Vol. VI] WEAVER— EOCENE OF LOWER COWLITZ VALLEY 5 



sist of thinly bedded, fine-grained, dark brown shale contain- 

 ing a few narrow bands of sandstone. The total thickness of 

 the sediments at this point is about 75 feet. They are overlaid 

 with 35 feet of black basalt showing well defined columnar 

 jointing. Both the sedimentaries and lavas have a strike of 

 N. 80° E. and a dip of 10° to the N. W. 



About one-half mile south of the railway bridge across Cow- 

 litz River there is a third exposure of Eocene basalt but no 

 sedimentary rocks. The lower portion of the bluff is made up 

 of agglomeratic materials consisting of a heterogeneous mass 

 of angular fragments of badly weathered, dense and vesicular 

 basalt having a thickness of 20 feet. Above this is a flow of 

 fine grained, dense, black basalt exhibiting a tendency to col- 

 umnar structure. The approximate strike of these flows is 

 nearly east and west with a low dip to the north. The eroded 

 surface of this outcrop is overlaid with Pleistocene sands and 

 gravels. 



One-half mile north of the previously mentioned outcrop, 

 and along the south bank of Cowlitz River at the railway 

 bridge, basalts and sedimentary rocks again appear. At the 

 south end of the bridge and along the river there is a quarry 

 composed of basalt exhibiting pronounced columnar structure. 

 Lying conformably below the basalts are dark shales and brown 

 sandstones, which in places contain narrow carbonaceous 

 bands. They are about 60 feet in thickness with a strike of 

 N. 35° W. and a dip of 10° to the N. E. From this point 

 northward to the town of Olequah no recognizable exposures 

 of the Eocene occur. 



At one of the above mentioned localities a single speci- 

 men of Turritclla nz'asajia Conrad was collected, but aside from 

 this, the only fossils occurring are a few plant fragments 

 and wood. From observations taken upon strike and dip there 

 appears to be a continuous low dipping series of sedimentary 

 beds with intercallated basaltic flows extending from Castle 

 Rock to Olequah. However, it is possible that there may be 

 folding and faulting in the intervening covered areas. If the 

 strata are continuously dipping northward they possess a thick- 

 ness of at least 6000 feet. From Olequah northward to Win- 

 lock, where the strata are better exposed, a stratigraphic sec- 



