STRUCTURAL TERMINOLOGY 



far greater, even continental arching. Schuchert generally recognized 

 geanticlines and geosynclines as "complementary structures," but called 

 the land that divided the Cordilleran geosyncline during Mesozoic time 

 into an eastern geosyncline and a western, the greatest of North American 

 geanticlines. 



Although Schuchert attempted to clarify Dana's most confused defini- 

 tion, he introduced contradictory thoughts, and therefore did not clarify 

 the meaning of the term. Others have confused the meaning still more. 

 According to Willis ( 1934 ) , "a geanticline is a very large elevation of the 

 earth's surface. The rocks of the geanticline may not be folded — may not 

 even be stratified — and the anticlinal significance is lost." Lahee ( 1941 ) 

 states that a "geanticline is a very extensive uplift, generally anticlinal in 

 nature (also called a regional anticline)." He gives as examples the "Ar- 

 buckle Mountain Uplift and the Central Mineral Region of Texas," which 

 are two greatly different kinds of tectonic elements. According to Nevin 

 ( 1942 ) a geanticline is a "great upwarp . . . whose dimensions are meas- 

 ured in hundreds of miles. . . . The Ozark Mountains and the Arbuckle 

 Uplift are true geanticlines." These, again, are dissimilar structures. Bill- 

 ings (1942) defines a geanticline as "the counterpart of a geosyncline, (it) 

 is an area from which the sediments are derived. The geanticline that lay 

 southeast of the Appalachian geosyncline is known as Appalachia." In 

 the Dictionary of Geologic Terms (Rice, 1940) a geanticline is "a 

 large, broad, and usually very gentle anticline, commonly many miles in 

 width." 



Most of these definitions are widely divergent, and the examples are 

 structures of contrasting size, composition, history, and relation to the 

 central stable interior of the continent. Some of the definitions are synony- 

 mous with terms already defined, such as arch, dome, and landmass. 



The confusion in American literature is paralleled by the European. 

 Brouwer (1925) of Holland says that a geanticline is a major uplift of 

 island arc size, complementary to the geosyncline. Collet ( 1927 ) , follow- 

 ing Argand (1916), defines a geanticline as an anticlinal ridge that ap- 

 pears on the bottom of a geosyncline and expresses itself as a land barrier 

 between the seas of the geosyncline. It is at first a long, narrow anticline 

 of considerable size and later evolves into a great nappe. Whether the de- 



velopment of a nappe is necessary to demonstrate a true geanticline in not 

 stated or implied. Most Alpine geologists, it is my impression, follow tin- 

 usage of Collet. 



King (1937) exemplifies the Alpine usage in his treatise of die evolu- 

 tion of the Marathon system. A structure in west-central Nevada tint 

 rose out of the Paleozoic Cordilleran geosyncline is i ailed a geantu line In 

 Nolan (1928). I have decided to follow the specific usage of Collet, King, 

 and Nolan and will denote a geanticline as a large, elongate, anticlinal 

 fold that develops in the sediments of a geosyncline. It is not a 'geanticline 

 if an uplift in the foreland or shelf area. Two or more geanticlines ma) 

 develop at the same time or following each other in a great geos\ ncline. 

 After the early anticlinal uplift, the great fold usually becomes a complex 

 anticlinorium, several imbricate thrust sheets, or a nappe. It may be 

 largely submarine, and suffer little erosion. 



Range 



The synonymous use of the terms highland, landmass, mountains, up- 

 lift, arch, and geanticline, all to describe uplifts of the Ancestral Rockies 

 and Wichita systems with fairly similar size and shape, poses a difficult 

 problem, especially because of the provincial nature of the usage. It is so 

 commonplace to say Electra arch and Uncompahgre highland that a 

 change of name of one or both is not easily accepted by all. For the sake 

 of the student who is trying to get an understanding of the rather com- 

 plex, regional, structural relations of the continent, uniformity of meaning 

 is desirable. Many geologists long since out of school recognize the need. 

 It is a matter of clear composition. 



Nearly all the structural features to which the names highland, land- 

 mass, uplift, arch, and geanticline in the Ancestral Rockies and Wichita 

 systems have been attached are the size of a range like the Bighorn, the 

 Uinta, or the Selkirk ranges. It seems, therefore, that the word range 

 would be very expressive of the sharp and linear, now buried or nearly 

 buried, late Paleozoic uplifts of the interior part of the United States. 



Geographers have agreed on the usage of range and mountain svstem 

 as follows: A range is a mountain mass within limits the size of the Big- 

 horns or the Selkirks, and a number of these ranges with certain unifying 



