CONTENTS. 



PAGE 



Introduction ^ 



Chapter I. The Elements of a Paleogeographic Problem i 



A. The nature of the problem 2 



B. Outline of points to be considered in any paleogeographic problem 2 



I. Stratigraphic limits of the unit to be considered 2 



(a) Isolation of the unit by the nature of the deposits 3 



Marine deposits 3 



Coastal deposits 3 



Shallow-water deposits 5 



Deep-water and abyssal deposits 5 



Cut-off arms of the sea " 



Non-marine saline deposits " 



Brackish-water deposits 7 



Fresh-water deposits ° 



Subaerial deposits (fluviatile, delta, and aeolian) 8 



Glacial deposits " 



Metamorphosed sediments '2 



Igneous rocks '^ 



(b) Isolation of unit by limiting planes 12 



II. Geographical limits of the unit '4 



(a) Mapping of the limits '4 



(b) Location of source of material '4 



(c) Seaward limits of the unit '5 



(d) Lateral changes in the beds '6 



(e) Positive and negative areas I" 



III. Interpretation of the adjacent lands '7 



(a) Direct contact of observed surfaces of degradation 17 



(6) Physical character of deposits '7 



(c) Mineral content '° 



(d) Fossil content '9 



IV. The fossil content of the unit '9 



(a) The fauna of the unit '9 



{b) Origin of the fauna 2° 



Aquatic invertebrate fauna 20 



Terrestrial invertebrate fauna 23 



Terrestrial vertebrate fauna 23 



(c) Character of the fauna ^4 



(d) Phylogenetic relations of the fauna 24 



(e) Peculiarities of the fauna ^5 



(/) Radiation and depression of life 26 



(g) The interrelations of the fauna 27 



(h) Faunal elements as time markers 29 



(t) The flora of the unit 29 



V. Correlation of unit with other beds 32 



VI. Climatology of the past 33 



VII. Distribution of the fauna and flora 34 



(a) Provincial or cosmopolitan 34 



(b) Distribution dependent upon the character of the biota 34 



(c) Distribution dependent on the inorganic environment 35 



(d) Migration 36 



(e) Autochthony 37 



(/) Accidental introduction 37 



(g) Extinction of a fauna or flora 3° 



(h) Survivals and precipitate development 3° 



(i) Control of distribution 39 



(J) Environment 40 



VIII. Checks on the geologist 42 



IX. Checks on the biologist 43 



(a) Bridges and barriers 43 



iii 



