126 PRINCIPLES OF STRATIGRAPHY 



porary lakes. Examples of these are Lake Agassiz (LTpham-40) 

 on the Minnesota-Canadian border; Lake Passaic (Salisbury-33) 

 of eastern New Jersey; Lakes Boiive (Grabaii-i6), Charles (Clapp- 

 3), Nashua (Crosby-4), etc., in eastern Massachusetts; and Lake 

 Shaler (Wilson-4r)) in the Cape Cod region; and the glacial 

 Genesee and other lakes of New York (Fairchild-13). Additional 

 examples are found in Scotland, Scandinavia, the north of Ger- 

 many, etc. Ice-barrier lakes are as a rule very short-lived. 



5. Organic barriers. The growth of vegetal material at the 

 mouth of a river may serve directly to choke drainage and so 

 transform the district into a lake, and indirectly it will serve this 

 purpose by inviting deposition of fine detritus where the current is 

 checked. The growth of coral reefs may also form a barrier across 

 an indentation of the shore, which may then be transformed into 

 a lake. According to Davis (7), the lakes of the Everglades in 

 southern Florida are examples of this type. 



6. Detrital barrier basins. These are perhaps the most com- 

 mon barrier basins, and to them by far the largest part of the 

 barrier lakes now existing belong. 



(a) Barrier beach basins. A barrier beach may cut off a 

 valley or embayment from the ocean or from other lakes and so 

 convert it into a separate lake basin. So long as the free connec- 

 tion with the parent body is maintained, so that water flows into 

 the new basin from the sea or lake to which it belongs, it cannot 

 be considered distinct, but only as an arm of the parent body. In 

 some cases the opening remaining is so small as practically to pro- 

 hibit the entrance of the water from the parent body. This seems 

 to be largely the case in the Frische Haff and the Kurische Haff 

 on the Prussian coast (2); and to a large extent also in the 

 Black Sea. Occasionally the cut-off from the sea becomes brackish 

 or fresh, as in the case of some ponds along the ]\Iassachusetts 

 coast, and those of the coast of Pomerania, while in others exces- 

 sive evaporation may cause the extinction of the lake, unless the 

 barrier is broken, as in the salt lakes of Bessarabia on the north- 

 west coast of the Black Sea. 



(b) Fan delta basins. These are formed by the damming of a 

 valley by the dry delta or fan of a tributary. Lake Pangkong in 

 the Himalayas, back of Kashmir, represents this type. Its drain- 

 age is now entirely by seepage, the water being slightly brackish. 

 Another example is Tulare Lake, a shallow sheet of water with 

 indefinite marshy shores, situated along the San Joaquin River in 

 the Valley of California. The upper tributaries of this stream have 

 been ponded back by the alluvial fan of King River, which rises 



