Part I—Orogenic Movements in Anadarko Basin
This paper attempts to clarify controversial articles regarding the age and magnitude of deformation in the Anadarko basin, diastrophism which seems to have occurred at different times and in varying intensity across the Mid-Continent region. Evidence is cited and inferences defended to support the following sequence of events: (1) the appearance and rejuvenated arching of the Central Kansas and Ozark uplifts, upon which converged (northward with increasing interruption) deposits of Cambrian to pre-Mississippian age out of an original basin centering in southern Oklahoma: (2) an episode of regional tilting and broad gentle warping that successively beveled off northward the Hunton to Arbuckle sequence; (3) the advent of full-scale orogeny in post-Morrow pre-Des Moines (early Pennsylvanian time) which established the Amarillo, Wichita, Arbuckle, and Ouachita uplifts (increasing in deformation from west to east) and the adjoining Anadarko, Ardmore, and McAlester basins on their flanks; (4) rejuvenated faulting, warping, and over-thrusting, culminating in late Pennsylvanian and early Permian time, that re-elevated these features as well as northwest-trending adjustment axes in the adjoining basins to locally reëxpose basement rocks which contributed a thick and widespread arkose fades to contemporaneous deposition.
Thus, the Anadarko basin, defined in origin as post-Morrow pre-Des Moines in age and in outline as flanked by the Amarillo-Wichita-Arbuckle uplifts and Nemaha ridge on the east was involved in numerous Paleozoic movements on the north flank which have no counterpart on the south flank. This is the same contest of simultaneous, world-wide orogenic dogma that is more and more frequently raised by geologists.
The pattern of differential crustal shortening with maximum compression to the east in the Ouachitas encourages a new concept: that contraction of the crust in continental areas bordering the Gulf of Mexico may explain the pronounced positive gravity anomaly of that area indicative of a basaltic, high-density floor and an absence of granitic crust, conceivably withdrawn during deformation of surrounding orogenic belts.
Part II—Contracting Continents—A Theory
Geologists have revived their search for a concept that will replace the extremes of “permanent” and “drifting” continents and ocean basins by means of “foundering” or the gravitational withdrawal of crust from the Pacific to create our satellite moon—a theory that will relate accumulating geophysical and geological facts bearing upon the derivation of continents, ocean basins and orogenic belts. Such a theory must explain (1) the localization of continents from the logically assumed crustal shell of granitic material originally covering the surface of the earth, (2) the presently existing contrast in physical properties and relief of continents and ocean basins, (3) the strategic position of major orogenic belts within and paralleling the margins of the continents and their relation to similar structural trends in the continental nuclei, or shield areas, (4) the distribution of critical organisms, dependent on climate and dry land, whose similarity of morphology requires land connections between widely separated continents.
This theory of contracting continents on the face of a shrinking globe accounts for the great ocean basins by the withdrawal of the original granitic crust from these areas during the processes of orogenesis and crustal shortening in which successive belts of deposition and diastrophism were folded and thrust toward pre-existing shield areas which acted as buttresses to contraction from all directions because they had been stabilized in pre-Cambrian time by intense deformation, injection and re-crystallization. If Paleozoic to recent crustal shortening measurable in the mappable sediments and basement rocks could not explain a sufficient withdrawal of crustal material from the ocean basins, it is obvious that the creation of the pre-Cambrian continental nuclei must have already begun to differentiate the continents and ocean basins.
On the North American continent, orogenic belts are peripheral to the shield, have counterparts in the lineation of shield structures, and border the continental margins which they evidently have established. If the continents contracted and withdrew crust during successive movements into late Cenozoic time, it is conceivable that suitable land connections for organic migration existed throughout much of Paleozoic to Recent time.
This theory also seeks to explain specifically, (1) the Gulf of Mexico, a pronounced and unexplained positive gravity anomaly, as a typical ocean basin devoid of its granitic veneer, withdrawn by crustal shortening of Mid-Continent and Tertiary orogenic movements on the north and south, (2) the Mediterranean, a comparable anomaly, by crustal shortening most pronounced on the north in the Alpine structural system, (3) the other great ocean basins by the process of peripheral orogenic contraction of the adjoining continents, for example, the Cordilleran and eastern Asiatic (Himalayan) systems, resulting in tensional by-products of volcanic islands, earthquakes, and vulcanism bordering the Pacific basin.