Geological Papers. 109 



glacial marine deltas. 



1. Deltas Deposited in Front of the Ice in the Open 

 Sea. — This class spread outward in round or irregular fan 

 shape when deposited over broad and rather level plains where 

 they were free to expand in all directions; but in narrow 

 valleys their slopes were necessarily determined in part by 

 adjacent hills. They conspicuously show the characteristic 

 horizontal transition of sediments, from coarse at the north 

 to finer material toward the south, that is, away from the 

 mouth of the glacial river. The delta indications are unmis- 

 takable. 



2. Ice-bordered or Narrow Marine Deltas. — These are 

 usually much longer from north to south than from east to 

 west, having but little of the fan shape. At their southern 

 ends they pass by degrees into clays having the same level, 

 like the delta plains above described. They are found in val- 

 leys or level regions much broader than they are, where there 

 is no topographical reason why a delta, if deposited in the 

 open sea, should not have spread outward in fan shape. Evi- 

 dently the glacial rivers flowed into channels which were open 

 toward the sea, but at the sides were bordered by ice which 

 covered the rest of the valleys and prevented the delta from 

 spreading out. 



That these deltas are marine is attested by the marine 

 fossils. 



Fringing Lake Sediments. — This class embraces deposits 

 of suspended material brought out from the ice into the bor- 

 dering lakes by glacial streams and spread over their bottoms. 

 It is a somewhat stratified material of the clayey type, some- 

 times bearing lacustrine fossils. It is often commingled with 

 stony material dropped by floating ice from the edge of the 

 glacier, but not in noticeable quantities. It is also always 

 commingled with wash from the adjacent land not covered by 

 ice. 



Bordering Sea Sediment. — This class differs from the pre- 

 ceding in the fact that the waters were not imponded in ice. 

 and in the fact that the deposits are commingled with oceanic 

 sediments and marine fossils, and impregnated with saline 

 waters, which may or may not have been wholly removed sub- 

 sequently. 



Local Formations Produced by Floating Ice. — These de- 



