CHAPTER I. 

 THE ELEMENTS OF A PALEOGEOGRAPHIC PROBLEM. 



A. THE NATURE OF THE PROBLEM. 



Adequate treatment of paleogeographic problems has been delayed by 

 the lack of a true appreciation of their nature. Much of the literature in 

 paleogeography is from the pens of workers primarily concerned with the 

 distribution of land, water, and life, and commonly inadequately prepared 

 to discuss the complex factors which make up the true geography of any 

 time or region. Of all the numerous proposed definitions of geography, the 

 most satisfactory regards it as a discussion of "the response of life to the 

 conditions surrounding it." 



Paleogeography is the geography of past time and far wider in its scope 

 than a mere record of the extent of a bed or formation or the distribution 

 of animals and plants in any period of time. It involves all the factors 

 which must be considered in a modern geographical study, except the 

 economic features applicable to human industry, and must take into account 

 every influence, organic or inorganic, which has had any bearing upon the 

 life of the period or formation. An investigator who concerns himself solely 

 with the distribution of life is considering the effect rather than the cause 

 and is far from viewing the problem in the broad sense in which it should 

 be taken up. 



Obviously, then, a paleogeographic problem involves not only the deter- 

 mination of the location and extent of any stratigraphic unit of the earth's 

 crust and its biota, but all the factors which have in any way determined 

 the character of the rock or the manner of its deposition and all the factors 

 which have in any wise influenced the location, movements, and develop- 

 ment of the fauna and flora. It is equally obvious that such a problem is 

 enormously complex and may not be solved by attack from any one side 

 or angle. The biologist must consider the petrographic, structural, and 

 physiographic features of the rocks so far as they will serve to make clear 

 the physical conditions under which life existed and developed, and the 

 physical geologist may not neglect the laws of biology or a study of the 

 effects of environment upon life. 



1 Clements (Scope and significance of paleo-ecology, Bull. Geological Society of America, 

 Vol. 29, pp. 369—374, 1918) has recently emphasized the necessity of considering and 

 interpreting the habitat as the causative source of developmental changes. His paper, 

 written largely from the botanical standpoint, stresses the need for the same method 

 of attack as is urged in this work. 



2 1 



