Can a propagating rift model finally explain all the peculiarities of the rift-drift evolution in the South Atlantic and in the Gulf of Mexico basins?

Abstract

At continental scale, a propagating rift model implies that at a given time, different margin segments occur in a different stage of rift development. In the direction of propagation, the rift is getting younger. Thus, it is possible that in the area where the propagation initiated the rift is already developed into a deep oceanic basin, while at the tip of the propagation the rift is still in the early stage of development and occurs above sea level. Clearly, at a given time, paleogeographic conditions along rifted continental margins, such as paleo-water depth, can be very different. A common work hypothesis, for example, in the Gulf of Mexico, is that salt represents the last syn-rift deposits and that no autochthonous salt was deposited over oceanic crust. We propose that the presence of autochthonous salt only tells us that the paleogeographic conditions were favorable for salt deposition along a given margin segment. More specifically, the paleogeographic requirements for salt deposition are (a) intermittent saltwater supply resulting in a restricted basin, and (b) subsidence below paleo sea-level, providing accommodation space for salt deposition. In simple terms, the salt has no knowledge about the nature of the underlying basement rocks, but it is very sensitive to the paleogeographic conditions. The “salt deposition window” is a well-defined time interval when salt can form along a margin. We propose that the amount of salt observed along a continental margin is directly related to the accommodation space available during the salt deposition window.

AAPG Datapages/Search and Discovery Article #90369 © 2020 AAPG Hedberg Conference, Geology and Hydrocarbon Potential of the Circum-Gulf of Mexico Pre-salt Section, Mexico City, Mexico, February 4-6, 2020