Paleomagnetic data have long been used to hypothesize that the Cenozoic extrusion of the Indochina Block along the left-lateral Ailao Shan-Red River fault, as a result of the India-Asia collision, ...may have been associated with a major southward paleolatitude shift of as much as 10–15°, and a vertical-axis rotation of as much as 25–40°. However, although numerous paleomagnetic studies have been conducted in the southeast margin of the Tibetan Plateau and in the Indochina region during the last few decades, the detailed rotation as well as the latitudinal displacement of the Indochina Block remain controversial because of apparently contradicting paleomagnetic results. Geological constraints also yield contrasting estimates on the amount of displacement along different segment of the Ailao Shan-Red River fault: 700±200km in the northwest, but only ~250km in the southeast. In this paper, the available paleomagnetic data from the southeast margin of the Tibetan Plateau and Indochina, as well as the South China Block, from Jurassic and younger rocks are compiled and critically reviewed using the new paleomagnetic toolkit on Paleomagnetism.org. Our results show that (1) the South China Block has declinations that reveal no significant rotations relative to Eurasia since latest Jurassic. Inclinations are consistently shallower than expected, which is likely the result of inclination shallowing in sedimentary rocks; (2) there is no paleomagnetically resolvable southward motion of the Indochina Block with respect to Eurasia based on the paleomagnetic data. Paleomagnetic inclinations are in fact lower than expected, probably due to inclination shallowing in sediments; (3) paleomagnetic declinations reveal large, more or less coherently rotating blocks in the northern Indochina domain and the SE Tibetan margin that rotated up to 70° clockwise, much more than the ~10–15° rotation of the stable, SE part of the Indochina Block. These blocks are bounded by fold-thrust belts and strike-slip faults, which we interpret to have accommodated these block rotations during the Cenozoic. We designed a new tool on the online open-access portal Paleomagnetism.org that allows testing whether Euler rotations in a kinematic reconstruction fulfill paleomagnetic data. Using this tool, we built a first-order kinematic reconstruction of rotational deformation of northwest Indochina in Cenozoic. We show that the northwestern part of Indochina extruded 350km more along the Ailao Shan-Red River fault than the southeastern part accommodated by internal northwest Indochina rotation and deformation. Estimates of 250km of extrusion of the southeastern part of the Indochina then predicts ~600km of left-lateral motion along the northwestern part of the Ailao Shan-Red River fault, which reconciles the small and large estimates that prevail in the literature of extrusion of Indochina from the Tibetan realm during the Cenozoic India-Asia collision.
•A critical review and compilation on the available paleomagnetic data from the South China and Indochina Blocks;•A updated kinematic reconstruction of Cenozoic deformation of Indochina;•The first reconciles regarding the small and large estimates of Indochina extrusion along the Ailao Shan-Red River fault.
Thick successions of middle and late Cenozoic sedimentary rocks occur in the Linxia Basin of China. These deposits comprise an archive recording spatiotemporal patterns of mountain uplift, erosion, ...basin deformation, and associated changes in the monsoon, as a result of the growth of the northeastern Tibetan Plateau. The Linxia Basin is also world famous for its abundant and diverse vertebrate fossils that shed light on Cenozoic terrestrial ecosystem evolution; however, previous studies of these important fossils have been beset by issues related to commercial excavation and associated difficulties in ascertaining provenance, with many specimens in private collections. Despite years of intensive studies by geologists from Lanzhou University and vertebrate paleontologists from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP), aspects of basin stratigraphy and chronology still remain controversial. The heart of these controversies often revolves around questions of imprecise fossil provenance and related casual references of fossils as age tie-points, different interpretations of lithostratigraphic units at different localities across the basin, and ultimately different age determinations. In this special issue, entitled Biostratigraphy, Chronostratigraphy and Vertebrate Paleontology of the Linxia Basin, we report the findings of an IVPP project, funded by the Chinese Academy of Sciences, which addresses these controversies, proposes a new age model for basin, and develops understanding of the fossil assemblages. In this introduction to the special issue, we review the tectonic context for basin evolution and chronology as well as lithostratigraphy, paleoenvironments and climates. While issues of provenance remain challenging and will continue to burden Chinese vertebrate paleontologists into the future, our findings shed new light on the vertebrate paleontology of the Linxia Basin, and unique circumstances in which it developed.
•Linxia Basin in Gansu Province produces rich Cenozoic vertebrate fossils.•Basin sediments reflect tectonic evolution of northeastern Tibetan Plateau.•Basin structure and surrounding mountains influenced paleoclimate.•Fossils and sediments are useful for paleoenvironmental interpretations.•We highlight controversies over chronologic interpretations of strata and fossils.
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•The development of hydrido-coinage-metal clusters concerning synthesis and characterization are reviewed.•The hydrides/hydrogen adopting different modes affords a wide variety of ...structures.•The clearly systematic strategy of characterizing hydrido-coinage-metal clusters is listed and overviewed.•Important aspects of future works are proposed.
Ligated hydrido-coinage-metal clusters MxHyLz (M = Cu/Ag/Au, L = ligand; where x, y, and z are positive integers) often exhibit interesting catalytic properties, and serve as ideal models to investigate the fundamental concepts and particle growth processes, as well as the catalytic process and reaction mechanism at the atomic level. This field is emerging rapidly. For a better understanding of structure-property correlations, the isolation and characterization of these atomically precise hydrido-coinage-metal nanoclusters (NCs) are essential. This Review will summarize the recent advancements in this particular research area, including: (1) synthesis and characterization of copper hydride clusters; (2) silver hydrido clusters from small nuclearity to bulk polyhydrido clusters; and (3) gold clusters associated with hydrogen/hydride and the alloy coinage metal hydride clusters. The Review is concluded by briefly outlining some potential aspects in this flourishing and vibrant field. We hope that this Account will provide a perspective on the various strategies in the design and synthesis of hydrido-coinage-metal clusters as well as a basic understanding of their determined structures, thereby helping in building materials base for nanoscience and nanotechnology.
Variations of the Earth’s geomagnetic field during the Holocene are important for understanding centennial to millennial-scale processes of the Earth’s deep interior and have enormous potential ...implications for chronological correlations (e.g., comparisons between different sedimentary recording sequences, archaeomagnetic dating). Here, we present 21 robust archaeointensity data points from eastern China spanning the past ∼6 kyr. These results add significantly to the published data both regionally and globally. Taking together, we establish an archaeointensity reference curve for Eastern Asia, which can be used for archaeomagnetic dating in this region. Virtual axial dipole moments (VADMs) of the data range from a Holocene-wide low of ∼27 to “spike” values of ∼166 ZAm² (Z: 1021). The results, in conjunction with our recently published data, confirm the existence of a decrease in paleointensity (DIP) in China around ∼2200 BCE. These low intensities are the lowest ever found for the Holocene and have not been reported outside of China. We also report a spike intensity of 165.8 ± 6.0 ZAm² at ∼1300 BCE (±300 y), which is either a prelude to or the same event (within age uncertainties) as spikes first reported in the Levant.
•New high-resolution magnetostratigraphic study constrains the Gonjo Basin from 69 to 41.5 Ma.•Rapid SR and rotation periods suggest pulses of Tibetan crustal shortening at 69-67 Ma and 52-48 ...Ma.•Tibetan crustal shortening pulses correlate with India-Asia convergence rate.
Models that aim to explain the causes of the significant Indian plate motion acceleration around 70 Ma, and the subsequent deceleration around 52 Ma predict different scenarios regarding crustal shortening of the Tibetan Plateau, which can be tested by precisely determining the timing of regional shortening events in Tibet. Here we attempt to determine this timing by presenting a high-resolution magnetostratigraphy of a ∼3.5 km thick sedimentary sequence in the syn-contractional Gonjo Basin, east-central Tibet. We successfully isolated the primary remanence as confirmed by positive fold and reversal tests. Correlation to the geomagnetic polarity time scale reveals a 69–41.5 Ma age for the Gonjo Basin sedimentary succession. Average sedimentation rates indicate two episodes of enhanced sediment accumulation rate at 69–64 Ma and 52–48 Ma, which coincide with periods of vertical axis rotation recorded in the basin fill. This coincidence suggests a tectonic cause, which given regional structures we interpret as shortening pulses. Our results are similar to those from basins elsewhere in southern, central and northern Tibet, suggesting plateau-wide, synchronous shortening pulses at ∼69–64 Ma and ∼52–48 Ma. These pulses are synchronous with major acceleration and deceleration of India-Asia convergence rate, suggesting that both the acceleration and deceleration of India-Asia convergence may be associated with enhanced crustal deformation in Tibet, which we use to evaluate previous dynamic models explaining the Indian plate motion changes and India-Asia collision processes.
Past ground surface temperature (GST), one of the important aspects of paleoclimate reconstructions, can be inverted from borehole temperature measurements. Here, we report continuous 6,100‐m ...temperature logs in the International Continental Scientific Drilling Program SK‐2e. We inverted the past GST changes from upper borehole temperature logging (<600 m). Below this depth, localized fluid flow masks the paleoclimate record. Inversions yield an approximately 2 K GST rise since 0.1–0.6 Kyr BP and an approximately 10 K rise since 20 Kyr BP. Assuming a ±5 K influence from the deep groundwater flow, the inverted temperature rise has varied between 8 and 12 K since 20 Kyr BP, which is consistent with previous reports since the Last Glacial Maximum. Our results emphasize the potential of borehole heat‐flow profiles as a record of climate changes and the importance of climate correction for heat‐flow determinations.
Plain Language Summary
Temperatures within the shallow boreholes are perturbed by changes in ground surface temperature (GST) in response to paleoclimate variations and anthropogenic land use. The GST varies at different time scales, and these variations penetrate different depths underground. Thus, the borehole temperatures can be used for reconstructing the history of ground surface temperatures. Based on borehole geotherms of the International Continental Scientific Drilling Program in Northeast Asia, the past GST changes since the Last Glacial Maximum were inverted. The results show a ∼2 K surface temperature rise during 0.1–0.6 Kyr BP and a ∼10 K rise since 20 Kyr BP, which is consistent with previous independent estimates.
Key Points
We report an undisturbed 6,100‐m continuous heat‐flow profile from the scientific drilling project SK‐2e
The heat‐flow profile recorded a 2 K rise of ground surface temperature in the last five centuries and a 10 K rise since the Last Glacial Maximum
A basin‐scale comparison reveals localized heat‐flow anomalies induced by advective heat in deep and confined high‐permeability aquifers
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