Abstract
Many large paleo-lakes in North China were formed after the Triassic Era. Seawater incursion events (SWIEs) in these lakes have been extensively discussed in the literature, yet lack reliable methodology and solid evidence, which are essential for reconstructing and confirming SWIEs. The present study employs specific marine biological markers (24-n-propyl and 24-isopropyl cholestanes) to trace SWIEs in a dated core taken from the Songliao Basin (SLB). Two SWIEs were identified. The first SWIE from 91.37 to 89.00 Ma, was continuous and variable but not strong, while the second SWIE from 84.72 to 83.72 Ma was episodic and strong. SWIEs caused high total organic carbon (TOC) and negative δ13Corg values in the sediments, which were interpreted as an indication of high productivity in the lake, due to the enhancement of nutrient supplies as well as high levels of aqueous CO2, due to the mixing of alkaline seawater and acidic lake water. The SWIEs in SLB were controlled by regional tectonic activity and eustatic variation. Movement direction changes of the Izanagi/Kula Plate in 90 Ma and 84 Ma created faults and triggered SWIEs. A high sea level, from 90 to 84 Ma, also facilitated the occurrence of SWIEs in SLB.
Highlights
Many large paleo-lakes in North China were formed after the Triassic Era
The present study employs specific marine biological markers (24-n-propyl and 24-isopropyl cholestanes) to trace SWIEs in a dated core taken from the Songliao Basin (SLB)
SWIEs caused high total organic carbon (TOC) and negative d13Corg values in the sediments, which were interpreted as an indication of high productivity in the lake, due to the enhancement of nutrient supplies as well as high levels of aqueous CO2, due to the mixing of alkaline seawater and acidic lake water
Summary
P. et al Discovery of Late Cretaceous foraminifera in the Songliao Basin: Evidence from SK-1 and implications for identifying seawater incursions. M. C30-steranes, novel markers for marine petroleums and sedimentary rocks. M. et al Sedimentary 24-n-propylcholestanes, molecular fossils diagnostic of marine algae. X. Chronology of the terrestrial Upper Cretaceous in Songliao Basin, northeast Asia. H. The floating astronomical time scale for the terrestrial Late Cretaceous Qingshankou Formation from the Songliao Basin of Northeast China and its stratigraphic and paleoclimate implications. J. et al Marine incursion events in the Late Cretaceous Songliao Basin: constraints from sulfur geochemistry records. The Molecular Biomarker Study of The Depositional Environments of Nenjiang Formation of Upper Cretaceous in Songliao Basin PhD dissertation, Graduate Univ. S. et al Late Cretaceous climate changes recorded in Eastern Asian lacustrine deposits and North American Epieric sea strata.
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