Stepwise onset of the Icehouse world and its impact on Oligo-Miocene Central Asian mammals.

Mathias Harzhauser,Ursula B Göhlich,Werner E Piller,Margarita A Erbajeva,Paloma López-Guerrero,Olivier Maridet,Sylvain Richoz,Gudrun Daxner-Höck,Thomas A Neubauer,Adriana Oliver

doi:10.1038/srep36169

Abstract

Central Asia is a key area to study the impact of Cenozoic climate cooling on continental ecosystems. One of the best places to search for rather continuous paleontological records is the Valley of Lakes in Mongolia with its outstandingly fossil-rich Oligocene and Miocene terrestrial sediments. Here, we investigate the response by mammal communities during the early stage of Earth’s icehouse climate in Central Asia. Based on statistical analyses of occurrence and abundance data of 18608 specimens representing 175 mammal species and geochemical (carbon isotopes) and geophysical (magnetic susceptibility) data we link shifts in diversities with major climatic variations. Our data document for the first time that the post-Eocene aridification of Central Asia happened in several steps, was interrupted by short episodes of increased precipitation, and was not a gradual process. We show that the timing of the major turnovers in Oligocene mammal communities is tightly linked with global climate events rather than slow tectonics processes. The most severe decline of up 48% of total diversity is related to aridification during the maximum of the Late Oligocene Warming at 25 Ma. Its magnitude was distinctly larger than the community turnover linked to the mid-Oligocene Glacial Maximum.

Highlights

The Tertiary terrestrial deposits of the Valley of Lakes in Mongolia (Fig. 1) are outstanding concerning their rich fossil record and the vast outcrops (Fig. 2)
The Oligocene and lower Miocene deposits are united in the Hsanda Gol Formation (HGF) and the Loh Formation (LF)
A total of 175 species-level taxa are recorded in the Oligocene and lower Miocene samples

Summary

Introduction

The Tertiary terrestrial deposits of the Valley of Lakes in Mongolia (Fig. 1) are outstanding concerning their rich fossil record and the vast outcrops (Fig. 2) This fact makes the area a main target to study the development of continental faunas of Central Asia. Geodynamic events may have played an additional important role for the development of the Oligocene Glacial Maximum (OGM) This cool phase was followed by the global Late Oligocene Warming (LOW), which was interrupted only by the minor isotope event Oi2c. The Oligocene and lower Miocene deposits are united in the Hsanda Gol Formation (HGF) and the Loh Formation (LF) Both are widely exposed in the Taatsiin Gol Basin and extraordinarily rich in fossil mammals (Fig. 2). The upper Oligocene to Miocene Loh Formation is partly interfingering with the HGF and lithologically more diversified It exposes brownish-reddish to greyish clay and silt with caliche layers. An absolute dating of our sections based on intercalated flood basalts[28] and magnetostratigraphic dating[7] allow a precise correlation with the marine record

Methods

Results

Discussion

Conclusion