HP]NRY'S FORK BASIN. 265 



spots. The upper 150 to 200 feet consist of sandstones, with a varying 

 admixture of colored clays, the former frequently having a shaly structure, 

 and containing some calcareous seams with indistinct fossil remains. Below 

 these is a body of bluish-drab limestones and calcareous shales, from the 

 latter of which were obtained, JRliynconella Myrina, R. gnatliopora, Lima 

 {plagiostoma) occidenfaUs, CavvpUmecies heIUst)-?ahf,s, and GrypJ/aa calceola. 

 These limestone beds have a thickness of about 200 feet, and are underlaid 

 by a deep Indian-red sandstone of 100 feet in thickness, running below into 

 a series of sandstones and sandy limestones, which form the base of the 

 series, containing thin beds of gypsum, but whose thickness could not be 

 accurately estimated, as they were partially covered by surface debris. 



In the Triassic formation the upper half consists of characteristic strata 

 of massive buff or white sandstone, with remarkably well-developed lines 

 of cross-bedding, and very thick beds, often nearly 100 feet without strati- 

 fication-lines. They form the summit of the ridge, and are developed to a 

 thickness of nearly 1,000 feet, a bed of about 50 feet of yellow, argillaceous 

 sandstone dividing them into two nearly equal parts. The lower half of the 

 Triassic, which forms the cliffs overlooking the Horseshoe Canon of Green 

 Eiver, also nearly 1,000 feet in thickness, consists of an upper portion of 

 pinkish-red sandstones relatively rather thinly bedded, the lighter color 

 being due to an alternation of thin beds of nearly white color, and a lower 

 portion of dafker-colored and more heavily-bedded red sandstones, sepa- 

 rated from the former by some argillaceous beds, and at the base running 

 into clay beds with gypsum. 



The valley of Green River, at the base of the cliffs, is eroded out of a 

 series of light-colored beds, largely clays, of a prevailing greenish hue, whose 

 thickness could not be estimated, and which have been considered to belong 

 to the Permo-Carboniferous group. 



Along the northern base of the Flaming Gorge Ridge are low outcrops 

 of sandstones of the lower members of the Cretaceous, with narrow 

 included monoclinal valleys, which follow the outlines of the main ridge, but 

 in the open valley of the basin west of Plenry's Fork the Quaternar)'- 

 covering conceals the earlier members. In following up this stream, then, 

 the first outcrops are found at the gap just where it emerges from the 



