724 A CENTURY OF PROGRESS IN THE NATURAL SCIENCES 



Upper Cretaceous succession of England with that of northern France. Coquand 

 carried on detailed investigations in southern France, where the rocks show 

 marked facies variations, and tried to correlate the divisions with those estab- 

 lished by Hebert in the north of France. The regression of the seas late in Juras- 

 sic time left extensive areas of Europe just barely above sea level and upon this 

 surface in southern England was deposited the Wealden formation, with its 

 rich vertebrate fauna. 



The east-west Vindelican land mass which divided Europe into two east-west 

 basins became flooded as Cretaceous time progressed, producing a succession of 

 overlapping beds from southern to northern France so that by ]\Iiddle Cretaceous 

 time the sea transgressed widely over Europe. Farther east in the Himalaya 

 region of Tethys Basin an extensive series of Cretaceous sediments contained an 

 eastern facies of the Alpine faunas, as described by Victor Uhlig and Stoliczka. 



Extensive outcrops of folded and faulted Cretaceous rocks, which lie in the 

 great downfold extending w^estward through northern Venezuela and thence 

 southward in the Andean trough from Colombia into southern Argentina and 

 Chili, have been described by the geologists connected with the national surveys 

 of those countries and by independent scientific investigators. The faunas of 

 the successive stages show close relationships to those of Europe. The Creta- 

 ceous faunas of central Argentina have many affinities with those of the Uiten- 

 hage formation of South Africa. Among the more important contributors to 

 these problems are Behrendsen, Burekhardt, Groeber, Windhausen, Gerth, Ort- 

 mann, Krantz, Stanton, Leanza, and Feruglio. 



The Federal and state survey reports in north America during the second 

 half of the past century present a fairly clear picture of the areal distribution 

 of Cretaceous rocks in the Atlantic and Gulf Coastal Plains, the Rocky ]\Ioun- 

 tain region, and the Pacific Coast. During the past fifty years detailed studies 

 of particular areas have been undertaken by the geologic staffs of oil companies 

 and a part of this information has been published by the American Association 

 of Petroleum Geologists, the Geological Society of America, and other similar 

 organizations. 



Late in the Jurassic and axial uplift west of the Rocky Mountains was ac- 

 companied by a broad north and south downwarp extending from northern 

 Canada to Mexico and within it were deposited a nearly complete succession of 

 marine Middle and Upper Cretaceous sediments. These formations and their 

 faunas have been described in the numerous reports and geologic folios of the 

 U. S. Geological Survey and other state and ]H-ivate organizations. For many 

 years there was uncertainty concerning the boundary between the uppermost 

 Cretaceous and basal Tertiary, a time of withdrawal of marine seas from the 

 trough and of the sharp tectonic disturbances which accompanied the Laramide 

 Revolution. For some time there were controversies whether the top of the Cre- 

 taceous should be placed at the upper level of the Laramie or Fort Union beds. 

 The land plants in the Laramie at first were thought to be related to the Tertiary 

 but the dinosaurs were distinctly Cretaceous and are not known in the Fort 

 Union beds. Investigations by Earling Dorf in 1940 revealed that the floras of 

 the two formations were distinct, and the plane of demarcation now is placed at 

 the top of the Laramie. 



The studies made bv the Geological Survey of California from 1860 to 1869 



