6 PKOCEEDINGS OF SPRINGFIELD MEETING. 



The Trias 



The Trias occupies the broad valley of the Connecticut, beginning in Westfield, 

 near the state line, as a narrow remnant and widening as it crosses the Connecticut 

 line to above 20 miles. 



It consists of (1) very coarse conglomerate along its eastern border — the mount 

 Toby conglomerate ; (2) of a coarse arkose or feldspathic sandstone and conglom- 

 erate on the western border — the Sugarloaf arkose ; (3) of a rusty sandstone — the 

 Longmeadow brownstone — in its more central parts ; (4) while down the central 

 line of the valley a series of shales and calcareous beds marks the deepest portion 

 of the ancient bay. The deposition of these coarse sediments was interrupted by 

 the outflow of the great Deerlield and Holyoke trap-sheets, which were submarine 

 and which, filling up the deeper portion of the channel, have been covered by fine 

 calcareous mud. This mud has been intimately mingled with the scoracious upper 

 surface of the trap for 12 miles, and also underroUed, so that similar masses form 

 the base of the bed. 



After the deposition of sand had deeply covered the great trap-beds mentioned 

 above, another bed flowed out over the sea bottom, and immediately following 

 this came an explosive eruption at a point south of mount Holyoke, which spread 

 tuff over a broad area of sea bottom. This was followed by a long series of isolated 

 outbursts of trap along the old fissure by which the great flows had come up earlier, 

 which may have formed volcanoes on the surface, but which appear now as cores 

 cutting across all the other rocks. 



The character of the basin in which the beds were deposited, the succession of 

 the same and the subsequent mOnoclinal faulting and erosion were illustrated by 

 detailed maps and models. 



The Quaternary Deposits 



A detailed map of the surface geology was exhibited, the drumlins and other 

 forms of till being shown in detail, and attention was especially called to the map- 

 ping of the glacial lake and stream beds. 



The area is divided into three toi)Ograi)hic parts — the eastern and western plateaus 

 and the central valley of the Connecticut river. This valley runs north and south, 

 while the ice retreated north 35° west, with a lobe extending down the central 

 valley. This enabled the ice to free the eastern side valleys in their headwaters 

 fii-st, causing a series of lakes, which drained off east of the Connecticut river. 

 This was followed by the series of Connecticut lakes— the INlontague, the Hadley 

 and the Springfield lakes— occupying the broad valley bottom, and, finally, a series 

 of stream beds was formed ]jy the retreat of the ice across the western plateau and 

 up the preexistent valleys from their mouths to their sources. 



Attention was called to the distinction of filled and unfilled lakes, and to the 

 repulsion of tributaries across construction terraces. It was shown that the tribu- 

 taries run for long distances parallel to the main stream, because the terrace is made 

 up of many confluent islands, around the lower ends of which the tributary suc- 

 cessively finds its way. 



Attention was also directed to the great preponderance of ox-bows and bends on 

 the right-hand side of the Connecticut and its tributaries, where they cross the 

 fine sands and clays of the Champlain epoch — an effect to be referred to the rota- 

 tion of the earth. 



