454 B. K. EMERSON — ON THE TRIASSIC OF MASSACHUSETTS. 



the midst of the conglomerate and repeats all the conditions described above, 

 and was another of the unknown rocks of the conglomerates. This reinforced 

 the conclusions here advanced as to the current system and showed the local 

 origin of the conglomerate and the improbability of its glacial origin. The 

 outcrops form also beautiful sections of transition from the Triassic into the 

 disintegrated crystalline rocks in strong contrast to the usual sections, where 

 quartz conglomerates, concentrated from the wear of a large quantity of rock 

 and often transported a considerable distance, form distinctly unconformable 

 contacts. They indicate that the disintegration of the crystallines was so 

 deep and the transgression of the water so rapid that this area was not eroded 

 down to the firm rock. I think, from all the circumstances, that this erosion 

 was performed by submarine currents and not by strictly shore action. 



Further, if subjected to slight metamorphism, such contacts would be 

 wholly obliterated. Thus in several ways they throw light on the difficult 

 contacts among the altered rocks of the Berkshire hills. This furnishes an 

 illustration of the effects of secular disintegration conjoined with rapid trans- 

 gression, as discussed by Professor Pumpelly in another paper in this volume.* 



The conglomerate materials found about Mount Toby are carried down 

 the eastern side of the valley for several miles beyond where schists form 

 the border of the basin, and across the eastern area of the pegmatites ; but 

 these gradually supply their place, and the resulting arkose is carried down 

 the eastern side of the valley and, in the center of the state, blends with that 

 already described on the west. 



The Sandstone and Shale. — At Turner's Falls, and again in the southern 

 third of the state, the basin widens, and, as the coarse shoreward beds retain 

 their width, a central area of sandstones — the Longmeadow brownstone — 

 was accumulated in the quieter situation ; while in the southern area, which 

 is also the more extensive, the bay widened so greatly that in its middle 

 fine silts and marls gathered, forming the Chicopee shale. 



While the two first (shoreward) rocks, the arkose and the conglomerate, 

 are marked by coarse rippling and cross-bedding (directed northward on 

 the western side), the central rocks are filled with problematical tubular 

 markings (sand tubes, one-eighth inch to one-half inch in diameter and one 

 inch to eight inches long, which I have called fucoids, but which my paleo- 

 botanical friends hesitate to acknowledge as plant remains), " bird tracks," 

 mud cracks, rain drops, curdled drying surfaces, and every indication of 

 frequent immersion and emersion. 



Conditions of Deposition. 



I believe the region to have been a narrow bay, with tides of the Bay of 

 Fundy type (reinforced on the east by the prevalent strong westerly winds), 



* Pp. 209-224. 



