Gebregiorgis, Daniel; Deocampo, Daniel M; Longstaffe, Fred J; Simpson, Alexandra M; Ashley, Gail M; Beverly, Emily J; Delaney, Jeremy S; Cuadros, Javier (2020): Relative proportions of smectite and illite, and illite-smectite oxygen-isotope compositions (δ18OI-S) of 39 mudstone samples collected from a lacustrian section at Paleolake Olduvai. PANGAEA, https://doi.org/10.1594/PANGAEA.910866
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Most clay minerals in sedimentary environments have traditionally been considered to be of detrital origin, but under certain conditions, authigenic clay minerals can form at low temperature through the transformation of precursor clays or as direct precipitates from lake-water. Such clay minerals can hold important information about the prevailing climatic conditions during the time of deposition. We present the first quantitative reconstruction of salinity in paleolake Olduvai based on the oxygen-isotope composition of authigenic clay minerals. We provide a framework illustrating that the isotopic signature of authigenic lacustrine clay minerals is related to the isotopic composition of paleo-waters, and hence to paleosalinity. This new paleosalinity proxy shows that the early Pleistocene East African monsoon was driven by combinations of precession and obliquity forcing, and subsequent changes in tropical SSTs. Such quantitative lacustrine paleosalinity estimates provides a new direction of research for modeling ecosystem change based on an ecologically relevant parameter.
Gebregiorgis, Daniel; Deocampo, Daniel M; Longstaffe, Fred J; Simpson, Alexandra M; Ashley, Gail M; Beverly, Emily J; Delaney, Jeremy S; Cuadros, Javier (2020): Oxygen Isotopes in Authigenic Clay Minerals: Toward Building a Reliable Salinity Proxy. Geophysical Research Letters, 47(3), e2019GL085576, https://doi.org/10.1029/2019GL085576
Latitude: -2.963083 * Longitude: 35.313583
Date/Time Start: 1999-07-01T00:00:00 * Date/Time End: 1999-07-01T00:00:00
|#||Name||Short Name||Unit||Principal Investigator||Method/Device||Comment|
|1||Sample ID||Sample ID||Gebregiorgis, Daniel||Standard sample identification numbers (Deocampo et al., 2017, Geology; Gebregiorgis et al., 2020; GRL)|
|2||Age model||Age model||ka||Gebregiorgis, Daniel||Estimated ages for 39 mudstone samples from a lacustrian section collected from Paleolake Olduvai|
|3||Illite||Ill||%||Gebregiorgis, Daniel||Illite percentages determined based on glycolated XRD patterns (See Gebregiorgis et al., 2020, GRL and references therein).|
|4||Smectite||Sme||%||Gebregiorgis, Daniel||Smectite percentages determined based on glycolated XRD patterns (See Gebregiorgis et al., 2020, GRL and references therein).|
|5||δ18O, illite-smectite||δ18O Ill-Sme||‰ SMOW||Gebregiorgis, Daniel||illite-smectite oxygen-isotope compositions (δ18OI-S) (VSMOW)|
195 data points