698 G. C. MARTIN TRIASSIC ROCKS OF ALASKA 



ciation with the Kamishak chert. Its exact relations to the latter forma- 

 tion are somewhat doubtful, but it is believed to underlie it. It contains 

 a species of Halobia which resembles the Alaskan species that is usually 

 compared with Halobia superb a Mojsisovics, and which may indicate that 

 the limestone corresponds in general position with the Chitistone lime- 

 stone and is of Karnic age. 



The Kamishak chert consists of banded cherts, calcareous shales, and 

 thin limestones in the upper part, grading downward into more massive 

 beds of dark chert. The total thickness is at least 1,000 feet and probably 

 exceeds 2,000 feet. The upper shaly and calcareous part of the formation 

 contains Pseudomonotis subcircularis (Gabb), but the lower, more mas- 

 sive cherts have thus far yielded no fossils. The upper part of the forma- 

 tion is with little doubt the equivalent of at least part of the McCarthy 

 formation and is of Upper Noric age. There is considerable doubt, how- 

 ever, concerning the exact age and correlation of the lower and more 

 cherty members. There is a strong presumption in favor of correlating 

 them with the cherts of Chitina Valley, which likewise are of somewhat 

 doubtful age and position, although they apparently belong near the base 

 of the McCarthy formation and are closely associated with, even though 

 they may not include beds containing, Pseudomonotis subcircularis 

 (Gabb). 



The Triassic rocks of the east coast of Cook Inlet, which are situated 

 in the southwest end of Kenai Peninsula, include 16 limestones and tuffs 

 with Upper Triassic fossils. These beds are apparently underlain by con- 

 torted cherts which have yielded no characteristic fossils, but which the 

 writer believes to be of Upper Triassic age. Beneath the cherts are ellip- 

 soidal lavas which are underlain by slate and graywacke. The Upper 

 Triassic limestones and tuffs are overlain, probably unconformably, by 

 Lower Jurassic tuff and agglomerate. 



The fossiliferous Upper Triassic rocks of the Kenai Peninsula, as ex- 

 posed on Port Graham, are composed of limestones, cherts, and tuffs. 

 Their thickness is at least 1,000 feet. Pseudomonotis subcircularis 

 (Gabb) occurs near the top of the sequence, and lower clown a species 

 of Halobia has been found. The former species indicates that at least 

 part of the succession is of Upper Noric age, and is to be correlated ap- 

 proximately with the McCarthy formation and with the banded cherts 

 and calcareous shales in the upper part of the Kamishak chert. If the 

 Halobia is identical with the Alaskan and California species usually re- 

 ferred to Halobia superb a Mojsisovics, it possibly indicates that the lower 



16 G. C. Martin : The western part of Kenai Peninsula. U. S. Geol. Survey Bull., No. 

 587, 1915, pp. 52-63. 



