40 



STRUCTURAL GEOLOGY OF NORTH AMERICA 



of the Redwall limestone on Mazatzal land and the related increase in the 

 thickness of the red residual member of the Naco formation nearby (Huddle 

 and Dobrovolny, 1950). 



EASTERN INTERIOR BASINS AND ARCHES 



General Features 



Three basins of subsidence and sedimentation had become clearly 

 established by late Devonian time southeast of the Transcontinental Arch, 

 namely, the Michigan basin, the Illinois-Indiana-Kentucky basin (East- 

 ern Interior basin), and the West Virginia-Pennsylvanian basin (Appala- 

 chian basin). In Pennsylvanian time a fourth became defined, which is 





Fig. 5.1. Basins southeast of the Transcontinental Arch showing areas of sand accumulation 

 early Pennsylvanian time and the direction of stream transport. After Potter and Siever, 1956. 



called the Western Interior basin as a coal province, and the Forest City 

 basin as an oil province. See map, Fig. 5.1, and Plate 7. The Western 

 Interior and Eastern Interior basins were first so labeled when studied 

 as coal basins of Pennsylvanian age, and although the nomenclature is 

 not consistent with the state name applied to the Michigan basin, also a 

 coal basin, it is generally retained and used today. 



Appalachian Basin 



The history of the Appalachian basin is recounted in Chapter 7 in 

 connection with the Appalachian Mountains. As shown on the map, Fig. 

 5.1, it lies between the Valley and Ridge Province of the Appalachians 

 and the Cincinnati arch, but in its development its deepest part lay in 

 the mountainous belt; the eastern half of the basin became involved in 

 folding and thrusting in late Paleozoic time leaving the western half 

 relatively undeformed and what is now called the Appalachian basin. 

 See Figs. 8.11 and 8.12. It is filled with a remarkable succession of 

 miogeosynclinal and shelf strata ranging in age from Cambrian to 

 Permian. 



Michigan Basin 



In pre-Devonian time, the Michigan and Illinois-Indiana-Kentucky 

 basins were continuous; but beginning in the Devonian, the Kankakee 

 arch began to form, and the two basins became increasingly individual- 

 istic thereafter. The Michigan basin today is circumscribed by the 

 Great Lakes depressions on the west, north, and east, and by the Cin- 

 cinnati dome on the south. It consists of a sequence of beds representative 

 of all periods of the Paleozoic, cast in saucer fashion, each one of which 

 is smaller than the preceding on which it rests. The youngest strata are 

 thin and patchy red beds of either Upper Pennsylvanian or Permian age. 

 All Paleozoic strata are overlain and nearly completely blanketed by a 

 layer of glacial drift which ranges in thickness from a few feet to 1200 

 feet. As the basin subsided through the Paleozoic, its crystalline pre- 

 cambrian floor acquired the configuration shown in Figs. 5.2 and 5.3. 

 The total thickness of sediments in the basin is about 14,000 feet ( Cohee, 

 1948). 



