About This Item
Share This Item
A mature Precambrian topography in southeastern Missouri having a maximum relief of more than 2,000 ft was buried by Late Cambrian and Ordovician sediments, but is now extensively resurrected by stream erosion. Peripheral dips in sedimentary strata adjacent to the buried topography of as much as 34° are shown to be limited in lateral extent, and are interpreted as due mainly to the compaction of carbonate muds by as much as 25%.
Detrital igneous material ranging in size from fine sand to large boulders is locally abundant in some sedimentary units. Sedimentary breccias are common at the margins of depositional basins bordered by Precambrian ridges. These breccias are attributed by Snyder and Odell to submarine sliding on slopes of as little as 4°. Algal and stromatolite reef facies are developed at the margins of the depositional basins, and appear closely related to the Precambrian topography which apparently existed as islands or shoal areas in early Paleozoic seas.
Joints and fractures developed in sedimentary strata exhibit both radial and tangential orientation with respect to the configuration of the buried hills. Comparison with results of model experiments by Cloos and Beloussov, and theoretical analysis support a concept of origin in which tensional stresses developed in the sediments during compaction.
The area of these stratigraphic and structural features constitutes a unique "laboratory of exposures" which provides opportunities for comparison with facies encountered in deep drilling elsewhere in the Mid-Continent.
End_of_Article - Last_Page 644------------