# Cenozoic paleoecological evolution of NE Tibet: A review of magnetostratigraphically-constrained mammal records

Zhantao Feng, Weilin Zhang, Xiaomin Fang, Guillaume Dupont-Nivet, Maodu Yan, Bastien Mennecart, Sirui Zhang, Tao Zhang, Jinbo Zan, Chunhui Song

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Zhantao Feng, Weilin Zhang, Xiaomin Fang, Guillaume Dupont-Nivet, Maodu Yan, et al.. Cenozoic paleoecological evolution of NE Tibet: A review of magnetostratigraphically-constrained mammal records. Earth-Science Reviews, 2025, 267, pp.105156. 10.1016/j.earscirev.2025.105156. insu-05076379

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Cenozoic paleoecological evolution of NE Tibet: A review of magnetostratigraphically-constrained mammal records

Zhantao Feng, Weilin Zhang, Xiaomin Fang, Guillaume Dupont-Nivet, Maodu Yan, Bastien Mennecart, Sirui Zhang, Tao Zhang, Jinbo Zan, Chunhui Song

<figure><img src="image_3.png" /></figure>

PII: S0012-8252(25)00117-5

DOI: https://doi.org/10.1016/j.earscirev.2025.105156

Reference: EARTH 105156

To appear in: *Earth-Science Reviews*

Received date: 24 October 2024

Revised date: 6 April 2025

Accepted date: 6 May 2025

Please cite this article as: Z. Feng, W. Zhang, X. Fang, et al., Cenozoic paleoecological evolution of NE Tibet: A review of magnetostratigraphically-constrained mammal records, *Earth-Science Reviews* (2024), https://doi.org/10.1016/j.earscirev.2025.105156

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Cenozoic paleoecological evolution of NE Tibet: a review of magnetostratigraphically-constrained mammal records

Zhantao Feng<fnref n="1" />, <fnref n="2" />*, Weilin Zhang<fnref n="1" />*, Xiaomin Fang<fnref n="1" />, <fnref n="3" />, Guillaume Dupont-Nivet<fnref n="2" />, <fnref n="4" />, Maodu Yan<fnref n="1" />,
Bastien Mennecart<fnref n="5" />, Sirui Zhang<fnref n="6" />, Tao Zhang<fnref n="3" />, Jinbo Zan<fnref n="1" />, Chunhui Song<fnref n="3" />

<footnote n="1">¹ State Key Laboratory of Tibetan Plateau Earth System and Resources Environment, Institute of
Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, China</footnote>

<footnote n="2">² Géosciences Rennes, UMR-CNRS, University of Rennes, Rennes, France</footnote>

<footnote n="3">³ School of Earth Sciences, Lanzhou University, Lanzhou, China</footnote>

<footnote n="4">⁴ Helmholtz Centre Potsdam -GFZ, German Research Centre for Geosciences, 14473 Potsdam,
Germany</footnote>

<footnote n="5">⁵ Naturhistorisches Museum Basel, Augustinergasse, Basel, Switzerland</footnote>

<footnote n="6">⁶ State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China</footnote>

<footnote>*Corresponding author: fengzht@itpcas.ac.cn; zhangwl@itpcas.ac.cn</footnote>
**Abstract**

The northeastern Tibetan Plateau (NETP) is an ideal laboratory for investigating the interplay between tectonics, climate and biotic evolution. Cenozoic sedimentary basins in this region have recorded ecological shifts linked to the evolution from a wetter monsoonal to an arid climate, in response to the formation of the Tibetan Plateau and to global climate variations. Through decades of intense investigations from various international groups, the Longzhong Basin (LB) in the eastern segment of the NETP represent one of Asia's best dated continental records with a comprehensive set of climate proxies that have allowed major advances in the reconstruction of paleoenvironmental conditions and landscape evolution, as well as understanding of their driving forces. The LB also preserves a particularly rich and well-documented mammal fossil record offering key insights for reconstructing paleoecological conditions by analyzing taxonomic compositions and faunal characteristics. However, a comprehensive review synthesizing previous faunal record studies—which have primarily focused on individual sub-basins of the LB—remains to be performed in order to develop an understanding of regional patterns and drivers of ecological shifts. In this review, we compile the best-dated and richest mammalian fossil records of the LB in the Lanzhou, Xining, and Linxia sub-basins. We integrated all published mammalian fossil taxa from these sub-basins into a re-evaluated magnetostratigraphic framework dating back to the Oligocene. Subsequently, we assigned ecological scores to reflect the environments inhabited by these fossil assemblages, thereby enabling a semi-quantitative reconstruction of their habitats over time and space. Our results suggest that the LB region was characterized by open woodland during the Oligocene–Early Miocene, transitioned to dense forest during the Middle Miocene, and evolved into savanna- and steppe-dominated environments beginning in the Late Miocene. These paleoecological changes, as supported by regional mammalian fossil- and pollen-based ecology studies, strongly correlate with monsoonal precipitation patterns previously reported from terrestrial and marine records. Thus, a progressive intensification of East Asian monsoon precipitation in the LB from late Oligocene to the Early Miocene, a pronounced upsurge during the Middle Miocene, and a large periodic reduction from the late Middle Miocene to the Quaternary can be inferred. Furthermore, integrating these new paleoecological insights with published data on sedimentary facies, provenance, and sedimentation rates allows us to elucidate the regional paleoecological and geomorphological evolution extending to the late Eocene. Under the combined influence of orogenic uplift and global cooling, the LB region gradually evolved from low-elevation, low-relief landscapes characterized by drier conditions and open woodland environments following the Eocene–Oligocene Transition to relatively high-elevation, high-relief landscape featuring pronounced monsoonal seasonality, persistently drier conditions, and ecosystems dominated by C4 plants during the Late Miocene–Quaternary.

**Keywords**

Paleoecology, Landscape, Magnetostratigraphy, Mammal, Fossil, East Asia, Monsoons, Northeastern Tibetan Plateau
Contents

1. Introduction ..................................................................................................................5

2. Geological setting ........................................................................................................6

3. Cenozoic stratigraphic sequences in the Longzhong Basin ....................................8

3.1. Eocene stratigraphic sequences and facies ....................................................8

3.2. The lithofacies sequences since the Oligocene................................................9

4. The magnetostratigraphic age of the mammalian fossil fauna ................................10

4.1. Chronology of mammalian fauna in the Xining Basin....................................10

4.2. Chronology of mammalian fauna in the Lanzhou Basin..................................13

4.3. Chronology of mammalian fauna in the Linxia Basin....................................17

5. Oligocene to Pleistocene paleoecology of the Longzhong Basin indicated by mammalian faunas ........................................................................................................22

6. Comparison to environmental proxy records ........................................................24

6.1. Mammal fossil-based ecology from the Longzhong Basin region ....................24

6.2. Pollen fossil-based ecology from the Longzhong Basin region....................24

6.3. Comparison to regional climate evolution ........................................................25

7. Paleoecological landscape evolution of the Longzhong Basin since the late Eocene.28

7.1. The late Eocene ....................................................................................................28

7.2. From the Eocene-Oligocene Transition to the Mid-Miocene Climatic Optimum 28

7.3. The Middle Miocene ........................................................................................30

7.4. The Late Miocene to Pliocene........................................................................30

7.5. The Quaternary ....................................................................................................31

8. Summary and future directions....................................................................................32
Acknowledgments..................................................................................................................34

References.................................................................................................................................34
# 1. Introduction

The northeastern Tibetan Plateau (NETP), located farthest from the India–Asia collision zone, serves as a crucial transitional region in terms of lithospheric deformation, topographic evolution, and climatic regimes (Li J. et al., 2014; Fang et al., 2019). Topographically, the elevation of the NETP shifts dramatically from 4,000–5,000 m in the interior of the plateau to approximately 1,000 m near the central Loess Plateau and the Gobi Desert. Climatically, the NETP is positioned within the monsoonal triangle zone, representing a transitional belt between the warm–humid climate influenced by the Asian monsoon and the arid–cold conditions of the inland Asian interior (Li J. et al., 1988; Caves Ruggenstein and Chamberlain, 2018; Fig. 1). This unique setting has made the NETP an ideal natural laboratory for investigating the interactions between tectonic uplift and climate change, attracting long-standing attention in geoscientific research. Studies of the Asian monsoon–arid climate organization and evolution have frequently focused on this region (Guo et al., 2002; Licht et al., 2014; Wu et al., 2022), with climatic transitions generally attributed to Tibetan Plateau uplift (Hui et al., 2021a, 2023), global cooling (Dupont-Nivet et al., 2007; Miao et al., 2012; Nie et al., 2017), and/or the retreat of the proto-Paratethys Sea (Bosboom et al., 2014a; Meijer et al., 2019, 2021).

Reconstructing paleoenvironmental changes in the NETP since the Cenozoic has largely relied on sedimentary records from regional basins. For example, the Longzhong Basin preserves a continuous sedimentary sequence from the Eocene to the Pleistocene, offering an excellent chronological framework with only a few minor age disputes (e.g., Yue et al., 2000; Wu et al., 2006; Zhang Y.-B. et al., 2014; Wang W. et al., 2016; Fang et al., 2019; Meijer et al., 2019, 2021; He et al., 2021). These limited chronological discrepancies do not undermine the robust stratigraphic framework that underpins our interpretations of regional tectonics and climate (e.g., Dupont-Nivet et al., 2007; Fang et al., 2016; Ao et al., 2020). Moreover, the sedimentary basins in the NETP yield a wealth of high-quality proxy records, making them ideal settings for investigating monsoon dynamics. However, physical and chemical proxies, which are likely affected by sediment grain size and depositional environment, may yield different climatic signals regarding the evolution of the East Asian monsoon since the Late Miocene. Proxies such as pollen, carbonate isotopes, biomarkers, and sediment color have been used to infer a weakening of the East Asian monsoon since the Late Miocene (e.g., Miao et al., 2012; Peng et al., 2016; Hui et al., 2021a; Yang et al., 2022; Zhang T. et al., 2022), while other proxies, including n-alkanes, clay minerals, Rb/Sr ratio and environmental magnetism, suggest a stepwise intensification of monsoonal precipitation during the same period (e.g., Fu et al., 2017; Song et al., 2022). In this context, fossil evidence offers a critical yet underutilized tool for reconstructing past ecological conditions and monsoon evolution. Although plant fossils have successfully revealed that Central Tibet hosted a “Shangri-La” ecosystem during the Eocene (e.g., Su et al., 2020; Zhou et al., 2023), the sparse distribution of megafossil plant in the NETP and the complications arising from long-distance pollen transport limit their utility for local reconstructions. By contrast, mammalian fossils in the NETP serve as robust indicators of past ecological conditions, with their taxonomic composition and faunal characteristics reflecting specific habitat preferences and climatic constraints. However, research utilizing mammalian fossil records to reconstruct paleoenvironmental changes in this region remains relatively scarce.
Fortunately, the sedimentary basins in the NETP contain many mammalian fossils from the Cenozoic (Liu et al., 1992; Qiu Z.-X. et al., 1997; Wang X.-M. et al., 2003, 2007; Deng et al., 2004, 2013a). The Longzhong Basin (LB), which is composed of several sub-basins (Fig. 2), represents one of the richest fossil-bearing basins in the NETP, preserving mammalian faunas from the Oligocene to the Quaternary (Deng et al., 2013a). However, prior paleoenvironmental studies based on mammalian fossils in this region have largely focused on single species (e.g., rhinoceroses, gomphotheres, or squirrels) (e.g., Biasatti et al., 2018; Deng et al., 2023; Qiu Z.-D. and Li, 2023; Wang S. et al., 2023) or individual sub-basins (e.g., Deng et al., 2004; Zhang P. et al., 2016, 2018; Fang et al., 2019; Wang X.-M. et al., 2023), limiting broader regional comparisons. Moreover, paleomagnetic dating within the LB remains subject to multiple interpretations, despite constraints from fossil-bearing horizons (e.g., Qiu Z.-X. et al., 2001; Wu et al., 2006; Fang et al., 2019; Zheng et al., 2023; Hou et al., 2023). These discrepancies underscore the need for a comprehensive reassessment of stratigraphic, biostratigraphic, and magnetostratigraphic frameworks to refine our understanding of the region's environmental history.

In this study, we systematically integrate fossil mammal assemblages, magnetostratigraphy, and sedimentary records from the Lanzhou, Xining, and Linxia Basins, three sub-basins in the LB, to reconstruct the paleoecological evolution of the NETP. Specifically, we (1) critically review and synthesize existing paleomagnetic age constraints for fossiliferous sections in the LB, refining the temporal framework of mammalian faunas across three key sub-basins; (2) compile and analyze published mammalian fossil taxa to reconstruct habitat shifts and ecological transitions; and (3) synthesize paleoecological reconstructions with sedimentological evidence, including depositional environments, provenances, and sedimentation rates, to infer landscape evolution since the late Eocene. Our findings provide new insights into the long-term interplay among regional tectonics, climate dynamics, and biotic evolution, offering a more refined framework for understanding the paleoclimatic and paleoenvironmental history of the NETP.

## 2. Geological setting

The NETP, encompassing an area of 560,000 square kilometers, is tectonically bounded by the sinistral strike-slip Altyn Tagh fault to the west, the sinistral strike-slip Kunlun–West Qinling faults to the south, the Qilian–Haiyuan faults to the north, and the Liupan Shan transpressional fault to the east (Li J. et al., 2014; Fig. 1). Topographically, this region consists of a series of rhombic basins and parallel ranges with higher elevations in the western part and lower elevations in the eastern part, in contrast to the much lower elevation areas of the Tarim Basin, Alxa, and Ordos Plateau. Geotectonically, the area belongs to the central part of the Central Orogenic Belt and is at the intersection of the Tarim Craton, North China Craton, and Tethys Orogenic Belts (Dong et al., 2021).

The LB is located in the eastern segment of the NETP, roughly bounded by southeastern Qilian Shan, northern West Qinling Shan, and western Liupan Shan and connects to the Ningxia Basin to the northeast (Zhai and Cai, 1984; Fig. 1). It can be subdivided into several sub-basins, namely the Longxi-Jingning, Lanzhou, Linxia, Xining, and Xunhua-Guide Basins (Zhai and Cai, 1984; Fig. 2). During the Cretaceous, under a left-lateral strike-slip extensional regime, the basin experienced subsidence controlled by normal faults along its southern margin (characterized by north-dipping faults) and its eastern margin (characterized by west-dipping faults) (Horton et al., 2004). This tectonic setting led to the widespread deposition of red clastic rocks, with a dominant
distal fluvial-lacustrine facies developing in the united LB (Horton et al., 2004). Since the early
Eocene, the LB has subjected to significant deformation that coincides with rapid uplift and
cooling of the West Qinling Shan at ~50-45 Ma, as indicated by apatite (U-Th)/He dating and the
initiation of thrust faulting at ~50±8 Ma (Clark et al., 2010; Duvall et al., 2011). During this time,
distinct depositional environments developed: the Linxia Basin, proximal to West Qinling,
accumulated alluvial fan and fluvial deposits (Feng et al., 2022a), while the Xining Basin was
characterized by distal floodplain and saline lake settings (Dai et al., 2006; Fang et al., 2019; Yang
et al., 2019). The Lanzhou Basin received fan-delta and fluvial deposits (Yue et al., 2000, 2003;
Wang W. et al., 2016). Strong lithostratigraphic correlations among Eocene strata in the Xining,
Guide, Qianhu, and Heixia Basins (Song, 2006; Fang et al., 2007; Liu et al., 2013) and detrital
zircon U-Pb ages suggest that West Qinling Shan is a primary sediment source of the united LB
(Zhang J., Wang et al., 2016; Yao, 2019; He et al., 2021; Feng et al., 2022a). From the Eocene to
the Oligocene, spatial variations in sedimentary architecture reflect a transition from thick alluvial
conglomerates (>1000 m) in the Kunlun foreland region to sandstone-mudstone sequences (~800
m) in Guide region and finer-grained deposits (~600 m) in Xining region (Fang et al., 2007). A
similar trend is observed along the West Qinling Shan-Linxia-Lanzhou transect, where sediment
thickness decreases from Linxia region (>1000 m) to Lanzhou region (~800 m) and Maxian Shan
region (~170 m), with facies evolving from alluvial fans to fluvial and lacustrine deposits (Yue et
al., 2000, 2003; Wang W. et al., 2016; Ma et al., 2021). Since the Miocene, accelerated uplift in
the Laji, Jishi, and Maxian Mountains at 25-22 Ma and 13-8 Ma has led to fault propagation and
basin segmentation (Fang et al., 2003; Lease et al., 2007, 2012; Xiao et al., 2012; Li J. et al., 2017),
reorganizing drainage systems into comb-shaped networks orthogonal to mountain fronts (Fang et
al., 2016). This transition resulted in foreland basin development, with high sedimentation rates in
foredeep zones and reduced accumulation in forebulge regions. Concurrently, Sr isotope data
indicate a unified lake system during the Paleogene, followed by divergence in ⁸⁷Sr/⁸⁶Sr ratios
after 22 Ma, marking basin fragmentation and drainage reorganization due to intensified tectonic
activity (Liu Y. et al., 2024). In addition, numerous peneplains have developed within the LB and
its surrounding regions, with the most prominent examples observed in Daban Mountain, Maxian
Mountain, and the western Qinling Mountains. Based on the ages of the overlying sediments, the
final formation and subsequent disintegration of the Maxian and Daban Mountain peneplains
occurred before approximately 6.9 Ma and 6.7 Ma, respectively (Li J. et al., 2017; Ma et al., 2020).
Collectively, the original LB existed as a unified entity prior to its segmentation into sub-basins
during the Miocene. Following this division, the segmented individual areas were subsequently
designated as specific sub-basins, marking the termination of the original LB. Given that this
study discusses multiple sub-basins while extending its temporal scope back to the Late Eocene,
this paper introduces the term " Longzhong Basin (LB) region" to collectively describe the
post-Miocene assemblage of these sub-basins, ensuring terminological consistency.

Cenozoic sediment deposition within sub-basins is primarily characterized by three distinct
stratigraphic Groups, often exhibiting a prominent angular unconformity between the lower and
middle Groups (QBGMR, 1991; GPBGMR, 1997; Liu et al., 2013; Meijer et al, 2019, 2022). The
Paleogene Xining Group unconformably overlies older basement or Cretaceous strata. It
comprises a diverse assemblage of deposits, from red-purple basal fluvial conglomerates and braided channel sands to overbank mudstones, lacustrine deposits, and distal alluvial fan sequences, reflecting an evolving depositional environment that shifted in response to regional uplift and erosion. Overlying the Xining Group, the Neogene Guide Group is bounded by a prominent angular unconformity and records a later phase of basin development, dominated by coarse conglomerates interbedded with brownish sandstones, siltstones, and mudstones, the Guide Group documents the progression from alluvial fan and braided channel systems in its lower part to more stable floodplain and shallow lacustrine environments in its upper stratigraphy. Upon these two groups, aeolian dust accumulated on flat erosion surfaces and fluvial terraces (Pan et al., 2009; Feng et al., 2022b) and altered fluvial hydrochemistry (Yang Y. et al., 2017). Additionally, the Yellow River and its tributaries traverse the LB region, exposing Cenozoic strata and forming a series of fluvial terraces (Li J. et al., 2014). In terms of the chronological age of the strata, the oldest stratigraphic sequences within the LB were constrained from Eocene to Miocene within the Lanzhou and Xining sub-basins mainly through magnetostratigraphy and rare U-Pb isotope dating of volcanic ash and carbonate (Yue et al., 2000; Wang W. et al., 2016; Fang et al., 2019; Meijer et al., 2019, 2022; He et al., 2021). The strata in the western Linxia Basin have also been constrained to start in the Eocene (Feng et al., 2022a). Other sub-basins, including the Xunhua, Tianshui, and Guide Basins, appear to start later in the Oligocene with generally higher but localized accumulation rates in relation to the compartmentalization of the Longzhong Basin into these smaller, mostly Miocene, sub-basins (Fang et al., 2005; Lease et al., 2012; Wang X.-X. et al., 2023). The resulting sedimentary accumulations throughout these sub-basins preserved a rich mammalian fossil record through well-constrained ages ranging from the Oligocene to the Pliocene (Deng et al., 2013a).

The modern climate in the LB region is characterized by a continental monsoon climate. Warm temperate zone montane broadleaved forests and subalpine coniferous forests are distributed in the mountainous areas surrounding the basin, and the landscape within the basin consists of temperate deciduous broadleaved forests.

### 3. Cenozoic stratigraphic sequences in the Longzhong Basin

The Lanzhou, Xining, and Linxia Basins, three sub-basins of the LB, preserve an abundant collection of mammalian fossils dating back to the Oligocene. Remarkably, pre-Oligocene strata have remained barren of fossils in the LB despite being well-exposed and widely studied in these three sub-basins in comparison with other sub-basins within the region. The reason for the lack of Eocene fossils in the LB remains to be determined and may relate to the changes in depositional environments through the Eocene-Oligocene transition (EOT) affecting taxa occurrences (Barbolini et al., 2020).

#### 3.1. Eocene stratigraphic sequences and facies

The Eocene strata in the Xining Basin are divided into three formations that record distinct depositional environments reflective of regional paleoclimatic and tectonic evolution (Dai et al., 2006; Fang et al., 2019; Yang et al., 2019; Meijer et al., 2019, 2022; Fig. 3). According to these studies, the early Eocene Qijiachuan Formation preserves a transition from low-energy distal floodplain and alluvial mudflat settings, indicated by fine-grained sediments in the lower and upper parts, to an evaporitic environment in the central part, where abundant gypsum deposits point to the development of a saline lake. Overlying this, the Honggou Formation records a spatial
differentiation in depositional settings: in the central basin, the predominance of mudstones intercalated with gypsum indicates a stable alluvial mudflat and saline lake environment, whereas in the eastern basin, coarse-grained sandstones, conglomerates, and interbedded channel deposits reveal the influence of a meandering river system, highlighting a more dynamic fluvial regime. Finally, the late Eocene Mahalagou Formation is characterized by cyclic changes in depositional conditions, as reflected by alternating layers of red mudstones and gypsum (Dupont-Nivet; 2007; Meijer et al., 2019; Fig. 4e). The gypsum layers suggest episodes of high groundwater levels and perennial subaqueous playa conditions, while the red mudstones, often displaying oxidation features, indicate periods of exposure and deposition within distal alluvial fan environments (Dupont-Nivet; 2007).

In the Lanzhou Basin, the Eocene strata are divided into early Eocene Xiliugou and middle to late Eocene lower Yehucheng Formations (Yue et al., 2000; Wang W. et al., 2016; Fig. 3). The Xiliugou Formation is mainly composed of red-colored, coarse- to fine-grained sandstones with low-angle cross-stratification, planar cross-bedding, and horizontal bedding in the lower part and massive, homogeneous, and loose sandstone beds in the upper part (Yue et al., 2000; Wang W. et al., 2016; Figs. 3 and 4c). The sandstones are several meters to tens of meters thick and are laterally continuous over hundreds of meters. The depositional environment of the Xiliugou Formation can be interpreted as a sandy braided river system (Wang W. et al., 2016; Fig. 3). The lower Yehucheng Formation is also characterized by regular alternations of laterally continuous gypsum layers and red mudstone beds, developed in mudflat and playa saline lake conditions (Wang W. et al., 2016; Ao et al., 2020; Fig. 4d). These gypsum/mudstone alternations are regulated by the eccentricity-driven atmospheric water supply to the basin (Dupont-Nivet; 2007; Ao et al., 2020). More interestingly, the disappearance of the gypsum layers in these two sub-basins occurred at the EOT and is considered a direct record of the global climate as a major contributor to the inland environment of Asia (Dupont-Nivet; 2007; Ao et al., 2020).

In the Linxia Basin, the Eocene is expressed in the western part of the basin by the 490-meter-thick Dahejia section that has been dated to approximately 54–40 Ma via magnetostratigraphic methods (Feng et al., 2022a). Lithological and sedimentary structure analysis revealed three distinct parts: the lower section (53–51 Ma) features massive reddish quartz-rich coarse sandstone interbedded with massive pebble-to-cobble conglomerates, indicating an alluvial fan environment; the middle section (51–47 Ma) comprises massive maroon quartz-rich fine sandstone interbedded with light maroon laminated quartz-rich coarse sandstone and cobble conglomerates, suggesting a braided fluvial environment; and the upper section (47–40 Ma) primarily consists of massive maroon argillaceous siltstone, silty mudstone, and gypsiferous mudstone interbedded with thin layers of calcareous coarse sandstone, indicating a mudflat and distal floodplain environment (Feng et al., 2022a; Fig. 3).

Overall, the stratigraphy and lithofacies within these three sub-basins can be correlated and provide valuable insights, as the lithofacies transition across the basins reflects a continuum from proximal to distal depositional environments, enabling an integrated understanding of the sedimentary evolution of the wider region. In addition, the oldest Cenozoic sediments in this region disconformably overlie the Cretaceous deposits (Horton et al., 2004; Figs. 3, 4a, and 4c). According to magnetostratigraphy, these disconformity boundaries possibly recorded the far-field response to the initial India–Eurasia collision (He et al., 2021; Meijer et al., 2022).

**3.2. The lithofacies sequences since the Oligocene**
Numerous sub-basins, including the Lanzhou, Xining, Linxia, Guide, Xunhua, and Tianshui Basins, extensively expose sedimentary strata from the Oligocene to the present. Due to the large number of studied sections, the detailed lithological characteristics of this region are not described herein but can be thoroughly reviewed in the relevant academic papers for each section. We focus on the sedimentary facies and their spatial distribution characteristics across the time periods. Notably, there have been six major lithofacies assemblages in the LB since the Oligocene according to the lithological characteristics of sedimentary rocks, including 1) a playa characterized by massive red-brown gypsiferous mudstone that is interbedded with green-white layered gypsum (Lease et al., 2012; Fang et al., 2019; Ao et al., 2020); 2) a shallow lake characterized by greenish-white marlite and alternative purple-red mudstone (Li J. et al., 2006; Hough et al., 2011; Fang et al., 2016); 3) a distal floodplain characterized by massive mudstone and siltstone that is interbedded with fine-grained sandstone (Lease et al., 2012; Fang et al., 2016); 4) a braided river characterized by pebble-to-cobble conglomerates interbedded with medium- to coarse-grained sandstone (Lease et al., 2012; Fang et al., 2016); and 5) an alluvial fan characterized by thick boulder conglomerates intercalated with thin gravelly sandstone (Hough et al., 2011; Fang et al., 2016) and eolian loess.

During the early Oligocene, the Tianshui, Xunhua, and eastern Linxia Basins began to be infilled by alluvial and fluvial sediments based on magneto- and biostratigraphic constraints (Fang et al., 2003; Lease et al., 2012; Xu, 2016; Sun et al., 2023; Wang X.-X. et al., 2023), which was synchronous with increases in sedimentation rates and changes in provenance in the Lanzhou and Xining Basins (Wang W. et al., 2016; Fang et al., 2019). During the late Oligocene to Early Miocene, the sedimentary facies of these sub-basins were relatively uniform and were characterized mainly by distal floodplain deposits, which were occasionally accompanied by braided rivers (Figs. 4f and 5). However, large changes in sedimentary facies occurred in these sub-basins during the Middle Miocene to early Late Miocene. The region south of the Maxian Shan-Laji Shan, including Guide, Xunhua, Linxia, and Tianshui, featured primarily lacustrine sedimentary environments (Figs. 4g and 5). In contrast, the Lanzhou and Xining Basins in the northern Maxian Shan-Laji Shan consist of a combination of floodplain and braided river deposits (Fig. 5). From the middle Late Miocene onward, there were large variations in the sedimentary environments of the sub-basins. Notably, the depositional centers in individual sub-basins shifted greatly (Fig. 5). For example, the depositional centers of the Xining and Xunhua Basins migrated away from Laji Shan, whereas the depositional center of the Tianshui Basin migrated away from West Qinling Shan. In addition, the sediment color was mainly dark maroon in the Oligocene-Early Miocene and light maroon and brownish yellow in the Late Miocene. Since the Pliocene, extensive accumulations of eolian loess have been deposited in the region (Figs. 4i and 5).

# 4. The magnetostratigraphic age of the mammalian fossil fauna

Owing to the vast number of mammalian fossils found in the Lanzhou, Xining, and Linxia Basins, each containing its own mammalian fauna, we focused on the mammalian fauna and their ages in these three basins.

## 4.1. Chronology of mammalian fauna in the Xining Basin

Five representative mammal faunas, the Xiejia, Chetougou, Danshuilu, Diaogou, and Xiamen faunas, from the Oligocene to the present have been reported in the Xining Basin (Li C.-K. et al., 1981; Qiu-D et al., 1981; Liu et al., 1992; Fang et al., 2019; Table S1).
4.1.1. The Xiejia fauna

The discovery of Xiejia mammal fossils and the definition of the Early Miocene Xiejia
Formation in the 1980s led to the study of the Cenozoic stratigraphy of the basin (Li C.-K. et al.,
1981). The Xiejia fauna was identified in a 3-m-long, 0.5-m-thick sandstone lens, approximately
80 m above the base of the Xiejia Formation in the Xiejia section (Li C.-K. et al., 1981; Fig. 6).
This fauna includes *Eucricetodon youngi*, *Parasminthus huangshuiensis*, *Parasminthus
xiningensis*, *Parasminthus lajeensis*, *Sinolagomys pachygnathus*, *Sinopalaeoceros xiejiaensis*,
*Tachyoryoctoides kokonorensis*, *Tataromys suni*, *Yindirtemys suni*, *Yindirtemys xiningensis*, and
*Diceratherium* sp. (Li C.-K. et al., 1980, 1981; Qiu Z.-D. et al., 1981; Liu et al., 1992; Qiu Z.-X.
and Qiu Z.-D., 1995; Qui Z.-X. et al., 2013).

The age of the Xiejia fauna was initially determined to be in the Early Miocene based on its
correlation with the European land mammal zones (ELMZ) (Li C.-K. et al., 1980, 1981; Qiu Z.-D.
et al., 1981; Qiu Z.-X. and Qiu Z.-D., 1990); however, despite this correlation, the fauna shares
most genera with the late Oligocene Taben-buluk fauna (Li C.-K. et al., 1981, 1984). It was later
classified as part of the standard Chinese land mammal stage of the Early Miocene (Li C.-K. et al.,
1984; Qiu Z.-X. and Qiu Z.-D., 1990; Deng et al., 2006, 2019). A high-resolution
magnetostratigraphic study from the upper Xiejia section constrained the Xiejia fauna to between
20.71 Ma and 21.08 Ma (Wu et al., 2006). Nevertheless, after conducting a high-resolution
magnetostratigraphic study of the full Xiejia section and reinterpreting the paleomagnetic results
of the East Xining section, the sedimentary sequence of the Xiejia section was dated to between
52 Ma and 17 Ma (Dai et al., 2006). Consequently, Dai et al. (2006) revised the age of the Xiejia
fauna to 25.18–25.50 Ma, making it approximately 4 to 5 Ma years older than Wu et al.’s (2006)
estimate for the same section. Subsequently, the more detailed paleomagnetic results from the
lower part of the Shuiwan section and the Xiejia section, combined with the orbital tuning time
scale, demonstrate that the termination of thick gypsum development in the Xining Basin
corresponds to the EOT, further confirming the reliability of the magnetostratigraphic results of
the Xiejia section (Dupont-Nivet et al. 2007; Abels et al., 2011). Notably, the southern limb of the
Tashan syncline is named the Xiejia section, while the northern limb is named the Tashan section.
High-resolution magnetostratigraphic results revealed that the age of the Tashan section ranges
from ~33 Ma to 16 Ma, which is also consistent with the age of the Xiejia section (Dai et al., 2006)
and supports the late Oligocene age of the Xiejia fauna (Xiao et al., 2012). Fang et al. (2019)
conducted detailed investigations of the stratigraphic sequences, lithology, sedimentary facies, and
paleomagnetic dating results of typical study sections in the Xining Basin, combining integrated
paleontology, paleoclimatic proxies, and new paleomagnetic dating of the Shuiwan and East
Xining sections. These investigations further determined that the age of the Xiejia fauna is ~25 Ma,
marking the latest Oligocene (Fig. 7). Furthermore, the results of Fang et al. (2019) are supported
by recent magnetostratigraphic results from the Xijigou, Caijia, East Xining, and Xiejia sections
(Meijer et al., 2019; Yang et al., 2019).

Meng et al. (2013) argued that the Tabenbulukian age (latest Oligocene) of the Xiejia fauna
should be considered. Li C.-K. et al. (1981) recognized that the Xiejia fauna shares most genera
with the late Oligocene Taben-buluk fauna but completely differs from the latter at the species
level. However, only approximately 11 taxa from the Xiejia section can be identified at the genus
and/or species level, and the limited sample size makes it challenging to discern the
distinctiveness of its evolutionary stage compared with that of the Tabenbuluk fauna (Meng et al.,
2013). In addition, the polarity sequence from the Xiejia section presented by Wu et al. (2006) is complex and does not display a distinct pattern comparable to that of the GPTS 2012 (Gradstein et al., 2012). In contrast, recent paleomagnetic results adopted in this study support assigning a late Oligocene age to the Xiejia fauna (Fig. 7).

### 4.1.2. The Chetougou and Danshuilu faunas

The Chetougou and Danshuilu faunas were found at several sites in the Xining Basin, including Chetougou, Shuiwan, Danshuilu, Hanjiashan, Longzhigou, Qijiagoukou, and Shijia (Li C.-K. et al., 1981; Qiu Z.-D. et al., 1981; Liu et al., 1992; Fig. 6). These fossils were initially suggested to be in the Chetougou Formation on the basis of the locality and lithology of the fossiliferous beds (Liu et al., 1992). Thus, the Danshuilu fauna was included in the Chetougou fauna (Qiu Z.-X. et al., 2013). Fang et al. (2019) cross-checked the lithology of the fossiliferous layers in each section and reported that the fossils from the Chetougou and Shuiwan sites were found in the Chetougou Formation and were thus classified as the Chetougou fauna. In contrast, the fossils from the other sites are located in the lower part of the Guanjiashan Formation and belong to the Danshuilu fauna (Fang et al., 2019). Notably, the Guanjiashan Formation was formerly known as the Xianshuihe Formation. This formation was renamed to distinguish the same stratigraphic divisions in the Lanzhou Basin (Zhang W.-L. et al., 2017). Thus, the Chetougou fauna includes *Eumyarion* sp., Ochotomidae indet., Rodentia indet., Artiodactyla indet., and Rhinocerotidae indet. (Li C.-K. et al., 1981; Qiu Z.-D. et al., 1981; Liu et al., 1992; Fang et al., 2019). The Danshuilu fauna includes *Heterosminthus orientalis*, *Megacricetodon sinensis*, *Protalactaga tungurensis*, *Paleomeryx* sp., *Stephanocema* sp., Cervidae indet., *Sinomioceros* sp., and Rhinocerotidae indet. (Li C.-K. et al., 1981; Qiu Z.-D. et al., 1981; Liu et al., 1992; Fang et al., 2019).

According to the paleomagnetic results of the Xiejia and Shuiwan sections, the age of the Chetougou fauna was dated to approximately 22.5-19.5 Ma (Fang et al., 2019; Fig. 7). For the Danshuilu fauna in the lower part of the Guanjiashan Formation, we estimate an age of 17-16 Ma for the following three reasons. First, paleomagnetic dating constrains the Guanjiashan Formation from the Shuiwan, Guanjiashan, Houwan, and Mojiazhuang sections to approximately 17.2-7 Ma (Yang R. et al., 2017; Zhang W.-L. et al., 2017; Fang et al., 2019), with the lower part of the Guanjiashan Formation containing the Rhinocerotidae indet. in the Shuiwan section dating to ~17-16 Ma (Fang et al., 2019). Second, *Heterosminthus orientalis*, *Megacricetodon* cf. *sinensis*, *Megacricetodon sinensis*, and *Stephanocemas* sp. in the Danshuilu fauna also appear in the Early Miocene Zhangjiaping and Duitinggou faunas of the Lanzhou Basin (Zhang P. et al., 2016). Third, the Diaogou fauna in the Xining Basin contains *Gomphotherium connexum* and *G. wimani* and is estimated to be Middle Miocene (Wang S. et al., 2013a), making it younger than the Chetougou and Danshuilu faunas.

### 4.1.3. The Diaogou fauna

The Diaogou fauna succeeded the Danshuilu fauna and is characterized by a predominance of large forest-dwelling mammals, including an abundant occurrence of proboscideans, as well as a notable presence of small grassland-dwelling mammals (Liu et al., 1992). This fauna contains *Alloptox chinghaiensis*, *Plesiodipus leei*, *Tachyoryctoides* sp., Elasmotherini, *Bunolistriodon minheensis*, *Micromeryx* sp., *Palaeotragus* sp., *Sinomioceros noverca*, *Stephanocemas chinghaiensis*, *Gomphotherium connexum*, and *Gomphotherium wimani* (Li C.-K. et al., 1981; Qiu Z.-D. et al., 1981; Liu et al., 1992; Li C.-X. et al., 2018). These fossils were excavated at several
sites in the Xining Basin, including Diaogou, Bapanshan, Qijia, Li'erbao, Ledu, Shishan, and Leidazhuang (Li C.-K. et al., 1981; Qiu Z.-D. et al., 1981; Liu et al., 1992; Li C.-X. et al., 2018; Fig. 6).

For a long time, there has been a lack of paleomagnetic age constraints on the age of the Diaogou fauna. Its age was estimated to be Middle Miocene, mainly based on correlations with other localities in China, such as Tunggur fauna and Dingjiaergou fauna (Liu et al., 1992; Qiu Z.-X. et al., 2013). The hypodigms of *Gomphotherium connexum* and *Gomphotherium wimani* in the Xining Basin were first studied by Hopwood (1935), but their precise locations and horizons are unclear. Li C.-X. et al. (2018) conducted textual research on tracing localities of *G. connexum* and *G. wimani* described by Hopwood (1935) and obtained their precise positions at Diaogou and Bapanshan, respectively. According to magnetostratigraphic results of the Tashan section adjacent to the Bapangshan section (Xiao et al., 2012; Zan et al., 2015), the age of *G. wimani* was estimated to be ~16–13.8 Ma (Li C.-X. et al., 2018). This estimated age is consistent with the paleomagnetic age of *G. wimani* in the Tianshui Basin (Wang S. et al., 2013a; Liu et al., 2015). Therefore, the Diaogou fauna in the Xining Basin is dated to the Middle Miocene, specifically between 16 and 13.8 Ma (Fig. 7).

#### 4.1.4. The Xiamen fauna

The Xiamen fauna is named based on the discovery of Late Miocene mammalian fossils in the Xiamen section, which consists of *Chleuastochoerus stehlini*, *Cervidae* indet., *Gazella* sp., *Giraffoidea* indet., *Hipparion* cf. *coelophyes*, *Hipparion dongxiangense*, *Hipparion* sp., *Chilotherium wimani*, and *Parelasmotherium* sp. (Liu et al., 1992). The newly discovered *Hipparion* cf. *coelophyes*, *H. dongxiangense*, *Kubanochoerus* sp., and *Testudo hipparionum* at the Mojiazhuang and Banyancun sites further extend the distribution of Xiamen fauna in the Xining Basin (Han et al., 2015, 2021; Yang R. et al., 2017). This fauna is composed mainly of macromammals, with only a few micromammals identified. The species are mainly savanna-type animals, accompanied by a minority of forest-type animals, such as *Cervidae* (Liu et al., 1992). Notably, the presence of *Testudo hipparionum* may indicate the existence of small swamp areas in the Xining Basin (Han et al., 2021). According to the magnetostratigraphic results from the Mojiazhuang section, the age of the fossiliferous beds is estimated to be approximately 10–8 Ma (Yang R. et al., 2017), which likely represents the age of the Xiamen fauna in the Xining Basin (Fig. 7). According to the magnetostratigraphic results of the Mojiazhuang section, the age of fossiliferous beds was estimated to be ~10–8 Ma (Yang R. et al., 2017), which can represent the age of the Xiamen fauna in the Xining Basin (Fig. 7).

## 4.2. Chronology of mammalian fauna in the Lanzhou Basin

### 4.2.1. Overview of the fossiliferous strata

Mammalian fossils from the Lanzhou Basin are found mainly in the Xianshuihe Formation. Based on these mammals, many scholars have conducted extensive magnetostratigraphic studies in the Lanzhou Basin to further investigate the uplift processes and mechanisms of the Tibetan Plateau, the evolution of mammals, the aridification of the Asian interior, and the evolution of the orbital-scale East Asian monsoon (e.g., Miao et al., 2013a; Zhang Y.-B. et al., 2014; Ao et al., 2020; Zhao et al., 2022). However, the ages of the strata obtained by researchers have not been consistently integrated in a comprehensive framework. The paleomagnetic ages of some sections were subjected to reinterpretation. Therefore, it is highly necessary to reevaluate the paleomagnetic dating results by systematically checking the characteristics of the Cenozoic
stratigraphic sequences in the Lanzhou Basin to obtain accurate mammalian fossil ages.

As early as 1997, Qiu Z.-X. et al. (1997) provided a detailed description of the Cenozoic strata of the Lanzhou Basin, especially the Xianshuihe Formation, which contains abundant mammalian fossils, based on detailed basin-wide scale field investigations. Subsequent magnetostratigraphic studies were conducted based on this field investigation.

The Xianshuihe Formation is distributed mainly on the northern bank of the Yellow River and can be divided into three parts (Qiu Z.-X. et al., 1997; Fig. 8). The lower part of the Xianshuihe Formation consists of massive packages of yellow sandstones and overlying red mudstones. Several thin layers of yellowish-green, grayish-white, grayish-black, and/or purplish-red sandstone and conglomerates are interbedded in the yellow sandstone layer, which can be easily distinguished from the interbedded purplish-red gypsum-rich mudstone and mudstone of the underlying Yehucheng Formation. The thickness of this massive yellow sandstone containing cross-stratifications is approximately 80 m at the Nanpoping site and decreases at the Hajiazui site. It can also be traced in the section of the Xiajie site, which it is thinner but contains abundant fossils (Fig. 8). The collection of fossils from this yellow sandstone is known as the Nanpoping fauna. In contrast, the thickness of the overlying massive red mudstone is relatively thin near the Nanpoping site, approximately 20-30 m, whereas it exceeds 100 m at the Hajiazui site. This mudstone is rich in secondary gypsum veins and calcareous nodules, with occasional intercalations of thin layers of gray-green calcareous siltstone in the middle of the mudstone. The red mudstone contains abundant fossils and is named the Xiagou fauna. The middle part of the Xianshuihe Formation consists of a massive layer of white sandstone and overlying massive red mudstone. The white sandstone is lithologically homogenous and highly cross-stratified. At the Nanpoping site, white sandstone occurs frequently, with 9~11 beds, each of which is approximately 5 m thick on average and generally thinner upward. At the Huangyangtou, Hanjiajing, and Duitinggou sites, there are generally four beds of white sandstone, while ~1.5 m of white sandstone is exposed at the northern Shijiayatou site (Fig. 8). The massive red mudstone along the Nanpoping site to the Hajiazui site is mostly parallel laminated and interbedded with thin gray-green and gray-white fine sandstone and limestone. However, the thickening of the red mudstone is accompanied by thinning of the white sandstone in the Xiajie section. In the middle part of the Xianshuihe Formation, the Zhangjiaping fauna is preserved in this white sandstone, whereas the Duitinggou fauna is preserved in this red mudstone. The upper part of the Xianshuihe Formation is exposed only near the Xiajie section in the western part of the basin. The lithology of this segment is dominated by light reddish brown pebbly sandstones, with several thick beds of conglomerates in the middle and upper parts. The upper part of the Xianshuihe Formation preserves the Quantuogou fauna (Fig. 8).

In addition, the Gaolanshan fauna was found on the northern slope of Gaolanshan Mountain on the southern bank of the Yellow River (Qiu Z.-X. and Gu, 1988; Fig. 8), and the Xingjiawan fauna was found in Longgu Mountain near Xingjiawan village (Zhang X., 1993). Furthermore, the mammalian fauna of the Lanzhou Basin was further subdivided by Xie (2004), primarily by dividing the Zhangjiaping fauna into the Miaozuizi and Zhangjiaping faunas. Collectively, the mammalian fauna of the Lanzhou Basin includes, from old to new, the Nanpoping, Xiagou, Gaolanshan, Miaozuizi, Zhangjiaping, Duitinggou, Quantougou, and Xingjiawan faunas.

### 4.2.2. The Nanpoping, Xiagou, Miaozuizi, Zhangjiaping, and Duitinggou faunas

The mammalian fossil species identified in the Nanpoping, Xiagou, Miaozuizi, Zhangjiaping,
and Duitinggou faunas are listed in Table S2.

In the period before paleomagnetic dating, the ages of these five faunas were estimated mostly based on correlations with other localities in China and Europe. In the Nanpoping fauna, *Tsaganomys* is one of the landmark Oligocene fossils of Asia and first appeared in the late early Oligocene and became extinct in the early late Oligocene (Wang X.-M. et al., 2003; Deng et al., 2004). Moreover, *Allacerops* and *Schizotherium ordosium* in the Nanpoping fauna lived in Asia during the Oligocene, with the latter being a characteristic Oligocene species of China (Qiu Z.-X. et al., 1997; Qiu Z.-X. and Wang, 1999). In addition, the age of the Xiagou fauna is considered late Oligocene, mainly on the basis of the occurrence of numerous taxa in the late Oligocene Taben-buluk fauna of the Danghe area in Gansu, including *Yindirtemys grangeri*, *Parasminthus asiae-centralis*, *Parasminthus tangingoli*, *Amphechinus* cf. *rectus*, *Amphechinus* cf. *minimus*, *Sinolagomys kansuensis*, *Heterosminthus lanzhouensis*, and *Litodonomys huangheensis* (Wang B. and Qiu, 2000a, 2000b). The Miaozuizi fauna contains both remnants of Oligocene taxa, such as *Tsaganomys* sp. and *Tachyoryctoides* sp., and more advanced species, such as *Sinolagomys* sp. (Xie, 2004). In addition, Qiu Z.-X. and Xie (1997) suggested that *Aprotodon lanzhouensis* in the Miaozuizi fauna was more primitive than *Aprotodon* in the Early Miocene Bugti Formation of Pakistan. Therefore, the age of the Miaozuizi fauna is considered Early Miocene (Xie, 2004). The ages of the Duitinggou and Quantuogou faunas are relatively close, but the former is more ancient than the latter. The two genera of *Megacricetodon* and *Democricetodon* in the Duitinggou fauna first appeared in Europe during MN4, whereas the *Kubanochoerus gigans* and *Gomphotherium wimani* in the Quantuogou fauna are more primitive than the Tunggur fauna at the evolutionary level and may correspond to MN7 in Europe (Qiu Z.-X. et al., 1997; Xie, 2004).

Opdyke et al. (1998) initially performed paleomagnetic dating of the Duitinggou section at sampling intervals of 1–5 m and identified 9 normal and 8 reversed polarity zones. However, the poor correction of these paleomagnetic results to the geomagnetic polarity time scale enabled several subsequent reinterpretations of these results, resulting in a wide range of fossil ages for the corresponding horizons (Flynn et al., 1999; Qiu Z.-X. et al., 2001, 2013). High-resolution magnetostratigraphic studies have been performed in several sections by Ao's group, including the Duitinggou, Jimazhuang, Quantuogou, and Xingjiawan sections. The sedimentary sequence between ~36 and 5 Ma was thus synthetically obtained (Ao et al., 2016b, 2020; Zhang P. et al., 2016, 2018, 2020; Fig. 9). The lower Xianshuihe Formation of the Duitinggou section is suggested to span from polarity chron C12r to C7n, ranging from ca. 31 Ma to 24 Ma (Zhang P. et al., 2018; Fig. 9). The ages of the Nanpoping fauna in the yellow sandstones and the Xiagou fauna in the overlying red mudstones are estimated to be ~31–30 Ma and ~26–25 Ma, respectively (Zhang P. et al., 2018; Fig. 9). These results are further reinforced by the combined magnetochronology and astrochronology of the underlying Yehucheng Formation in the Duitinggou section (Ao et al., 2020).

In the middle Xianshuihe Formation, high-resolution paleomagnetic results revealed 10 pairs of normal and reversed polarity zones in the Duitinggou section (Zhang P. et al., 2016), which are more robust than the results obtained by Opdyke et al. (1998). The ages for the Miaozuizi and Zhangjiaping faunas in the lower and upper white sandstone layers can be estimated to be ~24–23.2 Ma and 21.3–20.6 Ma, respectively, and the Duitinggou fauna from the sandstone package within the upper part of the middle Xianshuihe Formation has an estimated age of 18.9 Ma according to linear interpolation (extrapolation) using the ages of appropriate geomagnetic
reversal boundaries as age tie points (Zhang P. et al., 2016; Fig. 9). Remarkably, the high-resolution paleomagnetic results of the Duitinggou section can be correlated with the ages of the yellow sandstone and white sandstone in the Xianshuihe Formation in both the Xiajie and Xianshuihe sections (Yue et al., 2000; Wang W. et al., 2016; Fig. 9). Despite the critical thinness of the white sandstone layers in the Xianshuihe section, the ages of the Miaozuizi, Zhangjiaping, and Duitinggou faunas can be roughly estimated from this section (Fig. 9). Notably, the Fenghuangshan section, which is located 7 km south of the Duitinggou section, was investigated by Zhang Y.-B. et al. (2014) in their magnetostratigraphic studies. However, the age of the Nanpoping fauna is constrained at ~24 Ma (Zhang Y.-B. et al., 2014). The thicknesses of the Yehucheng and Xiliugou Formations were determined to be greater than 1500 m, far exceeding the thickness of the same strata unit in nearby sections, where the Yehucheng and Xiliugou Formations are ~600 m thick (Yue et al., 2000; Wang et al., 2016). In addition, we observed that there are different estimations of sedimentation rates for the same section (Zhang Y.-B. et al., 2014; Wang Z. et al., 2021). Therefore, we suggest that the age of the Fenghuangshan section may need to be reevaluated.

### 4.2.3. The Gaolanshan fauna

The Gaolanshan fauna contains only five identified species, namely, *Metexallerix gaolanshanensis*, *Yindirtemys suni*, *Yindirtemys grangeri*, *Tataromys sigmodon*, and *Tsaganomys altaicus*. This fauna was first correlated with the Xiejian stage based mainly on the discovery of an advanced insectivore, *Metexallerix* (Qiu Z.-X. and Gu, 1988; Qiu Z.-X. et al., 2013). Furthermore, the presence of *Tataromys sigmodon* and *Tsaganomys altaicus* in these small faunas has not been detected in any other Miocene faunas, and the Gaolanshan fauna is more likely to be Oligocene in age (Xie et al., 2004; Qiu Z.-X. et al., 2013). This interpretation is consistent with the latest paleomagnetic dating results from the Xining Basin, in which the Xiejia fauna was dated to the late Oligocene (Fang et al., 2019). However, the magnetostratigraphic results of the Nanshan section demonstrate that the Cenozoic sedimentary sequence on Gaolanshan Mountain yields an age of Late Miocene, without considering the constraints of fossil age (Sun et al., 2011). Therefore, considering that the Gaolanshan fauna is older than the Xiagou and Miaozuizi faunas in the Lanzhou Basin and that the Gaolanshan fauna is correlated with the Xiejia fauna in the Xining Basin (Qiu Z.-X. and Gu, 1988; Qiu Z.-X. et al., 2013), we restrict the age of this fauna to ~25 Ma.

### 4.2.4. The Quantougou and Xingjiawan faunas

The Quantougou fauna consists of *Democricetodon tongi*, *Ganocricetodon cheni*, *Heterosminthus orientalis*, *Megacricetodon sinensis*, *Mellalomys gansus*, *Microdyromys wuae*, *Mioechinus* (?) *gobiensis*, *Myocricetodon plebius*, *Ochotonidae* gen. et sp. indet., *Paracricetulus schaubi*, *Plesiodipus leei*, *Protalactaga grabaui*, *Protalactaga major*, *Kubanochoerus gigans*, *Stephanocemas* sp., and *Gomphotherium wimani* (Qiu Z.-X. et al., 1997; Qiu Z.-D., 2000, 2001a, 2001b; Xie, 2004).

Among them, *Democricetodon tongi*, *Heterosminthus orientalis*, *Megacricetodon sinensis*, *Mioechinus* (?) *gobiensis*, *Plesiodipus leei*, and *Protalactaga grabaui* are close to the micromammals in the Middle Miocene Tunggur fauna, while the macromammals, such as *Kubanochoerus gigans* and *Gomphotherium wimani*, are more evolutionarily primitive than those of the Tunggur fauna (Qiu Z.-X. et al., 1997). Therefore, it is inferred that the age of the Quantuogou fauna may be roughly equivalent to MN7 in the European land mammal zonation
(Qiu Z.-X. et al., 1997). The Xingjiawan fauna consists of Cervidae indet., *Chleuastochoerus stehlini*, *Chilotherium haberei*, *Hipparion* sp., *Hyeana variabilis*, and *Stegodon* sp. (Zhang X., 1993). On the basis of the occurrence of *Hipparion*, the age of this fauna is assigned to the Late Miocene Baodean stage (Zhang X., 1993).

High-resolution magnetostratigraphic results from the Quantougou section have constrained the age of the Quantougou fauna to ~12.8–11.7 Ma (Zhang P. et al., 2020), which can further constrain the age of the Xingjiawan fauna. High-resolution paleomagnetic dating results indicate that the Xingjiawan fauna is dated to 11 Ma or 8 Ma (Ao et al., 2016b), both of which are older than the Baodean stage. Recently, four newly identified mammalian taxa from Xingjiawan village — *Yoshi yongdengensis*, *Yoshi faie*, *Paramachaerodus schlosseri*, and *Paramachaerodus yingliangi*—have led paleontologists to propose that the Xingjiawan fauna likely corresponds to the Baodean stage, with an estimated age of approximately 6.5 to 5.8 Ma, or slightly older (Jiangzuo et al., 2022). Subsequently, the discovery of two additional taxa typical of the Baodean stage—‘*Gazella*’ *paotehensis* and *Cervavitus* cf. *shanxius*—prompted a reevaluation of the paleomagnetic results of the Xingjiawan section (Li Y. et al., 2023). Based on these findings, the age of the Xingjiawan fauna was reinterpreted to be approximately 6.54 to 6.62 Ma (Li Y. et al., 2023). Given that the stratigraphic positions of these newly discovered mammalian fossils remain uncertain with respect to the fossiliferous layers analyzed in Ao et al. (2016), it is currently difficult to definitively assess the validity of these interpretations. Moreover, considering that the Xingjiawan fauna is stratigraphically younger than the Quantougou fauna, this study excludes the hypothesis that the Xingjiawan fauna dates to 11 Ma. Instead, we tentatively adopt an age range of 8–6.5 Ma for the Xingjiawan fauna, reflecting the most recent evidence and interpretations.

**4.3. Chronology of mammalian fauna in the Linxia Basin**

The Linxia Basin is home to a vast number of mammalian fossils, making it one of the most
abundant regions for late Cenozoic mammalian fossils in Eurasia. Given the plethora of
mammalian fossils found in this area, the People's Republic of China has constructed a large
museum, which features three special exhibitions, and a Hualin burial site museum in Hezheng
County to preserve this invaluable fossil collection. Mammalian fossils within the Linxia Basin
are classified into four representative fossiliferous mammal faunas: the late Oligocene
*Dzungariotherium*, the Middle Miocene *Platybelodon*, the Late Miocene *Hipparion*, and the Early
Pleistocene *Equus* faunas (Deng et al., 2004). These four principal faunas have been further
divided into 10 faunas based on typical excavation sites as follows: late Oligocene Jiaozigou fauna,
Early Miocene Sigou fauna, early Middle Miocene Shinanu fauna, late Middle Miocene Laogou
fauna, early Late Miocene Guonigou fauna, middle Late Miocene Dashenggou and Yangjiashan
faunas, late Late Miocene Qingbushan fauna, Pliocene Shilidun fauna, and Early Pleistocene
Longdan fauna (Deng et al., 2013a).

The ages of the four representative faunas—*Dzungariotherium*, *Platybelodon*, *Hipparion*, and *Equus* faunas—have been constrained by high-resolution magnetostratigraphy. In contrast, most of the ten subdivided faunas still lack age estimates due to the absence of paleomagnetic measurements from their stratotype sections. Their approximate ages have been determined
mainly through comparisons with horizons from other locations. In addition, many late Oligocene to late Pliocene micromammal assemblages consisting of 121 species arranged in 24 families have been reported (Qiu Z.-D. et al., 2023). Based on their excavation sites, these micromammal fossils have been classified into seven faunas: late Oligocene Yagou fauna, late Oligocene Mansancun fauna, late Early Miocene Gucheng fauna, early Middle Miocene Galijia fauna, late Middle Miocene Lanjiashan fauna, early Late Miocene Yihachi fauna, and late Pliocene Caojiashan fauna (Qiu Z.-D. et al., 2023). The ages of these micromammalian faunas have been primarily assessed by correlating them to the Chinese land mammal stage/age (CLMS) and the European land mammal zones (ELMZ) (Qiu Z.-D. et al., 2023).

Thus, the subdivisions of macrofossils and microfossils within the Linxia Basin's mammalian faunas are inconsistent, and most subdivided fossil faunas lack paleomagnetic age constraints, making systematic integration challenging. Moreover, given that the Linxia Basin is categorized as an intracontinental flexural basin, the sedimentological characteristics exhibit critical temporal and spatial variability concurrent with the basin's evolution. Such variability is prone to causing misinterpretations in the stratigraphic correlation of fossil-bearing horizons (Fang et al., 2016). Consequently, we adopted four established representative faunas to assess the age of the basin's faunas. The subdivision of mammalian fauna will be reevaluated in the future when more stratotype sections with paleomagnetic age results become available in the Linxia Basin. The species of the four representative faunas are listed in Table S3.

### 4.3.1. The *Dzungariotherium* fauna

The *Dzungariotherium* fauna is characterized primarily by its large mammal assemblages, including *Tsaganomys* sp., *Ardynia* ultidentatu, *Ardynia* sp., *Schizotherium*, *Dzungariotherium orgosense*, *Paraceratherium* sp., *Aprotodon* lanzhouensis, *Aprotodon* sp., and *Paraentelodon macrognathus*. Initially, *Dzungariotherium orgosense* and *Paraentelodon macrognathus* were discovered from conglomeratic coarse sandstones between the Tala Formation and Zhongzhuang Formation in Jiaozigou, Dongxiang County (Qiu Z.-X. et al., 1990, 2004a; Deng et al., 2004). Paleontologists have thus designated this layer the Jiaozigou Formation (Deng et al., 2013a, 2021, 2023; Qiu Z.-X. et al., 2023). Subsequent discoveries of Rhinocerotoid fossils have been made at the Yagou and Wangjiachuan sites (Qiu Z.-X. et al., 2004b; Deng et al., 2021), with some paracontemporary micromammal fossils also found at the Yagou and Mansancun sites (Qiu Z.-X. et al., 2023).

The magnetostratigraphic age of the *Dzungariotherium* fauna is largely controversial. Initially, *Dzungariotherium orgosense*, *Rhinoceratidae* indet., *Paraentelodon macrognathus*, and *Gomphotherium* sp. were found together in the lower sandy conglomerate layers at the Jiaozigou site, which has been estimated to date to the Early Miocene based on the presence of proboscidean species (Qiu Z.-X. et al., 1990). Subsequent high-resolution magnetostratigraphic results from the Maogou section, ~3.5 km north of the fossil-bearing section at the Jiaozigou site, indicate that this gravel bed at the base of the Zhongzhuang Formation (also called the Jiaozigou Formation by paleontologists) was deposited ~21 Ma, supporting Early Miocene inference (Fang et al., 1997, 2003). However, paleontologists have found more late Oligocene fossils in the lower part of the Jiaozigou Formation at the Yagou site (Qiu Z.-X. et al., 2004b; Deng et al., 2013a). The paleontologists thus suggest that the fossil of *Gomphotherium* sp. (GVD 86001) found at the beginning is mixed with fossils from the overlying strata and infer that the fossils are of late Oligocene age (Qiu Z.-X. et al., 2004b). These inferences are based on several aspects. First,
*Schizotherium* and *Tsaganomys* were also found in the Oligocene Nanpoping fauna in the Lanzhou Basin (Qiu Z.-X. et al., 1998), with the former being a characteristic Oligocene form in China. Second, *Aprotodon*, *D. orgosense*, and *Paraceratherium bugtiense* were primarily found in late Oligocene deposits across the Central Asian region, including Pakistan, Kazakhstan, and Xinjiang Province in China (Chiu, 1973; Lucas and Bayshashov, 1996; Qiu Z.-X. and Xie, 1997; Antoine et al., 2003). The clade consisting of *Paraceratherium linxiaense* and *Paraceratherium lepidum* is the sister group of *Paraceratherium bugtiense* (Deng et al., 2021). Finally, *Tataromys*, *Tsaganomys*, *Bagacricetodon*, and *Ordolagus* are confined to the Oligocene (Qiu Z.-D. et al., 2023). According to these inferences, magnetostratigraphy results from the Yagou Section at the Yagou site correlate the fossil-bearing sandy gravel layers overlying the Tala Formation with Chron C9n of the early late Oligocene (~27 Ma) (Sun et al., 2023; Fig. 11e).

Additionally, since the magnetostratigraphic results of the Maogou section were questioned by paleontologists (Deng et al., 2004, 2013a), paleomagnetic dating was reconducted, yielding a similar paleomagnetic polarity pattern and different correlations with the GPTS over the long term compared with previous findings (Zheng et al., 2023). The new correlation was mostly based on the *Sayimys* and *Alloptox* found at the Yangwa site and the *Palaeosciurus* sp. and *Plesiodipus leei* found at the Zhuanchang site near the measured Maogou section (Zheng et al., 2023), each of which is assumed to be approximately Tunggurian in age (Qiu Z.-D. et al., 2023). Notably, this new magnetostratigraphic result also supported another line of evidence that a conglomerate layer overlying the Dongxiang Formation, named the Hujialiang Formation, correlates from the south to the center of the basin, indicating an early Late Miocene age (Zheng et al., 2023). However, conglomerates are generally deposited in braided fluvial environments characterized by relatively short durations and instability, leading to risky situations when the conglomerate is used as a marker bed for basin-scale lithostratigraphic correlation. The Linxia Basin is an intracontinental flexural basin, and large lateral variations in the Cenozoic stratigraphic thickness and sedimentary facies, such as the well-known "Zebra Bed" of the Dongxiang Formation, have been documented from the margin of the mountain to the depocenter (Fang et al., 2016). Consequently, the overlying conglomerate deposits associated with the Dongxiang Formation may also be diachronous in nature. In addition to the fossil constraints, the early magnetostratigraphic results from the Maogou section were constrained by fission track dating of nine gypsum samples within the strata (Fang et al., 1997, 2003). Notably, sample DX92, which was collected from the purplish-red mudstone interbedded with the basal conglomerate of the Zhongzhuang Formation, yielded a fission track age of 21.39±1.84 Ma (Chen et al., 1996). Field and microscopic observations indicated that sample DX92 did not exhibit crystal crosscutting of depositional laminations; however, slight continuous deformation of the laminations occurred, suggesting that the gypsum was of syngenetic origin (Chen et al., 1996).

In summary, the magnetostratigraphic age of the *Dzungariotherium* fauna is subjected to two competing age estimates (~27 Ma or ~21 Ma). Further work is needed to determine the absolute stratigraphic age by identifying volcanic ash or employing the U-Pb dating method on calcite.

### 4.3.2. The *Platybelodon* fauna

The *Platybelodon* fauna in the Linxia Basin contains a rich collection of proboscidean fossils, including *Platybelodon grangeri*, *Platybelodon tongxinensis*, *Gomphotherium tassyi*, *Gomphotherium wimani*, *Protanancus wimani*, *Choerolophodon* sp., *Serbelodon zhongningensis*,
and *Zygolophodon* sp. (Deng, 2003; Deng et al., 2004, 2013a; Wang S. et al., 2013b, 2017, 2023; Yang X. et al., 2017). Additionally, other mammalian fossils are abundant, such as *Heterosminthus orientalis*, *Alloptox gobiensis*, *Alloptox guangheensis*, *Pseudaelurus guangheensis*, *Kubanochoerus gigas*, *Kubanochoerus* sp., *Stephanocemas guangheensis*, *Turcocerus* sp., *Anchitherium gobiensis*, and *Chalicotherium* sp., among others.

Mammalian fossils from the *Platybelodon* fauna were mostly discovered in the conglomerates and sandstones of the Dongxiang Formation at the Laogou site in Hezheng County and the Dalanggou and Wangshijie sites in Guanghe County (Fig. 10). In the central basin, the Dongxiang Formation consists of horizontally thick-bedded median sandstones with both massive and weak cross-bedding in the lower part, along with a distinctive unit known as the "Zebra Bed" in the upper part (Fang et al., 2016). The "Zebra Bed" is characterized by alternating layers of purple massive mudstones and relatively massive to weakly horizontal laminated white greenish-gray marlites (Fig. 4g). In contrast, in the southern basin, the Dongxiang Formation is characterized by alternating layers of thin grayish fine conglomerates or sandstones and thick reddish-brown mudstones, capped by well-developed paleosol complexes with substantial luvic properties (Fang et al., 2016). According to the magnetostratigraphy results from the Laogou, Heilinding, and Guonigou sections, the age of the *Platybelodon* fauna is approximately 12.5–11.1 Ma (Wang J. et al., 2010; Fang et al., 2016; Zhang W.-L. et al., 2019; Fig. 11), with the *Platybelodon* fauna gradually becoming younger from north to south in the Linxia Basin (Zhang W.-L. et al., 2019).

### 4.3.3. The *Hipparion* fauna

The *Hipparion* fauna, characterized by its smaller size, was discovered in the Late Miocene Liushu Formation and early Pliocene Hewangjia Formation, within fluvial–lacustrine siltstones or mudstones. Numerous *Hipparion* fauna fossils were collected by paleontologists from the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, at dozens of sites (Fig. 10). These fossils are distinctly divided into four horizons represented by the Guonigou, Dashengou, Yangjiashan, and Shilidun localities (Deng et al., 2013a). The magnetostratigraphic results indicated a living period for the *Hipparion* fauna, spanning from approximately 12 Ma to 5.3 Ma (Fang et al., 2003; Wang et al., 2010), which signifies its long-term continuous evolution and adaptation to environmental changes during the Late Miocene. To elucidate the detailed evolutionary stages of the *Hipparion* fauna, Zhang W.-L. et al. (2020) conducted an in-depth analysis and synthesis of multiple sections bearing the *Hipparion* fauna using paleomagnetic dating results.

The oldest *Hipparion* fauna were excavated from the Guonigou and Yangjiashan sections and included species such as *Pararhizomys hipparionum*, *Dinocrocuta gigantea*, *Machairodus* sp., *Promephitis parvus*, *Ictitherium* sp., *Hyaenictitherium wongii*, *Dinocrocuta gigantea*, *Chleuastochoerus stehlni*, *Shaanxispira* sp., *Miotragocerus* sp., *Hipparion donxiangense*, *Hipparion* sp., *Parelasmotherium linxiaense*, *Chilotherium wimani*, *Acerorhinus hezhengensis*, *Prodeinotherium sinense*, and *Tetralophodon* sp. (Fang et al., 2003, 2016; Deng et al., 2013a, 2013b). This level of the *Hipparion* fauna corresponds to the Guonigou fauna. Based on magnetostratigraphic results in the Guonigou section, the age of the lowermost level of the oldest Chinese *Hipparion* fauna is 11.5 Ma (Fang et al., 2016; Zhang W.-L. et al., 2020; Fig. 11), which is largely consistent with that of the Wangjiashan section (Li J. et al., 1997a).

The second level of the *Hipparion* fauna mostly included *Protalactaga* cf. *tunggurensis*,
Spalacinae indet., Castoridae indet., *Ochotona lagrelii minor*, *Ictitherium hipparionum hyaenoides*, *Adcrocuta* cf. *eximia variabilis*, *Honanotherium* sp., *Cervavitus* sp., *Hipparion* sp., and *Chilotherium* sp. (Fang et al., 2003, Zhang W.-L. et al., 2020). This level of the *Hipparion* fauna corresponds to the Dashengou fauna. According to most of these mammalian fossils preserved in the lower part of the Liushu Formation, the age of the second level of the *Hipparion* fauna is estimated to be between 10 and 8 Ma based on high-resolution magnetostratigraphic results (Fang et al., 2016; Zhang W.-L. et al., 2019; Fig. 11).

The third level of the *Hipparion* fauna includes *Pararhizomys hupparionum*, *Pararhizomys gen* & sp. nov., *Micromys* sp., *Hystrix gansuensis*, *Simocyon primigenius*, *Agriotherium inexpectans*, *Indarctos zdanskyi*, *Promephitis parvus*, *Promephitis hootani*, *Parataxidea sinensis*, *Pleisiogulo* sp., *Ictitherium* sp., *Hyaenictitherium wongii*, *Hyaenictitherium hyaenoides*, *Adcrocuta* *eximia*, *Machairodus palanderi*, *Metailurus* sp., *Metailurus minor*, *Felis* sp., *Chleuastochoerus stehlini*, *Microstonyx* major, *Metacervulus* sp., *Dicrocerus* sp., *Cervivatus novorossiae*, *Honanotherium schlosseri*, *Palaeotragus microdon*, *Miotragocerus* sp., *Sinotragus* sp., *Protoryx* sp., *Gazella* sp., *Hipparion coelophyes*, *Hipparion dermatorhinum*, *Hipparion robustus*, *Hipparion platyodus*, *Ancylotherium* sp., *Tapirus hezhengensis*, *Chilotherium wimani*, *Chilotherium anderssoni*, *Shansirhinus ringstroemi*, *Acerorhinus hezhengensis*, *Dicerorhinus ringstromi*, and *Pliohyrax* sp. (Deng et al., 2013a). These mammalian fossils mainly originate from the upper Liushu Formation and were discovered in the Laogou, Heilinding, Hualin, and Wangjiashan sections (Fang et al., 2003; Wang J. et al., 2010; Zhang W.-L. et al., 2019, 2020). This level of the *Hipparion* fauna corresponds to the Yangjiashan fauna. According to paleomagnetic results from the Wangjiashan, Maogou, Laogou, and Heilinding sections, the ages of these fossils are consistently estimated to be approximately 6.4 to 6.3 Ma (Li J. et al., 1997a; Fang et al., 2003, 2016; Wang J. et al., 2010; Zhang W.-L. et al., 2019; Fig. 11).

The fourth level of the *Hipparion* fauna can be found in the red clays of the Hewangjia Formation at the Wangjiashan and Duikang sections, containing species such as *Hystrix gansuensis*, *Alilepus* sp., *Promephitis* sp., *Sinictis* sp., *Parataxidea sinensis*, *Chasmaporthetes kani*, *Hyaenicyitherium wongii*, *Adcrocuta* *eximia*, *Felis* sp., *Cervavitus novorossiae*, *Paleotragus microdon*, *Samotherium (?)* sp., *Gazella blacki*, *Capricornis* sp., *Sinotragus* sp., *Hipparion licenti*, *Hipparion hippidiodus*, *Hipparion platyodus*, *Hipparion pater*, *Hesperotherium* sp., *Ancylotherium* sp., *Shansirhinus ringstroemi*, and *Gomphotheriidae* indet. (Deng et al., 2013a). This level of the *Hipparion* fauna is linked to the Shilidun fauna. The Hewangjia Formation was dated to between 6 Ma and 4.5 Ma in the Maogou and Wangjiashan sections (Fang et al., 2003) and between 6.5 Ma and 4.1 Ma in the Heilinding section (Wang J. et al., 2010; Fang et al., 2016). The mammalian fossil-bearing horizons were constrained at ~4.8 Ma in the Wangjiashan section (Fang et al., 2003) and at ~5.3 Ma in the Duikang section (Zhang W.-L. et al., 2020; Fig. 11). Therefore, the age of this *Hipparion* fauna was estimated to range from 5.3 Ma to 4.8 Ma.

#### **4.3.4. The Equus fauna**

The *Equus* fauna, which originates from the Wucheng Loess at Longdan in Dongxiang County, encompasses a diverse range of species, including *Aepyosciurus orientalis*, *Bahomys* sp., *Canis brevicephalus*, *Canis* cf. *chihliensis*, *Canis longdanensis*, *Canis teilhardi*, *Castor anderssoni*, *Chasmaporthetes progressus*, *Coelodonta nihowanensis*, *Crocuta honanensis*, *Eirictis robusta*, *Equus* *eisenmannae*, *Felis* cf. *palaeosinensis*, *Felis teilhardi*, *Gatella* cf. *blacki*, *Hemibos gracilis*, *Hesperotherium* sp., *Hipparion* sinense, *Homotherium* cf. *nestianum*, *Homotherium crenatidens*,
*Leptobos brevicornis*, *Lynx shansius*, *Macaca* cf. anderssoni, *Marmota parva*, *Megantereon nihowanense*, *Meles teilhardi*, *Mimomys* cf. gansunicus, *Myospalax arvicolinus*, *Nestoritherium* sp., *Nipponicervus longdanensis*, *Ochotona* cf. thibetana, *Pachycrocuta licenti*, *Pannonictis* cf. pachygnathus, *Panthera palaeosinensis*, *Paradolichopithecus gansuensis*, *Procynocephalus* sp., *Pseudodama* sp., *Sciuridae* gen. et sp., *Sericolagus brachypus*, *Shansirhinus ringstromi*, *Sinicuon* cf. dubius, *Sivapanthera linxiaensis*, *Sus* sp., *Vulpes chikushanensis*, *Postschizotherium* sp., and *Protarctos yinanensis* (Qiu Z.-X. et al., 2002; Deng, 2002, 2005; Deng et al., 2004, 2013a)

This fauna is believed to be slightly older than the Nihewan fauna (Deng et al., 2004), which is supported by magnetostratigraphic findings. The Nihewan fauna, made up of a series of mammalian faunas, is estimated to have spanned a timeframe of approximately 0.8–2.0 Ma (Deng et al., 2008). In the Linxia Basin, the initial paleomagnetic investigation from the Wucheng Loess in the Longdan section indicated that the *Equus* fauna was approximately 2.5 Ma old (Qiu Z.-X. et al., 2004c). However, subsequent paleomagnetic dating proposed a time interval between 2.2 Ma and 1.9 Ma (Liu et al., 2008). Recent comprehensive magnetostratigraphic research on loess deposits from two boreholes in the Longdan and Nalesi sections revealed that the Wucheng Loess began accumulating in the Linxia Basin at approximately 3.0 Ma and firmly established that the *Equus* fauna has an age range of 2.5–2.2 Ma (Zan et al., 2016, 2018a; Fig. 11).

**5. Oligocene to Pleistocene paleoecology of the Longzhong Basin indicated by mammalian faunas**

The taxonomic composition and faunal characteristics of mammals are highly responsive to environmental conditions (Li Y. et al., 2014; Sun et al., 2020). By examining the features and assemblages of animals from different periods, the living environments of the fauna can be used to reconstruct regional paleoecological variations (Koch and Barnosky, 2006). This has been extensively experimented in the Linxia Basin by previous studies that have attempted to unveil environmental shifts by analyzing the presence of animals in ecological habitats (Deng, 2005), cenograms of fossil mammals (Deng, 2009; Qiu Z.-D et al., 2023), evolutionary traits of individual species (Deng et al., 2023; Shi et al., 2023; Wang S. et al., 2023), and body size, diet, and locomotor patterns of fossil Carnivora (Jiangzuo et al., 2023). Mammalian occurrence percentages in woodland and grassland groups have also been used to reconstruct environmental changes in the Lanzhou Basin (Zhang P. et al., 2016, 2018). However, such qualitative and semi-quantitative reconstructions have not yet been applied to the combination of the Linxia, Lanzhou and Xining sub-basins. Combining these records will enable to explore longer time intervals with increased age resolution and to consider a higher diversity of fauna holding the potential to unravel a broader range of habitats (woodland, grassland or mixed environments) and the regional character of the observed patterns. We thus applied a semi-quantitative approach to reconstruct regional environmental changes over time by assigning each taxon in our comprehensive LB fossil fauna database an ecological score reflecting its associated vegetation type (Fortelius et al., 2014). This scoring approach follows methodologies similar to those used in previous studies to quantify paleoenvironmental and ecological changes (Köhler, 1993; Wu et al., 2022; Jiangzuo et al., 2023).

To establish a meaningful ecological framework, we define seven distinct environments that have existed in the LB since the Oligocene: forests, open woodlands, thickets, savannas, shrublands, grasslands, and steppes. These categories are based on well-established ecological
divisions observed in both modern and fossil mammal assemblages (e.g., Janis et al., 2000; Deng, 2005; Jung et al., 2020). Each environment is assigned a specific ecological score to reflect its structural complexity and vegetation cover: forests receive 5 points, woodlands and open woodlands receive 4 points, thickets and savannas receive 3 points, shrublands receive 2 points, and grasslands and steppes receive 1 point. These classifications are widely applied in paleoecological reconstructions and provide a robust framework for interpreting long-term environmental changes (Fortelius et al., 2014). To quantify past environments, we first assign each fossil species an ecological score based on published studies describing its habitat preferences. In cases where taxa exhibit broad habitat preferences, we assign a range of ecological scores to capture this variability, rather than a single fixed value. While no single species can define an entire environment, the aggregated ecological scores of all species within a fossil assemblage provide a robust reflection of local paleoenvironmental conditions. Detailed descriptions of each ecological setting, along with the corresponding scores and literature references, are provided in the supplementary materials.

To avoid significant differences in total scores generated by different mammalian faunas varying in the number of fossil species, we applied the average ecological score ($S_{name}$) using the following equation:

$$S_{name} = \frac{1}{n} \sum_{k=1}^{n} k$$

Here, n denotes the number of animal species within a faunal assemblage, and k represents the ecological score of a certain animal species within that mammalian fauna. The average ecological scores of each mammalian fauna were calculated and are presented in Table 1.

Most of the fauna presented average ecological scores between 2 and 4, except for the Diaogou fauna in the Xining Basin and the *Platybelodon* fauna in the Linxia Basin. The Diaogou fauna was dated to the Middle Miocene Climatic Optimum (MMCO) and had an average ecological score of 4.14±0.38, while the *Platybelodon* fauna had a value of 4.07±0.33 (Table 1). Notably, the Chetougou fauna has only two valid ecological scores. Therefore, in this study, the Chetougou fauna was temporarily excluded from the statistical averaging of the ecological scores. The average ecological scores of mammalian faunas were further examined with confidence intervals via a 5,000-bootstrap smoothing method with a 20% sliding window and a loess regression (local regression using weighted linear least squares and a second-degree polynomial model) employing Acycle v2.6 software (Li M. et al., 2019; Fig. 12).

The loess regression outcome suggested that the LB mainly exhibited an open environment during the late Oligocene, with significant forest expansion occurring after approximately 25 Ma (Fig. 12). Moreover, the ecological environment of the LB transformed into a forest environment during the Middle Miocene (Fig. 12). Following this, the forested area experienced periodic declines starting at approximately 14 Ma, evolving into a savannah or mixed woodland-grassland habitat in the Late Miocene and a steppe landscape during the Quaternary period (Fig. 12). These trends are generally consistent with previously published regional paleoenvironmental constraints from various environmental proxies applied to the studied sub-basins and the general regional environmental evolution interpreted from continental and marine records as compared in the next parts.
# 6. Comparison to environmental proxy records

## 6.1. Mammal fossil-based ecology from the Longzhong Basin region

Our semiquantitative reconstructions corroborate earlier ecological interpretations derived from qualitative assessments of mammalian fossil assemblages in both the Linxia Basin (e.g., Deng, 2005; Deng et al., 2013a, 2023) and the Lanzhou Basin (Zhang P. et al., 2016, 2018). Additionally, in the Linxia Basin, these reconstructions are supported by stable isotope analyses of δ¹³C and δ¹⁸O from rhinocerotoid tooth enamel (Biasatti et al., 2018), which provide detailed insights into environmental changes over geological time. Specifically, during the Late Oligocene, *Paraceratherium* exhibited remarkably low and stable δ¹⁸O values, whereas *Allacerops* showed higher and more variable δ¹⁸O and δ¹³C values, collectively indicative of an open, arid environment. In contrast, during the Middle Miocene, the low δ¹⁸O values and more negative δ¹³C values observed in *Alicornops* suggest the development of a more humid, open forest environment, while the progressively increasing δ¹⁸O values from the Late Miocene to the Pliocene reflect an evolutionary trend toward greater aridity (Biasatti et al., 2018). Complementary paleoenvironmental analyses of micromammal fossils by Qiu Z.-D. et al. (2023) indicate that the Linxia Basin transitioned gradually from relatively arid conditions to warm and humid climates between the Late Oligocene and the Middle Miocene, as evidenced by the increased abundance of moisture-adapted rodents and insectivores. By the Late Miocene, the appearance of arid-adapted groups such as Dipodidae and Ochotonidae further signifies the stepwise development of shrub-grassland conditions (Qiu Z.-D. et al., 2023).

In addition, our results are consistent with ecometric analyses on trait evolution in the *Hipparion* fauna spanning from approximately 12 Ma to 5.3 Ma in the Linxia Basin comprising at least eight species of *Hipparion* with different eras. Between ~12 Ma and ~5.3 Ma, the body size of *Hipparion* gradually increased, and the lateral toes of both the front and hind hooves became shorter and slimmer (Matthew, 1926; Zhang W.-L. et al., 2020). Horse teeth evolved from simple, low-crowned teeth suited for browsing soft vegetation to high-crowned teeth with complex ridges, better adapted for grinding tough grasses in response to dietary shifts driven by climatic changes (Liu, 2013; Bokor et al., 2016). Collectively, these diverse lines of evidence demonstrate that the ecosystem of the LB region underwent significant climatic fluctuations and vegetative structural changes, providing detailed insights into regional paleoclimatic dynamics and habitat transitions.

## 6.2. Pollen fossil-based ecology from the Longzhong Basin region

Sporopollen fossil records are also broadly consistent showing similar long-term trends but with significant differences. The percentages of shrub and herb pollen in the Xining Basin during the Oligocene-Early Miocene were approximately 40% (Long et al., 2011; Miao et al., 2013b), which was marginally lower than the percentages in the Linxia and Xunhua Basins during the same timeframe (50-70%) (Ma et al., 1998; Xu et al., 2015; Fig. 12). In the Xunhua Basin, the vegetation transitioned from sparse woodlands and grasslands (30-23 Ma) to mixed coniferous-broadleaf forests from 23.0-13.6 Ma including the MMCO, with a warm and humid climate (Xu, 2016). The vegetation shifted back to sparse shrub-grassland from 13.6 to 8.0 Ma, accompanied by a cooler and drier climate, and further developed into shrub-grassland by 8.2-5.8 Ma under
continued cooling (Xu et al., 2015). Similarly, in the Linxia Basin, vegetation transitioned from
sparse woodland-grassland from 30.6–21.8 Ma to forest from 21.8–8.5 Ma (Ma et al., 1998).

Following this period, the vegetation became dominated by grasslands from 8.5–6.0 Ma,
indicating significant climatic drying and cooling. In the Tianshui Basin, tree pollen percentages
reached 60% from 16–14 Ma but decreased significantly to less than 40% after 10.1 Ma, whereas
grass percentages increased to 60–80%, indicating a shift toward open grassland environments
(Hui et al., 2011; Liu et al., 2016). These pollen data collectively support a more nuanced
hypothesis: the LB likely experienced a transition from open woodland during the Oligocene–
Early Miocene to mixed forest environments in the Middle Miocene, followed by a shift to
savanna and steppe conditions starting in the Late Miocene. This conclusion is consistent with
broader regional trends generally observed in the Central Asian desert-steppe biome showing the
emergence of herb-dominated steppe starting to increase in humid habitats since the MMCO
followed by Plio–Pleistocene mammal turnovers attributed to increased climatic fluctuations,
glaciation events or seasonal and monsoonal variability affecting distributional ranges and genetic
diversity (Barbolini et al., 2020).

To support these regional ecological interpretations, we used the normalized difference vegetation index (NDVI), which reflects vegetation greenness and photosynthetic activity, and changes in the NDVI can thus provide information on the dynamics of vegetation growth and provide a means to monitor the impacts of climate change on ecosystems (Sun et al., 2013; Zewdie et al., 2017). Vegetation growth and ecological environment changes are mostly attributed to two dominant climatic factors, precipitation and temperature (Milich and Weiss, 2000; Sun et al., 2013). Furthermore, it is suggested that precipitation rather than temperature is the main factor affecting changes in the vegetation NDVI in arid and semiarid regions, particularly within the Tibetan Plateau (Sun et al., 2013). Precipitation today is mainly influenced by the modulation of westerly and monsoonal moisture sources modulated by topography and seasonal changes. The forcing factors significantly evolved through geologic times (see next part) but remained the main relevant drivers. We conducted an analysis of NDVI data from 2000 to 2020 in the region including the Longzhong Basin (Fig. 13). In most regions of our study area, the analysis indicated that precipitation accounted for more than 50% of the variation in the NDVI, as evidenced by the Pearson's correlation coefficients calculated at matching temporal and spatial scales for climate variables (temperature and precipitation) (Fig. 13). This strong pattern in arid environment appears to occur for different xerophytic taxa in modern as well as in Cenozoic biomes (Barbolini et al., 2020), suggesting that regional precipitation changes have been a major driver of vegetation cover changes over longer geological periods. Therefore, we interpret our reconstruction of regional ecological environment changes, which mainly reflect vegetation cover since the Oligocene, as being primarily influenced by regional precipitation changes.

**6.3. Comparison to regional climate evolution**

The Cenozoic precipitation and atmospheric moisture in the region have been mostly
transported by a combination of midlatitude westerlies in the winter and the East Asian summer
monsoon in the summer (Caves et al., 2015; Caves Ruggenstein et al., 2018; Chen et al., 2019;
Meijer et al., 2019). In the present day, it is estimated that the LB region received 70% of its precipitation from the East Asian Monsoon and 30% from the westerlies, according to the annual amount-weighted mean precipitation δ¹⁸O in the LB region and nearby areas and the precipitated carbonate δ¹⁸O of the late Quaternary loess in the Xining Basin (Yang et al., 2022). Previous studies from climate model and proxies estimate that in the region the westerlies contribution generally decreased and the monsoonal contribution increased from Oligocene to the Miocene (e.g., Tardif et al., 2023; Meijer et al., 2024). This evolution is consistent with the observed changes in the reconstructed ecological conditions based on fossil mammals, which broadly align with the sporopollen records (Fig. 12). Thus, we propose that the precipitation in the LB region experienced gradual strengthening from the late Oligocene to the Early Miocene and exhibited great intensification during the Middle Miocene mainly responding to East Asian monsoonal evolution, followed by a large periodic decrease from the late Middle Miocene to the Quaternary mainly in relation to global climate cooling. We compare this evolution to broader climate proxies below.

The slow increase in the forested component around 25 Ma is consistent with the East Asian summer monsoon expansion to the NETP during that period (Fig. 12), which was suggested by pollen records (Sun and Wang, 2005), the increase of aeolian deposits in northern China (Guo et al., 2002; Qiang et al., 2011), and multiple other paleoclimate proxy records (e.g., Guo et al., 2008; Wu et al., 2022). Monsoonal moisture records from the Xining Basin are suggested by abrupt concomitant increases in carbonate δ¹³C and δ¹⁸O during ~17–14 Ma and after 8 Ma, which are interpreted as increased seasonality and precipitation during the MMCO, followed by a decrease in the soil respiration rate within the distal alluvial fan/floodplain, indicating progressive aridification of the climate since the Late Miocene (Yang et al., 2022, Fig. 14b and c). Furthermore, our review of marine proxy records shows increasing monsoon-sourced dust into the Pacific since the MMCO followed by the Pliocene increase variability (Fig. 14). These are generally consistent with our fossil-based reconstructions showing a shift to dense forests during the Middle Miocene, followed by large declines in forested area leaving way to a savanna dominated habitat in the Late Miocene and a steppe landscape during the Quaternary period. Data from ODP Site 1148 in the northern South China Sea, which lies in the core area of the East Asian monsoon, indicate a trend in the chemical index of alteration (CIA) and elemental ratios such as Al/Ti, Al/Na, La/Sm, and Al/K (Wei et al., 2006). These proxies show a general declining trend from the Early Miocene to the Quaternary, with a reversal occurring between 17 and 15 Ma (Fig. 14f). This pattern suggests that the summer monsoon has weakened, whereas the winter monsoon has intensified since the Early Miocene (Wei et al., 2006; Fig. 14f). Clay mineral and Sr–Nd isotopic compositions from the West Pacific also revealed that the Asian interior was subjected to stepwise enhanced aridification during the Late Miocene (Tang et al., 2023), which was confirmed by a dramatic increase in the dust accumulation rate in the North Pacific Ocean (Zhang W.-F. et al., 2016; Fig. 14e).

Notably, the magnetic susceptibility of aeolian deposits in northern China is widely used as a proxy for tracking variability in East Asian summer monsoon precipitation (e.g., Deng et al., 2007; Qiang et al., 2011; Ao et al., 2016a). Magnetic susceptibility data from these deposits indicate a pronounced increase in pedogenesis and the in situ formation of fine-grained magnetic minerals, attributed to enhanced Asian summer monsoon precipitation during the MMCO (Qiang et al., 2011; Zhao et al., 2017; Fig. 14d). This pattern of enhanced precipitation persisted into the Late Miocene
(e.g., An et al., 2000; Sun et al., 2010; Ao et al., 2016a). In contrast, the magnetic susceptibility analyses of fluvio-lacustrine sediments in our study area revealed distinct environment conditions. During the MMCO, these sediments indicate a persistently waterlogged environment with poor drainage (Khan et al., 2023). Subsequently, during the Late Miocene, an increase in pedogenic intensity suggests a shift from anaerobic to aerobic conditions (Zan et al., 2018b). These changes in sedimentary conditions reflect a stepwise decrease in regional precipitation, associated with accelerated aridification in the NETP (Zan et al., 2018b). Furthermore, studies of Late Miocene aeolian red clay on the Chinese Loess Plateau (CLP) have revealed spatially variable magnetic susceptibility patterns, with lower values on the central CLP and higher values on both the eastern and western CLP (Wang X.-X. et al., 2022). The elevated magnetic susceptibility values in the western CLP during the Late Miocene may be attributed to an increased content of ultrafine ferrimagnetic grains from source regions. In contrast, the magnetic susceptibility in the eastern CLP is thought to more accurately reflect EASM intensity, indicating a weakened EASM during the Late Miocene (Wang X.-X. et al., 2022). This finding aligns with our fossil-based paleoenvironmental reconstruction.

The mechanisms underlying the reconstructed ecological conditions and associated monsoon precipitation changes in the LB since the Oligocene are complex and multifaceted. Modeling studies suggest that the evolution of the East Asian monsoon and the drying of inland Asia have been driven by an interplay of factors, including increasing continentality, orographic changes linked to the uplift of the Tibetan Plateau and adjacent mountain ranges, and reductions in pCO₂ levels (Zhang Z. et al., 2007; Licht et al., 2014; Zhang R. et al., 2017; Ao et al., 2021; Tardif et al., 2023; He et al., 2024). The Paratethys Sea began retreating westwards from the Tarim and Tajik Basins during the Eocene, eventually contracting into a salt lake around the Mediterranean region during the Late Miocene (Popov et al., 2004; Palcu et al., 2021). This retreat led to significant changes in continentality that influenced rainfall patterns in East Asia (Zhang et al., 2007; Meijer et al., 2019). However, sedimentary records indicate that its most significant impact was an aridification episode in inland Asia and the LB region during the Late Eocene (Bosboom et al., 2014b; Kaya et al., 2019; Meijer et al., 2019; Fang et al., 2022), predating the monsoon variability discussed in this study. In addition, modeling studies reveal that the Neogene retreat of the Paratethys Sea and the associated increase in land exposure could enhance summer precipitation in the core areas of both the South Asia and East Asia Monsoon domains, while also increasing aridification in the Asian inland regions north of 40° latitude, though with minor impact on the LB region (Tardif et al., 2023; Zhang J. et al., 2023). Global climate change, as evidenced by deep-sea δ¹⁸O isotope data (Westerhold et al., 2020) and variations in atmospheric pCO₂ levels (The Cenozoic CO₂ Proxy Integration Project Consortium, 2023), likely acted as a primary driver, particularly after the MMCO. This is closely associated with shifts in precipitation and ecological conditions in the LB region (Fig. 14). Remarkably, the notable expansion of forested areas in the LB beginning at approximately 25 Ma occurred without significant global warming (Fig. 14), suggesting that global climate change was a secondary factor. Geological evidence indicates that significant tectonic deformation events in the NETP, including the uplift of the Laji-Jishi Shan and the formation of sub-basins in the LB, occurred from 25–22 Ma, at ~15 Ma, and from 11–8 Ma.
Ma, closely corresponding to key ecological transitions (Fang et al., 2005; Lease et al., 2011; Xiao et al., 2012; Li J. et al., 2014, 2017; Wang W. et al., 2016; He et al., 2017; Saylor et al., 2018). These findings suggest that tectonic activity, superimposed on global climate change, primarily controlled the variability in East Asian summer monsoon precipitation. Variations in monsoon precipitation, in turn, regulated vegetation changes, which further influenced mammalian habitats and evolutionary trajectories. Based on these considerations, we propose in the following a schematic interpretation of the regional paleobiogeographic evolution since the Eocene to infer potential forcing factors for the observed changes.

# 7. Paleocological landscape evolution of the Longzhong Basin since the late Eocene

The Cenozoic uplift history of the NETP, along with global climate change, has significantly influenced regional monsoon precipitation patterns. These changes have profoundly shaped the landscape and ecological systems, subsequently affecting species evolution and biodiversity. Understanding regional paleocological landscape evolution is crucial for elucidating the interconnections among uplift, climate change, and biological evolution. Our reconstruction of ecological changes, combined with sedimentary facies, thermochronological, and provenance data, identified five stages in the paleocological landscape evolution of the LB since the late Eocene, accompanied by corresponding paleobiogeographic reconstructions of the region (Fig. 15).

## 7.1. The late Eocene

During the late Eocene, low-temperature thermochronological data suggest uplift in the West Qinling Shan and eastern Qilian Shan regions, resulting in relatively high topographic conditions (Clark et al., 2010; He et al., 2017; Zhang Y.-P. et al., 2020; Chen et al., 2021; Fig. 16a). Paleomagnetic data indicate that a 25° clockwise rotation of the Xining Basin relative to the stable Eurasian continent aligns with these uplift (Dupont-Nivet et al., 2008a). Fault gouge dating from the West Qinling Fault suggests that it was active approximately 50 ± 8 million years ago (Duvall et al., 2011), playing a significant role in controlling the basin's evolution. Eocene paleoelevation estimates are available from clumped isotope paleothermometry in the Xining Basin indicating temperature ranges similar to coeval coastal regions suggesting very low elevations compared to today (Page et al., 2019). Furthermore, significant topographic relief in surrounding mountainous areas is evident in the LB as shown by sedimentary facies and provenance data (Meijer et al., 2022). The detrital zircon U-Pb ages from the Xining, Linxia, and Lanzhou sub-basins suggest that the West Qinling Shan was the primary sediment source for the Xining and Linxi sub-basins (Zhang J., Wang et al., 2016; He et al., 2021; Licht et al., 2016; Feng et al., 2022a), while the eastern Qilian Shan supplied sediment primarily to the Lanzhou sub-basin (Wang W. et al., 2016). During this period, Linxia was characterized by a floodplain environment, while the Lanzhou-Xining region exhibited playa and mudflat conditions (Fig. 5).

The late Eocene vegetation was dominated by halophytic Nitrariaceae and xerophytic Ephedraceae, as indicated by pollen records from the Xining Basin (Barbolini et al., 2020) but the presence of arboreal species like *Picea* in the late Eocene further support the existence of surrounding upland areas although this will be prominent after drastic cooling at the Eocene-Oligocene transition (Dupont-Nivet et al., 2008b; Hoorn et al., 2012; Barbolini et al., 2020).

## 7.2. From the Eocene-Oligocene Transition to the Mid-Miocene Climatic Optimum

At the EOT, the basins' base levels generally sank, leading to the widespread disappearance
of lacustrine environments and the development of floodplains (Fig. 5). Climate model simulations for eastern Central Asia indicate a twofold increase in bare soil and a 20–50% rise in the NETP during this period (Barbolini et al., 2020). Over the EOT, palynological evidence indicates a marked increase in conifer density, likely originating from adjacent mountains, and a near disappearance of shrub species such as Nitrariaceae and Ephedraceae suggesting a reduction in vegetative cover in the Xining Basin until the Middle Miocene (Barbolini et al., 2020). This inference contrasts with the high proportion of shrubs and herbs in the Linxia Basin (Fig. 12), which implies that the elevations around the Linxia Basin were not high enough during the Eocene to yield sufficient conifer pollen to dominate the basin record. However, between approximately 25 and 20 Ma, the sharp decrease in herbs relative to conifers in the Linxia Basin (Ma et al., 1998) can be attributed to the combined effects of global cooling and regionally high elevations resulting from tectonic deformation.

Indeed, the LB's paleoecological landscape appears to have undergone significant transformation in the latest Oligocene to Early Miocene landscape, before the onset of the Mid-Miocene Climatic Optimum (MMCO). Apatite (U-Th)/He and fission-track thermochronology suggests that the West Qinling Shan and eastern Qilian Shan experienced accelerated exhumation starting in the Early Miocene (Lease et al., 2011; Pan et al., 2013; He et al., 2017; Li C. et al., 2024). This surface deformation is associated with the segmentation of the former LB and the development of multiple depositional centers, accompanied by widespread stratigraphic unconformities (Fan et al., 2019). Furthermore, subsidence began in neighboring regions, initiating the formation of the Xunhua, eastern Linxia, and Tianshui Basins, as evidenced by the ages of the oldest Cenozoic sediments in these basins (Fang et al., 2003; Lease et al., 2012; Liu et al., 2015; Sun et al., 2023; Wang X.-X. et al., 2023; Fig. 15b). These local topographic changes may account for the fluctuations and increased variability in the stable isotopic compositions of authigenic carbonates from the Xining Basin, which were modulated by regional Asian monsoon activity between 26 and 24 Ma in the NETP (Yang et al., 2022). During this interval, active deformation triggered variations in sediment supply, as evidenced by significant changes in sedimentation rates (Xiao et al., 2012; Lease et al., 2012), which likely in turn led to dramatic shifts in the extent of the basin's water bodies. Consequently, isotopic fractionation may have been further enhanced through increased evaporative enrichment during episodes of East Asian summer monsoon rainfall that were characterized by negative $δ^{18}$O signatures.

In terms of mammalian fauna, a significant faunal turnover may have coincided with the EOT shifts in vegetation across Central Asia, known as "Mongolian Remodeling" (Meng and McKenna, 1998). This period was marked by the replacement of the Eocene's moderately sized, perissodactyl-dominant mammals with a diverse array of rodents and lagomorphs during the Oligocene (Kraatz and Geisler, 2010; Wasiljeff et al., 2020). In the Longzhong Basin, however, the EOT impact on mammals is obscured by the near lack of mammalian fossils reported from the Eocene and early Oligocene. Younger deposits yield a rich record of rodents and lagomorphs starting ca. 31 Ma that were prevalent during the late Oligocene to Early Miocene. These species exhibit high hypsodonty levels, an adaptation to grit-laden or fibrous vegetation, indicative of decreased primary productivity within a seasonally arid and/or cold climate (Strömberg, 2011; Fortelius et al., 2014; Barbolini et al., 2020). This is consistent with a post-EOT shift in the Longzhong Basin toward relatively cooler, drier conditions, persisting during the late Oligocene. This shift potentially resulted from the transition from a planetary wind-dominated climate to a
monsoon-arid regime in Asia (Sun and Wang, 2005; Guo et al., 2008; Wu et al., 2022). The late
Oligocene mammal appearance in the Longzhong Basin remains open for discussion. A bias from
preservation of depositional environments seems unlikely given the broad range of lithologic
compositions of Eocene to Oligocene strata across the sub-basins. Climate proxies through the
Oligocene indicate no major shifts or trends in temperature or precipitation (Page et al., 2019; Fig.
14). The late Oligocene appearance may thus rather be linked to xerophitic adaptation and
associated dispersals across Eurasia, in particular after 31 Ma (Mennecart et al., 2021).

**7.3. The Middle Miocene**

During the Middle Miocene, the Longzhong Basin experienced significant deformation. Provenance evidence, such as detrital zircon U-Pb ages and paleocurrents suggest pronounced uplift of the Laji Shan, leading to the formation of the Xining, Xunhua, and Guide sub-basins (Fang et al., 2005; Lease et al., 2012; Liu et al., 2013; Fig. 15c). South of the Laji Shan-Maxian Shan, extensive lakes have developed, while floodplain environments prevailed to the north (Figs. 5 and 16c). The Laji Shan became the primary sediment source for the sub-basins, resulting in increased sedimentation rates (Lease et al., 2011, 2012; Xiao et al., 2012). Globally, the MMCO (~17–15 Ma) is characterized by temperatures 3–8 °C higher than preindustrial levels (You et al., 2009; Pound et al., 2012; Holbourn et al., 2015). In East Asia, East Asian summer monsoon (EASM) precipitation has increased significantly. This is evidenced over a broad region by the presence of *Lotus* megafossils and increased palynomorphs (*Fupingopollenites*) in the Qaidam Basin (Miao et al., 2016; Luo et al., 2022), weakened pedogenesis in the LB region due to strongly waterlogged environments (Zan et al., 2015; Khan et al., 2023), and the characteristics of iron oxides and magnesium isotopes from the Chinese Loess Plateau (Zhao et al., 2020; Ma et al., 2022). Additionally, intensified physical erosion and chemical weathering in the South China Sea have been observed (Clift et al., 2014). In the LB region, the MMCO is marked in pollen records by a shift to dominating temperate, warm-temperate broad-leaved forests with a sharp increase in sub-tropical assemblages (Ma et al., 1998; Hui et al., 2011). Yet, the preserved extended range of taxa with different ecologic characteristics (*Piceae*, *Abies*, *Quercus*, *Ulmus*, and *Betula*) potentially suggest pronounced vertical zonation in the LB region, corroborated by intense tectonic activity and paleoelevation reconstructions. A recent pollen-based paleoaltimetry indicator support that the NETP likely obtained its current or higher elevation in the Late Miocene (Miao et al., 2022). Pollen records also suggest the spread of herb-dominated steppe in Central Asia around the MMCO interpreted to relate in part to enhanced monsoonal seasonality (Barbolini et al., 2020). Mammalian evolution during this period resulted in increased species diversity, notably the proliferation of large genera, compared to the Early Miocene. Taxa such as Proboscidea, squirrels, *Anchitherium*, Rhinocerotoidea, *Kubanochoerus*, and *Palaeotragus* thrived (Deng, 2016; Deng et al., 2023; Qiu Z.-D. and Li, 2023; Wang S. et al., 2023). Animals with low-crowned teeth, adapted to browsing on soft twigs, tender leaves, or fruits, indicate forest ecosystem habitats (Deng, 2016).

This evolutionary trajectory is closely linked to global warming during the MMCO and increased EASM precipitation, while the observed diversity is consistent with concurrent orogenic uplift that promoted altitudinal vegetation zonation together with increased monsoonal seasonality (Favre et al., 2015; Müllner-Rhiel, 2019).

**7.4. The Late Miocene to Pliocene**

From the Late Miocene to the Pliocene, extensive evidences, including detrital zircon U-Pb
ages, peneplain disintegration patterns, low-temperature thermochronological data, and
sedimentation rate variations, indicates that the Laji Shan, Jishi Shan, Maxian Shan, and surrounding areas underwent further accelerated uplift (Lease et al., 2007, 2011; Hough et al., 2011; Li J. et al., 2014, 2017; Ma et al., 2020; Wang W. et al., 2020). This tectonic activity ultimately transformed these ranges into dominant sediment sources for adjacent sub-basins and led to the separation of the Xunhua, Linxia, Lanzhou, and Tianshui sub-basins, ultimately establishing their current topographic distribution (Hough et al., 2011; Lease et al., 2011, 2012; Li J. et al., 2017; Fig. 15d). Concurrently, these processes fostered the development of thrust-fold belts, growth strata, and unconformities in the LB region (Li J. et al., 2014). The increased erosion of these mountains significantly increased sedimentation rates in the sub-basins, giving rise to alluvial braided river systems at the mountain fronts and floodplains in the basin centers (Li J. et al., 2014; Fang et al., 2016).

Although the stepwise uplift of the NETP has regulated surface processes in the LB region during the Late Miocene, the influence of climatic factors should not be underestimated. After the lush times of the MMCO, East Asia appears to have experienced significant long-term cooling, aridification and increased variability (e.g., Tardif et al., 2023). This trend is evident from decreased moisture and temperature, inferred from megafloras, microfloristic plants, and pollen analyses (Miao et al., 2012); a reduction in chemical weathering (Ren et al., 2020); and positive shifts in δ¹⁸O and δ¹³C values in pedogenic carbonates (Yang et al., 2022; Zhuang et al., 2011). Additionally, there has been an accumulation of aeolian red clay on floodplains and remnant planation surfaces (Li J. et al., 2017; Ma et al., 2020; Zhang R. et al., 2021). Climate simulations suggest that the Late Miocene to Pliocene aridification in inland Asia correlated with the intensification of the East Asian winter monsoon, which was possibly caused by the uplift of the NETP, the Tian Shan, and the Mongolian Plateau (Zhang R. et al., 2017; Sha et al., 2020; Tardif et al., 2023). Interestingly, a relatively open and subarid grassland/steppe environment emerged in the LB region since the MMCO, culminating with the expansion and dominance of grasses and other herbs at ~7 Ma (Barbolini et al., 2020). This period also saw an increase in the frequency and intensity of fire activity (Miao et al., 2019; Hui et al., 2021b) and an increase in the mean C₄ plant abundance (Hui et al., 2021b) across both western and eastern Central Asia. The causes of the Late Miocene expansion of C₄ vegetation in Central Asia remain unclear. However, this expansion coincided with the global proliferation of C₄ plants and likely had significant impacts on mammalian evolution such as the increase in the body size of *Hipparion* (Fortelius et al., 2014). In the LB region, during the Late Miocene, mammalian clades underwent considerable diversification, with numerous new species emerging (Deng et al., 2013a, 2019). Myomorpha became the dominant group within Rodentia, while families such as Eomyidae and Gliridae faced a decline or extinction by the Late Miocene. Cricetidae replaced the Mid-Miocene Cricetodontidae and, alongside the Muridae family, diversified substantially, showing notable increases in species diversity and population. The number of Proboscidea species significantly decreased, while *Hipparion* and *Chilotherium* became dominant within Perissodactyla. Increased topography and relief combined with increased seasonality, generally cooler conditions and the emergence of C₄ plants appears to have been a strong driver for mammal speciation, a trend that continued to its extreme in the Quaternary.

**7.5. The Quaternary**

Since the onset of the Quaternary period, Earth has experienced significant climatic changes characterized by global cooling. The expansion of polar ice sheets and glacier development in the
Tibetan Plateau underscore this shift toward colder conditions (e.g., Miller et al., 2005; Knies et al., 2014; Chen et al., 2018). This climatic transition profoundly influences the geomorphology and ecosystems of various regions, including the formation and expansion of major deserts in the northern Tibetan Plateau, such as the Gobi, Badain Jaran, and Tengger (Li Z. et al., 2014; Wang F. et al., 2015; Lu et al., 2019). The deposition of loess in northern China, including the LB region, also increased significantly during this period (Zan et al., 2016; Zhang J., Li et al., 2016; Guo et al., 2020).

In the LB region, another pivotal event was the development of the Yellow River drainage pattern. Based on paleomagnetic dating of loess-paleosol complexes, the Yellow River drainage formed the oldest erosion surface level in the Lanzhou and Linxia Basins at approximately 1.7 Ma (Pan et al., 2009; Li J. et al., 2014). It is suggested to have later carved its way upstream through bedrock mountains and sediments of the Xunhua Basin at approximately 1.2 Ma, reaching the Gonghe Basin by approximately 0.15 Ma (Li J. et al., 1997b, 2014; Fig. 15e). The eastern Qilian Shan appears to have been incorporated into the Yellow River catchment area, with the modern Datong and Huangshui River valleys established between 1.5 and 1.1 Ma (Zhang W.-L. et al., 2017; Feng et al., 2022b).

Quaternary cooling and the resulting environmental changes have had profound impacts on biology (Qiu Z.-X., 2006). Mammalian and plant species faced significant evolutionary pressures, leading to broader grassland development and the expansion of cold habitats for ice-age megafauna, such as the woolly rhino (*Coelodonta*) (Deng, 2002; Deng et al., 2011b).

## 8. Summary and future directions

We revised the magnetostratigraphic ages of mammalian fossil faunas from the Oligocene onward in three sub-basins of the LB within the NETP, namely the Lanzhou, Xining, and Linxia Basins. In addition, we compiled published records of mammalian taxa from these sub-basins and assigned corresponding ecological scores based on the paleoenvironments in which each species resided. This approach enabled a semi-quantitative estimation of the habitats associated with the identified faunas. The results indicate an open woodland environment during the Oligocene to Early Miocene, which gradually transitioned into a dense forest reaching its apex during the MMCO, followed by the progressive expansion and predominance of savanna and steppe ecosystems into the Quaternary. To validate our semi-quantitative reconstructions of the paleoecological environments, we compared them with a compilation of local terrestrial paleoenvironmental proxies and employed modern NDVI analyses to assess vegetation-precipitation correlations. Utilizing these reconstructions, along with sedimentary facies, provenance data, and sedimentation rates, we reconstructed the regional evolution of the paleoecological landscape since the late Eocene. Our reconstruction demonstrates a correlation with both terrestrial and marine proxies that indicate the intensity of regional monsoonal precipitation.

Although the present review advances the understanding of Cenozoic sedimentary chronologies, ecological changes, and landscape evolution in the NETP, it also identifies areas requiring further investigation to elucidate the interrelationships among regional tectonics, climate, and biotic evolution. The relatively low resolution of mammalian fossil records, despite high-resolution stratigraphic dating, confines the analysis to long-term trends that may relate to progressive abiotic changes such as orogeny or long-term climate shifts. Shorter-term events such
as the Eocene Oligocene transition, hyperthermal events or the onset of the MMCO, which are
well documented in pollen records (Barbolini et al., 2020), necessitate higher-resolution
mammalian records to fully assess their impact on biodiversity. This resolution may be achieved in
the LB through systematic exploration, particularly of micromammal assemblages (as documented
in the Linxia Basin; Qiu Z.-D. et al., 2023) in key stratigraphic intervals that have been well
characterized by the existing chronological and palynological frameworks. Another promising
avenue of exploration with high potential in the LB is the systematic analysis of isotopic
compositions of mammal teeth that would provide valuable average environmental information
(Biasatti et al., 2018), in particular following the frontier work performed in the Linxia Basin
micomammals (Qiu Z.-D. et al., 2023). Moreover, the paleo-landscape and paleo-ecologic data we
produced with the provided well dated mammal records serve as essential frameworks for the
application of biotic dispersal models (Hagen et al., 2021). Such models could test various
regional or local scenarios of biodiversity against the provided mammal records. For example,
previous research indicated that the ages of the *Hipparion* and *Platybelodon* faunas in the Linxia
Basin decrease progressively from the basin center toward its margins (Zhang W.-L. et al., 2019).
However, the underlying mechanism driving this trend remain unclear. Coeval mountain building
around the Linxia Basin may have played a significant role by increasing the availability of
diverse physiographic niches, thereby offering a range of micro- and mesoclimatic conditions
(Badgley et al., 2017). On a regional scale, the LB holds substantial potential for further testing
the relative influences of tectonic and climatic forces on biotic evolution. This can be achieved by
examining changes in well-dated local records against global climatic events such as the MMCO
(Barbolini et al., 2020; Zhou et al., 2023; Wang J. 2024) or the mountain-building episodes of the
surrounding Liupan Shan, Qilian Shan, Laji Shan, Maxian Shan, and Qinling Shan (e.g., Zheng et
al., 2006; Lease et al., 2011; Wang W. et al., 2020; Han et al., 2024; Li C. et al., 2024). Combined
landscape evolution and focused climate models with plant functional types are applicable to the
LB well-defined context to decipher climatic from tectonic drivers.

Finally, this study highlights the notable absence of mammalian fossils in Eocene strata and
their subsequent sudden abundance, diversification, and persistence following the Eocene-
Oligocene transition in the LB. Comparable nearby regions, such as Inner Mongolia, contain
abundant Eocene mammalian assemblages, including well-established type localities and
taxonomically diverse fossil records (Wasiljeff et al., 2020). Preservation bias or differences in
fossil collection are unlikely explanations given the similarity in lithologies and the extent of
paleontological investigations in Eocene versus Oligocene strata (Qiu Z.-X. et al., 1997; Fang et
al., 2019; Meijer et al., 2019). Long-term tectonic changes are also an improbable cause, given the
rapidity of the transition, which is more likely attributable to concomitant climatic shifts at the
Eocene–Oligocene transition. This transition is characterized by cooling, aridification, and a
dramatic change in vegetation and plant cover. In the region, the transition is also associated with
increased seasonal variability in precipitation (Page et al., 2019). Although the Eocene conditions
appear to have been more favorable for mammalian habitation compared to the Oligocene, the
exceptionally high temperatures recorded in the LB during the Eocene, as indicated by Δ47
clumped isotope data (Page et al., 2019; Meijer et al., 2024), likely exceeded the thermal
tolerances of most mammals, particularly larger taxa. These high temperatures may have inhibited
the dispersal of mammals in the LB until significant cooling and increased seasonality in the
Oligocene facilitated their establishment in parts of the basin. More generally, the presence of
large mammals, some of which the largest to ever roam continents, in such arid regions at this
time remains a mystery requiring further investigation. These extreme environmental conditions
may have pre-adapted Asian taxa, contributing to phenomena such as the "Mongolian
Remodeling" (Meng and McKenna, 1998; Kraatz and Geisler, 2010) during the Eocene–Oligocene
transition and possibly influencing the Grande Coupure in Europe (Mennecart et al., 2018). How
these large-scale biotic events are connected to the concurrent appearance of mammals in the LB
remains to be determined. Future research that combines Earth System models with multiple
well-dated proxies and comprehensive mammalian records from the Paleogene dispersal and
turnover events in the LB and adjacent regions is expected to provide critical insights into these
continental-scale dispersal phenomena.

Acknowledgments

This research was co-supported by the National Key Research and Development Program of China (grant no. 2022YFF0800502), the National Natural Science Foundation of China (grant nos. 42302121), the Second Tibetan Plateau Scientific Expedition and Research Grant (grant no. 2019QZKK0707). G. Dupont-Nivet acknowledges support from the ANR grant TIBETOP. Tingjiang Peng and Zhenhua Ma are thanked for their fieldwork assistance.

References

Abels, H.A., Dupont-Nivet, G., Xiao, G., Bosboom, R. and Krijgsman, W., 2011. Step-wise change of Asian interior climate preceding the Eocene–Oligocene Transition (EOT). Palaeogeography, Palaeoclimatology, Palaeoecology. 299, 399-412. https://doi.org/10.1016/j.palaeo.2010.11.028.

An, Z., Sun, D., Chen, M., Sun, Y., Li, L. and Chen, B., 2000. Red clay sequences in Chinese Loess Plateau and recorded paleoclimate events of the late Tertiary. Quaternary Sciences. 20, 435-446 (in Chinese with English abstract). https://doi.org/10.3321/j.issn:1001-7410.2000.05.004.

Antoine, P.-O., Ducrocq, S., Marivaux, L., Chaimanee, Y., Crochet, J.-Y., Jaeger, J.-J. and Welcomme, J.-L., 2003. Early rhinocerotids (Mammalia: Perissodactyla) from South Asia and a review of the Holárctic Paleogene rhinocerotid record. Canadian Journal of Earth Sciences. 40, 365-374. https://doi.org/10.1139/e02-101.

Ao, H., Dupont-Nivet, G., Rohling, E.J., Zhang, P., Ladant, J.-B., Roberts, A.P., Licht, A., Liu, Q., Liu, Z., Dekkers, M.J., Coxall, H.K., Jin, Z., Huang, C., Xiao, G., Poulsen, C.J., Barbolini, N., Meijer, N., Sun, Q., Qiang, X., Yao, J. and An, Z., 2020. Orbital climate variability on the northeastern Tibetan Plateau across the Eocene–Oligocene transition. Nature Communications. 11, 5249. https://doi.org/10.1038/s41467-020-18824-8.

Ao, H., Liebrand, D., Dekkers, M.J., Zhang, P., Song, Y., Liu, Q., Jonell, T.N., Sun, Q., Li, X., Li, X., Qiang, X. and An, Z., 2021. Eccentricity-paced monsoon variability on the northeastern Tibetan Plateau in the Late Oligocene high CO₂ world. Science Advances. 7, eabk2318. https://doi.org/10.1126/sciadv.abk2318.

Ao, H., Roberts, A.P., Dekkers, M.J., Liu, X., Rohling, E.J., Shi, Z., An, Z. and Zhao, X., 2016a. Late Miocene–Pliocene Asian monsoon intensification linked to Antarctic ice-sheet growth. Earth and Planetary Science Letters. 444, 75-87. https://doi.org/10.1016/j.epsl.2016.03.028.

Ao, H., Zhang, P., Dekkers, M.J., Roberts, A.P., An, Z., Li, Y., Lu, F., Lin, S. and Li, X., 2016b. New magnetochronology of Late Miocene mammal fauna, NE Tibetan Plateau, China: Mammal migration and paleoenvironments. *Earth and Planetary Science Letters*. 434, 220-230. https://doi.org/10.1016/j.epsl.2015.11.019.

Badgley, C., Smiley, T.M., Terry, R., Davis, E.B., DeSantis, L.R.G., Fox, D.L., Hopkins, S.S.B., Jezkova, T., Matocq, M.D., Matzke, N., McGuire, J.L., Mulch, A., Riddle, B.R., Roth, V.L., Samuels, J.X., Strömberg,
C.A.E. and Yanites, B.J., 2017. Biodiversity and Topographic Complexity: Modern and Geohistorical Perspectives. Trends in Ecology & Evolution. 32, 211-226. https://doi.org/10.1016/j.tree.2016.12.010.

Barbolini, N., Woutersen, A., Dupont-Nivet, G., Silvestro, D., Tardif, D., Coster, P.M.C., Meijer, N., Chang, C., Zhang, H.-X., Licht, A., Rydin, C., Koutsodendris, A., Han, F., Rohrmann, A., Liu, X.-J., Zhang, Y., Donnadieu, Y., Fluteau, F., Ladant, J.-B., Le Hir, G. and Hoorn, C., 2020. Cenozoic evolution of the steppe-desert biome in Central Asia. Science Advances. 6, eabb8227. https://doi.org/10.1126/sciadv.abb8227.

Biasatti, D., Wang, Y. and Deng, T., 2018. Paleoecology of Cenozoic rhinos from northwest China: a stable isotope perspective. Vertebrata Palasiatica. 56, 45-68. https://doi.org/10.19615/j.cnki.1000-3118.170519.

Bokor, J., Broo, J. and Mahoney, J., 2016. Using Fossil Teeth to Study the Evolution of Horses in Response to a Changing Climate. The American Biology Teacher. 78, 166-169. https://doi.org/10.1525/abt.2016.78.2.166.

Bosboom, R.E., Abels, H.A., Hoorn, C., van den Berg, B.C.J., Guo, Z. and Dupont-Nivet, G., 2014a. Aridification in continental Asia after the Middle Eocene Climatic Optimum (MECO). Earth and Planetary Science Letters. 389, 34-42. https://doi.org/10.1016/j.epsl.2013.12.014.

Bosboom, R., Dupont-Nivet, G., Grothe, A., Brinkhuis, H., Villa, G., Mandic, O., Stoica, M., Kouwenhoven, T., Huang, W., Yang, W. and Guo, Z., 2014b. Timing, cause and impact of the late Eocene stepwise sea retreat from the Tarim Basin (west China). Palaeogeography, Palaeoclimatology, Palaeoecology. 403, 101-118. https://doi.org/10.1016/j.palaeo.2014.03.035.

Caves, J.K., Winnick, M.J., Graham, S.A., Sjostrom, D.J., Mulch, A. and Chamberlain, C.P., 2015. Role of the westerlies in Central Asia climate over the Cenozoic. Earth and Planetary Science Letters. 428, 33-43. https://doi.org/10.1016/j.epsl.2015.07.023.

Caves Rugenstein, J.K. and Chamberlain, C.P., 2018. The evolution of hydroclimate in Asia over the Cenozoic: A stable-isotope perspective. Earth-Science Reviews. 185, 1129-1156. https://doi.org/10.1016/j.earscirev.2018.09.003.

Chen, F., Chen, J., Huang, W., Chen, S., Huang, X., Jin, L., Jia, J., Zhang, X., An, C., Zhang, J., Zhao, Y., Yu, Z., Zhang, R., Liu, J., Zhou, A. and Feng, S., 2019. Westerlies Asia and monsoonal Asia: Spatiotemporal differences in climate change and possible mechanisms on decadal to sub-orbital timescales. Earth-Science Reviews. 192, 337-354. https://doi.org/10.1016/j.earscirev.2019.03.005.

Chen, H., Fang, X., Li, J. and Kang, S., 1996. Fission track dating of Cenozoic strata in Linxia Basin. Nuclear Techniques. 19, 632-634 (in Chinese with English abstract).

Chen, L., Song, C., Wang, Y., Fang, X., Zhang, Y., Zhang, J., Chen, Y. and He, P., 2021. Mesozoic–Cenozoic Uplift/Exhumation History of the Qilian Shan, NE Tibetan Plateau: Constraints From Low-Temperature Thermochronology. Frontiers in Earth Science. 9, 760100. https://doi.org/10.3389/feart.2021.760100.

Chen, Y., Li, Y., Zhang, M., Cui, Z. and Liu, G., 2018. Much late onset of Quaternary glaciations on the Tibetan Plateau: determining the age of the Shishapangma Glaciation using cosmogenic $^{26}$Al and $^{10}$Be dating. Science Bulletin. 63, 306-313. https://doi.org/10.1016/j.scib.2018.01.020.

Chiu, C.S., 1973. A new genus of giant rhinoceros from Oligocene of Dzungaria, Sinkiang. Vertebrata Palasiatica. 11, 182-191 (in Chinese with English abstract). https://doi.org/10.19615/j.cnki.1000-3118.1973.02.008.

Clark, M.K., Farley, K.A., Zheng, D., Wang, Z. and Duvall, A.R., 2010. Early Cenozoic faulting of the northern Tibetan Plateau margin from apatite (U–Th)/He ages. Earth and Planetary Science Letters. 296, 78-88. https://doi.org/10.1016/j.epsl.2010.04.051.

Clift, P.D., Wan, S. and Blusztajn, J., 2014. Reconstructing chemical weathering, physical erosion and monsoon intensity since 25Ma in the northern South China Sea: A review of competing proxies. Earth-Science Reviews. 130, 86-102. https://doi.org/10.1016/j.earscirev.2014.01.002.

The Cenozoic CO$_2$ Proxy Integration Project Consortium, 2023. Toward a Cenozoic history of atmospheric CO$_2$.
Science. 382, eadi5177. https://doi.org/10.1126/science.adi5177.

Dai, S., Fang, X., Dupont-Nivet, G., Song, C., Gao, J., Krijgsman, W., Langereis, C. and Zhang, W., 2006. Magnetostratigraphy of Cenozoic sediments from the Xining Basin: Tectonic implications for the northeastern Tibetan Plateau. Journal of Geophysical Research: Solid Earth. 111, B11. https://doi.org/10.1029/2005JB004187.

Deng, C., Liu, Q., Pan, Y. and Zhu, R., 2007. Environmental magnetism of Chinese loess-paleosol sequences. Quaternary Sciences. 27, 193-209 (in Chinese with English abstract). https://doi.org/10.3321/j.issn:1001-7410.2007.02.005.

Deng, C., Zhu, R., Zhang, R., Ao, H. and Pan, Y., 2008. Timing of the Nihewan formation and faunas. Quaternary Research. 69, 77-90. https://doi.org/10.1016/j.yqres.2007.10.006.

Deng, T., 2002. The earliest known wooly rhino discovered in the Linxia basin, Gansu Province, China. Geological Bulletin of China. 21, 604-608 (in Chinese with English abstract). https://doi.org/10.3969/j.issn.1671-2552.2002.10.002.

Deng, T., 2003. New material of Hispanotherium matritense (Rhinocerotidae, Perissodactyla) from Laogou of Hezheng County (Gansu, China), with special reference to the Chinese Middle Miocene elasmotheres. Geobios. 36, 141-150. https://doi.org/10.1016/S0016-6995(03)00003-2.

Deng, T., 2005. Character, Age and Ecology of the Hezheng Biota from Northwestern China. Acta Geologica Sinica - English Edition. 79, 739-750. https://doi.org/10.1111/j.1755-6724.2005.tb00927.x.

Deng, T., 2009. Late Cenozoic environmental changes in the Linxia Basin (Gansu, China) as indicated by cenograms of fossil mammals. Vertebrata Palasiatica. 47, 282-298. https://doi.org/10.19615/j.cnki.1000-3118.2009.04.003.

Deng, T., 2016. Records and characteristics of the mammalian faunas of Northern China in the Middle Miocene Climatic Optimum. Quaternary Sciences. 36, 810-819 (in Chinese with English abstract). https://doi.org/10.11928/j.issn.1001-7410.2016.04.003.

Deng, T., Hou, S. and Wang, S., 2019. Neogene integrative stratigraphy and timescale of China. Science China Earth Sciences. 62, 310-323. https://doi.org/10.1007/s11430-017-9155-4.

Deng, T., Hou, S., Xie, G., Wang, S., Shi, Q., Chen, S., Sun, B. and Lu, X., 2013b. Chronostratigraphic subdivision and correlation of the upper Miocene of the Linxia Basin in Gansu, China. Journal of Stratigraphy. 37, 417-427. https://doi.org/10.19839/j.cnki.dcxzz.2013.04.004.

Deng, T., Lu, X., Sun, D. and Li, S., 2023. Rhinocerotoid fossils of the Linxia Basin in northwestern China as late Cenozoic biostratigraphic markers. Palaeogeography, Palaeoclimatology, Palaeoecology. 614, 111427. https://doi.org/10.1016/j.palaeo.2023.111427.

Deng, T., Lu, X., Wang, S., Flynn, L.J., Sun, D., He, W. and Chen, S., 2021. An Oligocene giant rhino provides insights into Paraceratherium evolution. Communications Biology. 4, 639. https://doi.org/10.1038/s42003-021-02170-6.

Deng, T., Qiu, Z., Wang, B., Wang, X. and Hou, S., 2013a. Late Cenozoic biostratigraphy of the Linxia basin, northwestern China, in: X. Wang, L.J. Flynn and M. Fortelius (Eds.), Fossil Mammals of Asia: Neogene Biostratigraphy and Chronology. Columbia University Press, New York, pp. 243-273.

Deng, T., Wang, W. and Yue, L., 2006. The Xiejian stage of the continental Miocene series in China. Journal of Stratigraphy. 30, 315-322 (in Chinese with English abstract). https://doi.org/10.3969/j.issn.0253-4959.2006.04.003.

Deng, T., Wang, X., Fortelius, M., Li, Q., Wang, Y., Tseng, Z.J., Takeuchi, G.T., Saylor, J.E., Säilä, L.K. and Xie, G., 2011. Out of Tibet: Pliocene Woolly Rhino Suggests High-Plateau Origin of Ice Age Megaherbivores. Science. 333, 1285-1288. https://doi.org/10.1126/science.1206594.
Deng, T., Wang, X., Ni, X. and Liu, L., 2004. Sequence of the Cenozoic Mammalian Faunas of the Linxia Basin in Gansu, China. *Acta Geologica Sinica* - English Edition. 78, 8-14. https://doi.org/10.1111/j.1755-6724.2004.tb00669.x.

Dong, Y., Sun, S., Santosh, M., Zhao, J., Sun, J., He, D., Shi, X., Hui, B., Cheng, C. and Zhang, G., 2021. Central China Orogenic Belt and amalgamation of East Asian continents. *Gondwana Research*. 100, 131-194. https://doi.org/10.1016/j.gr.2021.03.006.

Dupont-Nivet, G., Dai, S., Fang, X., Krijgsman, W., Erens, V., Reitsma, M. and Langereis, C., 2008a. Timing and distribution of tectonic rotations in the northeastern Tibetan Plateau. Investigations into the Tectonics of the Tibetan Plateau. 444, 73-87. https://doi.org/10.1130/2008.2444(05).

Dupont-Nivet, G., Hoorn, C. and Konert, M., 2008b. Tibetan uplift prior to the Eocene-Oligocene climate transition: Evidence from pollen analysis of the Xining Basin. *Geology*. 36, 987-990. https://doi.org/10.1130/g25063a.1.

Dupont-Nivet, G., Krijgsman, W., Langereis, C.G., Abels, H.A., Dai, S. and Fang, X., 2007. Tibetan plateau aridification linked to global cooling at the Eocene–Oligocene transition. *Nature*. 445, 635-638. https://doi.org/10.1038/nature05516.

Duvall, A.R., Clark, M.K., van der Pluijm, B.A. and Li, C., 2011. Direct dating of Eocene reverse faulting in northeastern Tibet using Ar-dating of fault clays and low-temperature thermochronometry. *Earth and Planetary Science Letters*. 304, 520-526. https://doi.org/10.1016/j.epsl.2011.02.028.

Fan, L., Meng, Q., Wu, G., Wei, H., Du, Z. and Wang, E., 2019. Paleogene crustal extension in the eastern segment of the NE Tibetan plateau. *Earth and Planetary Science Letters*. 514, 62-74. https://doi.org/10.1016/j.epsl.2019.02.036.

Fang, X., Fang, Y., Zan, J., Zhang, W., Song, C., Appel, E., Meng, Q., Miao, Y., Dai, S., Lu, Y. and Zhang, T., 2019. Cenozoic magnetostratigraphy of the Xining Basin, NE Tibetan Plateau, and its constraints on paleontological, sedimentological and tectonomorphological evolution. *Earth-Science Reviews*. 190, 460-485. https://doi.org/10.1016/j.earscirev.2019.01.021.

Fang, X., Garzione, C., Van der Voo, R., Li, J. and Fan, M., 2003. Flexural subsidence by 29 Ma on the NE edge of Tibet from the magnetostratigraphy of Linxia Basin, China. *Earth and Planetary Science Letters*. 210, 545-560. https://doi.org/10.1016/s0012-821x(03)00142-0.

Fang, X., Guo, Z., Jiang, D., Zhang, W., Zhang, R., Li, M., Wang, Y., Zhang, T. and Miao, Y., 2022. No monsoon-dominated climate in northern subtropical Asia before 35 Ma. *Global and Planetary Change*. 218, 103970. https://doi.org/10.1016/j.gloplacha.2022.103970.

Fang, X., Li, J., Zhu, J., Chen, H. and Cao, J., 1997. Absolute age and separation of Cenozoic strata from the Linxia Basin, Gansu. *Chinese Science Bulletin*. 42, 1457-1471 (in Chinese). https://doi.org/10.1360/csb1997-42-14-1457.

Fang, X., Song, C., Dai, S., Zhu, Y., Gao, J. and Zhang, W., 2007. Cenozoic deformation and uplift of the NE Qinghai Tibet Plateau: evidence from high-resolution magnetostratigraphy and basin evolution. *Earth Science Frontiers*. 14, 230-242 (in Chinese with English abstract). https://doi.org/10.3321/j.issn:1005-2321.2007.01.022.

Fang, X., Wang, J., Zhang, W., Zan, J., Song, C., Yan, M., Appel, E., Zhang, T., Wu, F., Yang, Y. and Lu, Y., 2016. Tectonosedimentary evolution model of an intracontinental flexural (foreland) basin for paleoclimatic research. *Global and Planetary Change*. 145, 78-97. https://doi.org/10.1016/j.gloplacha.2016.08.015.

Fang, X., Yan, M., Van der Voo, R., Rea, D.K., Song, C., Parés, J.M., Gao, J., Nie, J. and Dai, S., 2005. Late Cenozoic deformation and uplift of the NE Tibetan Plateau: Evidence from high-resolution magnetostratigraphy of the Guide Basin, Qinghai Province, China. *GSA Bulletin*. 117, 1208-1225.
https://doi.org/10.1130/b25727.1.

Favre, A., Päckert, M., Pauls, S.U., Jähnig, S.C., Uhl, D., Michalak, I. and Muellner-Riehl, A.N., 2015. The role of the uplift of the Qinghai-Tibetan Plateau for the evolution of Tibetan biotas. Biological Reviews. 90, 236-253.
https://doi.org/10.1111/brv.12107.

Feng, Z., Peng, T., Ma, Z., Han, B., Wang, H., Guo, B., Zhao, Z., Zhang, J., Song, C. and Hu, Z., 2022b. Contrasting responses of rivers with different sizes to extrinsic changes in the northeastern Tibetan Plateau. Journal of Asian Earth Sciences. 233, 105269. https://doi.org/10.1016/j.jseaes.2022.105269.

Feng, Z., Zhang, W., Fang, X., Zan, J., Zhang, T., Song, C. and Yan, M., 2022a. Eocene deformation of the NE Tibetan Plateau: Indications from magnetostratigraphic constraints on the oldest sedimentary sequence in the Linxia Basin. Gondwana Research. 101, 77-93. https://doi.org/10.1016/j.gr.2021.07.027.

Flynn, L.J., Wang, X., Downs, W., Opdyke, N., Huang, K., Lindsay, E., Ye, J. and Xie, G., 1999. Recent Advances in the Small Mammal Biostratigraphy and Magnetostratigraphy of Lanzhou Basin. Chinese Science Bulletin. 44, 105-118. https://doi.org/10.1360/sb1999-44-S1-105.

Fortelius, M., Eronen, J.T., Kaya, F., Tang, H., Raia, P. and Puolamäki, K., 2014. Evolution of Neogene Mammals in Eurasia: Environmental Forcing and Biotic Interactions. Annual Review of Earth and Planetary Sciences. 42, 579-604. https://doi.org/10.1146/annurev-earth-050212-124030.

Fu, C., Qiang, X., Xu, X., Xi, J., Zuo, J. and An, Z., 2017. Late Miocene magnetostratigraphy of Jianzha Basin in the northeastern margin of the Tibetan Plateau and changes in the East Asian summer monsoon. Geological Journal. 53, 282-292. https://doi.org/10.1002/gj.3047.

Gao, J., Shi, Y., Zhang, H., Chen, X., Zhang, W., Shen, W., Xiao, T. and Zhang, Y., 2024. China Regional 250m Fractional Vegetation Cover Data Set (2000-2023). National Tibetan Plateau Data Center: Beijing, China. https://doi.org/10.11888/Terre.tpdc.300330.

GPBGMR (Gansu Provincial Bureau of Geology and Mineral Resources), 1997. Stratigraphy (Lithostratic) of Gansu Province. China University of Geosciences Press, Wuhan.

Gradstein, F.M., Ogg, J.G., Schmitz, M.B. and Ogg, G.M., 2012. The geologic time scale 2012. Elsevier.

Guo, B., Liu, S., Peng, T., Ma, Z., Feng, Z., Li, M., Li, X., Li, J., Song, C., Zhao, Z., Pan, B., Stockli, D.F. and Nie, J., 2018. Late Pliocene establishment of exorheic drainage in the northeastern Tibetan Plateau as evidenced by the Wuquan Formation in the Lanzhou Basin. Geomorphology. 303, 271-283.
https://doi.org/10.1016/j geomorph.2017.12.009.

Guo, B., Peng, T., Yu, H., Hui, Z., Ma, Z., Li, X., Feng, Z., Liu, J., Liu, S. and Zhang, J., 2020. Magnetostratigraphy and Palaeoclimatic Significance of the Late Pliocene Red Clay-Quaternary Loess Sequence in the Lanzhou Basin, Western Chinese Loess Plateau. Geophysical Research Letters. 47, e2019GL086556. https://doi.org/10.1029/2019GL086556.

Guo, Z.T., Ruddiman, W.F., Hao, Q.Z., Wu, H.B., Qiao, Y.S., Zhu, R.X., Peng, S.Z., Wei, J.J., Yuan, B.Y. and Liu, T.S., 2002. Onset of Asian desertification by 22 Myr ago inferred from loess deposits in China. Nature. 416, 159-163. https://doi.org/10.1038/416159a.

Guo, Z.T., Sun, B., Zhang, Z.S., Peng, S.Z., Xiao, G.Q., Ge, J.Y., Hao, Q.Z., Qiao, Y.S., Liang, M.Y., Liu, J.F., Yin, Q.Z. and Wei, J.J., 2008. A major reorganization of Asian climate by the early Miocene. Climate of the Past. 4, 153-174. https://doi.org/10.5194/cp-4-153-2008.

Hagen, O., Flück, B., Fopp, F., Cabral, J.S., Hartig, F., Pontarp, M., Rangel, T.F. and Pellissier, L., 2021. *gen3sis*: A general engine for eco-evolutionary simulations of the processes that shape Earth's biodiversity. Plos Biology. 19, e3001340. https://doi.org/10.1371/journal.pbio.3001340.
Han, B., Peng, T., Han, C., Liu, Z., Li, X., Ma, Z., Feng, Z., Li, M., Zhou, A. and Song, C., 2024. Biomarkers Indicate Pliocene Uplift of the Maxian Mountains, Northeastern Tibetan Plateau. Geochemistry, Geophysics, Geosystems. 25, e2023GC011401. https://doi.org/10.1029/2023GC011401.

Han, J., Shao, Z., Chen, Q., Meng, X., Zhu, D., Zhang, Q., Quan, K., Wang, J. and Xu, B., 2015. Discovery and Significance of Hipparion and Parelasmotherium Fossils in the Xining Basin, Qinghai Province. Acta Geoscientica Sinica. 36, 115-120 (in Chinese with English abstract). https://doi.org/10.3975/cagsb.2015.01.14.

Han, J., Shao, Z., Yu, J., Wang, J., Zhang, Q., Meng, X. and Zhu, D., 2021. Discovery of Late Miocene Testudo fossil in the Xining Basin of Qinghai Province, China and its significance. Geology in China. 48, 1292-1293 (in Chinese). https://doi.org/10.12029/gc20210423.

He, C., Zhang, Y., Li, S., Wang, K. and Ji, J., 2021. Magnetostratigraphic study of a Late Cretaceous–Paleogene succession in the eastern Xining basin, NE Tibet: Constraint on the timing of major tectonic events in response to the India-Eurasia collision. GSA Bulletin. 133, 2457-2484. https://doi.org/10.1130/b35874.1.

He, L., Zhou, T., Guo, Z., Zuo, M., Ren, Z., Chen, X., Wu, B., Zou, L., Zhang, L., Man, W. and Jiang, J., 2024. Northward Extension of East Asian Summer Monsoon Since the Miocene Set by the Uplift of Tibetan Plateau. Geophysical Research Letters. 51, e2023GL107262. https://doi.org/10.1029/2023GL107262.

He, P., Wang, X., Song, C., Wang, Q., Deng, L. and Zhong, S., 2017. Cenozoic evolution of the Western Qinling Mt. Range based on thermochronologic and sedimentary records from the Wudu Basin, NE Tibetan Plateau. Journal of Asian Earth Sciences. 138, 484-494. https://doi.org/10.1016/j.jseaes.2017.02.033.

Holbourn, A., Kuhnt, W., Kochhann, K.G.D., Andersen, N. and Sebastian Meier, K.J., 2015. Global perturbation of the carbon cycle at the onset of the Miocene Climatic Optimum. Geology. 43, 123-126. https://doi.org/10.1130/g36317.1.

Hoorn, C., Straathof, J., Abels, H.A., Xu, Y., Utescher, T. and Dupont-Nivet, G., 2012. A late Eocene palynological record of climate change and Tibetan Plateau uplift (Xining Basin, China). Palaeogeography, Palaeoclimatology, Palaeoecology. 344-345, 16-38. https://doi.org/10.1016/j.palaeo.2012.05.011.

Hopwood, A.T., 1935. Fossil Proboscidea from China. Palaeontologia Sinica, Ser. C. 9, 1-85.

Horton, B.K., Dupont-Nivet, G., Zhou, J., Waanders, G.L., Butler, R.F. and Wang, J., 2004. Mesozoic-Cenozoic evolution of the Xining-Minhe and Dangchang basins, northeastern Tibetan Plateau: Magnetostratigraphic and biostratigraphic results. Journal of Geophysical Research: Solid Earth. 109, B04402. https://doi.org/10.1029/2003jb002913.

Hou, S. and Zhang, Y., 2023. A biostratigraphic and palaeoecological study of Late Cenozoic kubanochoeres from the Linxia Basin, Gansu Province, China. Palaeogeography, Palaeoclimatology, Palaeoecology. 623, 111633. https://doi.org/10.1016/j.palaeo.2023.111633.

Hough, B.G., Garzione, C.N., Wang, Z., Lease, R.O., Burbank, D.W. and Yuan, D., 2011. Stable isotope evidence for topographic growth and basin segmentation: Implications for the evolution of the NE Tibetan Plateau. GSA Bulletin. 123, 168-185. https://doi.org/10.1130/b30090.1.

Hui, Z., Gowan, E.J., Hou, Z., Zhou, X., Ma, Y., Guo, Z. and Zhang, J., 2021b. Intensified fire activity induced by aridification facilitated Late Miocene C4 plant expansion in the northeastern Tibetan Plateau, China. Palaeogeography, Palaeoclimatology, Palaeoecology. 573, 110437. https://doi.org/10.1016/j.palaeo.2021.110437.

Hui, Z., Li, J., Xu, Q., Song, C., Zhang, J., Wu, F. and Zhao, Z., 2011. Miocene vegetation and climatic changes reconstructed from a sporopollen record of the Tianshui Basin, NE Tibetan Plateau. Palaeogeography, Palaeoclimatology, Palaeoecology. 308, 373-382. https://doi.org/10.1016/j.palaeo.2011.05.043.

Hui, Z., Liu, J., Chevalier, M., Wei, X., Chen, P., Zhang, J., Peng, T. and Zhou, X., 2023. Multiple forcing on Late
Miocene East Asian Summer Monsoon Precipitation Variability in NE Tibetan Plateau. Catena. 221, 106752.
https://doi.org/10.1016/j.catena.2022.106752.

Hui, Z., Ran, M., Li, H., Liu, C., Guo, B., Zhang, J., Peng, T., Liu, D. and Pan, Y., 2021c. Early Pleistocene pollen record from the western Chinese Loess Plateau and its implications for the evolution of the East Asian Summer Monsoon. *Science of The Total Environment*. 761, 143304.
https://doi.org/10.1016/j.scitotenv.2020.143304.

Hui, Z., Zhou, X., Chevalier, M., Wei, X., Pan, Y. and Chen, Y., 2021a. Miocene East Asia summer monsoon precipitation variability and its possible driving forces. *Palaeogeography, Palaeoclimatology, Palaeoecology*. 581, 110609. https://doi.org/10.1016/j.palaeo.2021.110609.

Janis, C.M., Damuth, J. and Theodor, J.M., 2000. Miocene ungulates and terrestrial primary productivity: where have all the browsers gone? *Proceedings of the National Academy of Sciences*. 97, 7899-904.
https://doi.org/10.1073/pnas.97.14.7899.

Ji, J., Zhang, K., Qiang, T., Kou, X., Chen, F., Xu, Y., Lu, J. and Lin, Q., 2010. Magnetostratigraphy of the Neogene Strata in Xunhua Basin, Qinghai Province. *Earth Science-Journal of China University of Geosciences*. 35, 803-810 (in Chinese with English abstract). https://doi.org/10.3799/dqkx.2010.093.

Jiangzuo, Q., Niu, K., Li, S., Fu, J. and Wang, S., 2022. A Diverse Metailurine Guild from the Latest Miocene Xingjiawan Fauna, Yongdeng, Northwestern China, and Generic Differentiation of Metailurine Felids. *Journal of Mammalian Evolution*. 29, 845-862. https://doi.org/10.1007/s10914-022-09622-8.

Jiangzuo, Q., Wang, S. and Deng, T., 2023. Chronological framework and palaeoecology of Carnivora from the Linxia Basin, China. *Palaeogeography, Palaeoclimatology, Palaeoecology*. 615, 111463.
https://doi.org/10.1016/j.palaeo.2023.111463.

Jung, M., Dahal, P.R., Butchart, S.H.M., Donald, P.F., De Lamo, X., Lesiv, M., Kapos, V., Rondinini, C. and Visconti, P., 2020. A global map of terrestrial habitat types. *Scientific Data*. 7, 256.
https://doi.org/10.1038/s41597-020-00599-8.

Kaya, M.Y., Dupont-Nivet, G., Proust, J.-N., Roperch, P., Bougeois, L., Meijer, N., Frieling, J., Fioroni, C., Özkan Altıner, S., Vardar, E., Barbolini, N., Stoica, M., Aminov, J., Mamtimin, M. and Zhaojie, G., 2019. Paleogene evolution and demise of the proto-Paratethys Sea in Central Asia (Tarim and Tajik basins): Role of intensified tectonic activity at ca. 41 Ma. *Basin Research*. 31, 461-486. https://doi.org/10.1111/bre.12330.

Khan, A.A., Zan, J., Fang, X., Zhang, W. and Jadoon, U.F., 2023. Global warming drove the Mid-Miocene climate humidification in the northern Tibetan Plateau. *Global and Planetary Change*. 226, 104135.
https://doi.org/10.1016/j.gloplacha.2023.104135.

Knies, J., Cabedo-Sanz, P., Belt, S.T., Baranwal, S., Fietz, S. and Rosell-Melé, A., 2014. The emergence of modern sea ice cover in the Arctic Ocean. *Nature Communications*. 5, 5608. https://doi.org/10.1038/ncomms6608.

Koch, P.L. and Barnosky, A.D., 2006. Late Quaternary Extinctions: State of the Debate. *Annual Review of Ecology, Evolution, and Systematics*. 37, 215-250. https://doi.org/10.1146/annurev.ecolsys.34.011802.132415.

Köhler, M., 1993. Skeleton and habitat of recent and fossil ruminants. *Münchner Geowissenschaftliche Abhandlungen*, 25, 1-88.

Kraatz, B.P. and Geisler, J.H., 2010. Eocene–Oligocene transition in Central Asia and its effects on mammalian evolution. *Geology*. 38, 111-114. https://doi.org/10.1130/g30619.1.

Lease, R.O., Burbank, D.W., Clark, M.K., Farley, K.A., Zheng, D. and Zhang, H., 2011. Middle Miocene reorganization of deformation along the northeastern Tibetan Plateau. *Geology*. 39, 359-362.
https://doi.org/10.1130/g31356.1.

Lease, R.O., Burbank, D.W., Gehrels, G.E., Wang, Z. and Yuan, D., 2007. Signatures of mountain building:
Detrital zircon U/Pb ages from northeastern Tibet. Geology. 35, 239-242. https://doi.org/10.1130/g23057a.1.

Lease, R.O., Burbank, D.W., Hough, B., Wang, Z. and Yuan, D., 2012. Pulsed Miocene range growth in northeastern Tibet: Insights from Xunhua Basin magnetostratigraphy and provenance. Geological Society of America Bulletin. 124, 657-677. https://doi.org/10.1130/b30524.1.

Li, C.-K. and Qiu, Z.-D., 1980. Early Miocene mammalian fossils of Xining Basin, Qinghai. Vertebrata PalAsiatica. 18, 198-210. https://doi.org/10.19615/j.cnki.1000-3118.1980.03.004.

Li, C.-K., Qiu, Z.-D. and Wang, S.-J., 1981. Discussion on Miocene stratigraphy and mammals from Xining Basin, Qinghai. Vertebrata PalAsiatica. 19, 313-320 (in Chinese with English abstract). https://doi.org/10.19615/j.cnki.1000-3118.1981.04.003.

Li, C.-K., Wu, W.-Y. and Qiu, Z.-D., 1984. Chinese Neogene: subdivision and correlation. Vertebrata PalAsiatica. 22, 163-178. https://doi.org/10.19615/j.cnki.1000-3118.1984.03.001.

Li, C.-X., Wang, S.-Q., Hao, C.-L., Chen, G.-L., Sun, B.-Y., Zheng, Y. and Si-Jian, X., 2018. A textual research of the early localities of fossil Gomphotherium in the Xining Basin with relevant stratigraphic correlation. Journal of Stratigraphy. 42, 313-324 (in Chinese with English abstract). https://doi.org/10.19839/j.cnki.dcxzz.2018.03.007.

Li, C., Zheng, D., Yu, J., Lease, R.O., Wang, Y., Pang, J., Wang, Y., Hao, Y. and Xu, Y.-G., 2024. Revised timing of rapid exhumation in the West Qinling: Implications for geodynamics of Oligocene-Miocene Tibetan plateau outward expansion. Earth and Planetary Science Letters. 646, 118966. https://doi.org/10.1016/j.epsl.2024.118966.

Li, J., Fang, X., Song, C., Pan, B., Ma, Y. and Yan, M., 2014. Late Miocene–Quaternary rapid stepwise uplift of the NE Tibetan Plateau and its effects on climatic and environmental changes. Quaternary Research. 81, 400-423. https://doi.org/10.1016/j.yqres.2014.01.002.

Li, J., Fang, X., Van der Voo, R., Zhu, J., Mac Niocaill, C., Cao, J., Zhong, W., Chen, H., Wang, J., Wang, J. and Zhang, Y., 1997a. Late Cenozoic magnetostratigraphy (11-0 Ma) of the Dongshanding and Wangjiashan sections in the Longzhong Basin, western China. Geologie en Mijnbouw. 76, 121-134. https://doi.org/10.1023/A:1003153717799.

Li, J., Fang, X., Van der Voo, R., Zhu, J., Niocaill, C.M., Ono, Y., Pan, B., Zhong, W., Wang, J. and Sasaki, T., 1997b. Magnetostratigraphic dating of river terraces: Rapid and intermittent incision by the Yellow River of the northeastern margin of the Tibetan Plateau during the Quaternary. Journal of Geophysical Research: Solid Earth. 102, 10121-10132. https://doi.org/10.1029/97JB00275.

Li, J., Feng, Z. and Tang, L., 1988. Late quaternary monsoon patterns on the Loess Plateau of China. Earth Surface Processes and Landforms. 13, 125-135. https://doi.org/10.1002/esp.3290130204.

Li, J., Ma, Z., Li, X., Peng, T., Guo, B., Zhang, J., Song, C., Liu, J., Hui, Z., Yu, H., Ye, X., Liu, S. and Wang, X., 2017. Late Miocene-Pliocene geomorphological evolution of the Xiaoshuizi penplain in the Maxian Mountains and its tectonic significance for the northeastern Tibetan Plateau. Geomorphology. 295, 393-405. https://doi.org/10.1016/j geomorph.2017.07.024.

Li, J., Zhang, J., Song, C., Zhao, Z., Zhang, Y., Wang, X., Zhang, J. and Cui, Q., 2006. Miocene Bahean stratigraphy in the Longzhong Basin, northern central China and its implications in environmental change. Science in China Series D: Earth Sciences. 49, 1270-1279. https://doi.org/10.1007/s11430-006-2057-y.

Li, M., Hinnov, L. and Kump, L., 2019. Acycle: Time-series analysis software for paleoclimate research and education. Computers & Geosciences. 127, 12-22. https://doi.org/10.1016/j.cageo.2019.02.011.

Li, Y., Wang, S. and Deng, T., 2023. Age of Xingjiawan mammalian assemblage revealed by new Cervidae and Bovidae material from Yongdeng, Gansu Province, China. Historical Biology. 37, 76-86. https://doi.org/10.1080/08912963.2023.2286513.
Li, Y., Zhang, Y., Wu, X., Ao, H., Li, L. and An, Z., 2014b. Mammalian Evolution in Asia Linked to Climate Changes, in: Z. An (Ed.), Late Cenozoic Climate Change in Asia: Loess, Monsoon and Monsoon-arid Environment Evolution. Springer Netherlands, Dordrecht, pp. 435-490.

Li, Z., Sun, D., Chen, F., Wang, F., Zhang, Y., Guo, F., Wang, X. and Li, B., 2014. Chronology and paleoenvironmental records of a drill core in the central Tengger Desert of China. Quaternary Science Reviews. 85, 85-98. https://doi.org/10.1016/j.quascirev.2013.12.003.

Licht, A., Dupont-Nivet, G., Pullen, A., Kapp, P., Abels, H.A., Lai, Z., Guo, Z., Abell, J. and Giesler, D., 2016. Resilience of the Asian atmospheric circulation shown by Paleogene dust provenance. Nature Communications. 7, 12390. http://dx.doi.org/10.1038/ncomms12390.

Licht, A., van Cappelle, M., Abels, H.A., Ladant, J.B., Trabucho-Alexandre, J., France-Lanord, C., Donnadieu, Y., Vandenberghe, J., Rigaudier, T., Lécuyer, C., Terry Jr, D., Adriaens, R., Boura, A., Guo, Z., Soe, A.N., Quade, J., Dupont-Nivet, G. and Jaeger, J.J., 2014. Asian monsoons in a late Eocene greenhouse world. Nature. 513, 501-506. https://doi.org/10.1038/nature13704.

Liu, J., Li, J.J., Song, C.H., Yu, H., Peng, T.J., Hui, Z.C. and Ye, X.Y., 2016. Palynological evidence for late Miocene stepwise aridification on the northeastern Tibetan Plateau. Clim. Past. 12, 1473-1484. https://doi.org/10.5194/cp-12-1473-2016.

Liu, M., 1992. Stratigraphic sequence and fossil assemblage of Neogene system in Xining-Minhe Basin. Qinghai Geology. 2, 1-18 (in Chinese).

Liu, P., Zhang, S., Han, J. and Liu, T., 2008. Paleomagnetic chronology of quaternary stratigraphy of the Longdan section in Gansu province of China. Quaternary Science. 28, 796-805 (in Chinese with English abstract). https://doi.org/10.3321/j.issn:1001-7410.2008.05.002.

Liu, S., Li, J., Stockli, D.F., Song, C., Nie, J., Peng, T., Wang, X., He, K., Hui, Z. and Zhang, J., 2015. Late Tertiary reorganizations of deformation in northeastern Tibet constrained by stratigraphy and provenance data from eastern Longzhong Basin. Journal of Geophysical Research: Solid Earth. 120, 5804-5821. https://doi.org/10.1002/2015jb011949.

Liu, S., Zhang, G., Pan, F., Zhang, H., Wang, P., Wang, K. and Wang, Y., 2013. Timing of Xunhua and Guide basin development and growth of the northeastern Tibetan Plateau, China. Basin Research. 25, 74-96. https://doi.org/10.1111/j.1365-2117.2012.00548.x.

Liu, Y., 2013. Late Miocene Hipparionine fossils from Lantian, Shaanxi Province and phylogenetic analysis on Chinese Hipparionines, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, 1-128 pp (in Chinese with English abstract).

Liu, Y., Yang, Y., Feng, Z., Yan, Z., Yue, Y., Wu, F., Song, B. and Fang, X., 2024. Neogene drainage reorganization of Longzhong Basin driven by growth of the northeastern Tibetan Plateau: A Sr isotope hydrological perspective. Basin Research. 36, e12828. https://doi.org/10.1111/bre.12828.

Long, L., Fang, X., Miao, Y., Bai, Y. and Wang, Y., 2011. Northern Tibetan Plateau cooling and aridification linked to Cenozoic global cooling: Evidence from n-alkane distributions of Paleogene sedimentary sequences in the Xining Basin. Chinese Science Bulletin. 56, 1569. https://doi.org/10.1007/s11434-011-4469-0.

Lu, H., Wang, X., Wang, X., Chang, X., Zhang, H., Xu, Z., Zhang, W., Wei, H., Zhang, X., Yi, S., Zhang, W., Feng, H., Wang, Y., Wang, Y. and Han, Z., 2019. Formation and evolution of Gobi Desert in central and eastern Asia. Earth-Science Reviews. 194, 251-263. https://doi.org/10.1016/j.earscirev.2019.04.014.

Lucas, S.G. and Bayashov, B.U., 1996. The giant rhinoceros Paraceratherium from the late Oligocene at Aktau Mountain, southeastern Kazakhstan, and its biochronological significance. Neues Jahrbuch für Geologie und Paläontologie-Monatshefte. 9, 539-548. https://doi.org/10.1127/njgpm/1996/1996/539.

Luo, M., Jia, H., Li, Q., Meng, X., Ferguson, D.K., Liu, P., Han, Z., Wang, J. and Quan, C., 2022. Middle Miocene
lotus (Nelumbonaceae, Nelumbo) from the Qaidam Basin, Northern Tibet Plateau. Biology. 11, 1261.
https://doi.org/10.3390/biology11091261.

Ma, L., Sun, Y., Jin, Z., Bao, Z., Yuan, H., Zhang, P. and Huang, K.-J., 2022. Magnesium isotopic evidence for staged enhancement of the East Asian Summer Monsoon precipitation since the Miocene. Geochimica et Cosmochimica Acta. 324, 140-155. https://doi.org/10.1016/j.gca.2022.03.005.

Ma, Y., Li, J. and Fang, X., 1998. A record of polynoflora and climatic evolution of Red Bed between 30.6 to 5.0 Ma BP, Linxia Basin. Chinese Science Bulletin. 43, 301-304 (in Chinese).
https://doi.org/10.1360/csb1998-43-3-301.

Ma, Z., Li, X., Peng, T., Zhang, J., Dou, L., Yu, H., Liu, J., Ye, X., Feng, Z., Li, M., Guo, B., Song, C., Zhao, Z. and Li, J., 2020. Landscape evolution of the Dabanshan planation surface: Implications for the uplift of the eastern tip of the Qilian Mountains since the Late Miocene. Geomorphology. 356, 107091.
https://doi.org/10.1016/j geomorph.2020.107091.

Ma, Z., Peng, T., Li, X., Feng, Z., Guo, B., Li, M., Zhang, J. and Song, C., 2021. Evolution of the main planation surfaces in the Longzhong Basin and its surrounding areas and its significance for the uplift of the Tibetan Plateau. Journal of Glaciology and Geocryology. 43, 827-840.
https://doi.org/10.7522/j.issn.1000-0240.2021.0024.

Matthew, W.D., 1926. The evolution of the horse: a record and its interpretation. Quarterly Review of Biology. 1, 139-185. https://doi.org/10.1086/394242.

Meijer, N., Dupont-Nivet, G., Abels, H.A., Kaya, M.Y., Licht, A., Xiao, M., Zhang, Y., Roperch, P., Poujol, M., Lai, Z. and Guo, Z., 2019. Central Asian moisture modulated by proto-Paratethys Sea incursions since the early Eocene. Earth and Planetary Science Letters. 510, 73-84. https://doi.org/10.1016/j.epsl.2018.12.031.

Meijer, N., Dupont-Nivet, G., Barbolini, N., Woutersen, A., Rohrmann, A., Zhang, Y., Liu, X.-J., Licht, A., Abels, H.A., Hoorn, C., Tjallingii, R., Andermann, C., Dietze, M. and Nowaczyk, N., 2021. Loess-Like Dust Appearance at 40 Ma in Central China. Paleooceanography and Paleoclimatology. 36, e2020PA003993.
https://doi.org/10.1029/2020PA003993.

Meijer, N., Dupont-Nivet, G., Licht, A., Roperch, P., Rohrmann, A., Sun, A., Lu, S., Woutersen, A. and Nowaczyk, N., 2022. Early Eocene magnetostratigraphy and tectonic evolution of the Xining Basin, NE Tibet. Basin Research. 35, 510-529. https://doi.org/10.1111/bre.12720.

Meijer, N., Licht, A., Woutersen, A., Hoorn, C., Robin-Champigneul, F., Rohrmann, A., Tagliavento, M., Brugger, J., Kelemen, F.D., Schauer, A.J., Hren, M.T., Sun, A., Fiebig, J., Mulch, A. and Dupont-Nivet, G., 2024. Proto-monsoon rainfall and greening in Central Asia due to extreme early Eocene warmth. Nature Geoscience. 17, 158-164. http://dx.doi.org/10.1038/s41561-023-01371-4.

Meng, J. and McKenna, M.C., 1998. Faunal turnovers of Palaeogene mammals from the Mongolian Plateau. Nature. 394, 364-367. https://doi.org/10.1038/28603.

Meng, J., Ye, J., Wu, W., Ni, X. and Bi, S., 2013. A Single-Point Base Definition of the Xiejian Age as an Exemplar for Refining Chinese Land Mammal Ages, in: X. Wang, L.J. Flynn and M. Fortelius (Eds.), Fossil Mammals of Asia: Neogene Biostratigraphy and Chronology. Columbia University Press, New York, pp. 124-141.

Mennecart, B., Aiglstorfer, M., Li, Y., Li, C. and Wang, S., 2021. Ruminants reveal Eocene Asiatic palaeobiogeographical provinces as the origin of diachronous mammalian Oligocene dispersals into Europe. Scientific Reports. 11, 17710. http://dx.doi.org/10.1038/s41598-021-96221-x.

Mennecart, B., Geraads, D., Spassov, N. and Zagorchev, I., 2018. Discovery of the oldest European ruminant in the late Eocene of Bulgaria: Did tectonics influence the diachronic development of the Grande Coupure? Palaeogeography, Palaeoclimatology, Palaeoecology. 498, 1-8. https://doi.org/10.1016/j.palaeo.2018.01.011.
Miao, Y., Fang, X., Song, C., Yan, X., Xu, L. and Chen, C., 2013b. Pollen and fossil wood's linkage with Mi-1 Glaciation in northeastern Tibetan Plateau, China. Palaeoworld. 22, 101-108. https://doi.org/10.1016/j.palwor.2013.06.001.

Miao, Y., Fang, X., Sun, J., Xiao, W., Yang, Y., Wang, X., Farnsworth, A., Huang, K., Ren, Y., Wu, F., Qiao, Q., Zhang, W., Meng, Q., Yan, X., Zheng, Z., Song, C. and Utescher, T., 2022. A new biologic paleoaltimetry indicating Late Miocene rapid uplift of northern Tibet Plateau. Science. 378, 1074-1079. https://doi.org/10.1126/science.abo2475.

Miao, Y., Herrmann, M., Wu, F., Yan, X. and Yang, S., 2012. What controlled Mid–Late Miocene long-term aridification in Central Asia? — Global cooling or Tibetan Plateau uplift: A review. Earth-Science Reviews. 112, 155-172. https://doi.org/10.1016/j.earscirev.2012.02.003.

Miao, Y., Song, C., Fang, X., Meng, Q., Zhang, P., Wu, F. and Yan, X., 2016. Late Cenozoic genus Fupingopollenites development and its implications for the Asian summer monsoon evolution. Gondwana Research. 29, 320-333. https://doi.org/10.1016/j.gr.2014.12.007.

Miao, Y., Wu, F., Herrmann, M., Yan, X. and Meng, Q., 2013a. Late early Oligocene East Asian summer monsoon in the NE Tibetan Plateau: Evidence from a palynological record from the Lanzhou Basin, China. Journal of Asian Earth Sciences. 75, 46-57. https://doi.org/10.1016/j.jseaes.2013.07.003.

Miao, Y., Wu, F., Warny, S., Fang, X., Lu, H., Fu, B., Song, C., Yan, X., Escarguel, G., Yang, Y., Meng, Q. and Shi, P., 2019. Miocene fire intensification linked to continuous aridification on the Tibetan Plateau. Geology. 47, 303-307. https://doi.org/10.1130/g45720.1.

Milich, L. and Weiss, E., 2000. GAC NDVI images: Relationship to rainfall and potential evaporation in the grazing lands of The Gourma (northern Sahel) and in the croplands of the Niger-Nigeria border (southern Sahel). International Journal of Remote Sensing. 21, 261-280. https://doi.org/10.1080/014311600210821.

Miller, K.G., Kominz, M.A., Browning, J.V., Wright, J.D., Mountain, G.S., Katz, M.E., Sugarman, P.J., Cramer, B.S., Christie-Blick, N. and Pekar, S.F., 2005. The Phanerozoic Record of Global Sea-Level Change. Science. 310, 1293-1298. https://doi.org/10.1126/science.1116412.

Muellner-Riehl, A.N., 2019. Mountains as Evolutionary Arenas: Patterns, Emerging Approaches, Paradigm Shifts, and Their Implications for Plant Phylogeographic Research in the Tibeto-Himalayan Region. Frontiers in Plant Science. 10. http://dx.doi.org/10.3389/fpls.2019.00195.

Nie, J., Garzione, C., Su, Q., Liu, Q., Zhang, R., Heslop, D., Necula, C., Zhang, S., Song, Y. and Luo, Z., 2017. Dominant 100,000-year precipitation cyclicity in a late Miocene lake from northeast Tibet. Science Advances. 3, e1600762. https://doi.org/10.1126/sciadv.1600762.

Opdyke, N.D., Flynn, L.J., Lindsay, E.H. and Qiu, Z.X., 1998. The magnetic stratigraphy of the Yehucheng and Xianshuihe Formations of Oligocene–Miocene age near Lanzhou city, China, Proceedings. Paleontology Working Meeting, pp. 51.

Page, M., Licht, A., Dupont-Nivet, G., Meijer, N., Barbolini, N., Hoorn, C., Schauer, A., Huntington, K., Bajnai, D., Fiebig, J., Mulch, A. and Guo, Z., 2019. Synchronous cooling and decline in monsoonal rainfall in northeastern Tibet during the fall into the Oligocene icehouse. Geology. 47, 203-206. http://dx.doi.org/10.1130/g45480.1.

Palcu, D.V., Patina, I.S., Şandric, I., Lazarev, S., Vasiliev, I., Stoica, M. and Krijgsman, W., 2021. Late Miocene megalake regressions in Eurasia. Scientific Reports. 11, 11471. http://dx.doi.org/10.1038/s41598-021-91001-z.

Pan, B., Li, Q., Hu, X., Geng, H., Liu, Z., Jiang, S. and Yuan, W., 2013. Cretaceous and Cenozoic cooling history of the eastern Qilian Shan, north-eastern margin of the Tibetan Plateau: evidence from apatite fission-track analysis. Terra Nova. 25, 431-438. https://doi.org/10.1111/ter.12052.
Pan, B., Su, H., Hu, Z., Hu, X., Gao, H., Li, J. and Kirby, E., 2009. Evaluating the role of climate and tectonics during non-steady incision of the Yellow River: evidence from a 1.24 Ma terrace record near Lanzhou, China. Quaternary Science Reviews. 28, 3281-3290. https://doi.org/10.1016/j.quascirev.2009.09.003.

Peng, S., Ding, Y., Liu, W. and Li, Z., 2019. 1 km monthly temperature and precipitation dataset for China from 1901 to 2017. Earth System Science Data. 11, 1931-1946. https://doi.org/10.5194/essd-11-1931-2019.

Peng, T., Li, J., Song, C., Guo, B., Liu, J., Zhao, Z. and Zhang, J., 2016. An integrated biomarker perspective on Neogene-Quaternary climatic evolution in NE Tibetan Plateau: Implications for the Asian aridification. Quaternary International. 399, 174-182. https://doi.org/10.1016/j.quaint.2015.04.020.

Popov, S.V., Rozanov, A., Rögl, F., Steininger, F.F., Shcherba, I.G. and Kovac, M., 2004. Lithological-paleogeographic maps of Paratethys. CFS Courier Forschungsinstitut Senckenberg, 1-46.

Pound, M.J., Haywood, A.M., Salzmann, U. and Riding, J.B., 2012. Global vegetation dynamics and latitudinal temperature gradients during the Mid to Late Miocene (15.97-5.33Ma). Earth-Science Reviews. 112, 1-22. https://doi.org/10.1016/j.earscirev.2012.02.005.

QBGMR (Qinghai Bureau of Geology and Mineral Resources), 1991. Regional Geology of Qinghai Province. Geological Publishing House, Beijing.

Qiang, X., An, Z., Song, Y., Chang, H., Sun, Y., Liu, W., Ao, H., Dong, J., Fu, C., Wu, F., Lu, F., Cai, Y., Zhou, W., Cao, J., Xu, X. and Ai, L., 2011. New eolian red clay sequence on the western Chinese Loess Plateau linked to onset of Asian desertification about 25 Ma ago. Science China Earth Sciences. 54, 136-144. https://doi.org/10.1007/s11430-010-4126-5.

Qiu, Z.-D., 2000. Insectivore, Dipodoidean and Lagomorph from the middle Miocene Quantougou fauna of Lanzhou, Gansu. Vertebrata Palasiatica. 38, 287-302. https://doi.org/10.19615/j.cnki.1000-3118.2000.04.004.

Qiu, Z.-D., 2001a. Cricetid rodents from the middle Miocene Quantougou fauna of Lanzhou, Gansu. Vertebrata Palasiatica. 39, 204-214. https://doi.org/10.19615/j.cnki.1000-3118.2001.04.009.

Qiu, Z.-D., 2001b. Glirid and gerbillid rodents from the middle Miocene Quantougou fauna of Lanzhou, Gansu. Vertebrata Palasiatica. 39, 297-305. https://doi.org/10.19615/j.cnki.1000-3118.2001.03.006.

Qiu, Z.-D., Li, C.-K. and Wang, S.-J., 1981. Miocene mammals fossils from the Xining Basin, Qinghai Province. Vertebrata Palasiatica. 19, 156-173. https://doi.org/10.19615/j.cnki.1000-3118.1981.02.008.

Qiu, Z.-D. and Li, L., 2023. Miocene squirrels from Linxia Basin, Gansu, China; paleoenvironmental and palaeoecological implications. Palaeogeography, Palaeoclimatology, Palaeoecology. 619, 111530. https://doi.org/10.1016/j.palaeo.2023.111530.

Qiu, Z.-D., Wang, B.-Y. and Li, L., 2023. Middle Cenozoic micromammals from Linxia Basin, Gansu Province, China, and their implications for biostratigraphy and palaeoecology. Palaeogeography, Palaeoclimatology, Palaeoecology. 616, 111467. https://doi.org/10.1016/j.palaeo.2023.111467.

Qiu, Z.-X., 2006. Quaternary environmental changes and evolution of large mammals in North China. Vertebrata Palasiatica. 44, 109-132. https://doi.org/10.1360/aps040120.

Qiu, Z.-X., Deng, T. and Wang, B.-Y., 2004c. Early Pleistocene Mammalian Fauna from Longdan, Dongxiang, Gansu, China. Science Press, Beijing.

Qiu, Z.-X. and Gu, Z.-G., 1988. A new locality yielding mid-Tertiary mammals near Lanzhou, Gansu. Vertebrata Palasiatica. 26, 198-213 (in Chinese with English abstract). https://doi.org/10.19615/j.cnki.1000-3118.1988.03.007.

Qiu, Z.-X. and Qiu, Z.-D., 1990. The sequence and division of mammalian local faunas in the Neogene of China. Journal of Stratigraphy. 14, 241-260 (in Chinese). https://doi.org/10.19839/j.cnki.dcxzz.1990.04.001.

Qiu, Z.-X. and Qiu, Z.-D., 1995. Chronological sequence and subdivision of Chinese Neogene mammalian faunas. Palaeogeography, Palaeoclimatology, Palaeoecology. 116, 41-70.
https://doi.org/10.1016/0031-0182(94)00095-P.

Qiu, Z.-X., Qiu, Z.-D., Deng, T., Li, C.-K., Zhang, Z.-Q., Wang, B.-Y. and Wang, X.-M., 2013. Neogene Land Mammal Stages/Ages of China, in: X. Wang, L.J. Flynn and M. Fortelius (Eds.), Fossil Mammals of Asia: Neogene Biostratigraphy and Chronology. Columbia University Press, New York, pp. 29-90.

Qiu, Z.-X., Qiu, Z.-D., Zheng, Y. and Li, L., 2023. Stratigraphic context of Oligocene to Pliocene mammal-bearing deposits in Linxia Basin, Gansu Province, China: a historical review and a discussion of ongoing controversies. Palaeogeography, Palaeoclimatology, Palaeoecology. 628, 111773. https://doi.org/10.1016/j.palaeo.2023.111773.

Qiu, Z.-X. and Wang, B.-Y., 1999. Allacerops (Rhinoceroidea, Perissodactyla), its discovery in China and its systematic position. Vertebrata PalAsiatica. 37, 48-61. https://doi.org/10.19615/j.cnki.1000-3118.1999.01.005.

Qiu, Z.-X., Wang, B.-Y. and Deng, T., 2004a. Indricotheres (Perissodactyla, mammalia) from Oligocene in Linxia Basin, Gansu, China. Vertebrata Palasiatica. 42, 177-192. https://doi.org/10.19615/j.cnki.1000-3118.2004.03.001.

Qiu, Z.-X., Wang, B.-Y. and Deng, T., 2004b. Mammal fossils from Yagou, Linxia Basin, Gansu, and related stratigraphic problems. Vertebrata PalAsiatica. 42, 276-296. https://doi.org/10.19615/j.cnki.1000-3118.2004.04.003.

Qiu, Z.-X., Wang, B.-Y., Deng, T., Ni, X.-J. and Wang, X.-M., 2002. Notes on the mammal fauna from the bottom of loess deposits at Longdan, Dongxiang County, Gansu Province. Quaternary Science. 22, 33-38 (in Chinese with English abstract). https://doi.org/10.3321/j.issn:1001-7410.2002.01.006.

Qiu, Z.-X., Wang, B.-Y., Qiu, Z.-D., Heller, F., Yue, L.-P., Xie, G.-P., Wang, X.-M. and Engesser, B., 2001. Land mammal geochronology and magnetostratigraphy of mid-Tertiary deposits in the Lanzhou Basin, Gansu Province, China. Eclogae Geologicae Helvetiae. 94, 373-385. http://dx.doi.org/10.5169/seals-168902.

Qiu, Z.-X., Wang, B.-Y., Qiu, Z.-D., Xie, G.-P., Xie, J.-Y. and Wang, X.-M., 1997. Recent advances in study of the Xianshuihe Formation in Lanzhou Basin, in: Y. Tong, Y. Zhang, W. Wu, J. Li and L. Shi (Eds.), Evidence for Evolution, Essays in Honor of Prof. Chungchien Young on the Hundredth Anniversary of His Birth. China Ocean Press, Beijing, pp. 177-192 (in Chinese with English abstract).

Qiu, Z.-X., Wang, B.-Y. and Xie, J.-Y., 1998. Mid-Tertiary Chalicothere (Perissodactyla) fossils from Lanzhou, Gansu, China. Vertebrata PalAsiatica. 36, 297-318. https://doi.org/10.19615/j.cnki.1000-3118.1998.04.004.

Qiu, Z.-X. and Xie, J.-Y., 1997. A new species of Aprotodon (Perissodactyla, Rhinocerotidae) from Lanzhou Basin, Gansu, China. Vertebrata PalAsiatica. 35, 250-267. https://doi.org/10.19615/j.cnki.1000-3118.1997.04.002.

Qiu, Z.-X., Xie, J.-Y. and Yan, D.-F., 1990. Discovery of some early Miocene mammalian fossils from Dongxiang, Gansu. Vertebrata Palasiatica. 28, 9-24. https://doi.org/10.19615/j.cnki.1000-3118.1990.01.002.

Ren, X., Nie, J., Saylor, J.E., Wang, X., Liu, F. and Horton, B.K., 2020. Temperature Control on Silicate Weathering Intensity and Evolution of the Neogene East Asian Summer Monsoon. Geophysical Research Letters. 47, e2020GL088808. https://doi.org/10.1029/2020GL088808.

Saylor, J.E., Jordan, J.C., Sundell, K.E., Wang, X., Wang, S. and Deng, T., 2018. Topographic growth of the Jishi Shan and its impact on basin and hydrology evolution, NE Tibetan Plateau. Basin Research. 30, 544-563. https://doi.org/10.1111/bre.12264.

Sha, Y., Ren, X., Shi, Z., Zhou, P., Li, X. and Liu, X., 2020. Influence of the Tibetan Plateau and its northern margins on the mid-latitude Westerly Jet over Central Asia in summer. Palaeogeography, Palaeoclimatology, Palaeoecology. 544, 109611. https://doi.org/10.1016/j.palaeo.2020.109611.

Shi, J., Li, Q., Stidham, T.A., Zhang, C., Jiangzuo, Q., Chen, M. and Ni, X., 2023. Evolutionary and biogeographic implications of an Erycine snake (Serpentes, Erycidae, Eryx) from the Upper Miocene of the Linxia Basin, Gansu Province, China. Palaeogeography, Palaeoclimatology, Palaeoecology. 617, 111491.
https://doi.org/10.1016/j.palaeo.2023.111491.

Song, B., Hu, F., Liang, Y., Zhang, K., Ji, J., Algeo, T.J., Hower, J.C., Yang, T. and Zhang, X., 2022. Middle to Late Miocene tectonic forcing of intensified humidity in the Xunhua Basin, NE Tibetan Plateau. Palaeogeography, Palaeoclimatology, Palaeoecology. 607, 111268. https://doi.org/10.1016/j.palaeo.2022.111268.

Song, C., 2006. Tectonic uplift and Cenozoic sedimentary evolution in the northern margin of the Tibetan Plateau, Lanzhou University, Lanzhou (in Chinese with English abstract).

Strömberg, C.A.E., 2011. Evolution of Grasses and Grassland Ecosystems. Annual Review of Earth and Planetary Sciences. 39, 517-544. https://doi.org/10.1146/annurev-earth-040809-152402.

Su, T., Spicer, R.A., Wu, F.-X., Farnsworth, A., Huang, J., Del Rio, C., Deng, T., Ding, L., Deng, W.-Y.-D., Huang, Y.-J., Hughes, A., Jia, L.-B., Jin, J.-H., Li, S.-F., Liang, S.-Q., Liu, J., Liu, X.-Y., Sherlock, S., Spicer, T., Srivastava, G., Tang, H., Valdes, P., Wang, T.-X., Widdowson, M., Wu, M.-X., Xing, Y.-W., Xu, C.-L., Yang, J., Zhang, C., Zhang, S.-T., Zhang, X.-W., Zhao, F. and Zhou, Z.-K., 2020. A Middle Eocene lowland humid subtropical "Shangri-La" ecosystem in central Tibet. Proceedings of the National Academy of Sciences. 117, 32989-32995. https://doi.org/10.1073/pnas.2012647117.

Sun, D., Su, R., Li, Z. and Lu, H., 2011. The ultrafine component in Chinese loess and its variation over the past 7.6 Ma: implications for the history of pedogenesis. Sedimentology. 58, 916-935. https://doi.org/10.1111/j.1365-3091.2010.01189.x.

Sun, J., Cheng, G., Li, W., Sha, Y. and Yang, Y., 2013. On the Variation of NDVI with the Principal Climatic Elements in the Tibetan Plateau. Remote Sensing. 5, 1894-1911. https://doi.org/10.3390/rs5041894.

Sun, J., Zhang, Z., Cao, M., Windley, B.F., Tian, S., Sha, J., Abdulov, S., Gadoev, M. and Oimahmadov, I., 2020. Timing of seawater retreat from proto-Paratethys, sedimentary provenance, and tectonic rotations in the late Eocene-early Oligocene in the Tajik Basin, Central Asia. Palaeogeography, Palaeoclimatology, Palaeoecology. 545, 109657. https://doi.org/10.1016/j.palaeo.2020.109657.

Sun, L., Deng, C., Deng, T., Kong, Y., Wu, B., Liu, S., Li, Q. and Liu, G., 2023. Magnetostratigraphy of the Oligocene and Miocene of the Linxia Basin, northwestern China. Palaeogeography, Palaeoclimatology, Palaeoecology. 613, 111404. https://doi.org/10.1016/j.palaeo.2023.111404.

Sun, X. and Wang, P., 2005. How old is the Asian monsoon system?—Palaeobotanical records from China. Palaeogeography, Palaeoclimatology, Palaeoecology. 222, 181-222. https://doi.org/10.1016/j.palaeo.2005.03.005.

Sun, Y., An, Z., Clemens, S.C., Bloemendal, J. and Vandenberghe, J., 2010. Seven million years of wind and precipitation variability on the Chinese Loess Plateau. Earth and Planetary Science Letters. 297, 525-535. https://doi.org/10.1016/j.epsl.2010.07.004.

Tang, Y., Wan, S., Zhao, D., Yu, Z., Xu, Z., Zhang, J., Song, Z., Li, M., Jin, H., Jiao, W., Dong, H. and Li, A., 2023. Evolution of Asian drying since 30 Ma revealed by clay minerals record in the West Pacific and its tectonic-climatic forcing. Science China Earth Sciences. 66, 1365-1382. https://doi.org/10.1007/s11430-022-1075-0.

Tardif, D., Sarr, A.C., Fluteau, F., Licht, A., Kaya, M., Ladant, J.B., Meijer, N., Donnadieu, Y., Dupont-Nivet, G., Bolton, C.T., Le Hir, G., Pillot, Q., Poblete, F., Sepulchre, P., Toumoulin, A. and Banfield, W., 2023. The role of paleogeography in Asian monsoon evolution: a review and new insights from climate modelling. Earth-Science Reviews. 243, 104464. https://doi.org/10.1016/j.earscirev.2023.104464.

Wang, B. and Qiu, Z., 2000a. Dipodidae (Rodentia, mammalia) from the lower member of Xianshuihe Formation in Lanzhou Basin, Gansu, China. Vertebrata PalAsiatica. 38, 10-35. https://doi.org/10.19615/j.cnki.1000-3118.2000.01.002.

Wang, B. and Qiu, Z., 2000b. Micromammal fossils from red mudstone of lower member of Xianshuihe Formation
in Lanzhou Basin, China. Vertebrata Palasiatica. 38, 255-273.
https://doi.org/10.19615/j.cnki.1000-3118.2000.04.002.

Wang, F., Sun, D., Chen, F., Bloemendal, J., Guo, F., Li, Z., Zhang, Y., Li, B. and Wang, X., 2015. Formation and evolution of the Badain Jaran Desert, North China, as revealed by a drill core from the desert centre and by geological survey. Palaeogeography, Palaeoclimatology, Palaeoecology. 426, 139-158.
https://doi.org/10.1016/j.palaeo.2015.03.011.

Wang, J., Fang, X., Zhang, W., Zan, J., Miao, Y. and Li, S., 2010. Magnetostratigraphy and implications of the Heilinding Section, the Linxia Basin, Gansu province, China. Marine Geology & Quaternary Geology. 30, 129-136 (in Chinese with English abstract). https://doi.org/10.3724/SP.J.1140.2010.05129.

Wang, J., Zhou, X., Wang, S., Ye, J., Liu, J., Zheng, Y., Stidham, T.A., Zhao, K., Behling, H. and Li, X., 2024. Two-Stage Climate and Vegetation Change at the East Asian Monsoonal Margin Across the Miocene Climatic Optimum. Paleooceanography and Paleoclimatology. 39, e2024PA004894.
https://doi.org/10.1029/2024PA004894.

Wang, S., He, W. and Chen, S., 2013b. The gomphotheriid mammal Platybelodon from the Middle Miocene of Linxia Basin, Gansu, China. Acta Palaeontologica Polonica. 58, 221-240.
https://doi.org/10.4202/app.2011.0009.

Wang, S., Li, C., Li, Y. and Zhang, X., 2023. Gomphotheres from Linxia Basin, China, and their significance in biostratigraphy, biochronology, and paleozoogeography. Palaeogeography, Palaeoclimatology, Palaeoecology. 613, 111405. https://doi.org/10.1016/j.palaeo.2023.111405.

Wang, S., Li, Y., Duangkrayom, J., Yang, X., He, W. and Chen, S., 2017. A new species of gomphotherium (Proboscidea, mammalia) from China and the evolution of gomphotherium in Eurasia. Journal of Vertebrate Paleontology. 37, e1318284. https://doi.org/10.1080/02724634.2017.1318284.

Wang, S., Liu, S., Xie, G., Liu, J., Peng, T. and Hou, S., 2013a. Gomphotherium wimani from Wushan County, China, and its implications for the Miocene stratigraphy of the Tianshui area. Vertebrata Palasiatica. 51, 71-84.
https://doi.org/10.19615/j.cnki.1000-3118.2013.01.009.

Wang, W., Zhang, P., Liu, C., Zheng, D., Yu, J., Zheng, W., Wang, Y., Zhang, H. and Chen, X., 2016. Pulsed growth of the West Qinling at ~30 Ma in northeastern Tibet: Evidence from Lanzhou Basin magnetostratigraphy and provenance. Journal of Geophysical Research: Solid Earth. 121, 7754-7774.
https://doi.org/10.1002/2016jb013279.

Wang, W., Zheng, D., Li, C., Wang, Y., Zhang, Z., Pang, J., Wang, Y., Yu, J., Wang, Y., Zheng, W., Zhang, H. and Zhang, P., 2020. Cenozoic Exhumation of the Qilian Shan in the Northeastern Tibetan Plateau: Evidence From Low-Temperature Thermochronology. Tectonics. 39. https://doi.org/10.1029/2019tc005705.

Wang, X.-M., Flynn, L.J. and Deng, C.-L., 2023. A review of the Cenozoic biostratigraphy, geochronology, and vertebrate paleontology of the Linxia Basin, China, and its implications for the tectonic and environmental evolution of the northeastern margin of the Tibetan Plateau. Palaeogeography, Palaeoclimatology, Palaeoecology. 628, 111775. https://doi.org/10.1016/j.palaeo.2023.111775.

Wang, X.-M., Qiu, Z.-D., Li, Q., Wang, B.-Y., Qiu, Z.-X., Downs, W.R., Xie, G.-P., Xie, J.-Y., Deng, T., Takeuchi, G.T., Tseng, Z.J., Chang, M., Liu, J., Wang, Y., Biasatti, D., Sun, Z.-C., Fang, X.-M. and Meng, Q.-Q., 2007. Vertebrate paleontology, biostratigraphy, geochronology, and paleoenvironment of Qaidam Basin in northern Tibetan Plateau. Palaeogeography, Palaeoclimatology, Palaeoecology. 254, 363-385.
https://doi.org/10.1016/j.palaeo.2007.06.007.

Wang, X.-M., Wang, B.-Y., Qiu, Z.-X., Xie, G.-P., Xie, J.-Y., Downs, W., Qiu, Z.-D. and Deng, T., 2003. Danghe area (western Gansu, China) biostratigraphy and implications for depositional history and tectonics of northern Tibetan Plateau. Earth and Planetary Science Letters. 208, 253-269.
https://doi.org/10.1016/S0012-821X(03)00047-5.

Wang, X.-X., Li, J.-J., Song, C.-H., Zattin, M., Zhao, Z.-J., Zhang, J., Zhang, Y. and He, K., 2012. Late Cenozoic orogenic history of Western Qinling inferred from sedimentation of Tianshui basin, northeastern margin of Tibetan Plateau. International Journal of Earth Sciences. 101, 1345-1356.
https://doi.org/10.1007/s00531-011-0724-5.

Wang, X.-X., Nie, J.-S., Stevens, T., Zhang, H.-B. and Xiao, W.-J., 2022. Resolving conflicting models of late Miocene East Asian summer monsoon intensity recorded in Red Clay deposits on the Chinese Loess Plateau. Earth-Science Reviews. 234, 104200. https://doi.org/10.1016/j.earscirev.2022.104200.

Wang, X.-X., Zattin, M., Wang, L.-B., Pang, B.-Z., Yang, Y., He, K., Danišík, M., Li, X.-M., Ma, Z.-H., Tao, J., Song, A., Liu, H.-M. and Zhang, Y.-B., 2023. Cenozoic morphotectonic evolution of the northeasternmost Tibetan Plateau: Evidence from detrital thermochronology. Global and Planetary Change. 225, 104131.
https://doi.org/10.1016/j.gloplacha.2023.104131.

Wang, Z., Shen, Y., Licht, A. and Huang, C., 2018. Cyclostratigraphy and Magnetostratigraphy of the Middle Miocene Ashigong Formation, Guide Basin, China, and Its Implications for the Paleoclimatic Evolution of NE Tibet. Paleoceanography and Paleoclimatology. 33, 1066-1085. https://doi.org/10.1029/2018pa003409.

Wang, Z., Zhang, Z., Huang, C., Shen, J., Sui, Y. and Qian, Z., 2021. Astronomical forcing of lake evolution in the Lanzhou Basin during early Miocene period. Earth and Planetary Science Letters. 554, 116648.
https://doi.org/10.1016/j.epsl.2020.116648.

Wasiljeff, J., Kaakinen, A., Salminen, J.M. and Zhang, Z., 2020. Magnetostratigraphic constraints on the fossiliferous Ulantatal sequence in Inner Mongolia, China: Implications for Asian aridification and faunal turnover before the Eocene-Oligocene boundary. Earth and Planetary Science Letters. 535, 116125.
https://doi.org/10.1016/j.epsl.2020.116125.

Wei, G., Li, X.-H., Liu, Y., Shao, L. and Liang, X., 2006. Geochemical record of chemical weathering and monsoon climate change since the early Miocene in the South China Sea. Paleooceanography. 21, PA4214.
https://doi.org/10.1029/2006PA001300.

Westerhold, T., Marwan, N., Drury, A.J., Liebrand, D., Agnini, C., Anagnostou, E., Barnet, J.S.K., Bohaty, S.M., De Vleeschouwer, D., Florindo, F., Frederichs, T., Hodell, D.A., Holbourn, A.E., Kroon, D., Lauretano, V., Littler, K., Lourens, L.J., Lyle, M., Pálike, H., Röhl, U., Tian, J., Wilkens, R.H., Wilson, P.A. and Zachos, J.C., 2020. An astronomically dated record of Earth's climate and its predictability over the last 66 million years. Science. 369, 1383-1387. https://doi.org/10.1126/science.aba6853.

Wu, F., Fang, X., Meng, Q., Zhao, Y., Tang, F., Zhang, T., Zhang, W. and Zan, J., 2017. Magneto- and litho-stratigraphic records of the Oligocene-Early Miocene climatic changes from deep drilling in the Linxia Basin, Northeast Tibetan Plateau. Global and Planetary Change. 158, 36-46.
https://doi.org/10.1016/j.gloplacha.2017.09.008.

Wu, F., Fang, X., Yang, Y., Dupont-Nivet, G., Nie, J., Fluteau, F., Zhang, T. and Han, W., 2022. Reorganization of Asian climate in relation to Tibetan Plateau uplift. Nature Reviews Earth & Environment. 3, 684-700.
https://doi.org/10.1038/s43017-022-00331-7.

Wu, L., Yue, L., Wang, J., Heller, F. and Deng, T., 2006. Magnetostratigraphy of stratotype section of the Neogene Xiejian Stage. Journal of Stratigraphy. 30, 50-53 (in Chinese with English abstract).
https://doi.org/10.3969/j.issn.0253-4959.2006.01.007.

Xiao, G., Guo, Z., Dupont-Nivet, G., Lu, H., Wu, N., Ge, J., Hao, Q., Peng, S., Li, F., Abels, H.A. and Zhang, K., 2012. Evidence for northeastern Tibetan Plateau uplift between 25 and 20Ma in the sedimentary archive of the Xining Basin, Northwestern China. Earth and Planetary Science Letters. 317-318, 185-195.
https://doi.org/10.1016/j.epsl.2011.11.008.
Xie, G., 2004. The Tertiary and local mammalian faunas in Lanzhou Basin, Gansu. Journal of Stratigraphy. 28, 67-80 (in Chinese with English abstract). https://doi.org/10.3969/j.issn.0253-4959.2004.01.011.

Xu, Z., 2016. Oligocene-Miocene pollen records in Xunhua Basin, northeastern Tibetan Plateau and its implications for evolution of the East Asian monsoon, China University of Geosciences, Wuhan, 16-54 pp (in Chinese with English abstract).

Xu, Z., Zhang, J., Ji, J. and Zhang, K., 2015. The Mid-Miocene Pollen Record of the Xunhua Basin, NE Tibetan Plateau: Implications for Global Climate Change. Acta Geologica Sinica - English Edition. 89, 1649-1663. https://doi.org/10.1111/1755-6724.12571.

Yang, F., Guo, Z., Zhang, C., Abu Sadat Md, S., He, Z. and Deng, C., 2019. High-Resolution Eocene Magnetostratigraphy of the Xijigou Section: Implications for the Infilling Process of Xining Basin, Northeastern Tibetan Plateau. Journal of Geophysical Research: Solid Earth. 124, 7588-7603. https://doi.org/10.1029/2019JB017624.

Yang, R., Fang, X., Meng, Q., Zan, J., Zhang, W., Deng, T., Yang, Y., Ruan, X., Yang, L. and Li, B., 2017. Paleomagnetic Constraints on the Middle Miocene-Early Pliocene Stratigraphy in the Xining Basin, NE Tibetan Plateau, and the Geologic Implications. Geochemistry, Geophysics, Geosystems. 18, 3741-3757. https://doi.org/10.1002/2017gc006945.

Yang, X., Li, Y. and Wang, S., 2017. Cranial and dental material of Gomphotherium wimani (Gomphotheriidae, Proboscidea) from the Middle Miocene of the Linxia Basin, northwestern China. Vertebrata Palasiatica. 55, 331-346. https://doi.org/10.19615/j.cnki.1000-3118.170511.

Yang, Y., Fang, X., Han, W., Wang, Y. and Galy, A., 2022. Terrestrial carbonate oxygen isotopes constraints on the interplay between westerlies and monsoonal rains modulating the Cenozoic climate on the northeastern Tibetan Plateau. Palaeogeography, Palaeoclimatology, Palaeoecology. 608, 111289. https://doi.org/10.1016/j.palaeo.2022.111289.

Yang, Y., Galy, A., Fang, X., Yang, R., Zhang, W. and Zan, J., 2017. Eolian dust forcing of river chemistry on the northeastern Tibetan Plateau since 8 Ma. Earth and Planetary Science Letters. 464, 200-210. https://doi.org/10.1016/j.epsl.2017.02.009.

Yao, Y., 2019. Detrital zircon U-Pb geochronology of the Xining Basin and its geological implications in Cenozoic, Lanzhu University, Lanzhou, 1-53 pp (in Chinese with English abstract).

You, Y., Huber, M., Müller, R.D., Poulsen, C.J. and Ribbe, J., 2009. Simulation of the Middle Miocene Climate Optimum. Geophysical Research Letters. 36, L04702. https://doi.org/10.1029/2008GL036571.

Yue, L., Heller, F., Qiu, Z., Zhang, L., Xie, G., Qiu, Z. and Zhang, Y., 2000. Magnetostratigraphy and pavleo-environmental record of Tertiary deposits of Lanzhou Basin. Chinese Science Bulletin. 46, 770-773. https://doi.org/10.1007/BF03187220.

Yue, L., Qiu, Z., Xie, G., Qiu, Z., Zhang, L., Zhang, Y. and Heller, F., 2003. Sedimentary Environment of Tertiary Recorded in the Yongdeng Section of Lanzhou Basin. Acta Sedimentologica Sinica. 21, 683-687 (in Chinese with English abstract). https://doi.org/10.3969/j.issn.1000-0550.2003.04.022.

Zan, J., Fang, X., Yan, M., Zhang, W. and Lu, Y., 2015. Lithologic and rock magnetic evidence for the Mid-Miocene Climatic Optimum recorded in the sedimentary archive of the Xining Basin, NE Tibetan Plateau. Palaeogeography, Palaeoclimatology, Palaeoecology. 431, 6-14. https://doi.org/10.1016/j.palaeo.2015.04.024.

Zan, J., Fang, X., Zhang, W., Yan, M. and Zhang, D., 2018a. A new record of late Pliocene-early Pleistocene aeolian loess-red clay deposits from the western Chinese Loess Plateau and its palaeoenvironmental implications. Quaternary Science Reviews. 186, 17-26. https://doi.org/10.1016/j.quascirev.2018.02.010.

Zan, J., Fang, X., Zhang, W., Yan, M. and Zhang, T., 2016. Palaeoenvironmental and chronological constraints on
the Early Pleistocene mammal fauna from loess deposits in the Linxia Basin, NE Tibetan Plateau. Quaternary
Science Reviews. 148, 234-242. https://doi.org/10.1016/j.quascirev.2016.07.026.

Zan, J., Kang, J., Yan, M., Fang, X., Li, X., Guan, C., Zhang, W. and Fang, Y., 2018b. A Pedogenic Model for the Magnetic Enhancement of Late Miocene Fluvial-Lacustrine Sediments From the Xining Basin, NE Tibetan Plateau. Journal of Geophysical Research: Solid Earth. 123, 6176-6194. https://doi.org/10.1029/2018jb016064.

Zewdie, W., Csaplovics, E. and Inostroza, L., 2017. Monitoring ecosystem dynamics in northwestern Ethiopia using NDVI and climate variables to assess long term trends in dryland vegetation variability. Applied Geography. 79, 167-178. https://doi.org/10.1016/j.apgeog.2016.12.019.

Zhai, Y. and Cai, T., 1984. The Tertiary system of Gansu province. Gansu Geology. 1984, 1-40 (in Chinese with English abstract).

Zhang, J., Hu, Y., Zhu, C., Flögel, S., Fang, X. and Sun, J., 2023. Modeling the effects of global cooling and the Tethyan Seaway closure on North African and South Asian climates during the Middle Miocene Climate Transition. Palaeogeography, Palaeoclimatology, Palaeoecology. 619, 111541. https://doi.org/10.1016/j.palaeo.2023.111541.

Zhang, J., Li, J., Guo, B., Ma, Z., Li, X., Ye, X., Yu, H., Liu, J., Yang, C., Zhang, S., Song, C., Hui, Z. and Peng, T., 2016. Magnetostratigraphic age and monsoonal evolution recorded by the thickest Quaternary loess deposit of the Lanzhou region, western Chinese Loess Plateau. Quaternary Science Reviews. 139, 17-29. https://doi.org/10.1016/j.quascirev.2016.02.025.

Zhang, J., Li, J., Song, C., Zhao, Z., Xie, G., Wang, X., Hui, Z. and Peng, T., 2013. Paleomagnetic ages of Miocene fluvio-lacustrine sediments in the Tianshui Basin, western China. Journal of Asian Earth Sciences. 62, 341-348. https://doi.org/10.1016/j.jseaes.2012.10.014.

Zhang, J., Wang, Y., Zhang, B. and Zhang, Y., 2016. Tectonics of the Xining Basin in NW China and its implications for the evolution of the NE Qinghai-Tibetan Plateau. Basin Research. 28, 159-182. https://doi.org/10.1111/bre.12104.

Zhang, P., Ao, H., Dekkers, M.J., An, Z., Wang, L., Li, Y., Liu, S., Qiang, X., Chang, H. and Zhao, H., 2018. Magnetochronology of the Oligocene mammalian faunas in the Lanzhou Basin, Northwest China. Journal of Asian Earth Sciences. 159, 24-33. https://doi.org/10.1016/j.jseaes.2018.03.021.

Zhang, P., Ao, H., Dekkers, M.J., Li, Y. and An, Z., 2016. Late Oligocene–Early Miocene magnetochronology of the mammalian faunas in the Lanzhou Basin–environmental changes in the NE margin of the Tibetan Plateau. Scientific Reports. 6, 38023. https://doi.org/10.1038/srep38023.

Zhang, P., Ao, H., Roberts, A.P., Li, Y., Sun, Q., Zhang, J., Sun, P. and Qiang, X., 2020. Magnetochronology of Mid-Miocene mammalian fauna in the Lanzhou Basin, northeastern Tibetan Plateau: Implications for Asian mammal migration. Geoscience Frontiers. 11, 1337-1344. https://doi.org/10.1016/j.gsf.2020.01.006.

Zhang, R., Jiang, D., Zhang, Z., Cheng, Z. and Zhang, Q., 2017. Comparison of the climate effects of surface uplifts from the northern Tibetan Plateau, the Tianshan, and the Mongolian Plateau on the East Asian climate. Journal of Geophysical Research: Atmospheres. 122, 7949-7970. https://doi.org/10.1002/2017JD026470.

Zhang, R., Wei, X., Kravchinsky, V.A., Yue, L., Zheng, Y., Qin, J., Yang, L., Ma, M., Xian, F., Gong, H., Zhang, Y. and Liu, X., 2021. “Tiny Wiggles” in the Late Miocene Red Clay Deposits in the North-East of the Tibetan Plateau. Geophysical Research Letters. 48, e2021GL093962. https://doi.org/10.1029/2021GL093962.

Zhang, T., Han, W., Fang, Y., Zhang, W., Han, S., Tian, Q., Feng, Z., Song, C. and Fang, X., 2022. Late Miocene reorganization of lake hydrological systems on the northern Tibetan Plateau linked to topographic growth. Catena. 219, 106626. https://doi.org/10.1016/j.catena.2022.106626.

Zhang, W.-F., Chen, J., Ji, J.-F. and Li, G.-J., 2016. Evolving flux of Asian dust in the North Pacific Ocean since
the late Oligocene. Aeolian Research. 23, 11-20. https://doi.org/10.1016/j.aeolia.2016.09.004.

Zhang, W.-L., Erwin, A., Wang, J.-Y., Fang, X.-M., Zan, J.-B., Yang, Y.-B., Miao, Y.-F. and Yan, X.-L., 2019. New paleomagnetic constraints for Platybelodon and Hipparion faunas in the Linxia Basin and their ecological environmental implications. Global and Planetary Change. 176, 71-83. https://doi.org/10.1016/j.gloplacha.2019.03.002.

Zhang, W.-L., Fang, X.-M., Song, C.-H., Yan, M.-D., Wang, J.-Y., Zhang, Z.-G., Wu, F.-L., Zan, J.-B., Zhang, T., Yang, Y.-B. and Tan, M.-Q., 2020. Magnetostratigraphic constraints on the age of the Hipparion fauna in the Linxia Basin of China, and its implications for stepwise aridification. Palaeogeography, Palaeoclimatology, Palaeoecology. 537, 109413. https://doi.org/10.1016/j.palaeo.2019.109413.

Zhang, W.-L., Zhang, T., Song, C.-H., Appel, E., Mao, Z.-Q., Fang, Y.-H., Lu, Y., Meng, Q.-Q., Yang, R.-S. and Zhang, D.-W., 2017. Termination of fluvial-alluvial sedimentation in the Xining Basin, NE Tibetan Plateau, and its subsequent geomorphic evolution. Geomorphology. 297, 86-99. https://doi.org/10.1016/j geomorph.2017.09.008.

Zhang, X., 1993. New discovery of the mammalian fossils in Baode period of later Miocene epoch in Lanzhou Basin. Acta Geologica Gansu. 2, 1-5 (in Chinese with English abstract).

Zhang, Y.-B., Sun, D.-H., Li, Z.-J., Wang, F., Wang, X., Li, B.-F., Guo, F. and Wu, S., 2014. Cenozoic record of aeolian sediment accumulation and aridification from Lanzhou, China, driven by Tibetan Plateau uplift and global climate. Global and Planetary Change. 120, 1-15. https://doi.org/10.1016/j.gloplacha.2014.05.009.

Zhang, Y.-P., Zheng, W.-J., Wang, W.-T., Tian, Y.-T., Zhou, R.-J., Xu, B.-B., Li, M.-J., Yan, Y.-G., Tian, Q.-Y. and Zhang, P.-Z., 2020. Rapid Eocene Exhumation of the West Qinling Belt: Implications for the Growth of the Northeastern Tibetan Plateau. Lithosphere. 2020, 8294751. https://doi.org/10.2113/2020/8294751.

Zhang, Z., Wang, H., Guo, Z. and Jiang, D., 2007. What triggers the transition of palaeoenvironmental patterns in China, the Tibetan Plateau uplift or the Paratethys Sea retreat? Palaeogeography, Palaeoclimatology, Palaeoecology. 245, 317-331. https://doi.org/10.1016/j.palaeo.2006.08.003.

Zhao, H., Qiang, X., Xu, X. and Sun, Y., 2020. Iron oxide characteristics of the Chinese loess-red clay sequences and their implications for the evolution of the East Asian summer monsoon since the Late Oligocene. Palaeogeography, Palaeoclimatology, Palaeoecology. 543, 109604. https://doi.org/10.1016/j.palaeo.2020.109604.

Zhao, H., Sun, Y. and Qiang, X., 2017. Iron oxide characteristics of mid-Miocene Red Clay deposits on the western Chinese Loess Plateau and their paleoclimatic implications. Palaeogeography, Palaeoclimatology, Palaeoecology. 468, 162-172. https://doi.org/10.1016/j.palaeo.2016.12.008.

Zhao, Y., Wu, F., Fang, X., Meng, Q. and Cai, D., 2022. Global climate change drove terrestrial ecosystem evolution during the late Paleocene-middle Miocene in the Lanzhou Basin, northeast Tibetan Plateau. Palaeogeography, Palaeoclimatology, Palaeoecology. 598, 111045. https://doi.org/10.1016/j.palaeo.2022.111045.

Zheng, D., Zhang, P.-Z., Wan, J., Yuan, D., Li, C., Yin, G., Zhang, G., Wang, Z., Min, W. and Chen, J., 2006. Rapid exhumation at ~8 Ma on the Liupan Shan thrust fault from apatite fission-track thermochronology: Implications for growth of the northeastern Tibetan Plateau margin. Earth and Planetary Science Letters. 248, 198-208. https://doi.org/10.1016/j.epsl.2006.05.023.

Zheng, Y., Qiu, Z., Qiu, Z., Li, L., Wei, X., Zhang, R., Yue, L. and Deng, T., 2023. Revised magnetostratigraphy of the Linxia Basin in the northeast Tibetan Plateau, constrained by micromammalian fossils. Palaeogeography, Palaeoclimatology, Palaeoecology. 623, 111620. https://doi.org/10.1016/j.palaeo.2023.111620.

Zhou, X., Hui, Z., Vachula, R.S., Wei, X., Chen, P., Zhang, J., Wang, X. and Peng, T., 2023a. Mid-Miocene
Palaeofire and Its Complex Relationship With Vegetation Changes in the Wushan Basin, Northeastern Tibetan Plateau, China: Evidence From a High-Resolution Charcoal Record. Paleooceanography and Paleoclimatology. 38, e2022PA004461. https://doi.org/10.1029/2022PA004461.

Zhou, Z., Liu, J., Chen, L., Spicer, R.A., Li, S., Huang, J., Zhang, S., Huang, Y., Jia, L., Hu, J. and Su, T., 2023. Cenozoic plants from Tibet: An extraordinary decade of discovery, understanding and implications. Science China Earth Sciences. 66, 205-226. https://doi.org/10.1007/s11430-023-9980-9.

Zhuang, G., Hourigan, J.K., Koch, P.L., Ritts, B.D. and Kent-Corson, M.L., 2011. Isotopic constraints on intensified aridity in Central Asia around 12Ma. Earth and Planetary Science Letters. 312, 152-163. https://doi.org/10.1016/j.epsl.2011.10.005.

<figure><img src="image_4.png" /><figcaption>**Figure 1:** Topographic map of the northeastern Tibetan Plateau (NETP) showing the locations of orogenic belts and major Cenozoic basins, especially the Longzhong Basin. The inset map shows the schematic atmospheric circulation pattern of Asia with the locations of the NETP in Asia. EA: East Asian.</figcaption></figure>
<figure><img src="image_5.png" /><figcaption>**Figure 2:** Geological map of the study area showing the sub-basins of the Longzhong Basin and regional lithology. The numbers in black circles represent the various sites referenced in Fig. 5.</figcaption></figure>