History of the Carboniferous Sediments of the Mid-Continent Oil Field

Abstract

Obviously, the study of successive controlling geologic conditions and influences has many direct applications to the problems of the oil geologist with his duties of interpretation and prediction. The Carboniferous sediments of the Mid-Continent region were deposited upon a basement which was exceedingly well base-leveled but very complex structurally due to 10,000 feet of structural change during earlier Paleozoic, and far greater changes during pre-Cambrian times. Accumulation occurred mainly in shallow seas, hence practically at sea-level and without appreciable regional dip. Great inequalities in thickness required extensive structural changes within the basin areas, and the arrival of vast quantities of coarse material indicates equally extensive and concurrent uplift of areas around the basins. Such interrelation of negative and positive movements furnishes the basis for certain important deductions. Six successive groups of sediments are discussed as to character, location, thickness, and probable source. The oscillatory and migratory tendencies of these basins are noted and attendant structural effects discussed. Analysis of the various types of structure of this region is attempted, and maps are submitted showing net results of structural changes since (1) early Pennsylvanian and (2) Jurassic times. It is concluded that unequal subsidence and diastrophism caused by subcrustal pressures associated with successive basin subsidences best explain the ordinary oil field type of structure and the successive rejuvenations. The Ouachita geosyncline and synclinorium are considered the dominant features of the region, and a diagram is included indicating the successive developments in this area of greatest deposition, structural change, and erosion.