Xiubin Lin

The Uplift History of the Haiyuan-Liupan Shan Region Northeast of the Present Tibetan Plateau: Integrated Constraint from Stratigraphy and Thermochronology

The Haiyuan-Liupan Shan delimits the northeastern margin of the Tibetan Plateau. We present the integrated results of new stratigraphic investigations, apatite fission track analyses, and related thermal history modeling tied to the structural fabric of this region. These constraints provide insight into the timing of northward propagation of the plateau with (1) local relief creation and enhanced erosion in the latest Jurassic to earliest Cretaceous, representing the local element of a complex, regional, far-field deformation response to the Lhasa-Qiangtang collision with the south Asian margin; (2) evidence for likely Late Cretaceous exhumation, but this is uncertain given the regional sedimentary gap that exists across this interval; (3) Eocene relief generation as a first likely response to far-field effects of the India-Asia collision and related to wider regional events recognized in this part of northwestern China; and (4) the latest deformation episode propagating strongly into the Haiyuan-Liupan Shan in the early Miocene, increasing in intensity in the later Miocene and possibly again in the Quaternary. The diachronous nature of the apparent responses to distant plate-boundary events demonstrates that structural preconditioning on its own is inadequate to account for this far-field deformation, suggesting that subcrustal tectonic architecture may play a role in the transfer of stress north of the Tibetan Plateau.

Conceptual models for fracturing in fault related folds

Fault related folds and fractures, which always improve reservoirs and trap capacity, especially in the oil and gas fields in western China, are of extreme importance for oil and gas exploration. Based on four assumptions and fault related fold theory, we propose four conceptual models for fracturing in fault related folds, i.e., a simple-step parallel fault bend anticline, a simple-step parallel fault propagation anticline, a multiple-bend fault-bend fold and a break-forward imbricate. Fracture conditions depend on structural evolution and specific site conditions. A case study of the Kulongshan Anticline in the Jiuquan Basin shows that our conceptual models match reality data very well.

Deformation geometry and timing of the Wupoer thrust belt in the NE Pamir and its tectonic implications

The Pamir region, located to the northwest of the Tibetan Plateau, provides important information that can aid the understanding of the plateau’s tectonic evolution. Here we present new findings on the deformation geometry and timing of the Wupoer thrust belt at the northeastern margin of Pamir. Field investigations and interpretations of seismic profiles indicate that the eastern portion of the Wupoer thrust belt is dominated by an underlying foreland basin and an overlying piggy-back basin. A regional unconformity occurs between the Pliocene (N2) and the underlying Miocene (N1) or Paleogene (Pg) strata associated with two other local unconformities between Lower Pleistocene (Q1) and N2 and between Middle Pleistocene (Q2-4) and Q1 strata. Results of structural restorations suggest that compressional deformation was initiated during the latest Miocene to earliest Pliocene, contributing a total shortening magnitude of 48.6 km with a total shortening rate of 48.12%, most of which occurred in the period from the latest Miocene to earliest Pliocene. These results, combined with previous studies on the Kongur and Tarshkorgan extensional system, suggest an interesting picture of strong piedmont compressional thrusting activity concurrent with interorogen extensional rifting. Combining these results with previously published work on the lithospheric architecture of the Pamir, we propose that gravitational collapse drove the formation of simultaneous extensional and compressional structures with a weak, ductile middle crustal layer acting as a décollement along which both the extensional and compressional faults merged.

Geometry and Kinematic Evolution of the Hotan-Tiklik Segment of the Western Kunlun Thrust Belt: Constrained by Structural Analyses and Apatite Fission Track Thermochronology

The western Kunlun thrust belt defines the boundary between the stable Tarim Basin in the north and the intensely deformed Cenozoic Tibetan Plateau in the south. Because of its important tectonic position, understanding its tectonic evolution should have important implications for propagation of deformation from Tibet to its neighboring cratonal regions during India-Eurasia convergence. We here present new structural analyses based on field investigations and seismic reflection profiles across the Hotan-Tiklik segment of the western Kunlun thrust belt. The results indicate that the structural section crosses two major thrust zones: the Tiklik zone in the hinterland to the south and the Hotan zone in the foreland to the north. Within these, the Hotan thrust zone is thin skinned, with its deformation characterized by fault-bend folding and fault slipping along detachment layers, whereas the Tiklik thrust zone involves basement, with its deformation driven by the currently steeply dipping Tiklik fault. Results from apatite fission track thermochronology in combination with growth strata and balanced cross section indicate that the Hotan-Tiklik segment underwent two-stage deformation: (1) development of the Tiklik thrust during the late Oligocene–early Miocene and again since the mid- to late Miocene and (2) activity of the Hotan thrust since the mid- to late Miocene as a result of basinward propagation of thrusting. The balanced cross section, combined with the apatite fission track results, suggests that the Hotan-Tiklik segment contributes a total shortening magnitude of more than ca. 34 ± 6 km. Within this, ca. 4 ± 2 and ca. 23 ± 1 km of the shortenings were absorbed by the Hotan anticline and the Hotan detachment fault, respectively, both of which were related to detachment layers. This suggests that detachment layers played an efficient role in propagating deformation from the western Tibetan Plateau into the Tarim Basin.

On the timing and forcing mechanism of a mid-Miocene arid climate transition at the NE margins of the Tibetan Plateau: stratigraphic and sedimentologic evidence from the Sikouzi Section

Abstract The Sikouzi Section is located towards the northern limits of the East Asian summer monsoon, providing the opportunity of placing the stratigraphic record into the context of the East Asian summer monsoon history. We present here the results of the details of the sedimentology of the Neogene succession of the section and use these to provide insights into the evolving history of the East Asian summer monsoon. The record is marked by a strongly expressed early Miocene lacustrine phase. A well-defined evaporate bed defines the top of the lacustrine succession, marking the onset of more arid conditions during the middle Miocene. The overlying succession is dominated by a series of alluvial packages, extending into the late Pleistocene with varying stratigraphic architectures and including a subordinate lacustrine component. Given the regional setting, the onset of drier conditions during the middle Miocene must relate to a downturn of summer monsoon activity. We focus on the question: what ‘forced’ this palaeoclimate event? Earlier biostratigraphic work places the explanation of this change into the context of the global-scale middle Miocene climate reorganisation. Here we explore this question in the context of regional-scale climate dynamics and propose that the onset of drier conditions over the study area was a response to atmospheric subsidence driven by circulation changes related to the growth of the Tibetan Plateau.

An Active East Asian Monsoon at the Oligocene-Miocene Boundary: Evidence from the Sikouzi Section, Northern China

The East Asian monsoon forms a significant element of the global climatic system. We here present detailed sedimentologic investigations of the Oligocene to early Miocene succession in the Sikouzi section, northern China, to determine monsoon evolution during this time. The particle-size characteristics and grain surface structures, in combination with the large-scale cross-bedding arrangements, graded bedding laminations, and small-scale deformation structures, type the Oligocene red beds in association I as eolian, attributable to large dune forms. Rare earth element results imply that the Oligocene sediments are possibly sourced from a local provenance in the West Qinling Mountains, excluding a more regional wind system during this time. Packages of thick-bedded dark-red mudstone/silty mudstone as well as subordinate medium-bedded pale-gray fine- to medium-grained sandstone and thin-bedded gypsum, with the massive mudstone/silty mudstone taking dominance, point to a lacustrine deposition with deeper-lake phases taking dominance for the early Miocene association II. This significant transition in depositional environments, while possibly linked to local tectonic and/or global eustatic events, is more likely to reflect a shift of regional paleoclimates from arid to more humid regimes. We attribute the shift to the impact of an active East Asian summer monsoon. Our results, combined with those for previously well-defined loess in the early Miocene, demonstrate activity (onset or possibly intensification) of an East Asian monsoon system around the Oligocene-Miocene boundary.

Major transgression during Late Cretaceous constrained by basin sediments in northern Africa: implication for global rise in sea level

The global rise in sea level during the Late Cretaceous has been an issue under discussion by the international geological community. Despite the significance, its impact on the deposition of continental basins is not well known. This paper presents the systematic review on stratigraphy and sedimentary facies compiled from 22 continental basins in northern Africa. The results indicate that the region was dominated by sediments of continental facies during Early Cretaceous, which were replaced by deposits of marine facies in Late Cretaceous. The spatio-temporal distribution of sedimentary facies suggests marine facies deposition reached as far south as Taoudeni-Iullemmeden-Chad-Al Kufra-Upper Egypt basins during Turonian to Campanian. These results indicate that northern Africa underwent significant transgression during Late Cretaceous reaching its peak during Turonian to Coniacian. This significant transgression has been attributed to the global high sea-level during this time. Previous studies show that global rise in sea level in Late Cretaceous may have been driven by an increase in the volume of ocean water (attributed to high CO2 concentration and subsequently warm climate) and a decrease in the volume of the ocean basin (attributed to rapid production of oceanic crust and seamounts). Tectonic mechanism of rapid production of oceanic crust and seamounts could play a fundamental role in driving the global rise in sea level and subsequent transgression in northern Africa during Late Cretaceous.