From the Guajira Desert to the Apennines, and from Mediterranean Microplates to the Mexican Killer Asteroid: Honoring the Career of Walter Alvarez
CONTAINS OPEN ACCESS
This volume pays tribute to the great career and extensive and varied scientific accomplishments of Walter Alvarez, on the occasion of his 80th birthday in 2020, with a series of papers related to the many topics he covered in the past 60 years: Tectonics of microplates, structural geology, paleomagnetics, Apennine sedimentary sequences, geoarchaeology and Roman volcanics, Big History, and most famously the discovery of evidence for a large asteroidal impact event at the Cretaceous–Tertiary (now Cretaceous–Paleogene) boundary site in Gubbio, Italy, 40 years ago, which started a debate about the connection between meteorite impact and mass extinction. The manuscripts in this special volume were written by many of Walter’s close collaborators and friends, who have worked with him over the years and participated in many projects he carried out. The papers highlight specific aspects of the research and/or provide a summary of the current advances in the field.
The ocean-continent transition of late synrift salt basins: Extension and evaporite deposition in the southern Gulf of Mexico and global analogs
Published:June 21, 2022
Mark G. Rowan, 2022. "The ocean-continent transition of late synrift salt basins: Extension and evaporite deposition in the southern Gulf of Mexico and global analogs", From the Guajira Desert to the Apennines, and from Mediterranean Microplates to the Mexican Killer Asteroid: Honoring the Career of Walter Alvarez, Christian Koeberl, Philippe Claeys, Alessandro Montanari
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Two-dimensional depth-migrated seismic data were used to interpret and analyze extension and salt deposition in the ocean-continent transition (OCT) along 720 km of the southern Gulf of Mexico rifted margin. The OCT is characterized by alternating areas of salt-filled, fault-bounded outer troughs overlying a shallow Moho and salt perched at a level above the top of oceanic crust. Normal faults and the limit of oceanic crust are both offset by two sets of transfer faults and paleo–transform faults, respectively, that trend NNW-SSE and N-S. The patterns define five OCT segments that show propagation of both rifting and spreading to the NE, an abrupt jump in pole location, and rifting/spreading nuclei that link up laterally. Salt was deposited during outer trough formation to the SW but prior to it in the NE, where salt consequently flowed from proximal locations into the growing trough during decoupled thick-skinned extension. The salt was deposited at least 0.5–1.5 km below global sea level, with precipitation initially confined to the oldest troughs (in the west) and subsequently spreading to cover the entire basin in a deep brine over a period of at least 5 m.y. Possible siliciclastic strata interbedded with the salt were likely sourced from the south and southeast, and hypersaline conditions waned gradually during punctuated marine flooding over another 5–10 m.y. The Gulf of Mexico was thus a giant evaporite basin formed in a deep depression during late-synrift mantle exhumation in a magma-poor setting, analogous to the South Atlantic salt basins and possibly the Red Sea and southern Moroccan/Scotian margins.