Climbing-Ripple Cross-Lamination of the Early Oligocene Yaxicuo Group in the Hoh Xil Basin and Its Significance for Depositional Environment

LIU Zhi fei; WANG Cheng shan; JIN Wei

The climbing ripple cross lamination is especially well developed and widely distributed in the early Oligocene Yaxicuo Group sandstone of the Hoh Xil Basin, northern Tibetan Plateau. The small scale cross lamination is formed from the upward movement of sediment, when the source quickly provides too much new sediment. Two types of climbing ripple cross lamination, i.e. erosional stoss Type A and depositional stoss Type B1, are included in the Yaxicuo Group sandstone. Among that, a single set of Type A is about 2 cm in thickness and less than 7° for its climb angle; but a single set of Type B1 is about 4 cm in thickness and around 10° 20° for its climb angle. Three kinds of flows including non uniform, unsteady, and non uniform unsteady flows, which belong to sandy clastic flow and bottom flow, contributed their formation. The mean fluid velocity is generally 11 60 cm/s and the sediment deposition rate may be up to 0.1 g/cm₂ s. The depositional environment is the delta front in shallow lake. The development of the Yaxicuo Group climbing ripple cross lamination could be under conditions of the early Oligocene uplift process of the Tibetan Plateau and global cooling and drying climate change.

Climbing-Ripple Cross-Lamination of the Early Oligocene Yaxicuo Group in the Hoh Xil Basin and Its Significance for Depositional Environment

1. Laboratory of Marine Geology, Tongji University, Shanghai200092;

2. School of Earth Sciences, China University of Geosciences, Beijing 100083;

3. Institute of Sedimentary Geology, Chengdu University of Technology, Chengdu610059

Received Date: 2003-11-20

Rev Recd Date: 2004-03-28

Publish Date: 2004-12-10

Key words:

Abstract: The climbing ripple cross lamination is especially well developed and widely distributed in the early Oligocene Yaxicuo Group sandstone of the Hoh Xil Basin, northern Tibetan Plateau. The small scale cross lamination is formed from the upward movement of sediment, when the source quickly provides too much new sediment. Two types of climbing ripple cross lamination, i.e. erosional stoss Type A and depositional stoss Type B1, are included in the Yaxicuo Group sandstone. Among that, a single set of Type A is about 2 cm in thickness and less than 7° for its climb angle; but a single set of Type B1 is about 4 cm in thickness and around 10° 20° for its climb angle. Three kinds of flows including non uniform, unsteady, and non uniform unsteady flows, which belong to sandy clastic flow and bottom flow, contributed their formation. The mean fluid velocity is generally 11 60 cm/s and the sediment deposition rate may be up to 0.1 g/cm₂ s. The depositional environment is the delta front in shallow lake. The development of the Yaxicuo Group climbing ripple cross lamination could be under conditions of the early Oligocene uplift process of the Tibetan Plateau and global cooling and drying climate change.

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Reference (13)

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Climbing-Ripple Cross-Lamination of the Early Oligocene Yaxicuo Group in the Hoh Xil Basin and Its Significance for Depositional Environment

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