Structural Origin and Evolution of Mississippi Fan Foldbelt, Gulf of Mexico

Paul Weimer, Richard T. Buffler

The Mississippi fan foldbelt is a series of east-trending anticlines associated with primarily north-dipping thrust faults in the northern Gulf of Mexico. The foldbelt is approximately 300 km in length and a minimum of 50 km in width. The folds contain strata of Middle Jurassic through Pliocene(?) age, based upon correlations with deep Gulf of Mexico seismic units (Challenger, Campeche, lower and upper Mexican Ridges, and Cinco de Mayo). The series of thrust faults and anticlines becomes younger basinward to the south and formed localized, confined turbidite basins in the adjacent synclines to the north. This foldbelt represents the compressive toe of a complete growth fault system where updip sediment loading caused downdip compression and decollement formation. The fold reflect where the decollement ramps up.

A major reflection in the middle of the Miocene(?) upper Mexican Ridges unit marks the beginning of growth of the foldbelt. This reflection, in the undeformed basin to the south, is a major downlap surface for sediments being derived from the growing anticlines. Updip to the north, the anticlines acted as basin margins to trap incoming sediments, and this reflection marks the first onlap surface for the localized sediments within the confined basins.

The older sediments of the Mississippi fan (upper Pliocene-lower Pleistocene) pinch out against the foldbelt, indicating the foldbelt formed a major topographic barrier after its formation and influenced the early sedimentation in the Mississippi fan. The structurally highest folds are truncated by deep marine erosion. Some of the younger Mississippi fan sequences locally decrease in thickness across the foldbelt, indicating minor recurrent growth on the foldbelt during the Pleistocene. The foldbelt contains several potential reservoir intervals, including shallow-water Jurassic carbonates to Miocene-Pliocene turbidites, and has high petroleum potential.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.