (Welten, 1982). The very low apparent sedimentation rate (< 0.002 cm/year) between the two samples, which is consistent with a marked increase in pollen concentration, suggests that there may have been a depositional hiatus during the phase of shallow conditions. Alternatively the radiocarbon dates may be in error. According to the pollen stratigraphy, which suggests that this unit was formed in the Alleröd (ca 12000 - 11000 yr B.P., Welten, 1982), the radiocarbon dates are respectively too young and too old. Welten (1982) suggests that the dates may have been affected by the contamination, and Lang and Tobolski (1985) suggest they may be unreliable because of low amounts of carbon. The overlying unit is a mineral deposit, variously described as sandy loam (Welten, 1982), silt (Küttel, 1979) or grey clay/silt (Lang and Tobolski, 1985). The reduction in organic matter suggests increased water depth after ca 11000 yr B.P. Cladocera decline abruptly in abundance, as do the remains of aquatic plants (Lang and Tobolski, 1985), consistent with increased water depth. The diatom assemblages are characterised by a decline in the importance of Fragillaria (Marciniak, 1988), consistent with a gradual increase in water depth. The overlying unit is gyttja. The increase in organic matter is consistent with reduced water depth. Two radiocarbon samples from near the base of the gyttja in the marginal core Bohrung II, yield radiocarbon dates of 9000±150 and 9530±250 yr B.P. The extremely low sedimentation rate (ca. 0.002 cm/year) suggests the presence of a a sedimentary hiatus and argues for very shallow conditions at the beginning of gyttja deposition. The base of the gyttja in Bohrung II is olive/grey in colour and apparently not very rich in organic matter. This and the rather low sedimentation rate in this part of the core (0.01 cm/year) is consistent with shallow conditions. The aquatic assemblage, which is characterised by Potamogeton and Ranunculus (Lang and Tobolski, 1985), is consistent with fairly shallow conditions. An increase in water depth sometime between 8730 and 7980 yr B.P. is indicated by the transition to dark brown, homogenous detrital gyttja. An increase in sedimentation rate (0.4-0.6 cm/year) is consistent with increased water depth. The macrofossils indicate a very diverse aquatic assemblage, including Sparganium and Hippuris. Cladocera are also abundant (Lang and Tobolski, 1985). A decrease in water depth ca 2500 yr B.P. is indicated by a time-transgressive transition to light olive brown detritus gyttja. These more mineral-rich sediments are characterised by a marked increase in macrofossils of Sparganium, which Lang and Tobolski (1985) argue is consistent with hydroseral development in the basin. The uppermost unit in the marginal cores is Carex peat. The transition to peat deposition in Bohrung II is dated to ca 600 yr B.P., but appears to have taken place somewhat earlier in other littoral cores. In the status coding, an hiatus is indicated by (0); low (1) is indicated by mineral-rich, olive-coloured gyttja, with abundant aquatic macrofossils including Ranunculus; intermediate (2) by brown detrital gyttja, with high sedimentation rates; high (3) by mineral deposits, with few aquatics. The uppermost gyttja and peat are considered to mark hydroseral development and coded accordingly. References Küttel, M., 1979. Pollenanalytische Untersuchungen zur Vegetationsgeschichte und zum Gletscherrückzug in den westlichen Schweizer Alpen. Berichte der schweizerischen botanischen Gesellschaft 89: 9-62. Lang, G. and Tobolski, K., 1985. Hobschensee - late-glacial and holocene environment of a lake near the timberline. Dissertations Botanicæ 87: 209-228. Marciniak, B., 1988. Diatoms in bottom sediments of Lake Hobschen, Simplon, Switzerland, Preliminary report. In: Lang, G., and Schlüchter C., (editors) 1988. Lake, Mire and River Environments During the Last 15000 Years. Balkema. Rotterdam. P. 31-39. Welten, M., 1982. Vegetationsgeschichtliche Untersuchungen in den westlichen Schweizer Alpen: Bern-Wallis. Denkschriften der Schweizerischen Naturforschenden Gesellschaft 85: Textheft und Diagrammheft. Radiocarbon dates B-634 660±80 0.97m, brown gyttja, Bohrung II B-669 3230±100 2.01m, brown gyttja, Bohrung II B-635 4500±300 2.46m, brown gyttja, Bohrung II B-635E 5040±150 2.775m, brown gyttja, Bohrung II B-3038 7640±200 3.25-3.38m, brown gyttja, Profile SH B-610 7730±180 3.90m, brown gyttja, Bohrung II B-609 9000±150 4.05m, olive grey-brown gyttja, Bohrung II B-530 9530±250 4.06m, olive grey-brown gyttja, Bohrung II B-529 10430±250 4.90m, olive grey gyttja, Bohrung II, ATY B-608 12580±200 4.94m, olive grey gyttja, Bohrung II, ATO Coding -12000 yr B.P. high (3) 12000-11000 yr B.P. low (1) 11000-9500 yr B.P. high (3) 9600-9000 yr B.P. hiatus (0) 9150-7980 yr B.P. low (1) 8730- 0 yr B.P. intermediate (2) Preliminary coding: 17/1/1994; Final coding: 25/2/1994 Coded by: XY, SPH Léman, Switzerland Lake Léman (also known as the Lake of Geneva: 45 52'-46 41' N, 6 3'-8 28' E, 372m above sea level) lies in the southwest of the Swiss Plateau and is one of the largest basins draining the northern slopes of the Alps (Serruya, 1969). The lake is ca 72km long, with an average width of 8.1 km and an area of 58,200ha. The maximum water depth is 309.7m and the average depth is 152.7m. The lake is fed by numerous rivers, but the Rhône is the major source of inputs (ca 75%), and overflows via the Rhône westwards. The lake has been artificially maintained at a level of 372m above sea level since 1892 (Magny and Olive, 1981). In the period between 1774 and 1892, the elevation fluctuated within ±1.3m of 372m (Forel, 1892-1904; Magny and Olive, 1981). The catchment area is 797,500ha. The average catchment elevation is 1,670m above sea level, but the highest peaks reach elevations of up to 4,634m above sea level (Mont-Rose). The highest peaks are glaciated, and it is estimated that glaciers cover 10-11% of the catchment area (Serruya, 1969). The basin was occupied by the Rhône glacier during the last glacial maximum. Deglaciation began ca 18,000 yr B.P., but was interrupted by several readvances. The most important of these occurred at ca 15,000 yr B.P., during the Montossey stadial (Gaillard, 1985). These advances are associated with terrace formation around Lake Léman, such as the 540m terrace dated to 14,000 yr B.P. The Rhône glacier retreated from the basin after 14,000 yr B.P. (Gaillard, 1985). Lacustrine deposition within the basin is thought to have begun immediately after the retreat of the glacier, and the oldest lacustrine beds are therefore correlated with terrace formation (Villaret and Burri, 1965). The catchment is underlain by crystalline bedrocks and Tertiary molasse, and the surface materials include morainic deposits. The stratigraphy of the bottom deposits has been reconstructed by geophysical studies and from 59 cores (Serruya, 1969). The cores have been subjected to detailed lithological analysis, but unfortunately they are primarily dated palynologically. During the Oldest Dryas, the Bölling and the Older Dryas, the sediments are represented by sand beds separated by thin clay layers. During the Preboreal, the sediments are either non- or only weakly-laminated. Varved sediments are characteristic of the Boreal. During the Atlantic, the varves are thin and dark-coloured. Sediments deposited after the Atlantic are very fine-grained. Several authors (e.g. Olive, 1972; Gallay and Kaenel, 1981; Gaillard et al., 1981; Magny and Olive, 1981) have presented lake-level curves based on different sources of information. The reconstruction given here is based on a consensus of the available information, but broadly follows previous reconstructions. The chronology is based on radiocarbon dating (Gallay and Corboud, 1979; Gallay et al., 1980; Gallay and Kaenel, 1981; Gaillard et al., 1981; Håkansson, 1980; Magny and Olive, 1981; Gabus et al., 1987; Peese, 1994, pers. comm). There are three terraces (30m, 10m, 3m) associated with Lake Léman (Villaret and Burri, 1965). The highest is a kame terrace, and has been dated to ca 13000-13200 yr B.P. (Olive, 1972; Gabus et al., 1987). However, the 10m and 3m terraces are of lacustrine origin and provide evidence that the lake was higher than present (Chaix, 1981). The 10m terrace is chiefly composed of lacustrine sands and gravels. The occurrence of at least 3 thin peats beds within these deposits is interpreted as indicating minor fluctuations in the level of the lake (Gallay and Kaenel, 1981). Gallay and Kaenel (1981) suggest that terrace formation occurred during the Alleröd. Gabus et al. (1987) obtained a radiocarbon date of 10520+140 yr B.P. (Ly-3300) on a peat bed in the uppermost part of the terrace deposits. This would suggest a slightly younger age for terrace formation. The unit overlying the tarrace deposits consists of yellow sand of terrestrial origin. This unit contains archaeological material of Middle Bronze and Roman age. The stratigraphy of the 3m terrace has been described by Villaret and Burri (1965) and Gallay and Kaenel (1981). The lowermost beds (3-6) are of lacustrine origin, and consist of grey-blue silty clay (6), yellow lacustrine sands (5), lacustrine chalk (4) and grey lacustrine sands (3). Radiocarbon dating indicates that these units were formed between ca 12100 and 12800 yr B.P. The contact with the overlying unit is discordant, suggesting a break in deposition corresponding to a long interval when the lake fell below 376m (Villaret and Burri, 1965). The overlying bed (2) is composed of lacustrine sands and gravels, and marks the transgressive phase when the 3m terrace was formed. A sample from this unit was radiocarbon dated to 4330+40 yr B.P. (GrN-5602). The presence of a lense of lacustrine chalk overlying this unit at one site (Bâtiment X) suggests a brief interval of high lake level around the time the 3m terrace was formed. The uppermost unit is a more or less clayey sand, rich in pulmonate molluscs. In some locations (e.g. at the excavation site of the Roman basilica) this layer consists of yellow sands apparently of terrestrial origin, and containing abundant archaeological material. Radiocarbon dates from this unit are in the range 3390-2590 yr B.P., indicating that the lake had fallen from its high level by ca 3400 yr B.P. Given that the basal lacustrine beds beneath the 3m terrace were deposited during the interval when the 10m terrace was formed, the dicordant nature of the upper contact indicates that the lake level fell well below 376m after ca 10,500 yr B.P. Additional evidence for the early Holocene history of the lake is provided by the existence of an arcaheological site at Vionnez (Gallay et al., 1980), at an elevation of ca 369m a.s.l. This site has been radiocarbon-dated to the Mesolithic (?8500-7700 yr B.P.). Magny and Olive (1981) interpret this site as showing a gradual decline in water level from ca 10,000 yr B.P. to a minimum (369m above sea level) at 8200 yr B.P. There is little concrete evidence about the lake level during the mid-Holocene. According to Gaillard et al. (1981), the evidence from the available pollen cores is consistent with water levels about the same as today. Magny and Olive (1981) indicate that sediments representing the Atlantic period are not found in the littoral zone of Lake Léman, suggesting that the lake was lower than today. This suggestion is consistent with the evidence that Neolithic settlement sites overlie substantial beach deposits (see below). Archaeological sites at or below modern lake level provide information on intervals when the lake was lower than today (Olive, 1972; Gallay and Kaenel, 1981). Archaeological investigations of these sites have been carried out since 1823, and are sumarised by Gallay and Kaenel (1981). There are ca 50 sites (e.g. Dorigny-Les Pierettes, Vidy, Poudrière, Corsier-Port, Roseaux, l'Eglise, Grand Cité, Boiron). They appear to correspond to two distinct intervals of settlement: the Neolithic and the Late Bronze Age. The elevations of the sites suggest that the lake level was ca 369m (ie 3m lower than today) during the Neolithic and 366m (i.e. 6m lower than today) during the Late Bronze Age (Gallay and Kaenel, 1981). The stratigraphy of the submerged site of Corsier-Port (Burrus, 1980) appears to be typical. The archaeological layer overlies a unit of black biodetritic beach sand. The sand unit indicates a comparatively long interval when the lake was low. Plant macrofossils within the overlying archeological unit show signs of wave action, and indicate that this unit was deposited in shallow water. Gallay and Kaenel (1981) indicate that the actual living site was probably at an elevation of 369m a.s.l. and that the lake level fluctuated seasonally between 367.5- 368.5m. Radiocarbon dates from the archaeological unit indicate it was deposited ca 5200 yr B.P. The overlying unit consists of ca 50cm of lacustrine chalk, indicating an increase in lake level some time after 5000 B.P. An organic lense within this unit has been radiocarbon dated to 3202+52 B.C. (CRG-218). According to Burrus (1980) the granulometric characteristics of this layer suggest a water depth of more than 10m at the site. This would imply that the lake level was 378m a.s.l. However, Gallay and Kaenel (1981) suggest that this might be an over-estimate. In any case, it seems likely that this increase in water depth corresponds to the formation of the 3m terrace, which is dated to ca 4400 yr B.P. Regression of the lake during the late Neolithic and Bronze Age is marked by a second phase of occupation at Corsier-Port. Gallay and Kaenel (1981) argue that the absence of material dated to the middle Bronze age indicates that the lake was again high between ca 3500-3200 yr B.P. The final phase of occupation is dated to the late Bronze Age and corresponds to a decrease in lake level. During this interval, the average level of the lake is estimated at 367.5m (Gallay and Kaenel, 1981) or 366m (Magny and Olive, 1981). The lake rose again at the end of the Bronze Age. The remains of a Roman port, overlying the gravel deposits of the 3m terrace near Vidy, indicates that the average lake level ca 2000 yr B.P. was at 375.6m (Gallay and Kaenel, 1981). Magny and Olive (1981) suppose that the lake remained at this interval throughout Gallo-Roman times and then declined to the levels characteristic of the recent period. Attempts have been made to document the historical evidence of recent lake- level fluctuations (e.g. Forel, 1892-1904) but these are apparently not very reliable. In the status coding, low (1) is indicated by an estimated lake level at or below 370m; intermediate (2) by lake levels in the range 370-374m; high (3) by lake levels in the range 374 to 378m; very (4) by lake levels greater than 378m. Radiocarbon Dates B-3266 2590±60 arch. matl., yellow sands, 3m terrace, Vidy B-3265 2690±40 arch. matl., yellow sands, 3m terrace, Vidy B-3382 3000±80 peat, 0.1-0.3m, Collonge-Bellerive B-3267 3390±70 arch. matl., yellow sands, 3m terrace, Vidy B-3380 3750±80 arch. matl., 0.6m, Champ-Vully Gif- 3910±400 wood fragment, 395cm, core L66 GrN-5602 4330±40 bed 2, lacustrine sands/gravels, 3m terrace, Vidy B-3230 4600±80 peat, core (Reynaud) B-3369 5090±80 archaeological layer, Corsier-Port LU-1697 5090±65 carbonaceous shore-peat, archaeological layer, Corsier-Port LU-1696 5140±120 carbonaceous shore-peat, archaeological layer, Corsier-Port CRG-218 5152±52 organic matl. overlying arch layer, Corsier-Port B-3371 5310±90 arch. matl., 1m, Abri CRG-283 7770±400 arch matl. from Mesolithic shelter, Vionnez Ly-3300 10520±140 wood from peat bed, 381m, from 10m terrace CRG-215 11000±80 wood, Buchillon (10m) terrace B-752 12100±250 bed 3, pine trunk, 3m terrace, Vidy B-753 12400±200 bed 4, birch trunk, 3m terrace, Vidy B-751 12750±200 bed 6, organics, 3m terrace, Vidy Ly-2815 13090±160 30m terrace CRG-606 13210±180 plant remains in sandy silts, 30m terrace References Chaix, L., 1981. Le contenu paléontologique des terrasses du Léman et sa signification. Archives suisses d'anthropologie générale, Genève 45: 123-128. Forel, F.A., 1892-1904. Le Léman. Monographie limnologique. (3 vol.). Lausanne, F. Rouge (réédité par Slatkine, Genève, 1969). Gabus, J.-H., Lemdal, G. and Weidmann, M., 1987. Sur l'âge des terrasses lémaniques au SW de Lausanne. Bulletin de la Société vaudoise des Sciences naturelles 78: 419-429. Gaillard, M.-J., 1985. Late-glacial and Holocene environments of some ancient lakes in the western Swiss plateau. Dissertationes Botanicae 87: 273-336. Gaillard, M.-J., Reynaud, B., Weber, B. and Wegmüller, S., 1981. Les variations tardiglaciaires et postglaciaires du niveau du lac Léman: apport des données palynologiques Aperçu bibliographique. Archives suisses d'anthropologie générale, Genève 45: 117-121. Gallay, A. and Corboud, P., 1979. Les stations préhistoriques littorales du Léman. Où en sont nos connaissances? Archéologie Suisse 2:44-49. Gallay, A. and Kaenel, G., 1981. Repères archéologiques pour une histoire des terrasses du Léman. Archives suisses d'anthropologie générale, Genève 45: 129-157. Gallay, A, Corboud, P. and Chaix, L., 1980. Chronique archéologique. Annuaire de la Société Suisse de Préhistoire et d'Archéologie 63: 215-257. Håkansson, S., 1980. University of Lund radiocarbon dates XIII. Radiocarbon 22: 1045-1063. Magny, M. and Olive, P., 1981. Origine climatique des variations du niveau du lac Léman au cours de l'Holocène La crise de 1700 à 700 ans BC. Archives suisses d'anthropologie générale, Genève 45: 159-169. Olive, P., 1972. La région du lac Léman depuis 15000 ans: données paléoclimatiques et préhistoriques. Revue de Géographie physique et Géologie dynamique XIV: 253-264. Peese, S., 1994. Personal communication. Letter (December 27, 1994) Serruya, C., 1969. Les dépôts du Lac Léman en relation avec l'évolution du bassin sédimentaire et les caractères du milieu lacustre. Archives des Sciences 22: 125-254. Villaret, P. and Burri, M., 1965. Les découvertes palynologiques de Vidy et leur signification pour l'historire du Lac Léman. Bulletin de la Société vaudoise des Sciences naturelles 69: 1-19. Coding 14000-10500 yr B.P. very high (4) ca 382m 10500- 8500 yr B.P. high (3) below 376m 8500- 7700 yr B.P. low (1) 369m 7700- 5200 yr B.P. intermediate (2) below 372m ca 5200 yr B.P. low (1) 369m 5200-4200 yr B.P. high (3) 375m (+3m terrace) 4200-3500 yr B.P. intermediate (2) ca 370m 3500-3200 yr B.P. high (3) ca 375m 3200-2700 yr B.P. low (1) ca 366-368m 2700-1200 yr B.P. high (3) ca 375.5m 1200- 0 yr B.P. intermediate (2) 372+1.3m Preliminary coding: September 1988; Final coding: December 1988 Coded by: SPH Lobsigensee, Switzerland Lobsigensee (47 02'N, 7 18'E, 514.4m above sea level) is located 15km northwest of Berne on the Frienisberg- plateau. The lake is small (2 ha) with a maximum depth of 2.7m. The catchment area is ca 100 ha. The lake is fed directly by seepage. There is an intermittant outflow to the northeast (Ammann, 1989). The lake is bounded by an old littoral terrace on the north-northwest side, and has a rather steep shore in the south-southeast (Ammann, 1989). There is a well-developed macrophyte fringe with a regular zonation from riparian forest (Alnus glutinosa) to Phragmites, to floating-leaved aquatics (Nuphar and Nymphaea), and to submerged aquatics (Potamogeton) in the centre. The bedrock consists of sequences of freshwater and marine sedimentary rocks, particularly sandstone and limestone, overlain by moraine. The lake basin was formed as a kettle hole during the last deglaciation (Ammann, 1989). The lake was artificially lowered by 98cm to its present level in 1944. Twenty four cores (including eight paired cores) from two transects (LQ: SSE-NNW and LL: SSW-NNE) across the basin provide information on the stratigraphy (Ammann, 1989). The LQ transect consists of four deepwater cores (90, 120, 82 and 68) and eleven marginal cores (20, 60, 70, 80, 150, 150c, 150d, 150e, 170, 170c and 170d). Core 90 is 9.40m long. Core 120 is 9m, core 82 is 12.8m and core 68 is 10m. Cores 20, 60, 70, 80, 150, 150c, 150d and 150e were taken from NNW margin of the lake and core 170, 170c and 170d were from the opposite side. The Arabic numbers show the distances in meter between the cores and the riparian forest marking the shoreline to the north-northwest. The lengths of cores 20, 60, 70, 80, 150, 150d, 150e, 170, 170c and 170d are 13.90m, 7m, 10.9m, 6.7m, 7m, 1.5m, 1.5m, 9.80m, 9.60m and 9.10m espectively. The LL transect crosses LQ at core 90 and has three additional cores (160, 11 and 2). Core 160 (12.9m) was taken from the littoral zone and core 2 (9m) was taken at the shoreline. Cores 150, 70, 20, 68, 82, 120, 170 and 160 have twin cores. All cores have been used for pollen analyses (Ammann, 1989). Plant macrofossils have been analysed from cores 2, 150, 150d and 150e (Tobolski, 1985; Ammann, et al., 1983; Ammann and Tobolski, 1983). Cladocera from core 120 (Hofmann, 1985) and molluscs from cores 20, 70, 150d and 150e (Ammann et al., 1983; Ammann, 1989) have been studied. Pigment stratigraphic analysiswas carried out on cores 68 and 160 (Züllig, 1986). The different cores are correlated by terrestrial pollen assemblages. Ammann (1989) reconstructed the history of lake level changes at Lobsigensee, based on lithological evidence, occurrence of molluscs, and transitions between limnogenic sediment and peat. Here, changes in water depth are reconstructed from changes in lithology, aquatic pollen and macrofossils, Cladocera, molluscs and pigment stratigraphy (Ammann, 1989; Ammann and Tobolski, 1983; Ammann, et al., 1983; Hofmann, 1985; Tobolski, 1985; Züllig, 1986). Our reconstructions broadly follow those in Ammann (1989). The late glacial and Holocene chronology is provided by 19 radiocarbon dates on terrestrial plant macrofossils from core 160 (160a and 160b) and 16 radiocarbon dates on terrestrial plant macrofossils from cores 170d and 170c. Three dates on terrestrial macrofossils at the level of the Laacher-See tephra are in good agreement with dates obtained for this tephra elsewhere (Ammann, 1989; van den Bogaard and Schmincke, 1985). Radiocarbon dates on gyttja (20 dates) and carbonate (14 dates) from cores 160, 170 and 90 are between 300-1000 years older than expected during the late Pleistocene, and 500-700 years too old during the Holocene because of hard-water effects (Ammann, 1989; Oeschger, et al., 1985). Pollen-based dating is therefore used after 8000 yr B.P. (Ammann, 1989). The basal unit, found in all cores, is clay. Aquatic pollen, such as Ranunculus and Potamogeton, is present in the littoral zone but very rare in the central area. Aquatic macrofossils (Chara, Myriophyllum and Polygonum) are abundant in the shallower littoral (core 150d) zone. Only Chara occurs in the deeper littoral (core 2) zone. The Cladocera content is low. On the basis of sediment profiles, Ammann (1989) suggested that the lake was at least 10 ha in area and 17m deep during the early Late-Glacial. There are two radiocarbon dates on terrestrial plant macrofossils from this unit: 12630±170 yr B.P. (core 160a at a depth of 10.60-10.90m) and 13360±280 (core 170d at a depth of 8.30-8.50m). The overlying unit is fine detritus gyttja in the centre, calcareous gyttja in the deep-littoral and lake marl in the shallow-littoral zone. The increase in organic content indicates decreased water depth. The occurrence of Potamogeton and Ranunculus in the profundal zone is consistent with shallowing. The presence of Phragmites and the decrease of Chara macrofossils in littoral core 150 are in agreement with decreased water depth. In the deeper littoral (core 2), Chara is predominant in the aquatic macrofossils assemblages. Pelagic Cladocera (Bosmina logispina and Bosmina longirostris) are abundant, 1985), suggesting the water was relatively deep. Laminations are present both in centre and in littoral zone, indicating enlargement of littoral conditions (Ammann, 1989). Thirty terrestrial plant macrofossil samples from this unit have been radiocarbon dated. A sample from the base (7.99-8.015m in core 170d) yields an age of 12360±320 yr B.P. and one from the top (7.52-7.54m in 170d) is dated to 9980±120 yr B.P.. The overlying sediments are fine detritus gyttja in the centre, calcareous gyttja in the deeper littoral zone, lake marl in the marginal area and peat in the most littoral core 150, suggesting shallowing. Pigment stratigraphy indicates increased eutrophication (Züllig, 1986), consistent with shallowing. The occurrence of molluscs in littoral cores (70 and 20) is in agreement with shallower water (Ammann, 1989). Menyanthes, a shallow water aquatic, is present in the littoral zone (cores 70, 60 and 20). Chara decreased considerably, and Typha and Phragmites increased in the macrofossil assemblages from the deeper littoral. Littoral Cladocera, such as Chydorus piger, Alonella excisa, Alonella nana, Acroperus harpae and Alona affinis, are predominant also consistent with shallowing. There are seven radiocarbon dates on terrestrial plant macrofossils from this unit, indicating that this phase occurred between 9950 and 8000 yr B.P. The overlying unit is calcareous gyttja and calcareous, fine detritus gyttja in the centre, and lake marl in the littoral zone. The highest marginal core (150) does not contain limnic deposits, suggesting continued shallowing. The presence of Menyanthes, Nuphar, Typha and Nymphaea in the littoral pollen assemblage is in agreement with decreased water depth. The macrofossil assemblages from the littoral zone (core 2) are characterized by the occurrence of Nymphaea, Phragmites and the clear decrease of Chara. In the Cladocera assemblages, littoral species (Acroperus harpae and Alona affinis) are abundant. Molluscs are present in core 20 at a depth 5m below modern lake level (515.38m). The occurrence of coarse layers of plant macrofossils in core 170, is consistent with decreased depth. The overlying sediments are calcareous, fine detritus gyttja in the centre and peat in the littoral zone. Peat deposition transgressed to lower altitudes through time, suggesting decreased water depth after ca 6000 yr B.P. The time-transgressive onset of peat deposition is generated partly by climatically induced decrease of water depth and partly by infilling processes (Ammann, 1989). The absence of limnic deposits in the littoral core 80 is consistent with decreased water depth. Pigment stratigrphy indicates that eutrophication increased (Züllig, 1986), in agreement with decreased water depth. The abundance of aquatic pollen in the littoral zone, represented by Sparganium, Nymphaea, Nuphar and Potamogeton is also consistent with shallower water. In the macrofossil assemblages from the littoral zone (core 2), Ceratophyllum, Nymphaea and Phragmites are present. Littoral Cladocera (Acroperus, Alona and Alonella) are abundant, suggesting the water was moderately shallow. The local pollen chronology indicates this unit was deposited between ca 6000-2000 yr B.P. The overlying sediments are calcareous gyttja in the centre and lake marl in the littoral zone. Limnic sediments are absent from the former littoral cores 70, 60 and 20, indicating decreased depth after ca 2000 yr B.P. The increased abundance of Nymphaea and Cyperaceae is consistent with shallowing. Littoral Cladocera, such as Alona and Graptoeberis, are predominant. This is also consistent with shallow conditions. The overlying sediments are fine detritus gyttja, suggesting increased water depth after ca 1550 yr B.P. The decrease of Cyperaceae, and the increase of Sparganium, Ceratophyllum and Potamogeton, is consistent with deeper water. Macrofossils of Ceratophyllum, Potamogeton, Nymphaea and Chara are abundant in the littoral zone, also indicating increased water depth. The increased abundance of pelagic Cladocera (Bosmina longirostris) indicates deeper water. Local terrestrial pollen chronosequence suggests this unit was deposited between ca 1550-800 yr B.P. (Ammann, 1989). The uppermost unit is calcareous gyttja with clay, indicating decreased water depth after ca 800 yr B.P. The abundance of Cyperaceae, Nymphaea, Nuphar and Typha is consistent with shallowing. In the status coding, very low (1) is indicated by calcareous gyttja and abundance of Nymphaea, Typha and Cyperaceae; low (2) by calcareous, fine detritus gyttja, transgression of peat in the littoral zone and abundance of littoral Cladocera; intermediate (3) by presence of calcareous gyttja over a larger area, and decrease of Chara in littoral zone; moderately high (4) by fine detritus gyttja in the centre, calcareous gyttja in the deeper littoral zone and peat in the marginal area or calcareous gyttja with clay, the occurrence of molluscs in littoral cores (70 and 20); high (5) by fine detritus gyttja in the centre, calcareous gyttja in the littoral zone and the abundance of Bosmina; very high (6) by clay deposits. References Ammann, B., 1989. Late-Quaternary palynology at Lobsigensee. Dissertations Botanicæ 137, 157pp.+ 81 diagr. Ammann, B., 1986. Litho- and palynostratigraphy at Lobsigensee: Evidences for trophic changes during the Holocene. Hydrobiologia 143: 301-307. Ammann, B., Chaix, L., Eicher, U., Elias, S. A., Gaillard, M.-J., Hofmann, W., Siegenthaler, U., Tobolski, K. and Wilkinson, B., 1983. Vegetation, insects, molluscs and stable isotopes from late würm deposits at Lobsigensee (Swiss Plateau). Studies in the late Quaternary of Lobsigensee 7. Revue de Paléobiologie 2(2): 221-227. Ammann, B. and Tobolski, K., 1983. Vegetational development during the late-würm at Lobsigensee (Swiss Plateau). Studies in the late Quaternary of Lobsigensee 1. Revue de Paléobiologie 2(2): 163-180. Firbas, F., 1949. Spät- und nacheiszeitliche Waldgeschichte Mitteleuropas nördlich der Alpen. Erste Band: Allgemeine Waldgeschichte. Jena. 480pp. Hofmann, W., 1985. Developmental history of Lobsigensee: subfossil Cladocera (Crustacea). Dissertations Botanicæ 87: 150-153. Oeschger, H., Andrée, M., Moell, M., Riesen, T., Siegenthaler, U., Ammann, B., Tobolski, K., Bonani, B., Hofmann, H.-J., Morenzoni, E., Nessi, M., Suter, M. and Wölfli, W., 1985. Radiocarbon chronology at Lobsigensee. Comparison of materials and methods. Dissertations Botanicæ 87: 135-139. Tobolski, K., 1985. Plant macrofossils from Lobsigensee. Dissertations Botanicæ 87: 140-143. van den Bogaard, P. and Schmicke, H.-U., 1985. Laacher See Tephra: A widespread isochronous late Quaternary tephra layer in central and northern Europe. Geological Society of America Bulletin 96: 1554-1571. Züllig, H., 1986. Carotenoids from plankton and photosynthetic bacteria in sediments as indicators of trophic changes in Lake Lobsigen during the last 14 000 years. Hydrobiologia 143: 315-319. Radiocarbon dates B-4314 1690±80 2.22-2.25m, gyttja, core 90, ATO B-4315 2030±60 2.43-2.46m, gyttja, core 90, ATO B-4316 2300±50 2.92-2.95m, gyttja, core 90, ATO B-4317 2680±50 3.66-3.70m, gyttja, core 90, ATO B-4318 3230±50 4.00-4.03m, gyttja, core 90, ATO B-4319 4140±60 4.60-4.63m, gyttja, core 90, ATO B-4320 4950±70 5.00-5.03m, gyttja, core 90, ATO B-4321 5350±60 5.23-5.26m, gyttja, core 90, ATO B-4322 6300±60 5.70-5.74m, gyttja, core 90, ATO B-4044 7550±40 8.03-8.05m, gyttja, core 90, ATO ck-77 8000±200 7.38-7.40m, terrest. plant macrofossils, 170d ck-76 8370±230 7.40-7.42m, terrest. plant macrofossils, 170d B-4043 8430±40 7.97-7.99m, gyttja, core 90, ATY c-1087 9270±170 7.42-7.44m, terrest. plant macrofossils, 170d B-4323 9500±90 7.30-7.32m, gyttja, core 90 c-609 9550±130 7.54-7.56m, terrest. plant macrofossils, 170d, ATY ck-37 9620±130 7.60-7.62m, terrest. plant macrofossils, 170c, ATY B-4034 9640±190 0.23-0.26m, carbonate, 150e, not used c-611 9770±120 7.46-7.48m, terrest. plant macrofossils, 170d c-612 9910±120 7.44-7.46m, terrest. plant macrofossils, 170d c-608 9980±120 7.52-7.54m, terrest. plant macrofossils, 170d c-609 9930±120 7.50-7.52m, terrest. plant macrofossils, 170d c-610 10060±120 7.48-7.50m, terrest. plant macrofossils, 170d c-604 10150±130 7.56-7.58m, terrest. plant macrofossils, 170d c-597 10300±140 7.64-7.66m, terrest. plant macrofossils, 170c c-603 10330±130 7.58-7.60m, terrest. plant macrofossils, 170c c-599 10350±120 7.68-7.70m, terrest. plant macrofossils, 170d c-598 10600±140 7.66-7.68m, terrest. plant macrofossils, 170c B-4037 10670±70 7.43-7.45m, gyttja, core 90, ATO c-755 10680±140 9.075-9.10m, terrest. plant macrofossils, 160a c-754 10680±150 9.05-9.075m, terrest. plant macrofossils, 160a B-4038 10790±70 7.47-7.49m, gyttja, core 90, ATO c-497 10860±130 9.01-9.03m, terrest. plant macrofossils, 160a c-613 10900±130 7.75m, terrest. plant macrofossils, 170d c-496 10900±140 8.87-8.89m, terrest. plant macrofossils, 160a B-4032 10910±120 0-0.02m, carbonate, 150e, ATO c-756 10970±140 9.125-9.15m, terrest. plant macrofossils, 160a c-503 11060±140 8.98-9.00m, terrest. plant macrofossils, 170c c-717 11080±170 9.10-9.125m, terrest. plant macrofossils, 160a B-3980 11090±120 0.02-0.05m, carbonate, 150e, ATO c-760 11110±160 9.03-9.05m, terrest. plant macrofossils, 160a c-757 11220±150 9.225-9.25m, terrest. plant macrofossils, 160a c-723 11460±160 9.175-9.20m, terrest. plant macrofossils, 160a B-4039 11470±120 7.65-7.67m, gyttja, core 90, ATO c-719 11510±150 9.15-9.715m, terrest. plant macrofossils, 160a c-722 11510±150 9.20-9.225m, terrest. plant macrofossils, 160a c-758 11530±160 9.275-9.30m, terrest. plant macrofossils, 160a c-718 11590±160 9.25-9.275m, terrest. plant macrofossils, 160a ck-38 11640±160 7.62-7.64m, terrest. plant macrofossils, 170c B-4047 11750±100 0.29-0.32m, carbonate, 150e, ATO c-499 11920±140 9.30-9.325m, terrest. plant macrofossils, 160a B-4040 12170±60 7.81-7.85m, gyttja, core 90, ATO B-4041 12180±60 7.85-7.87m, gyttja, core 90, ATO B-4084 12240±170 0.35-0.38m, carbonate (tephra), 150e, ATO B-4036 12270±120 0.55-0.58m, carbonate, 150e, ATO B-4049 12310±120 0.43-0.46m, carbonate, 150e, ATO B-4035 12320±130 0.52-0.55m, carbonate, 150e, ATO ck-75 12360±320 7.99-8.015m, terrest. plant macrofossils, 170d c-501 12360±140 9.395-9.435m, terrest. plant macrofossils, 160a c-533 12410±150 9.365-9.395m, terrest. plant macrofossils, 160a c-493 12420±150 9.325-9.365m, terrest. plant macrofossils, 160a B-4046 12460±160 8.07-8.085m, gyttja, core 90, ATO c-614 12470±140 9.01-9.05m, terrest. plant macrofossils, 170c B-3982 12480±120 0.76-0.80m, carbonate, 150e, ATO B-3981 12500±140 0.58-0.61m, carbonate, core 90, ATO B-3983 12520±140 0.80-0.83m, carbonate, 150e, ATO c-759 12630±170 10.60-10.90m, terrest. plant macrofossils, 160a B-4042 12700±80 7.95-7.97m, gyttja, core 90, ATO B-4050 12820±130 0.67-0.70m, gyttja, 150e, ATO B-3984 12880±140 0.83-0.87m, carbonate, 150e, ATO B-4045 13250±100 8.05-8.07m, gyttja, core 90, ATO c-1088 13360±280 8.30-8.50m, terrest. plant macrofossils, 170d B-3985 13800±150 0.87-0.91m, carbonate, 150e, ATO Coding 14000-12400 yr B.P. very high (6) 12400-9950 yr B.P. high (5) 9950-8000 yr B.P. moderately high (4) 8000-6000 yr B.P. intermediate (3) 6000-2000 yr B.P. low (2) 2000-1550 yr B.P. very low (1) 1550-800 yr B.P. high (5) 800-0 yr B.P. moderately high (4) Preliminary coding: 20th March 1994; Final coding: 12th April 1994. Coded by: XY and SPH Nussbaumerseen, Switzerland Nussbaumerseen (47.65 N, 8.45 E, 434m above sea level) consists of three sub-basins, with a total surface area of 24.6 ha. The maximum depth is 8.2m. The lake is fed by several small streams and overflows into the Hüttwilersee. The lake level was artificially lowered by ca 2m in 1945. The stratigraphy of the bottom deposits was reconstructed from ca 170 borings. Detailed pollen and sedimentological analyses were carried out on 10 cores (Rösch, 1983, 1985). Macrofossil, oxygen isotope and geochemical analyses were carried out on some cores. Rösch (1983, 1985) has reconstructed a continuous record of changes in lake-level since 16,000 yr B.P. on the basis of changes in lithology, sedimentation rates and the position of the sediment limit, the occurrence of sedimentary hiatuses, and changes in aquatic plant assemblages. The chronology is based on 16 radiocarbon dates. The basin was originally occupied by a single glacier-dammed lake. The deglaciation of the Thur valley, south of the lake, led to a drop in water level of ca 5m and the drainage of this lake. The three lakes of Nussbaumersee originated at this time (ca 14,000 yr B.P.). There is some indication of uplift after the area was deglaciated, but according to Rösch (1983) this did not affect the level of the Nussbaumerseen significantly. The water level was high (436m) initially but started to fall shortly after ca 12,000 yr B.P., reaching a level of 433m between ca 10,500 and 8800 yr B.P. The water level increased slightly after this, peaking at 434m ca 8000 yr B.P. and then falling again. The interval between ca 7600 and 4000 yr B.P. is marked by several lake- level fluctuations but, in general the lake was much lower than at any other time in its history. After 4000 yr B.P., the lake rose progressively, reaching maximum depth (436m) just before 1000 yr B.P. It persisted at this level until it was artificially regulated in 1945. In the status coding, low (1) is indicated by a lake level below 433m; intermediate (2) by a lake level between 433-435m; high (3) by a lake level of 435m or greater. The modern low lake level (434m a.s.l.) is the result of artificial lowering in 1945, and so modern is coded as the pre-1945 level. Reference Rösch, M., 1983. Geschichte der Nussbaumer Seen (Kanton Thurgau) und ihrer Umgebung seit dem Ausgang der letzten Eiszeit aufgrund quartärbotanischer, stratigraphischer und sedimntologischer Untersuchungen. Mitteilungen der Thurgauischen Naturforchenden Gesellschaft 45: 1-103. Rösch, M., 1985. Nussbaumer Seen - Spät- und postglaziale Umweltsveränderungen einer Seengruppe im östlichen schweizer Mittelland. Dissertationes Botanicae 87: 337-379. Radiocarbon Dates B-3889 modern clay gyttja, Nu-2, 424-430cm, contam. B-3898 260±130 gyttja, Nu-4, 460-470cm B-3892 4070±70 peat, Nu-4, 182-191cm B-3894 4750±70 peat, Nu-4, 261-271cm B-3895 5230±60 peat, Nu-4, 271-281cm B-3896 6190±80 peat, Nu-4, 317-325cm B-3897 7220±90 peat, Nu-4, 389-398cm B-3899 9820±120 gyttja, Nu-4, 610-619cm B-3901 10210±90 gyttja, Nu-4, 680-689cm B-3902 10960±90 gyttja, Nu-4, 715-724cm, Laacher tephra B-3887 11170±150 peaty gyttja, Nu-2, 414-419cm B-3903 11630±100 gyttja, Nu-4, 740-749cm B-3888 12720±160 peaty gyttja, Nu-2, 419-424cm B-3905 13100±90 calcareous gyttja, Nu-4, 757-767cm B-3893 no date peat, Nu-4, 225-234cm, too little matl. B-3900 no date gyttja, Nu-4, 640-649cm, too little matl. Coding 13800-11100 yr B.P. high (3) 11100-7600 yr B.P. intermediate (2) 7600-4000 yr B.P. low (1) 4000-2200 yr B.P. intermediate (2) 2200-0 yr B.P. high (3) Preliminary coding: February 1987; Final coding: November 1987 Coded by: SPH Rotsee, Switzerland Lake Rotsee (47.15 N, 8.31 E, 419m above sea level) is a meromictic lake in an ancient river valley. The lake is 2.5 km long, but generally less than 250-300m wide, with a surface area of 46ha (Lotter, 1988b). The lake has a maximum depth of 16m and a mean depth of 9m. There is a small inflow at the western end of the lake, and an outflow from the eastern end. The catchment area is 460ha. The lake lies at the boundary of the central Swiss Plateau and the calcareous Prealps (Lotter, 1987). Lithological, pollen, plant macrofossil, diatom, oxygen isotope and geochemical studies have been carried out at this site (Lotter, 1988a, 1988b; Ammann and Lotter, 1989; Lotter and Zbinden, 1989). Changes in water depth are reconstructed from changes in lithology and diatom assemblages, and broadly follow those reconstructed by Lotter (1988b). There are 14 conventional radiocarbon dates and at least 61 AMS dates on terrestrial macrofossils (Lotter, 1988b; Ammann and Lotter, 1989). Unfortunately, all of the AMS dates are on late glacial sediments and there appears to be substantial hard-water and contamination problems with the conventional dates (Lotter, 1988b). The chronology after ca 9500 yr B.P. appears to be largely based on pollen correlation. The stratigraphy of the lake deposits has been reconstructed from a longitudinal SW-NE transect of 15 cores (Lotter, 1988b). Several cores (e.g. RL-300, RL-305, RL-270) from the overgrown area at the northeast end of the lake contain the Laacher See tephra, indicating that they provide a record back to before ca 11,000 yr B.P. Core RL-240, a 11m-long taken in a water depth of 8m at the northeast end of the lake, provides a continuous record back to ca 9000 yr B.P. (Lotter, 1988b). The basal sediments are clays grading to clayey gyttja. The overlying sediments are calcareous gyttja or lake marl. The diatom assemblages in core Rl-240 are characterised by the overwhelming dominance of planktonics species and indicate that the water depth was greater than 9m (and thus greater than present) (Lotter, 1988b). The presence of the Laacher See tephra near the base of this unit indicates that deposition of this unit began some time before 11,000 yr B.P. There is a transition to carr-peat at ca 3-4m below modern lake level in cores at both ends of the lake (e.g. RL- 20, RL-270, RL-280, Rl-300, RL-305), indicating a decrease in water depth. In cores from the northeastern marginal zone of the lake (e.g. RL-240, RL-250), carr-peat appears to correspond to a transition from calcareous gyttja to fine detritus gyttja, a lithological change consistent with shallowing. According to the diatom assemblages in core RL-240, there was a gradual and oscillatory increase in Fragilaria spp., across the transition from calcareous gyttja to fine detritus gyttja. Periphytic species and Fragilaria spp. were overwhelmingly dominant during most of the fine detritus gyttja unit, consistent with shallower water. Lotter (1988b) indicates that the water depth at the coring site was less than 5m during this interval. Palynological dating indicates that the transition to carr-peat took place at the end of the Older Atlantic (AT1), ca 6000 yr B.P. (Lotter, 1988b). In the cores from the overgrown area at the northeastern end of the lake, the carr-peat grades upward into sedge peats. However, a transition from fine detritus gyttja to calcareous gyttja in marginal cores at the northeastern end of the lake indicates an increase in water depth. This transition corresponds to a decline in the abundance of perphytic species and of Fragilaria spp., consistent with increasing water depth. In core RL-20, at the southwestern end of the lake, there is a transition from carr-peat to fine detritus gyttja and thence into calcareous gyttja, consistent with a progressive increase in depth. In core RL-20, the increase has been dated to during the Older Subatlantic (SA1), ca 2000 yr B.P. (Lotter, 1988b). Lotter (1988b) suggests that the increase in water depth ca 2000 yr B.P., coinciding with Roman times, may be a reflection of human impacts in the catchment. There is no independent evidence of this. In the status coding, low (1) is indicated by carr-peat deposition in cores from the overgrown area, and by fine detritus gyttja deposition with overwhelming dominance of periphytic and epiphytic diatoms in core RL-240; intermediate (2) by intermediate abundances of periphytic and epiphytic diatoms, and reconstructed water depths in the range 5-9m, similar to present; high (3) by calcareous gyttja deposition, the overwhelming dominance of planktonic diatoms in core RL-240 and reconstructed water depths greater than today. Radiocarbon Dates St 10060 1895±75 gyttja, 1.30-1.40m, RL-240 B-4882 2360±40 gyttja, 1.10-1.22m, RL-250 B-4883 2280±60 gyttja, 1.50-1.60m, RL-250 B-4884 2230±60 gyttja, 1.85-1.95m, RL-250 St 10059 3900±90 gyttja, 3.10-3.20m, RL-240 B-4885 4370±60 gyttja, 2.30-2.40m, RL-250 B-4886 4820±60 gyttja, 2.80-2.29m, RL-250 B-4881 5140±40 bruchtorf, 4.18-4.23m, RL-305 B-4887 5940±60 gyttja, 3.35-3.45m, RL-250 St 10058 7140±100 gyttja, 5.85-5.95m, RL-240 B-4888 7420±100 gyttja, 4.05-4.15m, RL-250 B-4889 8750±50 gyttja, 4.49-4.60m, RL-250 C-728 9360±130 wood, 6.63-6.68m, RL-300, AMS date C-725 9380±130 wood, 6.33-6.38m, RL-300, AMS date C-724 9450±140 wood, 6.23-6.28m, RL-300, AMS date C-847 9450±140 wood, 9.08-9.12m, RL-305, AMS date C-846 9510±140 wood,9.04-9.08m, RL-305, AMS date (9505±140)* C-852 9630±150 wood, 9.16-9.20m, RL-305, AMS date C-848 9760±160 wood, 9.12-9.16m, RL-305, AMS date C-726 9770±130 wood, 6.43-6.48m, RL-300, AMS date C-727 9780±140 wood, 6.53-6.58m, RL-300, AMS date C-746 9840±140 wood, 6.83-6.88m, RL-300, AMS date B-4890 9800±120 braumoos, 7.13-7.17m, RL-250 C-869 9870±150 wood, 9.36-9.40m, RL-305, AMS date B-4891 10740±130 gyttja, 12.60-12.64m, RL-250 C-730 10000±130 wood, 7.33-7.38m, RL-300, AMS date C-853 10010±160 wood, 9.20-9.24m, RL-305, AMS date C-854 10010±150 wood, 9.24-9.28m, RL-305, AMS date C-864 10010±150 wood, 9.32-9.36m, RL-305, AMS date C-874 10010±150 wood, 9.40-9.44m, RL-305, AMS date (10015±150)* C-734 10020±120 wood,6.73-6.78m, RL-300, AMS date C-859 10060±130 wood, 9.28-9.32m, RL-305, AMS date C-731 10120±140 wood, 7.03-7.08m, RL-300, AMS date C-889 10130±150 wood, 9.44-9.48m, RL-305, AMS date C-904 10310±160 wood, 9.52-9.56m, RL-305, AMS date C-905 10440±160 wood, 9.56-9.60m, RL-305, AMS date C-901 10450±160 wood, 9.60-9.64m, RL-305, AMS date C-909 10460±160 wood, 9.48-9.52m, RL-305, AMS date C-914 10640±160 wood, 9.68-9.72m, RL-305, AMS date, LST C-968 10730±150 wood, 7.53-7.58m, RL-300, AMS date C-748 10920±170 wood, 7.43-7.48m, RL-300, AMS date C-910 11070±170 wood, 9.64-9.68m, RL-305, AMS date C-978 11230±180 wood, 9.76-9.80m, RL-305, AMS date C-779 11260±140 wood, 7.83-7.88m, RL-300, AMS date, LST C-780 11270±140 wood, 7.93-7.98m, RL-300, AMS date C-915 11370±180 wood, 9.72-9.76m, RL-305, AMS date C-784 11440±140 wood, 8.05-8.08m, RL-300, AMS date C-785 11460±140 wood, 8.13-8.18m, RL-300, AMS date C-919 11670±170 wood, 9.76-9.80m, RL-305, AMS date C-920 11740±180 wood, 9.80-9.84m, RL-305, AMS date C-783 11800±140 wood, 8.43-8.48m, RL-300, AMS date C-934 11810±200 wood, 9.84-9.88m, RL-305, AMS date C-782 11870±150 wood, 8.33-8.38m, RL-300, AMS date C-979 11880±150 wood, 8.53-8.58m, RL-300, AMS date C-781 11970±150 wood, 8.23-8.28m, RL-300, AMS date C-939 12060±220 wood, 9.88-9.92m, RL-305, AMS date C-804 12280±190 wood, 10.20-10.24m, RL-305, AMS date C-935 12410±220 wood, 9.92-9.96m, RL-305, AMS date C-795 12570±180 wood, 10.12-10.16m, RL-305, AMS date C-791 12580±170 wood, 8.63-8.68m, RL-300, AMS date C-794 12600±170 wood, 10.08-10.12m, RL-305, AMS date C-793 12730±190 wood, 10.04-10.08m, RL-305, AMS date C-796 12800±190 wood, 10.16-10.20m, RL-305, AMS date C-809 12800±190 wood, 10.24-10.28m, RL-305, AMS date C-815 12970±200 wood, 10.40-10.44m, RL-305, AMS date C-814 13290±200 wood, 10.36-10.40m, RL-305, AMS date C-805 13350±210 wood, 10.28-10.32m, RL-305, AMS date C-810 13540±210 wood, 10.32-10.36m, RL-305, AMS date C-818 13600±220 wood, 10.44-10.48m, RL-305, AMS date C-830 13820±210 wood, 10.48-10.52m, RL-305, AMS date C-838 13990±220 wood, 10.64-10.68m, RL-305, AMS date C-831 14000±210 wood, 10.52-10.56m, RL-305, AMS date C-836 14170±230 wood, 10.84-11.00m, RL-305, AMS date C-837 14240±220 wood, 10.60-10.64m, RL-305, AMS date C-823 14570±240wood, 10.56-10.60m, RL-305, AMS date * There are discrepancies of dates between two sources (Lotter, 1988 and Ammann and Lotter, 1989). The dates used here are following those from Ammann and Lotter (1989). References Ammann, B. and Lotter, A.F., 1989. Late-Glacial radiocarbon- and palynostratigraphy on the Swiss Plateau. Boreas 18: 109-126. Lotter, A., 1987. Late-glacial vegetational succession and chronology at Lake Rotsee, Switzerland (Abstract). In: M.J. Gaillard (ed), Palaeohydrological changes in the temperate zone in the last 15000 years. Lundqua Report 27: 202-203. Lotter, A., 1988a. Past water-level fluctuations at Lake Rotsee (Switzerland), evidenced by diatom analysis. In: U. Miller and A. Robertsson (eds.), Proceedings of Nordic Diatomist Meeting, University Stockholm, Department of Quaternary Research (USDQR) Report 12: 47-55. Lotter, A.F., 1988b. Paläoökologische und paläolimnologische Studie des Rotsees bei Luzern. Pollen-, grossrest- , diatomeen- und sedimentananalytische Untersuchungen. Dissertationes Botanicæ 124: pp 187. Lotter, A.F. and Zbinden, H., 1989, Late-Glacial pollen analysis, oxygen-istope record, and radiocarbon stratigraphy from Rotsee (Lucerne), Central Swiss plateau. Eclogicae Geologicae Helvetiae 82: 191- 202. Coding 11000-6500 yr B.P. high (3) 7000-5000 yr B.P. intermediate (2) 6000-2000 yr B.P. low (1) 2000-0 yr B.P. intermediate (2) Preliminary coding: March 1988; Final coding: February 1990 Coded by: SPH a'Chnuic, UK Loch a'Chnuic (57 12'N, 3 35'W, 310m above sea level) occupies part of a basin in a col at the present southwestern margin of the Abernethy Forest (O'Sullivan, 1974). The lake area is ca 4.7ha. The Abernethy Forest lies in the upper-reaches of a small tributary of the River Spey. The remainder of the basin is infilled by Schwingmoor (floating mats with Sphagnum). The catchment bedrock is Moine granulites with small granite intrusions (Birks, 1970). During glacial periods ice flowed along the Spey valley, resulting in the deposition of morainic material and boulder clay. The overlying soils are acid with mor humus accumulation (Birks, 1970). The stratigraphy of the peat deposit at Loch a'Chnuic was reconstructed by F. Oldfield from a transect of 11 cores (2, 3, 4, 5, 6, 7, 8, 9, A, B, C). Samples for pollen analysis were taken from the longest core (core 9). Changes in water depth are reconstructed from changes in lithology and aquatic pollen assemblages, and from biostratigraphic evidence suggesting an hiatus in deposition. The chronology is provided by correlation with the radiocarbon-dated site of Loch Garten, which lies ca 8km to the northwest (O'Sullivan, 1974, 1975). The basal deposits in the deepest cores (5.30-5.50m in Core 9) are tough, compact blue-grey clays, devoid of pollen. These and the overlying sandy clays (5.00-5.30m in Core 9) are thought to be of Late Devensian age (O'Sullivan, 1974). The overlying unit in the deepest cores (4.85-5.00m in Core 9) marks the transition from clay to organic muds, and the onset of lacustrine sedimentation. The aquatic pollen assemblage is characterised by a decline in the abundance of Cyperaceae and Equisetum, and the appearance of a diverse aquatic flora including Littorella, Sparganium, Potamogeton, Nymphaea and Myriophyllum. The overlying unit (4.45-4.85m in Core 9) is detritus mud, consistent with moderate water depth. Oscillations in water depth are indicated by the occurrence of two thin bands of diatomite (at 4.42-4.45m and 4.28-4.32m in Core 9), separated by fine detritus mud. The terrestrial pollen assemblages show an extremely abrupt change at the LC3/LC4 boundary, corresponding to the transition between the uppermost diatomite band and the overlying medium detrital mud unit. O'Sullivan (1975 and personal communication, 1984) thinks this abrupt change indicates an hiatus in sedimentation. Comparison with the terrestrial pollen assemblages at Loch Garten and Loch Pityoulish suggests that the hiatus occurred between ca 6700 and 8000 yr B.P. The overlying unit in the deeper cores (3.00-4.28m) is a medium detritus mud, indicating a return to limnic conditions. The aquatic pollen assemblage is characterised by moderate levels of Potamogeton and Nymphaea and the occurrence of Isoetes and Myriophyllum. A progressive decrease in water depth after ca 4000 yr B.P. is indicated by a gradual transition from detritus mud into drift peat and then into peat. This decrease is reflected in the aquatic assemblages, where Cyperaceae, Sphagnum, Isoetes and Menyanthes become increasingly abundant. These changes may reflect hydroseral development in the basin. In the status coding, low (0) is indicated by an hiatus; intermediate (1) by detrital mud; high (2) by diatomite. Note that the dating of the high phase at the beginning of the record is poorly constrained. Peat deposition after 4000 yr B.P. is considered as reflecting hydroseral development in the basin, and this interval is not coded. References Birks, H.H., 1970. Studies in the vegetational history of Scotland. Journal of Ecology 58: 827-846. O'Sullivan, P.E., 1974. Two Flandrian pollen diagrams from the east-central highlands of Scotland. Pollen et Spores 16: 33-57. O'Sullivan, P.E., 1975. Early and Middle-Flandrian pollen zonation in the Eastern Highlands of Scotland. Boreas 4: 197-207. O'Sullivan, P.E., 1984. Personal communication. Radiocarbon dates from Loch Garten UB-850 3635+205 0.80-0.90m UB-851 5860+100 2.50-2.60m UB-852 7585+335 2.72-2.82m Coding pre-8000 yr B.P. high (2) 8000-6700 yr B.P. hiatus (0) 6700-4000 yr B.P. intermediate (1) 4000-0 yr B.P. infilling, not coded Preliminary coding: 2nd July 1992; Final coding: 14th July 1993 Coded by SPH and GY a'Mhuilinn, UK Loch a'Mhuilinn (55 42'N, 5 16'W, 25m above sea level) is a small lake (4.5 ha) in the lower reaches of Glen Chalmadale, less than 1km from the north coast of Arran (Boyd and Dickson, 1987). The catchment area is about 110ha. The basin is bounded to the south by steep hills rising to 250m above sea level, and to the north by a ridge. This ridge may be a morainic feature, or more likely a protalus rampart formed ca 10,500 yr B.P. during the Loch Lomond Stadial (Gemmell, 1973; Boyd and Dickson, 1987). The underlying bedrock is schistose grit of Dalradian age. The lake is fed by a small stream and has an outflow via Glen Chalmadale into Loch Ranza. The margins of the lake are overgrown by mire, and floating mats of vegetation occur in the nearshore areas. In addition, the lake surface is covered by a mosaic of small islands and tussocks of macrophyte vegetation. The lake was cored at a site within a mat of floating vegetation at the southeast end, about 50m from the edge (Boyd and Dickson, 1987). The water depth at the site was ca 60cm. The basal part of the sedimentary sequence (6.00-6.55m) was collected in 1981; the sediments from the water-sediment interface (0.60m) down to 5.75m were collected from within a few metres of the original coring site in 1982. Changes in water depth are reconstructed from changes in lithology, sedimentation rates and aquatic pollen assemblages. The chronology is based on nine radiocarbon dates. The basal sediments (3.74m+) are highly diatomaceous muds, indicating open water conditions. A sample from 6.37-6.47m was radiocarbon dated to 8610+250 yr B.P. (SRR-2580). Two further samples from 5.07-5.13m and 4.92-4.96m were dated to 7290+120 (SRR-2579) and 6880+70 (SRR-2776) yr B.P. respectively. The aquatic assemblage in the lower part of the unit (5.20-5.75m in the 1982 core) include Nymphaea, Nuphar, Potamogeton, Callitriche and moderate levels of Equisetum, consistent with moderately deep water. The appearance of Menyanthes above 5.20m suggests a decrease in water depth after ca 7600 yr B.P. The marked increase in Equisetum in the uppermost part of the unit suggests a further decrease in depth after ca 6880 yr B.P. This shallowing trend continued with the deposition of organic muds (3.55-3.74m) and peat (1.41-3.55m). The marked increase in sedimentation rate is consistent with shallowing. A sample from the base of the organic mud was dated to 5360+100 yr B.P. (SRR-2578). Samples from within the peat, at 2.88-2.92m (SRR-2577, Sphagnum peat) and 2.14-2.18 (SRR-2775, Carex peat) are dated at 4390+90 and 3930+80 yr B.P. respectively. The overlying unit (0.60-1.41m) is a diatomaceous mud, indicating a return to open water conditions. The reappearance of Potamogeton is consistent with deeper water. The timing of this increase in water level is problematic. A sample spanning the transition to diatomaceous mud (1.37-1.43m) yielded a date of 4190+80 yr B.P. (SRR-2576). It seems likely that this anomalous age is due to the incorporation of older material into the lake sediment by erosion during the initial rise in lake level. Two other samples from the unit, though reversed, yield considerably younger ages of 1370+70 (SRR-2774) and 1670+110 yr B.P. (SRR-2575). Boyd and Dickson (1987) argue that the sharp change in terrestrial pollen assemblages, the marked increase in pollen concentration, and the significant increase in the proportion of corroded and broken pollen grains at the boundary between the peat and the diatomaceous muds all suggest an hiatus in sedimentation. Extrapolation of the sedimentation rates from within the peats suggests that the hiatus occurred sometime after ca 2860 yr B.P. Boyd and Dickson (1987) suggest that the interruption of the hydroseral development (represented by the sequence from diatomaceous muds through organic mud to peats) by renewed deposition of diatomaceous muds is anomalous. They list three possible local causes of such a reversal: temporary blockage of the outlet by rapid fen peat growth, a change to more open vegetation cover in the catchment leading to increased runoff, and possible human modification of the lake associated with its use as a mill pond. They do not consider the possibility that the return to openwater conditions reflected a change in the regional water balance, most likely because it is generally assumed that lakes with an outflow are insensitive to such changes. In the coding we assume that the change reflects a change in regional water balance. Confirmation or rejection of this hypothesis depends on the degree to which Loch A'Mhuilinn is found to display a similar pattern to other lakes in the region. In the status coding, 0 indicates a possible hiatus; low (1) is indicated by peat deposition; intermediate (2) by organic mud deposition; high (3) by diatomaceous mud deposition with an aquatic assemblage including Menyanthes; and very high (4) by diatomaceous mud deposition with an aquatic assemblage characterised by deepwater species and the absence of Menyanthes. References Boyd, W.E. and Dickson, J.H., 1987. A post-glacial pollen sequence from Loch A'Mhuilinn, North Arran: a record of vegetation history with special reference to the history of endemic Sorbus species. New Phytologist 107: 221-244. Gemmell, A.M.D., 1973. The deglaciation of the Island of Arran, Scotland. Transactions of the Institute of British Geographers 59: 25-39. Radiocarbon Dates SRR-2774 1370+70 Mud, 1.03-1.07m, 1982 core SRR-2575 1670+110 Mud, 0.60-0.65m, 1982 core SRR-2576 4190+80 Mud, 1.37-1.43m, 1982 core SRR-2775 3930+60 Peat, 2.14-2.18m, 1982 core SRR-2577 4930+90 Peat, 2.88-2.92m, 1982 core SRR-2578 5360+100 Peat, 3.73-3.77m, 1982 core SRR-2776 6880+70 Mud, 4.92-4.96m, 1982 core SRR-2579 7290+120 Mud, 5.07-5.13m, 1982 core SRR-2580 8610+250 Mud, 6.37-6.47m, 1981 core Coding ca 9000-7600 yr B.P. very high (4) 7600-5400 yr B.P. high (3) 5400-5250 yr B.P. intermediate (2) 5250-2860 yr B.P. low (1) ca 2860-1600 yr B.P. hiatus (0) ca 1600- 0 yr B.P. very high (4) Preliminary coding: 12th June 1992; Final coding: 14 July 1993. Coded by SPH and GY Berrington Pool, UK Berrington Pool (52.50 N, 2.70 W, <50m above sea level) is one of a group of ca fifty small, mostly eutrophic, lowland lakes in the north west part of the English Midlands. It is a small (<10 ha) but deep (12m maximum water depth) lake (O'Sullivan, 1990). The lake lies in a kettle hole at the limit of glacial drift in south Shropshire. The area was deglaciated between 10,000 and 12,000 years ago (Farr et al., 1990; O'Sullivan, 1990). The catchment area is less than 100ha. The basin has not been greatly affected by human activity, other than its use as the village reservoir until the 1930's (Farr et al., 1990). A 5.7m-long Livingstone core and a 1m-long frozen core (B1), both taken from the centre of the lake, provide a sedimentary record from the site (Farr et al., 1990; O'Sullivan, 1990). Changes in lake depth are based on changes in lithology, laminae thickness and diatom assemblages, and broadly follow those interpreted by Farr et al. (1990) and O'Sullivan (1990). The chronology is based on a single radiocarbon date and varve counting. The core deposits show both a fine and coarse structure, with very fine light/dark couplets (5-9 per cm) and a coarser banding (amplitude ca 0.5cm). If the coarse structures are annual varves, then the 4.7m of laminated sediments would represent only 750 years of deposition. O'Sullivan (1990) argues that this implies an unrealistically high sedimentation rate for a lake with a small catchment and a single inflow. Diatom evidence suggests that the fine laminae reflect seasonal changes in the lake, indicating that these couplets are annual features (Farr et al., 1990; O'Sullivan, 1990). This would suggest that the 4.7m of laminated sediments represents ca 2500 years of sedimentation, which is consistent with the radiocarbon date of 2760±70 yr B.P. (OxA-2374) on the underlying unit (Farr et al., 1990; O'Sullivan, 1990). The basal sediment (below 467cm) is silty peat. Farr et al. (1990) interpret this unit as a subaqueous lake- marginal deposit. The lack of plant macrofossils and sand-sized material, and the presence of diatoms, areconsistent with this interpretation. A sample from this unit (OxA-2374, ca 530cm) is radiocarbon dated to 2670±70 yr B.P. The overlying sediment (467-260cm) is laminated clay, suggesting an increase in water depth. The diatom assemblage includes planktonic Stephanodiscus hantzschii, consistent with deep water after 2500 yr B.P. Changes in laminae thickness and diatom abundance allow the unit to be subdivided. Between 467-400cm, the laminae are very thin (7-9 laminae per cm), suggesting deeper water conditions ca 2500-2000 yr B.P. Between 400-260cm, the laminae become discontinuous. The disruption of the laminae suggests the water became shallower. The organic matter is less well preserved, which is consistent with shallow conditions. The clay is pink-brown in colour, indicating oxygenated water. The same planktonic diatom species are present but are less abundant. Farr et al. (1990) and O'Sullivan (1990) interpret the changes in sediment colour and diatoms as reflecting shallower water. This interval is dated to ca 2000-1200 yr B.P. The uppermost sediment is a dark brown mud (260-0cm). O'Sullivan (1990) states this lacustrine mud was deposited in a calm, anoxic depositional environment. Between 260-150cm, the sediment is characterised by fine laminae (1-2mm thick) indicating deep water ca 1200-750 yr B.P. Between 150-40cm, the laminations disappear, suggesting the lake became shallower. The uppermost part of the unit (40-0cm) has laminations ca 1- 4mm thick, suggesting an increase in water depth after ca 200 yr B.P. The diatom assemblage includes planktonic species, such as Stephanodiscus hantzschii, consistent with deep water. In the coding status, low (1) is indicated by peat; intermediate (2) by non-laminated mud or poorly-laminated clay with low abundance of planktonic diatoms; high (3) by finely laminated mud or clay with abundant planktonic diatoms. References O'Sullivan, P.E., 1990. Studies of varved sediments in the Shropshire-Cheshire meres, UK. In: Saarnisto, M. and Kahra, A. (eds), Geological Survey of Finland, Special Paper 14: 33-46. Farr, K.M., Jones, D.M., O'Sullivan, P.E., Eglinton, G., Tarling, D.H. and Hedges, R.E.M., 1990. Palaeolimnological studies of laminated sediments from the Shropshire-Cheshire meres. Hydrobiologia 214: 279-292. Radiocarbon date OxA-2374 2670±70 yr B.P. 530cm silty peat Coding pre 2500 yr B.P. low(1) 2500-2000 yr B.P. high (3) 2000-1200 yr B.P. intermediate (2) 1200-750 yr B.P. high (3) 750-200 yr B.P. intermediate (2) 200-0 yr B.P. high (3) Preliminary coding: 26/9/1993; Final coding: 2/2/1994 Coded by GY and SPH Black Loch, UK Black Loch (56 15'N, 3 10'W, 90m above sea level) in the Ochil Hills of north Fife in eastern Scotland is a small lake (ca 1.5ha, ca 200mx75m), but was formerly of greater size (Edwards and Whittington, 1993). The maximum water depth is ca 3m. It is an open lake with a minor stream entering from the north-west and an exit to the south-east. The catchment area is 142.3ha. Soils are mainly of the freely drained Brown Forest type, derived from Lower Devonian lavas. The basin originated as an ice-scoured hollow. There are four cores (BL I, II, III and IV) from the lake (Whittington et al., 1991a, b; Edwards and Whittington, 1993). The two more central cores, BL I (7.5m long) and BL III (3.8m long) consist of uniform lacustrine mud and cover only the last 3700 and 3500 years respectively. Two marginal cores BL II (7m long, taken in a water depth of 1.76m) and BL IV (5.7m long, taken in a water depth of 0.6m) provide a sedimentary record back to before 12,600 yr B.P. Edwards and Whittington (1993) discuss the evidence for water-level changes at this site. The reconstruction given here is based on changes in lithology, sedimentation rates, geochemistry and aquatic pollen assemblages, and follows that of Edwards and Whittington (1993). The chronology is based on 25 radiocarbon dates, 11 from BL I and 14 from BL II (Whittington et al., 1991b). Discrepancies in the radiocarbon dating of apparently synchronous pollen zone boundaries in the two cores are of the order of ca 50- 400 years (Whittington et al., 1991b), and this provides a measure of the dating control on the reconstructed record of hydrological change. The basal sediment (below 678 cm in BL II and below 561 in BL IV) is clay. There is no aquatic pollen. The deposition of clay even at marginal sites suggests there was a large lake before ca 12,600 yr B.P. A sample from this unit is dated to 12,670±150 yr B.P. (SRR-2626, 6.64-6.74m in BL II). The overlying sediments are organic clay in BL II (678-662cm) and coarse detritus mud in BL IV (651-530cm). The increase in organic content, and particularly the presence of detrital material in BL IV, indicates a decrease in water depth. There are no aquatics. This interval of shallower water is dated to ca 12,600-11,600 yr B.P. Inorganic clay (662-640cm) deposition in BL II after 11,600 yr B.P. suggests an increase in depth. A decrease in sedimentation rate (from 0.05 to 0.02 cm/yr) is consistent with this interpretation. The continuation of coarse detritus mud deposition in BL IV suggests the increase in depth was slight. The overlying sediments in BL II (640-617cm) are fine organic detritus mud, suggesting a decrease in water depth. Increased sedimentation rates (>0.04 cm/yr) with increased organic values (mean 85%), suggest a high energy depositional environment, consistent with shallowing. The aquatic assemblage in BL II is characterised by the appearance of Potamogeton and Nymphaea. In BL IV, this interval is represented by coarse mud deposition. The lower part of the unit (530-524cm) contains wood fragments, but these are absent from the upper part (512-456cm). The lithology and presence of wood detritus are consistent with the evidence from BL II for decreased water depth. A continuation of the shallowing trend is indicated by the deposition of coarse organic detritus mud in both BL II (617-358 cm) and BL IV (456-116cm). The occurrence of wood fragments in both cores is consistent with shallowing. There are very few aquatics. According to the radiocarbon dates, this interval is estimated to 7700- 4700 yr B.P. In BL II (358-196cm), there is organic detritus mud without wood fragments. In the more central cores (BL I, 0- 700cm; BL III, 0-350cm) there is fine organic detritus mud. The lithology of the four cores suggests the lake was rising after ca 4700 yr B.P. The aquatic assemblage was marked by increases in Potamogeton and Nymphaea, consistent with increased water depth. Sedimentation rate decreased from 0.11 to 0.02 cm/yr, consistent with this interpretation. An interval of lowered water-level is indicated by an hiatus in sedimentation in the marginal core BL IV, indicated by the absence of part of the pollen sequence (upper half of zone BL IVd to lower part of BL IVg) (Whittington et al., 1991a, b). This interpretation is consistent with the high levels of damaged pollen, abundance of Alnus fragments, highly variable pollen concentrations, increasing representation of the resistant spores of Filicales, and very low sedimentation rates (0.02 cm/yr) in this part of the core (Whittington et al., 1991a, b). There is no evidence for an hiatus in the other cores, which are characterised by continued coarse (BL II) or fine (BL I and III) organic detritus mud as before. However, increases in mineral matter, the silt and clay fraction, and damaged pollen in cores BL I and BL III are consistent with shallowing. In BL II, there is a marked increase in Potamogeton to maximum abundances (150-30cm) and an increase in Equisetum, both consistent with shallower conditions. The interval of very shallow water/hiatus is dated to between ca 3000- 1000 yr B.P. The uppermost sediments are coarse organic detritus mud in BL II (30-0cm) and BL IV (32-0cm) and fine detritus mud in the central cores (BL I and BL III). The occurrence of coarse organic detritus mud in the marginal cores indicates rising water level. The aquatic assemblage is characterised by increased Potamogeton, Nymphaea and Myriophyllum, consistent with deeper water. Sedimentation rate decreased from 0.47 to 0.18 cm/yr in BI I, consistent with rising water level. Edwards and Whittington (1993), noting the representation of Cannabis pollen in these sediments, suggest that the rise in water level after 1000 yr B.P. might have resulted from damming for hemp retting activities. In the absence of any definite evidence for this, we have assumed that the change is equally likely to have resulted from regional climate changes, and have coded the record accordingly. In the status coding, very low (0/1) is indicated by coarse organic detritus mud in the lake centre and hiatus in core BL IV; low (2) by coarse organic detritus mud; intermediate (3) by clay or fine detritus mud in core BL II and coarse detritus mud in core BL IV; moderately high (4) by inorganic clay in core BL II and coarse detritus mud in core BL IV; high (5) by clay deposited over the whole of the lake. Radiocarbon dates UB-2290 615±65 1.40-1.50m fine detritus mud core I UB-2291 920±65 1.95-2.05m fine detritus mud core I UB-2293 1125±70 2.95-3.05m fine detritus mud core I UB-2292 1470±70 2.45-2.55m fine detritus mud core I, ATO UB-2294 1885±75 3.45-3.55m fine detritus mud core I UB-2295 2015±75 3.95-4.05m fine detritus mud core I SRR-2613 2060±100 1.075-1.125m fine detritus mud core II UB-2296 2235±75 4.38-4.48m fine detritus mud core I UB-2297 2525±50 4.95-5.05m fine detritus mud core I UB-2230 2700±75 6.33-6.43m fine detritus mud core I, ATY UB-2298 2840±75 5.45-5.55m fine detritus mud core I UB-2299 3070±105 5.95-6.05m fine detritus mud core I SRR-2614 3280±110 1.675-1.725m coarse detritus mud core II SRR-2615 3890±180 2.275-2.325m coarse detritus mud core II SRR-2616 4460±110 2.725-2.775m coarse detritus mud core II SRR-2617 4690±80 3.275-3.325m coarse detritus mud core II SRR-2618 4780±80 3.575-3.625m coarse detritus mud core II SRR-2619 5180±80 4.075-4.125m coarse detritus mud core II SRR-2620 5400±80 4.575-4.625m coarse detritus mud core II SRR-2621 5960±80 5.075-5.125m coarse detritus mud core II SRR-2622 6200±80 5.575-5.625m coarse detritus mud core II SRR-2623 7110±80 6.075-6.125m coarse detritus mud core II SRR-262 7660±80 6.270-6.370m coarse detritus mud core II SRR-2625 11,620±150 6.450-6.550m coarse detritus mud core II SRR-2626 12,670±150 6.640-6.740m coarse detritus mud core II References Edwards, K.J. and Whittington, G., 1993. Aspects of the environmental and depositional history of a rock basin lake in eastern Scotland, UK. In: McManus, J. and Duck, R.W. (eds), Geomorphology and Sedimentology of Lakes and Reservoirs. John Wiley and Sons Ltd, pp 155-180. Whittington, G., Edwards, K.J. and Cundill, P., 1991a. Palaeoecological investigations of multiple elm declines at a site in north Fife, Scotland. Journal of Biogeography 18: 71-87. Whittington, G., Edwards, K.J. and Cundill, P., 1991b. Late- and post-glacial vegetational change at Black Loch, Fife, eastern Scotland-a multiple core approach. New Phytologist 118: 147-166. Coding pre 12600 yr B.P. high (5) 12600-11100 yr B.P. moderately high (4) 10100-7700 yr B.P. intermediate (3) 7700-4700 yr B.P. low (2) 4700-3000 yr B.P. intermediate (3) 3000-1000 yr B.P. very low (0/1) 1000-0 yr B.P. intermediate (3) Preliminary coding: 13/6/1993; Final coding: 24/2/1994 Coded by GY and SPH Borralan, UK Loch Borralan (58 3'N, 4 54'W, 139m above sea level) is a small shallow loch in a hollow on a gently undulating plain of glacial drift (Haworth, 1976). The area is ca 77ha, the mean depth is 2.9m and the maximum depth is 6.4m. The lake is fed by inflows from the southeast and drains via the River Ledbeg into Loch Cam. It is thus part of the Fionn Loch drainage system. The catchment area is 1680ha. Loch Borralan lies beyond the limit of the Loch Lomond Readvance, which is correlated with the Younger Dryas interval (Pennington et al., 1972). The bedrocks within the catchment is Torridonian sandstone and Lewisian gneiss with igneous intrusions (Pennington and Sackin, 1975). These are covered with drift. A thick mantle of peat is developed upon the drift. There is very little soil development (Pennington et al., 1972). A single core (2.4m long) from a water depth of 3.5m has been studied by pollen (Pennington et al., 1972) and diatom analysis (Haworth, 1976). Changes in water depth are reconstructed from changes in lithology, sedimentation rates, aquatic pollen and diatom assemblages. The dating is based on correlation of the pollen and diatom stratigraphy with the nearby site of Loch Cam which is less than 8km east of Borralan (Haworth, 1976; Harkness and Wilson, 1979). The core bottoms out in silt and silt with sand (below 240cm in core). The basal sediment (240-225cm) is clay mud. The diatom assemblage is characterised by benthic taxa (Fragilaria brevistriata, F. construens). The lithology and diatom assemblage suggest shallow water ca 13000 and 12700 yr B.P. The overlying sediment (225-191cm) is slightly organic silt clay with moss threads, suggesting shallowing between ca 12700 and 11400 yr B.P. The dominant diatoms are alkaliphilous taxa (92%) with some typical rheophilous species, such as Navicula contenta, Meridion arculars and Ceratonis arcus. Haworth (1976) considered this assemblage to indicate strong erosion in the basin. The overlying sediment (191-188cm) is organic clay, suggesting a rise in water level. The aquatic pollen assemblage contains some Myriophyllum and Potamogeton. Planktonic diatoms such as Cyclotella spp. and Stephanodiscus astraea are abundant, consistent with increased water depth after ca 11400 yr B.P. Detritus silt occurs between 188-173cm, suggesting the lake was low between ca 11300 and 10700 yr B.P. There are no marked changes in the aquatic pollen and diatom assemblages. The overlying sediments (173-167cm) are clay, suggesting the water depth increased. The aquatic assemblage is characterised by only sparse Myriophyllum. The unit contains some planktonic diatoms, consistent with increasing depth between ca 10700 and 10600 yr B.P. The overlying sediment (167-163cm) is silt, suggesting decreased water level between 10600 and 10400 yr B.P. A decrease in planktonic diatoms is consistent with shallowing. The overlying sediment (above 163cm in core) is lake mud. The basal mud (163-150cm) contains high percentages of planktonic diatoms (e.g. Asterionella formosa), suggesting increased water depth. Only rare aquatics occur (Potamogeton and Isoetes), consistent with deep water. This interval is dated to ca 10400 and 9900 yr B.P. In the middle part of this unit (150-80cm), the mud is more organic, suggesting that the lake became shallower. Isoetes reaches 40%, and Potamogeton and Myriophyllum disappear, consistent with shallow water during ca 9900-6300 yr B.P. On the basis of the terrestrial pollen assemblages, Pennington et al. (1972) suggest that there is an unconformity at the beginning of pollen zone Vi (which is dated to 6300-5000 yr B.P.). They imply that this unconformity may have resulted from erosion and reworking during an interval when the lake was less deep than today. The length of the unconformity is difficult to assess, but may have spanned the interval from ca 6300-5400 yr B.P. The uppermost part of sediment (80-20cm) consists of lake mud, indicating increased water depth after ca 5400- 5000 yr B.P. The pollen assemblage is characterised by a sharp decrease in Isoetes and the occurrence of Potamogeton and Myriophyllum, consistent with moderately shallow water. In the status coding: a possible hiatus is indicated by (0); low by (1) detritus silt, silt, silty clay with moss layer, and with benthic or alkaliphilous diatoms dominant; intermediate (2) by organic muds, with deep-water aquatics such as Isoetes, Potamogeton and Myriophyllum, and planktonic diatoms; high (3) by relatively inorganic clay or mud with sparse aquatic pollen (depauperate aquatic assemblage) and high abundance of planktonic diatoms. References Harkness, D. and Wilson, H., 1979. Scottish University research and reactor centre radiocarbon measurements III. Radiocarbon 21: 203-256. Haworth, E.Y., 1976. Two Late-glacial (Late Devensian) diatom assemblage profiles from Northern Scotland. New Phytologist 77: 227-256. Pennington, W., Haworth, E.Y., Bonny, A.P. and Lishan, J.P., 1972. Lake sediments in Northern Scotland. Philosophical Transactions of Royal Society of London 264 (B): 191-293. Pennington, W. and Sackin, M.J., 1975. An application of principal components analysis to the zonation of two Late-Devensian profiles, I. Numerical analysis. New Phytologist 5: 419-440. Coding ca 13000-12700 yr B.P. low (1) ca 12700-11400 yr B.P. low (1) ca 11400-11300 yr B.P. high (3) ca 11300-10700 yr B.P. low (1) ca 10700-10600 yr B.P. high (3) ca 10600-10400 yr B.P. low (1) ca 10400-9900 yr B.P. high (3) ca 9900-6300 yr B.P. intermediate (2) ca 6300-5000 yr B.P. hiatus (0) ca 5400-0 yr B.P. intermediate (2) Preliminary coding: 19/3/1993; Final coding: 27/7/1993. Coded by SPH and GY Cam, UK Loch Cam (58 5'N, 5 0'W, 123.5m above sea level) is part of the Fionn Loch drainage system. It is fed by inflows from the River Ledbeg which drains Lochs Urigill and Borralan. There is an outflow via Loch Veyatie into Loch Fionn and from thence via the River Kirkaig to the sea. The Fionn Loch drainage system was once the site of a large lake (Loch Suilven) that covered the area now occupied by Lochs Cam, Veyatie and Fionn (Boyd, 1956). Loch Cam lies beyond the limit of the Loch Lomond Readvance, which is correlated with the Younger Dryas interval. The area is geologically complex as it overlies the Moine Thrust, and the catchment includes schists, Lewisian gneiss and limestone. The bedrock is partly mantled by drift. A thick mantle of peat is developed upon the drift. There is very little soil development (Pennington et al., 1972). Loch Cam has an area of 262ha, a mean depth of 11.6m and a maximum depth of 37m. The catchment area is 4140ha. The main part of Loch Cam is long and narrow, with two deep basins both reaching maximum depths of 37m. There is a shallower embayment (Camas Leathan) on the southern shore and it is also wider and shallower at the southeast end. The bottom deposits in the southeast end are mostly sand, but organic deposits are found in Camas Leathan. Wave-cut soil and peat profiles occur round the shores of Loch Cam (Haworth, 1976), but it is unclear whether these represent past higher water levels or erosion during storm events. Chemical analysis indicates that the loch water is slightly acid (pH=6); calcium and sodium are the major anions, and carbonate and chloride the major anions. The levels of sodium and magnesium are relatively high and probably reflect proximity to the sea. The level of carbonate is unusually low for a lake with limestone in the catchment (Haworth, 1976). Two 6m long cores (72-7 and 72-9) taken in the central part of Camas Leathan (in a water depth of 14m) provide a stratigraphic record back to ca 13000 yr B.P. (Haworth, 1976; Pennington, 1975). Sediment between 6m and ca 5m in core 72-7 was used for pollen (Pennington et al., 1975), diatom analyses (Haworth, 1976), and radiocarbon dating (Pennington, 1975; Harkness and Wilson, 1979). Chemical analyses were made on core 72- 9 (Pennington and Sackin, 1975). According to Harkness and Wilson (1979), there is a core (core 72-10) nearby core 72-7, from which 8 samples have been radiocarbon dated (SRR-238 to SRR-245). The basal sediment in core 72-7 (600-594cm) consists of soft grey clay with low organic content. A few benthic diatoms occur, mainly Fragilaria construens, F. elliptica and unidentified F. spp. There are no planktonic taxa. The diatoms suggest the lake was only moderately deep before ca 13,000 yr B.P. The overlying sediment (594-580cm) consists of grey clay silt. An increase in the organic and calcareous contents of the sediments is consistent with shallowing. Most diatoms are alkaliphilous, though a low percentage of planktonic diatoms occur. Between 594-587cm there is a layer of light-brown slightly organic silt when rheophilous diatoms are dominant, suggesting a short erosional phase. In the upper part some aerophilous diatoms occur (Achnanthes exilis, Cymbella brehmii, Navicula bryophila etc), indicating increased erosion. During this period from ca 13,000 to 11,800 yr B.P., it seems likely that conditions in the basin were unstable. A sample from the lowermost part of this unit has been radiocarbon dated to 12940±240 yr B.P. (SRR-253, 5.84-5.94m). The overlying sediment (580-550cm) is grey-brown organic silt, suggesting shallower conditions. The occurrence of benthic diatoms is consistent with moderate water depth. The aquatic pollen includes abundant Typha, consistent with shallower conditions between ca 11,800 and 11,000 yr B.P. A sample from this unit has been radiocarbon dated to 11920±230 yr B.P. (SRR-252, 5.75-5.84m). The overlying sediment (550-536cm) consists of grey clay. The decrease in organic content is consistent with increased depth. The unit contains abundant planktonic diatoms (such as Cyclotella spp.). Some aquatic pollen (Potamogeton) occurs in the upper part of this unit. Changes in the diatoms and aquatics suggest that the lake became deeper ca 11000-10400 yr B.P. Two samples from this unit have been radiocarbon dated to 10600±450 (SRR-248, 5.36-5.45cm) and 10700±490 yr B.P. (SRR-249, 5.45-5.55m) respectively. The overlying sediment (536-513cm) is grey-brown organic mud. The increased organic content suggests the lake became shallower. Benthic diatoms such as Fragilaria pinnata and F. brevistriata become dominant, and planktonic diatoms decrease in abundance, consistent with shallowing. There is a lot of Sphagnum. This interval is dated to ca 10,400-9200 yr B.P. Two samples from the unit have been radiocarbon dated to 10230±190 (SRR-247, 5.26-5.36m) and 9220±70 yr B.P. (SRR-246, 5.13-5.23cm). According to Harkness and Wilson (1979), Holocene sedimentation in the basin is represented by lake gyttja. The diatom and pollen records from this interval have not been published. We assume the gyttja represents moderate water levels during the Holocene. The lake still has a water depth to 37m in the centre. In status coding: low (1) is indicated by grey-brown organic silt or mud or gyttja with benthic diatoms and aquatic Typha or Sphagnum; intermediate (2) by clay or silt clay with few benthic diatoms or alkaliphilous diatoms; high (3) by grey clay with planktonic diatoms and Potamogeton. References Boyd, A.J., 1956. The evolution of the drainage of the Fionn Loch area, Sutherland. Transactions of Edinburgh Geology Society 16: 229. Harkness, D. and Wilson, H., 1979. Scottish University research and reactor centre radiocarbon measurements III. Radiocarbon 21: 203-256. Haworth, E.Y., 1976. Two Late-glacial (Late Devensian) diatom assemblage profiles from Northern Scotland. New Phytologist 77: 227-256. Pennington, W., 1975. A chronostratigraphic of Late-Weichselian and Late-Devensian subdivisions illustrated by two radiocarbon-dated profile from western Britain. Boreas 4: 157-171. Pennington, W., Haworth, E.Y., Bonny, A.P. and Lishan, J.P., 1972. Lake sediments in Northern Scotland. Philosophical Transactions of Royal Society of London 264 (B): 191-293. Pennington, W. and Sackin, M.J., 1975. An application of principal components analysis to the zonation of two Late-Devensian profiles, I. Numerical analysis. New Phytologist 75: 419-440. Radiocarbon dates SRR-238 3100±80 1.80-1.90m organic mud Core 70-10 SRR-239 3100±80 2.10-2.20m organic mud Core 70-10 SRR-240 4100±70 3.00-3.10m organic mud Core 70-10 SRR-241 4590±80 3.50-3.60m organic mud Core 70-10 SRR-242 5460±70 4.00-4.10m organic mud Core 70-10 SRR-243 6790±80 4.50-4.60m organic mud Core 70-10 SRR-244 8360±100 5.00-5.10m organic mud Core 70-10 SRR-246 9220±70 5.13-5.23m organic mud Core 72-7 SRR-245 9540±90 5.40-5.50m organic mud Core 70-10 SRR-247 10230±190 5.26-5.36m clay Core 72-7 SRR-248 10600±450 5.36-5.45m organic silt Core 72-7 SRR-249 10700±490 5.45-5.55m organic silt Core 72-7 SRR-250 12440±220 5.55-5.65m organic silt Core 72-7, ATO SRR-251 12760±190 5.65-5.75m organic silt Core 72-7, ATO SRR-252 11920±230 5.75-5.84m organic silt Core 72-7 SRR-253 12940±240 5.84-5.94m organic silt Core 72-7 Note: There are slight discrepancies in the radiocarbon dates (SSR-246 to SRR-253) given by Harkness and Wilson (1979), which we use here, and by Pennington (1975). Coding ? -13000 yr B.P. intermediate (2) 13000-11800 yr B.P. intermediate (2) 11800-11000 yr B.P. low (1) 11000-10400 yr B.P. high (3) 10400- 0 yr B.P. intermediate (2) Preliminary coding: 17/3/1993; Final coding: 27/7/1993. Coded by SPH and GY Crose Mere, UK Crose Mere (52 50'N, 2 50'W, 87m above sea level) is a dimictic lake in England (Beales, 1980). It has an area of 15.2 ha and a maximum depth of 9.2m. The catchment is 215.4ha. There is drainage from Crose Mere eastward into Sweat Mere. The lake water is rich in Ca2+ and HCO3- with a conductivity of ca 300 to 400 µmho/cm (Reynolds, 1973). The lake basin lies in an area covered by moraine boulder clay, and outwash gravels and sand. The underlying bedrock is Triassic, with Bunter and Keuper sandstones, Keuper waterstones and marl. The soils are predominantly brown earths. The lake was artificially lowered ca 2-3m by drainage operations in 1864 AD (Hardy, 1939). A 4.5m-long core taken from the deepest part of the lake provides a sedimentary record back to ca 14,000 yr B.P. (Beales, 1980). The chronology is provided by 11 radiocarbon dates from this core. Changes in water depth are reconstructed from changes in lithology, aquatic pollen assemblages and sedimentation rate, and broadly follow those outlined by Beales (1980). The basal sediment (612-607cm) is silty clay of low organic content, suggesting deep water. The aquatic pollen assemblage is characterised by Nuphar, Myriophyllum alterniflorum and Potamogeton, consistent with deep water. Extrapolation of a sedimentation rate of 0.02 cm/yr from the lowest radiocarbon date (Q-1240, 10310±210 yr B.P. from 526-536cm) suggests the unit was formed between ca 13,900 and 13,500 yr B.P. The overlying sediments (607-592 cm) are silty fine detritus mud of high mineral content (70-90%) and slightly increased organic content. The increase in mineral contents suggest the lake became shallow after ca 13,500 yr B.P. The aquatic assemblage is dominated by Sparganium, Typha latifolia and Potamogeton, consistent with relatively shallow water. The overlying unit (592-581cm) is silt and fine sand. The coarse nature of the sediment suggests shallowing continued after ca 13,300 yr B.P. The aquatic assemblage, which includes Typha latifolia and Ranunculus trichophyllus, is consistent with shallow water. The overlying unit (581-490cm) is silty fine detritus mud, suggesting increased water depth. The aquatic assemblage includes Sparganium, Myriophyllum alterniflorum and Potamogeton, consistent with increased depth. This interval is dated to ca 12,800-9010 yr B.P. The overlying sediment (490-481cm) is sandy fine detritus mud. The coarse nature of the sediments suggests shallowing. The aquatic assemblage is dominated by Potamogeton, Sparganium and Ranunculus trichophyllus. The increases in Sparganium and Ranunculus trichophyllus are consistent with shallowing. A sharp increase in sedimentation rate from 0.01 to 0.13 cm/yr is also consistent with this interpretation. These changes took place from ca 9010 to 8940 yr B.P. The overlying unit (481-269cm) is fine detritus mud of low mineral content, indicating deeper water between ca 8940-3700 yr B.P. However, there are marked increases in mineral content between 447-407cm (ca 8510-7900 yr B.P.) and 395-380cm (ca 4190-6800 yr B.P). Beales (1980) interprets these intervals as reflecting low water levels. The sediment from 269 to 70 cm is detritus mud, suggesting slightly decreased water depth. Changes in mineral content and sedimentation rate allow this unit to be subdivided. Higher mineral content (40%) and higher sedimentation rate (0.21 cm/yr) between 264-146cm, suggests decreased depth ca 3700-2090 yr B.P.. Lower mineral content (20%) and lower sedimentation rate (0.07 cm/yr) between 146-110cm, indicates increased depth ca 2090-1610 yr B.P. Archaeological evidence shows that there was open water between Crose Mere and Whattall Moss during Roman times. Now the lake is separated from Whattall Moss to the north by a gravel ridge, indicating the lake during Roman times was 2.5m higher than its present level (Beales, 1980), consistent with the lithological interpretation. A return to higher mineral content (50%) and higher sedimentation rate (0.15 cm/yr) between 110-70cm, suggests the lake became shallow ca 1610-1240 yr B.P. The top unit (70-10 cm) is fine detritus mud, suggesting increased water depth. The aquatic assemblage is characterised by Myriophyllum alterniflorum, and Nymphaea alba, consistent with moderately deep water. The sedimentation rate decreased from 0.15 to 0.05 cm/yr, suggesting a rise water level in the past ca 1240 years. Modern lake level is artificially low, but the lake is still 9.2m deep in the centre. In the status coding: very low (1) is indicated by silt and fine sand with Typha and Cladium; low (2) by silty or sandy detritus mud with high mineral content and abundant Sparganium and Ranunculus; intermediate (3) by detritus mud with increased mineral content and sedimentation rate; moderately high (4) by detritus mud with low mineral content and sedimentation rate; high (5) by fine detritus mud or silt clay with Nuphar, Myriophyllum and Potamogeton. References Beales, P.W., 1980. The late Devensian and Flandrian vegetational history of Crose Mere, Shropshire. New Phytologist 85: 133-161. Hardy, E.M., 1939. Studies of the Post-glacial history of British Vegetation. V. New Phytologist 38: 364. Reynolds, C.S., 1973. The phytoplankton of Crose Mere, Shropshire. British Phycological Journal 8: 153. Radiocarbon dates Q-1230 1055±75 yr B.P. 0.46-0.48m fine detritus mud Q-1231 1610±75 yr B.P. 1.10-1.19m detritus mud Q-1232 2086±75 yr B.P. 1.46-1.54m detritus mud Q-1233 2310±85 yr B.P. 1.92-2.01m detritus mud Q-1234 3714±130 yr B.P. 2.58-2.68m fine detritus mud Q-1235 5296±150 yr B.P. 3.59-3.68m fine detritus mud Q-1236 7373±110 yr B.P. 4.03-4.11m fine detritus mud Q-1237 8502±190 yr B.P. 4.43-4.51m fine detritus mud Q-1238 8730±200 yr B.P. 4.58-4.67m silt and fine sand Q-1239 9136±210 yr B.P. 5.10-5.20m silty fine detritus mud Q-1240 10310±210 yr B.P. 5.26-5.36m silty fine detritus mud Coding ca 14,000-13,500 yr B.P. high (5) ca 13,500-13,300 yr B.P. low (2) ca 13,300-12,800 yr B.P. very low (1) ca 12,800-9010 yr B.P. intermediate (3) ca 9010-8940 yr B.P. low (2) ca 8940-8510 yr B.P. high (5) ca 8510-7900 yr B.P. intermediate (3) ca 7900-6800 yr B.P. high (5) ca 6800-4200 yr B.P. intermediate (3) ca 4200-3700 yr B.P. high (5) ca 3700-2090 yr B.P. intermediate (3) ca 2090-1610 yr B.P. moderately high (4) ca 1610-1240 yr B.P. intermediate (3) ca 1240-0 yr B.P. high (5) Preliminary coding 26/2/1993; Final coding: 25/5/1994 Coded by GY and SP Diss Mere, UK Diss Mere (52 22'N, 1 6'E, 26m above sea level) is a small lake in East Anglia, UK. The lake has an area of 3.4ha and a maximum water depth of 6.2m. There is no outflow or inflow, and the area of the hydrological catchment is limited (Peglar et al., 1989). It is a highly eutrophic lake with a pH value of 9.0, an alkalinilty of 3.86 meq/l and a conductivity of 582 µS/cm (Peglar et al., 1984). The bedrock in the catchment is Upper Chalk, covered by 30m thick of chalky clay till (Lowestoft Till, the Anglian glaciation). The lake occupies a doline and probably formed by solution of chalk and collapse of local drift in the late glacial (Peglar et al., 1989). The stratigraphy of the lake deposits has been reconstructed by two cores from the deepest part of the lake (Peglar et al., 1984; Fritz, 1989; Peglar et al., 1989). A 17m-long composite stratigraphy, based on two cores (core 1979 and core 1980 from a water depth of 6.2m) provides lithological, pollen, diatom and algal records back to ca 12,000 yr B.P. Changes in water depth are reconstructed from changes in lithology, lamination structures, diatom and blue-green algae assemblages, and sedimentation rate, and generally follow those described by Peglar et al. (1989) and Fritz (1989). The chronology is based on annual laminations, archeological evidence and historical records (Peglar et al., 1984 and 1989) for the late Holocene; and on pollen correlations with nearby radiocarbon-dated sites (Peglar et al., 1989): Hockham Mere (Sims, 1978; Bennett, 1983), Saham Mere (Bennett, 1988) and The Mere, Stow Bedon (Bennett, 1986) for the earlier part of the record. The basal sediment is clay and silt (2320-2204cm below water surface). In the lower part of this unit, there are sand lenses (around 2239cm below water surface), indicating shallow water. Pollen is absent or extremely rare and the diatoms are poorly preserved. Peglar et al. (1989) suggest that this poor preservation probably reflects solifluction or reworking during the shallow water phase after ca 12,000 yr B.P. At 2287cm below water surface, the diatom concentration increases and the assemblage is dominated by planktonic diatoms (Cyclotella comta and C. kutzingiana), suggesting increased water depth, ca 10,500-9500 yr B.P. There is a depositional hiatus around 2204cm below the water surface, indicated by abrupt changes in the terrestrial pollen assemblages (sharp increase in Corylus from <1% to 70% and decrease in Betula from 80% to 14%), and the absence of diatoms. Peglar et al. (1989) assume this hiatus reflects a water level fluctuation and that the lake was ca 5m lower than the today between ca 9500-9200 yr B.P. The overlying sediment is fine detritus mud (2204-2110cm below water surface), suggesting increased depth. The diatom assemblage is dominated by planktonic Cyclotella spp., Stephanodicus spp. and Asterionella formosa, consistent with increased water depth, ca 9200-8500 yr B.P. There are two intervals with laminations within this unit (2204-2183cm below water surface and 2179-2146cm below water surface), suggesting deeper water conditions between ca 9200-9040 yr B.P. and 9010-8730 yr B.P. The diatom concentration in the laminated layers is higher than in the non-laminated part of the unit, consistent with reduced turbulence and good preservation under deeper water conditions. A marked decrease in water depth is indicated by a layer of sand (2110-2070cm below water surface). The unit has a high minerogenic content and is devoid of both pollen and diatoms, suggesting a hiatus (Birks, 1986, personal comm.) or extremely low lake level, ca 8500-8100 yr B.P. (Peglar et al., 1989). The overlying sediment is silt (2070-2030cm below water surface), suggesting increased water depth after 8100 yr B.P. The concentrations of both pollen and diatoms are low, implying oxidising and shallow water conditions. A change to fine detritus mud (2030-1824cm below water surface) suggests increased water depth after 7730 yr B.P. The diatom assemblage is characterised by planktonic Cyclotella comta and C. kutzingiana, consistent with increased water depth. In the upper part of this unit and the lower part of the overlying laminated unit (ca 1950- 1780cm below water surface), there is abundant Oscillatoria, a planktonic and anarobial blue-green alga. Fritz (1989) explains that this species lives in stable water, well-protected from wind, and that its abundance indicates stabilization of the water column, ca 6000-5000 yr B.P. The disappearance of Stephanodicus parvus and Asterionella formosa, planktonic diatoms characteristic of turbulent water, is consistent with stable and quite deep water conditions. The overlying sediment is laminated fine detritus mud (1824-1528cm below water surface). The unit has over 3000 pairs of pale and dark annual laminae, ca 1-2mm thick (Peglar et al., 1984). The preservation of thin laminated structures suggests deep water conditions. The diatom assemblage is characterised by dominance of planktonic species Stephanodicus spp., consistent with deep water. A low mineral content (10%) and low sedimentation rate (0.09 cm/yr) are also consistent with deep water. The unit is dated to ca 5500-2510 yr B.P. A decrease in water depth is indicated by the change from laminated fine detritus mud to fine detritus mud (1528-1028cm below water surface). An increase in the mineral content to 60% suggests littoral deposition in shallow water. The diatom assemblage is still dominated by planktonic species, but an increase in epiphytes (e.g. such as Fragilaria brevistriata up to 19% at 1242cm below water surface), is consistent with decreased depth. An increase in sedimentation rate from 0.10 cm/yr to 0.34 cm/yr is also consistent with shallow water. This unit is dated to ca 2510-770 yr B.P. The uppermost sediment (1028-620cm below water surface) is black fine detritus mud rich in iron sulphide. The deposit indicates anoxic bottom water and suggests quite deep water since ca 770 yr B.P. The mineral content declines at 950cm (ca 20%) and stabilises above 950cm, consistent with increased water depth. The diatom assemblage is dominated by planktonic species (Stephanodicus spp. and Cyclotella spp.), consistent with a return to deeper water. In the status coding, a possible hiatus (0) is indicated by sand or sand lens without pollen or diatoms; low (1) by silt or silt and clay with sparse pollen and diatoms; moderately low (2) by fine detritus mud with increases in epiphytic diatoms and in sedimentation rate; intermediate (3) by fine detritus mud with planktonic diatoms and with abundant planktonic blue-green alga; moderately high (4) by fine detritus mud, with iron sulphide, low mineral content and planktonic diatoms; high (5) by laminated fine detritus mud with very low mineral content. References Bennett, K.D., 1983. Devensian Late-glacial and Flandrian vegetational history at Hockham Mere, England. New Phytologist 95: 457-487. Bennett, K.D., 1986. Competitive interactions among forest tree population in Norfolk, England, during the last 10,000 years. New Phytologist 103: 603-620. Bennett, K.D., 1988. Holocene pollen stratigraphy of central East Anglia, England, and comparison of pollen zones across the British Isles. New Phytologist 109: 237-253. Birks, H.J. 1986. Personal communication. Fritz, S.C., 1989. Lake development and limnological response to prehistoric and historic land-use in Diss, Norfolk, U.K. Journal of Ecology 77: 182-202. Peglar, S., Fritz, S.C., Alapieti, T., Saarnisto, M. and Birks, H.J.B. 1984. The composition and formation of laminated sediments in Diss Mere, Norfolk, England. Boreas 13: 13-28. Peglar, S., Fritz, S.C. and Birks, H.J., 1989. Vegetation and land-use history at Diss, Norfolk, U.K. Journal of Ecology 77: 203-222. Sims, R.E., 1978. Man and vegetation in Norfolk. in: Limbrey, S. and Evans, J.G.(eds), The effect of man on the landscape: the lowland zone. Council of British Archaeology Report 21: 57-62. Coding ca 12,000-10,500 yr B.P. very low (0) ca 10,500-9500 yr B.P. low (1) ca 9500-9200 yr B.P. hiatus (0) ca 9200-9040 yr B.P. high (5) ca 9040-9010 yr B.P. intermediate (3) ca 9010-8730 yr B.P. high (5) ca 8730-8500 yr B.P. intermediate (3) ca 8500-8100 yr B.P. very low/hiatus (0) ca 8100-7730 yr B.P. low (1) ca 7730-6000 yr B.P. moderately low (2) ca 6000-5000 yr B.P. intermediate (3) ca 5500-2510 yr B.P. high (5) ca 2510-770 yr B.P. moderately low (2) ca 770-0 yr B.P. moderately high (4) Preliminary coding: 22/3/1994; Final coding: 22/5/1994 Coded by GY and SPH Bielersee, Switzerland Bielersee, Switzerland 270 269 Hobschensee, Switzerland Hobschensee, Switzerland Léman, Switzerland Léman, Switzerland Lobsigensee, Switzerland Lobsigensee, Switzerland Nussbaumerseen, Switzerland Nussbaumerseen, Switzerland Rotsee, Switzerland Rotsee, Switzerland a'Chnuic, UK a'Chnuic, UK a'Mhuilinn, UK a'Mhuilinn, UK Berrington Pool, UK Berrington Pool, UK Black Loch, UK Black Loch, UK Borralan, UK Borralan, UK Cam, UK Cam, UK Crose Mere, UK Crose Mere, UK Diss Mere, UK Diss Mere, UK