The major Late Albian transgressive event recorded in the epeiric platform of the Langshan Formation in central Tibet
Published:April 14, 2020
Yiwei Xu, Xiumian Hu, Marcelle K. BouDagher-Fadel, Gaoyuan Sun, Wen Lai, Juan Li, Shijie Zhang, 2020. "The major Late Albian transgressive event recorded in the epeiric platform of the Langshan Formation in central Tibet", Cretaceous Climate Events and Short-Term Sea-Level Changes, M. Wagreich, M. Hart, B. Sames, I. O. Yilmaz
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Global sea-level changes strongly impact within-basin depositional patterns and the evolution of palaeoclimate, palaeogeography and palaeoecology. During the long, worldwide ice-free period in the mid-Cretaceous greenhouse time interval, high-frequency global sea-level changes were recorded in sedimentary archives. However, the causes of these global sea-level changes are still debated. In central Tibet, the 1 km-thick Langshan Formation has been dated to the late Aptian to early Cenomanian based on larger benthic foraminifera and accumulated in an epeiric seaway, thus, it provides a good opportunity to reconstruct the sea-level change and their controlling factors. Eleven distinct microfacies corresponding to three sedimentary environments have been identified in the Langshan Formation. Calcispheres marlstone and bioclastic wackestone with calcispheres were deposited in an open marine environment; coral rudstone, rudist rudstone and benthic foraminifera–rudist wackestone characterize were deposited in a rudist bank environment; and orbitolinids floatstone–rudstone, green algae packstone, bioclastic grainstone, orbitolinids wackestone with small benthic foraminifera, spicules wackestone and small benthic foraminifera wackestone–mudstone were deposited in a lagoonal environment. The Langshan Formation accumulated on an epeiric platform. This unit documents a sudden deepening event from a rudist bank to an open marine environment during the late Albian (c. 107 Ma). Integrating these findings with regional data from the literature, we infer that this deepening event was a widespread, roughly synchronous feature across the globe, and was controlled by a global sea-level rise related to the decay of polar ice sheets or the release of water from continental aquifers.
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Cretaceous Climate Events and Short-Term Sea-Level Changes
CONTAINS OPEN ACCESS
Sea-level constitutes a critical planetary boundary for both geological processes and human life. Sea-level fluctuations during major greenhouse phases are still enigmatic and widely discussed in terms of changing climate systems. The geological record of the Cretaceous greenhouse period provides a deep-time view on greenhouse-phase Earth system processes that facilitates a much better understanding of the causes and consequences of global, geologically short-term, sea-level changes. In particular, Cretaceous hothouse periods can serve as a laboratory to better understand a near-future greenhouse Earth. This volume presents high-resolution sea-level records from globally distributed sedimentary archives of the Cretaceous involving a large group of scientists from the International Geoscience Programme IGCP 609. Marine to non-marine sedimentary successions were analysed for revised age constraints, the correlation of global palaeoclimate shifts and sea-level changes, tested for climate-driven cyclicities, and correlated within a high-resolution stratigraphic framework of the Geological Timescale. For hothouse periods, the hypothesis of significant global groundwater-related sea-level change, i.e. aquifer-eustasy as a major process, is reviewed and substantiated.