MAPS AND SECTIONS. 



The uncertainty whicli accompanies many of the views regarding the 

 geological structure of the lower Narragansett Basin is largely due to the 

 fact that the greater part of the area is covered by glacial drift and .and 

 plains or concealed by the water of the many arms of the bay. This is 

 well brought out by the map, which indicates the position of almost all 

 outcrops of any value for geological purposes, Moreover, the outcrops are 

 frequently scanty or absent at the very horizons where it is exceedingly 

 desirable to hiive them in order to determine the question of the succession 

 and the equivalence of the rocks. It was necessary on this account to 

 leave some areas without other indication than the color for the general 

 Carboniferous. The boundaries of some of the divisions recognized may 

 eventually have to be somewhat shifted, as sewers, ditches, and cellars 

 expose rocks now hidden from sight. - 



Moreover, in order to present anything in the nature of a section 

 across strata, it was necessary to generalize the interpretation of outcrops. 

 A reference to the map will ustially indicate the extent to which this has 

 been done. 



There is perhaps little doubt that both the Kingstown sandstones and 

 the Aquidneck shales have been considerably folded. This must certainly 

 be true of the Kingstown sandstones between Wickford and Potowomut 

 Neck, and also of the Aquidneck shales from Coddington Cove to Black 

 Point But unfortunately we have so far no indications as to the precise 

 locations of any of the synclines or anticlines in this system of folding. It 

 therefore seemed impossible to introduce folds into the section, offering 

 possibly a source of even greater error than if these indications were 

 omitted, but the general necessity of assuming folding was brought out 

 clearly in the text Actual exposures are shown in the sections by solid 

 lines, while inferences as to the continuation of these exposures beneath 

 the soil and the probable attitude of strata where there are no exposures 

 are indicated by dotted lines. 



394 



