366 REPORT UNITED STATES GEOLOGICAL SURVEY. 



present determination, there is found in the northern third of the pres- 

 ent section a somewhat different series of arenaceous deposits, mainly 

 characterized by their prevailing grayer color and generally looser text- 

 ure, and the greater preponderance of shaly deposits with which they 

 are interbedded. At a locality a mile or so above the upper entrance to 

 Fall Creek Canon these deposits appear in the low bluffs of an arroya 

 on the southwest side of the valley, where they exhibit a vertical thick- 

 ness of perhaps 75 feet. They consist of (a) a stratum of brown-gray, 

 jointed, spar-seamed sandstone, which outcrops in the bed of the gully ; 

 (b) blue and chocolate-red shales, 50 to 75 feet; (c) gray, spar-seamed, 

 coarse-grained, sometimes conglomeritic, sandstone, in places thin-bed- 

 ded, with oblique laminae, alternating with hard and soft layers, of which 

 a thickness of 10 to 12 feet is exposed, dipping at angles of 25° to 33°, 

 X. to X. 15° E. This locality derives much interest from the occur- 

 rence in the upper sandstone (c) of the remains of a flora, which is 

 represented by several varieties of as many dicotyledonous generic types. 

 These were submitted to Professor Lesquereux, and in a note kindly 

 announcing the result of his examination, the most perfectly preserved 

 form is referred to Auralia. The specific affinities of this fossil are 

 thought to be intimate with Dakota Group forms ; but while Professor 

 Lesquereux takes due cognizance of this fact, he observes the probable 

 later origin of this flora, and the strata in which it occurs, belonging to 

 an epoch represented by the transitional or Laramie Group, which ush- 

 ered in the dawn of the Cenozoic time. The conclusion here indicated 

 corresponds with the discoveries reported by the survey in the country 

 to the south, where vegetable remains of the same general facies, here 

 referred to, are met with in otherwise well- determined Laramie horizons. 

 In the opposite and steeper acclivity on the northeast side of Fall 

 Creek basin, a splendid series of strata in direct continuation of the 

 foregoing section is pretty well exposed, affording the data for the fol- 

 lowing detail stratigraphic section. This side of the valley is bounded 

 by a rather regular ridge, which may be traced many miles to the south- 

 east, where it culminates in a high crest at the head of Pyramid Creek, 

 8,800 feet in altitude. It reappears in the heights south of McCoy Creek, 

 between Station XXVII ancl Mount Caribou (Station XXVIII), while 

 to the northwest it forms the portal of the upper entrance to Fall Creek 

 Canon, and finally dies out some distance beyond Station XX, where its 

 altitude is 7,400 to 8,000 feet above sea-level. As seen from Station 

 XIX, the southwest slope of this ridge, descending into the mountain- 

 basin, is painted in bright bands of color, light drab and pale red, and 

 is for the most part quite free from trees. The upper portion of the slope 

 is broken into three, more or less, gradually steepening tilted benches, 

 from the foot of which a wide apron sweeps down into the valley, where 

 it terminates in bluffs 100 to 200 feet in height, which here hem in the 

 intervale-margined trout-stream. It is in the latter bluff-face the lowest 

 or first exposures in this northeast border ridge are met with, and these 

 belong to the series last mentioned in connection with the preceding sec- 

 tion in the opposite slope of the valley. The section is as follows : 



Section in the northeast border of Fall Creek basin. 



29. a, red and blue shales ; b, gray, shaly sandstone, 5 feet exposed, 

 underlaid by hard, indurated, ferruginous, gritty bed, dip X. X. E.; c, 

 red and blue shales. 



30. Long grassy slope, in which obscure exposures of red and drab 

 shales appear. 



