Tectonic Stratigraphy of Convergent Plate Boundaries: A Holistic Perspective from Paleozoic to Cenozoic Deepwater Systems of Western North America and the Gulf of Mexico

Paleozoic to Cenozoic deepwater systems of western North America record repetition in three phases of plate convergence inaccurately portrayed in static forearc basin models. Modern forearc basins record different phases of this dynamic continuum (e.g., Japan versus Andean types). Oceanic transform faults create volcanic headlands and vary phase along plate boundaries. These phases reflect:

1. Steep-slab subduction, high heat flow and igneous activity promotes high subsidence in a narrow forearc basin filled axially by volcanoclastic conglomerates in submarine channel fairways that parallel the basin axis and adjacent continental shelf; continental drainage directed away from the basin limits sediment derived from the magmatic arc;

2. Flat-slab subduction broadens forearc wavelength promoting a progressive decrease in basin subsidence. The basin fills with finer sediment and fewer lithics. Metamorphic and intrusive igneous clasts in conglomerates derived from the magmatic arc increase clast diversity in submarine channels oriented both transverse and parallel to the basin axis;

3. Transform plate boundaries, continental rifting, volcanism, unconformity development and extreme aridity (i.e., Triassic and Eocene red beds) follow flat-slab phases. This metastable plate boundary condition records the transfer, translation and accretion of exotic terrains contributing to the growth of accretionary prisms; trans-tensional and trans-pressional “pull-apart” basins have small footprints but thick fills when the forearc basin shuts down.

This tectonic stratigraphy is also reflected in source-to-sink correlations in the continental interior. Epeirogenic uplift of the Western Interior of North America, associated with eastward migration of continental magmatism in Permian and Paleogene and an increase in differential oblique subduction during the flat-slab phases, sourced deepwater systems recording long-distance, southward transport of predominantly fine-grained, sand-rich and feldspathic sediment.
 

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California