. Geology of the Narragansett basin. Geology. 168 GEOLOGY OF THE NARRAGA^SBTT BASIN, Fossils.—^North of the station black shales contain impressions of Sphe- nophjlhm scMotheimii, both alone and with Asterophyllites equisetiformis, Pecopteris, smaller than P. unitaj also occurs here. In the mudstones on the bluff calamites are abundant. In the rocky points and islets along the shore near Silver Spring the dips steepen to 45"^, rising to an anticline arching over the upper narrow- end of Narragansett Bay—the southward continuation of the fold which is more clearly indicated by the outcrops
. Geology of the Narragansett basin. Geology. 168 GEOLOGY OF THE NARRAGA^SBTT BASIN, Fossils.—^North of the station black shales contain impressions of Sphe- nophjlhm scMotheimii, both alone and with Asterophyllites equisetiformis, Pecopteris, smaller than P. unitaj also occurs here. In the mudstones on the bluff calamites are abundant. In the rocky points and islets along the shore near Silver Spring the dips steepen to 45"^, rising to an anticline arching over the upper narrow- end of Narragansett Bay—the southward continuation of the fold which is more clearly indicated by the outcrops on the sides of the Seekonk River. The southward extension of this anticline is not readily traceable. The sandstones and conglomerates reappear in the ledge at the present mouth of the Pawtuxet River, and again at Rocky Point, on the west side of the bay. It is evident from a diag- nosis of the dips in Provi- dence and East Providence that the strata in this section, from the western boundary eastward into the middle of Fig. 23.—Theoretical section of folded structure on western margin of the -^q basiu bchaVO VCrV mUch Narragansett Basin, a, Providence anticlinal belt; 6, East Providence ^ •/ jBat synoline; Bock anticline. (See PL LXXXII, figs, f-i, jjl tho manUCr of the layCrS Thirteenth Ann, Eept F. S. OeoL Survey, Part II.) " under horizontal pressure in the clay models experimented upon by Mr. Bailey Willis.^ The general structure of a cross section from back of Providence southeastward to Riverside is represented in the accompanying diagram, fig. 23. It will be noticed that there is a belt of very highly tilted strata next the resisting pre-Carboniferous terrane, in which the effects of great pressure are mani- fest also by the degree of metamorphism; thence eastward lies a belt of little-disturbed strata without any marked metamorphism or even slaty cleavage; there come in then subordinate anticlines with a slight amount of rock crushing. These two
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Keywords: ., bookcentury1800, bookdecade1890, bookpublishe, booksubjectgeology
