Evaluation of ostracod-based palaeoenvironmental reconstruction with instrumental data from the arid Faiyum Depression,Egypt |
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| Authors: | K W Keatings I Hawkes J A Holmes R J Flower M J Leng R H Abu-Zied A R Lord |
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| Institution: | 1.Environmental Change Research Centre,University College London,London,UK;2.Department of Geography,Lancaster University,Lancaster,UK;3.NERC Isotope Geosciences Laboratory,British Geological Survey,Nottingham,UK;4.School of Geography,University of Nottingham,Nottingham,UK;5.Geology Department, Faculty of Science,Mansoura University,El-Mansoura,Egypt;6.Sektion Mikropal?ontologie I,Forschungsinstitut Senckenberg,Frankfurt Am Main,Germany |
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| Abstract: | The utility of ostracod-based palaeoenvironmental reconstruction was evaluated using instrumental data for Lake Qarun, Egypt.
The euryhaline ostracod Cyprideis torosa was the only species found in the lake’s recent sediment record. This species is known to tolerate salinity levels and water
solute compositions that may prevent colonisation by other species. Oxygen and carbon isotope ratios of ostracod carbonate
from lake sediments covary with changes in instrumental values for lake level and salinity for the period 1890–1974. δ13C-values correlate negatively with lake water salinity (r
2 = 0.87) and δ18O-values correlate negatively with measured lake level changes (r
2 = 0.41). Other ostracod proxy data provide qualitative information on lake level trends. Fossil assemblage data (juvenile/adult
and valve/carapace ratios and valve preservation) provide information on wave energy. Ecophenotypic variation of C. torosa valves provided some useful palaeolimnological information. Sr/Ca and Mg/Ca ratios in ostracods were not found to reflect
water composition, due to the uncoupling of these ratios with salinity in Lake Qarun. Overall, our results highlight the need
to calibrate ostracod proxy data in modern systems prior to their use for palaeoenvironmental reconstruction. |
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| Keywords: | Ostracod valve chemistry Saline lakes Cyprideis torosa Stable isotope Sieve pores Lake Qarun |
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