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

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.

Oligocene and early Miocene mammal biostratigraphy of the Valley of Lakes in Mongolia

“…The samples of the Aquitanian Tachyoryctoides kokonorensis Zone follow this overall (stratigraphic) trend but are more separated, indicating another turnover at the Oligocene/Miocene boundary. These punctuations are most probably the result of climate forcing and corresponding changes in palaeoenvironments (Harzhauser et al 2016). A detailed reconstruction of the palaeoenvironments is beyond the scope of this paper, but some general conclusions can be drawn:

Rupelian ( Cricetops dormitor Taxon Range Zone): the high diversities and similar contributions by Palaeolagidae, Dipodidae, Cricetidae and Erinacidae (Fig.

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Diversification rates in Ctenodactylidae (Rodentia, Mammalia) from Mongolia

“…; late Oligocene). We assume that the observed changes of ctenodactylid compositions are linked with the climatic instability in the course of the late Oligocene, called the Late Oligocene Extinction Event (Harzhauser et al 2016). …”

“…), called the Mid-Oligocene Reorganization (Harzhauser et al 2016), coinciding with the Oligocene Glacial Maximum. This significant climatic change forced two effects in the ctenodactylid assemblages.…”

“…4), defined as the Late Oligocene Extinction Event (Harzhauser et al 2016), in which both Tataromys species and Y. birgeri went extinct. The genus Yindirtemys acted as a transitional component, being the only representative of the highly impoverished ctenodactylid faunas at the end of the late Oligocene.…”

Introduction to the special issue “The Valley of Lakes in Mongolia, a key area of Cenozoic mammal evolution and stratigraphy”

“…The fieldwork was carried out by changing teams of Mongolian and European members. This work in Mongolia led to important results and subsequent publications, including an integrated stratigraphy based on Oligocene-Miocene sediment, basalt and fossil associations (Daxner-Höck et al 1997Höck et al 1999), a reconstruction of climatic changes (Harzhauser et al 2016) and taxonomic studies performed on different fossil groups: Gastropoda (Stworzewicz 2007;Neubauer et al 2013), lower vertebrates (Böhme 2007), small mammals (Daxner-Höck 2000, 2001Daxner-Höck and Wu 2003;Erbajeva 2007Erbajeva , 2013Schmidt-Kittler et al 2007;Ziegler et al 2007;Erbajeva and Daxner-Höck 2014;Wessels et al 2014;Daxner-Höck et al 2013Maridet et al 2014aMaridet et al , b, 2015 and large mammals (Vislobokova and DaxnerHöck 2002;Morlo and Nagel 2002, 2006Nagel and Morlo 2003;Göhlich 2007;Heissig 2007). The enamel microstructure of Paleogene and early Neogene rodent teeth from Mongolia was analysed by Koenigswald and Kalthoff (2007).…”