GEOLOGY OF THE NARRAGANSETT BASIN. 



PART IIL-THE SOUTHWESTERN PORTION OP THE BASIN. 



By Aug. F. Foerste. 



CHAPTER I. 

 INTRODUCTION. 



DIFFICULTIES OF THE FIELD. 



The writer first studied tlie geology of the Narragansett Basin in the 

 summer of 1887. Thereafter he spent a part of each summer in this field 

 until 1890. His investigations during this time were confined almost 

 entirely to the region around North Attleboro, and some attention was 

 given to tracing the present margin of the Carboniferous basin. In the 

 course of the latter work about three months were spent on the southern 

 half of the Carboniferous basin. Some of these studies were recorded in 

 a thesis, "On the Igneous and Metamorphic Rocks of the Narragansett 

 Basin," 1890, deposited in the library of Harvard College. In the early 

 summei of 1890 a short stay at Newport convinced the writer that an order 

 of succession of the Carboniferous rocks could be made out, having the 

 following character: (1) At the base a series of shales, now known as the 

 Aquidneck shales ;. (2) above these, sandstone beds with some small pebbled 

 conglomerates, now known as the Sakonnet beds; (3) a very coarse peb- 

 bled conglomerate, then already known as the Purgatory conglomerate. 

 He then went to Swansea, around the margin of the great Dighton con- 

 glomerates, in order to see whether a similar succession could be made out 



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