Paleozic Stratigraphy of the James Peak Quadrangle, Utah

• Main Author: King, Harley D.
• Format: Others
• Published: DigitalCommons@USU 1965
• Subjects: Geology
• Online Access: https://digitalcommons.usu.edu/etd/6652; https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=7708&context=etd

General Statement The James Peak quadrangle is a topographic map unit of the Geological Survey of the U. S. Department of Interior (Plate 1). It covers 7 1/2 minutes of latitude and longitude at a scale of 1:24, 000 or 1 inch to 2, 000 feet. It is bounded by lat 41°22'30" N. and lat 41°30' N. and long 111°45' W. and long 111 °52 '30" W The quadrangle includes 56 square miles and has maximum relief of about 4, 300 feet. The James Peak quadrangle is located in northern Utah between the Wasatch Range on the west and the Bear River Range on the east (Figure 1). The eastern part includes the western flank of the Bear River Range. James Peak, 9, 500 feet in elevation, is in the southeastern part of the quadrangle and forms an imposing landmark as seen from Cache Valley to the north and Ogden Valley to the south. The area of the James Peak quadrangle is represented on various generalized geologic maps (Hardy and Williams, 1953; Stokes, 1963); how­ever, no concerted attempt has been made to study the Paleozoic stratigraphy of the area. Such an investigation is basic to an understanding of the geologic structure of northern central Utah and might also help resolve numerous stratigraphic problems of the region. The purpose of this investigation is to determine the lithology and thickness of the Paleozoic stratigraphic units present within the James Peak quadrangle. Previous investigations A preliminary map constructed by Ezell (1953, plate 9) includes the northwestern corner of the quadrangle but unfortunately leaves an internal area unmapped. The entire quadrangle was represented on a regional geo­logic map of northern Utah prepared by Hardy and Williams (1953). Certain aspects of the structure have been discussed briefly by Hardy (1957). None of these studies are based on an adequate analysis of the Paleozoic stratigraphy. The stratigraphy of certain surrounding areas is known in considerable detail. Williams (1948, 1958) studied the Paleozoic rocks of the Logan quad­rangle, Utah-Idaho, to the north and also mapped the quadrangle at a scale of 1:125, 000. The Paradise quadrangle, within the Logan quadrangle and just north of the James Peak quadrangle, has recently been mapped by Mullens and Izett (1964). The higher parts of the Wasatch Range to the west of the James Peak quadrangle have been described in general terms by Blackwelder (1910) and Eardley (1944). Finally, the quadrangle immediately east of the James Peak quadrangle is the subject of a thesis by Hafen (1961). Present understanding of regional Paleozoic stratigraphy is based on a great many detailed studies of more distant areas except for Blacksmith Fork Canyon which is a classic area of Cambrian stratigraphy. This locality is within the Logan quadrangle. Reference is made to many of these reports in the discussion of individual formations of the James Peak quadrangle. Geologic features Stratigraphic units of Paleozoic age are known largely from outcrops in the central and northwestern parts of the James Peak quadrangle (Plate 1). A succession, which dips generally northward, is found on both the eastern and western sides of the South Fork of Little Bear River (Table 1). It extends from Middle Mountain northward nearly to the margin of the quadrangle and from Public Grove Hollow northward to the lower part of Fourmile Canyon and to the northwestern corner of the quadrangle. A narrow area of Paleozoic rocks, in general poorly exposed and structurally complex, is present along the eastern margin of the quadrangle. James Peak and the southwestern part of the quadrangle are underlain by quartzites of presumed Precambrian age. The James Peak quadrangle is divided into three blocks by two north­south faults or fault zones: (1) western block, (2) central block, and (3) eastern block. James Peak is in the southern part of the central block; Middle Mountain is in the middle part of this same block near the western side. A fault or fault zone extends north-south along both the western side of James Peak and Middle Mountain. The eastern block forms the flank of the Bear River Range with McKenzie Mountain near the northern end. The front of the Bear River Range is distinctly limited by a fault or fault zone which extends southward between the main part of the range and James Peak to the west. Precambrian rocks, striking about east-west and dipping northward, are found in the southern part of the western block. The Prospect Mountain quartzite of Cambrian age, with essentially the same strike and dip as the Precambrian units, extends across the block from west to east; however, it is covered at the eastern side by the Salt Lake formation of Tertiary age. The Prospect Mountain is followed in normal stratigraphic succession by the Pioche(?) formation and younger Cambrian units. These are limited by an east-west fault, in Dips Hollow, which probably extends completely across the block. The Prospect Mountain is at the surface again north of this fault at the eastern side of the block. The Prospect Mountain, north of the fault, is over­lain by the Pioche(?) formation and 16 younger units of Paleozoic age, The northern part of the block, however, is largely covered by the Salt Lake formation. The southern part of the central block, James Peak, is formed of Precambrian rock but with north-south strike and east dip. A broad valley which extends across the block just north of James Peak and northward to the edge of the quadrangle is underlain by the Salt Lake formation which certainly covers various units of Paleozoic age. Middle Mountain, therefore, is isolated by a cover of the Salt Lake formation, except at its western side where it is bounded by a north-south fault separating the central and western blocks. The Prospect Mountain quartzite crops out at the southern end of Middle Mountain and is overlain in turn northward by 11 formations of Paleozoic age. The youngest unit, at the northern end, is the Laketown dolo­stone of Silurian age. The rocks of Middle Mountain strike west-northwest and dip northward. The part of the eastern block, south of Davenport Creek and east of James Peak, is not fully understood. Here unidentified Cambrian units, Laketown dolostone, and Garden City formation are separated by several more or less vertical north-south faults. North of Davenport Creek is a small syncline, with north-south axis, in the Garden City formation of Ordovician age. The Garden City is followed northward by the Swan Peak formation, Lodgepole limestone, and finally, making the higher part of McKenzie Moun­tain, the Great Blue limestone. These units, for the most part, strike north­south and dip gently westward. Field Work The major part of the field work was done in a two-month period during the summer of 1962. Additional time was spent in the field during the summer of 1963. The stratigraphic sections were measured with a 50-foot steel tape. A Brunton compass was used to determine dip, slope, and azimuth. Thick­nesses were subsequently computed. The terminology for bedding, used in this report, is that of McKee and Weir (1953, p. 381-389) as modified by Ingram (1954, p. 938). The Wentworth grade scale was used to describe elastic rocks. It was also used, as adapted by Payne (1942, p. 1, 706), for the crystalline carbonate rocks. Color was determined with reference to the Rock-Color Chart (Goddard, 1951).