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The AAPG/Datapages Combined Publications Database

Utah Geological Association

Abstract


Proceedings of the First International Conference on the New Basement Tectonics, 1974
Pages 169-182

Ortho-Polygonal Tectonic Patterns in the Exposed and Buried Precambrian Basement of Southeast Missouri

Geza Kisvarsanyi, Eva B. Kisvarsanyi

Abstract

The evolution of the Ozark uplift in southeast Missouri is a function of the deformation of its Precambrian basement. The Precambrian core of the dome is part of the Central Stable Craton of the Midcontinent. Fracturing and faulting of the craton commenced in Precambrian time and continued in the Paleozoic, resulting in doming and regional tilting of the area. The dominant structural pattern developed by block faulting, fault planes, fractures, and joints define a mosaic of polygons. Tectonic movements developed horst structures, grabens, square-shaped basins, and exposed basement rocks creating a series of “high” knobs and inter-knob “lows.”

The major lineament pattern of the area is defined by the integration of surface geologic structure, distribution and erosional patterns of exposed basement rocks, contact relationships, strike directions of basic dikes and other igneous bodies, location of ore deposits, and subsurface geologic data. Airphotos, aeromagnetic maps, and ERTS-1 imagery are used to complement the geological integration method. The major lineament systems are classified as structural lineaments that controlled the emplacement of intrusive bodies, ore deposits, and dikes during the Precambrian. Some of these ancient fracture and fault systems were rejuvenated in Paleozoic and later times.

The dominant set of structural directions, observed in the field and on airphotos, is a diagonal system of N 45° E and N 45° W trending faults and joints. It is responsible for the square-shaped distribution pattern of igneous knobs and sedimentary basins. A less significant axial set of structural elements follows N 0–25° E and N 65–90° W directions. Complementary faults and fractures of lesser importance complete the polygonal tectonic pattern of the basement complex. Large circular features of possible volcano-tectonic origin have been discovered by remote sensing techniques. Mega-lineaments of sub-continental size are superimposed on the local system of deformation.

Uniformity and regularity of structural elements suggest that the Precambrian basement was geomechanically rigid and homogeneous at the time of its basic deformation, Indications are that the greatest principal stress axis was essentially vertical when normal faulting developed and doming occurred, and that it was horizontal when strike-slip movements took place. Spatial and temporal distribution of intrusive bodies, dikes, lava flows, and mineral deposits are strongly affected by the tectonic evolution of the area.

The regular, repetitive pattern of lineaments is characteristic of the Midcontinent basement. These trends are probably related to the major regmatic fracture-fault pattern of the continent itself.


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