20 



sm J. W. DAWSON ON THE MESOZOIC FLORAS OP 



SUCCESSIVE FLORAS AND SUB-FLORAS OF THE CRETACEOUS IN CANADA. 



(In Descending Okder.) 



Periods. 



Transition 

 Eocene to 

 Cretaceous. 



Upper 



Cretaceous 



(Danian and 



Senonian.) 



Middle Creta- 

 ceous (Turo- 

 nian and Ce- 

 nomanian.) 



Lower Creta- 

 ceous (Neoco- 

 mian,&c.) 



Floras and Sub-floras. 



Upper Laramie or Porcupine Hill Series 



Middle Laramie or Willow Creek Series. 



Lower Laramie or St. Mary River Series 



Fox Hill Series 



Fort Pierre Series 



Belly River Series. (See note) . 



Coal Measures of Nanaimo, B.C., probably here. 



Dunvegan Series of Peace River. (See note). . . 



Mill Creek Series of Rocky Mountains 



Suskwa River and Queen Charlotte Island Series. 

 Intermediate Series of Rocky Mountains 



Kootanie Series of Rocky Mountains 



References. 



{Platanus beds of Souris River and Calgary. 

 Rejjort Geol. Survey of Canada for 1879, and 

 present memoir. 



( Lemna and Pistia beds of bad lands of 49tli 

 •j Parallel, Red Deer River etc., with Lignites. 

 I. Report 4ftth Parallel and this memoir. 



Marine. 



Marine. 



/ Sequoia and Brasenia beds of S. Saskatchewan, 

 1 Belly River, etc., with Lignites. This memoir. 



f Memoir of 1883. Many Dicotyledons, Palm.s, 

 \etc. 



/ Memoir of 1883. Many Dicotyledons, Cycads, 

 \etc. 



/ Dicotyledonous leaves, similar to Dakota Grou] 

 t of tlie U. S. This memoir. 



f Cycads, Pines, a few Dicotyledons. Report Geol- 

 \ Survey. This memoir. 



Cycads, Pines and Ferns. This memoir. 



Note.— Though the flora of the Belly River series very closely resembles that of the Lower Laramie, showing 

 that similar plants existed throughout the Senonian and Danian iie.riods in North America, yet it is to be antici- 

 pated that siieciflc differences will develop themselves in the progress of discovery. In the mean time it scarcely 

 seems possible to distinguish by fossil plants alone the Lower Laramie beds from those of Belly River, and if 

 these are really separated by 1,700 feet of marine strata, iis is now believed on stratigraphical grotmds, the flora 

 must have been remarkably iiersist«nt. The Dunvegan series of Peace River probably corresponds in time with 

 the marine Niobrara and Benton groups farther south and the Mill Creek with the Dakota group. 



VI. — Physical Conditions and Climate indicated by the Cretaceous Floras. 



In the Jurassic and earliest Cretaceous periods the prevalence, over the whole of the 

 Northern Hemisphere and for a loug time, of a monotonous assemblage of Gymnospermous 

 and Acrogenous plants, implies an vmiform and mild climate and facility for intercommuni- 

 cation in the north. Toward the end of the Jurassic and beginning of the Cretaceous, the 

 laud of the Northern Hemisphere was assuming greater dimensions, and the climate pro- 

 bably becoming a little less uniform. Before the close of the Lower Cretaceous periods 

 the dicotyledonous flora seems to have been introduced, under geographical conditions 

 which permitted a warm-temperate climate to extend as far north as G-reeuland. 



In the Ceuomanian, we find the Northern Hemisphere tenanted with dicotyledonous 

 trees closely allied to those of modern times, though still indicating a climate much warmer 

 than that which at present prevails. In this age, extensive but gradual submergence of 

 land is indicated by the prevalence of chalk and marine limestones over the surface of 



