--> Mechanics and Kinematics of the Perdido Foldbelt Toe, Northern Mexico

AAPG/SEG International Conference & Exhibition

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Mechanics and Kinematics of the Perdido Foldbelt Toe, Northern Mexico

Abstract

Abstract

The toe of the Perdido foldbelt in Mexico deforms above salt and shale detachments in the Jurassic Louann Salt and shales of the upper Eocene. There is a temporal and mechanical link between the allochthonous salt extrusion and foldbelt formation on the Eocene detachment. Imbricated fault-bend, fault-propagation and detachment folds are well-imaged on the upper Eocene detachment while steep limbed box and detachment folds are most common on the lower Jurassic detachment. The allochthonous salt and contractional toe of the foldbelt dictate the shape of the Neogene slope as they do throughout the Gulf of Mexico.

We show balanced structural cross-sections of the upper-detachment system that highlight the net structural shortening and thickening of the post-Eocene section, driven by gravitational processes from the prograding paleo-Rio Grande. We show that the principles of critical-taper wedge mechanics dictate that outboard clastic sediments build less structural taper (i.e. seafloor slope) than the allochthonous salt. The result is a complex, structurally-derived shape of the Neogene slope in the Perdido region. This relationship also sheds light on the mechanical properties and basal friction of both the allochthonous salt and Eocene shale detachment.