TY  - JOUR
A1  - Engelhardt, Jonathan Franz
A1  - Sudo, Masafumi
A1  - Stockhecke, Mona
A1  - Oberhaensli, Roland
T1  - Feldspar Ar-40/(39) Ar dating of ICDP PALEOVAN cores
JF  - Geochimica et cosmochimica acta : journal of the Geochemical Society and the Meteoritical Society
N2  - Eleven inverse isochron ages from total fusion and three from stepwise heating analyses fit the age model. Four experiments resulted in older inverse isochron ages that do not concur with the model within 2 sigma uncertainties and that deviate from 1 ka to 17 ka minimum. C-and R-type zoning are interpreted as representing growth in magma chamber cupolas, as wall mushes, or in narrow conduits. Persistent compositions of PO-type crystals and abundant surfaces recording dissolution features correspond to formation within a magma chamber. C-type zoning and R-type zoning have revealed an irregular incorporation of melt and fluid inclusions. These two types of zoning in feldspar are interpreted as preferentially contributing either heterogeneously distributed excess Ar-40 or inherited Ar-40 to the deviating Ar-40/Ar-39 ages that are discussed in this study. (C) 2017 Elsevier Ltd. All rights reserved.
KW  - Lake Van
KW  - Feldspar zoning
KW  - Lacustrine record
KW  - Volcaniclastics
Y1  - 2017
U6  - https://doi.org/10.1016/j.gca.2017.07.039
SN  - 0016-7037
SN  - 1872-9533
VL  - 217
SP  - 144
EP  - 170
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Foerster, Verena
A1  - Asrat, Asfawossen
A1  - Ramsey, Christopher Bronk
A1  - Brown, Erik T.
A1  - Chapot, Melissa S.
A1  - Deino, Alan
A1  - Düsing, Walter
A1  - Grove, Matthew
A1  - Hahn, Annette
A1  - Junginger, Annett
A1  - Kaboth-Bahr, Stefanie
A1  - Lane, Christine S.
A1  - Opitz, Stephan
A1  - Noren, Anders
A1  - Roberts, Helen M.
A1  - Stockhecke, Mona
A1  - Tiedemann, Ralph
A1  - Vidal, Celine M.
A1  - Vogelsang, Ralf
A1  - Cohen, Andrew S.
A1  - Lamb, Henry F.
A1  - Schaebitz, Frank
A1  - Trauth, Martin H.
T1  - Pleistocene climate variability in eastern Africa influenced hominin evolution
JF  - Nature geoscience
N2  - Despite more than half a century of hominin fossil discoveries in eastern Africa, the regional environmental context of hominin evolution and dispersal is not well established due to the lack of continuous palaeoenvironmental records from one of the proven habitats of early human populations, particularly for the Pleistocene epoch. Here we present a 620,000-year environmental record from Chew Bahir, southern Ethiopia, which is proximal to key fossil sites. Our record documents the potential influence of different episodes of climatic variability on hominin biological and cultural transformation. The appearance of high anatomical diversity in hominin groups coincides with long-lasting and relatively stable humid conditions from similar to 620,000 to 275,000 years bp (episodes 1-6), interrupted by several abrupt and extreme hydroclimate perturbations. A pattern of pronounced climatic cyclicity transformed habitats during episodes 7-9 (similar to 275,000-60,000 years bp), a crucial phase encompassing the gradual transition from Acheulean to Middle Stone Age technologies, the emergence of Homo sapiens in eastern Africa and key human social and cultural innovations. Those accumulative innovations plus the alignment of humid pulses between northeastern Africa and the eastern Mediterranean during high-frequency climate oscillations of episodes 10-12 (similar to 60,000-10,000 years bp) could have facilitated the global dispersal of H. sapiens.
KW  - Evolutionary ecology
KW  - Limnology
KW  - Palaeoclimate
Y1  - 2022
U6  - https://doi.org/10.1038/s41561-022-01032-y
SN  - 1752-0894
SN  - 1752-0908
VL  - 15
IS  - 10
SP  - 805
EP  - 811
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Glombitza, Clemens
A1  - Stockhecke, Mona
A1  - Schubert, Carsten J.
A1  - Vetter, Alexandra
A1  - Kallmeyer, Jens
T1  - Sulfate reduction controlled by organic matter availability in deep sediment cores from the saline, alkaline Lake Van (Eastern Anatolia,Turkey)
JF  - Frontiers in microbiology
N2  - As part of the International Continental Drilling Program deep lake drilling project Paleo Van, we investigated sulfate reduction (SR) in deep sediment cores of the saline, alkaline (salinity 21.4%0, alkalinity 155 m mEq-1, pH 9.81) Lake Van, Turkey. The cores were retrieved in the Northern Basin (NB) and at Ahlat Ridge (AR) and reached a maximum depth of 220 m. Additionally, 65-75 cm long gravity cores were taken at both sites. SR rates (SRR) were low (<22 nmol cm-3 day-1) compared to lakes with higher salinity and alkalinity, indicating that salinity and alkalinity are not limiting SR in Lake Van. Both sites differ significantly in rates and depth distribution of SR. In NB, SRR are up to 10 times higher than at AR. SR could be detected down to 19 mblf (meters below lake floor) at NB and down to 13 mblf at AR. Although SRR were lower at AR than at NB, organic matter (OM) concentrations were higher. In contrast, dissolved OM in the pore water at AR contained more macromolecular OM and less low molecular weight OM.VVe thus suggest, that OM content alone cannot be used to infer microbial activity at Lake Van but that quality of OM has an important impact as well. These differences suggest that biogeochemical processes in lacustrine sediments are reacting very sensitively to small variations in geological, physical, or chemical parameters over relatively short distances.
KW  - saline lake
KW  - alkaline lake
KW  - sulfate reduction
KW  - deep biosphere
KW  - organic matter
Y1  - 2013
U6  - https://doi.org/10.3389/fmicb.2013.00209
SN  - 1664-302X
VL  - 4
IS  - 28
PB  - Frontiers Research Foundation
CY  - Lausanne
ER  -