30 Nezv York State Museum 



fault breccias (see page 33). Wind-blown sands 

 (eolian sands) and river and beach sands have rounded 

 grains due to long handling. Material transported by 

 glaciers and later deposited by running water (fluvio- 

 glacial deposits) is apt to show subangular sands and 

 pebbles. Pebbles and boulders carried by ice show 

 faces or facets due to rubbing against bedrock as they 

 are carried along. The pebbles may shift their posi- 

 tion in the ice and then more than one facet is pres- 

 ent. These faces also show scratches. Sometimes 

 pebbles carried by ice show concave fracture scars. 

 Pebbles in conglomerates sometimes show scars and 

 indentations due to solution and pressure when they 

 are in contact under compression. Polished faceted 

 pebbles indicate wind action and are polished by wind- 

 blowm sand or dust. If there is one polished face the 

 pebble is known as einkanter (one-edge) ; three faces 

 give it the name dreikanier (three-edge). Pebbles and 

 boulders become rounded not only through mechanical 

 action in being rolled about, but also through concen- 

 tric weathering. The agents of disintegration work 

 in along the corners, edges and surfaces of blocks or 

 slabs and as the corners and edges wear faster than 

 the surfaces subangular to rounded boulders or peb- 

 bles of disintegration are formed. Such boulders and 

 pebbles are weathered on the outside and have a rough 

 surface in contrast to those that are rounded through 

 mechanical action. The weathered portion of such 

 boulders often peels off as a shell. 



The rocks derived ffom the consolidation of these 

 elastics, however accumulated, may be roughly divided 

 into three groups according to the character of the con- 

 stituents. These are the rubble rocks or conglomer- 



