Keywords and Phrases
Depositional sequence model; Nonmarine Basin; Sequence stratigraphy; Zhangjiatan Shale Bed
"Detailed sequence stratigraphic and depositional systems analyses can effectively delineate factors and processes controlling deposition of fine-grained lacustrine sediments. Upper Triassic Zhangjiatan (ZJT) Shale Bed and adjacent strata in Ordos foreland basin was used as an example. A new depositional sequence model shows that the maximum regressive shoreline was more landward than that at the lowest lake-level. The study area is on the ramp margin, covering 100x90 km2. Thin sections, cores and well-logs of 80 wells are used to calibrate log signatures, document lithofacies, and interpret depositional facies in a sequence stratigraphic context. The entire sequence thickens from 25 m in the NE to 160 m in the center, and thins to 55 m in the SW, suggesting a NW-SE-oriented elongate lake basin. The shoreline transgressed from the WSW corner northeastward outside the study area, and then regressed farther basinward than the initial shoreline. Ten environmental facies were interpreted. The lowstand systems tract constitutes a high-order sequence and is dominated by fluvial facies, including incised valley, lakeplain, and overbank. Lacustrine deposits are dominated by the high-order highstand prodeltaic to delta front facies. The transgressive systems tract is dominated by lacustrine sublittoral, littoral, beach, to supra-littoral facies. The highstand systems tract is dominated by prodeltaic to delta front deposits, which are partially eroded. Lake-level variations may have been the dominant control on the development of the two-order Zhangjiatan sequence, and combined with depositional topography and variation of sediment supply, dictated shoreline positions and the stratigraphic architecture of the sequence"--Abstract, page iii.
Wronkiewicz, David J.
Geosciences and Geological and Petroleum Engineering
M.S. in Geology
Missouri University of Science and Technology
x, 142 pages
© 2015 Qiuwan Yu, All rights reserved.
Thesis - Open Access
Library of Congress Subject Headings
Sedimentation and deposition -- China
Geology, Stratigraphic -- Triassic
Paleogeography -- China
Electronic OCLC #
Yu, Qiuwan, "Paleogeographic and paleoenvironmental evolution of lacustrine and fluvial Upper Triassic Zhangjiatan shale sequence, Ordos Basin, China" (2015). Masters Theses. 7487.