PEAT 



511 



of salt-marsh grasses, rushes, and sedges. In some 

 of the coastal marshes, salt-marsh peat is underlain 

 by peat of fresh-water origin, indicating subsidence 

 of part of the coast. 



Built-up deposits consist of moss and heath, over- 

 lain by tamarack-spruce in the north and by gum- 

 cypress in parts of the Atlantic and Gulf coastal 

 regions. The ground water level, although it may 

 never rise above the surface, is progressively ele- 

 vated as the peat collects. Surface conditions are 

 little changed from year to year; hence, built-up 

 bogs are relatively homogeneous. 



When a basin is filled with peat to the level of the 

 surrounding country, it is mature, and if moisture 

 is sufficient, the build-up process begins ; the deposit 

 develops as if it had originated on a relatively level 

 land surface not covered with peat. The result is 

 a composite peat deposit which may accumulate to 

 a thickness of many feet above the former level of 

 the basin. Composite areas are recognized by marked 

 changes in the character of the peat where the 

 pondweeds, water lilies, and sedges were displaced 

 by moss and heath plants. 



As the formation of peat depends upon many 

 factors, the rate of its accumulation varies widely 

 from place to place and from year to year. If climate, 

 topography, and vegetation are favorable, peat forms 

 rapidly, as in a few sphagnum bogs along the coasts 

 of Maine and Alaska, but if one of these factors 

 becomes relatively unfavorable, the rate of accumu- 

 lation is retarded or brought to a stop, or destruction 

 of the deposit may set in. Most if not all peat de- 

 posits that formed during the Pleistocene were 

 erased by weathering or erosion, so that the present 

 deposits, all of Holocene age, may lie on truncated 

 remnants of older cycles of peat development. An 

 age of about 13,000-14,000 years is about the maxi- 

 mum for a commercial peat deposit. Unlike timber 

 stands, most peat deposits in the United States are 

 not renewable. 



The major peat deposits in the conterminous 

 United States occur (1) north of the 41st parallel 

 and east of the 97th meridian in all the New England 

 States, Illinois, Indiana, Iowa, Michigan, Minnesota, 

 New Jersey, New York, Ohio, Pennsylvania, and 

 Wisconsin; (2) in the Atlantic and Gulf coastal 

 regions; and (3) in the western mountains and 

 coastal areas including parts of Washington, Idaho, 

 Montana, Oregon, California, Wyoming, Utah, Colo- 

 rado, Arizona, and New Mexico. 



In the northeastern and north-central region, peat 

 has accumulated chiefly in former lakes and ponds 

 in glacial terrain. Built-up deposits of sphagnum 

 moss peat are largely restricted to the cool humid 



northern parts of the Midwest and New England. 



The Atlantic and Gulf coastal regions are charac- 

 terized by many salt- and fresh-water marshes and 

 swamps; the peat deposits occur principally in 

 valleys and lagoons on a gradually subsiding coastal 

 plain. This peat is made up mostly of salt-marsh 

 grasses and other salt-water plants. However, many 

 deposits also have an underlayer of peat formed 

 from fresh-water plants. This layer was deposited 

 before the basin was invaded by salt water. 



Peat deposits of the West (Jennings, 1966, p. 288 ; 

 Cameron, 1968; Huntting, 1966; Savage, 1964) are 

 in basins in glaciated mountains and plains, in tidal 

 plains, and in river plains. 



The cool moist climate and irregular terrain of 

 Alaska favor the formation of all types of deposits, 

 but especially the built-up sphagnum moss type. 

 Small pockets of peat occur in high volcanic uplands 

 in Hawaii. 



GEOLOGIC AND PHYSIOGRAPHIC FACTORS 

 THAT CONTROL QUALITY AND QUANTITY 



The minimum size of a peat deposit worth exploit- 

 ing in the United States differs from place to place. 

 In the glaciated areas of the North, West and 

 Northwest, and in broad coastal marshes elsewhere, 

 peat deposits now exploited are at least 10 acres in 

 areal extent and have at least a 5-foot thickness of 

 commercial-quality peat. Tonnage in peat deposits 

 is calculated on the basis of 200 tons of air-dried 

 peat per acre-foot. 



On the basis of these criteria, high-quality sphag- 

 num moss peat may be expected in large raised bogs 

 in New England, especially in Maine, and in north- 

 ern Minnesota. Most of the peat in the United States, 

 however, is reed-sedge, humus, and other types de- 

 posited largely in basins. The quality and quantity 

 of these deposits are dependent upon constant fac- 

 tors such as size, shape, and composition of the 

 depression containing the deposit, and upon varying 

 factors such as climate and surface- and ground- 

 water drainage. Cameron (1970a, b, c), working in 

 the glaciated areas of Pennsylvania and New York 

 and the unglaciated uplands of West Virginia, Mary- 

 land, and Pennsylvania, listed relationships of these 

 factors significant to resource potential of peat de- 

 posits as follows: 



1. Peat deposits enclosed within a bedrock basin 

 tend to have a higher percentage of fibers longer 

 than 0.15 mm than those deposits surrounded by 

 unconsolidated material. Relationship of peat qual- 

 ity to kind of material composing the surrounding 

 area and the walls of the depression in which accu- 

 mulation of peat took place involves several aspects, 



