HORN EXPEDITION — GENERAL OEOLOOV. 57 



GOOO feet nf sandstones and (jnattzitps, some small part ))eing composed of tliinly- 

 bedded, hi<;ldy ai\<,'illaceous sandstone, passing iiito red micaceous clay sli;i-le. 



Fossils were found in the quartzite about half a niili^ north of Camp 2.") on 

 Petei-mann Creek, and again at two-and a half-miles north of the same point. 

 Furtiier north still, on the northern half of this great denuded anticline, the fossili- 

 ferous Iiorizon in the (piartzite was again met with ; while still fui'tlicr in the same 

 direction, neai' Tempe Downs .Station, the fossilifcrous limestone, on the same 

 horizon as that mentioned above, comes to the surface, and has yielded many 

 fossils. 



A vertical section of the fossilifcrous Ijeds in INIiddh^ ^^alley at Tempe Downs 

 is as follows : — 



Thit'kness. 



Three bands of fossilifcrous limestone, from two to four inclies thick, 



(lijiping at S0° to the south, sepaiated by sandy clay-slates - 45 feet. 



Sandy clay -slate, charged with Asaphiis illare/isis, passing into - - l-.j ,, 



Soft sandstones crowned by .a ([uartzite, which is fossilifi'rous - - 40 ., 



'J. ( )i)i,iriiinna Pass Section. — The Oooraminna Range, which has a breadth of 

 seven miles, is intersected in a north and south dii-ection by a narrow valley 

 excavated to a depth of from 200 to 300 feet. The basal rocks are bluish-gi'ey 

 dense limeston(>s in courses of two to four feet thick, separated by thinner llssih; 

 limestones. They strike W. 10" N. and dip from an anticlinal ridge at 1)° ; a total 

 thickness of forty feet was measured in the limestone series. In distinct conforma- 

 bility tlu^re succeed quart/.ose sandstone and two chief quartzite bands, the 

 uppermost of which forms the chief surface-i'ock of the range (.see Section S). No 

 fossils were observed, Ijut a hai'd yellow sandstone forming part of the corres- 

 ponding arenaceous seiies in James Range, penetrateil in the well sinking at 

 Deep Well, contained casts of Isoarctc. Limestones similar to those of the 

 Ooraminna Pass, and readily recognisable by their exceedingly hackled weathered 

 surfaces, form the superstructure of the country from James Range to the southei'ii 

 boundary of the Ordovician area. 



The quartzites of the Ooraminna Pass are somewhat irregularly developed, 

 and occasional instances were observed, particularly at ( )oraminna Waterhole, of 

 the grailual passage in a horizontal direction from sandstone to (piartzite. A 

 reniarkalile physiographic feature is pi-esented at the south escarpment of the 

 range in the form of four or tlve tall, wall-like masses of ([uartzite in close 

 proximity (locally known as lldl (Jates). The pl.iiies of si-ratilication in tlu^ 



