CORRELATION AND PALEOGEOGRAPHY 



233 



elusive results, is that which bases generalizations on plants or animals, or 

 earth conditions singly, instead of grouping and synthesizing all possible 

 evidence from all three sources. Plants, invertebrates, and vertebrates 

 each give their own peculiar testimony. A synthesis of this broad nature 



Fort Union molluscs, plants 



'-^■■■— — -^-^-W — Fort Union plants 



Mammal Quarry 



MAMMALS 



PantoJambda 

 C/aenodon 



Piilodus 



Fort Union plants 

 -Ceratops Beds'^molluscs 



Fort Union plants 



Fort Union plants 



C/aenodon 

 Mioc/aenus 



Ceratops Beds molluscs DINOSAURS 



Triceratops 

 Trachodon 



— r^ZlT7:"iIl^.":il -rr-nZZ tt^^^ ^"H JK— Livingston'''plants 



Marine and brackish 

 in vertebra tes 



Ft. Pierre 

 invertebrate 

 fauna 



Figure 1. — Section from Hell Creek, Montana 

 Transition from Summit of Cretaceous to Basal Eocene. Modified after Brown 

 Upper : Pantolambda Zone, Fort Union 

 Lower : Triceratops Zone, "Laramie" 



is what is demanded both for correlation and for paleogeographic conclu- 

 sions, which depend so largely on synthetic correlation. 



Granting that the above represent the modern canons for correlation 

 and paleogeography, in the brief time allotted our discussion must be con- 

 fined to the progress of the past ten years, based chiefly on the mammals 



