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Arjen Grothe
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A. Grothe
Paleomagnetic Laboratory
Fort Hoofddijk
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Department of Earth Sciences
Utrecht University
Budapestlaan 17, 3584 CD Utrecht 
The Netherlands 

Phone +31 30 253 1670
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Research of Arjan Grothe

Late Eocene sea retreat from the Tarim Basin (China) and concomitant Asian paleoenvironmental change
Late Cretaceous and Paleogene sediments of the Tarim basin contain the easternmost marine sediments of a large epicontinental sea, later to beecome the Paratethys Sea. The final regression of this sea has been associated with regional tectonics caused by the Indo-Asia collision and glacio-eustatic sea level lowering at the Eocene-Oligocene Transition (EOT; ca. 34 Ma). However, Bosboom et al. (2011) showed that the retreat of the Paratethys from the Tarim Basin seems to be earliest Priabonian in age (~ 37 Ma), thus predating both the glacio-eustatic sea-level fall at the EOT and the Oligocene–Miocene (regional) uplift of the Pamir Shan and Kunlun Shan mountain ranges.
In addition, the sea retreat may have contributed to a strong aridification and cooling of the Asian interior and an intensification of the Asian monsoon system, which have been recorded at the northeastern Tibetan Plateau. So far, the retreat seems to correlate to a significant aridification step at 36.6 Ma in the Xining Basin.
However, the timing of the Paratethys sea retreat remains poorly understood, which prevents a good understanding of its cause and environmental impacts. 

Tarim basin, along the Aertashi section

To improve the understanding of the cause and effect of the regression with respect to regional and global climate, an in-depth study which provides high-resolution data of the marine history of the Tarim Basin is required. Therefore a fieldwork was carried out in the summer of 2010, under supervision of Guillaume Dupont-Nivet and accompanied by Roderic Bosboom, Huang Wentao. Accordingly, the aim of this project is to accurately determine the timing and impact of the Paratethys retreat out of the Tarim Basin (figure above) by studying key sedimentary successions, which have recorded this event.
For dating and correlation of the shallow marine sections in the Tarim Basin, a marine palynological approach is required, particularly by studying dinoflagellates (dinocysts), which is supervised by Henk Brinkhuis. The dinocysts provide a strong tool for reconstructing the paleogeography and environmental conditions (e.g. temperature and salinity) at the time of deposition. In addition to the biostratigraphic approach,  magnetostratigraphy will be used as another tool for the construction of a chronological framework (by Roderic Bosboom). 

Heavily weathered red beds of the Bashibulak Formation, alternated by greyish-green 
marine beds. In the back: resistant limestones of the Kalatar Formation.

Additionally, quantitative constraints on temperature can be obtained through the application of organic geochemical proxies, such as TEX86, MBT/CBT which respectively yield Sea Surface Temperatures (SSTs) and Mean Annual Air Temperature (MAAT). A pilot study will be performed to test the potential for organic paleothermometry in this region. 

This project is a cooperation of the Paleomagnetic Laboratory and Biomarine Sciences Group, both from Utrecht University. Supervision will be performed by Prof. dr Henk Brinkhuis, Sander Houben (both Biomarine Sciences, LPP), dr. Guillaume Dupont-Nivet and Roderic Bosboom (both Paleomagnetic Laboratory). The field campaign has been sponsored by the Molengraaff Foundation.

publications Publications of Arjen Grothe