400 R. S. Lull — Life of the Connecticut Trias. 



Connecticut and Massachusetts. The shores of the bay were 

 the west scarp of the Worcester County plateau on the east and 

 the east scarp of the Green Mountain plateau on the west, and 

 extending from near Brattleboro, Vermont, to New Haven, 

 Connecticut. The sea waters rose to a considerable height 

 above the present level of the bordering plateaus and spread 

 sediments brought in from these elevated regions on either 

 side of the bay. The shoreward sediments on the east are 

 represented by the Mount Toby conglomerates, and the Sugar- 

 loaf arkose is the synchronous deposit formed along the 

 western shore. The Longmeadow sandstone was deposited in 

 the shallower and quieter off-shore area, and in the central zone 

 of the latter area, where the basin was widest, the still finer 

 Chicopee shale was laid down. All these deposits are partly 

 contemporaneous sediments, differing as the strength of the 

 current and the character of the shore rocks affected them. 

 Strong tides, like those of the Bay of Fundy, seem to have swept 

 up the west side of the bay, carrying the material of the gran- 

 itic shore rocks far north, to rest against a shore made of dark 

 schists, and the return currents ran along the east shore, carry- 

 ing the eastern shorewash south, while quieter waters and shift- 

 ing currents spread the sediments in the central area. 



" The accumulation of sediments was interrupted by an 

 eruption of lava through a fissure in the earth's crust, which 

 opened along the bottom of the basin. The lava flowed east 

 and west along the bay, as tar oozes and spreads from a crack, 

 and solidified in a sheet which may have been 2 or 3 miles wide 

 and about 400 feet thick in its central part. This is the main 

 sheet or Holyoke diabase. This sheet was soon covered with 

 sand layers, but its thickness was such that it shallowed the 

 waters to near tide level, and thus occasioned extensive mud flats. 

 This was an area suitable for the formation and preservation 

 of unique records of the life of the time. The curiously shaped 

 and often huge reptiles of that age wandered over the mud 

 exposed at low tide, and their footprints, being covered by the 

 deposit of the next flood tide, constitute the so-called ' bird 

 tracks' which have been found in such great numbers and 

 perfection. 



" The sands had reached a considerable thickness over the 

 first trap bed when a second outflow of the trap followed, rep- 

 resented by the posterior bed or Hampden diabase. Immedi- 

 ately after the outflow of this sheet an explosive eruption took 

 place, and blocks of diabase and pulverized lava were spread by 

 the waters over a broad area, forming the Granby tuff bed. A 

 third period of volcanic activity followed, during which a line 

 of small volcanoes broke out along the old fissure beneath the 

 bay. The area was next the scene of dislocations or faults, by 



