Seismic evidence for lithospheric boudinage and its implications for continental rifting

The continental rifting that precedes the breakup of a continent and the formation of a new ocean basin is one of the key processes of plate tectonics. Although often viewed as a two-dimensional process, rifted margins exhibit significant variations along strike. We document along-strike variations developed during the ca. 200–160 Ma continental rifting that formed the margins of the Gulf of Mexico ocean basin. Rayleigh-wave ambient noise tomography reveals a zone of high and low seismic velocity resembling large-scale geologic boudins in the mantle lithosphere of the northwestern Gulf of Mexico margin. These features become progressively less prominent eastward following the transition from a magma-poor to a magma-rich passive margin. We infer that mantle refertilization and thickness of the pre-rift lithosphere control deformation style and the along-strike variations in continental rifting. Our results also suggest that deformation during rifting produces long-lived features that persist long after breakup and, therefore, can be used to study rifted margins globally.