Abstract
AbstractThe timing and mechanisms of the Cretaceous sea incursions into Central Asia are still poorly constrained. We provide a new chronostratigraphic framework based on biostratigraphy and magnetostratigraphy together with detailed paleoenvironmental analyses of Cretaceous records of the proto‐Paratethys Sea fluctuations in the Tajik and Tarim basins. The Early Cretaceous marine incursion in the western Tajik Basin was followed by major marine incursions during the Cenomanian (ca. 100 Ma) and Santonian (ca. 86 Ma) that reached far into the eastern Tajik and Tarim basins. These marine incursions were separated by a Turonian‐Coniacian (ca. 92–86 Ma) regression. Basin‐wide tectonic subsidence analyses imply that the Early Cretaceous sea incursion into the Tajik Basin was related to increased Pamir tectonism. We find that thrusting along the northern edge of the Pamir at ca. 130–90 Ma resulted in increased subsidence in a retro‐arc basin setting. This tectonic event and coeval eustatic highstand resulted in the maximum observed geographic extent of the sea during the Cenomanian (ca. 100 Ma). The following Turonian‐Coniacian (ca. 92–86 Ma) major regression, driven by eustasy, coincides with a sharp slowdown in tectonic subsidence during the late orogenic unloading period with limited thrusting. The Santonian (ca. 86 Ma) major sea incursion was likely controlled by eustasy as evidenced by the coeval fluctuations in the west Siberian Basin. An early Maastrichtian cooling (ca. 71–70 Ma), potentially connected to global Late Cretaceous trends, is inferred from the replacement of mollusk‐rich limestones by bryozoan‐ and echinoderm‐rich limestones.
Highlights
The proto‐Paratethys Sea was a shallow epicontinental sea that extended across Eurasia from the Mediterranean Tethys to China
Considering the very large increase in tectonic subsidence in the east and marine incursion during an apparent eustatic lowstand from the west (Figure 6), we argue that tectonism must have been the main driver for the mid‐Cretaceous evolution of the Early Cretaceous and first major sea incursions
We related the Early Cretaceous invasion of the sea into the retro‐arc Tajik Basin to an increase in tectonic subsidence, caused by thrusting along the northern edge of the Pamir at ca. 130–90 Ma. This thrusting and increased subsidence were linked to coeval compressive deformation in the Pamir related to Neo‐Tethyan subduction and collisional events along the southern margin of Eurasia
Summary
The proto‐Paratethys sea incursions occurred during the Cretaceous and Paleogene until its drastic retreat during the late Eocene, followed by its isolation as the Paratethys during the Oligocene and Miocene (e.g., Kaya et al, 2019; Naidin et al, 1980; Popov et al, 2004). The fluctuations of this sea across Eurasia have shaped Asian paleoenvironments and provide a valuable record of Asian tectonism and eustatism (e.g., Bosboom et al, 2017, 2014; Carrapa et al, 2015; Hendrix et al, 1992; Kaya et al, 2019; Ramstein et al, 1997; Sun et al, 2016; Wang et al, 2019).
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