COUPLED GRAVITY SLIDING AND CRUSTAL MOTION DURING THE CENOZOIC ALONG WESTERN GULF OF MEXICO MARGIN: EVIDENCES FROM MULTICHANNEL SEISMIC DATA

The western margin of the Gulf of Mexico (GOM) Basin was initiated during the Upper Triassic. During the Late Jurassic, it is generally considered that the opening of the western Gulf was accommodated by the Western Main Transform (WMT) fault located along the present Mexican eastern continental slope, with counter-clockwise rotation of the Yucatán Block. In this paper, we document the existence of a Cenozoic tectonic reactivation of the margin that may have triggered the often described gravity sliding episode. Our study is based on offshore industrial multichannel seismic reflection data, provided by PEMEX. Along the GOM margin we identify a coupled system of shelf-wide extension initiated during the early Miocene and of deep water contractional growth-fold-belts (known as the Perdido and Mexican Ridges) associated with gravity sliding. The extensional system, located under the main décollement level (6 to 8s-twt), consists of NE-SW grabens passing progressively southward to a deep seated fault zone that often fits the N170° margin flexure. We interpret this fault zone, extended from Matamoros to Veracruz, as a major dextral strike-slip system that is strongly transtensional to the North and mainly transpressional to the South. We present evidence that the gravitational sedimentary collapse above the major décollement may have been triggered by the deep crustal faulting. The coupled extensional-shortening structures above the décollement appear to be causally related to the deep structural pattern. Finally, we discuss the existing link between this dextral N170° fault zone and the western termination of the active Polochic-Motagua fault system within the Gulf of Mexico geodynamic regional framework.