USGS Science⌕ Search
Home/Archive/USGS

USGS · mf2426

Geologic map of the Bonners Ferry 30' x 60' quadrangle, Idaho and Montana

Fred K. Miller·Russell F. Burmester
View original source ↗Export metadata ↓

Abstract

This data set maps and describes the geology of the Bonners Ferry 30' x 60' quadrangle, Idaho and Montana. The bedrock geology of the Bonners Ferry quadrangle consists of sedimentary, metamorphic, and granitic rocks ranging in age from Middle Proterozoic to Eocene. Bedrock units include rocks of (1) the Middle Proterozoic Belt Supergroup (2) the Middle Proterozoic Deer Trail Group, (3) the Late Proterozoic Windermere Group, (4) miogeoclinal or shelf facies lower Paleozoic rocks, and (5) Mesozoic and Tertiary granitic rocks. The Belt Supergroup, a thick sequence of argillite, siltite, quartzite, and impure carbonate rocks up to 9,000 m thick, occurs in two non-contiguous sequences in the quadrangle: (1) the Clark Fork-Eastport Sequence east of the Purcell trench and (2) the Newport Sequence in the hanging wall of the Newport Fault. Only the two lowest Belt formations of the Newport Sequence are found in the Bonners Ferry quadrangle, but these two units are part of a continuous section, which extends southwestward to the town of Newport. Belt Supergroup rocks of the Clark Fork-Eastport Sequence are separated from those of the Newport Sequence by the Newport Fault, Priest River Complex, and Purcell Trench Fault. Some formations of the Belt Supergroup show differences in thickness and (or) lithofacies from one sequence to the other that are greater than those predicted from an empirical depositional model for the distances currently separating the sequences. These anomalous thickness and facies differences suggest that there has been a net contraction along structures separating the sequences despite Eocene extension associated with emplacement of the Priest River Complex. In addition to these two Belt sequences, probable Belt rocks are present in the Priest River Complex as high metamorphic grade crystalline schist and gneiss. Northwest of the Newport Sequence of Belt Supergroup is the Deer Trail Group, a distinct Middle Proterozoic sequence of argillite, siltite, quartzite, and carbonate rocks lithostratigraphically similar to the Belt Supergroup, but separated from all Belt Supergroup rocks by the Jumpoff Joe Fault. Rocks of the Deer Trail Group are pervasively phyllitic and noticeably more deformed than rocks in the Belt Supergroup sequences. Lithostratigraphically the Deer Trail Group is equivalent to part of the upper part of the Belt Supergroup. Differences in lithostratigraphy and thickness between individual Deer Trail and Belt units and between the Deer Trail and Belt sequences as a whole indicate that they were probably much farther apart when they were deposited. The Windermere Group is a lithologically varied sequence of volcanic rocks and coarse-grained, mostly immature, clastic sedimentary rocks up to 8,000 m thick. It is characterized by extreme differences in thickness and lithofacies over short distances caused by syndepositional faulting associated with initial stages of continental rifting in the Late Proterozoic. Strata of the Windermere Group unconformably overlie only the Deer Trail Group, and are nowhere found in depositional contact with Belt Supergroup rocks. Paleozoic rocks in the Bonners Ferry quadrangle consist of a thin, fault-bounded remnant preserved within the Clark Fork-Eastport Belt Supergroup Sequence. Mesozoic granitic rocks underlie at least 50 percent of the Bonners Ferry quadrangle. They fall into two petrogenetic suites, hornblende-biotite plutons and muscovite-biotite (two-mica) plutons, most of which are Cretaceous in age. Both suites are represented in the mid-crustal Priest River Complex and in the higher level plutons that flank the complex; by far the majority of the Priest River Complex are Cretaceous, two-mica bodies. Tertiary rocks are restricted to a single small stock, numerous hypabyssal dikes that are too small to show at the scale of the map, and to cataclastic rocks related to the Newport Fault. Quaternary deposits include unconsolidated to poorl

Explore related subjects

Miscellaneous Field Studies MapReport
90° N90° S · 180° W ← longitude → 180° E
Source-reported bounding extent: 48.5° to 49° latitude; -117° to -116° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Fred K. Miller, Russell F. Burmester. 2003. Geologic map of the Bonners Ferry 30' x 60' quadrangle, Idaho and Montana. https://doi.org/10.3133/mf2426

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related USGS reports

USGS2007

Geology and Mineral Resources of the East Mojave National Scenic Area, San Bernardino County, California

From our evaluations that largely used model-based criteria, we conclude that much of the East Mojave National Scenic Area (EMNSA) contains significant indications of epigenetic mineralization of various types. Economically significant concentrations of many metals may possibly remain to be discovered in many parts of the EMNSA (see also Wetzel and others, 1992). We have discussed specific types of metallic deposits that are known to be present in the EMNSA. Some mountain ranges that have widespread occurrences are the Providence Mountains, Clark Mountain Range, Ivanpah Mountains, and New York Mountains; the area of Hackberry Mountain is included in a tract that is judged to be favorable for the discovery of epithermal, volcanic-hosted gold deposits (pl. 2). These ranges make up a broad, roughly north-south-trending region in the central part of the EMNSA. Much less endowed with known occurrences of all of the various types of deposits considered above are the Granite Mountains, the central parts of the Piute Range, the Fenner Valley area, the general area of Cima Dome, the Cima volcanic field, and areas west to Soda Lake. We have attempted to make some judgments concerning the gravel-covered areas in the EMNSA (pl. 3), including the areal extent of bedrock apparently covered only by thin veneers of gravel. But few data are available to us for the overwhelming bulk of the covered areas. The presence of any mineralization, the type of mineralization, and the extent and intensity of mineralization in the covered areas is essentially unknown. The likelihood is high, however, that those areas in the EMNSA covered only by a thin cap of gravels could host mineralization similar to that known in the adjoining mountain ranges. Most buried epigenetic-mineral deposits do not respond to standard geophysical methods, particularly at the coarse spacing of the data-collection points available for our evaluation. Restricting judgments concerning the presence of undiscovered metal resources in the EMNSA only to currently known types of deposits and to regionally representative tonnages for such deposits would undoubtedly yield small estimates for volumes of many metals that might be exploited. Metals from most newly discovered, base- and ferrous-metal deposits of the types presently known in the EMNSA probably would be insignificant from the standpoint of national needs. For example, copper from a newly discovered skarn deposit in the EMNSA would have roughly a 25 percent chance of being in excess of approximately 10,000 tonnes contained Cu, if the grade-and-tonnage distribution curves of Jones and Menzie (1986b) for copper skarns are applicable to copper skarn in the EMNSA. Most copper in the United States is produced in the Southwest from much larger open-pit operations than those associated with the typical copper skarn; the former operations exploit large-tonnage porphyry-type systems. Historically, the EMNSA has been the site of minor production of many metals from a large number of sites. Since 1985, however, a small number of sites in the EMNSA whose gold production and reserves are much greater than that of the preceding discoveries have been developed (see U.S. Bureau of Mines, 1990a). Nonetheless, widespread distribution of numerous types of deposits (including copper skarn, lead-zinc skarn, tin-tungsten skarn, polymetallic vein, gold-silver quartz-pyrite vein, low-fluorine porphyry molybdenum, gold breccia pipe, and volcanic-hosted gold) that are petrogenetically associated with igneous rock in many parts of the EMNSA is indicative of a metallogenic environment that may be the site of future discoveries of mineral-deposit types that are not now recognized by the exploration community. The science, art, and, yes, even luck of exploration procedures continually evolve, and this evolution is one of the most important aspects of currently employed methods of exploration (Bailly, 1981; Hutchinson and Grauch, 1991).

Miscellaneous Field Studies Map↗
USGS2005

Geologic map of the Pinedale quadrangle, McKinley County, New Mexico

The 1:24,000-scale geologic map of the Pinedale 7.5' quadrangle lies in the western part of the Grants uranium mineral belt, which was mapped and studied under a cooperative agreement between the USGS and the U.S. Department of Energy. A spectacular panoramic view of the southern half of the Pinedale quadrangle is obtained looking northward from Interstate Highway 40, particularly from the New Mexico State travelers' rest stop near the Shell Oil Company's Ciniza Refinery, 28.5 kilometers (17.8 miles) east of Gallup. A west-trending escarpment, 200 meters high, of massive red sandstone, rises above a broad valley, its continuity broken only by a few deep and picturesque canyons in the western half of the quadrangle. The escarpment is formed by the eolian Entrada Sandstone of Late Jurassic age. The Entrada unconformably overlies the Chinle Formation of Late Triassic age, which occupies the valley below. The Chinle Formation consists of cherty mottled limestone and mudstone of the Owl Rock Member and underlying, poorly consolidated, red to purple fluvial siltstone, mudstone, and sandstone beds of the Petrified Forest Member. The pinyon- and juniper-covered bench that tops the escarpment is underlain by the Todilto Limestone. A quarry operation, located just north of the Indian community of Iyanbito in the southwestern part of the quadrangle, produces crushed limestone aggregate for highway construction and railroad ballast. Beyond the escarpment to the north and rising prominently above it, is the northwest-trending Fallen Timber Ridge. Near the west side of the quadrangle lie the peaks of Midget Mesa, and Mesa Butte, the latter of which has the highest altitude in the area at 2,635 meters (8,030 feet) above sea level. The prominences are capped by buff-colored resistant beds of the Dakota Sandstone of Late Cretaceous age, containing some interbedded coal. These beds unconformably overlie the uranium-bearing Morrison Formation, which consists of red, green, and gray shale, orange feldspathic sandstone, and green tuffaceous mudstone, deposited in ancient lakes, alluvial fans, and rivers during the Upper Jurassic Period. Thick, crossbedded, white beds of the Cow Springs Sandstone, derived from ancient windblown desert sands, underlie the Morrison. In the northern part of the quadrangle, the Dakota Sandstone is overlain by gray Mancos Shale and yellowish-gray Two Wells and Gallup Sandstones that were deposited in Late Cretaceous seas. Unconsolidated deposits of Quaternary age are found throughout the quadrangle in talus, slope wash, fans, valley alluviums, pediments, and as windblown sands in dunes and blanket deposits. The strata conform to the regional dip of about three degrees to north, except where they are down-folded some 200 meters along the Pinedale monocline, whose limbs follow a sinuous west-northwest trend across the northern half of the quadrangle. The monocline is beautifully exposed at Pinedale, where it shows as much as 20 degrees dip on the pine-studded bare rock slope of the Two Wells Sandstone. A north-plunging broad anticline and accompanying syncline is developed in the east-central part of the quadrangle but dies out against the monocline. A minor fault, with barely 3 meters of vertical displacement, extends several kilometers westward across the Todilto Limestone bench. A large landslide mass, 1.5 kilometers long by 0.7 kilometers wide occurs in the Mancos Shale west of Pinedale. Exploration drilling for uranium in the Morrison Formation has been extensive in the quadrangle, particularly north of the monocline, which adjoins the Old Church Rock mine area, west northwest of the quadrangle.

Miscellaneous Field Studies Map↗