PENNSYLVANIAN-PERMIAN GLACIATION 467 



THE BOULDER CONGLOMERATES 



While the distinctive evidence of the supposed glaciation is 

 furnished by the occurrence of poHshed, striated, grooved and 

 deeply fluted rock surfaces, nevertheless these particular erosion 

 features were discovered only as the direct result of investigating 

 the origin of certain non-residuary boulder conglomerates which 

 are widespread in the region. These conglomerates form a series 

 of distinct beds ranging throughout a large part of the Pennsylvanian 

 and well up into the base of the Permian. Although the striated 

 rock surfaces are found in association with only some of the latest 

 boulder conglomerates, these conglomerates are all essentially the 

 same in character, hence it is inferred that they have had a common 

 origin under glacial conditions. 



The boulder conglomerates of Pennsylvanian-Permian age in 

 the Arbuckle Mountain region that are believed to have been formed 

 either directly or indirectly by glacial action, include what has been 

 termed the Franks Conglomerate. 



The Franks Conglomerate at the type locality in the vicinity 

 of Franks (see map. Fig. i), on the northeastern slope of the 

 Arbuckle region, consists of several distinct beds of conglomerate 

 each 100 to 350 feet in thickness, interstratified with limestone, 

 shale, and sandstone. The lowest conglomerate bed is about 150 

 feet in thickness and overlies the eroded edges of the 

 pre-Pennsylvanian rocks of the locaHty. The beds at higher hori- 

 zons occur as intra-formational conglomerates within the Pennsyl- 

 vanian. At least as many as five distinct conglomerate beds may 

 be distinguished at Franks, and at other localities on the north side 

 of the Arbuckles. The Franks, therefore, consisting of a series of 

 conglomerates rather than a single bed, it is convenient to refer to 

 it for the present at least as the Franks series. On the south side 

 of the Arbuckle Mountains several beds of conglomerate like the 

 Franks have been recognized in the Pennsylvanian series, though 

 they are not so thick as those on the north side. 



In the Wichita Mountain region there are also thick conglom- 

 erate beds essentially of the same type as the Franks series in the 

 Arbuckles. But the Wichita Mountain conglomerates have not 

 been called Franks Conglomerate, for they have been usually con- 

 sidered of later origin than the Franks. 



