Wood Canyon Research Articles

Paleomagnetism of Lower and Middle Cambrian sedimentary rocks from the Desert Range, Nevada

Over 500 oriented samples were collected from a homoclinal sequence of Lower and Middle Cambrian terrigenous and carbonate miogeoclinal strata in the Desert Range, Nevada. Extensive thermal demagnetization was successful in isolating similar characteristic magnetization directions in red‐purple mudstones of the Wood Canyon Formation (Lower(?) and Lower Cambrian) and in gray limestones of the Carrara and Bonanza King Formations (Lower and Middle Cambrian). Lithologic and magnetic evidence suggest that these magnetizations were acquired penecontemporaneously with deposition. The similarity of the characteristic magnetization directions in these strata implies that little apparent polar wander occurred with respect to North America from early Early through middle Middle Cambrian time. The divergence of these directions from those from the partly coeval Tapeats Sandstone of the Colorado Plateau probably resulted from a net 36° clockwise rotation of the Desert Range section about a vertical axis. This rotation is probably due to mid‐Tertiary oroflexural bending but may in part have been caused by Mesozoic thrusting. The polarity of the geomagnetic field in early Middle Cambrian time appears to have been continuously reversed. Stratigraphic intervals of mixed polarity, possibly correlative with those found in the Tapeats, may be present in the Lower Cambrian Zabriskie Quartzite.

Petrology of Late Precambrian-Cambrian Quartzose Sandstones in the Eastern Mojave Desert, Southeastern California

ABSTRACT Petrographic and radiographic analyses were conducted on oriented samples of Late Precambrian-Cambrian quartzose sandstones collected from five cratonal and five miogeoclinal stratigraphic sections in the eastern Mojave Desert, southeastern California. Twelve petrographic variables were measured in each of 494 samples. Cratonal sandstones are dominantly subarkose, whereas miogeoclinal sandstones are subarkose and quartzarenite in almost equal proportions. Sediments were derived chiefly from granitic rocks, gneiss, and schist as well as older sedimentary and metasedimentary rocks. The cratonal source areas were to the east and southeast. Samples collected from six northern sections within the Cordilleran frontal thrust belt have a higher content of undulatory quartz and silica cement and are partially recrystallized when compared with samples from four southern sections. Polynomial time-trend analysis showed considerable variation in mineral composition with thickness at each stratigraphic section. Areal variation of total quartz was estimated from analysis of variance models. The difference was not highly significant for the Stirling Quartzite. Depositional history was inferred for each formation on the basis of petrography, clasticity and sedimentary structures. The Johnnie Formation fines upward, which suggests a marine transgression or change from open to partially restricted shelf environments. The Stirling Quartzite coarsens upward and consists largely of prograding mature shelf sands or deposits of migrating bars and barrier beaches. The Wood Canyon Formation is dominantly subtidal with local evidence for intertidal deposition.

Extension of the Cordilleran Miogeosynclinal Belt to the San Andreas Fault, Southern California

Correlations of marine sedimentary rocks in the San Bernardino Mountains and western Mojave Desert area with known uppermost Precambrian and some Paleozoic rocks of the southern Great Basin suggest that a nearly complete succession of Cordilleran miogeosynclinal rocks extends into southern California. Pre-Mesozoic rocks in the San Bernardino Mountains consist of (1) gneiss and schist of Precambrian age (in part older than 1,750 m.y.); (2) the Saragossa Quartzite, here considered to be latest Precambrian and Early Cambrian in age; and (3) the Furnace Limestone, the upper part of which is locally dated by megafossils as Mississippian and possibly Pennsylvanian or Permian but considered here to contain strata ranging in age from Early Cambrian to Permian(?). The Saragossa Quartzite contains distinct units that can be lithologically correlated confidently with parts of the uppermost Precambrian and Lower Cambrian sequence containing the Johnnie, Stirling, Wood Canyon, and Zabriskie Formations of the eastern Mojave Desert and the southern Great Basin. Some rock units on Quartzite Mountain in the western Mojave Desert are lithologically correlated with the uppermost Precambrian and Cambrian Wood Canyon, Zabriskie, Carrara, and Bonanza King Formations of the eastern Mojave Desert and southern Great Basin. The Cordilleran miogeosynclinal belt is obliquely truncated by the San Andreas fault in southern California; a displaced segment may occur in the Salinian block 450 km to the northwest. Cordilleran miogeosynclinal rocks also occur in northwestern Mexico east of the San Andreas fault, indicating a major change in trend of the geosyncline between the Great Basin and Mexico.

Late Precambrian-Early Cambrian Stratigraphy of Kelso Mountains, Eastern Mojave Desert, California: ABSTRACT

A detailed study has been made of several outcrops of late Precambrian-Early Cambrian strata in the southern Kelso Mountains. These strata, which are part of the predominantly detrital basal sequence of the Cordilleran miogeocline, previously have been described only in reconnaissance. In the Kelso Mountains, these strata have been assigned to 5 regionally recognized formations. The late Precambrian Johnnie Formation, which lies unconformably on metamorphic basement, displays rapid lateral changes in lithology and thickness, perhaps due in part to infilling of uneven basement topography. Of 4 sections of Johnnie exposed, 3 are similar, consisting of 91-141 ft of quartzite and dolomite. Conformably overlying the Johnnie Formation are the late Precambrian Stirling Quartzite (186 ft thick, only the uppermost regional member is present), the late Precambrian-Early Cambrian Wood Canyon Formation (712 ft thick), the Early Cambrian Zabriskie Quartzite (75 ft thick), and the Early Cambrian lower part of the Carrara Formation (70 ft thick). Comparison of these strata with equivalent miogeoclinal strata in the Providence Mountains 8 mi southeast and with Early Cambrian cratonic strata in the Marble Mountains 30 mi south shows that the northeast-trending craton-miogeocline boundary was not an abrupt break (an interpretation based on comparison in Nevada and Utah of thick allochthonous miogeoclinal strata with autochthonous cratonic strata), but rather a relatively broad transition zone of gradual thickening of strata from southeast to northwest. End_of_Article - Last_Page 776------------

Strata of Late Precambrian-Cambrian Age, Death Valley Region, California-Nevada

The Noonday Dolomite, Johnnie Formation, Stirling Quartzite, Wood Canyon Formation, and Zabriskie Quartzite, which seem best assigned to the late Precambrian-Cambrian interval, are a conformable and predominantly detrital part of the stratigraphic record of the Death Valley region. They can be traced from type localities in the Spring Mountains and in the well-known section in the Nopah Range southwestward to the Salt Spring Hills and Silurian Hills in southern Death Valley and southeastward to the Kingston Range-Winters Pass area. Satisfactory correlation of these widespread formations is facilitated by (1) regional persistence of most of the members as originally recognized in the Nopah Range, (2) the distinctive lithologic character of the Noonday Dolomite, and (3) the presence of two marker units--an oolite and a volcanic ash(?)--high in the Johnnie Formation. Isopachous contouring of the stratigraphic interval from the top of the Zibriskie Quartzite to the base of the Noonday Dolomite appears to outline a late Precambrian-Cambrian marine trough. The major axis of this trough strikes north-northwest and is approximately coincident with the present Amargosa Valley and southern Death Valley. Along this axis, the combined thickness of these strata or their apparent equivalents decreases progressively from nearly 12,000 feet in the Funeral Mountains to only a few hundred feet in the Marble Mountains 160 miles toward the south. The isopachous lines drawn near the southeastward bend in the Garlock fault zone are nearly parallel with this major break, and the projected zero contour is about 10 miles southwest of it. This pattern strongly suggests that the structural element south and southwest of the Garlock fault, generally referred to as the Mojave block, existed as a topographic high in late Precambrian-Cambrian time.

Precambrian and Paleozoic Stratigraphy of Specter Range Quadrangle, Nye County, Nevada

More than 22,000 feet of Precambrian to Upper Devonian rocks crop out in the Specter Range Quadrangle. These rocks have been divided into fourteen formations; from the oldest to the youngest they are the Johnnie Formation, Stirling Quartzite, Wood Canyon Formation, Carrara Formation, Bonanza King Formation, Dunderberg Shale, Nopah Formation (restricted), Lower Pogonip Group undifferentiated (which includes the Goodwin Limestone and Ninemile Formation), Antelope Valley Limestone, Eureka Quartzite, Ely Springs Dolomite, Undifferentiated Silurian rocks, Nevada Formation, and Devils Gate Limestone. The four oldest formations, Precambrian to lower Middle Cambrian, are composed of clastic rocks; quartzite, siltstone, and shale with thin beds of limestone and dolomite. From lowe Middle Cambrian through Upper Devonian, the rocks are mainly limestone and dolomite with thin beds of quartzite and quartz sandstone. The formational names recognized during this study are probably applicable over a wide area in south-central Nevada where in large part the stratigraphy is poorly known. Four formations are of particular interest. The Antelope Valley Limestone is mapped for the first time in this part of Nevada and its lithologic and time equivalence with the type section is demonstrated. The Goodwin Limestone and Ninemile Formation are also tentatively identified for the first time. The age of the Nevada Formation has been established as Lower Devonian (Spirifer kobehana Zone) and Middle Devonian (Stringocephalus Zone); equivalent to the rocks of the type section in the Eureka district.

Geology of Central Panamint Range: ABSTRACT

The area is west of Death Valley, between Stovepipe Wells and Wildrose Canyon, a distance of 25 miles. Archean gneiss, exposed in two small areas, one at Wildrose Station, one on south flank of Tucki Mountain, is overlain by a 2,000-foot series of meta-graywackers and meta-conglomerates best exposed in Wildrose Canyon (Surprise formation? Upper Algonkian), and widely exposed 3,000 or more feet of younger series of variably metamorphosed graywackle, shale, conglomerate, dolomite, and gypsum (Telescope group? Upper Algonkian). East-dipping Paleozoic strata make up the east flank of the range: Lower Cambrian, Noonday dolomite (200-1,000 feet), Johnnie formation (2,500), Sterling quartzite (1,500), Wood Canyon formation (2,900); Middle Cambrian, Cadiz formation (700), Bonanza King formation (1,250), Racetrack dolomite (1,950); Upper Cambrian, Nopah formation (1,700); Lower Ordovician, Pogonip formation (1,950); Middle Ordovician, Eureka quartzite (400); Upper Ordovician, Ely Springs dolomite (1,300); Silurian (?), Hidden Valley dolomite (?) (700); Devonian, Lost Burro formation (l,500). Post-Devonian strata are not yet mapped. Total thickness, Cambrian through Devonian (19,550), of which 13,650 are Cambrian. A 12-mile-long quartz monzonite intrusive of presumed Nevadan age near the ccenter of the range appears laccolithic. Structural features include the east-dipping monocline of Paleozoic sediments on the east flank of the range, two northwest-trending anticlines in Algonkian strata on the west and south flanks of Tucki Mountain, and widely prevalent flat to low angle faulting. End_of_Article - Last_Page 140------------