Early Mesozoic Basin Development and Its Response to Thrusting in the Yanshan Fold-and-Thrust Belt, China

Abstract

Mesozoic basins in the Yanshan belt of northern China record two episodes of shortening during the Late Triassic and Late Jurassic that span the transition from retroarc deformation and basin formation to continental intraplate deformation. Gravel braided river depositional systems in the Upper Triassic Xingshikou Formation show provenance from the north and become relatively more distal southward onto the North China Block. These relationships are interpreted as a foreland basin system, southward of a retro-arc, and later collisional, fold-thrust belt. The Triassic basin shows widely correlative stratigraphy, simple proximal-to-distal relationships, and uniformly southdirected paleocurrents that suggest a simple integrated foreland basin. In contrast, the Upper Jurassic Tuchengzi Formation is characterized by coarse conglomerates with rapid facies changes, lateral non-uniformity, and local provenance, which argues for deposition in a broken foreland setting, with local high-gradient depositional systems dominant.