PALEOZOIC ROCKS,- SKA JIT FORMATION". 57 



formation as it disappears to the north unconforniably under the Fickett series. In 

 some localities, however, the faulting and folding- have been intense. 



Like the other Paleozoic rocks of the range, the Skajit formation is cut diag- 

 onally by the dominant northeast-southwest jointing, which divides the rocks into 

 nearly vertical sheets varying from less than 1 to more than 10 feet in thickness, and 

 by the secondary jointing sometimes at nearty right angles to this direction. 



The joint planes are usually nearly vertical or have a steep westerly dip, and are 

 sometimes locally followed by veins or veinlets of calcite and some quartz, carrying 

 occasionally a little galena or iron pyrites and copper. Prospectors report that 

 galena, probably of economic value, occurs on Wild Creek, 25 miles east of our 

 route, in a wide "ledge" in limestone probably belonging to the Skajit formation. 



Cleavage was also noted in a few instances, but none so pronounced or so well 

 developed as that observed in similar rocks in the area to the east, at the head of 

 Chandlar River. 



Age. — The Skajit formation, as seen in the geologic section, probably repre- 

 sents the oldest or next to the oldest rocks in the field. It is the principal formation 

 forming the southern axis of the Endicott Range, of which it seems to be the lowest 

 terrane exposed. It is unconforrnably below the Fickett series on the north, and 

 apparently bears similar relation to the Totsen series on the south, where, as shown 

 in the geologic section on PL III, the probable unconformity is indicated by the beds 

 of the Totsen series lying at a steeper angle than those of the Skajit formation, as 

 well as by an abrupt change in the chai"acter of the sediments along the zone of 

 contact. Similarly, on the north, where the heavy-bedded limestone of the Skajit 

 formation finally disappears with a northerly dip, it is met by the overlying slates 

 and schists of the Fickett series dipping south (section on PI. Ill and PL X, A). 



Though the limestone, as noted, is much altered by metamorphism, it contains 

 faunal remains, some of which were collected in place on John River. While most 

 of these forms are too greatly altered for determination, a single specimen has been 

 identified by Mr. Schuchert as " having the ventral valve of a brachipod of the order 

 of Meristina and Meristella, and also resembling a transverse Seminula. This kind 

 of shell indicates that the rock can not be older than Upper Silurian and not younger 

 than Lower Carboniferous." 



On this evidence, and because the rock is much more disturbed and metamor- 

 phosed than the limestone of the Lisburne formation, in which Devonian fossils have 

 been found in the northern axis of the range, the Skajit formation is provisionally 

 referred to the Upper Silurian. This, if the inference be correct, places it among 

 the oldest known fossil-bearing formations of northern Alaska. Late Upper Silurian 

 forms have been found in the Glacier Bay limestone in southeastern Alaska." Ordo- 



<i Brooks, A. H., Preliminary report on the Ketchikan mining district, Alaska: Prof. Paper U. S. Geol. Survey No. 1, 

 1902, pp. 19-20. 



