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 poorly consolidated glacial, alluvial, glacial-lacustrine, and landslide units.
Created using Environmental Systems Research Institute's ARC/INFO software, the data base consists of the following items: (1) a map coverage containing geologic faults, contacts and units, (2) a point coverage containing site-specific geologic structural data, (3) a line and point coverage containing structural data (fold axes) along with geologic line ornamentation, (4) a coverage containing cartographic elements (annotation), (5) four coverages derived from 1:100,000 Digital Line Graphs (DLG); topography, hydrography, and cultural data contained in two transportation coverages, road and rail, and (6) attribute and lookup tables for geologic units (polygons), contacts and faults (arcs), and site-specific data (points). In addition, the data set includes the following graphic and text products: (1) A PostScript graphic plot-file containing the geologic map, topography, cultural data, a list of Map Units (DMU), modal diagrams for granitic rocks, an index map, a regional geologic and structure map, and a key for point and line symbols; (2) PDF files of the Readme, Description of Map Units (DMU) including a discussion of the geologic framework, (3) map-sheet and (4) this metadata file.
The geologic map database contains original U.S. Geological Survey data generated by detailed field observation and by interpretation of aerial photographs. The map was compiled from geologic maps of eight 1:48,000 15' quadrangle blocks, each of which was made by mosaicking and reducing the four constituent 7.5' quadrangles. These 15' quadrangle blocks were mapped chiefly at 1:24,000 scale, but the detail of the mapping was governed by the intention that it was to be compiled at 1:48,000 scale. The compilation at 1:100,000 scale entailed necessary simplification in some areas and combining of some geologic units. Overall, however, despite a greater than two times reduction in scale, most geologic detail found on the 1:48,000 maps is retained on the 1:100,000 map. Geologic contacts across boundaries of the eight constituent quadrangles required minor adjustments, but none significant at the final 1:100,000 scale.
The geologic map was compiled on a base-stable cronoflex copy of the Bonners Ferry 30' X 60' topographic base and then scribed. The scribe guide was used to make a 0.007 mil-thick blackline clear-film, which was scanned at 1200 DPI by Optronics Specialty Company, Northridge, California. This image was converted to vector and polygon GIS layers and minimally attributed by Optronics Specialty Company. Minor hand-digitized additions were made at the USGS. Lines, points, and polygons were subsequently edited at the USGS by using standard ARC/INFO commands. Digitizing and editing artifacts significant enough to display at a scale of 1:100,000 were corrected. Within the database, geologic contacts are represented as lines (arcs), geologic units as polygons, and site-specific data as points. Polygon, arc, and point attribute tables (.pat, .aat, and .pat, respectively) uniquely identify each geologic datum.
The digital geologic map database for the Bonners Ferry 30' X 60' quadrangle has been created as a general-purpose data set that is applicable to other land-related investigations in the earth and biological sciences. For example, it can be used for mineral resource evaluation studies, animal and plant habitat studies, and soil studies in the Idaho Panhandle National Forest. The database is not suitable for site-specific geologic evaluations.
Use of this digital geologic-map database should not violate the spatial resolution of the data. Although the digital form of the data removes the constraint imposed by the scale of a paper map, the detail and accuracy inherent in map scale are also present in the digital data. The fact that this database was compiled and edited at a scale of 1:100,000 means that higher resolution information may not have been uniformly retained in the dataset. Plotting at scales larger than 1:100,000 will not yield greater real detail, although it may reveal fine-scale irregularities below the intended resolution of the database. Similarly, although higher resolution data is incorporated in most of the map, the resolution of the combined output will be limited by the lower resolution.
Geologic mapping and digital preparation of this report were sponsored jointly by (1) the National Cooperative Geologic Mapping Program of the U.S. Geological Survey, (2) the Southern California Areal Mapping Project (SCAMP), and (3) the Mineral Resources Program of the U.S. Geological Survey.
Nation-wide geologic-map accuracy standards have not been developed and adopted by the U.S. Geological Survey and other earth-science entities. Until such standards are adopted, SCAMP-related projects have developed internal map-accuracy standards for 1:100,000-scale geologic maps produced under the projects.
Geologic lines and points on 1:100,000 scale geologic maps are judged to meet SCAMP's internal map-accuracy standards if they are located to within +/-50 meters, relative to topographic or cultural features on the base map. On any derivative geologic-map plot, line data for faults that are judged to meet the SCAMP internal map-accuracy standard are denoted by solid lines; line data that may not meet the SCAMP internal map-accuracy standard are denoted by dashed or dotted lines. All non-fault contacts are represented by solid lines. Because many of the contacts in the Priest River Complex are highly gradational, they may not be located to within +/-50m. There is no cartographic device for denoting the map-accuracy for geologic-point data (eg. symbols representing bedding, foliation, lineations, etc.).
The areal extent of the map is represented digitally by an appropriately projected (UTM projection), mathematically generated box. Consequently, polygons intersecting the lines that comprise the map boundary are closed by that boundary. Polygons internal to the map boundary are completely enclosed by line segments which are themselves a set of sequentially numbered coordinate pairs. Point data are represented by coordinate pairs.
Initial transformation data for the Bonners Ferry quadrangle are as follows:
Scale (X,Y) = (2540.402,2539.610) Skew (degrees) = (-0.010) Rotation (degrees) = (0.363) Translation = (498231.996,369742.063) RMS Error (input,output) = (0.004,10.516) Affine X = Ax + By + C Y = Dx + Ey + F A = 2540.351 B = -16.554 C = 498231.996 D = 16.094 E = 2539.557 F = 369742.063
Matti, J.C., Miller, F.K., Powell, R.E., Kennedy, S.A., Bunyapanasarn, T.P., Koukladas, Catherine, Hauser, R.M., and Cossette, P.M., 1997b, Geologic-point attributes for digital geologic-map databases produced by the Southern California Areal Mapping Project (SCAMP), Version 1.0: U.S.Geological Survey Open-File Report 97-859
Matti, J.C., Miller, F.K., Powell, R.E., Kennedy, S.A., and Cossette, P.M., 1997c, Geologic-polygon attributes for digital geologic-map databases produced by the Southern California Areal Mapping Project (SCAMP), Version 1.0: U.S.Geological Survey Open-File Report 97-860
Matti, J.C., Powell, R.E., Miller, F.K., Kennedy, S.A., Ruppert, K.R., Morton, G.L., and Cossette, P.M., 1997a, Geologic-line attributes for digital geologic-map databases produced by the Southern California Areal Mapping Project (SCAMP), Version 1.0: U.S.Geological Survey Open-File Report 97-861
In no event shall the USGS have any liability whatsoever for payment of any consequential, incidental, indirect, special, or tort damages of any kind, including, but not limited to, any loss of profits arising out of use of or reliance on the geographic data or arising out of the delivery, installation, operation, or support by USGS.
This digital, geologic map database of the Bonners Ferry 30' x 60' quadrangle, 1:100,000 map-scale, and any derivative maps thereof, is not meant to be used or displayed at any scale larger than 1:100,000 (e.g., 1:24,000).