. Maryland geological survey. eesof the equator, while that from western Greenland is in latitude 70°North, and that from Spitzbergen is from latitude 78° North, and evenif the latter is latest Jurassic instead of earliest Cretaceous, it servesequally well to indicate that climatic conditions were much more uniformthan they are at the present time. It seems quite obvious from a consideration of the large-fronded fernsand cycads of the Potomac flora that they could not have withstood awinter as severe as the average winter of to-day in the latitude of Mary-land. The petrified woods show seasona
. Maryland geological survey. eesof the equator, while that from western Greenland is in latitude 70°North, and that from Spitzbergen is from latitude 78° North, and evenif the latter is latest Jurassic instead of earliest Cretaceous, it servesequally well to indicate that climatic conditions were much more uniformthan they are at the present time. It seems quite obvious from a consideration of the large-fronded fernsand cycads of the Potomac flora that they could not have withstood awinter as severe as the average winter of to-day in the latitude of Mary-land. The petrified woods show seasonal changes, but the width of theactive growth-ring is very wide, and that of restricted growth is narrowand more or less irregular, and is as readily explained by a dry season as 150 The Lowee Cretaceous Floras oe the World by a cold winter, nor are there any known deciduous forms/ While thedata are not conclusive it seems certain that the Potomac climate wasconsiderably warmer than that of to-day, with much less change from. Fig. 1.—Sketcli map of the world showing the approximate location ofoutcrops containing Lower Cretaceous Plants. Potomac Group (Patuxent, Arundel, Patapsco formations), Maryland-Virginia area. Glen Rose beds (Trinity Group), Texas area. Black Hills area (Lakota, Puson formations). Kootanie area, Montana, British Columbia. Lower Cretaceous, Queen Charlotte Islands. Shasta area Upper Knoxville and Horsetown beds). Mexico (Neocomian). Peru (Neocomian). Kome beds, Greenland. Spitzbergen (possibly of Jurassic age). Southern England (Wealden. Barremian, Aptian, Albian) and Belgium (Bernissartian). Germany (Wealden, Aptian). Portugal (Neocomian, Barremian, Aptian. Albian). Prance (Neocomian, Barremian, Aptian, Albian). Switzerland (Neocomian, Aptian) and Italy (scaly clays of Emilia). Austria Hungary (Barremian). Klin Sandstone (Barremian). Uitenhage series. Southwest China (Neocomian). Japan (Neocomian). * season to season, and with a very long growing period
Size: 1919px × 1302px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, booksubjectpaleont, bookyear1901
