Salt rock behaves as a fluid and can play a pivotal role in the large-scale, long-term collapse of the world's continental margins. However, the precise way in which this occurs is laced in controversy; nowhere is this controversy more apparent than along the Brazilian continental margin, where the origin of a feature called "the Albian Gap" has generated much heated debate over several decades.
Albian Gap is a zone in the Santos Basin, offshore Brazil, up to 75 kilometers wide and within which the Albian section is missing.
In study, Christopher A-L. Jackson and colleagues enter this debate, critiquing the geological and geophysical evidence forwarded in support of the two main competing genetic models, post-Albian extensional faulting (the extension model) and as an Albian salt structure evacuated in response to loading by post-Albian sediments (the expulsion model). Their study suggests that much of this evidence is not diagnostic of either model and that a revised model is required.
They propose a revised model for the evolution of the Albian Gap that invokes Albian thin-skinned extension and post-Albian salt expulsion. Although their results are unlikely to be universally accepted, they at least will stimulate ongoing debate regarding the origin of this enigmatic structure.
Citation: C. A-L. Jackson et al., 'Understanding passive margin kinematics: A critical test of competing hypotheses for the origin of the Albian Gap, Santos Basin, offshore Brazil', Geology 19 May 2015; DOI:10.1130/B31290.1
