MESOZOIC ROCKS, ANAKTUVUK SERIES. 75 



so-called Meade River Mountains, and, continuing northwestward, may extend to 

 the Arctic coast. 



The series consists essentially of impure sandstone or arkose, with a little tine 

 conglomerate. The sandstone is usually heavy bedded, beds 6 to 8 feet in thickness 

 being common, and it is generally fine to medium grained, but in some localities 

 becomes so coarse as to be almost a grit. In color it ranges from dark or bluish gray 

 to dirty greenish, while the coarser grained rock often presents a speckled or salt- 

 and-pepper appearance, and is seen to be composed of grains of the variously colored 

 flints represented in the Stuver conglomerate. In fact, the color of the rock through- 

 out seems to be determined largely by the relative abundance of the different colored 

 sediments from the Stuver series. 



Northward from the mountains the rocks, though distinctly sedimentary, contain 

 also some detritus of igneous rocks, as fragments of feldspar and some dark mineral, 

 apparently augite or hornblende. The igneous l-ocks from which such sediments 

 have been derived probably occur in the mountains lying far east or southeast of the 

 plateau, as none were observed in the mountains in the region of the Anaktuvuk. 



Conglomerate is apparently rare in the series, having been observed at but a 

 single place — on the right bank of the Anaktuvuk about 2 miles below the mouth of 

 Willow Creek, where it is exposed in a low point, interbedded with a few lens-like 

 layers of sandstone. The conglomerate is typically' rather fine, with scarcely a 

 pebble exceeding three-fourths of an inch in diameter. The pebbles and cement are 

 composed largely of sediments of the Stuver series, white quartz and dark or slate- 

 colored flint being the most conspicuous. The pebbles are noticeable for their 

 angularity, suggesting glaciation about the time the series was deposited. The 

 cementation is relatively firm for a young rock, but is not comparable with that in 

 the Stuver or Fickett series. The cement is mainly siliceous, but contains also 

 calcareous material, probably derived from the Lisburne formation. 



Owing to the low relief and the covering of drift and moss, no accurate idea 

 can be formed of the thickness of the Anaktuvuk series, but it is estimated to be 

 at least 2,000 feet. 



Structure. — The strike of the Anaktuvuk series is approximately east and west, 

 agreeing in this respect with the several series of rocks that compose the range to 

 the south. Broadly considered the structure seems monoclinal. The rocks in 

 general dip gently northward at varying angles, but subordinate gentle anticlinal 

 and synclinal folds are present, the latter being occasionally open. These were 

 probably caused by the same mountain-building forces that were exerted in the range 

 to the south. This is suggested by the fact that the trend of the more pronounced 

 folds in the plateau is parallel with the main folding of the range, as if all belonged 

 to the same system. Besides the east-west major flexures, the plateau is also 



