72 



CAPE COD GEOLOGY 



CLASSIFICATION OF THE GLACIAL DEPOSITS 



The chief object of a classification of the moraines of Pleistocene glaciers is 

 to assist in recognizing their mode of origin, whether through the agency of ice 

 or water, and, by an imaginative restoration of the ice sheet or its melting rem- 

 nants, to determine the position of particular deposits relative to the ice. A 

 classification proposed by me in 1890 is here presented, expanded to include the 

 subvarieties of moraine not specifically named in my original paper. In this 

 classification, mode of origin is the prime factor. Deposition either within a field 

 occupied by a glacier or just beyond its limits is a secondary factor. Position with 

 reference to the ice, whether on its surface, within it, under it or at its side, takes 

 a tertiary place in the classification. 



Classification of glacial deposits {moraines) 





Intraglacial 

 moraine 



Superglacial 



Lateral, medial, marginal moraine of cliff 

 debris (unstriated debris). Rock tables 



Ablation deposits brought up from within 

 the ice 



Crevasse (vein) moraine 



Wind-blown sand 



Ice-laid 

 moraine 



Englacial 



Dirt bands; crevasse (vein) moraine. 

 Boulders; clay pockets. Drift worked in 

 from above or up from below 





Subglacial 



Ground moraine, till plains; submarginal 

 moraines; drumlins; crag tails. Shoved 

 blocks. Dislocated terranes; e.g., Gay 

 Head cliffs 



Extraglacial 

 (till) 



Extraglacial 

 moraine 



Ice bound; in con- 

 tact with ice or 

 once supported 

 by it 



Frontal, terminal, dump moraines at edge 

 of ice, resting on unglaciated terrane; 

 also lobate and interlobate moraines. 

 Boulder belts 



Ice free; beyond 

 and below the 

 edge of the ice- 

 sheet 



Drop moraine on slopes. Bergdrift in seas 

 and lakes. Boulders rolled beyond 

 ice front 





Intraglacial 

 gravel, sand and 

 clay 



Superglacial 



Stream gravel and sand 

 Some kames ? lowered to base 

 Some eskers ? 





Englacial 



Some kames and eskers doubtfully of this 

 origin. "Englacial drift of Upham" 



Water-laid 

 glacial 



Subglacial 



Eskers; kames (in part); various stream 

 gravels. Boulders (in part) 



drift 



Extraglacial 

 gravel, sand and 

 clay 



Ice bound 



Outwash plains; sand plains; esker fans; 

 kames; pitted plains. Lateral terraces; 

 kame terraces 





Ice free 



Some sand plains; valley trains silt plains; 

 proglacial clays. Deposits reworked by 

 rivers, waves and currents 



The ice contact is typically shown by the sloping sides of eskers (long ridges 

 of water-laid drift), possibly by the steep sides of kames (mounds of gravel and 



