Neogene crustal shear zone along the western Gulf of Mexico margin and its implications for gravity sliding processes. Evidences from 2D and 3D multichannel seismic data

摘要

No significant crustal deformation was registered along the western Gulf of Mexico margin since the late Jurassic except the well known Cenozoic gravity tectonics. This is marked by a major extension across the platform and the upper continental slope compensated downslope by shortening across the Mexican Ridges fold belt. Based on extensive offshore 2D and 3D industrial multichannel seismic reflection data provided to us by PEMEX, we have evidenced significant Neogene deep-rooted deformation below the main decollement level (5 to 7 s-twtt) related to these gravitational processes. The main crustal deformation is outlined by a N170 degrees trending deep-seated reverse fault zone, which flattens downwards near the Moho and merges upwards near the main Oligo-Miocene decollement level, close to the Neogene Mexican Ridges fold belt. This deep seated fabric is interpreted as the result of a dextral strike slip fault zone rather steep and linear into the north and connecting southwards to a N150 degrees trending dextral wrench zone east of the Trans-Mexican volcanic belt. We consider that this Neogene transpressive dextral motion could have triggered gravity sliding along the Mexican Gulf margin. It could be located at the continent-ocean boundary and is probably linked to conjugate dextral slip related to the late Neogene N140 degrees trending left lateral slip along the Veracruz shear zone active since the Late Miocene. We discuss whether this deep thrust wrench zone is related with the eastward migrating Laramide orogeny front dated Paleocene-Eocene.