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.

中文翻译：

---

湖谷（蒙古）跨越始新世和中新世边界的渐新世地层。

塔特辛戈尔和塔特辛查干努尔地区的新生代沉积物富含化石，为蒙古哺乳动物的进化提供了独特的证据。地层夹有玄武岩流。玄武岩的⁴⁰ Ar/ ^{39 Ar 数据确定了沉积物沉积和哺乳动物进化的时间，并为研究区域提供了复合年龄年代学。}我们调查了该地区渐新世和早中新世矿床的 20 个地质剖面和 6 个化石产地。70 个化石床出土了 19,000 多块哺乳动物化石。这个庞大的收藏包括 175 种哺乳动物：50% 啮齿类动物、13% 真鼠类和双鼠类、12% 兔类动物。其余25%的物种分布在草食性和肉食性大型哺乳动物中。低等脊椎动物和腹足动物的代表性相对较差。数百张 SEM 图像展示了有袋动物、真鼠动物和啮齿动物齿列的多样性，并深入了解渐新世和中新世早期蒙古小型哺乳动物的进化。该数据集、玄武岩 I (∼31.5 Ma) 和玄武岩 II (∼27 Ma) 的辐射年龄以及磁性地层数据提供了哺乳动物组合的年龄和蒙古生物带的时间范围：字母区域 A 的范围从 ∼33 到 ∼31.5 Ma，字母区域B从～31.5到～28Ma，字母区域C从～28到25.6Ma，字母区域C1从25.6到24Ma，字母区域C1-D从24到～23Ma，字母区域D从～ 23 至 ∼21 Ma。