GEOLOGICAL POSITION OF NEWPORT CLIFF CONGLOMERATES. 371 



sures do not occur at intermediate localities. The absence of these con- 

 glomerates at Coddington Point is also puzzling. 



interpretation adopted. — So moderate a thickness of coarse conglomerate is 

 exposed in the fields northwest of Eastons Pond and west of Miantonomy 

 that it is impossible confidently to identify them with the much thicker 

 Purgatory conglomerate. The Miantonomy Hill and Coasters Harbor 

 Island exposures, on the contrary, suggest a much thicker section than 

 the field localities, and show pebbles of a size more nearly corresponding 

 with that of the coarse Purgatory conglomerate. For this reason the writer 

 considers the Miantonomy Hill exposure equivalent to the Purgatory con- 

 glomerate, the Coasters Harbor Island conglomerate being referred to the 

 same horizon. Whether the field exposures are to be considered as belonging 

 to the same general horizon or not is left, for the present, an open question. 



Geological position of the Newport Cliff section. The geological position of the 



Newport Cliff exposures presents another important question, to which an 

 uncertain answer must be returned. The conglomerate on Miantonomy 

 Hill pitches southward about 15°. If it has any representative southward 

 which is actually exposed, it is almost certainly the upper part of the New- 

 port Cliff section, toward Ochre Point. Here conglomerate occurs in layers 

 which are interbedded with a greater percentage of sandstone and shale 

 than is found in the Purgatory-Paradise or in the Black Point-Smiths 

 Beach coarse conglomerate sections. The pebbles, moreover, are commonly 

 not so large, although several layers with fairly large pebbles occur, and 

 locally some very large pebbles are found, a few exceeding 15 inches in 

 diameter. Some of the largest pebbles may be seen west of Ochre Point 

 in a very thin conglomerate layer, at the top of the conglomerate series. 

 The sandstones and shales interbedded with these coarser conglomerates are 

 more frequently greenish and brownish than similar rocks farther down in 

 the cliff section. 



If the upper and coarser conglomerate beds of the Newport Cliff sec- 

 tion be considered the equivalent stratigraphically of the Miantonomy 

 Hill section, the lower part of the Newport Cliff section at once demands 

 attention on account of its peculiar lithological characteristics. This part 

 of the section also contains frequent conglomerate layers, although the 

 pebbles are rather small or of only medium size. The interbedded sand- 

 stones are often darkened by the presence of carbonaceous matter, and the 



