TY  - JOUR
A1  - Sier, Mark J.
A1  - Langereis, Cor G.
A1  - Dupont-Nivet, Guillaume
A1  - Feibel, Craig S.
A1  - Joordens, Josephine C. A.
A1  - van der Lubbe, Jeroen Fiji.
A1  - Beck, Catherine C.
A1  - Olago, Daniel
A1  - Cohen, Andrew
T1  - The top of the Olduvai Subchron in a high-resolution magnetostratigraphy from the West Turkana core WTK13, hominin sites and Paleolakes Drilling Project (HSPDP)
JF  - Quaternary geochronology : the international research and review journal on advances in quaternary dating techniques
N2  - One of the major challenges in understanding the evolution of our own species is identifying the role climate change has played in the evolution of hominin species. To clarify the influence of climate, we need long and continuous high-resolution paleoclimate records, preferably obtained from hominin-bearing sediments, that are well-dated by tephro- and magnetostratigraphy and other methods. This is hindered, however, by the fact that fossil-bearing outcrop sediments are often discontinuous, and subject to weathering, which may lead to oxidation and remagnetization. To obtain fresh, unweathered sediments, the Hominin Sites and Paleolakes Drilling Project (HSPDP) collected a ∼216-meter core (WTK13) in 2013 from Early Pleistocene Paleolake Lorenyang deposits in the western Turkana Basin (Kenya). Here, we present the magnetostratigraphy of the WTK13 core, providing a first age model for upcoming HSPDP paleoclimate and paleoenvrionmental studies on the core sediments. Rock magnetic analyses reveal the presence of iron sulfides carrying the remanent magnetizations. To recover polarity orientation from the near-equatorial WTK13 core drilled at 5°N, we developed and successfully applied two independent drill-core reorientation methods taking advantage of (1) the sedimentary fabric as expressed in the Anisotropy of Magnetic Susceptibility (AMS) and (2) the occurrence of a viscous component oriented in the present day field. The reoriented directions reveal a normal to reversed polarity reversal identified as the top of the Olduvai Subchron. From this excellent record, we find no evidence for the ‘Vrica Subchron’ previously reported in the area. We suggest that outcrop-based interpretations supporting the presence of the Vrica Subchron have been affected by the oxidation of iron sulfides initially present in the sediments -as evident in the core record- and by subsequent remagnetization. We discuss the implications of the observed geomagnetic record for human evolution studies.
KW  - Paleolake Lorenyang
KW  - Magnetostratigraphy
KW  - Olduvai Subchron
KW  - Vrica Subchron
KW  - Drill-core reorientation
KW  - ICDP
KW  - Paleoclimate
KW  - Hominin evolution
Y1  - 2017
U6  - https://doi.org/10.1016/j.quageo.2017.08.004
SN  - 1871-1014
SN  - 1878-0350
VL  - 42
SP  - 117
EP  - 129
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Huang, Wentao
A1  - van Hinsbergen, Douwe J. J.
A1  - Dekkers, Mark J.
A1  - Garzanti, Eduardo
A1  - Dupont-Nivet, Guillaume
A1  - Lippert, Peter C.
A1  - Li, Xiaochun
A1  - Maffione, Marco
A1  - Langereis, Cor G.
A1  - Hu, Xiumian
A1  - Guo, Zhaojie
A1  - Kapp, Paul
T1  - Paleolatitudes of the Tibetan Himalaya from primary and secondary magnetizations of Jurassic to Lower Cretaceous sedimentary rocks
JF  - Geochemistry, geophysics, geosystems
N2  - The Tibetan Himalaya represents the northernmost continental unit of the Indian plate that collided with Asia in the Cenozoic. Paleomagnetic studies on the Tibetan Himalaya can help constrain the dimension and paleogeography of "Greater India,' the Indian plate lithosphere that subducted and underthrusted below Asia after initial collision. Here we present a paleomagnetic investigation of a Jurassic (limestones) and Lower Cretaceous (volcaniclastic sandstones) section of the Tibetan Himalaya. The limestones yielded positive fold test, showing a prefolding origin of the isolated remanent magnetizations. Detailed paleomagnetic analyses, rock magnetic tests, end-member modeling of acquisition curves of isothermal remanent magnetization, and petrographic investigation reveal that the magnetic carrier of the Jurassic limestones is authigenic magnetite, whereas the dominant magnetic carrier of the Lower Cretaceous volcaniclastic sandstones is detrital magnetite. Our observations lead us to conclude that the Jurassic limestones record a prefolding remagnetization, whereas the Lower Cretaceous volcaniclastic sandstones retain a primary remanence. The volcaniclastic sandstones yield an Early Cretaceous paleolatitude of 55.5 degrees S [52.5 degrees S, 58.6 degrees S] for the Tibetan Himalaya, suggesting it was part of the Indian continent at that time. The size of "Greater India' during Jurassic time cannot be estimated from these limestones. Instead, a paleolatitude of the Tibetan Himalaya of 23.8 degrees S [21.8 degrees S, 26.1 degrees S] during the remagnetization process is suggested. It is likely that the remagnetization, caused by the oxidation of early diagenetic pyrite to magnetite, was induced during 103-83 or 77-67 Ma. The inferred paleolatitudes at these two time intervals imply very different tectonic consequences for the Tibetan Himalaya.
Y1  - 2015
U6  - https://doi.org/10.1002/2014GC005624
SN  - 1525-2027
VL  - 16
IS  - 1
SP  - 77
EP  - 100
PB  - American Geophysical Union
CY  - Washington
ER  -