VOLUME LXXII NUMBER 2 
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DOTANIC AL GAZE Te 
* AUGUST 1921 
PEAT DEPOSITS AND THEIR EVIDENCE OF 
CLIMATIC CHANGES 
ALFRED P. DACHNOWSKI 
(WITH TWELVE FIGURES) 
The time in which the various peat deposits of the United States 
were formed can be determined only from a joint consideration of 
glacial geology, climate, and plant remains. These reflect the 
relations between a deposit of peat materials and its environment. 
To attempt a correlation of this kind on a chronological basis, 
however, has many difficulties, which investigators in the respective 
sciences appreciate. 
The essential nature of stratigraphic differences in peat deposits 
_is indicated by the nature of the plant remains and the order in 
which layers of peat material lie upon one another, that is, by the 
sequence of the vegetation units which at one time formed layers 
of plant remains in the deposit. As to the tectonic order of the 
layers or series of layers of material composing a peat deposit, 
little need be said at this time. From the standpoint of stratig- 
raphy the condition of the initial area in which a pioneer plant 
population established itself is the critical factor of greatest im- 
portance, so far as the beginning of the course of development is 
concerned. The sequence of the development may become changed 
anywhere in the course, either by changes in environmental factors 
or in plant population. These changes are all recorded within the 
deposit. In the vast majority of peat deposits the beginning of 
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