SAKDSTOE^ES WEST OF SAKONNET EIYBE. 357 



no longer present, and if ever in existence here must have been removed 

 by erosion. At (4) Eastons Point greenish shales verging to bluish are well 

 exposed beneath the coarse conglomerate on both sides of the anticline. 

 The greenish shales of all these localities are believed to represent the top 

 of the great Aquidneck shale series. This does not mean that all of the 

 greenish shales elsewhere also belong to this upper horizon. The greenish 

 shale of the western part of Bristol Neck certainly belongs low in the shale 

 series, and not at the top, but along the middle length of Aquidneck Island, 

 from the Portsmouth syncline to Eastons Point, such a north-south line of 

 green shales near the top of the Aquidneck shales can be recognized. 



SAKOKNET SANDSTOISTES OF THE AQUIBKECK SERIES VTEST OF THE 



XXX V JtSjJK. 



West of the line of npper green shales just described the corresponding 

 upper layers of the Aquidneck shale series are not greenish in color, but show 

 the more usual dark-blue tinge. This is certainly true beneath the Mian- 

 tonomy Hill and Coddington Point conglomerates, where the underlying 

 shales seem to represent the same horizon. Eastward of the line of npper 

 green shales described there are other exposures of the upper shales of the 

 Aquidneck series, which are also occasionally green in color — ^for instance, 

 north of the conglomerate area at Fogland Point. But usually the more 

 eastern exposures of the ripper Aquidneck series fail to show a marked 

 shaly character; on the contrary, they more frequentlj^- become moi'e 

 sandy in some of their layers, or even take on the general character of a 

 sandstone series, in which shales form only the subsidiary beds. When this 

 occurs, the finer sandstones usually contain considerable carbonaceous 

 material. Such shales with a predominating amount of dark-gray or 

 blackish sandstones are found at the top of the Aquidneck shale series and 

 beneath the coarse conglomerates along the shore north of Black Point, 

 and to a less pronounced degree at Taggarts Ferry. The more sandy 

 character of the upper part of the Aquidneck series along the southeastern 

 side of the island may indicate approach to shore conditions in that direction. 



THICKNESS OF THE UPFEB OBEEK SHAIiES. 



The thickness of the upper green shales on the western side of the 

 Portsmouth syncline is probably at least 150 feet, and this is certainly the 

 smallest possible estimate for the thickness of the green shale series exposed 



