Oxygen and Carbon Stable Isotope Composition of Cretaceous to Pliocene Calcareous Paleosols in the Tian Shan Region (Central Asia): Controlling Factors and Paleogeographic Implications

Marc Jolivet (1) , Philippe Boulvais (1) , Laurie Barrier (2) , Cécile Robin (1) , Gloria Heilbronn (3) , Julie Ledoyen (1) , Quentin Ventroux (1) , Yingying Jia (4) , Zhaojie Guo (5) , Elena A Bataleva (6)

1 GR - Géosciences Rennes
2 IPGP - Institut de Physique du Globe de Paris
3 CASP - Cambridge Arctic Shelf Programme
4 UCAS - University of Chinese Academy of Sciences [Beijing]
5 Key Laboratory of Orogenic Belts and Crustal Evolution
6 Research Station of the Russian Academy of Sciences

The Late Mesozoic–Cenozoic topographic and climate evolution of Central Asia remains highly debated. The final retreat of the proto-Paratethys Sea from the western Tarim Basin is thought to correspond in time with the onset of tectonic uplift in the Pamir, Tian Shan and Altai ranges, as well as with regional aridification. The oxygen and carbon isotope compositions of the sediment deposits in the various Central Asian basins have already been used to decipher both the topographic and climatic changes that occurred in that region during the Cenozoic, generally concentrating on one sedimentary section and/or on a limited time range and either using multiple-type samples including sandstone calcitic cements, marine carbonates, fossils, or paleosols. In order to get a homogeneous dataset, minimizing variations in the isotopic composition of the material depending on its type and/or depositional environment, we selected only calcareous paleosols sampled in several continuous sections covering a wide time range from the Late Jurassic to the Pliocene. Our sampling also covers a wide area encompassing the whole Tian Shan region, which allows detecting regional variations in the δ 18 O and δ 13 C values. We show that the influence of the distance to the proto-Paratethys Sea on the paleosol δ 18 O record was not significant. Besides local factors such as the occurrence of large lakes that can have a significant effect on the isotopic composition of the calcareous paleosols, the long-term evolution of both the δ 18 O and δ 13 C values possibly reflects the hypsometry of the river drainage systems that bring water to the basins. However, as it is commonly accepted that the δ 18 O of soil carbonates is controlled by the δ 18 O of in-situ precipitation, this last conclusion remains to be further investigated.

Mots clés: Central Asia; late Mesozoic–Cenozoic climate; calcareous paleosols; hypsometry

Domaines: Géochimie; Climatologie

Marc Jolivet, Philippe Boulvais, Laurie Barrier, Cécile Robin, Gloria Heilbronn, et al.. Oxygen and Carbon Stable Isotope Composition of Cretaceous to Pliocene Calcareous Paleosols in the Tian Shan Region (Central Asia): Controlling Factors and Paleogeographic Implications. Geosciences, 2018, 8 (9), pp.330. ⟨10.3390/geosciences8090330⟩. ⟨insu-01866759⟩