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Mesozoic Basins of Mexico

James Lyons

The University of Texas at Austin,

Jackson School of Geosciences

[email protected]

Some current hypotheses define the Guerrero Flysch Basin of western Mexico as an exotic volcanic arc terrane. However, much evidence supports the model of in place deposition as a marginal basin formed along an early Mesozoic rifted margin to Mexico’s craton. The principle expression of this rift is the Cananea-Inde structure which separates the Precambrian and Ouachita age basement from the deep basin sediments. Additional evidence includes basement ridges within the basin sediments representing basement blocks of the extended crust and possible ultramafic ocean crust of the basin floor. Boron and molybdenum chemistry variations in hydrothermal systems across the structural boundary also support major crustal discontinuity across it. Transpressional dislocation of basement and sediments along the western North American continent complicate the history of the basin.

Numerous intracratonic basins developed within Mexico’s crustal platform during the early Mesozoic. These filled with Jurassic volcanic rocks, clastic debris from the platforms and evaporites. Cretaceous carbonate and shale completed filling the basins and covering most of the platforms. Laramide shortening resulted in isoclinal folding and thrusting of supracrustal rocks within the Mesozoic basins while open anticlinal and monoclinal folding dominates the platforms. The abrupt change from basin inversion structures to more modest platform deformation delineates the basin-platform margins more accurately than facies and wide spaced drilling more commonly utilized. The distribution and intensity of the fold belts and oroclines of the Sierra Madre Oriental of Mexico reflect the inversion of the underlying basins and the degree of shortening of each basin.

AAPG Search and Discovery Article #90060©2006 AAPG Foundation Grants-in-Aid