Long-term fluvial archives in the Fen Wei Graben, central China, and their bearing on the tectonic history of the India-Asia collision system during the Quaternary

摘要

Staircases of large-scale river terraces are striking features of the landscape in the Fen Wei Graben, adjacent to the Qinling orogenic belts, central China. Field investigations indicate that all five river terraces are composed of a basal channel gravel and an overlying, thick loess palaeosol succession. As Chinese loess stratigraphy has been well studied, it favours age determination of these terraces and their correlation with the marine oxygen isotope stages. Our research indicates that the ages of the five terraces are approximately 2.6, 1.2, 0.9, 0.65, and 0.15Ma, respectively. The formation of these river terraces within the Fen Wei Graben has been attributed to NW-SE crustal extension, associated with left lateral displacement between the North and South China Blocks, in response to the northward movement of India towards Asia since Cenozoic time. Thus, the stepped terraces in the Fen Wei Graben reflects elements of the India-Asia collision systems, in which terraces define episodes of accelerated northward movement of India towards Asia during the Quaternary. (c) 2004 Elsevier Ltd. All rights reserved.