Depositional Patterns and Tectonic Setting of Early Tertiary Basins in the NE Margin of the Tibetan Plateau: A Case Study of the Nangqian and Xialaxiu Basins

ZHOU Jiang-yu; WANG Jiang-hai; YIN An; Spurlin M S; Horton B K

Many red Early Tertiary basins are exposed in the northeastern margin of the Tibetan Plateau due to intracontinental deformation and uplift induced by the Indo-Asian collision. Based on detailed mapping and sedimentologic investigations of two Early Tertiary basins, Nangqian and Xialaxiu, and combining with the comprehensive analysis of tectonism, sedimentation and magmatism, two stages for the tectonic and depositional evolution of the basins are revealed, i.e. the early stage is controlled by thrusting and characterized by coarse-grained alluvial-fan clastic sediments at the bottom and local magmatic activities; and the late stage is controlled by strik-slip and pull-apart and characteristic of fine-grained lacustrine-delta gypsum- sandstones and mudstones interbedded with thin-bedded limestones and widespread igneous activities. There is a clear episodic evolution resulting from the basin tectonic framework, the thickness and structure of sedimentary sequences, sediment constituents and magmatism. The data of the basin paleocurrent and ⁴⁰ Ar/ ³⁹ Ar dating for igneous rocks in the basins suggest that the sediments in the early Tertiary basins were formed in the period of Late Eocene-Early Oligocene (38～29 Ma). Depositional patterns and magmatic activities in the Early Tertiary basins in the NE margin of the Tibetan Plateau were controlled by thrusting and strike-slipping in the early period of the Indo-Asian collision.

1 Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640;

2 Institute of Earth Resources, China University of Geosciences, Wuhan 430074;

3 Department of Earth & Space Sciences, University of California, Los Angeles,California CA90095, U.S.A;

4 Department of Geology & Geophysics, Louisiana State University, Louisiana, Batonrouge LA70803, U.S.A

Received Date: 2001-01-08

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Abstract: Many red Early Tertiary basins are exposed in the northeastern margin of the Tibetan Plateau due to intracontinental deformation and uplift induced by the Indo-Asian collision. Based on detailed mapping and sedimentologic investigations of two Early Tertiary basins, Nangqian and Xialaxiu, and combining with the comprehensive analysis of tectonism, sedimentation and magmatism, two stages for the tectonic and depositional evolution of the basins are revealed, i.e. the early stage is controlled by thrusting and characterized by coarse-grained alluvial-fan clastic sediments at the bottom and local magmatic activities; and the late stage is controlled by strik-slip and pull-apart and characteristic of fine-grained lacustrine-delta gypsum- sandstones and mudstones interbedded with thin-bedded limestones and widespread igneous activities. There is a clear episodic evolution resulting from the basin tectonic framework, the thickness and structure of sedimentary sequences, sediment constituents and magmatism. The data of the basin paleocurrent and ⁴⁰ Ar/ ³⁹ Ar dating for igneous rocks in the basins suggest that the sediments in the early Tertiary basins were formed in the period of Late Eocene-Early Oligocene (38～29 Ma). Depositional patterns and magmatic activities in the Early Tertiary basins in the NE margin of the Tibetan Plateau were controlled by thrusting and strike-slipping in the early period of the Indo-Asian collision.

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Depositional Patterns and Tectonic Setting of Early Tertiary Basins in the NE Margin of the Tibetan Plateau: A Case Study of the Nangqian and Xialaxiu Basins

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