244 c - w - TOMLINSON 



the Arbuckle-Wichita region. Near the border of the present 

 Arbuckle and Wichita mountains, limestone conglomerate and 

 conglomerate of crystalline rocks dovetail into Red Beds sediments 

 of finer grain. The limestone undoubtedly was derived from earlier 

 Paleozoic formations, and the crystalline fragments from more 

 ancient rocks, both of which are known to have been exposed in the 

 uplifted region just named. Increasing thickness of sediments 

 toward the mountains testifies to the same relation. To what 

 distance sediments from this isolated highland may have been 

 distributed is largely a matter of conjecture. The entire Red 

 Beds series thins northward from this area to the northern limit 

 of their outcrops in Nebraska, and in the same direction clastic 

 sediments give place in part to limestones: both of which facts 

 signify increasing distance from the source of terrigenous material . 

 The small outlier of Red Beds in central Iowa, which probably 

 is to be correlated with the Cimarron series of Kansas, 1 is composed 

 chiefly of red shale and gypsum, likewise indicating relatively 

 clear-water conditions. It would be an unwarranted assumption, 

 however, to assume that the Kansas and Iowa Red Beds were 

 derived wholly from the Arbuckle highlands. The greater areas 

 of upland which probably existed in the region surrounding and 

 including the pre-Cambrian areas of Minnesota and Wisconsin 

 may have been important sources of material, as may also the 

 ancient Appalachian continent of the East; but it may safely be 

 said that their influence is not exhibited in the strata now available 

 for study, as the influence of the Arbuckle highland so clearly is. 

 Similar criteria may be applied to the great conglomerates of 

 the Fountain and Wyoming formations of the Front Range, and 

 to those of central and southwestern Colorado. The conglomerates 

 of the Front Range Red Beds and of the Maroon formation of the 

 Anthracite, Crested Butte, and Tenmile districts are made up 

 chiefly of fragments from pre-Cambrian crystallines, 2 which still 



1 Cf. F. A. Wilder, "The Age and Origin of the Gypsum of Central Iowa," Jour. 

 Gcol., XI (1903), 723-48. 



3 See Whitman Cross, Pikes Peak Folio (No. 7), Gcol. Atlas of the U.S., U.S. Geol. 

 Survey, 1894; G. K. Gilbert, Pueblo Folio (No. 36), 1897; and G. H. Eldridge, 

 " Description of the Sedimentary Formations," Anthracite-Crested Butte Folio (No. 9), 

 1894. 



