Lake Malawi Biogenic Silica Data --------------------------------------------------------------------- World Data Center for Paleoclimatology, Boulder and NOAA Paleoclimatology Program --------------------------------------------------------------------- NOTE: PLEASE CITE ORIGINAL REFERENCE WHEN USING THIS DATA!!!!! NAME OF DATA SET: Lake Malawi Biogenic Silica Data LAST UPDATE: 10/2003 (Extension of record length for cores M98-1PG and M98-2PG, adding data for 1258-1670 AD for core M98-2PG and correcting timescale for core M98-1PG). CONTRIBUTOR: Thomas C. Johnson, Large Lakes Observatory, University of Minnesota - Duluth. IGBP PAGES/WDCA CONTRIBUTION SERIES NUMBER: 2001-017 SUGGESTED DATA CITATION: Johnson, T.C., et al., 2001, Lake Malawi Biogenic Silica Data, IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series #2001-017. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA. ORIGINAL REFERENCES: Johnson, T.C., Barry, S.L., Chan, Y., and Wilkinson, P., 2001, Decadal record of climate variability spanning the last 700 years in the southern tropics of East Africa, Geology, v. 29, No. 1, p. 83-86, January 2001. DeMaster, D.J., 1979, The marine budgets of silica and Si32 [Ph.D. Dissertation thesis], Yale University. GEOGRAPHIC REGION: East Africa PERIOD OF RECORD: 1258-1996 AD FUNDING SOURCES: U.S. National Science Foundation, Grant ATM-9709291. DESCRIPTION: The data are biogenic silica (as % SiO2) versus age from six cores in the north basin of Lake Malawi, at the southern end of the East African Rift Valley. The chronology is based on a combination of varve counts and Pb-210 geochronology, all tied to stratigraphic correlations of certain marker beds that can be traced among the six cores. Positions of the cores are based on GPS navigation. Biogenic silica analyses were done using the time series digestion technique of Demaster (DeMaster, 1979). The precision is ±1% SiO2. Data is presented in columns for depth in core, % biogenic silica (Bsi), and year, based on varve counts and, in two cores, Pb-210 activity. Pb-210 analyses and age assignments were done by Dr. Paul Wilkinson, Dept. of Fisheries and Oceans, Winnipeg, using alpha spectrometry. These data show strong evidence of this part of tropical Africa responding to the Little Ice Age, and are presented in Johnson et al., 2001. Data were generated in the period from 1998 to 2000. Note: The Pb-210 chronology for M98-10MC assumes the core top was 1998. However stratigraphic correlations with M98-11MC indicate that the core top is missing the top ca. 4 cm, or 18 years. The correlation is in layer H1, situated at about 10 cm in 11 MC and at 7.5 cm in 10 MC. DATA: Tab-delimited text columns for 6 Lake Malawi cores Lake Malawi Core M93-1SB 9º 49.0'S 34 06.0'E 260 m Water Depth "Depth, cm" "Bsi, %" Year AD (varve) 0-1 13 1877 1-2 12.1 1870 2-3 10.8 1863 3-4 13 1859 4-5 12.7 1854 5-6 1850 6-7 1850 7-8 1850 8-9 1850 9-10 1850 10-11 22.4 1820 11-12 19.5 1813 12-13 14.9 1807 13-14 20.8 1800 14-15 28.5 1793 15-16 16.3 1786 16-17 20.4 1777 17-18 29.8 1769 18-19 24.8 1761 19-20 16.9 1753 20-21 16.3 1745 21-22 13.6 1736 22-23 13.5 1727 23-24 1720 24-25 1720 25-26 1720 26-27 19.6 1714 27-28 29.3 1706 28-29 23.3 1699 29-30 21.9 1692 30-31 20.2 1686 31-32 21.6 1680 32-33 24.3 1676 33-34 22.4 1672 34-35 18.9 1670 35-36 13.5 1667 36-37 14.8 1663 37-38 19.5 1659 38-39 23.4 1653 39-40 17.4 1647 40-41 15.7 1643 41-42 16.4 1638 42-43 1632 43-44 1632 44-45 1632 45-46 15.1 1625 46-47 13.1 1618 47-48 16.8 1611 48-49 14.8 1603 49-50 13.5 1595 50-51 19.7 1587 51-52 16.1 1579 52-53 16.4 1570 53-54 11.9 1562 54-55 12.2 1554 55-56 14.8 1545 56-57 10.2 1536 57-58 9.3 1527 58-59 10.9 1518 59-60 10.2 1509 60-61 9.9 1500 61-62 13.5 1491 62-63 1483 63-64 1475 Lake Malawi Core M93-2SB "Depth, cm" % Biognic Si Year AD (varve) 0.5 12.8 1925 1.5 11.4 1919 2.5 8.2 1913 3.5 6.8 1908 4.5 8.9 1902 5.5 11.4 1895 6.5 13.3 1889 7.5 10.3 1883 8.5 1878 9.5 1878 10.5 8.2 1873 11.5 8.4 1867 12.5 12.4 1862 13.5 9.3 1857 14.5 1850 15.5 1850 16.5 1850 17.5 1850 18.5 1850 19.5 1850 20.5 1850 21.5 1850 22.5 19 1822 23.5 18.3 1816 24.5 12.5 1810 25.5 14.9 1804 26.5 15.6 1799 27.5 18.7 1791 28.5 19 1784 29.5 16.9 1777 30.5 23.8 1770 31.5 25.8 1765 32.5 24.5 1759 33.5 21.8 1753 34.5 20 1747 35.5 13.8 1741 36.5 12.8 1734 37.5 13 1726 38.5 1720 39.5 1720 40.5 1720 41.5 15.6 1713 42.5 15.6 1707 43.5 1701 44.5 1701 45.5 20 1694 46.5 18 1688 47.5 16.9 1683 48.5 16.5 1679 49.5 24.4 1675 50.5 21.4 1672 51.5 1670 52.5 9.7 1667 53.5 13 1663 54.5 22.9 1658 55.5 24.8 1653 56.6 18.2 1647 57.5 14.9 1641 58.5 16.4 1635 59.5 15.4 1629 60.5 1624 61.5 1624 62.5 14.5 1618 63.5 16.6 1611 64.5 16.2 1605 65.5 15.6 1598 66.5 18.1 1589 67.5 18 1581 68.5 18.3 1574 69.5 18 1566 70.5 16.4 1559 71.5 18.1 1552 72.5 14.5 1546 73.5 1540 Lake Malawi Core M98-10MC 9º 58.6'S 34º 13.9'E 364 m water depth Note: The Pb-210 chronology for M98-10MC assumes the core top was 1998. However stratigraphic correlations with M98-11MC indicate that the core top is missing the top ca. 4 cm, or 18 years. The correlation is in layer H1, situated at about 10 cm in 11 MC and at 7.5 cm in 10 MC. "Depth, cm" % Bsi Year AD Pb-210 lin Pb-210 CRS 0.5 18.05 1982 1995 1996 1.5 19.95 1978 1990 1991 2.5 14.34 1972 1984 1986 3.5 11.31 1965 1979 1981 4.5 11.33 1958 1973 1975 5.5 14.91 1951 1966 1967 6.5 14.5 1950 1958 1959 7.5 14.78 1945 1951 1950 8.5 11.43 1938 9.5 11.44 1931 1942 1940 10.5 15.34 1925 11.5 17.06 1916 1935 1930 12.5 15.31 1909 13.5 13.23 1902 1924 1917 14.5 15.58 1896 15.5 11.61 1889 1908 1900 16.5 13.54 1884 17.5 12.66 1878 1893 1883 18.5 10.34 1871 19.5 16.32 1866 1877 1866 20.5 1846 21.5 15.52 1839 22.5 12.8 1832 23.5 14.9 1825 24.5 16.56 1818 25.5 19.9 1811 26.5 22.04 1807 27.5 20.46 1801 28.5 18.27 1794 29.5 26.65 1787 30.5 30.58 1780 31.5 28.82 1778 32.5 28.18 1772 33.5 29 1765 34.5 27.54 1761 35.5 25.47 1757 36.5 22.47 1748 37.5 1739 38.5 1716 39.5 21.53 1708 40.5 22.66 1699 41.5 20.08 1689 42.5 24.48 1683 43.5 24.78 1678 44.5 20.18 1674 45.5 19.11 46.5 17.75 47.5 21.03 Lake Malawi Core M98-11C 10º 00.2'S 34 17.3'E 404 m Water Depth "Depth, cm" % Bsi Year AD Pb-210 yr 0.5 17.95 1997 1996 1.5 17.6 1992 1992 2.5 15.17 1987 1988 3.5 12.74 1981 1984 4.5 10.73 1975 1979 5.5 14.84 1970 1973 6.5 14.83 1965 1967 7.5 14.27 1960 1961 8.5 12.73 1954 1955 9.5 1951 1949 10.5 12.5 1939 11.5 17.8 1934 1939 12.5 19.44 1927 13.5 15.57 1921 1926 14.5 12.7 1912 15.5 14.07 1905 1913 16.5 16.66 1899 17.5 11.25 1892 1901 18.5 14.38 1886 19.5 13.56 1881 1890 20.5 9.55 1875 21.5 13.95 1869 1878 22.5 20.25 1866 23.5 16.78 1837 1866 24.5 15.23 1831 25.5 13.33 1824 1853 26.5 17.31 1817 27.5 14.78 1811 28.5 23.97 1806 29.5 21.74 1802 30.5 23.22 1797 31.5 31.2 1789 32.5 29.38 1782 33.5 32.37 1776 34.5 27.35 1767 35.5 20.17 1759 36.5 28.73 1759 37.5 25.08 1751 38.5 24.9 1743 39.5 16.11 1736 40.5 18.67 1722 41.5 22.32 1713 42.5 19.26 1704 43.5 26.98 1696 44.5 25.35 1688 45.5 16.08 1681 46.5 26.89 1676 47.5 12.55 1674 48.5 15.95 1667 49.5 15.55 1659 50.5 18.51 1655 M98-1PG "Depth, cm" % BSi replicates Year AD 0 17.48 1 16.81 2 19.95 3 27.89 29.1 4 21.85 5 21.11 6 20.06 7 23.04 8 24.15 9 16.84 1674 10 15.15 1670 11 19.3 1665 12 29.93 1659 13 22.25 1652 14 18.74 19.64 1645 15 24.76 1636 16 31.05 1628 17 19.41 1599 18 16.05 1590 19 17.83 1581 20 19.7 18.16 1572 21 21.85 1564 22 14.2 1558 23 23.09 1548 24 24.77 1538 25 19.06 1533 26 17.49 1528 27 22.49 1520 28 1513 29 16.98 1495 30 1488 31 11.92 1484 32 12.58 1473 33 9.46 1462 34 12.48 1453 35 13.12 1445 36 11.17 1437 37 14.76 1430 38 17.8 18.65 1426 39 20.34 1418 40 20.15 1410 41 1403 42 18.1 18.01 1391 43 19.83 1390 44 17.26 1384 45 1376 46 16.68 47 12.1 48 14.55 49 9.12 M98-2PG "Depth, cm" % BSI 5 pt smooth Year AD wt. % water 0 14.77 1886 1 16.98 1882 84.37 2 14.76 15.264 1877 3 13.78 14.524 1873 4 16.03 13.22 1869 5 11.07 13.576 1865 6 10.46 14.02 1861 7 16.54 13.914 1856 8 14.73 1850 9 15.318 1850 10 15.15 15.482 1849 83.76 11 13.4 15.208 1844 12 17.36 16.124 1839 13 14.63 17.694 1834 14 20.08 19.014 1829 15 23 19.184 1822 16 20.802 1815 17 18.21 21.62 1814 18 22.72 23.87 1807 19 24.17 24.568 1801 20 34.25 27.364 1794 84.89 21 23.49 28.33 1787 22 32.19 29.12 1780 23 27.55 27.6 1773 24 28.12 26.484 1765 25 26.65 23.88 1758 26 17.91 21.072 1752 27 19.17 18.52 1746 28 13.51 16.39 1738 29 15.36 16.208 1730 30 16.174 1720 83.45 31 17.686 1720 32 19.938 1720 33 21.07 21.48 1706 34 26.62 23.178 1695 35 23.71 24.808 1687 36 25.49 23.688 1679 37 27.15 21.902 1675 38 15.47 20.774 1672 39 17.69 21.354 1670 40 18.07 20.838 1655 82.45 41 28.39 21.374 1648 42 24.57 22.338 1642 43 18.15 23.588 1637 44 22.51 23.43 1632 45 24.32 23.272 1626 46 27.6 23.614 1618 47 23.78 23.054 1612 48 19.86 22.16 1606 49 19.71 21.424 1600 50 19.85 21.004 1592 81.32 51 23.92 20.362 1586 52 21.68 20.384 1578 53 16.65 20.484 1569 54 19.82 19.262 1559 55 20.35 18.078 1549 56 17.81 18.562 1539 57 15.76 18.48 1527 58 19.07 18.936 1515 59 19.41 17.86 1505 60 22.63 17.228 1498 79.06 61 12.43 15.984 1490 62 14.772 1483 63 12.85 13.048 1479 64 13.35 13.942 1472 65 14.01 14.456 1464 66 16.9 14.578 1456 67 15.17 15.474 1450 68 13.46 16.192 1442 69 17.83 16.676 1434 70 17.6 16.748 1426 80.25 71 19.32 18.246 1420 72 15.53 18.48 1411 73 20.95 18.56 1402 74 18.154 1391 75 17.632 1385 76 17.29 15.942 1382 77 12.92 14.542 1375 78 13.34 1367 79 12.808 1363 80 11.99 12.756 1356 78.53 81 14.63 13.9 1346 82 12.66 15.888 1337 83 18.22 16.626 1329 84 21.94 16.266 1322 85 15.68 16.876 1315 86 12.83 16.69 1308 87 15.71 16.008 1300 88 17.29 16.908 1295 89 18.53 16.666 1287 90 20.18 16.68 1280 76.59 91 11.62 15.996 1273 92 15.78 1266 93 13.87 1258