62 RECONNAISSANCE IN NORTHERN ALASKA IN 1901. 



series to \ iew along- the axis of the fold. These arc apparently the lowest and oldest 

 rocks exposed in the northern part of the range. 



Toward its northern limits and the crest of the fold, as has been noted, the 

 Stuver series dips southward at an angle of 30°. But still nearer its northern 

 limits, practically at the crest of the fold, the beds have been strained, bent down- 

 ward, and broken, and finally terminate in a well-defined fault scarp, as shown in the 

 section on PI. III. This scarp trends a little south of east and is visibly pronounced 

 for at least 5 or 6" miles. Along this distance, in the higher part of the mountains, 

 the edges of the broken, hard conglomerate beds forming the scarp are distinctly 

 exposed, generally dipping about 30° S., while at a lower elevation along the face 

 of the scarp the broken-off portions of the same strata have dragged behind along 

 the lower face of the scarp and stand nearly on edge, dipping northward at an angle 

 of 80°. These nearly vertical beds of the Stuver series are met at the contact on the 

 north by the limestone of the Lisburne formation, which dips south at an angle of 

 75° to 80°. (See section on PI. III.) The contact of the two formations thus forms 

 a reentrant angle of 25°, opening upward. 



The conglomerate of the Stuver series, toward its north edge and along the fault 

 scarp, is intersected by two systems of jointing about equally pronounced. One 

 system trends east and west, with dip vertical; the other nearly north and south, 

 with dip to the east at an angle of 80°. On the top of a low mountain along the edge 

 of the scarp the same hard conglomerate is finely laminated by a well-marked 

 cleavage trending N. 60° E. and dipping northwestward at an angle of 45°. 



No estimate can be formed of the thickness of the Stuver series, as its lower 

 limits are unknown. The exposed portion shows a thickness of at least 2,000 feet. 



Age. — The Stuver series, from its position underneath the Lisburne series, which 

 on paleontologic evidence is considered to extend to below Middle Devonian, is 

 certainly not younger than Lower Devonian, and it is regarded as probably pre- 

 Devonian. 



Correlation. — No other Alaskan rocks with which it may be correlated are known 

 to the writer. Sediments, notably of fine conglomerate, containing materials similar 

 to those forming the conglomerates of the Stuver series, have been noted in the 

 Mission Creek series of the Yukon district; but probably these, like the sediments 

 derived from the Stuver series and now found in the Tertiary and other formations 

 on the Arctic slope, have been many times deposited and reworked since they were 

 derived from their original source. 



LISBURNE FORMATION (DEVONIAN). 



Character and occurrence. — Lisburne formation is the name here employed to 

 designate the limestone, with some shale, occurring next above the Stuver series at 

 the head of Anaktuvuk River. The name is taken from Cape Lisburne, where 



