Abstract

Sedimentological and stratigraphic studies of seven stratigraphic sections of Permian Hongyanchi (HYC) and Quanzijie (QZJ) low-order cycles (LCs) in the Tarlong-Taodonggou half graben and Dalongkou area in Bogda Mountains, NW China, demonstrate effective approaches and methodology in cyclo- and time-stratigraphic analyses of complex fluvial-lacustrine deposits in an intracontinental rift setting. A new synchronous stratigraphic unit, the lower QZJ LC is defined. The lower and upper boundaries of this cycle include a regionally correlative disconformity, erosional unconformity, and conformity, across which significant and abrupt changes in palaeoenvironments and tectonic and climatic conditions occurred. The lower boundary is an erosional unconformity and disconformity with a high-relief topography that juxtaposes lacustrine deposits of the underlying HYC LC with the overlying meandering stream deposits of the lower QZJ LC, and was caused by a regional tectonic uplift. The upper boundary is a disconformity and local erosional unconformity and conformity, juxtaposing stacked paleosols developed on fluvial sediments with overlying fluvial and loessial deposits of the upper QZJ LC. The paleosols indicate landscape stability and a prolonged period of subaerial exposure and minimal deposition and suggest that climatic conditions were semi-arid with strong precipitation seasonality in the Tarlong-Taodonggou half graben and subhumid in the Dalongkou area. The fluvial-loessial deposits indicate a renewed tectonic uplift and a change in the atmospheric circulation pattern. The newly-defined lower QZJ LC facilitates accurate palaeogeographic reconstruction in the study area during a period of major tectonic and climatic changes. The interpreted tectonic and climatic conditions provide a critical data point in the mid-latitude east coast of NE Pangea during the Mid-Permian icehouse-hothouse transition. The results demonstrate that a process-response approach is effective in time-stratigraphic analysis of complex fluvial-lacustrine strata in a highly-partitioned rift basin.

Department(s)

Geosciences and Geological and Petroleum Engineering

Comments

Open Access funded by China University of Petroleum (Beijing) under a Creative Commons license.

Keywords and Phrases

China; Cyclostratigraphy; Fluvial; Loess; Permian

Geographic Coverage

NW China

Time Period

Permian

International Standard Serial Number (ISSN)

20953836

Document Type

Article - Journal

Document Version

Final Version

File Type

text

Language(s)

English

Rights

© 2015 China University of Petroleum Beijing, All rights reserved.

Creative Commons Licensing

Creative Commons License
This work is licensed under a Creative Commons Attribution-No Derivative Works 4.0 License.

Included in

Geology Commons

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