FACIES OF THE SHORE ZONE 651 



and well worn, are found in this beach. Other examples no doubt 

 occur in other sections of this coast and elsewhere. 



Boulder beds of Tertiary age are not uncommon. In the Mi- 

 ocenic of the X'ienna Basin, some of the best preserved pelecypod 

 and gastropod shells are found in a boulder bed with pebbles up to 

 six inches or more in diameter, and well rounded. The Cretacic 

 boulder beds of South Germany and of Sweden are other examples. 

 In the former well-worn boulders up to several feet in diameter 

 constitute the deposit, while among them abound fragments and en- 

 tire individuals of brachiopods, pelecypods and other organisms 

 often in a remarkable state of preservation. In the Dresden region 

 pothole-like hollows are found in the old porphyries with a depth 

 of 20 feet or more, and these are filled with a coarse boulder con- 

 glomerate of Cretacic age, the individual boulders often a foot or 

 more in diameter, and well worn. Among these boulders sponges, 

 oysters and other organisms occur in abundance. In Scania and 

 elsewhere an Upper Cretacic conglomerate of pebbles and boulders 

 worn or angular contains Belemnites and other fossils of that 

 period, many of them showing no wear. One of the most striking 

 examples of such a conglomerate is found on the present eastern 

 coast of Sutherland, North Scotland, near the village of Helms- 

 dale. The formation occurs as a coastal strip, largely eroded by the 

 present sea, and forming a series of low-lying skerries exposed at 

 low water. The age of the formation is Jurassic, but it is almost 

 wholly composed of large and small fragments of Caithness flags 

 (Lower Old Red sandstone), some of the fragments reaching the 

 astonishing length of 20 feet or more. The larger fragments lie in 

 irregular positions, their stratification planes dipping in all direc- 

 tions, and they resemble in every respect the fragments now found 

 at the foot of the cliffs of these flags on the exposed Caithness 

 coast. Among the fragments and firmly embedded in the con- 

 glomerate and breccia matrix are worn heads of coral (Isastrea), 

 shells, Belemnites and other Jurassic organisms. Many of the 

 smaller organisms have apparently escaped all wear. 



4. Sandy fades. 



Sand is by far the most typical material of the shore zone, on 

 lakes as well as on the seashore. To a large extent the sand con- 

 sists of quartz grains, since this is the least destructible constitu- 

 ent of rocks. In regions of purely calcareous sources of sand, as in 

 the Bermudas, and on many coral reef islands, the sand is largely or 



