Oligocene stratigraphy across the Eocene and Miocene boundaries in the Valley of Lakes (Mongolia)

Abstract

Cenozoic sediments of the Taatsiin Gol and TaatsiinTsagaan Nuur area are rich in fossils that provide unique evidence of mammal evolution in Mongolia. The strata are intercalated with basalt flows. 40Ar/39Ar data of the basalts frame the time of sediment deposition and mammal evolution and enable a composite age chronology for the studied area. We investigated 20 geological sections and 6 fossil localities of Oligocene and early Miocene deposits from this region. Seventy fossil beds yielded more than 19,000 mammal fossils. This huge collection encompasses 175 mammal species: 50% Rodentia, 13% Eulipotyphla and Didelphomorphia, and 12% Lagomorpha. The remaining 25% of species are distributed among herbivorous and carnivorous large mammals. The representation of lower vertebrates and gastropods is comparatively poor. Several hundred SEM images illustrate the diversity of Marsupialia, Eulipotyphla, and Rodentia dentition and give insight into small mammal evolution in Mongolia during the Oligocene and early Miocene. This dataset, the radiometric ages of basalt I (∼31.5 Ma) and basalt II (∼27 Ma), and the magnetostratigraphic data provide ages of mammal assemblages and time ranges of the Mongolian biozones: letter zone A ranges from ∼33 to ∼31.5 Ma, letter zone B from ∼31.5 to ∼28 Ma, letter zone C from ∼28 to 25.6 Ma, letter zone C1 from 25.6 to 24 Ma, letter zone C1-D from 24 to ∼23 Ma, and letter zone D from ∼23 to ∼21 Ma.Electronic supplementary materialThe online version of this article (doi:10.1007/s12549-016-0257-9) contains supplementary material, which is available to authorized users.

Lithostratigraphy of a long, fossiliferous Oligocene sequence: Revisiting Saint Jacques, Nei Mongol, China

“…The presence of Ardynia praecox and Gobiomys shows that the lower Saint Jacques sequence extends into the Eocene. Another taxon that sheds light on the E-O boundary is Ardynomys, a primitive cylindrodontids previously known from the late Eocene of Nei Mongol Wang and Meng, 2009;Gomes Rodrigues et al, 2014;Wasiljeff et al, 2020;Wasiljeff and Zhang, 2022), the late Eocene to the early Oligocene of Mongolia (Dashzeveg, 1996;Daxner-Höck et al, 2017), and the late Eocene of North America (Wood, 1970;1974;Korth, 1992). In Saint Jacques, Ardynomys occurs in litho-units 3 and 4.…”

A New Fossil Erinaceidae from the Shajingyi Area in the Lanzhou Basin, China

“…The known species from the Oligocene include Palaeoscaptor, Metexallerix and Amphechinus (Huang, 1984;Qiu and Gu, 1988;Wang et al, 1981;Daxner-Höck et al, 2017), whereas species from European and American areas that have similar characters include those belonging to the Galericinea, Apulogalerix, Galerix and Parasorex (Fig. 2) (Mein and Suárez, 1993;Ziegler, 2005;Furió et al, 2010;Federico and Flaviano, 2013;Klietmann et al, 2014;Prieto et al, 2015).…”

Miocene Ochotonids of the Genus Bellatona (Lagomorpha, Mammalia) from Mongolia

“…The studied fossil material comes from the Loo Formation exposed in several Miocene localities of the Valley of Lakes in Central Mongolia (Daxner-Höck et al, 2017). It was collected by members of the Austrian-Mongolian Expedition as part of the projects FWF, P-10505-GEO, P-15724-N06 and P-23061-N19 (led by G. Daxner-Höck).…”

“…O c c u r r e n c e. Central Mongolia, Valley of Lakes, Loo Formation; early Miocene, zone D (Uncheltseg, UNCH-A/3; Hotuliin Teeg, HTE-001, HTE-003, HTE-008), zone D1/1 (Olon Ovoony Hurem, ODO-B/1) (Daxner-Höck et al, 2017); Ara Hangai aymak, Bugat; China, Shanxi, Xinzhou, early Miocene (Zhou, 1988)…”