Abstract
The sediments from Lake Bosumtwi, Ghana contain a unique record of fine-scale (mm to sub-mm) laminations, which will provide a valuable annual chronometer for reconstructing paleoenvironmental changes in West Africa covering much of the last 1 Ma. Comparisons of laminae counts to independent 210Pb dates and the rise in anthropogenic “bomb” radiocarbon support the interpretation of the laminations in the uppermost sediments as registering annual events. Radiocarbon dates on in-situ fish-bone collagen are in agreement with varve counts, further supporting the annual nature of our varve chronology. Over the instrumental period (1925–1999), dark-varve thickness measurements are correlated with local rainfall (r = 0.54) and appear able to resolve decadal-scale changes in precipitation. The relationship between varve thickness and rainfall provides support for our interpretation that dark-colored varve thickness records catchment runoff during the rainy season rather than dust flux during the dry season. Dark laminae alternate with organic and carbonate-rich light laminae formed during the fall period of enhanced productivity. Downcore, varves undergo significant microstratigraphic and geochemical variations, but retain the same pattern of alternating clastic and organic-rich laminae, providing support that the laminae may represent annual time markers for reconstructions of the deeper part of the record.
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References
Almond J, Hecky R (2001) Water column properties of Lake Bosumtwi, Ghana
Appleby PG, Oldfield F, Thompson R, Huttunen P, Tolonen K (1979) 210Pb dating of annually laminated sediments from Finland. Nature 280:53–55
Beuning KRM, Talbot MR, Livingstone DA, Schmukler G (2003) Sensitivity of carbon isotopic proxies to paleoclimatic forcing: a case study from Lake Bosumtwi, Ghana, over the last 32,000 years. Global Biogeochem Cy 17(4):1121
Chaing JCH, Biasutti M, Battisti DS (2003) Sensitivity of the Atlantic intertropical convergence zone to last glacial maximum boundary conditions. Paleoceanography 18:1094
Dai KM, Fan CY (1986) Bomb produced 14C content in tree rings grown at different latitudes. Radiocarbon 28:346–349
Dai KM, Qian Y, Fan CY (1992) Bomb-produced 14C in tree rings. Radiocarbon 34:753–756
Dean JM, Kemp AES, Bull D, Pike J, Patterson G, Zolitschka B (1999) Taking varves to bits: scanning electron microscopy in the study of laminated sediments and varves. J Paleolimnol 22:121–136
Devries HL, Barendsen GW (1954) Measurements of age by the Carbon-14 technique. Nature 174:1138–1141
Dibb JE, Talbot RW, Gregory GL (1992) Beryllium 7 and Lead 210 in the western hemisphere arctic atmosphere: Observations from three recent aircraft-based sampling programs. J Geophys Res 97:16,709–16,715
Eakins JD, Morrison RT (1978) New procedure for determination of Pb-210 in Lake and Marine-sediments. Int J Appl Radiation Isotopes 29:531–536
Hughen KA, Overpeck JT, Anderson RF, Williams KM (1996) The potential for paleoclimate records from varved Arctic lake sediments: Baffin Island, Eastern Canadian Arctic. In: Kemp AES (ed) Palaeoclimatology and Palaeoceanography from Laminated Sediments. Geological Society Special Publication, pp 57–71
Hulme M (1992) Rainfall changes in Africa: 1931–1960 to 1961–1990. Int J Climatol 12:685–699
Johnson TC (2001) Decadal record of climate variability spanning the past 700 years uin the Southern Tropics of East Africa. Geology 29:83–86
Koeberl C, Reimold WU, Blum JD, Chamberlain CP (1998) Petrology and geochemistry of target rocks from the Bosumtw impact structure, Ghana and comparison with Ivory Coast tektites. Geochimica Cosmochimica Acta 62:2179–2196
Maley J (1991) The African Rain Forest vegetation and paleoenvironments during the late Quaternary. Climatic Change 19:79–98
Nicholson SE (1993) An overview of african rainfall fluctuations over the last decade. J Climate 6:1463–1466
Peck JA, Green RR, Shanahan T, King JW, Overpeck JT, Scholz CA (2004) A magnetic mineral record of Late Quaternary tropical climate variability from Lake Bosumtwi, Ghana. Palaeogeogr Palaeoclimatol Palaeoecol 215:37–57
Peck JA, Heil C, king JW, Scholz CA, Shanahan TM, Overpeck JT, Fox PA, Amoako PY, Forman SL, Koeberl C, Milkereit B (2005) The Lake Bosumtwi Drilling Project: A 1Ma West African Paleoclimate Record. American Geophysical Union Fall Meeting, San Francisco
Pike J, Kemp AES (1996) Preparation and analysis techniques for studies of laminated sediments. In: Kemp AES (ed) Palaeoclimatology and Palaeoceanography from Laminated Sediments. Geological Society Special Publication
Russell J, Talbot MR, Haskell BJ (2003) Mid-holocene climate change in Lake Bosumtwi, Ghana. Quaternary Res 60:133–141
Shanahan TM, Overpeck JT, Sholz C, Sharpe E, Arko J (2007) Simulating the response of a closed basin lake to recent climate changes in tropical West Africa (Lake Bosumtwi, Ghana). Hydrol Processes 21:1678–1691
Shanahan TM, Overpeck JT, Wheeler CW, Beek JW, Pigati JS, Talbot MR, Scholz CA, Peck J, King JW (2006) Paleoclimatic variations in West Africa from a record of late Pleistocene and Holocene lake level stands of Lake Bosumtwi, Ghana. Palaeogeogr Palaeoclimatol Palaeoecol 242:287–302
Street-Perrott FA, Perrott RA (1990) Abrupt climate fluctuations in the tropics: the influence of Atlantic Ocean circulation. Nature 343:607–612
Stuiver M, Reimer PJ (1993) Extended 14C database and revised CALIB radiocarbon calibration program. Radiocarbon 35:215–230
Stuiver M, Reimer PJ, Bard E, Beck JW, Burr GS, Hughen KA, Kromer B, McCormac G, Van der Plicht J, Spurk M (1998) NTCAL98 radiocarbon age calibration, 24,000-0 cal BP. Radiocarbon 40:1041–1083
Talbot MR, Delibrias G (1980) A new late-Holocene water-level curve for Lake Bosumtwi, Ghana. Earth Planetary Sci Lett 47:336–344
Talbot MR, Johannessen T (1992) A high resolution paleoclimatic record for the last 27,000 years in tropical West Africa from the carbon and nitrogen isotopic composition of lacustrine organic matter. Earth Planetary Sci Lett 110:23–37
Talbot MR, Livingstone DA, Palmer PG, Maley J, Melack JM, Delibrias G, Gulliksen S (1984) Preliminary results from sediment cores from Lake Bosumtwi, Ghana. Paleoecol Africa 16:173–192
Tauber H (1967) Copenhagen radiocarbon measurements.8. Geographic Variations in Atmospheric C14 Activity. Radiocarbon 9:246–256
Thompson LG, Mosley-Thompson E, Davis ME, Henderson KA, Brecher HH, Zagorodnov VS, Mashiotta TA, Lin PN, Mikhalenko VN, Hardy DR, Beer J (2002) Kilimanjaro ice core records: evidence of holocene climate change in tropical Africa. Science 298:589–593
Turner BF, Gardner LR, Sharp WE (1996a) The hydrology of Lake Bosumtwi, a climate-sensitive lake in Ghana, West Africa. J Hydrol 183:243–261
Turner BF, Gardner LR, Sharp WE, Blood ER (1996b) The geochemistry of Lake Bosumtwi, a hydrologicaly closed basin in the humid zone of tropical Ghana. Limnol Oceanogr 41:1415–1424
Verschuren D, Laird K, Cumming B (2000) Rainfall and drought in equatorial east Africa during the past 1,100 years. Nature 403:410–414
Wright HE (1980) Cores of soft lake sediments. Boreas 9:107–114
Acknowledgements
This work was funded through NSF Earth System History grants awarded to JTO, JWB, CAS and JK. TMS was partly funded by an NSF-IGERT traineeship in geoarchaeology during this work.
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Shanahan, T.M., Overpeck, J.T., Beck, J.W. et al. The formation of biogeochemical laminations in Lake Bosumtwi, Ghana, and their usefulness as indicators of past environmental changes. J Paleolimnol 40, 339–355 (2008). https://doi.org/10.1007/s10933-007-9164-4
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DOI: https://doi.org/10.1007/s10933-007-9164-4