Imaging the Sedimentary and Crustal Structure of the Luoyang Basin, Central China, Using a Dense Nodal Seismic Array

Abstract

The Luoyang basin lies in the southern margin of the North China block, separating the trans-North China orogen to the north and the Qinling-Dabie orogen to the south. Determining how the basin formed is important for understanding the history of the North China block and its evolution during the Mesozoic and Cenozoic times. Based on the teleseismic data recorded by a dense nodal seismic array, we used the receiver function method to image the sedimentary and crustal structures in the Luoyang basin. Common conversion point stacking images show that the Moho is at a depth of ∼35 km on the south and west sides and slightly uplifted to ∼30 km below the northeastern basin. Two sets of P-to-S conversions are imaged in the shallow crust, separating the near-surface sediments into consolidated, semiconsolidated, and unconsolidated layers. The top of the consolidated sedimentary layer is close to the surface at the southern basin and present at a depth of ∼2 km beneath the central basin, then deepens to a depth of ∼3 km below the northern basin. The discontinuous interface in the sediments indicates that the sedimentary layer was truncated by some blind north-dipping normal faults. The northeastward thinning crust, thickening sedimentary layers, and dipping normal faults together indicate that the Luoyang basin evolved in association with the deep crustal extension response to the lithospheric thinning of the North China block. By superimposing the deep crustal extension, we propose that the present-day landform of the Luoyang basin was also shaped by fluvial erosion at the surface, which was accompanied by the expansion of Yihe and Luohe riverbeds during the Quaternary.