[Reports volI-XIII] . pears tobe merely the upper part of the main group of strata; and thefossils contained fully substantiated this view. A character-istic exposure is shown in the accompanying plate viii. An unconformity of the Saint Louis rocks upon the under-lying strata in Iowa and in the adjoining portions of the neigh- 72 GEOLOGICAL FORMATIONS boring states has been claimed by WMte*, but the recentevidence bearing upon the point is not near so conclusive aswould be desired. The differences in thickness of the limestonehave been alluded to already. This is due partly to the thinningout
[Reports volI-XIII] . pears tobe merely the upper part of the main group of strata; and thefossils contained fully substantiated this view. A character-istic exposure is shown in the accompanying plate viii. An unconformity of the Saint Louis rocks upon the under-lying strata in Iowa and in the adjoining portions of the neigh- 72 GEOLOGICAL FORMATIONS boring states has been claimed by WMte*, but the recentevidence bearing upon the point is not near so conclusive aswould be desired. The differences in thickness of the limestonehave been alluded to already. This is due partly to the thinningout of the strata northward, and partly to the subaerial erosionprior to the deposition of the Coal Measures of the region. Over all the northern area of the Saint Louis a character-istic brecciated rock is observable. But south of the Missouririver evenly bedded limestones are present, with occasionalextensive beds of oolite. In places, as at Ste. Genevieve,the oolitic limestones present perfect cross-bedding, such as is. Fig. 4. Cross-ljedding of Oolite. commonly seen in sandstones^a fact which is very suggestivein its bearing upon the origin of certain rocks of this kind. The faunal features of the Saint Louis are peculiar inmany respects, and quite distinct from those of both the over-lying and underlying strata, particularly from the latter. KASKASKIA, OE CHESTER, BEDS. Aux Vases Sandstone—In southern Illinois and southeast-ern Missouri, the Kaskaskia comprises extensive beds of lime-stone and shale. Everywhere over this district the calcareousportions, which greatly predominate in the lower part of the *Geology of Iowa, Vol. I, pp. 225-229. 1870. <J<so
Size: 2177px × 1148px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., boo, bookcentury1800, booksubjectgeology, booksubjectpaleontology
