Modelling of a high-resolution Moho geometry from a synthetic gravity field data for tectonic studies over southeastern Nigeria

Mapping of the Moho geometry could serve as an effective tool for visualization of the tectonic features/processes and their interactions beneath a region of interest. In this study, we employed a high-resolution (25′′×25′′ grid) tailored Bouguer gravity data to explore the mechanisms of tectonism beneath a highly rifted continental plate of the Southeastern Nigeria. Hence, we separated the Bouguer gravity data into shallow (high-pass) and deep (low-pass) gravity signals before carrying out gravimetric inversion. To obtain suitable estimates of gravimetric inversion parameters (reference depth and density contrast), we numerically computed and stochastically evaluated a seismically and our gravimetrically determined crustal thickness until a minimum RMS of their differences was achieved. Our obtained crustal thickness data range from 22 to 36 km with a stochastically determined optimal reference depth of 26 km and density contrast of 0.45gcm^-3. The crustal thickness map reveals a dense magmatic feature traversing the central portion of the study area in northeastern, southeastern, and southwestern directions leading to the thinning of the crust in those regions. We have been also able to refine and depict the lateral extent of the different sub-basins, ridges, crustal architecture, and the geophysical processes (magmatism, faulting/fracturing, mantle uplift, crustal thinning/thickening) of continental separation within the study area from our crustal thickness map. Considering the fine-scale discontinuity and continuity of tectonism revealed in our crustal thickness map, we conclude that a narrowing of two or more conjugate plates might have mainly occasioned those visible and complex geophysical phenomena.

The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)