PALEOBIOGEOGRAPHY OF THE MARINE REALM 185 



warm as those of the present temperate zone." From the distri- 

 butional data it would have been pardonable to call them temperate 

 without qualification. 



General Cretaceous (late Mesozoic) paleoclimatology runs in 

 much the same vein as that of the Late Jurassic. The very wide- 

 spread Cretaceous deposits and rich shelly faunas, however, ofTer 

 enticing prospects of doing something more refined about the 

 paleobiogeography. In the hope of spurring more interest in this, 

 I have tried reconstructing a current system for the well-docu- 

 mented early Late Cretaceous seaway through North America 

 (Fig. 10), connecting with the Tethyan seaway at the south. 



The evidence of the ammonites and inoceramids from Greenland 

 and northern Alaska (Imlay and Reeside, 1954, pp. 226, 242, and 

 references there cited) and of the rich Cretaceous flora of west 

 Greenland (Dubois, 1895, p. 13) confirms the warm-temperate 

 nature of the Turonian climate of present Arctic regions. Hence 

 (assuming no latitudinal change, and for reasons given) we may 

 eliminate the polar easterly winds as an effective force and intro- 

 duce a preponderant eastward current drift at high latitudes, 

 driven by the west winds of a subpolar whirl. Such a current, 

 presumably, would enter the northern end of the Rocky Mountain 

 geosyncline, turn right under the influence of Coriolis force, and 

 execute a clockwise gyral. Opposing this at the south, would be 

 another clockwise gyral introduced by the Tethyan trade wind 

 drift from the southeast in a similar way. Of course, numerous 

 local irregularities would develop, but the two principal gyrals 

 should impinge obliquely about at the present international 

 boundary, and broadly separate different faunal provinces. The 

 fact that the Turonian faunas of northern Alaska have Atlantic 

 aspects (W. A. Cobban, oral communication) Is not at odds with 

 this. It is to be expected that entralnment of southern waters along 

 the western side of the northern gyral, or even a narrow long-shore 

 current from the south would filter some southern elements 

 northward, and that the reverse might happen along the eastern 

 side. There should, moreover, be a general coincidence of pelagic 

 and shallow benthonic differences with the two suggested gyrals, 



