Davis, Matthew H.¹, R. K. Goldhammer¹, Randall Marrett¹, Dan Lehrmann²
(1) University of Texas, Austin, TX
(2) University of Wisconsin-Oshkosh, Oshkosh, WI

ABSTRACT: A Field Study of Rift through Passive Margin Development and Laramide Deformation in Triassic and Jurassic Strata of the Sierra Madre Oriental, NE Mexico

Exposed near Galeana, Nuevo Leon are sedimentary deposits and contemporaneous structures that record the rifting and opening of the Gulf of Mexico, passive-margin development, and Laramide compression in the region. A mapping, sedimentologic, and structural study utilizing thin sections, measured sections, aerial photos and kinematics has produced a detailed stratigraphic section that records the transition from terrestrial to open-marine deposition and the orientation and timing of deformational events. Triassic to Early Jurassic red beds in the Huizachal Group are composed of fluvial and marine sands. The La Boca and La Joya Formations, respectively, are separated by a polymictic cobble conglomerate. Interbedded basal sandstone stringers and intercolated carbonates within the Callovian-aged Minas Viejas evaporate are the result of cyclic changes in sea-level during evaporite deposition. The increase in biodiversity in Upper Jurassic carbonates up through the Zuloaga Formation reflects the change from restricted to open-marine conditions. Rift-related tectonics and brittle extension features within the carbonates have been overprinted by Laramide orogenesis. The red beds have been folded and faulted into a broad Laramide anitclinorium with smaller intrusion cored folds having amplitudes on the order of 10’s of meters. Within the evaporite lies the decollement for Laramide thin-skinned deformation, thus there is a high degree of structural complexity represented in the overlying carbonates as tight folding patterns. By integrating concepts of depositional systems with structural deformation a picture of the stratigraphic and rifting kinematics of the Gulf of Mexico is developed along with the effects of Laramide deformation.

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.