Page 61 - Carbonate Facies in Geologic History

48 The Stratigraphy of Carbonate Deposits

Presen distribution
m Limestone m Morine shale .' Morine sandstone
Probably deposited but now eroded or obscured
~ Limestone EJ Marine shale

Fig. II-24. Facies map of Upper Ordovician strata in North America. After Clark and Stearn
(1968) illustrating the widespread single argillaceous carbonate sheet across the Midcontinent
and Cordilleran miogeosyncIine. In the Midcontinent and western regions this unit directly
overlies an equally widespread and lithologically similar pure carbonate unit-the Red River,
Bighorn, Viola-Montoya. Fine brick pattern indicates the carbonate facies. Coarser brick
marks, eroded areas where the unit formerly extended. Note the Appalachian Queenston
delta along eastern border of craton. Illustration from Geological Evolution of North Amer-
ica (2nd Edition) with permission of authors and The Ronald Press, New York City

marine orthoquartzites and glauconitic oolitic limestones, represent residual (or
lag) strata formed by repeated marine transgressions and regressions across the
shelves and during times of relatively slow sedimentation.
Other single, uniform units may represent widespread stable marine condi-
tions and consist of members deposited more or less at the same time. The Middle
and Upper Ordovician west of the Mississippi River contain two lithosomes
which fall in this category. The Red River-Viola-Montoya shallow marine car-
bonate unit and the overlying shale, Stoney Mountain-Maquoqueta-Sylvan, are