Monte M Swan¹, Stanley B. Keith², Thomas L Thompson³

(1) MagmaChem, L.L.C, Evergreen, CO
(2) MagmaChem, L.L.C, Bellevue, WA
(3) Thompson Geo-Discovery, Inc, Boulder, CO

ABSTRACT: Foreland Basin Analysis Based on Stratotectonic, Crustal Oxidation State and Wet Zone Studies in the Arc and Foreland of the Cordillera of North and South America

This paper describes a new approach to analysis of foreland basins developed originally for the mineral industry, but with obvious applications to oil and gas exploration. Based on petrochemistry of Cordilleran arcs adjoining foreland basins, it provides an empirical linkage to practical exploration that has eluded the plate tectonic model. It addresses basin analysis through the use of the geologic tools listed below.

1. Direct connection of oceanic transform fractures (in light of buoyancy contrasts) to continental basement structures and subducted oceanic slab tears.

2. Delineation of slab segmentation under continental crust through petrochemical analysis of magmatic arcs. This identifies panel-like geologic provinces on the continent.

3. Stratotectonic (time-distance) sections as well as time-slice maps for individual panels of crust. These provide a highly-resolved geologic framework for dynamic basin modeling.

4. Crustal oxidation state maps that delineate major structures, terranes, and basement-controlled redox stability of oil and gas both regionally and within basins.

5. Identification of deep, wet, permeable zones (active basement structures) through contouring of "wetness" of igneous rocks and mineral systems. These fluids, if reduced, commonly carry dissolved non-biogenic hydrocarbons.

6. Analogy to numerous studies of igneous rock differentiation series suggests that lateral shear strain which characterizes Cordilleran continental margins causes subhorizonatal migration of petroleum fluids along pressure gradients transverse (not parallel) to extensional fractures.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado