ENVIEONMENT OF THE TITANOTHEEES 



105 



nels ranged in width from a few hundred feet to half 

 a mile. Beside these stream channels there were 

 lagoons and areas of back water, some of them spread- 

 ing into shallow lakes but none into vast sheets of 

 fresh water. Savannas were interspersed with grass- 

 covered pampas traversed by wide, meandering rivers 

 that frequently changed their course. In these chan- 

 nels were deposited conglomerates and river sandstones, 

 marked by cross-bedding, as well as calcareous grits 

 In the shallow lagoons and back waters were deposited 

 the fine clays and layers of fuller's Qarth. The de- 

 posits of gypsum represent periods of evaporation. 

 In the lower part of the Titanotherium zone the de- 



it spread over the great area on which it has left its 

 traces by the deposition of its peculiar sediments. 

 * * * The basin-like character of this formation 

 is most admirably shown." In the same memoir, 

 Leidy (1869.1, p. 25) expressed some doubt as to the 

 lacustrine theory, observing: "It is a remarkable cir- 

 cumstance that among the large quantity of fossil 

 bones brought from the Mauvaises Terres and sub- 

 mitted to the examination of the author, certainly 

 amounting to several tons in weight, there was de- 

 tected no trace of remains of birds or fishes; and the 

 same may be said of reptiles, except one species of 

 turtle." 



Juan Ot/l^^ Ul 'lo he.iLi' ol UjJ.yiU-J 



Figure 72. — Type locality of the " Tiianoiheriuvi beds ol llaj deu, oii Bear Creek, S. Dak. 



Panoramic view, connecting at X. Upper section, looking southeastward, up Bear Creek; lower section, looking northwestward, down Bear Creek. Am. Mas. 



negatives 104722-104726. 



posits consist chiefly of fine flood-plain or overflow 

 sediments interspersed with river sandstones and 

 conglomerates, perhaps locally lacustrine, and occa- 

 sional layers of volcanic ash. 



This theory that the deposits of the western Great 

 Plains region are of flood-plain and fluviatile origin 

 has gradually replaced the older lacustrine theory that 

 they were laid down in great fresh-water lakes. The 

 lacustrine theory originated with Hayden, who, in his 

 geologic introduction to Leidy's memoir of 1869 

 (1869.1, p. 18), observes: "One of the most interesting 

 features in regard to this great fresh-water lake is the 

 evidence of its growth from a germ, as it were, until 

 101959^29— VOL 1 9 



The lake-basin theory was generally adopted by 

 geologists and paleontologists, reaching its apex in 

 King's development of the lake theory both for the 

 Plains and the mountain region. Johnson (1901.1), 

 Gilbert (1896.1), Haworth (1897.1), and especially 

 Davis (1900.1) reviewed the whole subject broadly in 

 a critical way, developing the theory of fluviatile and 

 flood-plain origin. Fraas (1901.1), Hatcher (1902.3), 

 and more recently Darton (1905.2) set forth strong 

 evidence for the theory of deposition in river channels, 

 flood plains, back waters, lagoons, and shallow lakes. 

 Among paleontologists Matthew (1899.2; 1901.1) 

 was the first to attack the lacustrine theory of the 



