NO. 5 PRE-DEVONIAN PALEOZOIC FORMATIONS 275 



Feet Meters 



Fauna. — (58b) : small fauna of undescribed forms. 

 ic. Arenaceous, purple shale, with interbedded gray shaly 



limestone in thin layers 265 80.8 



The highest of the purple layers occur near the 

 summit of ic. 

 id. Siliceous, fine-grained, thin-bedded, buff-weathering 



limestone 63 19.2 



Total Bosworth formation 423 128.9 



Arctomys Formation 



la. Arenaceous and calcareous shale, purple- and gray- 

 colored with thin, intercalated buff-weathering cal- 

 careous layers. Mud cracks, ripple marks, and the 

 pseudomorphs of large salt crystals occur in the 

 arenaceous beds 158 48.2 



I fe. Thin-bedded, compact, drab-colored limestone 60 18.3 



Total Arctomys formation 218 66.5 



MIDDLE CAMBRIAN 

 Eldon Formation 



la. Thin-bedded (2 to 6 inches [5 to 15 cm.] ), gray siliceous 



limestone 265 80.8 



Fauna. — Numerous large and small annelid trails and 

 borings. 



lb. Bluish-black and gray fossiliferous limestone becom- 

 ing more or less arenaceous toward the top 260 79.2 



Fauna. — (sSe) : Annelid trails, and two or three species 

 of trilobites. 



IC. Steel-gray weathering light gray arenaceous limestone 



in thin layers 55 16.7 



id. Massive-bedded, light gray, finely granular, arenaceous 

 limestone which weathers more like a compact granu- 

 lar sandstone than a limestone. This limestone is 

 usually very massive, but between 540 and 575 feet 

 (164.6 and 175.3 m.) above the base it is thin-bedded. 1,065 324-6 



This is the great cliff-forming limestone of the 

 mountains and ranges in this region. It forms the 

 upper cliff of Castle Mountain. 



Fauna. — Numerous annelid trails and borings occur at 

 various horizons. 



le. Massive-bedded, cliff-forming, dark and light gray are- 

 naceous limestone, the massive layer breaking up 

 into thin layers on broken cliffs and talus slopes. The 

 dark-colored band forms the lower 200 to 250 feet 

 (60.9 to 76.2 m.), the line of demarcation between the 

 dark band and the lighter gray being irregular 260 79.2 



Total Eldon formation 1,905 580.5 



