Paleozoic fault systems of the Tazhong Uplift, Tarim Basin, China

This report presents interpretations developed from a detailed study of new three-dimensional (3-D) high-resolution reflection seismic data in a portion of Tarim Basin. The tectonic history began with oceanic spreading during the Cambrian–Early Ordovician and continues beyond the Silurian–Devonian time of oceanic closure. Paleozoic faults of the Tazhong Uplift in the hinterland of Tarim Basin are capped by thick and undisturbed Meso-Cenozoic sedimentary sequences. Four Paleozoic fault systems have been recognized: (1) the Cambrian–Early Ordovician extensional faulting, (2) the Late Ordovician NWW trending thrust faulting, (3) the Silurian–Devonian NNE strike-slip faulting and (4) the Permian plutonism influenced by pre-existing fault planes. Zones of weakness created during Cambrian–Early Ordovician extensional faulting influenced subsequent tectonic movements. The Late Ordovician fault system divides the Tazhong Uplift into several deformation zones. Their mechanical characteristics vary across the study area, with stronger thrusting in the east. The Silurian–Devonian strike-slip fault system consists of three components: main faults, subordinate en echelon faults, and fault troughs. The main faults appear as steeply dipping, almost vertical, offsets on seismic map view, with associated flower structures on seismic profiles, together with other levels of faults. The Permian magmatic plugs have a spotty or bandy distribution, and are interpreted to have utilized former faults.