Unified basis for tectonic theory

Abstract

Five important principles are adopted as guides in developing a tectonic theory. These are: 1. (1) strike-slip motion is more important than any other kind. 2. (2) the crust is essentially a passive layer, riding on top of an active deeper zone. 3. (3) the degree of crustal deformation is, commonly, a greatly diminished measure of actual displacement at depth. 4. (4) the orientation of structural features such as faults and fold axes is more important than their relative sizes. 5. (5) present deformational patterns are typical, rather than unique, and therefore can be used as a key to tectonic history. These five principles are combined to produce a zonal rotation hypothesis for earth deformation. According to this hypothesis, the hierarchy of deformational units is as follows: 1. I. Equatorial belt, consisting of a variety of features, but specifically including a number of axisymmetric systems such as the Caribbean system which extends (north-south) from Cuba into Venezuela. The motion in each system is west-east, hence the entire belt is assumed to have a west-east acceleration. 2. II. The north Pacific plate, rotating in counter-clockwise fashion, as a result of being driven from the south by the equatorial belt. 3. III. Individual continents or fragments of continents, such as North America, which is circling the north Pacific plate — also in a counterclockwise direction, but at a retarded rate — as a result of drag along the Alaska-California coast. 4. IV. Smaller features, such as the Ouachita Mountains of Arkansas and Oklahoma, and the Alps. The two truly unique parts of the surface of the planet are the two junctions of the equatorial belt and the Pacific rim: 1. (1) a convergence zone, in the vicinity of the up-thrust Himalayan plateau. 2. (2) a divergence zone, in the vicinity of the subsiding, primarily tensional, Gulf of Mexico. The rate of displacement, through much of this four-level system, is on the order of 1 cm/year. Mountain systems of North America can be analyzed in terms of the theory. West Coast ranges are permanently active right-lateral structures, although perhaps they have experienced crescendoes at intermittent intervals. The Appalachians were more-or-less continuously active left-lateral structures only during late Precambrian and Paleozoic time, when they were the northern limb of an axisymmetric system in the equatorial belt. The Gulf Coast “geosyncline” has a long depositional history still ahead of it. The theory also predicts that the Pleistocene, if extended into the future to cover all immediately succeeding glaciations, has only begun. The force problem remains unsolved, but past attempts to resolve this difficulty have ignored several important facets of the problem. Regardless of the order of the forces involved, however, the present theory is no more handicapped than any other.