Abstract

The Taatsiin Gol Basin in Mongolia is a key area for understanding the evolution and dispersal of Central Asian mammal faunas during the Oligocene and early Miocene. After two decades of intense fieldwork, the area is extraordinarily well sampled and taxonomically well studied, yielding a large dataset of 19,042 specimens from 60 samples. The specimens represent 176 species-level and 99 genus-level taxa comprising 135 small mammal species and 47 large mammals. A detailed lithostratigraphy and new magnetostratigraphic and radiometric datings provide an excellent frame for these biotic data. Therefore, we test and evaluate the informal biozonation scheme that has been traditionally used for biostratigraphic correlations within the basin. Based on the analysis of the huge dataset, a formalised biostratigraphic scheme is proposed. It comprises the Cricetops dormitor Taxon Range Zone (Rupelian), subdivided into the Allosminthus khandae Taxon Range Subzone and the Huangomys frequens Abundance Subzone, the Amphechinus taatsiingolensis Abundance Zone (early Chattian), the Amphechinus major Taxon Range Zone (late Chattian), subdivided into the Yindirtemys deflexus Abundance Subzone and the Upper Amphechinus major T. R. Z., and the Tachyoryctoides kokonorensis Taxon Range Zone (Aquitanian). In statistical analyses, samples attributed to these biozones form distinct clusters, indicating that each biozone was also characterised by a distinct faunal type.

Highlights

  • The Oligocene and Miocene terrestrial deposits of the Valley of Lakes in Mongolia are outstanding regarding the rich and stratigraphically dense successions of mammal assemblages

  • We evaluate which species are significant and frequent enough to be detected in samples of a certain biozone

  • The sampling method clearly focused on small mammals, and larger mammals might be underrepresented, despite their high palaeoecological significance

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Summary

Introduction

The Oligocene and Miocene terrestrial deposits of the Valley of Lakes in Mongolia are outstanding regarding the rich and stratigraphically dense successions of mammal assemblages. An informal biozonation scheme for Oligocene and Miocene mammal assemblages of the Valley of Lakes was proposed as a biostratigraphic tool (Daxner-Höck et al 1997). This zonation scheme was subsequently refined by Daxner-Höck (2001) and Daxner-Höck et al (2010, 2013, 2014). It is based on characteristic assemblages and co-occurrences of taxa and might best be considered as assemblage-zones. They proved to be highly valuable during fieldwork and enabled detecting depositional gaps in the often very uniform lithologies

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