430 EEPOET UNITED STATES GEOLOGICAL SURVEY. 



Section through Station XLII. 



1. Pink-colored tracTiyte, associated witTi dark basalt, dipping east- 

 ward at an angle of 15^. These deposits crown the elevation at Station 

 XLI, and that to the northwest in the opposite side of the debouchnre 

 of a small stream which here penetrates the foot-hills. 



2. Blue, rusty weathered, shaly sandstone, forming a narrow ledge 

 exposure, which dips 35°, northeasterly. It is underlaid by gray, shaly 

 sandstone debris. 



3. Gray, brown weathered, shaly sandstone, dip 15°, south westward; 

 exi)osed in the foot of the opposite slope which rises into the prominent 

 hog-back ridge overlooking the volcanic border-ridges. 



4. Crossing a space of several hundred yards, in which no rock ex- 

 posures appear, in the steeper northwest acclivity three ledges of gray, 

 shaly sandstone outcrop, including a vertical thickness of CO to 100 feet, 

 and dipi)ing southwesterly at an angle of 20° to 30°. From these ledges, 

 which doubtless i)ertain to the same age as the previously-mentioned 

 sandstones, we pass over the steep cZe'&m-covered slope to a point near 

 the crest of the ridge, where the following bed appears : 



5. Drab, fragmentary limestone, with segments of the column of 

 Pentacrinites, showing a thickness of about 20 feet, in nearly vertical 

 position, or dipping at an angle of 85°, southwesterly. This bed is sep- 

 arated from the succeeding by a narrow space, in which appear the fol- 

 lowing : 



6. Drab, shaly limestone and indurated deposits, containing a small 

 Ostrea, like 0. strigulecula White, which, together with Pentacrinites re- 

 mains, determine the Jurassic age of this horizon. The same an d associated 

 ledges are also seen in the steep ridge to the south. 



7. Bluish-gray, shaly, fine-grained sandstone, exposed 5 to 10 feet in 

 sharp hog-back crest of the ridge, dipping 85°, W. 15° S. 



8. In the succeeding space of 200 yards or so, obscure exposures of 

 pink-buffc' sandstone alone indicate the character of the several hiuidred 

 feet of superimposed material. 



9. Drab limestone, forming a heavy ledge, which dips steeply to the 

 southwestward. 



10. Very hard buff-gray and pink sandstone, containing obscure 

 vegetable remains. This rock forms a heavy ledge, outcropping in the 

 southwest slope of the ridge, which descends to the lower level of the 

 intervening basin, in which the succeeding exposures are indifferently 

 revealed, in part owing to their more friable nature, the materials de- 

 rived fi?om their easy disintegration effectually covering considerable 

 areas of the undulating surface. Hence the following beds, which out- 

 crop at intervals, probably show only the more indurated layers of a 

 heavy series of deposits which fill the basin area above outlined. These 

 are referred to under IsTos. 11 to 13, inclusive, as follows : 



11. Grayish and bluish-gray, thin-bedded sandstones, appearing in 

 low obscure outcrojis littering the surface with debris. 



12. Gray, thin-bedded sandstone below, dark gray and buff-reddish, 

 shaly, laminated sandstone above. In the belt apparently occupied by 

 the above deposits, a heavy bed of drab indurated shales and dark 

 brown- gray limestone layers occur, which afford fragments of a small 

 Ostrea ( 0. strigulecula f ) and Pentacrinites, like those occuriiug in bed 

 No. 5 ; the latter deposits were observed in the steep slope south side of 

 the little stream which flows out into the basin immediately north of 

 Station XLI, but their actual relationshi]} to the gray sandstones was 

 not satisfactorily disclosed. 



