288 BROOKS AND KINDLK PALEOZOIC ROCKS OF UPPER YUKON 



almost certainly to belong to the species BucMola retrostriata, an Upper 

 Devonian form verj^ characteristic of the jSTunda or Portage in the New 

 York section. The shales in which it w^as found resemble those of the 

 ISTunda. 



These drab shales are followed above by black shales in the section as 

 developed betn^een Eagle and Calico bluff. The black shales, which some- 

 times are altered to slate, are well exposed in the northeast bank of the 

 Yukon one-half mile above Calico bluff. Here a small Lingula somewhat 

 like L. spatulata occurs sparingly. No other fossils were found in the 

 black shale at this place. The same beds form the base of the Calico 

 Bluff section where their relation to the Carboniferous series is clearly 

 shown. The section exposed at Calico bluff is given below in order to 

 show in detail the transition of the Carboniferous series : 



Calico Bluff Section 



Feet 



0. Gray to blackish shale, with few bands of limestone 300 



n. Gray limestone in 6-inch to 12-inch bands, interbedded with thin bands 



of black shale 500 



m. Black shale and subordinate thin bands of limestone 60 



1. Black carbonaceous shale 50 



k. Gray chert and black shale 6 



;. Dark gray limestone full of Productus, etcetera 9 



i. Dark carbonaceous shale 20 



h. Gray cherty limestone 25 



g. Soft fissile black shale 55 



f. Gray chert S 



e. Fissile black carbonaceous shale 150 



d. Black carbonaceous shale, with slaty cleavage developed in most beds. . 100 

 c. Black carbonaceous shales, with some thin black chert bands inter- 

 bedded 40 



6. Black cherts in 4-inch to 6-inch bands and interbedded black shale 55 



a. Black carbonaceous fissile shale 150 



Total 1528 



The only fossils found in the lower 500 feet of this section is a small 

 Lingula somewhat like L. spatulata, but a different species. In number ? 

 of the section occurs a Leiorhynchus closely allied to L. laura Billings 

 and a Chonetes somewhat resembling C. manitoiensis. Characteristic 

 Lower Carboniferous fossils appear in the section in the divisions above g. 



While the Devonian age of the beds below number h can hardly be posi- 

 tively affirmed from the evidence of the three species found in them, the 

 entire absence of characteristic Carboniferous fossils from this portion 

 of the section and the still lower drab and reddish shales seen elsewhere is 



