discovery of upper cretaceous neo tethyan trench deposits in south tibet luogangcuo formation

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Late Cretaceous-Eocene exhumation of the northern Lhasa terrane and topographic implications for the Central Tibet

The central Tibetan Plateau has an average altitude of ∼5000 m; its exhumation and chemical weathering greatly influence the global climate and ocean chemistry. The modern central Tibet is characterized by low-relief, high elevation topography with endorheic drainage. When and how these geomorphic characteristics of central Tibet were initiated remains controversial. Here, we have applied zircon Usingle bondPb dating and low-temperature thermochronology on the Cretaceous plutons from Coqin Basin of central Tibet in order to assess timings of exhumation. The thermal history modeling indicates a period of relatively rapid cooling (2.5–4 °C/Ma) occurred in Late Cretaceous to Middle Eocene times (from ∼80 Ma to ∼40 Ma), with the exhumation rates of 0.2–0.4 mm/yr assuming a geothermal gradient of 25 °C/km. Cooling rates then slowed to ∼0.5 °C/Ma during the Middle Eocene to the present, with a relatively lower exhumation rates of ∼0.02–0.03 mm/yr. Synchronous rapid cooling and exhumation has also been identified in central Tibet; this signal of widespread Late Cretaceous exhumation across the region may be viewed as evidence for the initial surface uplift and erosion of the central Tibetan plateau. Lower exhumation rate since ∼40 Ma, combined with sedimentological data suggests that the low-relief, internally drained topography of central Tibet was initiated around this time

Modeling hyperthermal events in the Mesozoic-Paleogene periods: a review

Hyperthermal events, which are characterized by rapid and extreme warming, occurred at several points throughout the Mesozoic to Paleogene periods. Model simulation studies have been conducted to investigate the mechanisms behind these events, including the carbon fluxes required to drive observed warming and isotope dynamics, the impact of warming on continental weathering, seawater pH, ocean anoxia, and the mechanism that terminated the warming. Studies using simple box models, Earth system box models, or 3D Earth system models have suggested that warming had a significant biogeochemical impact and would enhance continental weathering, increase ocean anoxia, and drive marine acidification. However, the magnitudes of these impacts remain debated and require further modeling work, as do the reconstructions of carbon fluxes and compositions. This review provides an overview of the current state of knowledge on hyperthermal events and proposes possible modeling development directions to better understand the causes and impacts of these events. Particularly, new long-term ‘semi-spatial’ Earth system models are promising tools for providing new solutions and perspectives on the biogeochemical responses to warming events and the carbon fluxes behind hyperthermal events from the Mesozoic to Paleogene periods

Late Cretaceous to Late Eocene Exhumation in the Nima Area, Central Tibet:Implications for Development of Low Relief Topography of the Tibetan Plateau

Much of the interior of the Tibetan Plateau is characterized by internal drainage, low relief topography, and high altitude. How and when this landscape formed is controversial. In this study, we use new zircon U-Pb data and low-temperature thermochronological data (apatite and zircon [U-Th/He], apatite fission track [AFT]) from the Late Cretaceous to Cenozoic Nima Basin sedimentary rocks and Xiabie granite in the adjacent Muggar Thrust hanging wall (part of the regional Shiquanhe-Gaize-Amdo thrust system), to determine the paleodrainage and timing of exhumation in the region. Individual AHe and ZHe cooling ages range from 9 to 60 Ma and 58 to 118 Ma, and the AFT ages range from 30 to 90 Ma. The thermal history derived from the Northern Nima Basin sediments and Xiabie granite require a period of exhumation between 70 and 40 Ma in the thrust fault hanging wall, and 40 and 30 Ma in the Nima Basin. Across the region, this event was followed by low rates of exhumation and the deposition of locally sourced sediment, lacustrine, and evaporitic deposits that are indicative of an internal drainage system. We suggest that the exhumation event is associated with development of thrust-elevated relief that may have disrupted the drainage network favoring the development of an endorheic system. This system, sediment accumulation, and/or post-30 Ma tectonic quiescence led to the generation of low relief topography

Carbonate-platform response to the Toarcian Oceanic Anoxic Event in the southern hemisphere : Implications for climatic change and biotic platform demise

We are grateful to Zhifei Liu for TOC and analyses at the Tongji University. We thank also Wei An, Bo Zhou and Shiyi Li for their assistance in the field, and Zhicheng Huang, Yiwei Xu and Weiwei Xue for their help in the laboratory, and Chao Chang, Tianchen He and Bolin Zhang for their helpful discussion. Hugh Jenkyns commented on a draft of the manuscript. We would also like to thank Editor Derek Vance, Christopher Pearce and two anonymous reviewers whose comments greatly improved the manuscript. This study was financially supported by the National Natural Science Funds for Distinguished Young Scholar in China (41525007) and the Chinese MOST 973 Project (2012CB822001). DBK acknowledges support of NERC Fellowship NE/I02089X/1. This is a contribution to the IGCP 655.Peer reviewedPostprin

Marine rapid environmental climatic change in the Cretaceous greenhouse world

The Cretaceous Period serves as a relevant model to understand greenhouse climate evolution. As atmospheric CO2 concentrations continue to rise in the twenty-first century, critical questions put forward are 1) how the Cretaceous Earth System could have been maintained in the “greenhouse” state, if there are some variations, 2) why and how fast did climatic and palaeoenvironmental changes happened during the Cretaceous, and 3) what records were preserved in the Earth's archives that enable the comparison of Cretaceous rates of paleoenvironmental changes with today's global changes. In fact, rapid and severe global environmental and climatic changes happened in the Cretaceous greenhouse world including oceanic anoxic events, oceanic red beds, “cold snaps” or glaciations and carbonate platform drowning events. This special issue originated from the final workshop of UNESCO International Geoscience Program IGCP 555 and the Pardee session of the Geological Society of America 2010 annual meeting. Participants and contributors mainly focused on the causes, processes, and consequences of rapid environmental/climatic changes that happened in the Cretaceous greenhouse world

A dataset of sandstone detrital composition from Qinghai‐Tibet Plateau

Abstract As a hot topic in Earth sciences, the Qinghai‐Tibet Plateau has accumulated a large amount of sedimentary‐related data. We constructed a dataset of detrital components for Qinghai‐Tibet Plateau from 63 peer‐reviewed publications. The dataset thus comprises 1813 Late Proterozoic to Pleistocene sandstones from 84 stratigraphic units. For each sample, we present details on reference, detrital composition, GPS, geographic location, depositional age, tectonic setting and depositional environment. It becomes a high‐quality dataset after the information on each sandstone sample was standardized and reviewed by sedimentary experts. The dataset can be used for regional geoscience studies, exploring the general laws of the source‐to‐sink process. The dataset may also be useful in the field of utilities, such as assisting in finding suitable building stones, helping oil and gas and mineral exploration, and so forth

Stratigraphic transition and palaeoenvironmental changes from the Aptian oceanic anoxic event 1a (OAE1a) to the oceanic red bed 1 (ORB1) in the Yenicesihlar section, central Turkey

We performed a detailed study of the stratigraphic transition from the early Aptian oceanic anoxic event 1a (OAE1a) to the oceanic red bed 1 (ORB1) along the pelagic Yenicesihlar section in the Mudurnu region of central Turkey. The Selli-equivalent level of the OAE1a (approximately 2.1 m thick) consists of black to dark-grey shales interbedded with grey marlstones with total organic carbon contents up to 2.05%. The carbon isotopic record shows a negative excursion (C3 stage, 0.58 m in thick) at the bottom of the Selli-equivalent black shales and a stepwise positive excursion (C4 to C6 stages, 1.52 m in thick) within the Selli-equivalent black shales. The OAE1a-ORB1 transitional interval (similar to 20.3 m in thick) displays an alternation of light-grey limestones with grey marls or shales that links the anoxic environment of the Selli-equivalent black shales at the bottom and the highly anoxic environment of the ORB1 at the top. The OAE1a-ORB1 transition corresponds to stable carbon isotopic C7 and C8 stages, and based on the cyclostratigraphy, the transition lasted for approximately 1.3 Myr, which is very close to the duration of the OAE1a (1.1-1.3 Myr). The delta O-18 values in the transitional interval are variable and generally show an increase towards the ORB1, when the climate became relatively cool