•Mesozoic–Cenozoic tectonics of North China.•Intracontinental rifting in North China.•Magnitude of Neogene extension in the Shanxi Rift.•Inverse and forward modeling of low-temperature ...thermochronometric data.
We present new apatite U-Th-Sm/He (AHe; n = 51), apatite fission track data (AFT; n = 12), and zircon U-Th/He (ZHe; n = 8) data for two elevation transects in the north-central Shanxi Rift, North China. Low-temperature thermochronologic data combined with forward and inverse time-temperature history models reveal a Precambrian to Quaternary thermal history characterized by: (1) cooling to <∼50°C during the Proterozoic, consistent with the development of a regional unconformity above Neoarchean–Paleoproterozoic cratonic basement rocks; (2) reheating to <∼180°C due to sediment burial during the Paleozoic to Mesozoic; (3) cooling at a rate >3.5°C/Ma during the Late Jurassic to earliest Cretaceous Yanshanian orogeny; (4) a possible ca. 120-90 Ma reheating event due to elevated geothermal gradients and/or local sediment burial; (5) Late Cretaceous (ca. 110-65 Ma) cooling contemporaneous with regional extension in eastern Asia and denudation of the paleo-Taihangshan highlands; and finally, (6) post ca. 10 Ma cooling associated with extension in the Shanxi Rift. AFT dates from the deepest exhumed structural positions of the sampled footwall blocks are mostly >65 Ma and AHe dates tend to be highly dispersed within samples. AFT inverse and AHe forward model results indicate that samples were at temperatures of <∼75°C by ca. 70 Ma. Despite the early Cenozoic and older AFT and AHe dates, metamict zircon grains with high effective uranium (eU >∼750 ppm) yield young ZHe dates of ca. 13-9 Ma, consistent with Late Miocene exhumation. We argue for the onset of latest cooling by ca. 10 Ma based on these ZHe dates; however, the precise timing for the onset of rifting remains uncertain. The results further suggest that Late Miocene–Quaternary extension in the north-central Shanxi Rift is responsible for ≤∼2.5 km of exhumation, such that published Quaternary extension and fault throw rates are significantly (>100%) higher than long-term rates inferred from the thermochronologic data.
Paleoelevation reconstruction using oxygen isotopes is making a significant contribution to understanding the Cenozoic uplift of the Himalayas and the Tibetan Plateau. This paper presents new oxygen ...and carbon isotopic compositions from well dated Tertiary paleosols, lacustrine calcareous carbonates, and marls from the Nianbo (60–54 Ma) and upper Pana Formations (51–48 Ma) of the Linzizong Group in the Linzhou (Penbo) Basin. The sediments of the Nianbo Formation, which are >180 m-thick, were deposited in alluvial fans, braided rivers, fan deltas, and on nearshore to offshore lacustrine settings, whereas those of the upper Pana Formation are >100 m-thick and are comprised predominantly of proximal alluvial fan and braided river deposits. Correlations between the lithofacies and stable isotopic compositions suggest that the basin was mainly a hydrologically open environment. It is confirmed that the δ18Oc and δ13Cc values from Nianbo and Pana Formations have not yet been reset by late-stage diagenesis based on petrographic examination, oxygen isotope of the fossil ostracodes, and tectonic deformation of strata. The paleoelevations are reconstructed using the corrected most negative paleosurface water δ18Opsw values. These imply that the Linzhou area had attained an elevation of 4500±400 m during the period of the Indo-Asian collision, i.e., achieved a near-present elevation, and may form an Andean-type mountain range stretching the Gangdese arc before collision. The Gangdese Mountains probably maintained high elevations since at least the Paleocene and could play a crucial role in the climate change in the interior of the Tibetan Plateau during the Early Cenozoic. The paleogeomorphic scenario of the Eocene Tibet is proposed to exist at two high mountains in excess of 4500 m that sandwiched a low elevation basin.
•δ18O data of Ostracode analyzed in situ by NanoSIMS rule out diagenetic reset.•The southern Lhasa terrane reached an elevation of 4500 m in Paleocene–Eocene.•Eocene Tibet was two high mountains sandwiched one low corridor.
The initial collision between Indian and Asian continents marked the starting point for transformation of land-sea thermal contrast,uplift of the Tibet-Himalaya orogen,and climate change in Asia.In ...this paper,we review the published literatures from the past 30 years in order to draw consensus on the processes of initial collision and suturing that took place between the Indian and Asian plates.Following a comparison of the different methods that have been used to constrain the initial timing of collision,we propose that the tectono-sedimentary response in the peripheral foreland basin provides the most sensitive index of this event,and that paleomagnetism presents independent evidence as an alternative,reliable,and quantitative research method.In contrast to previous studies that have suggested collision between India and Asia started in Pakistan between ca.55 Ma and50 Ma and progressively closed eastwards,more recent researches have indicated that this major event first occurred in the center of the Yarlung Tsangpo suture zone（YTSZ） between ca.65 Ma and 63 Ma and then spreading both eastwards and westwards.While continental collision is a complicated process,including the processes of deformation,sedimentation,metamorphism,and magmatism,different researchers have tended to define the nature of this event based on their own understanding,an intuitive bias that has meant that its initial timing has remained controversial for decades.Here,we recommend the use of reconstructions of each geological event within the orogenic evolution sequence as this will allow interpretation of collision timing on the basis of multidisciplinary methods.
•Carbonate clumped isotopes validate the preservation of primary carbonate of the Gonjo Basin in the early and middle Eocene.•The Gonjo Basin was low (0.7 km) in the early Eocene and rose to 3.8 km ...in the middle Eocene.•Rapid uplift was induced by intracontinental subduction between the Lhasa and Qiangtang terrains.
Views differ on the uplift history of the SE Tibetan Plateau and causal geodynamic mechanisms, yet reliable age-constrained paleoaltimetry in this region could test growth models of the entire plateau. Here we apply carbonate clumped isotope thermometry to well-dated carbonate paleosols and marls in the Gonjo Basin, SE Tibet, to reveal the topographic evolution of the basin. The sedimentary ages of carbonates of the lower and upper Ranmugou Formation are constrained to 54-50 Ma and 44-40 Ma, respectively. The temperature derived from carbonate clumped isotope thermometry indicates the mean annual air temperature (MAAT) of the Gonjo Basin in the early Eocene was ∼24°C, which is consistent with the warm climate indicated by palm fossils. The MAAT of the basin in the middle Eocene was ∼7°C, 17°C cooler than in the early Eocene. Carbonate clumped oxygen isotope thermometry-based paleoaltimetry shows the Gonjo Basin experienced a rapid uplift of 3.1 km, from ∼0.7 km in the early Eocene to ∼3.8 km in the middle Eocene. This rise explains the marked cooling. As a cause of this rapid rise, and the associated regional climate change transforming the landscape from desert to forest, we invoke crustal deformation and thickening induced by intracontinental subduction between the Lhasa and Qiangtang terranes that comprise the core of the Tibet.
This study presents a comprehensive low‐temperature thermochronometric data set from the Shanxi Rift, Taihangshan, and eastern Ordos block in North China, including new apatite fission track and ...apatite (U‐Th‐Sm)/He data and published apatite and zircon fission track and (U‐Th‐Sm)/He data. We use these data and new thermal history inversion models to reveal that the Shanxi Rift and Taihangshan experienced an increase in cooling rates between ca. 110–70 Ma and ca. 50–30 Ma. A preceding ca. 160–135 Ma cooling event is generally restricted to the western rift margin in the Lüliangshan and Hengshan. In contrast, the ca. 50–30 Ma cooling event was widespread and occurred coevally with the opening of the Bohai Basin and slip across the NNE‐striking Eastern Taihangshan fault. In the southern rift zone, however, exhumation beginning ca. 50 Ma was likely associated with fault block uplift across the ESE–striking Qinling and Huashan faults, which accompanied the extensional opening of the Weihe Graben. Coeval fault slip along the NNE–striking Eastern Taihangshan faults and ESE–striking Qinling and Huashan faults was associated with NW‐SE extension in North China related to oblique subduction of the Pacific plate under Eastern Asia and slow convergence rates. The Shanxi Rift is commonly attributed to Late Miocene and younger extension, but our new thermochronologic data do not precisely record the onset of rifting. However, our inversion models do suggest ≤∼50°C of Neogene–Quaternary cooling, consistent with ≤∼2 km of footwall uplift across most range‐bounding faults.
Key Points
Fault blocks of the Shanxi Rift have experienced <∼2 km of footwall uplift since the Miocene
Low‐temperature thermochronometric data record region‐wide cooling events at ca. 110–70 Ma and 50–30 M, prior to development of the modern Shanxi Rift
Exhumation at ca. 50–30 Ma is coeval with the formation of the Bohai and Weihe basins during a period of regional NW‐SE extension
Sandstone petrographic and U–Pb detrital zircon analyses of Upper Triassic sedimentary rocks from the northern margin of India (Tethyan Himalaya Sequence) and southern margin of Eurasia (Lhasa ...terrane) provide new constraints on the Mesozoic paleogeography of Neo–Tethyan Ocean basins. The Upper Triassic Nieru Formation of the Tethyan Himalaya Sequence (THS) near Lazi city (∼29°N, 87.5°E) is dominated by Indian-affinity, Precambrian detrital zircons, which are typical of the majority of the THS. However, the Upper Triassic Langjiexue Formation of the THS exposed to the east (at 90–93°E longitude) includes significant populations of Permian to Early Jurassic (291–184 Ma) detrital zircons for which there is no known Indian source. In addition, the Upper Triassic Nieru Formation near Kangma town (∼28.5°N, 90°E), located ∼200 km to the southeast of Lazi city, yielded detrital zircon age spectra that are similar to those of Langjiexue Formation. Based on detrital zircon age spectra comparisons, we propose that both the Langjiexue and Nieru formations were derived from continental crustal fragments that were adjacent to the northwestern margin of Australia. Furthermore, we suggest that these THS units, and age-equivalent strata in Northwest Australia, West Sulawesi, Timor and West Papua, comprised a Late Triassic submarine fan along the northern Australian shelf. The Upper Triassic Mailonggang Formation in the southern Lhasa terrane (35 km northeast of Lhasa city, ∼30°N, 91.5°E) is dominated by Permian detrital zircons, which were likely derived from proximal Lhasa terrane sources. The Mailonggang Formation differs from all age-equivalent strata in the Tethyan Himalaya; therefore we interpret that it was separated from Greater India by the Neo–Tethyan Ocean.
•Upper Triassic strata record early Mesozoic paleogeography of Neo–Tethyan margins.•Langjiexue Fm. was deposited on India's margin and was sourced from West Papua.•Nieru Fm. near Lazi is typical of the Indian craton derived Tethyan Himalaya Sequence.•Nieru Fm. near Kangma are similar to the Upper Triassic strata in NW Australia.•Mailonggang Fm. was separated from Greater India by the Neo–Tethyan Ocean.
Original stable isotope compositions of carbonates representing conditions in the latest Oligocene-early Miocene Kailas and Qiabulin areas, both in southern Tibet, record Oligocene-Miocene ...paleoelevations of the Gangdese arc and the Himalayan orogen, and provide constraints on the formation of the Himalayan-Tibetan Plateau. Oxygen isotope compositions of bivalve shell, paleosol, and lacustrine carbonates indicate the preservation of unaltered isotopic signals of paleometeoric waters in the Kailas and Qiabulin areas, whereas the oxygen isotopic compositions of Liuqu Eocene paleosols were likely altered by paleometeoric waters. Paleoelevation estimates using oxygen isotopes indicate the Kailas area was at ~4.9km during ~20–19Ma and the Qiabulin Basin was at ~2.0km during 24–21Ma, but rose rapidly to ~4.1km between 21 and 19Ma. These results suggest a steep south-facing flank on the proto-Tibetan highland prior to the onset of the India-Asia collision. The Himalayan orogen began to be built against the pre-existed high (~4.5km) Gangdese Mountains in the early Eocene and obtained elevations close to those of the present by the early Miocene. We propose that the southernmost Tibetan Plateau and Himalayan orogen are the expression of an early Eocene to early Miocene southward migration of the locus of deformation. Early stage uplift is linked to the crustal thickening in the early Eocene, but the dramatic elevation gain in the early Miocene may have been caused by Indian slab rollback, break-off and coeval renewed underthrusting, behind which late Miocene to present east-west crustal extension took place.
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•Primary isotopes of meteoric waters record Oligocene-Miocene Himalayan evolution.•Himalaya/S. Tibet grew southwards from the early Eocene >4km high Gangdese Mts.•Geodynamic models explaining the elevation changes are presented and discussed.
We present two robust and well‐dated paleomagnetic poles from upper Eocene and Oligocene volcanics in the Urumieh‐Dokhtar magmatic arc, Central Iran. These two poles place Iran ∼3.7°–3° of latitude ...south of its present position between ca. 40 and 23 Ma. Our new paleomagnetic declination data indicate that the Central Iran block may have experienced a ∼11.6° clockwise rotation since the Late Eocene. We integrated our new data with the retrodeformed margins of the Zagros collision zone and contemporaneous Arabia positions to better constrain the age and configuration of the Arabia and Eurasia assembly process. In our model, the Arabia‐Eurasia collision occurred first in the western Main Zagros suture between ca. 35 and 30 Ma and then diachronously spread eastwards. Our paleogeographic reconstruction and initial continental collision timing supports the Arabia‐Eurasia collision as a first‐order driver of global cooling, Red Sea rifting, and Mediterranean extension.
Plain Language Summary
The demise of the Neo‐Tethyan ocean and accompanied continent‐continent collisions created the thick crust and the low relief surfaces of the Iran Plateau and Tibetan Plateau. The onset timing and configuration in the Zagros collisional belt are critical for understanding the uplift of the Iran Plateau, tectonic evolution of the Mediterranean and Zagros regions, as well as the associated Cenozoic climate change. However, the age and configuration of the Arabia‐Eurasia continental collision are hotly debated. Previous works generated competing collision timing estimates ranging from Late Cretaceous to Pliocene, with most estimates from Eocene to Miocene. By conducting geochronology and paleomagnetism on the Eocene‐Oligocene volcanic rocks in Central Iran, we show that the Arabia‐Eurasia collision occurred first in the western Main Zagros suture at the Eocene/Oligocene boundary, and then diachronously spread eastwards. We suggest the Arabia‐Eurasia collision facilitates the slowing of Africa, the opening of the Red Sea, the extension in the Mediterranean, and the Eocene/Oligocene global cooling.
Key Points
Our paleomagnetic results indicate a ∼3.7°–3° of latitude south of the present position of Central Iran during ca. 40–23 Ma
Central Iran has experienced ∼11.6° clockwise rotation since ca. 40 Ma
Arabia‐Eurasia collision began at the Eocene/Oligocene boundary in the western Main Zagros suture and diachronously spread eastwards
The northernmost exposures of sub-Himalayan Cenozoic strata in the Hazara–Kashmir syntaxial region of north Pakistan comprises the Paleocene–Eocene marine strata in the lower part and ...Oligocene–Miocene nonmarine strata in the upper part. This study provides the detrital zircon U–Pb geochronology of the Cenozoic strata in this area. The strong resemblance of U–Pb age spectra of Paleocene Hangu, Lockhart and Patala formations with those of Himalayan strata indicate an Indian plate provenance. The first appearance of <100 Ma detrital zircon U–Pb ages within the lower most part of the Early Eocene Margalla Hill Limestone indicates a shift from an Indian to Asian provenance. Geologic mapping shows the existence of a disconformity between the lower and upper most part of the Patala Formation, which is interpreted to have been formed by the migration of a flexural forebulge through this region. We consider the upper most part of the Patala Formation to have been deposited within the distal foredeep of the foreland basin. The Indian to Asian provenance shift and the presence of a possible foreland basin forebulge provide strong evidence that India–Asia collision was underway in northern Pakistan at ca. 56–55 Ma.
•A complete detrital zircon U–Pb age record of Paleocene–Miocene sequence in Pakistan.•Our data constrain minimum age for India–Asia collision in NW Himalaya at ca. 56–55 Ma.•Detritus of Murree formation suggest the enhanced Himalayan exhumation during 35–23 Ma.
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