No. 2. — The Squanium Tillite. 



By Robert "W. Sayles. 



Introduction. 



For many years the origin of the Roxbury conglomerate has been 

 a matter of debate. In 1869 Prof. X. S. Shaler stated his beHef in 

 the marine origin of this formation (Shaler, 1869, p. 172-177). Later 

 on, in his lectures he considered the conglomerate to be of glacial 

 origin. In some of his published statements the same idea may be 

 found (Shaler d al, 1899, p. -37-38, 57-59, 64-67). Prof. AY. O. 

 Crosby thought that the Roxbury conglomerate was of marine origin 

 (Crosby, 1890, p. 10-17). :Mr. W. W. Dodge believed in the glacial 

 origin of the Roxbury conglomerate (Dodge, 1875, p. 408-409). 

 Prof. J. B. Woodworth, although not publishing his views, has often 

 expressed his opinion that the conglomerate was of glacial origin. 

 Prof. George R. Mansfield did not indicate any decided view as to 

 the origin of the Roxbury conglomerate, but in his conclusions 

 (^Mansfield, 1906, p. 256-257) favored strongly the glacial idea. In 

 the last paragraph of this section of his paper he says : " The great 

 quantity of large pebbles of relatively fresh granite and the abun- 

 dance of felspathic material in the sandstones and in the matrices 

 of the conglomerates suggest that much material was furnished to 

 the streams of that time by glaciers of which no direct evidence now 

 exists." 



In ^-iew of the fact that tillite of Permian age has been found in 

 every continent except North America, the discovery of what appears 

 to be tillite in the Roxbury conglomerate is important. Glacial beds 

 of Huronian age have ahead v been found in Canada bv Prof. A. P. 

 Coleman, (Coleman, 1907) and Mr. J. A. Taff (1909), has found ice- 

 borne boulders in mid-Carboniferous shales in Oklahoma. 



On the 19th of December, 1909, I was gathering specimens of rock 

 with Dr. Laurence La Forge, just south of Boston, for the Harvard 

 Geological ^Museum. Dr. La Forge, who was at that time engaged in 

 making a geological survey of the Boston region for the L'nited States 

 Geological Survey, had come upon a curious exposure of the Roxbury 

 conglomerate at a locality in Hyde Park, across the street from the 

 Becker Milling Machinery Company. The rock appeared to have all 



