Stereo and Mosaic Aerial Photo Study of Central Ouachita Mountain System in Oklahoma and Arkansas: ABSTRACT

Abstract

A careful study of stereo aerial photographs of a central part of the Ouachita Mountains in Oklahoma and Arkansas, followed by a related study of photo-index sheets of a much larger area in the Ouachitas, yields the following tentative conclusions: 1. The earliest structural dislocations of field dimensions are a series of approximately parallel bedding faults in the Stanley Shale, increasing in numbers downward in the section. A slight schistosity, also nearly parallel with bedding, may likewise increase downward. Some large overthrusts may have formed at this time. The prime source of this deformation was probably an underthrusting basement moving northward. 2. The next recognizable tectonic movements were uplifts of three main anticlinoria, although these could have followed episode 3. At this time the Ouachitas began to shed much coarse and finer clastic sediments toward the west and probably in other directions. 3. The next major episode seems to be steep faulting probably involving the basement and overlying sediments, producing semi-fault-block structures with tight broken anticlines; this was followed by a collapse of the sediments into deep synclines. Most of the high synclinal and more complicated ranges have straight or gently curved bordering faults in the adjacent lowlands. 4. The Mid-Continent regional uplift which included the Ouachitas must have produced a flood of coarse clastics adjacent to the mountains. These tectonic conglomerates have been removed by subsequent deep erosion, but their distal equivalents--the Garber, Duncan-San Angelo, and Whitehorse sands--are present in the Lower and Middle Permian of western Oklahoma and the western part of north-central Texas. 5. The nearly vertical Big Cedar fault extends nearly 200 mi from near Big Cedar, Oklahoma, to Jacksonville, Arkansas, northeast of Little Rock. It probably was formed during a period of relaxation or tension in Jurassic or Cretaceous time, and roughly parallels other faults in the coastal plain in southwest Arkansas. The Big Cedar fault touches 9 or 10 separate local structures along its length. End_of_Article - Last_Page 422------------