Abstract
In order to reveal the nature of the segmentation of Longmen Mountains Thrust Belt caused by the three nappes (Jiaoziding, Jiudingshan, and Baoxing Nappe), several methods are applied in this paper, including field investigation, seismic explanation and balanced crossed section, etc. Results of research reveal that nappes in Longmen Mountains vary in geometry, kinematics, and dynamics. Jiaoziding Nappe has generally behaved in a ductile manner, whereas Jiudingshan Nappe has been rigid, and the rheology of Baoxing Nappe has been intermediate between that of the other two nappes. The development of nappes has resulted in tectonic segmentation of Longmen Mountains: the main structural style of the northern segment is thrust faulting, with Jiaoziding Nappe representing a giant syncline. Given its ductility, it absorbed lots of stress, with the least amount of tectonic shortening in the SE part of the nappe. In the middle segment, the deformation is controlled by the rigid Jiudingshan Nappe, whose frontal area records lots of tectonic shortening. Deformation in the southern segment is intermediate in character between that of the other two segments, characterized by horizontal zonation, as demonstrated by fault development, and vertical stratification, which indicates that fault development was controlled by lithology.
Highlights
Located on the western edge of the Western Sichuan Foreland Basin, the Longmen Mountains Thrust Belt records polyphase deformation and is characterized by complicated structures [1] [2] [3] [4] [5]
This paper focuses on the long standing nappes and their implication on the tectonic characteristics and evolution of Longmen Mountains Thrust Belt and even Western Sichuan Foreland Basin which has largely been neglected in previous studies, so the mechanism of segmentation of the Longmen Mountains Thrust Belt is further investigated in terms of three main nappes in this paper; these nappes are described and analyzed in terms of their geometry and kinematics, and the control by nappes on segmentation of the thrust belt and the tectonic evolution of the Western Sichuan Foreland Basin
The three nappes vary in terms of lithology: the Jiudingshan and Baoxing nappes consist of migmatite, whereas the Jiaoziding Nappe is a giant syncline composed of Devonian, Carboniferous, and Permian
Summary
Located on the western edge of the Western Sichuan Foreland Basin, the Longmen Mountains Thrust Belt records polyphase deformation and is characterized by complicated structures [1] [2] [3] [4] [5]. Jin et al (2010) divided the Longmen Mountain Thrust Belt into three segments (northern, middle, and southern, separated by two transfer zones) based on seismic data and field surveys [9] [10]. This paper focuses on the long standing nappes (the Jiaoziding, Jiudingshan, and Baoxing nappes) and their implication on the tectonic characteristics and evolution of Longmen Mountains Thrust Belt and even Western Sichuan Foreland Basin which has largely been neglected in previous studies, so the mechanism of segmentation of the Longmen Mountains Thrust Belt is further investigated in terms of three main nappes in this paper; these nappes are described and analyzed in terms of their geometry and kinematics, and the control by nappes on segmentation of the thrust belt and the tectonic evolution of the Western Sichuan Foreland Basin
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