Linxia Basin Research Articles

Eolian dust forcing of river chemistry on the northeastern Tibetan Plateau since 8 Ma

Eolian dust is one of the most important factors controlling fluvial hydrological evolution in modern arid and semi-arid central Asia. Here, we present the bulk carbonate Ca–Mg–Sr concentrations and Sr isotopic compositions recorded in water soluble salts, carbonate and silicate fractions, as well as the Nd isotopic compositions in the silicate fraction of a Late Miocene (12.2–5.1 Ma) fluvial sequence exhibiting paleosol development, in the Linxia Basin on the northeastern Tibetan Plateau (TP). Bulk carbonate Mg–Sr systematics show a distinct pattern in log–log plots of Mg/Ca versus log Sr/Ca ratios, and clearly higher 87Sr/86Sr ratios since ∼8 Ma. These findings cannot be adequately explained by the mechanism of prior calcite precipitation (PCP) – this latter process results in a positive correlation between the Mg/Ca and Sr/Ca ratios in authigenic calcite, evident in the fixed gradient in their log–log plots and has been isolated as being the major factor controlling carbonate Mg–Sr systematics before 8 Ma. Nor can these findings be explained by other mechanisms related to the catchment's provenance/sedimentation. The dramatic changes in carbonate Sr contents, Sr isotopes, and Sr/Mg ratios since ∼8 Ma may therefore be inferred to have been triggered by significant inputs of eolian dust via the dissolution of dust carbonates and evaporites in the paleowaters where fluvial and paleosol carbonates precipitated. This process of eolian dust input can be reliably illustrated using a binary mixing model corresponding to a series of varying PCP fluxes (identical to processes affecting the area before 8 Ma) combined with a constant eolian influx calculated from the co-variations between Mg/Ca, Sr/Ca and Sr isotopic ratios. Eolian dust also leaves a fingerprint in the carbonate and silicate minerals of bulk sediments, as revealed respectively by their Sr and Nd isotopic compositions. Eolian dust compositions for the ∼8–5 Ma on the northeastern TP can thus be taken to be characterized by a εNd value ≤−10.5 for the silicate fraction, and by a 87Sr/86Sr value ≥0.7115 for the labile faction (carbonates and evaporites). Eolian dust is now recognized to have made a significant impact on the hydrological evolution of arid and semi-arid northern China as far back as ∼8 Ma, suggesting an enhanced regime of dust activity and regional aridification in central Asia at that time.

A new Old World vulture from the late Miocene of China sheds light on Neogene shifts in the past diversity and distribution of the Gypaetinae

ABSTRACT Neogene fossils of Old World vultures (Aegypiinae and Gypaetinae) are known from both Old World and New World records. There are no extant Old World vultures in the Americas today, although a large diversity of Gypaetinae is known from Miocene to late Pleistocene records. Despite a comparatively large number of North American gypaetine fossils, complete specimens have rarely been reported from Eurasia and Africa. We describe the exceptional skeleton of a new gypaetine vulture from the late Miocene deposits of the Linxia Basin in northwestern China. The specimen is the oldest record of Gypaetinae from Eurasia or Africa. A reexamination of the geographic and temporal distribution of most Old World vultures from Neogene deposits indicates a diverse radiation, coincident with early- to mid-Miocene grassland expansion for Gypaetinae. Although the diversification of Aegypiinae has been linked to the transition from C3 to C4 grassland, Gypaetinae diversification predates that transition in both North Am...

Tectonosedimentary evolution model of an intracontinental flexural (foreland) basin for paleoclimatic research

Intracontinental flexural (foreland) basin sediments are now frequently used as archives for detailed paleoclimatic and sedimentary environmental reconstruction, fossil and stratigraphic correlation, and tectonic evolution and uplift of basin and orogen. However, sedimentologic characteristics vary considerably in time-space with the evolution of flexural basin, apt to cause misinterpretation of climatic change and stratigraphic correlation. Based on high resolution fossil mammal and magnetostratigraphic constraints and sedimentary facies analysis, here we took the Linxia Basin at the front of the NE Tibetan Plateau as a case to demonstrate and figure out a model how sedimentology and stratigraphy vary temporospatially with the evolution of such flexural basin. The results show that the Linxia Basin is a type intracontinental foreland basin subjected to two phases of flexural deformation exerted by the West Qin Ling (Mts.) and NE Tibetan Plateau to the south. Phase I began latest at the beginning of the Miocene (23.3Ma), indicated by a balanced fast flexural subsidence and mostly fine sediment infilling giving rise to the early underlying unconformity. It manifests as an obvious sediment wedge with high filling rate, thickening toward mountains and an occurrence of a mountains-parallel big river – shallow lake system along the foredeep, suggesting a less high mountain topography. In the late Phase I, from ~13Ma to 8Ma, the subsidence and thickening rates began to decrease, accompanied by faults and deformation propagating gradually into the basin, causing gradual basinward migration of the foredeep and its accompanying river-lake system. Since ~8Ma in Phase II, the West Qin Ling and NE Tibetan began to uplift rapidly and thrust/load onto the Linxia Basin, causing strong mountain erosion, thrust-fold belt propagation and basin overfilling. This forced the mountains-parallel river - lake system to turn to the mountains-perpendicular alluvial - braided river system, and finally to an outflow system by the Quaternary onset of the Yellow River in the basin. Concurrent are rapid rotation of the basin, occurrence of growth strata and late unconformities, widespread expansion of boulder conglomerates, great decreasing and increasing sedimentation rates above and before the hanging wall of the fault-fold system and new supplementary provenance from the thrust-fold system. This demonstrates that in stable climate, same lithologic units such as distinct lacustrine sediments and alluvial conglomerates will migrate basinwards with the foredeep moving into basin, causing a great diachroneity and often misleads to recognize the same lithologic unit in space as one unit in time. A dynamic model is presented that should help to avoid such pitfalls in tectonic basin evolution, especially concerning stratigraphic correlation and paleoclimatic change research.

Plateau uplift forcing climate change around 8.6 Ma on the northeastern Tibetan Plateau: Evidence from an integrated sedimentary Sr record

The uplift of the northern Tibetan Plateau (TP) has long been regarded as one of major factors accounting for both the enhanced process of aridification recorded in central Asia and the shifts in the Asian monsoonal circulations that are known to have occurred at approximately 8Ma. Until now, there have been few sedimentary records reported on which can directly, and in an integrated fashion, shed light on the region's tectonic and climate regimes. This can be largely attributed to the fact that the influence exerted by the presence of source materials and subsequent sedimentary sorting in this tectonically active region would be likely to bias significantly any paleoclimatic interpretation of silicate-derived proxies. Based on detailed investigations of strontium (Sr) distributions revealed by multi-step leaching in a fluvial sequence from the Linxia Basin which includes paleosols, we reconstructed the long-term late Miocene regional climatic and environmental changes likely to have occurred on the northeastern TP from 12.1 to 5.2Ma. We investigated Sr-related proxies in two typical paleosol profiles to constrain Sr mobility in paleosol weathering, and, thus, to further prompt the interpretation of Sr-related proxies along the whole section. We would suggest that carbonate-derived Sr concentrations and Sr/Ca ratios are suitable proxies for tracing regional climate change associated with weathering and pedogenesis; together, they exhibit weakened chemical weathering intensity and pedogenesis at ~8.6Ma. The concomitant appearance of immature sediments through poor sedimentary sorting revealed by silicate-derived Rb/Sr, 87Sr/86Sr and Eu anomaly (Eu/Eu*) alongside a sharp increase in sedimentation rates noted at this time suggests that it was indeed tectonic uplift that principally controlled the dramatic climatic and environmental changes. This multi-proxy record of concomitant tectonic uplift and climate change in the Linxia Basin provides direct geological evidence for uplift driven climate change in the northeastern TP region.

Palaeoenvironmental and chronological constraints on the Early Pleistocene mammal fauna from loess deposits in the Linxia Basin, NE Tibetan Plateau

Abstract The Longdan mammal fauna from the central part of Linxia Basin, NE Tibetan Plateau, is the first Early Pleistocene fauna in China in which the fossils are derived loess deposits, and it provides an excellent opportunity to document mammalian and environmental evolution in Asia. However, the precise age and palaeoenvironmental setting of the fauna are controversial due to the poor exposure of the outcrop section. In the present study, a 105-m-long drill core was obtained from Longdan village and used for detailed magnetostratigraphic dating. The results demonstrate that the late Pliocene- Pleistocene loess deposits in the Longdan section deposited since ca. 3 Ma and that the Longdan fauna has an age range of 2.5–2.2 Ma. In addition, the results of lithological and rock magnetic analyses demonstrate that paleosols are weakly developed throughout the whole core and that in the lower and middle parts the core the magnetic susceptibility and its frequency dependence are relatively low and uniform. These observations, combined with the ecological characteristics of the Longdan fauna, indicate that during the Early Pleistocene the climate in the Longdan area, and even in the Linxia Basin, was sub-humid and that the aeolian dust was frequently subjected to post-depositional reworking by water.

An examination of the dietary habits of Platybelodon grangeri from the Linxia Basin of China: Evidence from dental microwear of molar teeth and tusks

The paleodiet of shovel-tusked gomphotheres from the upper middle Miocene Hujialiang Formation of the Linxia Basin (Gansu Province, China) was assessed via molar microwear analysis of dental enamel. Both adults and an ontogenetic series of individuals of Platybelodon grangeri with assigned dental ages estimated via comparison of eruption and wear to that of extant elephants were analyzed. Mandibular tusks were also examined for microscopic scars to test a long-standing hypothesis that P. grangeri used its mandibular tusks to shovel substrate. Results show a consistent browsing signal throughout all of the age classes studied. Evenso, scratch numbers are higher and scratch widths are greater in older individuals indicating that coarser browse was consumed in older versus younger individuals. Results are more similar to those of the extant forest elephant (Loxodonta cyclotis) than to other extant forms (Loxodonta africana and Elephas maximus). Mandibular tusk microwear is very fine and inconsistent with the usage of lower tusks to shovel aquatic or terrestrial substrates and more consistent with stripping vegetation than as shoveling agents.

A new species of the tetralophodont amebelodontineKonobelodonLambert, 1990 (Proboscidea, Mammalia) from the Late Miocene of China

ABSTRACT Here we describe a new species of Konobelodon Lambert, 1990 — a poorly known tetralophodont shovel-tusked proboscidean — from the Late Miocene of the Linxia Basin, China. Detailed osteological anatomies of skulls, teeth, and partial postcranial bones of the new taxon, Konobelodon robustus n. sp., are described and detailed morphological comparisons with the other species of Konobelodon (K. atticus (Wagner, 1857) = Mastodon grandincisivus, Schlesinger 1917, and K. britti (Lambert, 1990)) and other gomphotheres are conducted. The skull and jaw-closing muscles of a juvenile individual of the new species are reconstructed and the body mass is estimated based on its limb bones. Phylogenetic analysis of genera within Elephantimorpha results in three most parsimonious trees, of which two support a sister-group relationship between Konobelodon and Platybelodon, within a monophyletic Amebelodontinae. The new results enhance our knowledge on the anatomy and phylogeny of Konobelodon, and indicate pronounced...

A combined-mesowear analysis of late Miocene giraffids from North Chinese and Greek localities of the Pikermian Biome

The family Giraffidae is represented by two extant taxa (Giraffa camelopardalis and Okapia johnstoni), both of which are committed browsers. During the late Miocene, however, the Pikermian Biome included more than 15 giraffid species with a wider range of dietary ecologies. To examine the diet of these taxa, we apply a novel combined approach using four variables from two methods of dental mesowear. We score the traditional outer mesowear, which evaluates the sharpness and relief of the labial-most paracone enamel band. We also apply inner mesowear, which evaluates the surface morphology of the lingual band of paracone enamel on the mesial and distal ends, as well as the junction point between the two. Using a database of 8 extant species (N=98) of browsing, grazing, and mixed feeding ruminants, we predict the diets 190 extinct giraffid specimens. The discriminant function analysis (DFA) of the extant taxa using all four mesowear variables predicted diet with greater accuracy than any single mesowear variable. We compare the dietary profiles of species found in four Pikermian Biome regions: Samos, Pikermi, North China, and Linxia Basin. We find differences in the giraffid diet throughout the Pikermian Biome: in the localities from Greece, a larger number of giraffids were predicted as browsers, whereas both Chinese regions included a larger number of mixed feeding individuals. Our inner and outer mesowear dietary predictions agree with previously studied ecomorphological paleodietary proxies. Our data supports the hypothesis that the late Miocene giraffids comprised a wider range of dietary habits than the living giraffe and okapi.

A new species of Euprox (Cervidae, Artiodactyla) from the upper Miocene of the Linxia Basin, Gansu Province, China, with interpretation of its paleoenvironment.

The Linxia Basin, Gansu Province, China, is known for its abundant and well preserved fossils. Here a new species, Euprox grandis sp. nov., is established based on a skull and antlers collected from the upper Miocene Liushu Formation of the Linxia Basin. The new species is distinguishable from other Euprox species by its large body size, notably long pedicle and weak burr. The main beam and the brow tine are slightly curved both medially and backwards, and the apex of the main beam turns, curving slightly laterally. The upper cheek teeth are brachydont, with a clear central fold on the premolars and internal postprotocrista and metaconule fold on M1-M2. The cingulum is almost absent, only occasionally weakly developed at the anterior and lingual surface of the teeth. Cladistic analysis was carried out using the TNT software, and two most parsimonious trees were retained. As the strict consensus tree shows E. grandis appears to be an advanced muntiacine form, which may have a close relationship with the genus Muntiacus. The presence of E. grandis in the Linxia Basin adds new evidence to support a warm and humid environment during the late Miocene in the basin.

Evolution of Protanancus (Proboscidea, Mammalia) in East Asia

ABSTRACT—Interspecific competition and species replacement explain many evolutionary successions, but these processes are difficult to test. According to recent paleontological research, amebelodontines were predominant proboscideans in faunas of the early to middle Miocene of East Asia. In addition to the abundant Platybelodon, other amebelodontines are known, but they have been largely neglected by researchers. Here we describe two species of Protanancus, Pr. tobieni and Pr. brevirostris, sp. nov., from China. The former was present during the middle Miocene in Tongxin and Qin’an and was previously attributed to Amebelodon or Serbelodon; the latter was present during the early Miocene in the Linxia Basin. Cladistic analysis indicates that the two species appear to represent primitive members of Protanancus. However, the phylogenetic relationship among Protanancus, Platybelodon, and Amebelodon remains unresolved because of their strong parallel evolution. Our study suggests intensive competition between Protanancus and Platybelodon based on similarities in their mandibular morphologies and dental microwear patterns, with the former genus disappearing from East Asia by the late middle Miocene. This scenario is supported by a mechanical model, in which lower tusks with dentinal tubules, as occur in Platybelodon, show greater resistance to the adverse effects of both a heavy load and abrasion than those with concentric laminae, present in Protanancus. The model aids in interpreting the evolution of the inner structure of the lower tusks of amebelodontines, which may have provided a competitive advantages for these species.http://zoobank.org/urn:lsid:zoobank.org:pub:4D33BD71-CB05-4058-B9DD-337060B0B7CBSUPPLEMENTAL DATA——Supplemental materials are available for this article for free at www.tandfonline.com/UJVP

A new species of Eostyloceros (Cervidae, Artiodactyla) from the Late Miocene of the Linxia Basin in Gansu, China.

A new species, Eostyloceros hezhengensis sp. nov., is established based on a skull with its cranial appendages collected from the Late Miocene Liushu Formation of the Linxia Basin in Gansu Province, northwestern China. It is a large-sized muntjak with a distinct longitudinal ridge along the lateral margin of the frontal bone that joins the antler pedicle. The pedicle is short, cylindrical, robust, and extends posteriorly from the rear of the orbit. The anterior and posterior branches arise from the burr and diverge at an angle of 30°. The posterior branch is relatively long, and its tip is strongly curved posteriorly. The anterior branch is straight and situated anteromedially from the posterior branch. The posterior branch is lateromedially compressed, and the anterior branch has a circular cross section. The morphological observation together with a cladistic and a principal component analysis indicate that E. hezhengensis is more basal than any known species of the genus Eostyloceros in having shorter pedicles, a lower position of the fork above the burr, more slender anterior branches, and a small angle between the anterior and posterior branches. Its age is the middle Late Miocene, corresponding to the late Bahean.

A new species of Chleuastochoerus (Artiodactyla: Suidae) from the Linxia Basin, Gansu Province, China.

The Linxia Basin, Gansu Province, China, is known for its abundant and well-preserved fossils. Here a new species, Chleuastochoerus linxiaensis sp. nov., is described based on specimens collected from the upper Miocene deposits of the Linxia Basin, distinguishable from C. stehlini by the relatively long facial region, more anteromedial-posterolaterally compressed upper canine and more complicated cheek teeth. A cladistics analysis placed Chleuastochoerus in the subfamily Hyotheriinae, being one of the basal taxa of this subfamily. Chleuastochoerus linxiaensis and C. stehlini are considered to have diverged before MN 10. C. tuvensis from Russia represents a separate lineage of Chleuastochoerus, which may have a closer relationship to C. stehlini but bears more progressive P4/p4 and M3.

Relations between Paleoclimatological Conditions and Mineralogical Characteristics of Clays in Miocene Sediments at Linxia Basin, China

Linxia basin is a late Cenozoic fault-block basin along the border between the Tibet plateau and the Loess plateau in Northwestern China. Its formation and sediments’ record may be directly affected by the structural dynamics and the uplift of the Tibet Plateau. For this reason, we studied the mineral characteristics of the Maogou formation of Miocene sediments using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD results showed that quartz, chlorite, illite, calcite, plagioclase, orthoclase, kaolinite, and trace palygorskite are present throughout the sequence of the cross-section in Linxia basin. In contrast, gypsum and ankerite occur occasionally in the upper portion of the Miocene deposits. The content of calcite varied with layers in the profile and was relatively concentrated in mudstone. Chlorite and illite were observed transforming into palygorskite under SEM observation. Based on the mineral characteristics and the change of mineral composition, especially the clay minerals, it could be inferred that an arid environment prevailed in the region with warm and cold intervals during Miocene time.

A falconid from the Late Miocene of northwestern China yields further evidence of transition in Late Neogene steppe communities

ABSTRACT Although the family Falconidae, which includes extant falcons and caracaras, has a long evolutionary history, most previously reported fossils referred to this family are isolated single elements. We report a new species, Falco hezhengensis sp. nov., represented by a nearly complete and articulated skeleton from the Late Miocene deposits of Linxia Basin in northwestern China. The new fossil shares an array of derived morphologies with the genus Falco, and analysis of the largest morphological dataset for Falconidae, sampling most genera, identifies the specimen as a new stem kestrel. The phylogeny shows a high degree of congruence with published molecular phylogenies and time trees supporting a Miocene radiation of Falconidae. The species provides a new calibration for the divergence of extant kestrels from other Falco. Remains of a small mammal, a jerboa (Dipodidae), are preserved in the abdominal region of the specimen. Integrated with data from other avian remains from the Linxia Basin, the ne...

A new species of Shaanxispira (Bovidae, Artiodactyla) from the upper Miocene of China.

A new species of the bovid Shaanxispira, from the upper Miocene deposits of the Linxia Basin, Gansu Province, China, is described here. Shaanxispira is endemic to Northern China and was previously known only from the Lantian area, Shaanxi Province, by two species, S. chowi and S. baheensis. The new species, S. linxiaensis nov. sp., is of early Bahean in age, slightly older than the species from the Lantian area. The horn-cores of the new species are more derived, with large wing-shaped antero-medial keels, suggesting the occurrence of a different lineage of Shaanxispira in the Linxia Basin. Although Shaanxispira has homonymously twisted horn-cores, it is not closely related to other late Miocene bovids with homonymously twisted horn-cores, like Oioceros and Samotragus. Its phylogenetic status is still in debate, but might be more closely related to the late Miocene "ovibovines."

Late Cenozoic fluvial–lacustrine susceptibility increases in the Linxia Basin and their implications for Tibetan Plateau uplift

The variations and mechanisms of fluvial–lacustrine mass-specific magnetic susceptibility (χ) in the northeastern (NE) Tibetan Plateau are complex. In this study, we compiled two Miocene–Pliocene χ records (the Heilinding and Maogou sections, respectively) from the Linxia Basin fluvial–lacustrine sediments, NE Tibetan Plateau to describe the χ increases and discuss their influential factors. The χ in the Heilinding section remained relatively stable at low values before ca. 8.5 Ma, and has increased since ca. 8.5 Ma with strong fluctuations. In the Maogou section the χ increased at ca. 6.0 Ma with relatively weak fluctuations. The mean χ values were higher in the Heilinding section than the Maogou section. The rock magnetic results showed that hematite dominated both sites during the early periods (>8.5 Ma in the Heilinding and >6.0 Ma in the Maogou, respectively), and was replaced by magnetite after that time. Based on the comparison of χ records in Linxia Basin with other magnetic and climate records from the surrounding regions, the χ increase around 8.5–6.0 Ma in the Linxia Basin was mainly driven by tectonics in the northeastern Tibetan Plateau.

New species of Tsaidamotherium (Bovidae, Artiodactyla) from China sheds new light on the skull morphology and systematics of the genus

A new species of Tsaidamotherium (Bovidae, Artiodactyla), T. brevirostrum, described here represents only the second discovery of the genus. Tsaidamotherium is a mid-sized late Miocene bovid with an odd-looking plate-like horn-core apparatus so far known only from northwestern China. The holotype of T. brevirostrum is a cranial part of skull from the Liushu Formation (late Miocene) of the Linxia Basin. The new species differs from the type species, T. bohlini, mainly in horn-core morphology, having the frontal horn-cores proper much smaller and less distinctly separated from the plate-shaped posterior portion. Furthermore, the new species has smaller frontal sinuses, but a thicker layer of compact bone beneath the horn-core apparatus as seen in frontal section. A complete skull with a smaller horn-core apparatus is considered to represent a female individual of T. brevirostrum. The facial part of the skull, which is first known for this genus, is very short and high, with a high nasal cavity, strongly retracted nasals, and shortened premaxillae and premolar rows. All this probably suggests that the animal with an enlarged nasal cavity, like the modern Saiga and Budorcas, may have had a special adaptation to the high plateau environment.

A bizarre tandem-horned elasmothere rhino from the Late Miocene of northwestern China and origin of the true elasmothere

Although the modern Indian and Javan rhinos have a single horn on their noses, the extinct one-horned rhino Elasmotherium was a source for the legendary unicorn, because the latter had a very long horn on its forehead and lived with the prehistoric human beings who drew its images on cave paintings. Elasmothere rhinos first appeared in South Asia in the Early Miocene, but the origin of Elasmotherium has been unclear. All other elasmotheres have a weak or strong nasal horn, whereas Elasmotherium seems to lose the nasal horn of its ancestors and to get a huge frontal horn apparently abruptly. Here we report the first discovered skull of Sinotherium lagrelii from the Late Miocene red clays in the Linxia Basin, northwestern China. This skull has an enormous nasofrontal horn boss shifted posteriorly and a smaller frontal horn boss, which are connected to each other, indicating an intermediate stage for the single frontal horn of Elasmotherium. Morphological and phylogenetic analyses confirm that Sinotherium is a transitional taxon between Elasmotherium and other elasmotheres, positioned near the root of the giant unicorn clade and originated in a subarid steppe. The posteriorly shifted nasal horn has a more substantial support and the arched structure of the nasofrontal area is an adaptation for a huge horn.

A juvenile skull of Ancylotherium (Mammalia, Perissodactyla, Chalicotheriidae) from the Pliocene of China

Though rarely found, chalicotheres have long been considered as indicators of wooded environment because of their unique anatomical structure and inferred ecological habits. A juvenile skull of a chalicothere with its articulated mandible was unearthed from the Duikang locality, Guanghe County, Gansu Province, China. This specimen can be identified as Ancylotherium sp. based on its short symphysis, shallow mandible, high crown and large size of upper molars, obvious crochets on upper milk teeth, complex structure of DP2 and dp2, and developed metastylids on the lower milk teeth. This rare skull differs from all other known species of the genus Ancylotherium. Nonetheless, existence of Ancylotherium in China is confirmed without doubt; at least five species in China (from Gansu, Sichuan, Shanxi and Shaanxi provinces respectively) can be attributed to this genus. Ancylotherium and its contemporaneous faunal components at the Duikang locality, together indicate a subarid steppe environment with small patches of forest in the Linxia Basin during the Early Pliocene.

Timing of Xunhua and Guide basin development and growth of the northeastern Tibetan Plateau, China

AbstractThe Xunhua, Guide and Tongren intermontane basin system in the NE Tibetan Plateau, situated near the Xining basin to the N and the Linxia basin to the E, is bounded by thrust fault‐controlled ranges. These include to the N, the Riyue Shan, Laji Shan and Jishi Shan ranges, and to the S the northern West Qinling Shan (NWQ). An integrated study of the structural geology, sedimentology and provenance of the Cenozoic Xunhua and Guide basins provides a detailed record of the growth of the NE Tibetan Plateau since the early Eocene. The Xining Group (ca. 52–21 Ma) is interpreted as consisting of unified foreland basin deposits which were controlled by the bounding thrust belt of the NWQ. The Xunhua, Guide and Xining subbasins were interconnected prior to later uplift and damming by the Laji Shan and Jishi Shan ranges. Their sediment source, the NWQ, is constrained by strong unidirectional paleocurrent trends towards the N, a northward fining lithology, distinct and recognizable clast types and detrital zircon ages. Collectively, formation of this mountain–basin system indicates that the Tibetan Plateau expanded into the NWQ at a time roughly coinciding with Eocene to earliest Miocene continental collision between India and Eurasia. The Guide Group (ca. 21–1.8 Ma) is inferred to have been deposited in the separate Xunhua, Guide and Tongren broken foreland basins. Each basin was filled by locally sourced alluvial fans, braided streams and deltaic‐lacustrine systems. Structural, paleogeographic, paleocurrent and provenance data indicate that thrust faulting in the NWQ stepped northward to the Laji Shan from ca. 21 to 16 Ma. This northward shift was accompanied by E–W shortening related to nearly N–S‐striking thrust faulting in Jishi Shan after 11–13 Ma. A lower Pleistocene conglomerate (1.8–1.7 Ma) was deposited by a through‐flowing river system in the overfilled and connected Guide and Xunhua basins following the termination of thrust activity. All of the basin–mountain zones developed along the Tibetan Plateau's NE margin since Indian–Tibetan continental collision may have been driven by collision‐induced basal drag of old slab remnants in the manner of N‐dipping and flat‐slab subduction, and their subsequent sinking into the deep mantle.