Geophysical Interpretation and Formation Mechanism of the Yandang Low Uplift in the East China Sea Shelf Basin
The Yandang Low Uplift is a significant tectonic unit of the East China Sea Shelf Basin, which has previously received little attention. Based on the geophysical interpretation of seismic, gravity and magnetic data, Mesozoic distributions and basin structures are studied in this work to reveal formation mechanism of the Yandang Low Uplift. Our results show that the Yandang Low Uplift is characterized by a series of circular gravity highs which trend NE in free air gravity anomaly map and residual gravity anomaly map, but magnetic lows of about −60∼–160 nT in △T magnetic anomaly map, including some magnetic highs caused by magma intrusion. The uplift lies between the Oujiang Sag and the Minjiang Sag along a discontinuous NE-trending axis, about 170 km long and 15∼50 km wide. Jurassic and Cretaceous strata are widely distributed on the uplift, with a thickness of about 500∼1500 m, and cover a total area of about 5000 km2 with some local absence. The Oujiang Sag distinctly differs from the Minjiang Sag in the structure of Mesozoic basin. The former is a typical faulted basin bordered by En-echelon faults to the east, where Mesozoic half-grabens and tilted fault blocks are well developed. However, the latter is a down-warped basin with few faults and igneous rocks, where Mesozoic compressional anticlines, faulted anticlines and inverted structures are well developed. Above all, this study deduces that the Yandang Low Uplift is a palaeo-uplift comprised of Proterozoic strata and distinct from the Taipei Low Uplift. Furthermore, the Yandang Low Uplift and the Zhe-Min Uplift might be joined in a single entity in Jurassic, and divided into two parts in late Cretaceous.