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Kansas Geological Survey, Subsurface Geology 12, p. 53

Paleotectonic control of reservoir facies

D. L. Baars
Kansas Geological Survey

It has been well established that the basement structural fabric of the Paradox basin (Utah and Colorado) affected sedimentary facies throughout Phanerozoic time. Continental-scale conjugate basement wrench-fault zones, originally activated during 1.7 to 1.6 Ga, were rejuvenated repeatedly throughout the Paleozoic. The Paradox pull-apart basin was formed along the northwest-southeast-trending Olympic-Wichita lineament in Middle Pennsylvanian time, facilitated by basement faults of the northeast-southwest-trending Colorado lineament. These continental-scale basement lineaments conform to a global regmatic structural fabric that has been well documented in Precambrian and younger rocks. Structurally controlled shoaling conditions, formed by reactivation of basement faults, fostered marine-sandstone reservoirs in Late Devonian time, crinoidal Waulsortian buildups in the Early Mississippian, and phylloid-algal mounds in Middle Pennsylvanian time.

Apparently similar basement wrench-fault zones, dating at about 1.1 Ga, are present in Kansas. The midcontinent rift system is a north-northeast/south-southwest-trending fault zone that was reactivated several times during the Paleozoic. Northwest-southeast-trending faults along the Central Kansas-Bourbon arch complex seem to have offset structures of the midcontinent rift Both trends are interpreted to be continental-scale conjugate wrench-fault zones, with sinistral displacement along the midcontinent rift and dextral displacement along the Central Kansas-Bourbon arch complex. Stratigraphic relationships suggest a long history of reactivation prior to Middle Pennsylvanian uplift and erosion of the major structural features.

In both regions, major structural lineaments are associated with smaller scale rhomboidal fracture patterns, drag-related en echelon folds, and complex, mutually offsetting fault patterns, especially in areas of intersecting basement structures. Reactivation of these structural features through time created unconformity-bounded trapping conditions at several stratigraphic intervals, and structurally controlled water-depth variations localized algal accumulations in Pennsylvanian carbonates.

Evidence is accumulating in Kansas that tectonically controlled paleotopography and paleobathymetry are major predictable factors in reservoir localization. Recognition of reactivated regmatic basement structural fabrics is important to facies and reservoir analysis and can provide significant constraints on reservoir characterization and modeling.

Kansas Geological Survey
Comments to
Web version May 11, 2010. Original publication date 1989.