Metadata:
Identification_Information:
Citation:
Citation_Information:
Originator: Skipp, Betty
Originator: Lageson, D.R.
Originator: McMannis, W.J.
Publication_Date: 1998
Title: Digital files to accompany I-2634, "Geologic map of the Sedan
quadrangle, Gallatin and Park Counties, Montana"
Geospatial_Data_Presentation_Form: Map
Publication_Information:
Publication_Place: Denver, CO
Publisher: U.S. Geological Survey
Online_Linkage:
Larger_Work_Citation:
Citation_Information:
Originator: Skipp, Betty
Originator: Lageson, D.R.
Originator: McMannis, W.J.
Publication_Date: In press
Title: Geologic map of the Sedan quadrangle, Gallatin and Park
Counties, Montana
Geospatial_Data_Presentation_Form: Map
Series_Information:
Series_Name: U.S. Geological Survey Geologic Investigations
Series
Issue_Identification: I-2634
Publication_Information:
Publication_Place: Denver, CO
Publisher: U.S. Geological Survey
Other_Citation_Details: The printed version of I-2634 is in
press; it will include supplemental figures, three cross sections, and
interpretive text.
Description:
Abstract:
This quadrangle lies 6.4 km (4 mi) northeast of Bozeman, Mont., in
southwestern Montana. Metamorphic, sedimentary, and volcanic rocks of
Precambrian to Tertiary age are exposed in the Bridger Range and southwestern
margin of the Crazy Mountains Basin in a crustal cross section and a structural
triangle zone. Surface geology records Precambrian extension, Late Paleocene
east-vergent contraction, including backthrusts, and Holocene basin-range
extension.
Purpose:
The geology of the Sedan quadrangle was mapped as part of a regional
study of the western Crazy Mountains Basin. It was digitized for ease of
production of the printed version and for greater distribution for analytical
use.
Supplemental_Information:
A preliminary map was published as a U.S. Geological Survey Open-File Report
in 1971. The geologic data was interpreted 1965-93, the interpretation being
informed by data from two wells in addition to the original field work. The
printed version of I-2634 is in press; it will include supplemental figures,
three cross sections, and interpretive text.
Users should be aware that of the many faults mapped, the only active one is
the range front fault on the west side of the Bridger Range.
Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 1965
Ending_Date: 1971
Currentness_Reference: The geology of the quadrangle was mapped 1965-
71.
Status:
Progress: In work
Maintenance_and_Update_Frequency: As needed
Spatial_Domain:
Bounding_Coordinates:
West_Bounding_Coordinate: -111.0
East_Bounding_Coordinate: -110.75
North_Bounding_Coordinate: 46.0
South_Bounding_Coordinate: 45.75
Keywords:
Theme:
Theme_Keyword_Thesaurus: American Geological Institute Glossary of
Geology
Theme_Keyword: Geology
Theme_Keyword: Structure
Theme_Keyword: Geologic map
Theme_Keyword: Bedrock
Theme_Keyword: Surficial geology
Theme_Keyword: Metamorphic rocks
Theme_Keyword: Sedimentary rocks
Theme_Keyword: Volcanic rocks
Place:
Place_Keyword_Thesaurus: U.S. Board on Geographic Names (BGN)
Geographic Names Information System (GNIS)
Place_Keyword: United States
Place_Keyword: Montana
Place_Keyword: Gallatin County, Montana
Place_Keyword: Park County, Montana
Place_Keyword: Bridger Range
Place_Keyword: Crazy Mountains Basin
Stratum:
Stratum_Keyword_Thesaurus: North American Stratigraphic Code
Stratum_Keyword: Fort Union Formation
Stratum_Keyword: Livingston Group
Stratum_Keyword: Hoppers Formation
Stratum_Keyword: Billman Creek Formation
Stratum_Keyword: Sedan Formation
Stratum_Keyword: Eagle Sandstone
Stratum_Keyword: Telegraph Creek Formation
Stratum_Keyword: Cody Shale
Stratum_Keyword: Frontier Formation
Stratum_Keyword: Mowry Shale
Stratum_Keyword: Thermopolis Shale
Stratum_Keyword: Kootenai Formation
Stratum_Keyword: Muddy Sandstone
Stratum_Keyword: Skull Creek Shale
Stratum_Keyword: Fall River Sandstone
Stratum_Keyword: Morrison Formation
Stratum_Keyword: Ellis Group
Stratum_Keyword: Phosphoria Formation
Stratum_Keyword: Quadrant Formation
Stratum_Keyword: Amsden Group
Stratum_Keyword: Snowcrest Range Group
Stratum_Keyword: Madison Group
Stratum_Keyword: Mission Canyon Limestone
Stratum_Keyword: Lodgepole Limestone
Stratum_Keyword: Three Forks Formation
Stratum_Keyword: Jefferson Dolomite
Stratum_Keyword: Maywood Formation
Stratum_Keyword: Snowy Range Formation
Stratum_Keyword: Pilgrim Limestone
Stratum_Keyword: Park Shale
Stratum_Keyword: Meagher Limestone
Stratum_Keyword: Wolsey Shale
Stratum_Keyword: Flathead Sandstone
Stratum_Keyword: Belt Supergroup
Stratum_Keyword: La Hood Formation
Temporal:
Temporal_Keyword_Thesaurus: North American Stratigraphic Code
Temporal_Keyword: Pleistocene
Temporal_Keyword: Quaternary
Temporal_Keyword: Tertiary
Temporal_Keyword: Cretaceous
Temporal_Keyword: Jurassic
Temporal_Keyword: Mesozoic
Temporal_Keyword: Permian
Temporal_Keyword: Pennsylvanian
Temporal_Keyword: Mississippian
Temporal_Keyword: Devonian
Temporal_Keyword: Ordovician
Temporal_Keyword: Cambrian
Temporal_Keyword: Paleozoic
Temporal_Keyword: Precambrian
Temporal_Keyword: Proterozoic
Temporal_Keyword: Archean
Access_Constraints: None
Use_Constraints: None
Point_of_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Skipp, Betty
Contact_Organization: U.S. Geological Survey
Contact_Address:
Address_Type: mailing address
Address: U.S. Geological Survey, MS964, Box 25046, Denver Federal
Center
City: Lakewood
State_or_Province: CO
Postal_Code: 80225
Country: USA
Contact_Voice_Telephone: (303) 236-1242
Contact_Electronic_Mail_Address: bskipp@usgs.gov
Data_Set_Credit: The geology of the Sedan quadrangle was mapped by Betty
Skipp, D.R. Lageson, and W.J. McMannis; the map was converted to digital form by
Techni Graphic Systems, Inc., of Fort Collins, CO, under contract with the U.S.
Geological Survey, and by Nancy Shock, U.S. Geological Survey. The map was
edited and proofread by Diane E. Lane, U.S. Geological Survey.
Native_Data_Set_Environment: ARC/INFO v. 7.2.1, Solaris 2.6.
Data_Quality_Information:
Attribute_Accuracy:
Attribute_Accuracy_Report: Strike and dip of bedding surfaces,
eutaxitic layering in ash-flow tuffs, and layering in metamorphic rocks was
measured and recorded to the nearest degree in the Bridger Range and to the
nearest 5 degrees elsewhere in the map area.
Logical_Consistency_Report: The density of observations was lower in
parts of the Fort Union Formation as evidenced by the density of attitude
symbols on the map.
Completeness_Report: data set is complete
Positional_Accuracy:
Horizontal_Positional_Accuracy:
Horizontal_Positional_Accuracy_Report: The accuracy of location of
polygons, lines, and points is consistent with the mapping scale of 1:48,000.
Lineage:
Source_Information:
Source_Citation:
Citation_Information:
Originator: Skipp, Betty
Originator: Lageson, D.R.
Originator: McMannis, W.J.
Publication_Date: 1998
Title: Draft compilation of geologic map of the Sedan
quadrangle, Gallatin and Park Counties, Montana
Geospatial_Data_Presentation_Form: Map
Source_Scale_Denominator: 48000
Type_of_Source_Media: stable-base material
Source_Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 1965
Ending_Date: 1971
Source_Currentness_Reference: The geology of the quadrangle was
mapped 1965-71.
Process_Step:
Process_Description: Digitizing contractor scanned source stable-
base material, vectorized scan, attributed files from author drafting and
annotations, and produced check plots and coverages.
Process_Date:199807
Process_Step:
Process_Description: First author and map editor proofread check
plots, and digital map specialist reviewed digital files.
Process_Date:199808
Process_Step:
Process_Description: Digitizing contractor corrected attributing as
needed and produced new check plots.
Process_Date:199810
Process_Step:
Process_Description: Digital map specialist and editor proofread new
check plots and reviewed digital files, making final corrections as needed,
prepared metadata, and placed digital files on USGS ftp server.
Process_Date:199811
Spatial_Data_Organization_Information:
Direct_Spatial_Reference_Method: Vector
Spatial_Reference_Information:
Horizontal_Coordinate_System_Definition:
Planar:
Grid_Coordinate_System:
Grid_Coordinate_System_Name:
Universal_Transverse_Mercator:
UTM_Zone_Number: 12
Transverse_Mercator:
Scale_Factor_at_Central_Meridian: 0.9996
Longitude_of_Central_Meridian: -111
Latitude_of_Projection_Origin: 40
False_Easting: 0
False_Northing: 0
Entity_and_Attribute_Information:
Overview_Description:
Entity_and_Attribute_Overview:
The dataset for the Sedan quadrangle consists of 10 coverages. The three
coverages pnt_graphic, stpnt_graphic, and dvalues are not 'true' ARC/INFO
coverages. They are graphic representations of symbols used on the geologic
map: pnt_sym = pnt_graphic, stru_pnt and geo_pnt = stpnt_graphic, and dvalues =
annotation for stru_pnt and geo_pnt.
geo_net
geo_pnt
stru_net
stru_pnt
data_net
data_pnt
pnt_sym
pnt_graphic
stpnt_graphic
dvalues
The dataset also includes two plot files called sedangeology.gra and
sedangeology.ps.
Entity_and_Attribute_Detail_Citation:
The geo_net coverage includes polygons that are map units and arcs that are
contacts, veins, and dikes. The coverage consists of the following items:
GEOCODE
NAM
ACC
Items in the geo_net coverage are defined as follows:
GEOCODE refers to the type of geologic feature. The value for GEOCODE in the
geo_net coverage is one of the following: "Map unit," "Calcite vein," and
"Waulsortian bioherm." To interpret the map unit symbols, refer to the
explanation of unit symbols as coded by NAM.
NAM refers to the map unit name and associated symbol (e.g., Qal, Td, KJr) as
used in the following explanation (NOTE: The codes and items in the other
coverages are explained in the sections following the description of map units
and references cited):
SURFICIAL DEPOSITS
Qal Alluvium (Holocene to Upper Pleistocene)--Upper part consists of silt,
sand, clay, and minor angular to round gravel; locally humic, nonbedded to
parallel bedded. Lower part consists of pebble and cobble gravel; parallel
bedding and both large- and small-scale crossbedding. Maximum exposed thickness
about 8 m
Qf Alluvial-fan deposits (Holocene to Upper Pleistocene)--Fan-shaped
deposits of silt, sand, clay, and angular to round gravel mapped near head of
Ross Creek on western margin, and in School Gulch at southern margin of
quadrangle
Qld Lake deposits (Holocene to Upper Pleistocene)--Coarse-grained gravel on
shore grading into clay and marl in center. Thickness 0.3-3 m
Qrt Rock talus (Holocene to Upper Pleistocene)--Accumulations of locally
derived boulder- to pebble-sized angular detritus at heads of drainages on both
sides of crest of Bridger Range
Qls Landslide deposits (Holocene to Middle Pleistocene)--Pebble to boulder
gravel; commonly silty sand to silty clay matrix; also includes largely intact
slide blocks of bedrock; nonsorted to poorly sorted; clasts chiefly angular to
subangular; nonbedded to crudely bedded. Includes deposits of avalanches,
slumps, earth flows, debris flows, and mudflows. Locally includes colluvium in
the larger deposits of east flank of Bridger Range. Characterized by hummocky
topography. Thickness 0 to about 10 m
Qc Colluvium (Holocene and Pleistocene)--Coarse- to fine-grained deposits
derived from nearby bedrock. Includes (1) poorly bedded, coarse, angular to
subrounded, gravel-size clasts containing variable amounts of fine-grained
matrix material composing alluvial fans and cones in rugged terrain; and (2)
sand, silt, and minor fine gravel containing variable amounts of fine-grained
matrix forming slope-wash deposits chiefly on volcanic rocks in gentle terrain.
Thickness generally 1-3 m
Qg Glacial deposits (Pleistocene)--Boulder to pebble gravel; extremely
coarse, irregular blocks as much as 10 m in diameter; unsorted; contains
variable amounts of silty sand matrix; combination of morainal, outwash, and
avalanche debris. Thickness as much as 80 m
Qoa Older Alluvium (Pleistocene)--Chiefly boulder to pebble gravel
containing variable amounts of silty sand matrix; includes glacial outwash
gravels along east flank of Bridger Range, the North Fork of Carrol Creek, and
along Cache Creek, and pediment gravels on northwest flank of Battle Ridge;
locally subdivided into three members along Bridger Creek as described below
Qt3 Older alluvium--Terrace gravels along Bridger Creek less than 45 m above
present stream levels
Qt2 Older alluvium--Terrace gravels along Bridger Creek 45-60 m above
present stream levels
Qt1 Older alluvium--Terrace gravels along Bridger Creek 60-90 m above
present stream levels
IGNEOUS ROCKS
Td Mafic dike (Eocene?)--A composite, mainly basic, dike injected along the
plane of the Pass thrust fault and along a fault south of Pine Creek;
principally porphyritic, panidiomorphic olivine-augite-biotite diorite
containing small segregations of biotite-augite syenite; thickness generally
less than 90 m, but as much as 150 m in places
Ts Composite sill (Eocene? or Paleocene?)--Sill confined to Middle Cambrian
strata north and south of Cross Range fault; in places consists of upper chilled
layer of biotite-augite microdiorite 30-60 cm thick, middle thin layer of
syenodiorite, and lower thick layer of biotite-augite diorite; entire sill is
24-60 m thick. Offset by minor thrust. May be as young as earliest Eocene
(Harlan and others, 1988)
SEDIMENTARY ROCKS
Fort Union Formation (Paleocene and Upper Cretaceous)
Tfnp Conglomerate lens at Nixon Peak (Paleocene)--Interbedded brown and
olive-gray sandstone and conglomerate (25 percent or more). Sandstone is medium
to coarse grained, epiclastic, slightly calcareous, thin to medium bedded, and
crossbedded; weathers into conspicuous vertical columns on Nixon Peak.
Conglomerate and conglomeratic sandstone are medium to thick bedded, as much as
3 m thick; clasts include subangular to subrounded cobbles and boulders as large
as 30 cm in diameter of Middle Proterozoic Spokane Formation and Greyson Shale
(Belt Supergroup), Paleozoic limestone and quartzite, Proterozoic gabbro and
diabase, and Cretaceous granodiorite derived from Big Belt Mountains to the
northwest, mixed with other volcanic, sedimentary, igneous, and rare metamorphic
rock fragments. Contacts are gradational with unit Tfu. Thickness 0-914 m
Tfu Upper conglomeratic and middle sandy members, undivided (Paleocene)--
Dusky-yellow-green and olive-gray sandstone, conglomerate, and minor siltstone
and mudstone. Sandstone is slightly calcareous, fine grained to conglomeratic;
composed of lithic volcanic, limestone, and quartzite grains. The thin- to
medium-bedded (beds as much as 60 cm thick) sandstone is crossbedded and locally
displays soft-sediment folds and slumps indicating western and northwestern
sources; wood and leaf impressions are common; clay pebbles and limestone
nodules are common in upper fine-grained sandstones that also contain rare
freshwater gastropods and pelecypods. Conglomerate is composed of cobbles of
subangular to subrounded multilithologic clasts of volcanic and igneous rocks,
sandstone, chert, fetid limestone, and rare gneiss and schist in southeastward-
thinning tongues (Piombino, 1979; Roberts, 1972; this paper); boulders as much
as 60 cm in diameter are present in upper part. Siltstone is dusky yellow green
and chiefly thin bedded; weathers to grayish yellow green. Mudstone is olive
gray and chiefly massive; weathers light olive gray. Basal 60-90 m of unit may
contain beds of latest Cretaceous age. Unit has gradational contacts with over
and underlying units; thickness more than 2,130 m
TKfc Basal conglomerate member (Paleocene? and Upper Cretaceous)--
Interbedded dusky-yellow-green and olive-gray sandstone, lenses of conglomerate,
and minor siltstone and mudstone. Sandstone is medium grained to conglomeratic,
calcareous, thin bedded and crossbedded; contains soft-sediment folds and
slumps, and weathers dark yellowish brown. Conglomerate is gray and brown,
medium bedded and crossbedded; clasts include pebbles, cobbles, and some
boulders as much as 30 cm in diameter of intermediate volcanic rocks, basalt,
chert, quartzite, limestone, minor coarse-grained intrusive rocks, and a few
gneiss pebbles derived from Archean through Cretaceous terranes; no fragments of
unequivocal Belt Supergroup origin were noted; western and northwestern sources
are indicated by crossbedding. Siltstone is dusky yellow green and thin bedded;
weathers grayish yellow green. Mudstone is olive gray and chiefly massive;
weathers light olive gray. Unit forms ridge composed of Battle Ridge and Grassy
Mountain and weathers to gravel-strewn slopes; contact with Hoppers Formation is
abrupt and is placed at base of lowest cobble conglomerate; gradational upper
contact with unit Tfu; unit thins to northeast; about 304 m thick in quadrangle;
228 m measured in sec. 35, T. 3 N., R. 8 E., 3.2 km east of quadrangle (Skipp
and McGrew, 1972)
Livingston Group (Upper Cretaceous)
Kh Hoppers Formation--Light-greenish-gray, light-olive-gray, and minor gray
and grayish-purple conglomerate, sandstone, siltstone, and mudstone. Unit
chiefly is fine grained, volcaniclastic, and calcareous. Locally, coarse-
grained and crossbedded sandstone and siltstone are exposed as thin friable beds
that weather olive gray and yellowish brown and that contain imprints and
carbonacous films of plants and woody material. Interlayered grayish-purple,
green, and gray mudstone commonly is calcareous and locally bentonitic.
Conglomerate is present as minor ridge-forming thin beds and lenses composed of
granules and pebbles of mainly western-derived Paleozoic and Mesozoic
sedimentary rocks and a few well-rounded gneiss pebbles as much as 20 cm in
diameter (Skipp and McGrew, 1972). Formation contains limestone nodules
throughout, though they are more common in lower part; rare ironstone nodules
are found in upper part. Unit forms a steep slope below basal conglomerate
member of Fort Union Formation (unit Tkfc). Contact with Billman Creek
Formation (unit Kbc) is gradational and is placed at base of lowest thick (about
7.5 m) sandstone bed. Thickness ranges from 450 to 730 m; 730 m measured in
secs. 26 and 35, T. 3 N., R. 8 E., 3.2 km east of Sedan quadrangle (Skipp and
McGrew, 1972)
Kbc Billman Creek Formation--Grayish-red, grayish-green and gray,
volcaniclastic mudstone and siltstone interbedded with minor volcanic sandstone
and conglomerate and vitric tuff. Unit is chiefly volcaniclastic mudstone and
siltstone that are gray and green in lower 213 m and grayish red above;
calcareous, containing common carbonaceous material and common yellowish-brown-
weathering calcareous concretions; locally rich in magnetite and zeolites.
Interlayered lenses of fine-grained to conglomeratic volcaniclastic sandstone
are calcareous, containing 'cannonball' structures, are thin bedded to massive,
and are locally crossbedded. Conglomerate lenses contain subangular to
subrounded pebbles and cobbles of intermediate volcanic rocks and accessory
Paleozoic limestone and quartzite. Conglomerate and sandstone lenses are common
in upper beds in southern part of quadrangle and in lower beds in northern part.
Freshwater mollusks and Hadrosaurian dinosaur bones are common in lower mudstone
beds (Skipp and McGrew, 1972). Unit forms valleys. Contact with Lennep
Sandstone Member of Sedan Formation (unit Ksle) is gradational and is placed at
top of highest ridge-forming sandstone in that member. Estimated thickness 760-
914 m
Ks Sedan Formation--Chiefly western-derived volcaniclastic sandstone and
mudstone, and minor ash-flow tuffs; divided into the following five members;
unit used only on cross sections
Ksle Lennep Sandstone Member--Ridge-forming , olive-gray, greenish-gray, and
light-gray, volcaniclastic sandstone, conglomerate, and minor mudstone and
devitrified vitric tuff. Fine-grained to conglomeratic sandstone is calcareous,
is poorly bedded to crossbedded, has local magnetite concentrations along
bedding planes, contains reddish-brown-weathering "cannonball" concretions and
abundant carbonaceous material, and weathers yellowish brown. Iron staining and
zeolitic alteration locally are common. Lenses of volcaniclastic pebble and
cobble conglomerate contain cobbles as much as 15 cm in diameter of intermediate
volcanic rocks and a few pebbles of Paleozoic quartzite and limestone. Minor
siliceous mudstone is brown and massive. Thin beds of light-green and light-
gray, zeolitized (laumontite) vitric tuff are present in lower part of member.
Unit contains rare dinosaur bone fragments, freshwater and brackish-water
mollusks, and, in northern part of quadrangle, Ophiomorpha, a marine crustacean.
Gradational lower contact of unit is placed at base of lowest prominent
sandstone ledge. Thickness is about 106-152 m (Skipp and McGrew, 1977)
Ksm Mudstone member--Greenish-gray and brownish-gray, volcaniclastic
mudstone, siltstone, sandstone, and minor interbedded conglomerate and altered
vitric tuff. Siliceous mudstone is sandy, silty, locally bentonitic, massive,
and veined with calcite; contains abundant orange zeolite (clinoptilolite);
mudstone may be chiefly altered vitric lithic tuff. Fine-grained to
conglomeratic, volcaniclastic sandstone and siltstone are locally calcareous and
zeolitic, crossbedded, and graded. Yellowish-gray bentonite and light-gray-
weathering, altered vitric tuff are common in upper beds. Rare lenses of
volcanic pebble and cobble conglomerate containing a few boulders as much as 0.9
m in diameter of coarsely porphyritic augite andesite that resemble Member H of
Maudlow Formation are present in middle beds in northern part of quadrangle
(Skipp and McGrew, 1977). Unit contains freshwater mollusks, wood, and dinosaur
bones, including one femur identified as Gorgosaurus sp. (Nicholas Hotton III,
written commun., 1971). Member forms valleys and low barren hills, and has a
gradational contact with Middle sandstone member (unit Ksms) below. Thickness
ranges from 274 to 304 m
Ksms Middle sandstone member--Olive-green, olive-gray, and dark-greenish-
gray, volcaniclastic sandstone, conglomerate, mudflow conglomerate, and minor
siltstone and mudstone. Fine-grained to conglomeratic, but mainly medium- to
coarse-grained sandstone is calcareous, locally mottled, and crossbedded;
weathers brown; contains carbonaceous material and zeolites. Lenses of volcanic
conglomerate and mudflow conglomerate in upper part contain fragments of
intermediate volcanic rocks as much as 30 cm in diameter that resemble lava
flows of Member F of Maudlow Formation of Livingston Group in Maudlow Basin, 12
km to the northwest (Skipp and McGrew, 1972; 1977); a K-Ar radiometric age on
hornblende from Member F of Maudlow Formation is 76.6±1 Ma (Marvin and others,
1989). A light-gray, calcareous, biotitic quartzose sandstone present at base
of unit in northern part of area is correlated with upper part of Parkman
Sandstone Member in northern parts of western Crazy Mountains Basin (Skipp and
McGrew, 1977). Unit forms series of ridges and disconformably overlies Ash-
flow tuff member (unit Ksa); contact is placed at top of highest ash-flow tuff
or ash-flow tuff conglomerate. Thickness is about 304-436 m
Ksa Ash-flow tuff member--Pale-yellowish-green, light-greenish-gray,
grayish-red, and pale-yellowish- brown, welded to nonwelded tuff and ash-flow
tuff conglomerate, interbedded with volcaniclastic conglomerate, sandstone,
mudstone, and porcelanite. Tuff is dacitic and fine grained, containing locally
abundant phenocrysts of golden-weathering biotite and minor andesine, augite,
hypersthene, and altered cognate inclusions; glass is mostly devitrified, but
thin (90- to 150-cm-thick) zones of perlitic glass are present in northwestern
part of quadrangle. Conglomerate composed of ash-flow tuff pebbles marks base
and top of unit in some places. Welded tuff is composed of a maximum of three
composite cooling units, each 0-91 m thick, separated by intervals of greenish-
gray to light-gray, volcaniclastic sedimentary rocks including greenish-gray,
olive-green, and brown porcelanite. Wood is present in volcaniclastic beds.
Unit forms resistant knobs and ridges and disconformably overlies lower
sandstone member (unit Ksl). Thickness about 60-152 m. Tuffs thicken to
northwest ( Skipp and Peterson, 1965; Skipp and Hepp, 1968). Unit equivalent to
Welded tuff member of Skipp and McGrew (1977)
Ksl Lower sandstone member--Dark-olive-gray, greenish-gray, and yellowish-
gray, volcaniclastic sandstone, siltstone, mudstone, altered crystal lithic
tuff, minor volcaniclastic granule and pebble conglomerate, minor grayish-red-
purple hornblende dacite, and minor lignitic coal. Volcaniclastic sedimentary
rocks, chiefly sandstone, are fine grained to conglomeratic and calcareous,
containing common calcareous concretions and carbonacous plant material,
including leaf, needle, twig, and cone imprints; medium bedded and locally
crossbedded. Magnetite-rich zones in the sandstone beds and ironstone nodules
are common in lower part, and, locally, dark-brown lignitic coal is found at the
base. A lens of dacite in upper part of member that was identified about 1 km
southwest of northwest corner of quadrangle is correlated with Member B of
Maudlow Formation of Livingston Group about 12 km to the northwest (Skipp and
McGrew, 1977); a K-Ar age on hornblende from dacite of Member B is 80.8±1 Ma
(Marvin and others, 1989). Unit forms a low ridge and has an abrupt contact
with underlying Eagle Sandstone (unit Ket) throughout most of area, but units
are gradational just south of quadrangle (Roberts, 1963, 1964a,b, 1972).
Thickness is 152-304 m
KJr Eagle Sandstone, Telegraph Creek Formation, Cody Shale, Frontier
Formation, Mowry Shale, Thermopolis Shale, Kootenai Formation, Morrison
Formation, and Ellis Group, undivided (Cretaceous and Jurassic)--Mudstone,
sandstone, minor limestone, conglomerate, and porcelanite; includes Cross Range
fault zone rubble comprising Morrison Formation, Ellis Group, and Kootenai
Formation about 1.5 km east of Fairy Lake. Shown undivided primarily on cross
sections
Ket Eagle Sandstone and Upper Part of Telegraph Creek Formation, undivided
(Upper Cretaceous)--Eagle Sandstone in upper part is light-olive-gray,
yellowish-gray and medium-gray sandstone, minor gray shale, and thin black coal
seams. Very fine grained to medium-grained sandstone is quartzose, feldspathic,
biotitic, and chiefly calcareous, containing brown-weathering 'cannonball'
concretions; crossbedded and weathers yellowish gray. Basal Virgelle Sandstone
Member consists of dark-greenish-gray and greenish-gray, volcaniclastic
sandstone that is magnetite-rich and forms a ledge. Upper part of Telegraph
Creek Formation is medium-gray and light-olive-gray sandstone, siltstone, and
minor mudstone. Fine-grained sandstone is quartzose, micaceous, biotitic, and
calcareous, containing large 'cannonball' concretions; thin-bedded; contains
fossils--mollusks, rare ammonites, and wood impressions; forms slopes and has a
gradational lower contact. Thickness of map unit is 61-152 m ; thicker in
southern part of quadrangle
Ktc Lower part of Telegraph Creek Formation (Upper Cretaceous)--Medium-dark-
to dark-gray mudstone and light-gray sandstone, siltstone, and minor bentonite.
Silty and sandy mudstone and very fine grained sandstone are biotitic,
micaceous, calcareous, containing limestone nodules, and carbonacous; thin
bedded and fossiliferous, containing mollusks and ammonites. Unit forms valleys
or gentle slopes and is poorly exposed throughout area. Formation has
gradational basal contact with Cody Formation (unit Kc). Thickness about 61-122
m
Kc Cody Shale (Upper Cretaceous)--Gray shale and mudstone interbedded with
grayish-green and olive-gray sandstone and siltstone and minor brown-weathering
nodular limestone and yellowish-gray bentonite. Mudstone and shale are both
calcareous and noncalcareous, locally biotitic, silty and sandy; contain
limestone nodules, ironstone nodules, and cone-in-cone structures. Fine-grained
sandstone is quartzose but contains abundant detrital rock fragments, is
calcareous, argillaceous, and thin bedded. Mudstone and shale form slopes in
lower and upper parts of interval. Eldridge Creek Sandstone Member near center
of interval consists of ridge-forming sandstone that is greenish gray and olive
gray, fine grained, thin bedded, crossbedded, and ripple marked; locally
contains abundant glauconite. Member is about 30 m thick. Entire formation is
locally fossiliferous and contains fish scales, starfish, mollusks, and
ammonites. Unit is poorly exposed in quadrangle; sandstone ledges of Eldridge
Creek Sandstone Member crop out locally. Basal contact is conformable.
Thickness is about 304 m
Kf Frontier Formation (Upper Cretaceous)--Ledges of light- to medium-gray,
olive-gray, and dark-greenish-gray sandstone separated by mudstone and siltstone
intervals that contain minor chert-pebble conglomerate, bentonite, and siliceous
limestone. Fine- to coarse-grained sandstone is quartzose, feldspathic, lithic,
calcareous, argillaceous, thin to medium bedded, and locally crossbedded;
contains heavy-mineral concentrations on bedding planes; sandstone weathers
brown and olive gray and forms prominent ledges. Distinctive sandstone at top
of unit is light gray to light olive gray, friable, calcareous, and crossbedded.
East of Ross Peak sandstones contain calc-silicate minerals that give them a
mottled appearance. Dark-gray and greenish-gray mudstone and siltstone
intervals as much as 30 m thick are siliceous and thin bedded, containing a few
friable, fine-grained, calcareous sandstone beds. Marker beds in the upper
mudstone intervals include thin, black chert-pebble conglomerate composed of
well-rounded pebbles less than 2.5 cm in diameter, grayish-green siliceous
limestone lenses, and thin beds of bentonite and fossil oyster (mollusk) banks.
Basal contact is conformable. Thickness is about 152 m
Kmf Mowry Shale, Muddy Sandstone, Skull Creek Shale, and Fall River
Sandstone, undivided (Lower Cretaceous)--Medium-dark-gray and greenish-gray
mudstone, sandstone, porcelanite, and minor coal. Formations are described in
descending order. Mowry Shale is medium-dark-gray and greenish-gray mudstone,
sandstone, and porcelanite. Muddy Sandstone is light-olive-gray to greenish-
gray sandstone that is fine grained to conglomeratic; contains much volcanic
detritus; is chiefly noncalcareous, thin bedded, and crossbedded, containing a
thin, small pebble conglomerate bed near base. Muddy Sandstone forms a ledge
about 12 m thick. Skull Creek Shale is grayish-green interbedded mudstone,
siltstone, and fine-grained sandstone that is rich in volcanic detritus;
laminated to thin bedded, crossbedded, and locally calcareous; contains minor
thin coal beds. Fall River Sandstone is ridge-forming sandstone that is
greenish gray to grayish orange, medium grained, quartzose and quartzitic,
crossbedded, laminated, and ripple-marked; weathers yellowish brown; ledge is
about 11 m thick. Unit is poorly exposed in quadrangle and has a disconformable
basal contact. Thickness is about 182 m
Kk Kootenai Formation (Lower Cretaceous)--Red, gray, and purple mudstone,
interbedded with yellowish-gray and grayish-purple sandstone and minor
conglomerate and medium-light-gray freshwater nodular limestone. Medium- to
coarse-grained sandstone in upper part is quartzose, impure, and commonly
hematitic. Medium-light-gray limestone in nodular layers is common in upper
beds about 30 m below the top and just above the basal sandstone and
conglomerate; commonly contains freshwater gastropods. Basal ledge-forming,
coarse-grained sandstone and conglomerate are slightly argillaceous and are
composed of salt-and-pepper chert and quartz grains as large as pebble size.
Basal ledge is about 20 m thick. Formation is poorly exposed except for
fragments of the basal sandstone and conglomerate. Unit disconformably overlies
Morrison Formation (unit Jm). Thickness ranges from 111 to 121 m
Jme Morrison Formation and Ellis Group, undivided (Middle and Upper
Jurassic)--Poorly exposed, varicolored mudstone containing minor sandstone and
limestone; mapped only along gully northeast of Fairy Lake
Jm Morrison Formation (Upper Jurassic)--Red, green, and purple mudstone and
hackly shale intercalated with light-gray, yellowish-brown, and yellowish-orange
siltstone and sandstone. Upper 15-23 m includes light- to dark-gray
carbonaceous shale and mudstone; locally, lower part contains irregularly bedded
impure limestone and limestone nodules. Formation is poorly exposed and has a
conformable basal contact. Thickness is 91-133 m
Je Ellis Group (Upper and Middle Jurassic)--Consists in descending order of
Swift Sandstone, Rierdon Formation, and Sawtooth Formation. Swift Sandstone is
yellowish brown to grayish brown, medium to coarse grained, quartzose, very
calcareous, and glauconitic, containing scattered chert pebbles; is crossbedded
and fossiliferous (mollusks). Rierdon Formation consists of an upper yellowish-
gray calcareous shale and impure limestone and a lower gray-weathering, medium-
to thick-bedded, ledge-forming oolitic limestone. Sawtooth Formation includes
an upper red and yellow calcareous mudstone and shale, a middle gray-weathering,
dense, platy limestone and interbedded calcareous shale, and a basal sandy to
pebbly limestone or conglomeratic calcareous sandstone. Unit thins northward
and unconformably overlies Phosphoria or Quadrant Formation (unit PMpa).
Thickness varies from about 36 to 91 m
PCr Phosphoria and Quadrant Formations; Amsden , Snowcrest Range and Madison
Groups; and Three Forks Formation, Jefferson Dolomite, Maywood Formation, Snowy
Range Formation, Pilgrim Limestone, Park Shale, Meagher Limestone, Wolsey Shale,
and Flathead Sandstone, undivided (Permian, Pennsylvanian, Mississippian,
Devonian, Ordovician, and Cambrian)--Limestone, dolostone, mudstone, and
sandstone; shown undivided only on cross sections
PMps Phosphoria and Quadrant Formations and Amsden and Snowcrest Range
Groups, undivided (Permian, Pennsylvanian, and Mississippian)--Poorly exposed
mudstone, locally stained red, containing fragments of sandstone, dolostone, and
limestone. See units PMpa and Msr. Mapped on eastern flank of southern part of
Bridger Range; interval about 50-130 m thick
PMpa Phosphoria and Quadrant Formations and Amsden Group, undivided
(Permian, Pennsylvanian, and Mississippian)--Yellow, greenish-yellow, pale-gray-
brown sandstone, white to yellowish-brown dolostone and limestone, red to purple
dolomitic mudstone and shale, and minor green, nodular chert beds. Formations
are described in descending order. Phosphoria Formation (Permian) is yellow to
greenish-yellow sandstone containing scattered chert nodules; nodular chert beds
with interstitial sand; soft, green, noncalcareous, nonphosphatic shale; and
chert breccia or conglomerate. Thickness is 0-12 m; formation is absent north
of Fairy Lake. Quadrant Formation (Pennsylvanian) is pale-gray-brown to white,
fine-grained to very fine grained, medium-bedded to massive, crossbedded
quartzose sandstone that contains some white to pale-yellow-gray, dense granular
dolostone beds intercalated in lower part. Thickness is about 15-43.5 m.
Amsden Group (Pennsylvanian and Mississippian) includes an upper pale-yellow-
brown to white, dense, medium-granular, medium-bedded dolostone, containing a
few thin beds of pale-gray-brown, fine-grained quartzose sandstone (probably the
Devil's Pocket Formation) that unconformably overlies a lower red to purple
dolomitic mudstone and shale interbedded with impure silty or argillaceous
dolostone and limestone (probably Tyler Formation). Thickness of Amsden Group
about 32-103 m. Unit unconformably overlies Snowcrest Range Group and is mapped
separately in northern part of Bridger Range. Thickness of entire interval is
47-158 m
Msr Snowcrest Range Group (Upper Mississippian)--Gray and gray-brown
limestone and dolostone; red, pink, and yellow-orange sandstone; red and pink
siltstone; red to purple shale; and a red-stained breccia. Group is divisible
into three formations, described in descending order: The Conover Ranch
Formation consists of ledge-forming, medium-bedded, gray to gray-brown, chert-
nodule-bearing limestone and dolostone. Lower contact is gradational with
Lombard Limestone, which consists of dark-gray to purplish-gray and black,
fossiliferous shale or shaly limestone. Thickness of combined Conover Ranch
Formation and Lombard Limestone varies from zero to about 61 m. Lombard
Limestone unconformably overlies Kibbey Formation, which consists of three
parts: upper part is red, pink, and pale-yellow-orange, platy to massive
sandstone, sandy siltstone, and sandy dolostone, containing intercalated red
siltstone; middle part is red and pink, blocky-fracturing dolomitic siltstone,
and red to purple, hackly shale containing some thin pale-gray or cream-colored,
purple-mottled, fine-grained dolostone; lower part is cream- and lavender-
mottled, irregularly bedded, fine-grained dolostone or a red-stained breccia of
limestone and dolostone fragments (McMannis, 1955). Thickness of Kibbey
Formation varies from 11 to 71 m. Thickness of group varies from 11 to 122 m
MDmm Madison Group, Three Forks Formation, Jefferson Dolomite, and Maywood
Formation, undivided (Mississippian and Devonian)--Fault zone breccia consisting
of limestone and dolostone fragments derived from these formations in a
structural horse just north of southern border of quadrangle, southwest of Baldy
Mountain
Madison Group (Upper and Lower Mississippian)--Limestone and dolostone
divided into an upper thick-bedded formation, the Mission Canyon Limestone, and
a lower thin-bedded formation, the Lodgepole Limestone
Mmc Mission Canyon Limestone (Upper and Lower Mississippian)--Pale-yellow-
brown, massive, poorly bedded limestone and dolostone that weather light gray
and form cliffs and castellated ridges. Chert and limestone nodules are common
in middle and upper beds. Several conspicuous solution-collapse breccias occupy
persistent stratigraphic positions. Unit has a gradational lower contact with
Lodgepole Limestone (unit Mlp) and ranges in thickness from about 220 to 290 m;
it is thickest near Sacagawea Peak
Mlp Lodgepole Limestone (Lower Mississippian)-- Gray and brown limestone and
minor dark-brown to black silty shale. Formation is divisible into three
members: Upper Woodhurst Limestone Member consists of pale-yellow-brown,
orange-brown, gray-brown, red-stained, thin-bedded, and fine-grained limestone,
and intercalated medium- to thick-bedded, lighter colored, massive, cliff-
forming, crinoidal, very fossiliferous (corals, brachiopods) limestone.
Woodhurst Limestone Member is 134-146 m thick. Middle Paine Shale Member
includes dark-gray-brown, mainly thin-bedded and platy, fine-grained, brittle,
sparsely fossiliferous limestone, intercalated with yellow-weathering shaly
limestone, and local Waulsortian bioherms (Stone, 1972; Smith, 1982). 'W'
indicates positions of Waulsortian bioherms on map. Member is 94-99 m thick.
Basal Cottonwood Canyon Member is dark-brown to black silty shale and siltstone.
Member is 0.6-0.9 m thick. Formation unconformably overlies Sappington Member
of Three Forks Formation (unit Dtm) Total thickness is 228-246 m
Dtm Three Forks Formation, Jefferson Dolomite, and Maywood Formation,
undivided (Upper Devonian)--Light- and dark-brown dolostone; gray and gray-
green, nodular limestone; yellowish-brown sandstone; pink and gray siltstone;
black and green shale; and minor dolostone breccia. Unit comprises, in
descending order, three formations and their members. The Three Forks Formation
is divisible into three members: Sappington Member at top consists of
yellowish-brown, very fine grained, calcareous sandstone that grades downward to
gray and gray-green silty shale and silty to sandy, nodular, oncolith-bearing
limestone and a thin basal conodont-bearing, black shale. Sappington Member
disconformably overlies middle Trident Member, which consists of gray, nodular
limestone in upper part and green shale intercalated with some dolomitic
siltstone in main part. Underlying basal Logan Gulch Member includes an upper
ledge-forming, brecciated limestone underlain by evaporite-solution breccia and
red to orange, nodular, limonitic shale; conformable lower contact. Three Forks
Formation is conformable above Jefferson Dolomite and is 61-70 m thick.
Jefferson Dolomite consists of light- and dark-brown, mainly medium- to thick-
bedded, fine- to medium-grained, saccharoidal dolostone; dolomitic limestone;
and limestone having a few intercalated yellow and pale-pink dolomitic siltstone
and green dolomitic shale beds and associated dolostone breccia lenses. Lower
contact is gradational with Maywood Formation. Jefferson Dolomite is about 152-
188 m thick. Maywood Formation in southern outcrops consists mainly of
alternating thin beds of yellow to gray siltstone, dolomitic siltstone, and
dolostone totaling about 12 m in thickness; northern outcrops include about 27 m
of mainly reddish-orange to pale-yellow-gray, thin-bedded, platy siltstone and
mudstone, and, at the top, 1 m or so of gray-brown, platy, fine-grained
limestone. Unit disconformably overlies Upper Cambrian beds. Entire interval
is 225-286 m thick
OCsp Snowy Range Formation and Pilgrim Limestone, undivided (Lower
Ordovician and Upper Cambrian)--Dark- and light-gray mottled and grayish-brown
limestone, limestone-pebble conglomerate, and grayish-green shale. Snowy Range
Formation is divided into two parts: Upper part, the Sage Pebble Conglomerate
Member, consists of gray-brown, fine-grained, thin-bedded limestone; limestone-
pebble conglomerate; and interbedded green shale conformably underlain by a
thin, columnar algal limestone. Upper part has a conformable contact with lower
part. Lower part, the Dry Creek Shale Member, is mainly gray-green fissile
shale that contains a few intercalated yellow, calcareous siltstone or very fine
grained sandstone beds. Basal contact of formation is conformable. Snowy Range
Formation is about 51-84 m thick. Upper part of Pilgrim Limestone consists of
dark- and light-gray mottled, medium- to thick-bedded, partly dolomitized,
medium-grained, oolitic, locally crossbedded limestone and a few intercalated
beds of flat-pebble conglomerate. Uppermost 3-4.5 m is dense, mottled limestone
similar to that of Meagher Limestone. Upper part is 70-74 m thick. Lower part
consists mainly of gray and yellow-brown, thin- to medium-bedded, dense to
bioclastic limestone, limestone-pebble conglomerate, and edgewise conglomerate;
includes interbedded gray-green, fissile, calcareous shale, and a 2.4- to 3-m-
thick, gray-brown, massive, oolitic, vaguely mottled limestone at base. Lower
part is 39-57 m thick. At Bridger Peak, a massive, pale-greenish-brown, vaguely
mottled, fine-grained, reefoid, partly columnar (algal) limestone is between the
upper and lower parts. Basal contact is gradational. Pilgrim Limestone is 110-
131 m thick. Entire interval is about 161-215 m thick
Cpf Park Shale, Meagher Limestone, Wolsey Shale, and Flathead Sandstone,
undivided (Middle Cambrian)--Green and maroon, micaceous shale; dark-gray and
yellow mottled limestone; and red, pale-orange, and white sandstone. Unit
comprises, in descending order, four formations. Park Shale includes green and
maroon, very finely micaceous, fissile shale intercalated with thin-bedded
limestone at top and local beds of arkosic limestone and arkose; is locally
glauconitic in lower part. In northern Bridger Range, the lower 30 m consists
of interbedded arkosic sandstone, siltstone, and shale (Fryxell and Smith,
1986). Formation has a conformable lower contact. Park Shale is about 66 m
thick. Meagher Limestone consists of three parts: Upper part is thin-bedded,
dark-gray, dense limestone and interbedded green shale. Main middle ledge-
forming part is massive, dark-gray and yellow mottled, dense limestone. Lower
part includes thin-bedded, dark-gray, dense limestone and interbedded green and
yellow, silty shale. Lower contact is conformable. Meagher Limestone is about
112 m thick. Wolsey Shale consists of green and maroon, micaceous shale
interbedded with micaceous sandstone and siltstone; in places it contains
conglomeratic arkosic limestone and arkose. Lower contact is conformable.
Wolsey Shale is about 45-65 m thick. Flathead Sandstone contains red, pale-
orange, and white sandstone, locally quartzitic, and some glauconitic beds.
Flathead locally contains feldspathic sandstone and arkose beds, conglomeratic
in places. Sandstone is about 36-42 m thick. Unit unconformably overlies
arkose of Belt Supergroup (unit Yl) in northern part of area and on Archean
metamorphic rocks in southern part. Entire interval is 259-285 m thick
Yl La Hood Formation of Belt Supergroup (Middle Proterozoic)--Dark-gray-
green, reddish-weathering, coarse, massive, poorly bedded arkose and
conglomeratic arkose. Formation contains very coarse gneiss boulder
conglomerate in which boulders are as much as 2.4 m in diameter in southwestern
exposures. Intercalated dark-gray argillite and siliceous limestone beds are
common in upper part in northern exposures. Base is not exposed. Minimum
thickness ranges from about 2,134 m to more than 3,048 m. Unit is in fault
contact with Archean metamorphic rocks (McMannis, 1955, 1963)
Wm Metamorphic rocks (Archean)--Intermediate to felsic gneiss, amphibolite,
schist, metaquartzite, marble, and numerous small pegmatite dikes and veinlets
(McMannis, 1955; Lageson, 1989). Thickness is unknown
NOTE: The following explanation covers graphic representations of symbols
used on the Sedan quadrangle map:
Contact-Long dashed where approximately located; short dashed where
gradational; dotted where concealed
Fault-Dashed where approximately located; dotted where concealed; queried
where doubtful
Normal or oblique slip-Arrows indicate sense of relative movement; U,
upthrown side; D, downthrown side
Thrust-Sawteeth on upper plate; U, apparent upthrown side; D, apparent
downthrown side; arrows on map indicate oblique slip and in cross sections they
indicate relative movement
Detachment-Filled half circles indicate upper deformed plate
Anticline-Showing crestline and plunge of fold. Dashed where approximately
located; dotted where concealed
Overturned anticline-Showing crestline and direction of dip of limbs. Dashed
where approximately located; dotted where concealed
Syncline-Showing troughline and plunge of fold. Dashed where approximately
located; dotted where concealed
Overturned syncline-Showing troughline and direction of dip of limbs. Dashed
where approximately located; dotted where concealed
Strike and dip of beds in sedimentary rocks
Horizontal
Inclined
Vertical
Overturned
Estimated
Crumpled, vertical
Eutaxitic layering in ash-flow tuffs
Inclined
Overturned
Strike and dip of layering in metamorphic rocks
Inclined
Vertical
Calcite vein
Waulsortian bioherm
Oil test showing lease name and operator's name
Spring
Gravel pit
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Union Formation near Livingston, Montana-An evaluation as a host for sandstone
type uranium mineralization: Missoula, University of Montana, M.S. thesis, 84 p.
Price, R.A., and Fermor, P.R., 1984, Structure section of the Cordilleran
foreland thrust and fold belt west of Calgary, Alberta: Geological Survey of
Canada Paper 84-14.
Raisz, Erwin, 1957, Landforms of the United States: Melrose, Mass., Raisz
Landform Maps, Sixth Revised Edition.
Roberts, A.E., 1963, The Livingston Group of south-central Montana, in Short
papers in geology and hydrology: U.S. Geological Survey Professional Paper 475-
B, p. B-86-B-91.
Roberts, A.E., 1964a, Geologic map of the Fort Ellis quadrangle, Montana:
U.S. Geological Survey Miscellaneous Geologic Investigations Map I-397, scale
1:24,000.
Roberts, A.E., 1964b, Geologic map of the Bozeman Pass quadrangle, Montana:
U.S. Geological Survey Miscellaneous Geologic Investigations Map I-399, scale
1:24,000.
Roberts, A.E., 1972, Cretaceous and early Tertiary depositional and tectonic
history of the Livingston area, southwestern Montana: U.S. Geological Survey
Professional paper 526-C, 120 p.
Robinson, G.D., 1963, Geology of the Three Forks quadrangle, Montana: U.S.
Geological Survey Professional Paper 370, 143 p.
Schmidt, C.J., and Garihan, J.M., 1983, Laramide tectonic development of the
Rocky Mountain foreland of southwestern Montana, in Lowell, J.D., ed., Rocky
Mountain foreland basins and uplifts: Denver, Colo., Rocky Mountain Association
of Geologists, p. 271-294.
Schmidt, C.J., and Garihan, J.M., 1986, Middle Proterozoic and Laramide
tectonic activity along the southern margin of the Belt Basin, in Roberts, S.M.,
ed., Belt Supergroup-A guide to Proterozoic rocks of western Montana and
adjacent areas: Montana Bureau of Mines and Geology Special Publication 94, p.
217-235.
Schmidt, C.J., and O'Neill, J.M., 1982, Structural evolution of the southwest
Montana transverse zone, in Powers, R.B., ed., Geological studies of the
Cordilleran thrust belt, volume I: Denver, Colo., Rocky Mountain Association of
Geologists, p. 193-218.
Schmidt, C.J., O'Neill, J.M., and Brandon, W.C., 1988, Influence of Rocky
Mountain foreland uplifts on the development of the frontal fold and trust belt,
southwestern Montana, in Schmidt, C.J., and Perry, W.J., Jr., eds., Interaction
of the Rocky Mountain foreland and the Cordilleran thrust belt: Geological
Society of America Memoir 171, p. 171-201.
Skipp, Betty, 1977, Geologic map and cross section of the Wallrock
quadrangle, Gallatin and Park Counties, Montana: U.S. Geological Survey Geologic
Quadrangle Map GQ-1402, scale 1:24,000.
Skipp, Betty, and Hepp, M.M., 1968, Geologic map of the Hatfield Mountain
quadrangle, Gallatin County, Montana: U.S. Geological Survey Geologic Quadrangle
Map GQ-729, scale 1:24,000.
Skipp, Betty, and McGrew, L.W., 1968, Tertiary structure of the west edge of
the Crazy Mountains basin, Montana: Geological Society of America Special Paper
121, p. 637-638
Skipp, Betty, and McGrew, L.W., 1972, The Upper Cretaceous Livingston Group
of the western Crazy Mountains Basin, Montana: Montana Geological Society
Guidebook, 21st Annual Field Conference, 1972, p. 99-106.
Skipp, Betty, and McGrew, L.W., 1977, The Maudlow and Sedan Formations of the
Upper Cretaceous Livingston Group on the west edge of the Crazy Mountains Basin,
Montana: U.S. Geological Survey Bulletin 1422-B, p. B1-B68.
Skipp, Betty, and Peterson, A.D., 1965, Geologic map of the Maudlow
quadrangle, southwestern Montana: U.S. Geological Survey Miscellaneous Geologic
Investigations Map I-452, scale 1:24,000.
Smith, D.L., 1982, Waulsortian bioherms in the Paine Member of the Lodgepole
Limestone (Kinderhookian) of Montana, U.S.A., in Bolton, Keith, Lane, H.R., and
Lemone, D.V., eds., Symposium on the paleo-environmental setting and
distribution of Waulsortian facies: El Paso, Texas, and Alamagordo, N. Mex., El
Paso Geological Society and the University of Texas at El Paso, p. 51-64.
Stone, R.A., 1972, Waulsortian type bioherms of Mississippian age, central
Bridger Range, Montana: Montana Geological Society Guidebook, 21st Annual Field
Conference, 1972, p. 36-55.
Thompson, G.R., Fields, R.W., and Alt, David, 1982, Land-based evidence for
Tertiary climatic variations-Northern Rockies: Geology, v. 10, p. 413-417.
Tysdal, R.G., 1986, Thrust faults and back thrusts in Madison Range of
southwestern Montana foreland: American Association of Petroleum Geologists
Bulletin, v. 70, p. 360-376.
Winston, Don, 1986a, Stratigraphic correlation and nomenclature of the Middle
Proterozoic Belt Supergroup, Montana, Idaho and Washington, in Roberts, S.M.,
ed., Belt Supergroup-A guide to Proterozoic rocks of western Montana and
adjacent areas: Montana Bureau of Mines and Geology Special Publication 94, p.
69-84.
Winston, Don, 1986b, Middle Proterozoic tectonics of the Belt Basin, western
Montana and northern Idaho, in Roberts, S.M., ed., Belt Supergroup-A guide to
Proterozoic rocks of western Montana and adjacent areas: Montana Bureau of
Mines and Geology Special Publication 94, p. 245-257.
Wooden, J.L., Mogk, D.W., and Mueller, P.A., 1988, A review of the
geochemistry and geochronology of the Archean rocks of the northern part of the
Wyoming Province, in Ernst, W.G., ed., Metamorphism and crustal evolution of the
Western United States [Rubey Volume VII]: Englewood Cliffs, N.J., Prentice Hall,
Inc., p. 383-410.
Woodward, L.A., 1982, Tectonic map of the fold and thrust belt and adjacent
areas, west-central Montana: Montana Bureau of Mines and Geology Geologic Map
30, scale 1:250,000.
ACC refers to accuracy of location of contacts.
1=accurate
2=approximate
4=concealed
5=gradational
The geo_pnt coverage includes points that are orientation of beds in
sedimentary rocks and orientation of eutaxitic layering in ash-flow tuffs. The
coverage consists of the following items:
GEOCODE
STK
DIP
POS
ACC
CON
Items in the geo_pnt coverage are defined as follows:
GEOCODE refers to the type of surface for which orientation is given. The
value for GEOCODE in the geo_pnt coverage is one of the following: "BEDDING
SURFACE" and "ASHFLOW SURFACE."
STK for bedding surface refers to strike of beds in sedimentary rocks and for
ashflow surface refers to strike of eutaxitic layering in ash-flow tuffs.
DIP for bedding surface refers to dip value for beds in sedimentary rocks and
for ashflow surface refers to dip value for eutaxitic layering in ash-flow
tuffs. NOTE: The info files give the azimuth for strike and the value for dip;
the direction of dip is not readily apparent from the info files. The user
should refer to the plotted graphic to determine direction of dip.
POS refers to position of the bedding in sedimentary rocks or to position of
eutaxitic layering in ash-flow tuffs.
1=inclined
2=overturned
3=horizontal (bedding in sedimentary rocks only)
4=vertical (bedding in sedimentary rocks only)
ACC refers to accuracy in terms of whether the orientation of beds or
layering was measured or estimated.
1=measured
2=estimated (bedding in sedimentary rocks only)
CON refers to whether the bedding surface in sedimentary rocks is crumpled.
1=other (i.e., other surfaces not designated as crumpled)
2=crumpled
The stru_net coverage includes arcs that are faults and folds. The coverage
consists of the following items:
GEOCODE
TYP
ACC
DIR
POS
Items in the stru_net coverage are defined as follows:
GEOCODE refers to the type of geologic feature. The value for GEOCODE in the
stru_net coverage is one of the following: "FAULT" and "FOLD."
TYP refers to the type of fault or fold.
1=normal or oblique slip fault
2=thrust fault
5=detachment fault
6=queried (really an element of ACC but was included with GEOCODE; queries
used on fault where fault doubtful)
7=anticline (shows crestline of fold)
8=syncline (shows troughline of fold)
NOTE: The direction of the arcs is significant in that it determines on
which side the sawteeth or half circles are placed on the thrust and detachment
faults. The sawteeth or half circles are on the upper plate. If these
coverages are cleaned the arcs can 'flip' and the sawteeth or half circles will
end up on the incorrect side of the fault. Please refer to the graphic file for
correct placement of sawteeth or half circles.
ACC refers to accuracy of location of faults and folds.
1=accurate
2=approximate
4=concealed
DIR refers to sense of relative movement on normal or oblique slip faults or
to sense of oblique slip on thrust faults.
1=right lateral
2=left lateral
POS refers to position of the axial surface of folds.
1=upright or inclined
2=overturned
The stru_pnt coverage includes points that are orientation of layering in
metamorphic rocks. The coverage consists of the following items:
GEOCODE
STK
DIP
POS
ACC
GEOCODE refers to the type of surface for which orientation is given. The
only possible value for GEOCODE in the stru_pnt coverage is "FOLIATION" (i.e.,
layering in metamorphic rocks).
STK refers to strike of layering in metamorphic rocks.
DIP refers to dip value for layering in metamorphic rocks. NOTE: The info
files give the azimuth for strike and the value for dip; the direction of dip is
not readily apparent from the info files. The user should refer to the plotted
graphic to determine direction of dip.
POS refers to position of the layering in metamorphic rocks.
1=inclined
4=vertical
ACC refers to accuracy in terms of whether the orientation of layering was
measured or estimated.
1=measured
2=estimated (no instances mapped in the Sedan quadrangle)
The data_net coverage includes lines that form the quadrangle boundary and
lines of section (three cross sections are part of the printed version of this
map, which is in press). The coverage consists of the following items:
GEOCODE
XTA
GEOCODE refers to the type of line. The value for GEOCODE in the data_net
coverage is one of the following: "BOUND" and "Xsection"
XTA refers to the specific line of section: A-A', B-B', or C-C'.
The data_pnt coverage includes points that are locations for gravel pits,
test wells, and springs. The coverage consists of the following item:
GEOCODE
GEOCODE refers to the type of feature located. The value for the GEOCODE in
the data_pnt coverage is one of the following: "GRAVEL PIT", "OIL TEST"
(Robinson Ranch no. 1 Amoco prod. and Wilsall no. 1 Statescat drilling), and
"SPRING."
The pnt_sym coverage includes points that locate arrows for faults and folds
and U and D symbols for faults. (NOTE: On this map the "U" indicates the
APPARENT upthrown side of a thrust fault and "D" the APPARENT downthrown side.
Please refer to the graphic file for correct placement of sawteeth that indicate
the upper plate.) The coverage consists of the following item:
TYP
The value for TYP in the pnt_sym coverage is one of the following:
"ANTICLINE," "ANTI_OVER," "LL/SLIP," "NORMAL/D," "NORMAL/U," "PLUNGE,"
"RL/SLIP," "SYNCLINE," "SYNC_OVER." (NOTE: NORMAL/D and NORMAL/U as used here
also includes "U" and "D" on thrust faults.)
Distribution_Information:
Distributor:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: U.S. Geological Survey, Geologic Division,
Central Publications Group
Contact_Person: Nancy Shock
Contact_Position: Digital Map Specialist
Contact_Address:
Address_Type: mailing address
Address: U.S. Geological Survey, MS902, Box 25046, Denver Federal
Center
City: Lakewood
State_or_Province: CO
Postal_Code: 80225
Country: USA
Contact_Voice_Telephone: (303) 236-7684
Contact_Electronic_Mail_Address: nshock@usgs.gov
Resource_Description: Geologic Investigations Series I-2634, Geologic
map of the Sedan quadrangle, Gallatin and Park Counties, Montana
Distribution_Liability: Any use of trade, product, or firm names is for
descriptive purposes only and does not imply endorsement by the U.S. Government.
Although this data set has been used by the U.S. Geological Survey, no warranty,
expressed or implied, is made by the USGS as to the accuracy and functioning of
the data set and related material nor shall the fact of distribution constitute
any such warranty, and no responsibility is assumed by the USGS in connection
therewith.
Standard_Order_Process:
Digital_Form:
Digital_Transfer_Information:
Format_Name: ARCE
Format_Version_Number: 7.2.1
File_Decompression_Technique: gzipped tar file
Digital_Transfer_Option:
Online_Option:
Computer_Contact_Information:
Network_Address:
Network_Resource_Name:
Fees: No cost for the digital files.
Technical_Prerequisites: ARC/INFO 7.2.1
Metadata_Reference_Information:
Metadata_Date: 19981112
Metadata_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Nancy Shock
Contact_Organization: U.S. Geological Survey, Geologic Division,
Central Publications Group
Contact_Position: Digital Map Specialist
Contact_Address:
Address_Type: mailing address
Address: : U.S. Geological Survey, MS902, Box 25046, Denver
Federal Center
City: Lakewood
State_or_Province: CO
Postal_Code: 80225
Country: USA
Contact_Voice_Telephone: (303) 236-7684
Contact_Electronic_Mail_Address: nshock@usgs.gov
Metadata_Standard_Name: FGDC Content Standard for Digital Geospatial
Metadata
Metadata_Standard_Version: 199806
Metadata_Access_Constraints: None
Metadata_Use_Constraints: None