# Lake Bosumtwi, Ghana Late Quaternary Magnetic Mineral Data #---------------------------------------------------- # World Data Service for Paleoclimatology, Boulder # and # NOAA Paleoclimatology Program # National Centers for Environmental Information (NCEI) #---------------------------------------------------- # Template Version 4.0 # Encoding: UTF-8 # NOTE: Please cite original publication, NOAA Landing Page URL, dataset and publication DOIs (where available), and date accessed when using downloaded data. If there is no publication information, please cite investigator, study title, NOAA Landing Page URL, and date accessed. # # Description/Documentation lines begin with # # Data lines have no # # # NOAA_Landing_Page: https://www.ncei.noaa.gov/access/paleo-search/study/5454 # Landing_Page_Description: NOAA Landing Page of this file's parent study, which includes all study metadata. # # Study_Level_JSON_Metadata: https://www.ncei.noaa.gov/pub/data/metadata/published/paleo/json/noaa-lake-5454.json # Study_Level_JSON_Description: JSON metadata of this data file's parent study, which includes all study metadata. # # Data_Type: Paleolimnology # # Dataset_DOI: 10.25921/149q-tg68 # # Science_Keywords: #-------------------- # Resource_Links # # Data_Download_Resource: https://www.ncei.noaa.gov/pub/data/paleo/paleolimnology/africa/bosumtwi2004-freeze-noaa.txt # Data_Download_Description: NOAA Template File; Composite Cores BOS 99-11 and BOS 99-12 Rock Magnetic Data # #-------------------- # Contribution_Date # Date: 2007-01-01 #-------------------- # File_Last_Modified_Date # Date: 2024-04-22 #-------------------- # Title # Study_Name: Lake Bosumtwi, Ghana Late Quaternary Magnetic Mineral Data #-------------------- # Investigators # Investigators: Peck, J.A.; Green, R.R.; Shanahan, T.M.(https://orcid.org/0000-0002-3831-3198); King, J.W.; Overpeck, J.T.(https://orcid.org/0000-0002-3843-9313); Scholz, C.A. #-------------------- # Description_Notes_and_Keywords # Description: Lake Bosumtwi, Ghana (6°30'N, 1°25'W, 99m. elev.). In June, 2000, 19 piston cores were extracted from Lake Bosumtwi. Eight short piston cores (1N-8N), ranging from 108 to 134 cm in length, were used to capture the sediment-water interface. These cores were supplemented by two freeze cores obtained from the deepest portion of the lake. The remaining 11 longer cores, ranging from 5.5 to 10.9 m in length, did not preserve the sediment-water interface, but were correlated with the shorter cores using well-defined marker bands. Physical property logging of whole core volumetric magnetic susceptibility and gammaray attenuation (an estimation of wet bulk density) was conducted on the piston cores using an automated Geotek multisensor core logger. #-------------------- # Publication # Authors: Peck, J.A., R.R. Green, T. Shanahan, J.W. King, J.T. Overpeck, C.A. Scholz # Journal_Name: Palaeogeography, Palaeoclimatology, Palaeoecology # Published_Title: A magnetic mineral record of Late Quaternary tropical climate variability from Lake Bosumtwi, Ghana # Published_Date_or_Year: 2004-12-02 # Volume: 215 # Pages: 37-57 # Issue: 1-2 # Report_Number: # DOI: 10.1016/j.palaeo.2004.08.003 # Full_Citation: # Abstract: We report magnetic hysteresis results from sediment cores obtained from Lake Bosumtwi, Ghana. As a hydrologically closed basin, the water budget of Lake Bosumtwi is extremely sensitive to changes in the precipitation/evapotranspiration balance. Lake Bosumtwi lies in the path of the seasonal migration of the intertropical convergence zone (ITCZ); hence, the lake is ideally situated to study monsoon variability in West Africa. Five distinctive magnetic mineral zones (A-E) were identified in the 11-m-long sediment cores that span the last 26,000 calendar years. Prior to 12 calendar (cal) ka, low concentrations of multidomain, high-coercivity magnetic minerals are present. Three prominent shifts towards very high concentrations of high-coercivity iron sulfide (greigite) magnetic minerals are centered at 12,470, 17,290, and 22,600 calendar years during the last glacial period (magnetic zones D1-3). Between 12 and 3.2 cal ka, there is an abrupt shift to moderately high concentrations of mixed multidomain and single-domain, low-coercivity minerals and an organic-rich sapropel lithology. Since 3.2 cal ka, the magnetic mineral parameters reveal a shift to increased amounts of high-coercivity magnetic minerals. # # These magnetic mineral zones document tropical climate variability on a variety of temporal scales. Glacial age sediments have a high-coercivity magnetic mineralogy due to increased aeolian dust transport from the Sahel to Lake Bosumtwi as well as postdepositional reductive diagenesis. During the last glacial period, the increased strength of Harmattan and North African continental trade winds, the southward depression of the ITCZ, and weakened summer monsoon strength resulted in increased regional aridity and greater dust flux out of Sahel source regions. The greigite-bearing D magnetic zones correspond to brief lowstands in the level of Lake Bosumtwi and likely represent periods of intensified aridity in West Africa. The D magnetic zones closely resemble the timing and duration of Heinrich events and suggest a hemispheric-scale climatic coupling between the tropics and poles. The well-documented African humid period (AHP) is characterized by abrupt shifts in magnetic parameters between 12 and 3.2 cal ka. Dust flux to Lake Bosumtwi is inferred to be very low during this humid interval due to the strengthening of the summer monsoon. Since 3.2 cal ka, the magnetic mineral parameters suggest increased aridity as compared to the AHP. This work demonstrates that the magnetic properties of Lake Bosumtwi sediment are a sensitive recorder of abrupt climate change of global significance. #-------------------- # Funding_Agency # Funding_Agency_Name: US National Science Foundation # Grant: ATM-0117019 #-------------------- # Site_Information # Site_Name: Lake Bosumtwi # Location: Ghana # Northernmost_Latitude: 6.5 # Southernmost_Latitude: 6.5 # Easternmost_Longitude: -1.4167 # Westernmost_Longitude: -1.4167 # Elevation_m: 99 #-------------------- # Data_Collection # Collection_Name: Lake Bosumtwi Peck2004 Freeze Mag # First_Year: 104 # Last_Year: -32 # Time_Unit: cal yr BP # Core_Length_m: # Parameter_Keywords: magnetic susceptibility # Notes: Standardized (composited) depth, mean year, calendar age, and rock magnetic data for the two freeze cores (BOS 99-11 and BOS 99-12). #-------------------- # Chronology_Information # Chronology: #-------------------- # Variables # PaST_Thesaurus_Download_Resource: https://www.ncei.noaa.gov/access/paleo-search/skos/past-thesaurus.rdf # PaST_Thesaurus_Download_Description: Paleoenvironmental Standard Terms (PaST) Thesaurus terms, definitions, and relationships in SKOS format. # # Data variables follow that are preceded by '##' in columns one and two. # Variables list, one per line, shortname-tab-var components: what, material, error, units, seasonality, data type, detail, method, C or N for Character or Numeric data) ## core_id sample identification,,,,,paleolimnology,,,C,core name ## depth_comp_cm depth,,,centimeter,,paleolimnology,composited,,N,standardized core depth ## age_CE age,,,year Common Era,,paleolimnology,,,N, ## age_calBP2000 age,,,calendar year before other datum,,paleolimnology,,,N,present = 2000 CE ## age_calBP age,,,calendar year before present,,paleolimnology,,,N,present = 1950 CE ## IS initial magnetization slope,sediment,,cubic meter per kilogram,,paleolimnology,,,N,IS ## Mrs saturation isothermal remanent magnetization,sediment,,milliampere square meter per kilogram,,paleolimnology,,,N,Mrs ## Ms saturation isothermal magnetization,sediment,,milliampere square meter per kilogram,,paleolimnology,,,N,Ms ## Mr_Ms saturation isothermal remanent magnetization/saturation isothermal magnetization,sediment,,dimensionless,,paleolimnology,,,N,Mr/Ms ## Hcr coercivity of remanence,sediment,,millitesla,,paleolimnology,,,N,Hcr ## Hc coercivity,sediment,,millitesla,,paleolimnology,,,N,Hc ## Hcr_Hc coercivity of remanence/coercivity,sediment,,dimensionless,,paleolimnology,,,N,Hcr/Hc ## Mrs_IS saturation isothermal remanent magnetization/initial magnetization slope,sediment,,kiloampere per meter,,paleolimnology,,,N,Mrs/IS ## S-ratio S-ratio,sediment,,dimensionless,,paleolimnology,,,N, #-------------------- # Data: # Data lines follow (have no #) # Data line format - tab-delimited text, variable short name as header # Missing_Values: NA core_id depth_comp_cm age_CE age_calBP2000 age_calBP IS Mrs Ms Mr_Ms Hcr Hc Hcr_Hc Mrs_IS S-ratio BOS 99-11 8 1981.897 18.103 -31.897 25.7 4.283 16.03 0.2672 36.22 15.24 2.38 17.23 NA BOS 99-11 8.81 1977.259 22.741 -27.259 27.85 3.982 15.21 0.2618 32.69 13.92 2.35 14.9 0.8925 BOS 99-11 8.88 1974.939 25.061 -24.939 23.49 3.796 14.17 0.2679 36.13 15.06 2.4 16.66 0.906 BOS 99-11 9.72 1970.301 29.699 -20.301 28.09 4.174 15.48 0.2696 35.16 14.53 2.42 15.43 0.9078 BOS 99-11 10.92 1965.662 34.338 -15.662 20.56 3.323 11.38 0.292 33.76 14.97 2.26 16.68 0.9128 BOS 99-11 11.9 1961.024 38.976 -11.024 21.95 3.36 12.55 0.2677 34.04 14.3 2.38 16.08 0.8973 BOS 99-11 12.72 1955.226 44.774 -5.226 32.58 3.944 15.02 0.2626 32.18 12.11 2.66 12.54 0.9196 BOS 99-11 13.38 1951.747 48.253 -1.747 18.74 3.136 10.76 0.2915 37.44 16.65 2.25 17.18 0.9153 BOS 99-11 14.02 1947.108 52.892 2.892 14.14 2.83 9.1 0.311 38.8 17.38 2.23 20.44 0.9256 BOS 99-11 14.89 1942.47 57.53 7.53 13.8 2.717 8.69 0.3126 37.45 17.1 2.19 20.29 0.9061 BOS 99-11 15.99 1936.602 63.398 13.398 16.47 2.474 8.26 0.2995 32.41 14.95 2.17 14.87 0.9156 BOS 99-11 16.66 1930.711 69.289 19.289 17.14 2.401 8.2 0.2927 33.75 14.89 2.27 14.62 0.8785 BOS 99-11 17.31 1924.843 75.157 25.157 13.72 2.524 8.19 0.3083 38.57 16.75 2.3 18.91 0.8961 BOS 99-11 18.14 1919.045 80.955 30.955 13.99 2.297 8.09 0.284 34.92 15.22 2.29 16.94 0.9058 BOS 99-11 18.29 1916.03 83.97 33.97 15.12 2.212 7.85 0.282 34.05 14.44 2.36 15.31 0.8808 BOS 99-11 18.96 1910.162 89.838 39.838 13.99 2.294 8.01 0.2866 36.85 16.12 2.29 17.87 0.8639 BOS 99-11 19.53 1907.217 92.783 42.783 12.1 2.374 7.47 0.3177 40.06 18.06 2.22 20.13 0.8932 BOS 99-11 20.66 1901.349 98.651 48.651 10.91 1.981 6.4 0.3095 37.38 16.89 2.21 19.02 0.8806 BOS 99-11 21.49 1895.087 104.913 54.913 10.47 1.938 7.04 0.2754 36.35 15.96 2.28 18.99 0.8882 BOS 99-11 21.87 1891.771 108.229 58.229 9.77 1.676 5.53 0.3029 34.55 16.07 2.15 17.84 0.8741 BOS 99-11 22.73 1885.161 114.839 64.839 12.27 1.766 6.55 0.2698 32.1 13.85 2.32 14.92 0.8537 BOS 99-11 24.22 1875.211 124.789 74.789 10.06 1.782 6.02 0.2958 36.69 16.32 2.25 18.46 0.8518 BOS 99-11 24.68 1872.428 127.572 77.572 10.74 1.844 6.36 0.29 35.61 15.83 2.25 17.71 0.8687 BOS 99-11 25.2 1869.645 130.355 80.355 8.75 1.833 5.59 0.328 38.43 17.73 2.17 20.94 0.8484 BOS 99-11 26.23 1861.296 138.704 88.704 9.58 1.972 6.03 0.327 42.05 18.95 2.22 21.12 0.8249 BOS 99-11 26.78 1858.977 141.023 91.023 9.62 1.808 5.73 0.3155 38.35 17.58 2.18 19.52 0.8513 BOS 99-11 27.4 1856.657 143.343 93.343 10.18 1.912 5.98 0.3199 36.79 17.41 2.11 19.19 0.8711 BOS 99-12 12.41 1955.5 44.5 -5.5 20.4 3.139 10.88 0.2885 34.35 14.9 2.31 15.98 0.9168 BOS 99-12 13 1952 48 -2 19.97 3.309 10.91 0.3033 35.15 15.38 2.29 17.14 0.9185 BOS 99-12 13.29 1948.5 51.5 1.5 16.13 2.979 9.547 0.312 36.77 16.94 2.17 18.95 0.9233 BOS 99-12 13.59 1946.25 53.75 3.75 15.25 2.585 8.781 0.2944 35.15 15.67 2.24 17.43 0.9229 BOS 99-12 14.21 1942.25 57.75 7.75 15.74 2.734 9.316 0.2935 36.24 15.81 2.29 17.94 0.9148 BOS 99-12 14.63 1940.25 59.75 9.75 14.89 2.841 9.43 0.3013 36.43 16.49 2.21 19.49 0.9183 BOS 99-12 15.08 1938 62 12 16.21 2.738 8.916 0.3071 34.68 15.77 2.2 17.25 0.9224 BOS 99-12 15.43 1936 64 14 13.23 2.552 8.432 0.3027 36.47 16.82 2.17 19.76 0.9236 BOS 99-12 15.84 1934 66 16 14.82 2.431 8.15 0.2983 34.92 15.62 2.24 16.9 0.9154 BOS 99-12 16.25 1932 68 18 10.44 1.8 6.126 0.2938 34.26 15.63 2.19 17.9 0.8927 BOS 99-12 16.6 1930 70 20 15.23 2.3 8.05 0.2857 31.49 13.83 2.28 15.59 0.8996 BOS 99-12 17.07 1927.75 72.25 22.25 14.26 2.36 7.758 0.3042 34.34 15.39 2.23 16.55 0.9065 BOS 99-12 17.5 1925.75 74.25 24.25 13.82 2.171 7.396 0.2935 34.29 15.14 2.26 16.27 0.9009 BOS 99-12 17.74 1924.5 75.5 25.5 14.27 2.171 7.419 0.2926 32.12 14.39 2.23 15.84 0.8988 BOS 99-12 17.76 1923.5 76.5 26.5 13.73 2.137 7.646 0.2795 33.49 14.44 2.32 16.15 0.8878 BOS 99-12 18 1922 78 28 15.87 2.132 7.915 0.2694 30.71 13.01 2.36 13.88 0.9033 BOS 99-12 18.26 1920 80 30 16.16 2.431 8.666 0.2805 34.59 14.46 2.39 15.55 0.8993 BOS 99-12 18.5 1918.25 81.75 31.75 11.58 1.514 5.605 0.2701 34.1 14.06 2.43 13.57 0.9001 BOS 99-12 18.74 1916.75 83.25 33.25 15.05 2.36 8.226 0.2869 36.03 15.11 2.38 16.33 0.8981 BOS 99-12 19 1914.5 85.5 35.5 13.42 2.465 8.089 0.3047 39.82 17.15 2.32 18.98 0.8826 BOS 99-12 19.37 1911.75 88.25 38.25 11.61 2.211 7.042 0.314 39.16 17.71 2.21 19.6 0.9003 BOS 99-12 19.93 1908.25 91.75 41.75 11.06 1.995 6.517 0.3061 35.84 16.42 2.18 18.61 0.8907 BOS 99-12 20.49 1905 95 45 8.06 1.623 5.09 0.3189 39.24 17.79 2.21 20.76 0.8673 BOS 99-12 20.86 1902.5 97.5 47.5 11.31 1.915 6.436 0.2976 34.84 15.65 2.23 17.54 0.8915 BOS 99-12 21.16 1900.5 99.5 49.5 9.07 1.955 6.506 0.3005 35.84 16.67 2.15 22.3 0.8948 BOS 99-12 21.54 1897.5 102.5 52.5 10.4 1.918 6.434 0.2981 36.73 16.63 2.21 18.97 0.872 BOS 99-12 21.99 1894 106 56 10.96 1.784 6.207 0.2874 32.71 15.23 2.15 16.86 0.892 BOS 99-12 22.32 1892 108 58 11.96 1.921 6.897 0.2785 34.63 15.56 2.23 16.53 0.8792 BOS 99-12 22.64 1890 110 60 11.76 1.824 5.887 0.3098 38.62 17.06 2.26 16.35 0.8165 BOS 99-12 22.85 1888 112 62 6.48 1.283 4.176 0.3072 37.3 17.04 2.19 20.24 0.8523 BOS 99-12 23.22 1885.5 114.5 64.5 10.98 1.741 6.073 0.2867 31.32 14.43 2.17 16.47 0.8935 BOS 99-12 23.69 1883 117 67 10.51 1.629 5.505 0.2959 32.71 15.14 2.16 16.05 0.8897 BOS 99-12 24.1 1880.25 119.75 69.75 10.57 1.801 6.049 0.2977 33.53 15.1 2.22 17.05 0.8902 BOS 99-12 24.44 1877.5 122.5 72.5 10.12 1.804 5.825 0.3097 33.87 15.71 2.16 17.83 0.8843 BOS 99-12 24.7 1875.25 124.75 74.75 10.66 1.899 6.246 0.304 37.3 16.71 2.23 18.42 0.85 BOS 99-12 25.04 1872.75 127.25 77.25 10.67 1.808 5.929 0.3049 34.84 15.89 2.19 17.36 0.8852 BOS 99-12 25.51 1869.25 130.75 80.75 10.17 1.735 5.615 0.309 33.27 15.71 2.12 17.41 0.8957 BOS 99-12 25.88 1866.5 133.5 83.5 10.04 1.794 5.688 0.3154 35.4 16.32 2.17 18.26 0.884 BOS 99-12 26.19 1865 135 85 8.96 1.516 5.345 0.2836 34.71 15.94 2.18 18.2 0.8382 BOS 99-12 26.53 1863 137 87 12.89 1.955 6.545 0.2987 33.69 14.7 2.29 15.17 0.8839 BOS 99-12 26.87 1860 140 90 10.85 1.792 6.025 0.2974 34.38 15.45 2.23 16.98 0.8827 BOS 99-12 27.28 1857 143 93 10.42 1.625 5.463 0.2975 33.15 15.1 2.2 16.32 0.8742 BOS 99-12 27.61 1855 145 95 10.87 1.77 6.059 0.2921 32.97 15.33 2.15 16.87 0.8832 BOS 99-12 28.01 1852.5 147.5 97.5 25.05 2.747 15.49 0.1773 27.5 9.95 2.76 11.3 0.8997 BOS 99-12 28.46 1850 150 100 16.68 2.032 11.33 0.1794 29.98 11.32 2.65 13.08 0.8907 BOS 99-12 28.9 1847.5 152.5 102.5 8.08 1.606 5.603 0.2866 32.67 14.72 2.22 20.39 0.8809 BOS 99-12 29.35 1846 154 104 44.92 4.262 16.94 0.2516 28.3 10.45 2.71 10.14 0.8451