ABSTRACT: Contrasting Foreland Responses to Compression, Northern Margin of the Tarim Craton, Northwestern China

MCKNIGHT, C. L., Baylor University, Waco, TX, S. A. GRAHAM, and E. R. SOBEL, Stanford University, Stanford, CA, and Z. X. WANG, Institute of Geology, Chinese Academy of Geological Sciences, Beijing, China

The Tarim craton is a Precambrian crustal block surrounded by Phanerozoic mobile belts. Throughout the northern craton margin, Mesozoic and Cenozoic tectonics have been strongly affected by the earlier history of the craton. During early Paleozoic time, extension resulted in the development of a passive margin on the north side of the craton; in later Paleozoic time, this margin became an accretionary margin. The docking of the Tarim craton on the southern margin of paleo-Asia at the end of the Paleozoic Era initiated the rise of the ancestral Tian Shan mountain range to the north. Succeeding collisions farther south resulted in repeated episodes of north-directed compressional stresses. Transmitted through the rigid blocks into the heart of central Asia, these stresses were focused i the previously deformed mobile belts. Compression in the Tian Shan resulted in episodic uplift and shortening across the range and in the adjacent foreland basins.

The Tarim craton is broken into a number of fault-bounded structural blocks, and styles of foreland shortening on the northern margin of the craton differ among these domains. The Kalpin uplift is a basement high with a relatively thin sedimentary cover. This basement block acted as a buttress against advancing Tian Shan thrust sheets, and no mountain-front foredeep developed in the area. In the south, the basement block is faulted over adjacent cratonal blocks, creating deep, localized Mesozoic-Cenozoic depocenters within the craton interior.

In contrast, the Kuqa depression is a basement low loaded by south-vergent Tian Shan thrust sheets. The depression is a major Mesozoic-Cenozoic mountain-front foredeep bounded on the south by the North Tarim basement uplift.

The differences between the Kalpin uplift and the Kuqa depression can be traced to contrasting responses of Tarim basement to compression. In the Kalpin uplift area, basement was forced up; in the Kuqa depression area, basement was forced down.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)