328 PAIGE AND KNOPF STRATIGKAPHIC SUCCESSION IN ALASKA 



The thickness of this aeciimiilation often exceeds 1,000 feet. The tuffs 

 locally carry fragments of lignite, and at one point were found to contain 

 marine shells in a fine state of preservation. The fossils were submitted 

 to Dr T. W. Stanton, who reports in part : 



" Rhynconella. Astarle [f). 



Lima. Protocardia. 



Pecten — smooth species. Pleuromya. 



Pecten — species of Vola type. Sonnirda {?). 

 Trigonia. 



"The Jurassic age of this lot is clearly shown by the form of the Trigonia and 

 of the Ammonite (Sonninia ?). The general aspect of the fauna is that of the 

 lower part of the Enochkin (Middle Jurassic)." 



\ The greenstones and tuffs just described are transitional into an over- 

 lying series of graywackes, sandstones, shales, and subordinate conglom- 

 erates. 



: Several of these latter, of very diverse constitution, occur interstratified 

 with seams of low-grade bituminous coal. In the northeastern part of 

 the field several hundred feet of stream bluffs 100 feet high are composed 

 of conglomerate consisting of various porphyries and white quartz pebbles 

 an a gritty, coherent matrix. 



The shales and sandstones of this series are in general barren of fossils, 

 though Belemnites are ratber common. 



Inoceramu^j cf. lucifer Eichwald. Stephanoceran. 



Pleuromya. Opj)elia [f). 



Pleurotom.aria: . Natica. 



Phylloceras. Sonninia {.') — two species. 



Doctor Stanton, who examined the fossils, states "tliat tliey may be 

 referred Avithout question to the lower part of the Enochkin formation 

 as it occurs at Snug Jiarbor," on the west coast of Cook inlet. 



The beds are usually lying in monocliual attitudes, lirokon l)y l_)lock 

 faulting. Whatever folding is shown is, with one exception, of an open 

 character. Evidence, however, of severe internal disturbance, such as 

 the frequence of faulted pebbles in the conglomerates, is abundant, and 

 shattering and minor faulting are widespread. 



The series of rocks just described are separated from those next higher 

 in the column by an important unconformity. At one point sandstones 

 introduced by a thin basal conglomerate were found resting on the eroded 

 edges of the Lower Middle Jurassic greenstones. The absence from the 

 yoimger rocks of the profound shattering and shearing characteristic of 

 the older rocks, and the strong discordance in their respective strike lines, 



