Rocks in Southern Connecticut. 233 



is present in the rock. In some of the western ridges the con- 

 glomerate is mainly composed of trap fragments with a small 

 amount of coarse sandstone cement; the middle ridges contain 

 many bowlders of quartzite. mica and hornblende schist, gneiss, 

 and granite ; while the eastern ridges seem to have rather more 

 of the latter constituents than of trap. Bowlders of coarse sand- 

 stone also occur in this rock, and many of the fragments of trap 

 have coarse sandstone adhering firmly to them and forming a 

 part of the bowlders imbedded in the conglomerate. The pieces 

 of trap are either angular, subangular, or well rounded, compact 

 or amygdaloidal. and quite fresh or much decomposed. Many of 

 them contain long, vermiform cavities, either empty or filled with 



calcite But few of the trap bowlders, and those 



widely scattered, occur in the western and southern part of the 

 conglomerate area.'' 9 



After careful field study the present writer indorses 

 the foregoing description with the exception of one essen- 

 tial item — namely, the alleged occurrence of sandstone 

 bowlders and of sandstone adhering to trap fragments as 

 constituent parts of original bowlders. Obviously the 

 presence of such fragments w^ould be of great interest, 

 and of considerable importance in interpreting the history 

 of the deposits, inasmuch as the only sandstone in the 

 region is of Triassic age. Accordingly determination of 

 this point w^as made a special object of field study, and 

 the conclusion has been reached that the sandstone masses 

 mentioned in the description are probably parts of the 

 fan matrix, which is composed almost entirely of the 

 coarse arkose characteristic of the Triassic sediments in 

 the region. Between large angular bowlders the matrix 

 commonly has the form of isolated slabs or irregular 

 masses, which in weathered outcrops might be mistaken 

 for angular pieces originally deposited in the fan. It 

 appears that the original constituents w r ere derived only 

 from the crystalline formations and fissure veins in the 

 Eastern Highland and from masses of basalt. 



The valleys separating adjacent "bowdder ridges " are 

 peculiar in that they do not follow the strike of the beds 

 but cross it at a large angle. The parallelism of the 

 valleys, and the fact that some are not now occupied by 

 continuous stream courses, suggest a common and special 

 origin. Their trend corresponds closely to the apparent 



9 Hover, E. 0. : loe. cit., p. 375. 



