The Hushoot Shiveetiin gol section (Baruunhuurai Terrane, Mongolia): sedimentology and facies from a Late Devonian island arc setting

S. K. Carmichael,S. Gonchigdorj,A. Nazik,P. Königshof,O. Paschall,A. Yarinpil,A. Dombrowski,C. Crônier,J. A. Waters,A. Munkhjargal,S. Hartenfels,U. Jansen

doi:10.1007/s12549-020-00445-0

Abstract

A Late Devonian to (?)Early Mississippian section at Hushoot Shiveetiin gol in the Baruunhuurai Terrane of the Central Asian Orogenic Belt (CAOB) exposes large parts of cyclic Famennian shallow-water siliciclastic shelf deposits composed of siltstones, sandstones, shales, volcaniclastics, and intercalated autochthonous carbonates. The youngest part of the section, possibly Early Mississippian, is represented by arkosic sandstones with large plant remains. The facies reflects a range from shallow-intertidal to outer ramp settings. In terms of conodont stratigraphy, the Hushoot Shiveetiin gol section ranges from the Palmatolepis minuta minuta Biozone to at least the Palmatolepis rugosa trachytera Biozone. Hiatuses of several conodont biozones occur due to the facies setting (erosion and reworked sediments which are recognized by reworked conodonts) rather than thrusting or folding. The environmental setting was characterized by coeval subaerial volcanism resulting in numerous pyroclastic deposits. The depositional environments and intense volcanic activity at the Hushoot Shiveetiin gol section limited the stratigraphic distribution, abundance, and diversity of many elements of the fauna such as brachiopods. Ostracods were very abundant and diverse through many parts of the section. Although limited in stratigraphic distribution, the crinoid fauna is the most diverse Palaeozoic fauna collected from Mongolia to date and supports the hypothesis that the CAOB was a biodiversity hotspot in the aftermath of the Frasnian–Famennian extinction event.

Highlights

The global atmospheric CO2 and climate significantly changed during the mid-Palaeozoic, especially in the Late Devonian (Algeo and Scheckler 1998; Stein et al 2007; Becker et al 2016) and coincided with major extinction events
Forty-five samples between 1 and 4 kg were collected for biostratigraphic analysis from the eastern and western Hushoot Shiveetiin gol section in order to enhance the stratigraphic record published by Suttner et al (2020)
The Hushoot Shiveetiin gol section ranges from the Palmatolepis minuta minuta Biozone to at least the Palmatolepis rugosa trachytera Biozone (Fig. 2; zonation scheme follows Hartenfels 2011 and Spalletta et al 2017)

Summary

Introduction

The global atmospheric CO2 and climate significantly changed during the mid-Palaeozoic, especially in the Late Devonian (Algeo and Scheckler 1998; Stein et al 2007; Becker et al 2016) and coincided with major extinction events. Recent fieldwork in the Upper Devonian deposits from the CAOB within western Mongolia (Kido et al 2013; Ariunchimeg et al 2014; Suttner et al 2020) and analogous sites in NWChina (Suttner et al 2014; Carmichael et al 2014; Wang et al 2016; Carmichael 2019; Song et al 2019; Stachacz et al 2020) suggest that the Hushoot Shiveetiin gol site in the Baruunhuurai Terrane in western Mongolia (which represents a shallow-water/neritic palaeoenvironment) is likewise essential for understanding biodiversity patterns in isolated ecosystems in the aftermath of the F/F events

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Results

Conclusion