The Hermit Formation
Hermit Formation-Upper Supai shales of Darton (1910) were allocated to a separate formation, the Hermit Shale by Noble (1922); a marked unconformity was recognized at the base of the Hermit. Red-brown sandstones and siltstones above the Supai and beneath the Coconino Sandstone are well exposed along the Hermit Trail in the Grand Canyon National Park. McNair (1951) pointed out that the Hermit consists mostly of fine-grained sandstone, silt-stone, and massive claystone, and contains little shale. Fisher (1961) notes that throughout most of the Grand Canyon area the Hermit ". .. is characterized by dark red-brown or brick-red, fine-grained sediments which contrast with the orange-red or buff color of the Supai Formation and the light gray or buff-gray of the Coconino Sandstone."
Thicknesses of the Hermit Formation vary from about 100 ft. in easternmost sections to about 900 ft. in the western part of the Grand Canyon. Noble (1922) called attention to the marked westward thickening of the Hermit from 100 ft. in Tanner Canyon in the eastern park area to 317 ft. in the type section and 332 ft. west of the type section at Bass Trail. Sorauf (1962) indicated that the measured thickness of the Hermit is 1,095 ft. at Paw's Pocket in eastern Whitmore Wash, and 1,029 ft. directly south of Whitmore Point in southwestern Whitmore Wash. Fisher (1961) reported a thickness of 1,061 ft. for the formation in Parashant Canyon. These latter two geologists have accumulated a substantial body of detailed stratigraphic data pertaining to the Hermit Formation; the interested reader is referred to their contributions, for the Toroweap-Whitmore-Parashant-Andrus area along the north part of the Grand Canyon.
McNair (1951, p. 527-528) referred almost 700 ft. of dull red, very fine-grained sandstones to the Hermit Formation in the North Grand Wash Cliffs, Mohave County, Arizona, and 933 ft. of similar rocks in the same county in the Hurricane Cliffs. The detailed stratigraphic section measured by Welsh (1959) at-Pakoon Ridge consists of 1,071 ft. of fine-grained buff-yellow, white, red, and red-pink sandstones, red to white siltstones, and a thin gypsum bed. The writer's section at Tramp Ridge totals 1,094 ft. of variegated siltstone, gypsiferous siltstone, very fine-grained sandstone, and earthy sandstone. Welsh (1959) reported a thickness of 1,058 ft. for the Hermit Formation farther north in Nevada in the North Virgin Mountains (S 36, T 14 S, R 70 E), where it consists mostly of fine-grained red sandstone with minor siltstone. The formation thickens to about 1,400 ft. in the North Muddy Mountains south of Glendale Junction, there consisting of interbedded sandstone, limestone and siltstone below, giving way upsection to sandstone and siltstone with minor shale; colors vary from deep red and brick-red through pink, buff, and gray to white. Welsh (1959) indicated a thickness of 1,337 ft. for the Hermit in the western part of the Valley of Fire (S 34, 35, T 17 S, R 66 E) near a sharp curve in the road which crosses the section. His section indicates presence of 43 ft. of white to red gypsum and siltstone at the base, overlain in sequence by 254 ft. of red and gray siltstone and very fine-grained sandstone (both with some gypsum), 136 ft. of interbedded gypsum and fine-grained sandstone, and 904 ft. of buff, fine-grained sandstone at the top.
The writer measured a total thickness of 1,038 ft. of the Hermit Formation in and adjacent to a strike-valley east of Frenchman Mountain; the formation consists of red and variecolored siltstones, silty and earthy fine-grained sandstones, and fine-grained massive sandstones. No other sections of the Hermit crop out in close proximity to Frenchman Mountain; as the Las Vegas hinge line is crossed, the nearest essentially complete Hermit succession in outcrop is near Cottonwood Pass (eight miles north of Goodsprings), about 30 mi. southwest of Frenchman Mountain. At this locality in the Bird Spring Range, the Hermit Formation consists of 750 ft. of buff, pink, and red fine- to very-finegrained sandstone and siltstone. A sharp contact with the underlying Queantoweap Formation exists, marked by buff sandy dolomites and calcareous sandstones in upper units of the Queantoweap, contrasting with red siltstones in the basal Hermit. Seemingly no Coconino overlies the Hermit here, and dolomite in the basal overlying Toroweap Formation contrasts with uppermost beds of the Hermit.
Fossils were not found in the Hermit Formation during the course of field investigations on this project. In his monographic study of the flora of the Hermit, White (1929), 35 species of fossil plants were described; he stated that representatives of both the western European flora and the Eurasian Gondwana flora are among these species. This establishes a Permian age, and White correlated the Hermit with the Leonard. Dunbar et al. (1960) have accepted this age determination. Also, as a result of his studies with the Hermit flora, White concluded that the sediments which enclose these fossils were deposited in a semi-arid climate, with long dry seasons. Sorauf (1962) believed that presence of red coloration, scour, cross-bedding, desiccation cracks and current ripple marks in the Hermit in the Whitmore area supports an interpretation of the environment of Hermit sedimentation as a semiarid coastal plain. McNair (1951) did not elaborate concerning environmental conditions under which the Hermit accumulated in the Grand Wash Cliffs area, but commented: "It lacks the limestone beds of the eastern Supai and apparently was deposited when the Permian limestone-redbed boundary was a considerable distance northwest of the area." Welsh (1959) noted that the festoon cross-bedded units in the Hermit in southern Nevada may have accumulated on a widespread uniform floodplain, and considered the Las Vegas hinge line as a strand line during Hermit time (which he regarded as middle and late Wolfcampian time). He also stated: "In the Muddy Mountains at least restricted marine lagoons indicate the proximity of the floodplain to the marine environment." He presented an isopachous and lithofacies map illustrating his interpretation (1959), Fig. 10, p. 82). Bissell and Chilingar (1968, Fig. 8, p. 164) presented a somewhat similar, slightly modified interpretation of the lithofacies, and also showed (in Fig. 7, p. 163) the Hermit interfingering to the west (west of the Las Vegas line) into unnamed redbeds, probably of a shallow marine realm. Figure 6 of this paper suggests that the Hermit of the Bird Spring Range and adjacent areas east of the Keystone thrust thins rapidly westward and (in the Lovell Wash area of the Spring Mountains of the upper plate) constitutes the uppermost 350 ft. of an unnamed formation, there consisting of the upper red siltstone facies. So interpreted, it likely accumulated in shallow marine waters and in a realm subjected to tidal variations. Field and laboratory studies still in progress may provide more objective data than is currently available to decipher the realms of sedimentation for these Hermit-equivalent sediments of the basin.
-from Geology and Natural History of the Grand Canyon Region by The Four Corners Geological Society
The Hermit Shale, a sequence of thin-bedded, red and maroon shales, siltstones, and fine-grained mudstones, occurs beneath the Coconino Sandstone (Text-fig. 4) and weathers to a continuous prominent slope. The entire formation is characteristically deep red and is responsible for much of the red staining of lower units in the Grand Canyon. Along the river the Hermit Shale is only 200 to 300 feet thick but in the western Grand Canyon it thickens to more than 900 feet.
Thirty-five species of fossil plants have been described from the Hermit Shale within the Grand Canyon region, many of which have not been found anywhere else in the world. These plants apparently represent a savannah-type environment with long, dry seasons.
-Geology Studies Vol. 15 Part 5 1968