STRUCTURE AND TECTONIC OF THE WAGNER BASIN IN THE GULF OF CALIFORNIA USING MULTICHANNEL SEISMIC REFLECTION PROFILES

The Wagner Basin is the northernmost marine basin within the Gulf of California rift system. This basin accommodates transtensional strain along the Pacific and Northamerican plate-boundary. The basin trends NNE-SSW along 40 km and 20 km wide with a maximum depth of 210 m. We interpret the subsurface structure by using high-resolution multichannel seismic reflection data collected at one and six seconds two-way travel time (TWTT).

Correlation of faults and seismostratigraphic horizons indicates that the basin is a half-graben controlled by the Wagner Fault along the eastern flank of the basin. The Wagner Fault is 30 km long and strikes NNW with the downthrown block to the west. This western flank is affected by flexion of the seismostratigraphic horizons, which are tilted by rollover folds likely related to antithetic and synthetic faulting of the Wagner Fault. It is an apparent listric structure that dips ~79° to the NW at shallow depths and decreases gradually in dip to ~58° at 0.6 s TWTT and ~28° after 1.8 s TWTT. The strike of the secondary faults is to the NE. It is mainly of oblique movement and less than 10 km in length. The northwestern slope of the Wagner Basin is also influenced by N-NNE oblique (?) faults which dip mainly to the east. This N-NNE trending fault system is interpreted as a distinctive structural domain, here called the Wagner-Cerro-Prieto domain (WCPD), which transfers strain from the Wagner Fault to the Cerro-Prieto Transform Fault (CPTF). The interaction zone between WCPD and CPTF occurs over a zone ~20 km wide around ~31.35N. It separates the northwestern segment of the Cerro Prieto fault (active zone) from the now inactive segment to the SE, which suggests a possible evolution of the CPTF system toward NW. Both segments of the Cerro Prieto Fault are well constrained by seismic epicenters. The structural framework that controls the subsidence of the basin is not the northernmost system that transfers the deformation directly to CPTF. Instead of that, the interaction between the Wagner Fault, the WCPD, and the CPTF suggest that a large amount of strain is still transferred to the Cerro Prieto Fault through an additional en-echelón array of oblique (?) faults which would be at the NNW of the Wagner Basin.