Structural Characteristics of Luonan Basin Based on Gravity Data

Abstract

The Luonan Basin is a typical intermountain basin in the Qinling orogenic belt. The tectonic characteristics of the basin and its adjacent areas are very complex. Previous studies on Luonan Basin mainly focus on paleontology and sedimentation, and lack of reports on basin studies using geophysical data. In order to study the tectonic characteristics of Luonan Basin, this paper collected 1:500000 gravity data in the study area, and used the sliding average filtering method to separate the remaining gravity anomalies from the Bouguer gravity anomalies, and analyzed the causes of gravity anomalies. In this paper, the normalized total horizontal derivative vertical derivative, total horizontal gradient mode and vertical second derivative are used to infer the faults in the study area by referring to the remaining Bouguer gravity anomalies and geological data. According to the inferred results and geological data, the boundary of the basin is determined. Three gravity profiles across the basin were fitted by a 2.5D human-computer interaction inversion method. The results show that the high gravity is caused by the basement uplift, and the low gravity is the reflection of the Meso-Cenozoic and low-density intrusive rocks. The faults in the study area are mainly in NE, NW and nearly EW directions. The development of the basin is controlled by the basin margin faults. The east-west length of the basin is 85km, the maximum north-south width is 7km, and the basin area is 420km². Cretaceous, Paleogene and Neogene are mainly developed in the basin. The basement depth of the basin is "deeper in the middle than in the west, and deeper in the west than in the east", with the maximum depth of about 1130m.