256 HISTORICAL GEOLOGY 



Economic Products 



Coal beds of moderate extent and value are known in the 

 Lower Cretaceous rocks of Alaska, British Columbia, Australia, 

 and Germany. 



Coal is extensively developed in the later Cretaceous of the 

 western interior region of the United States. It is estimated that 

 fully 100,000 square miles are underlain with chiefly lignitic and 

 bituminous coals as well as a little anthracite coal. Considerable 

 Cretaceous coal also occurs in Australia and New Zealand. 



The greensands (glauconitic) of the Atlantic Coastal Plain, 

 especially in New Jersey and Virginia, were formerly extensively 

 used as land fertilizers on account of their phosphoric acid content. 



A heavy production of petroleum has been obtained from the 

 Cretaceous strata of Texas, particularly in the vicinity of Beau- 

 mont. Both oil and gas are obtained from the Cretaceous in 

 Louisiana and Wyoming. 



Cretaceous limestones are quarried in Kansas, Nebraska, and 

 Iowa for building stone. 



The most important sulphur deposits in the United States occur 

 in rocks of Cretaceous age in Louisiana. 



The vast supply of underground water obtained from the Cre- 

 taceous (Dakota) sandstone in the Great Plains region is worthy 

 of special mention. Much artesian water is also derived from 

 Cretaceous beds in the Atlantic and Gulf Coastal Plain. In the 

 regions just mentioned the water is held under pressure in porous 

 sandstone by overlying impervious clay or shale. 



Life of the Cretaceous 



Plants. — Early in the period the plants were very much like 

 those of the preceding Mesozoic periods, the dominant types still 

 having been Ferns, Equisetce, Cycads, and Conifers. 



Among the Gymnosperms, which were distinctly subordinate 

 and a good deal like those of the present day, a feature of special 

 interest was a considerable development of the genus Sequoia 

 which is still represented by the so-called "Big Trees" and giant 

 Redwoods of California. 



Before the Cretaceous, Angiosperms are not definitely known 

 to have existed, but in North America there can be no possible 



