GeMS validation of OF-20-02_AgateMountain.gdb

File written by GeMS_ValidateDatabase.py, version of 11/28/2023
Wed Jun 12 10:20:46 2024
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Database path: C:\Data\Pangaea\CGS\2020 Agate Mountain\OF-20-02_AgateMountain\OF-20-02_AgateMountain_Publication\OF-20-02_AgateMountain_Database\OF-20-02_AgateMountain.gdb
Output directory: C:\Data\Pangaea\CGS\2020 Agate Mountain\Validation
Metadata file: None
Check embedded metadata: False
Skip topology check: False
Refresh GeoMaterialDict: True
Delete extra rows in Glossary and DataSources: False
Compact GDB: True

This database is LEVEL 3 COMPLIANT.

Check Metadata option was skipped. Be sure to have prepared valid metadata and check this option to produce a complete report.
This file should be accompanied by OF-20-02_AgateMountain.gdb-ValidationErrors.html and a metadata summary from mp in the same directory.

If this database will be submitted to the NGMDB, it also needs to be accompanied by a reviewed Geologic Names report that includes identification of any suggested modifications to Geolex. Use the Geologic Names Check tool to generate that report or provide other documentation of a review.

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Contents

Compliance Criteria
Warnings
Content not specified in GeMS schema
Occurrence of MapUnits in DMU, feature datasets, or geopackage tables
Contents of Nonspatial Tables
DataSources
DescriptionOfMapUnits
Glossary
MiscellaneousMapInformation
Database Inventory

Compliance Criteria

LEVEL 1

Criteria for a LEVEL 1 GeMS database are: Databases with a variety of schema may meet these criteria. This script cannot confirm LEVEL 1 compliance.

LEVEL 2--MINIMALLY COMPLIANT

A LEVEL 2 GeMS database is accompanied by a peer-reviewed Geologic Names report, including identification of suggested modifications to Geolex, and meets the following criteria:
2.1 Has required elements: nonspatial tables DataSources, DescriptionOfMapUnits, GeoMaterialDict; feature dataset GeologicMap with feature classes ContactsAndFaults and MapUnitPolys PASS
2.2 Required fields within required elements are present and correctly defined PASS
2.3 All MapUnitPolys and ContactsAndFaults based feature classes obey Level 2 topology rules: no internal gaps or overlaps in MapUnitPolys, boundaries of MapUnitPolys are covered by ContactsAndFaults PASS
2.4 All map units in MapUnitPolys have entries in DescriptionOfMapUnits table PASS
2.5 No duplicate MapUnit values in DescriptionOfMapUnit table PASS
2.6 Certain field values within required elements have entries in Glossary table PASS
2.7 No duplicate Term values in Glossary table PASS
2.8 All xxxSourceID values in required elements have entries in DataSources table PASS
2.9 No duplicate DataSources_ID values in DataSources table PASS

LEVEL 3--FULLY COMPLIANT

A LEVEL 3 GeMS database meets these additional criteria:
3.1 Table and field definitions beyond Level 2 conform to GeMS schema PASS
3.2 All MapUnitPolys and ContactsAndFaults based feature classes obey Level 3 topology rules: No ContactsAndFaults overlaps, self-overlaps, or self-intersections. PASS
3.3 No missing required values PASS
3.4 No missing terms in Glossary PASS
3.5 No unnecessary terms in Glossary PASS
3.6 No missing sources in DataSources PASS
3.7 No unnecessary sources in DataSources PASS
3.8 No map units without entries in DescriptionOfMapUnits PASS
3.9 No unnecessary map units in DescriptionOfMapUnits PASS
3.10 HierarchyKey values in DescriptionOfMapUnits are unique and well formed PASS
3.11 All values of GeoMaterial are defined in GeoMaterialDict. GeoMaterialDict is as specified in the GeMS standard PASS
3.12 No duplicate _ID values PASS
3.13 No zero-length, whitespace-only, or bad null values PASS

Warnings

There are 11 warnings

Content not specified in GeMS schema

Some of the extensions to the GeMS schema identified here may be necessary to capture geologic content and are entirely appropriate. Please document these extensions in metadata for the database, any accompanying README file, and (if applicable) any transmittal letter that accompanies the dataset. Other extensions may be intermediate datasets, fields, or files that should be deleted before distribution of the database.

Fields


Tables


CorrelationOfMapUnits
CrossSectionA
CrossSectionB
GenericPoints
GenericPointsAnno
FaultsAnno
MapUnitPolysAnno
OrientationPointsAnno
MapUnitPolysAnnoLeaders
GeologicLinesAnno
GeochronPointsAnno
CMULines
CMULinesAnno
CMUMapUnitPolysAnno
CSA_CartoLines
CSA_DH
CSA_DHTrace
CSA_FltMvmt
CSA_CartoLinesAnno
CSA_DHAnno
CSA_DHTraceAnno
CSAMapUnitPolysAnno
CSB_CartoLines
CSB_CartoLinesAnno
CSB_DH
CSB_DHAnno
CSB_DHTrace
CSB_FltMvmt
CSBMapUnitPolysAnno

Occurrence of MapUnit in DMU, feature datasets, or geopackage tables

MapUnit DescriptionOfMapUnits GeologicMap CrossSectionB CorrelationOfMapUnits CrossSectionA
PEbs X X -- X X
PEgp X X -- X --
PEab X X -- X --
Qa1 X X -- X --
PEPP X -- X X X
PPmm X X -- X X
Ybd X -- -- X --
PEtcl X X -- X --
Ya X X -- X --
Yd X -- -- X --
PEatc X -- -- X X
PEwm X X X X X
YXu X -- X X X
PEbbam X -- X X --
YXfg X X -- X --
Ml X X X X --
PEbb X X X X --
YXg X X -- X --
Dd X X X X --
Nwt X X X X --
PPmmc X X -- X --
Qg X X -- X --
YXgg X X -- X --
af X X -- X --
Yi X X -- X --
Pb X X -- X --
Yp X X -- X --
PEa X X X X X
Qgo X X -- X --
Ygp X X -- X --
Qls X X -- X --
Qsw X X -- X --
PEam X X X X X
Qdf X X -- X --
Qa2 X X -- X --
PEal X X X X --
PEtc X X X X --
Oh X X X X --
PEat X X -- X --
Qau X X -- X --
Of X X X X --
Om X X X X --

Contents of Nonspatial Tables

DataSources

OBJECTIDSourceNotesURLDataSources_ID
3This compilationNoneNoneDAS1
4DictionaryNonehttps://www.dictionary.com/DICT1
2Federal Geographic Data Committee [prepared for the Federal Geographic Data Committee by the U.S. Geological Survey], 2006, FGDC Digital Cartographic Standard for Geologic Map Symbolization: Reston, Va., Federal Geographic Data Committee Document Number FGDC-STD-013-2006, 290 p., 2 plates.Nonehttps://ngmdb.usgs.gov/fgdc_gds/geolsymstd.phpFGDC-STD-013-2006
6GeMS standardNonehttps://pubs.er.usgs.gov/publication/tm11B10GEMS1
5Geologic dictionaryNonehttps://geology.com/geology-dictionary.shtmlGEODICT1
9Personal uranium drill hole data collectionDonated to Arthur Lakes Library at Colorado School of Mineshttps://library.mines.edu/GRIGSBY
7The National MapNonehttps://apps.nationalmap.gov/downloader/USGS1

DescriptionOfMapUnits

OBJECTIDMapUnitNameFullNameAgeDescriptionHierarchyKeyParagraphStyleLabelSymbolAreaFillRGBAreaFillPatternDescriptionDescriptionSourceIDGeoMaterialGeoMaterialConfidenceDescriptionOfMapUnits_ID
49NoneSURFICIAL UNITSSURFICIAL UNITSNoneColors are designated according to the Munsell soil color charts (Munsell Color Company, 1991). Description of soil-carbonate morphology is after Machette (1985) and Birkeland (1999).01DMUHeading1NoneNoneNoneNoneDAS1NoneNoneDMU01
50NoneHUMAN-MADE DEPOSITSHUMAN-MADE DEPOSITSNoneNone01-01DMUHeading2NoneNoneNoneNoneDAS1NoneNoneDMU02
51afArtificial fillArtificial fillUppermost HoloceneArtificial fill includes riprap, fill, and refuse placed during construction of roads, railroads, buildings, dams, and landfills. The unit generally consists of clay, silt, sand, and rock fragments. Extensive areas of artificial fill may exist in residential and commercial developments in the map area; however, some fill deposits are typically less than 1.5 m thick and may be difficult to delineate. Fill materials can vary in particle size and may locally include refuse of many types including household and industrial waste. Artificial fill may be subject to settlement, slumping, and erosion if not adequately compacted or emplaced. The unit is as much as 6 m thick.01-01-01DMUUnit1afaf255-255-255NoneDAS1"Made" or human-engineered landHighDMU03
52NoneALLUVIAL DEPOSITSALLUVIAL DEPOSITSNoneNone01-02DMUHeading2NoneNoneNoneNoneDAS1NoneNoneDMU04
53Qa1Alluvium oneAlluvium oneUpper to Middle HoloceneOlive brown to dark olive-brown (2.5Y 4/3 to 2.5Y 3/3) silt, fine sand, and gravel. Sand particles are predominantly quartz with lesser amounts of feldspar and opaque minerals. Deposits are unstratified to weakly stratified. Gravel lenses and dispersed gravels are present locally; gravel lenses are up to 5 cm thick. Clasts in gravel lenses are <2.5 cm in diameter. No visible secondary carbonate nodules were observed but the matrix does effervesce locally in response to dilute hydrochloric acid. In the northern part of the mapped area, a basal, matrix supported, weakly stratified gravel bed is locally exposed. In this area, the uppermost silt to fine sand is about 1 m thick. The gravel clasts are subangular to subround, and up to a 6 cm diameter. The unit underlies the most recently active channels of Agate, Little Agate, Badger, and Wagon Tongue creeks. It is hydraulically connected to streams, and groundwater is typically very close to the surface. The unit may be a source of sand and gravel. Areas mapped as unit Qa1 may be prone to flooding and collapse. Thickness may be as much as 5 m.01-02-01DMUUnit1Qa1Qa1254-252-226NoneDAS1Alluvial sedimentHighDMU05
54Qa2Alluvium twoAlluvium twoMiddle to Lower HolocenePoorly to moderately stratified, silt to fine sand. Sand particles are predominantly quartz with lesser amounts of feldspars and opaque minerals. Soil development includes an uppermost A horizon and weakly developed B and Bk horizons. The A horizon is approximately 30 to 36 cm thick and is olive-gray (5Y 4/2). The B horizon is an approximately 46 cm-thick, with weak prismatic structure that is dark olive-gray (5Y 3/2). The lowermost soil unit is a Bk horizon with Stage I+ to II carbonate development that contains few to common nodules and is very dark grayish brown (2.5Y 3/2). The unit underlies areas directly adjacent to unit Qa1 along Agate, Little Agate, Badger, and Wagon Tongue creeks. Terrace surfaces underlain by unit Qa2 are 1 to 1.5 m above adjacent modern channels. The unit is a potential source of sand and gravel. Areas underlain by unit Qa2 may be prone to flooding and collapse. The unit is likely as much as 2 m thick.01-02-02DMUUnit1Qa2Qa2254-246-136NoneDAS1Alluvial sedimentHighDMU06
55QauAlluvium, undividedAlluvium, undividedHolocene and Upper PleistoceneDeposits are unstratified to moderately stratified, silty sand to matrix supported, poorly sorted gravel. Gravel clasts are angular to subangular and reach up to 13 cm in diameter. Color and composition of clasts are dependent on source material and therefore vary across the quadrangle. In general, colors are typically pale brown (10YR 6/3) to dark yellowish-brown (10YR 4/4). Unit Qau underlies unnamed ephemeral streams. Sediments are usually deposited during high-energy, high-volume storm events (Barkmann and others, 2018). The unit may be correlative with units Qai, Qaio, and Qac of Barkmann and others (2018) and unit Qac of Wallace and Keller (2003). The unit may transmit limited groundwater. Areas underlain by unit Qau may be prone to flooding, collapse, and/or debris flow. Estimated thickness locally exceeds 1.5 m or greater (Barkmann and others, 2018).01-02-03DMUUnit1QauQau254-249-194NoneDAS1Sand and gravel of unspecified originMediumDMU07
56QgGravelGravelHolocene and Upper PleistocenePoorly sorted silt to gravel. Composition of clasts and color of deposits vary by location within the mapped area, largely due to differences in source area geology. Exposures are rare and outcrops were not observed. There are multiple terrace levels throughout the mapped area. Generally, the lower terrace surfaces are 2 to 12 m above adjacent modern stream channels and higher terrace surfaces are 5 to 20 m above adjacent modern stream channels. Terraces underlain by unit Qg extending from Kaufman Ridge on the west side of the mapped area are typically capped by clasts of metamorphic rocks, granitic rocks, vein quartz, and clasts derived from the Antero Formation that are 3 to 6 cm in diameter. Clasts are angular to subround. Carbonate rind thickness is 2 mm or less; some clasts may be reworked from older deposits. The topmost 0.3 m of the unit may locally include reworked silt to medium sand of possible eolian origin. Two terrace levels were identified. The lower gravel-capped surfaces are approximately 6 to 10 m above ephemeral streams while upper surfaces are 15 to 20 m above ephemeral streams. The unit is less than 7 m thick. Terraces underlain by unit Qg in the northeastern part of the mapped area are capped by brown to black andesitic clasts, and red, gray, and brown volcanic breccia clasts that are up to 15 cm in diameter. Clasts are subangular to subround. The matrix is composed of silt to medium sand. Discontinuous to continuous carbonate rinds are present on clasts and are up to 1 mm thick. Some of these clasts may have been reworked from older deposits. Surfaces are approximately 4 to 5 m above modern ephemeral streams. The unit is up to 2 m thick. Two soil pits were hand excavated within the mapped area: Site AG 1 located at SW ¼ SE ¼ sec. 36, T 13 S, R 76 W to a depth of 107 cm and Site AG 2 at SE ¼ SE ¼ sec. 36, T. 13 S., R. 76 W to a depth of 97 cm. The deposit at AG 1 is predominantly unstratified to well stratified, clast-supported pebble gravel. Clasts are subround to round, varying in color from red, light-grey, dark-grey, and black. They may reach up to 3 cm in diameter and are andesitic and basaltic in composition. From 0 to 84 cm depth, the unit is clay to medium sand. Coarser sand lenses are up to 2 to 3 cm thick. From 84 to 107 cm below ground surface, sand content increases and grains are coarser. Below 84 cm, the unit is silt to medium sand, with coarse sand and pebble gravel lenses up to 5 cm thick. The following description was provided by Laura Craven, Natural Resource Conservation Service (personal commun., 2019) : A horizon, 0 to 20 cm, brown (10YR 4/3) gravelly loamy sand, noneffervescent; Bw1 horizon, 20 to 36 cm, brown (10YR 4/3) very gravelly loamy sand, weak fine subangular structure, noneffervescent; Bw2 horizon, 36 to 65 cm, yellowish-brown (10YR 5/5) very gravelly sand, weak fine subangular blocky structure, noneffervescent; Bk1 horizon, 65 to 83 cm, yellowish-brown (10YR 5/6) very gravelly sand, weak medium subangular blocky structure, 2 percent fine carbonate masses, slight effervescence; Bk2 horizon, 83 to 87 cm, yellowish brown (10YR 5/6) gravelly sandy loam, weak medium blocky structure, 30 percent coarse carbonate masses, violent effervescence; C horizon, 87-100 cm, yellowish-brown (10YR 5/4) very gravelly sand, single grain structure, noneffervescent. The deposit at AG 2 is capped by approximately 25 cm of homogenous, stiff, silt to fine sand. This section is similar in texture and appearance to eolian deposits. Beneath is approximately 22 cm of clast supported pebble gravel. Clast lithology is predominantly andesitic with lesser amounts of chert. Clasts are subround to round and up to 4 to 5 cm in diameter. From 48 to 83 cm below ground surface, a Stage II+ to III Bk horizon is present. Carbonate rinds on clasts are continuous and less than 1 mm in thickness. Gravel clasts coarsen with increasing depth below ground, up to 10 cm in diameter. From 83 to 97 cm below ground surface, the unit consists of silt to medium sand. The following description was provided by Laura Craven and Sara Mack, Natural Resource Conservation Service (personal commun., 2019): A horizon, 0 to 10 cm, brown (10YR 5/3) sandy loam, weak fine granular structure, very slight effervescence; Bt1 horizon, 10 to 34 cm, yellowish-brown (10YR 5/4) sandy clay loam, moderate fine prismatic structure, noneffervescent; Bt2 horizon, yellowish-brown (10YR 5/4) sandy clay loam, weak fine subangular blocky structure, noneffervescent; Bk horizon, 50 to 78 cm, brown (10YR 5/2), very gravelly coarse sandy loam, weak medium subangular blocky structure, 50 percent extremely coarse irregular carbonate masses, strong effervescence; C horizon, 78 to 100 cm, grayish-brown (10YR 5/2), very gravelly sand, single grain structure, strong effervescence. Two samples were collected at AG 1 and AG 2 for optically stimulated luminescence dating. The first sample, AG 1, was taken at an elevation of approximately 2789 m at a depth of 97 cm in fine to medium sand; AG 2 was taken at approximately 2792 m at a depth of 97 cm in medium to coarse sand. Age estimates of 11,395 ± 1,230 at AG 1 and 8,595 ± 840 at AG 2 indicate both sampled deposits are Early Holocene in age. Unit Qg may be correlative to unit Qgo by Barkmann and others (2018). Segments of the unit are mapped as terraces of differing ages by various authors. Stark and others (1949) mapped part of the unit as “Como Surface”, which they inferred to be Pre-Illinoian in age (greater than 200 ka). De Voto (1971) identified parts of the surface as “Terrace A”, which he inferred to be Holocene, and “Terrace B”, which he inferred to be Wisconsin (80 to 11 ka). All previous age interpretations were made based on the basis of heights above stream level and degree of soil development. Landslides and debris flow initiation are possible at or near the unit’s contact with underlying, weaker bedrock units. The unit is a potential source of gravel.01-02-04DMUUnit1QgQg254-252-226602 gravel 255-0-0DAS1Alluvial sediment, mostly coarse-grainedHighDMU08
57QgoOld gravelOld gravelLower Pleistocene to Upper PleistocenePoorly sorted gravel, sand, silt, and clay. Gravel occurs as a mantle over bedrock. Cobbles and boulders are composed of andesite and basalt that are very similar in composition to clasts from units :am and :bs. Clasts are up to 2 m in diameter, and are angular to rounded. They occur in a matrix of tan sand, silt, clay, and pebbles of andesite and basalt. The cobbles and boulders have weathering rinds 0.5 to 5 cm thick. They are partially to entirely covered by carbonate and are typically <2 mm thick but can be up to 1 cm thick. Deposits that are higher in the landscape have thicker carbonate rinds and thus are likely older than deposits lower in the landscape. Gravel-capped surfaces underlain by the unit range between 40 and 166 m above modern channels as measured using lidar imagery. Multiple terrace surface heights and different degrees of carbonate rind development likely indicate there was more than one period of deposition of the unit during the Pleistocene. The terrace levels and relationships are complex within the mapped area and it is difficult to identify which major drainage individual terraces are associated with or if they were deposited by previously existing fluvial systems. Therefore, the terraces are mapped as the same unit. The unit was mapped as the “Badger Creek pediment” by De Voto (1971) and the “Badger Creek surface” by Stark and others (1949). On the basis of height above modern stream channels, Stark and others (1949) assigned the unit an age of late Pliocene. Scott (1965) assigned it an age of Early Pleistocene on the basis of its relationship with lower terraces along Badger Creek. The unit is likely not a good source of sand and gravel due to weathering of clasts. Rockfall is a hazard on steep slopes. Unit thickness is approximately 2 to 11 m.01-02-05DMUUnit1QgoQgo254-246-136602 gravel 56-168-0DAS1Alluvial sediment, mostly coarse-grainedHighDMU09
58NoneALLUVIAL AND MASS-WASTING DEPOSITSALLUVIAL AND MASS-WASTING DEPOSITSNoneNone01-03DMUHeading2NoneNoneNoneNoneDAS1NoneNoneDMU10
59QswSheetwash and debris-flow deposits, undividedSheetwash and debris-flow deposits, undividedHolocene to Upper PleistoceneThe unit consists of sheetwash and debris-flow deposits that grade into each other laterally, but are not geomorphically distinct or aerially large enough to map as individual deposits. Generally, the unit is poorly to weakly stratified and poorly sorted. An exposure in sec. 3, T. 15 S., R. 75 W. consists of angular to subangular clasts up to 20 cm in diameter, with some clasts exceeding 30 cm. Soil development ranges across the quadrangle, from weakly developed Bt and non-existent Bk horizons, to as much as Stage II to II+ carbonate development in the Bk soil horizon. At this exposure, carbonate rinds are continuous and can be up to 2 mm thick. Throughout the mapped area, sheetwash deposits are generally composed of matrix supported gravel deposits with angular clasts. Where debris-flow deposits are interbedded with sheetwash alluvium, bedrock clasts are as much as 3 cm in diameter. Color and composition of the unit varies depending on source area material but color may vary between light yellowish-brown (2.5Y 6/3) and yellowish-brown (10YR 5/4). Areas underlain by unit Qsw may be prone to flooding, collapse, and/or debris flow. The unit is typically up to 1 m thick but may be thicker locally.01-03-01DMUUnit1QswQsw254-246-136607 sand 255-0-0DAS1Silt and clay of unspecified originMediumDMU11
60QdfDebris flow depositsDebris flow depositsHolocene to Lower PleistocenePoorly sorted, matrix- to clast-supported gravel. The matrix is commonly mud to medium sand. Clasts are typically angular to subangular and derived from local bedrock units. Clasts can exceed 0.3 m in diameter. Some debris flow deposits along Wagon Tongue Creek have a well-developed Bk horizon that is approximately 0.3 m thick with Stage III carbonate development. Clasts have continuous carbonate rinds, which can exceed 1 mm in thickness. The Bk horizon may be thicker locally. Younger deposits have less developed soils and carbonate rinds that are thinner or not present. Debris flow deposits may be interbedded with alluvial deposits throughout the mapped area. Areas underlain by debris flow deposits may be prone to future debris-flow events, flooding, and/or collapse. Thickness is estimated to be about 7.5 m.01-03-02DMUUnit1QdfQdf254-228-132502 periglacial 0-0-0DAS1Debris flows, landslides, and other localized mass-movement sedimentHighDMU12
61NoneMASS-WASTING DEPOSITSMASS-WASTING DEPOSITSNoneNone01-04DMUHeading2NoneNoneNoneNoneDAS1NoneNoneDMU13
62QlsLandslide depositsLandslide depositsHolocene to Upper PleistoceneUnit is composed of unsorted gravel clasts, bedrock fragments, and soil clods. All deposits are mapped in the southeast corner of the quadrangle. Landslides occur at or near the contact of unit Qgo and the underlying, soft Wagontongue and Antero formations. Deposits were identified and mapped on the basis of hummocky topography typical of landslide deposit morphology. Many deposits were obscured by aspen groves. In these locations, lidar was used to map their extent. This unit is not well exposed in the mapped area. Landslides are predominantly translational and rotational. Landslide deposits and areas with similar bedrock units may be prone to future slope failures. Deposits may be up to 6 m thick.01-04-01DMUUnit1QlsQls254-228-132605 breccia 0-0-0DAS1Debris flows, landslides, and other localized mass-movement sedimentHighDMU14
63NoneBEDROCK GEOLOGYBEDROCK GEOLOGYNoneBedrock unit classifications follow those of Carpenter and others (2016). Chemical classification of igneous rocks is that of Le Bas and others (1986) and Frost and others (2001, 2008, 2011). Geologic terms follow the definitions of Neuendorf and others (2005).02DMUHeading1NoneNoneNoneNoneDAS1NoneNoneDMU15
64NwtWagontongue FormationWagontongue FormationMioceneLight gray, tan, and light brown interbedded conglomerate, sandstone, and mudstone that is cemented with calcite and silica. Two lithofacies are common. Clast-supported conglomerate and conglomeratic sandstone contains granules, pebbles, cobbles, and sand in a matrix of white, microcrystalline calcite, causing the rock to resemble concrete. Clasts are rounded to subangular. Beds are 15 to 60 cm thick. Some trough cross-bedding is present. Matrix-supported conglomerate, conglomeratic sandstone and conglomeratic mudstone is massive with granule- to boulder-sized gravel suspended in a matrix of sand and/or mud. Gravel clasts are rounded to angular. These massive deposits are up to 3 m thick. Where well-exposed, this facies has root traces and carbonate-rich layers indicative of soil development. West of Badger Creek, the gravel clasts in the Wagontongue Formation consist mainly of K-feldspar, limestone, quartz sandstone, vein quartz, chert, vitrophyre, gneiss, and a distinctive light bluish gray siliceous tuff. Near Badger Creek, clasts of andesite and basalt are also common. East of Badger Creek, the proportion of basalt and andesite clasts increases in the eastward direction while the proportion of other lithologies decreases. Much of the formation is poorly lithified and poorly exposed. It weathers to gently sloping hills in the southern half of the quadrangle. The two best outcrops are on the northeast ends of ridges in sec. 31 and 32, T. 14 S., R. 75 W. DeVoto (1971) reported the occurrence of fossil mammals of early Miocene age (Burdigalian Age, approximately 16 to 20 Ma) in the formation. An angular unconformity separates the Wagontongue Formation from the underlying Antero Formation and Gribbles Park Tuff. It is prone to producing debris flows and landslides, and rockfall is a hazard on slopes greater than 30 degrees. A complete section of the formation is not exposed on the quadrangle, but it is at least 120 m thick.02-01DMUUnit1NwtNwt233-202-160NoneDAS1ConglomerateMediumDMU16
65PEgpGribbles Park TuffGribbles Park TuffOligocene Light-gray to gray to pinkish-gray, fine-grained rhyolitic welded tuff. Sanidine, plagioclase, biotite and dark gray to brown lithic fragments are locally visible. The tuff is exposed along the road in sec. 10, T. 15 S., R. 75 W., sparsely in the northeast part of adjoining sec. 9, and more extensively along the southeast part of Agate Mountain in sec. 4, T. 15 S., R. 75 W. Samples of the Gribbles Park Tuff from the upper Arkansas River Valley yielded 40Ar/39Ar sanidine ages of 32.98 +/- 0.14 Ma and 32.91 +/- 0.11 Ma (McIntosh and Chapin, 2004). These authors correlated the Gribbles Park Tuff with the upper Bonanza Tuff, and determined its source to be the Bonanza caldera. The tuff unconformably overlies the Antero Formation. Rockfall is a hazard on slopes greater than 30 degrees. The tuff is approximately 30 m in thickness.02-02DMUUnit1:gpPegp248-156-50NoneDAS1Felsic-composition pyroclastic flowsHighDMU17
66PEaAntero FormationAntero FormationOligoceneThe Antero Formation was described in the adjoining Antero Reservoir NE quadrangle (Barkmann and others, 2018) as consisting of five different lithofacies. All five of the facies were observed in the mapped area. Four of these were mapped as one unit and are described here. Two additional lithofacies, limestone and welded tuff, were mapped separately and are described below. The tuffaceous shale consists of white to light tan, poorly consolidated, siltstone, mud shale, and clay shale. Laminations are common, and climbing ripples are present. Vitric shards and biotite crystals are present at most localities. The clast-supported sandstone and conglomerate is a white to light-gray tuffaceous sandstone to conglomerate with abundant vitric shards, biotite crystals, feldspar crystals, and granule- to pebble-sized pumice clasts. Some outcrops contain andesite pebbles. Bedding is thin to thick, with coarser deposits generally having thicker bedding. Climbing ripples, reactivation surfaces, heavy-mineral layers, and soft sediment deformation occur at some localities. Field-based X-ray fluorescence analysis of the heavy mineral layers yielded 2-3% titanium, 1000-1500 ppm vanadium, and elevated levels of iron. In the southernmost part of sec. 20, T. 14 S., R. 75 W., large-scale cross-beds, approximately 6 m thick, are present. These are interpreted as Gilbert delta deposits. Paleocurrent measurements corrected for tectonic dip yield an average strike of 57 degrees and dip of 30 degrees SE. The matrix-supported conglomerate consists of andesite pebbles and cobbles in a matrix of white granular coarse sandstone that is about 80% vitric shards and pumice, and 20% crystals of biotite and feldspar. It occurs as thick beds that are internally massive. The vitric tuff is white to light tan and massive, with clasts of tuffaceous siltstone and pumice up to 15 cm in diameter. It is poorly lithified, and is about 4 to 6 m thick. McIntosh and Chapin (2004) reported an 40Ar/39Ar average age of 33.76 +/- 0.10 Ma for tuff samples from the Antero Formation. They correlated it with the Badger Creek Tuff, and determined its source to be the Mt. Aetna cauldron. On the west side of the Antelope Creek and Little Agate Creek faults, its contact with the underlying Tallahassee Creek Conglomerate appears to be conformable and gradational. The contact was placed at the base of the lowest occurrence of white vitric ash- and pumice-rich sediment. However, deposits of Tallahassee Creek-like boulders of augen gneiss, granite, Wall Mountain Tuff, and Leadville Limestone up to 1 m in diameter were found interbedded with Antero-like tuffaceous deposits in the lower part of the Antero Formation. On the east side of the Agate Creek and Little Agate Creek faults, the formation unconformably overlies Eocene volcanic rocks and Proterozoic intrusive igneous and metamorphic rocks. Rockfall is a hazard on slopes greater than 30 degrees in the limestone and matrix-supported conglomerate lithofacies. On the west side of the Agate Creek and Little Agate Creek faults, the Antero Formation is up to 264 m thick. On the east side, its maximum thickness is 60 m.02-03DMUUnit1:aPea232-183-124NoneDAS1Sedimentary and extrusive igneous materialHighDMU18
67PEalAntero Formation limestone faciesAntero Formation limestone faciesOligoceneTan to light- brown to light-gray micritic limestone to shaley limestone. Shaley limestone is thinly bedded, easily parted, and fissile. Occasional rounded to subrounded quartz detritus, volcanic ash, calcareous algae, small wood fragments, and other lacustrine fossil fragments were observed. In some places, the limestone is oolitic. Limestone beds average 15 to 20 cm in thickness and bedding planes are well-developed. Partial to complete recrystallization and silicification are present. The most common exposures are near the Proterozoic outcrops where the limestone developed in shallow waters proximal to the lakeshore. However, one of the better exposures occurs along Agate Creek in the southeast quarter of sec. 16, T. 14 S., R. 75 W. On slopes greater than 30 degrees, rockfall is a hazard. The thickness in surface outcrops is approximately 3 m or less.02-04DMUUnit2:alPeal251-188-123NoneDAS1LimestoneHighDMU19
68PEatAntero Formation welded tuff faciesAntero Formation welded tuff faciesOligocenePinkish-orange, densely welded, vitric tuff. Though numerous quartz-filled voids are present, no phenocrysts and few pumice lapilli were observed. The unit contains two flows, each of which is about 1.2 m thick. The base of each flow has a lag of angular cobbles of silicified limestone. Only one small outcrop of welded tuff was found in sec. 31, T. 13 S., R. 75 W., in the north-central part of the quadrangle. Thickness of the unit is about 2.4 m.02-04-01DMUUnit2:atPeat241-100-63NoneDAS1Pyroclastic flowsHighDMU20
69PEtcTallahassee Creek ConglomerateTallahassee Creek ConglomerateEoceneVaricolored tuffaceous conglomerate, sandstone, and limestone that is generally tan, yellowish-tan, orangish-tan, or gray. Conglomerate, sandstone, and conglomeratic sandstone occur in beds approximately 1 to 1.5 m thick. Sand is medium- to coarse-grained and contains a mixture of quartz, feldspar, and rock fragments. Gravel clasts include pebbles, cobbles, and boulders of andesite, chert, quartzite, granite, tuff, and vitrophyre. The largest boulders are approximately 1.5 m in diameter. The limestone facies was mapped separately and is described below. The Tallahassee Creek Conglomerate is poorly exposed in an area in the northwest corner of the quadrangle. West of the Agate Creek fault and the Little Agate Creek fault, it unconformably overlies the undivided Minturn and Maroon formations, and possibly the Echo Park Alluvium. East of these faults, it is not present. Falling rocks are a hazard on slopes greater than 30 degrees. The formation is about 30 m thick on the quadrangle.02-05DMUUnit1:tcPetc253-209-160NoneDAS1Sedimentary and extrusive igneous materialHighDMU21
70PEtclTallahassee Creek Conglomerate, limestone faciesTallahassee Creek Conglomerate, limestone faciesEoceneLight gray, finely crystalline limestone that is extensively silicified in places. The limestone occurs in beds approximately 15-30 cm thick, and contains lacustrine algae (Chara). Sinkholes are associated with the limestone, and rockfall is a hazard on slopes greater than 30 degrees. Thickness is approximately 3 m.02-05-01DMUUnit2:tclPetcl251-188-123NoneDAS1LimestoneHighDMU22
71PEatcAntero and Tallahassee Creek Formations, undifferentiatedAntero and Tallahassee Creek Formations, undifferentiatedEoceneVolcaniclastic sandstone, conglomerate, siltstone, and shale with minor limestone and welded tuff. Thickness is approximately 60 to 300 m. Shown only on cross-section.02-06DMUUnit1:atcPeatc235-179-62NoneDAS1Sedimentary and extrusive igneous materialHighDMU23
72PEbsTrachybasaltTrachybasaltEoceneDense, black, fine-grained volcanic rock exposed in the northeastern part of the map area primarily in sec. 11, T 14 S., R. 75 W. Two isolated hills exposed in this area weather along the flanks into talus with flat surfaces that alter to a light-gray to gray to light-brown color. Thin sections contain anhedral to subhedral olivine and augite along with abundant subhedral plagioclase. The plagioclase laths are partially flow aligned and commonly twinned. Whole rock analysis of one sample indicates a composition of 47.7% SiO2, 15.9% Al2O3, 12.4% Fe2O3, 8.86% CaO, 5.71% MgO, 3.38% Na2O, and 2.06% K2O. This geochemistry plots in the trachybasalt field on the total alkali-silica diagram of LeBas and others, 1986. These results are very similar to results reported by Epis and Chapin (1974) for the upper member of the Thirtynine Mile Andesite, and the trachybasalt on this quadrangle may be correlative with it. The trachybasalt disconformably overlies the breccia of Buffalo Gulch and the middle andesite series. Sample JT44, taken in the NW ¼ sec. 11, T. 14 S., R. 75 W., yielded an 40Ar/39Ar date of 34.95+/-0.09 Ma. This date is older than expected, given the stratigraphic position of unit :bs. It was collected in an area where hydrothermal alteration is common, so perhaps the sample underwent some minor alteration that affected the results of the dating. Rockfall is a hazard on slopes greater than 30 degrees. The maximum exposed thickness observed in outcrops is about 55 m.02-07DMUUnit1:bsPebs170-102-205NoneDAS1Mafic-composition lava flowsHighDMU24
73PEbbVolcanic breccia of Buffalo GulchVolcanic breccia of Buffalo GulchEoceneVolcanic and volcaniclastic rocks composed of vitric pyroclasts of rhyolite and andesite. Two lithofacies are observed in the Agate Mountain quadrangle and mapped as a single unit. The block and ash deposit is the most widespread lithofacies and is a buff to gray, light orange to dark red to purple breccia. It is generally well lithified and forms some of the higher topography in the northeastern portion of the quadrangle. The blocks range in size from gravel to boulders up to 1 m and are composed of angular to subangular fragments of tuff, pumice, and andesite in a welded tuff matrix. This matrix is a fine-grained ash that is dark gray on fresh surfaces and becomes light gray to tan when altered. Phenocrysts of white feldspar and smaller amounts of biotite and hornblende are locally visible in the matrix. A matrix supported conglomerate lithofacies was observed in lesser areal extent than the block and ash facies and primarily forms caps on some of the higher knolls in the northeastern portion of the map area. It is an orange to orangish-brown breccia composed of smaller (5 to 15 cm) fragments of tuff, vitrophyre, and granite in a matrix of volcanic ash, mud, and fine-grained sand. The volcanic breccia of Buffalo Gulch was informally named and described on the Antero Reservoir NE quadrangle (Barkmann and others, 2018). Sanidine from a sample collected there yielded an 40Ar/39Ar single-crystal fusion age of 34.27 +/- 0.05 Ma (Barkmann and others, 2018). The unit disconformably overlies the middle andesite series. Rockfall is a hazard on slopes greater than 30 degrees. The maximum thickness exposed in outcrops is about 115 m.02-08DMUUnit1:bbPebb223-115-255605 breccia 0-0-0DAS1Pyroclastic flowsHighDMU25
74PEabAutoclastic volcanic brecciaAutoclastic volcanic brecciaEoceneLight to medium-gray clast supported volcanic breccia. Fragments are angular, up to 50 cm in size, typically elongated, and randomly oriented. Clasts are distinctly exposed out of a softer, fine-grained matrix of similar composition. The breccia is well exposed in the southern half of sec. 15, T. 14 S., R. 75 W., where a 50 m wall abruptly rises on the north side of Agate Creek. Whole-rock analysis of a sample collected from the east side of this outcrop indicates a composition of 62.4% SiO2, 14.7% Al2O3, 2.82% Fe2O3, 6.32% CaO, 0.43% MgO, 3.87% Na2O, and 4.55% K2O. This plots in the trachydacite field on the total alkali-silica diagram of LeBas and others (1986). However, the unit is highly altered, so this may not be its original composition. We interpret the unit to be a probable autoclastic volcanic breccia after Fisher (1960) where it is defined as broken fragments of semisolid and/or solid lava formed during confinement beneath the surface or by relatively slow movement of unconfined lava flows. The autoclastic volcanic breccia overlies the middle andesite series with apparent conformity. Sample JT40, taken in the SW ¼ sec. 14, T. 14 S., R. 75 W., yielded an 40Ar/39Ar date of 34.55+/-0.08 Ma. The breccia is prone to rockfall on slopes greater than 30 degrees. The maximum exposed thickness is about 60 m.02-09DMUUnit1:abPeab194-158-215NoneDAS1Igneous rockMediumDMU26
75PEamMiddle Andesite seriesMiddle Andesite seriesEoceneGray to brown to reddish-brown volcanic rocks primarily of andesitic composition. Two lithofacies were observed in the map area. Massive andesite and brecciated andesite is typically gray to dark-gray aphanitic andesite that weathers to a brown to reddish brown and forms low-lying hills in the eastern part of the quadrangle. It can be porphyritic with phenocrysts of plagioclase, hornblende, and biotite. The brecciated part consists of angular to subangular andesite fragments generally smaller than 6 cm in a matrix of similar composition suggestive of an autobreccia. This lithofacies is found in the lower part of the unit. A matrix-supported conglomerate is the second lithofacies. It contains subrounded to subangular pebbles and cobbles generally less than 4 cm in size and is poorly sorted in a fine-grained ash matrix. The clasts are composed of gray to dark-gray andesite and weather to a brown to reddish-brown color. The middle andesite series, as defined by Barkmann and others (2018) and herein, is correlative with the lower member of the Thirtynine Mile Andesite of Epis and Chapin (1974). On the Antero NE quadrangle, the unit yielded an 40Ar/39Ar age of 34.44+/-0.05 Ma (Barkmann and others, 2018). It nonconformably overlies the Proterozoic rocks. Rockfall is a hazard on slopes greater than 30 degrees. The middle andesite series is over 100 m thick in the east-central part of the map area.02-10DMUUnit1:amPeam203-188-211NoneDAS1Intermediate-composition lava flowsHighDMU27
76PEbbamVolcanic breccia of Buffalo Gulch and middle andesite series, undifferentiatedVolcanic breccia of Buffalo Gulch and middle andesite series, undifferentiatedEoceneVolcanic breccia, andesite, and volcaniclastic conglomerate. Thickness is approximately 100 m. Shown only on cross-section.02-10-01DMUUnit2:bbamPebbam174-128-235NoneDAS1Extrusive igneous materialHighDMU28
77PEwmWall Mountain TuffWall Mountain TuffEoceneRed, purple, gray, pink, and brown rhyolitic crystal and vitric welded tuff and black vitric welded tuff (vitrophyre). The upper rhyolitic crystal and vitric welded tuff is poorly to very poorly sorted with medium-grained, euhedral, translucent sanidine constituting up to 35% of the overall composition, supported by a matrix of very fine-grained vesicular ash and fine-grained biotite making up <1% of the overall composition. The matrix has eutaxitic texture created by crushed pumice lapilli, typically oriented parallel to bedding. The tuff is typically irregularly bedded in 1 cm to 10 cm beds, but varies from very thinly-bedded to massive and locally consists of thinly-laminated low-angle cross beds. Welding of the tuff increases with depth in the flow. The black basal vitrophyre is poorly to very-poorly sorted, with medium-grained, euhedral acicular and elongate-columnar crystals of translucent sanidine supported in a matrix of black glass. The vitrophyre contains elongate tan to yellow clay fiamme averaging 1 cm in width and 4 cm in length with some up to 15 cm in length. The vitrophyre weathers into smooth, rounded outcrops the size of large boulders. Its upper contact with the welded tuff is sharp and averages 1 to 2 m in exposed thickness. It is exposed in two small, isolated outcrops in the NE ¼ sec. 6, T 14 S, R 75 W and is not mapped separately. The Wall Mountain Tuff was forcibly emplaced onto the western flanks of the Proterozoic uplifts within the quadrangle, and into their paleodrainages. It forms ridges reminiscent of flatirons. Pervasive orthogonal jointing and fractures, coupled with differential weathering along eutaxitic texture, cause the unit to weather into semi-elongate blocks, ropy and log-like in texture. This differential weathering coupled with irregular bedding planes creates outcrops of large broken and tilted blocks. McIntosh and Chapin (2004) determined an 40Ar/39Ar age of 36.69+/-0.09 Ma for the Wall Mountain Tuff. Where underlying Proterozoic units have eroded away, the unit is prone to blocky rockfall on slopes. The unit varies dramatically in exposed thickness from less than 1 m to 15 m on the east side of the Agate Creek fault and the west side of the Rye Slough fault. In the area between these two faults, it is about 90 m thick.02-11DMUUnit1:wmPewm152-80-156NoneDAS1Felsic-composition pyroclastic flowsHighDMU29
78PPmmUpper Minturn and lower Maroon formations, undividedUpper Minturn and lower Maroon formations, undividedMiddle Pennsylvanian to Lower Permian?Orangish-brown arkosic sandstone and conglomerate. Sand grains are medium to coarse, and gravel is granule- to pebble-sized. The sandstone and conglomerate occur in planar beds about 5 to 20 cm thick, and in sets of trough cross-beds about 15 cm thick. On the northwest side of the outcrop in NE ¼ sec. 12, T 14 S, R 76 W, these rocks are altered; the feldspars have been turned into clay, and large amounts of interstitial silica are present. Mounds of dolomite are interbedded with the sandstone and conglomerate, and these are described separately below. Outcrops of unit PPmm form isolated hills that stand above the surrounding topography. They nonconformably overlie Proterozoic intrusive igneous and metamorphic rocks on the Hartsel uplift, east of the Rye Slough fault. Rockfall is a hazard on slopes greater than 30 degrees. The thickness exposed in outcrops is approximately 12 to 18 m, but the thickness in the subsurface is probably greater.02-12DMUUnit1P*mmPPmm115-223-255NoneDAS1Mostly sandstoneHighDMU30
79PPmmcUpper Minturn and lower Maroon formations, unnamed dolomite bedsUpper Minturn and lower Maroon formations, unnamed dolomite bedsMiddle Pennsylvanian to Lower Permian?Medium-gray, finely crystalline dolomite that weathers to tan and contains ghosts of crinoid stems, bryozoa, and horn corals. The dolomite is massive, and occurs in mound-shaped outcrops. Rockfall is a hazard on slopes greater than 30 degrees. The thickness exposed in outcrops is approximately 6 m, but the thickness in the subsurface could be greater.02-12-01DMUUnit2P*mmcPPmmc0-169-230NoneDAS1DolomiteHighDMU31
80PEPPEcho Park Alluvium (?), Maroon, and Minturn formations, undifferentiatedEcho Park Alluvium (?), Maroon, and Minturn formations, undifferentiatedEocene to Middle PennsylvanianArkosic sandstone, conglomerate, siltstone, and shale with minor limestone. Thickness is approximately 45 to 490 m. Shown only on cross-section.02-13DMUUnit1:P*PePP179-198-252NoneDAS1Mostly sandstoneHighDMU32
81PbBelden FormationBelden FormationLower PennsylanvianDark-gray, dolomitic shale that is very well indurated, and is extensively fractured. In the vicinity of the Rye Slough fault, it is altered to dark maroon and greenish-brown colors. Very limited outcrop exposures occur in the east side of the ridge of Paleozoic rocks in the southwestern part of the quadrangle. It disconformably overlies the Leadville Limestone and is in fault contact with the Wagontongue Formation. Approximately 45 m of Belden Formation are exposed on the quadrangle. A complete section of the Belden Formation is about 280 m thick in the adjoining Antero Reservoir quadrangle (Kirkham and others, 2012).02-14DMUUnit1*bPb135-161-191NoneDAS1MudstoneHighDMU33
82MlLeadville LimestoneLeadville LimestoneLower MississippianMedium-gray, smooth-weathering micritic limestone in beds 15 cm to 1 m thick. Some beds are internally laminated, and others appear massive. Nodules and lenses of orangish-brown chert are common, especially at the top of the formation. Blocks of fine-grained, well-indurated, quartz sandstone occur at the Leadville-Belden contact, but no outcrops were found. The Leadville Limestone weathers into large blocks, and rockfall is common on slopes greater than 30 degrees. It disconformably overlies the Dyer Dolomite, and is disconformably overlain by the Belden Formation, or is in fault contact with the Wagontongue Formation. Thickness is approximately 91 m.02-15DMUUnit1MlMl225-225-225NoneDAS1LimestoneHighDMU34
83DdDyer DolomiteDyer DolomiteUpper DevonianLight-tan, orangish-tan, and greenish-tan, thinly bedded, microcrystalline dolomite. A 0.3 m bed of massive gray and orange chert occurs at the top of the formation. The Dyer Dolomite disconformably overlies the Fremont Formation. Rockfall is a hazard on slopes greater than 30 degrees. Thickness is approximately 30 m. 02-16DMUUnit1DdDd200-197-226NoneDAS1DolomiteHighDMU35
84OfFremont FormationFremont FormationUpper OrdovicianMedium-gray, microcrystalline dolomite that weathers light gray. It occurs in beds about 15 cm thick. Fossil hash was observed near the base of the formation. Invertebrate burrows and trails approximately 2 mm in diameter were observed on bedding planes. The Fremont Formation disconformably overlies the Harding Sandstone. Rockfall is a hazard on slopes greater than 30 degrees. Thickness is approximately 91 m.02-17DMUUnit1OfOf247-194-218NoneDAS1DolomiteHighDMU36
85OhHarding SandstoneHarding SandstoneUpper OrdovicianPale-pink to reddish-pink, fine-grained quartz sandstone that is silica cemented and breaks across grains. It occurs in beds about 15 cm to 1 m thick. The formation resists erosion and forms ridges. It disconformably overlies the Manitou Formation. Rockfall is a hazard on slopes greater than 30 degrees. Thickness is approximately 23 m.02-18DMUUnit1OhOh226-151-181NoneDAS1SandstoneHighDMU37
86OmManitou FormationManitou FormationUpper OrdovicianGrayish-tan, thinly bedded, microcrystalline dolomite with horizons of orangish-brown or white chert and chert breccia. Invertebrate trails, approximately 2 to 4 mm in diameter, are common on dolomite bedding planes. The formation nonconformably overlies Proterozoic intrusive igneous and metamorphic rocks. Rockfall is a hazard on slopes greater than 30 degrees. Thickness is approximately 55 m.02-19DMUUnit1OmOm246-174-192NoneDAS1Mostly carbonate rockHighDMU38
87YiPorphyritic intrusionPorphyritic intrusionMesoproterozoic?Dark-green biotite gabbro porphyry that weathers black to brown. The unit is composed of up to 50% biotite phenocrysts averaging 10 mm diameter in a fine- to medium-grained groundmass of plagioclase, biotite, minor quartz, and very fine-grained green accessory minerals. The unit weathers readily and forms a valley within the intruded Proterozoic units. Outcrops consist of rounded 0.5 m mounds that weather to gray gravel. Contacts with intruded units are covered and any orientation is masked by extensive weathering. The unit forms one dike on the north-central border of the quadrangle where it intruded units Ya and YXg near a shear zone. 02-20DMUUnit1YiYi78-78-78NoneDAS1Coarse-grained, mafic-composition intrusive igneous rockHighDMU39
88YpPegmatitePegmatiteMesoproterozoicWhite and light-pink, pegmatitic alkali feldspar granite and granite that weathers white. Primarily composed of centric zones of milky-white quartz, bordered by zones of light reddish-pink potassium feldspar, white plagioclase, silver to brown muscovite and, less commonly, medium-grained black biotite and very fine-grained gray accessory minerals. Muscovite typically comprises 1% of total composition. Crystal sizes of euhedral quartz and potassium feldspar average 10 cm but can be up to 50 cm in diameter. Potassium feldspar is commonly perthitic. Muscovite crystals average 1 cm in diameter, with books up to 0.6 m in diameter. Pegmatites form ridges and weather to float of angular cobbles on hillsides. They are commonly associated with small bodies of light-pink to gray, fine-grained, equigranular aplite and occur more frequently in unit Ya than in unit Ygp. Pegmatites are pervasive in the Proterozoic units and vary in size; only those greater than 1 m in width are shown on the map. They average 1.5 m in thickness and 30 m in length.02-21DMUUnit1YpYp203-145-152NoneDAS1Coarse-grained, felsic-composition intrusive igneous rockHighDMU40
89YbdBrittle-ductile shear zone microbrecciaBrittle-ductile shear zone microbrecciaMesoproterozoicPredominantly medium to very coarse-grained microbreccia. The unit is matrix supported and very poorly sorted with framework clasts of predominantly subangular, medium-grained, light to reddish-pink alkali feldspar granite averaging 2 cm in diameter; medium-grained pink potassium feldspar; and gray quartz in a matrix of very fine-grained gray and brown mica. Feldspar grains are commonly weathered to white clay on exposed surfaces. Breccias form mounds that are less than 0.5 m wide, and are exposed over distances of approximately 50 m. Ductile areas within brittle-ductile zones include light-brown mylonitic muscovite schist with reddish-pink breccia streaks of potassium feldspar averaging 1 mm in thickness, and gold-brown phyllonite. Ductile areas also form outcrops that are less than 0.5 m wide, and are exposed over distances of 10 m or less. Most exposures of the unit contact are not well-exposed; only the contact on the west side of the uplift in the NE ¼ sec. 6, T 14 S, R 75 W was mapped. Brittle-ductile zones occur exclusively in Ya and represent the youngest deformation within the Proterozoic units.02-22DMUUnit1YbdYbdNoneNoneDAS1Deformation-related metamorphic rockMediumDMU41
90YaAlkali feldspar graniteAlkali feldspar graniteMesoproterozoicLight-pink to light-gray, fine- to medium-grained equigranular alkali feldspar granite and granitoid that weathers pink to red. The unit is composed primarily of subhedral to anhedral gray and translucent quartz, pink and gray potassium feldspar and up to 10% either biotite or muscovite; locally, biotite is predominant. Whole-rock composition by weight percent is 79.4% SiO2, 11.75% Al2O3, 1.15% Fe2O3, 0.4% CaO, 0.13% MgO, 2.03% Na2O, and 6.5% K2O. After Frost and others, (2001, 2008, 2011) Ya is ferroan, alkali-calcic, and peralkaline. Unit is commonly associated with aplite and pegmatites and commonly exhibits subhedral very coarse to pegmatitic milky and translucent quartz. Where foliated, foliation is delineated by dimensional preferred orientation of biotite; fewer outcrops have penetrative lineation. Locally, outcrops contain dimensional preferred orientation foliation of crosses of black, tabular biotite up to 2 cm in length. The two youngest shear zones occur within the unit. Brecciation and ductile deformation, up to 20 m in total width, occur within these zones. The unit is pervasively jointed by two sets of X-intersecting joints and joint planes are very smooth and angular. It is highly resistant to weathering and underlies sharp ridges and ledges along slopes of Ygp. The unit weathers to distinctly angular gravel and cobbles on hillsides. The unit discordantly intrudes Ygp and is the Proterozoic unit most commonly underlying unit PEwm. Sample 2244, taken in the NW ¼ sec. 8, T. 14 S., R. 75 W., yielded an 40Ar/39Ar date of 1.379+/-0.003 Ga.02-23DMUUnit1YaYa185-186-145NoneDAS1Fine-grained, felsic-composition intrusive igneous rockHighDMU42
91YdDuctile shear zone mylonitesDuctile shear zone mylonitesMesoproterozoicMylonite, grading from protomylonite to mylonite across an average thickness of 1.5 m. Ultramylonites were observed in both Ygp and YXgg. Their average thickness is 5 cm, and they are most commonly located centrally within mylonites averaging 1 m in thickness. Mylonites typically contain sigma type porphyroclasts of pink potassium feldspar and less commonly, delta type. Sigma and delta type porphyroclasts in shear zones indicate the rate of recrystallization was greater than the rate of strain. Porphyroclasts range in size from 1 cm to 5 cm. Like brittle-ductile zones, ductile zones are typically more weathered than surrounding undeformed rock, but they are much better exposed and typically crop out as localized areas of low relief or irregularly spaced boulder-sized outcrops. Ductile shear zones occur in units YXg, Ygp, and YXgg. They are continuous and occur in parallel sets with the exception of one set of anastomosing mylonites near the northern map border in units YXg and Ygp.02-24DMUUnit1YdYdNoneNoneDAS1Deformation-related metamorphic rockHighDMU43
92YgpBiotite granite porphyry and granitic gneissBiotite granite porphyry and granitic gneissMesoproterozoicBlack and gray, weakly to strongly foliated biotite granite porphyry and granitic augen gneiss that weathers gray to brown. Locally granodiorite. Groundmass is typically composed of fine- to medium-grained, subhedral, translucent and gray quartz, white and pink potassium feldspar, white plagioclase, and biotite. Phenocrysts are light-gray and pink subhedral potassium feldspar. The average diameter is 2 cm, but crystals can be up to 5 cm in diameter. They commonly cleave out of the unit with perfect 90 degree cleavage. Where gneissic, porphyroclasts and augen are also primarily pink potassium feldspar, and average 3 cm. Whole-rock composition by weight percent is 70.9% SiO2, 12.95% Al2O3, 4.4% Fe2O3, 2% CaO, 1% MgO, 2.46% Na2O, and 3.69% K2O. After Frost and others (2001, 2008, 2011), Xgp is ferroan, calc-alkalic, and peraluminous. Two sets of equally spaced joints with X-intersections are dominant and present in all outcrops though many are weathered and rounded. The unit is altered by at least five ductile shear zones; these mylonites average 1.5 m in thickness and 20 m in length. The unit forms both massive rounded ridges and slopes where it is more highly weathered. In the northern part of the mapped area, this unit is the primary ridge-former and dominates the landscape. Both weathering and metamorphism increase within the unit to the south, where it is primarily gneiss and prone to forming slopes and grus. It weathers with a consistent lumpy, porphyritic texture into well rounded and sometimes bouldery outcrops and wide fins. Weathering rinds and iron-oxide staining are common. It is discordantly intruded by dikes of Ya, varying in size from less than 1 m to more than 4 m in thickness. Pegmatites, though infrequent, have an average thickness of 30 cm. This is the most widespread Proterozoic unit on the quadrangle. Sample 2153, taken in the SW ¼ sec. 8, T. 14 S., R. 75 W., yielded an 40Ar/39Ar date of 1.380+/-0.003 Ga.02-25DMUUnit1YgpYgp207-214-169ESRI chemical overlay 0-0-0DAS1Igneous and metamorphic rockHighDMU44
93YXgGraniteGraniteMesoproterozoic or PaleoproterozoicLight pink-gray, medium- to coarse-grained, massive to weakly foliated biotite granite that weathers red. Locally the unit is alkali feldspar granite or quartz monzonite. It is equigranular with euhedral to subhedral gray quartz, light-pink potassium feldspar, white plagioclase, and black biotite groundmass crystals averaging 2 mm in diameter. Locally it is porphyritic, with subhedral potassium feldspar phenocrysts averaging 8 mm diameter. Where weakly foliated, foliation is created by dimensional preferred orientation of biotite aggregates. Myrmekitic intergrowths in sodic plagioclase are common. Whole-rock composition is 70.4% SiO2, 13.5% Al2O3, 4.8% Fe2O3, 1.76% CaO, 1.06% MgO, 2.61% Na2O, and 4.01% K2O. Unlike other Proterozoic units within the quadrangle, it weathers to low-lying smooth mounds, lacks dominant jointing, and crops out only in an area on the north-central border of the quadrangle.02-26DMUUnit1YXgYXg207-214-169NoneDAS1Coarse-grained, felsic-composition intrusive igneous rockHighDMU45
94YXfgFine-grained graniteFine-grained graniteMesoproterozoic or PaleoproterozoicLight-gray, fine-grained, moderately foliated, weakly lineated granite and granodiorite that weathers gray. The unit is equigranular, with a groundmass of subhedral gray quartz, pink and brown potassium feldspar, white plagioclase, and biotite. Whole-rock composition is 69.7% SiO2, 13.7% Al2O3, 4.58% Fe2O3, 1.93%CaO, 1.08% MgO, 2.17% Na2O, and 4.81% K2O. The unit weathers along foliations into very smooth slabs averaging 2 cm in thickness. It forms an isolated ridge where it crops out as 1-m -diameter boulders on the ridge top and thin, 1-m-thick rounded slabs along slopes. 02-27DMUUnit1YXfgYXfg166-164-113NoneDAS1Fine-grained, felsic-composition intrusive igneous rockHighDMU46
95YXggGranitic gneissGranitic gneissMesoproterozoic or PaleoproterozoicLight-gray, medium- to coarse-grained, moderately to strongly foliated, biotite granitic gneiss and granite porphyry that weathers red-brown. The unit is composed primarily of subhedral to anhedral white and gray potassium feldspar, gray quartz, white plagioclase, biotite, and accessory hornblende. It is porphyritic with subhedral megacrysts of gray and white potassium feldspar averaging 3 cm in diameter. Whole-rock composition by weight percent is 70.9% SiO2, 12.9 % Al2O3, 3.29% Fe2O3, 1.73% CaO, 0.52% MgO, 3% Na2O, and 5.11% K2O. The unit is marked by enclaves of quartz syenite and alkali feldspar quartz syenite composition far more resistant to weathering than the rest of the unit. These spheroidal to oblate enclaves are dominated by medium to coarse-grained microcline with fine-grained biotite. Enclaves average 5 cm in diameter with a maximum size of 15 cm. The unit is mostly gneissic and the enclaves commonly delineate an S-C fabric where they are flattened and stretched. Two joint sets with X-intersections are pervasive; the vertical set is more closely spaced, causing the unit to weather into fins less than 1 m wide. The unit commonly contains aplite dikes and pegmatites typically parallel to foliation averaging 10 cm in thickness. Some of the aplite dikes are tightly folded and in one isolated zone of semi-brittle deformation, have cm-scale offset en-echelon faulting. The unit is also altered by four parallel mylonites and ultramylonites averaging 1 m and 10 cm in thickness, respectively, that extend parallel along the length of the exposed unit. Outcrops are highly weathered with broken surfaces coated in iron oxide staining and feldspars weathered to white clay. Though limited in extent, this unit forms very large, 5 m to 10 m tall and 20 m long, rounded ridges of fins with a nodular texture created by the differential weathering of the oblate enclaves.02-28DMUUnit1YXggYXgg166-164-113ESRI chemical overlay 0-0-0DAS1Metaigneous rockHighDMU47
96YXuProterozoic rocks, undifferentiatedProterozoic rocks, undifferentiatedProterozoicGranite, granite porphyry, and granitic gneiss with minor pegmatite and gabbro, cut by brittle-ductile and ductile shear zones. Shown only on cross-section.02-29DMUUnit1YXuYXu186-194-92NoneDAS1Igneous and metamorphic rockHighDMU48

Glossary

OBJECTIDTermDefinitionDefinitionSourceIDGlossary_ID
531 standard deviationA statistic used as a measure of the dispersion or variation in a distribution or set of data, equal to the square root of the arithmetic mean of the squares of the deviations from the arithmetic mean. One SD is the 84.1st percentile.GEODICT1GLO52
522 standard deviationA statistic used as a measure of the dispersion or variation in a distribution or set of data, equal to the square root of the arithmetic mean of the squares of the deviations from the arithmetic mean. Two SD is the 97.7th percentile.GEODICT1GLO51
5Agethe length of time during which a being or thing has existed; length of life or existence to the time spoken of or referred toDICT1GLO01
6anticlineA fold in rock strata with a convex upward shape. The rocks in the core of an anticline are the oldest. Identity and existence certain, location accurateGEODICT1GLO02
7anticline_approximateA fold in rock strata with a convex upward shape. The rocks in the core of an anticline are the oldest. Identity and existence certain, location approximateGEODICT1GLO03
8anticline_concealedA fold in rock strata with a convex upward shape. The rocks in the core of an anticline are the oldest. Identity and existence certain, location concealedGEODICT1GLO04
35anticline_inferredA fold in rock strata with a convex upward shape. The rocks in the core of an anticline are the oldest. Identity and existence certain, location accurateGEODICT1GLO05
9Ar-ArArgon–argon dating. A variant of the K–Ar dating method fundamentally based on the natural radioactive decay of 40K to 40Ar, but which uses an artificially generated isotope of argon (39Ar) (produced through the neutron irradiation of naturally occurring 39K) as a proxy for 40K.GEODICT1GLO06
10beddingThe characteristic structure of sedimentary rocks in which layers of different composition, grain size, or arrangement are stacked one on top of another in a sequence with oldest at the bottom and youngest at the top.GEODICT1GLO07
39borderThe edge or boundary of something, or the part near itDICT1GLO08
11boundaryA line that marks the limits of an areaDICT1GLO09
12Brittle-ductile shear zoneA concentrated zone displaying evidence of both brittle and ductile deformation formed by high strain and noncoaxial shear under crustal conditions intermediate or transitional from brittle to ductile.GEODICT1GLO10
3certainIdentity of a feature can be determined using relevant observations and scientific judgment; therefore, one can be reasonably confident in the credibility of this interpretation.FGDC-STD-013-2006GLO11
13closed depressionA depression is a landform sunken or depressed below the surrounding areaGEODICT1GLO12
14contactA geological contact is a boundary which separates one rock body from another. A contact can be formed during deposition, by the intrusion of magma, or through faulting or other deformation of rock beds that brings distinct rock bodies into contact.GEODICT1GLO14
41creek labelAn identifer for a water featureDICT1GLO15
34Cross sectionA graphic representation of the intersection of the geological bodies in the subsurface with a vertical plane of a certain orientation showing relationships between rock unitsGEODICT1GLO16
15delta foresetsA foreset bed is one of the main parts of a river delta. It is the inclined part of a delta that is found at the end of the stream channel as the delta sediment is deposited along the arcuate delta front. As the sediments are deposited on a sloping surface the resulting bedding is not horizontal, but dips in the direction of current flow toward deeper water. A cross-section of a delta shows the cross bedding in the direction of stream flow into the still water.GEODICT1GLO17
36Deposit TypeGroupings for surficial units in the CMUGEODICT1GLO18
16DMUHeading1GeMS hierarchy formatting termGEMS1GLO19
17DMUHeading2GeMS hierarchy formatting termGEMS1GLO20
18DMUUnit1GeMS hierarchy formatting termGEMS1GLO21
33DMUUnit2GeMS hierarchy formatting termGEMS1GLO22
19Ductile shear zoneA concentrated zone of ductile deformation formed by high strain and noncoaxial shear under ductile crustal conditions.GEODICT1GLO23
40elev tickA hatch mark shown on the edges of geologic cross sections to denote the elevationDICT1GLO24
20estimated_beddingApproximate orientation of inclined bedding— Approximate orientation of inlcined bedding showing approximate strike and dipGEODICT1GLO25
43faultA fault is a fracture or zone of fractures between two blocks of rock. Faults allow the blocks to move relative to each other.GEODICT1GLO26
42fault labelAn identifier for a geologic structuralDICT1GLO27
49fault movementCartographic symbols showing the relative offset on the fault in cross sectionGEODICT1GLO28
21fault_approximateA fault is a fracture or zone of fractures between two blocks of rock. Faults allow the blocks to move relative to each other. Fault_approximate indicates that the existence is certain and the location is approximateGEODICT1GLO29
22fault_certainA fault is a fracture or zone of fractures between two blocks of rock. Faults allow the blocks to move relative to each other. Fault_certain indicates that the existence is certain and the location is accurateGEODICT1GLO30
23fault_concealedA fault is a fracture or zone of fractures between two blocks of rock. Faults allow the blocks to move relative to each other. Fault_concealed indicates that the existence is certain and the location is concealedGEODICT1GLO31
24fault_concealed_questionableA fault is a fracture or zone of fractures between two blocks of rock. Faults allow the blocks to move relative to each other. Fault_concealed_questionable indicates that the existence is questionable and the location is concealedGEODICT1GLO32
25fault_inferredA fault is a fracture or zone of fractures between two blocks of rock. Faults allow the blocks to move relative to each other. Fault_inferred indicates that the existence is questionable and the location is inferredGEODICT1GLO33
50fold plungeLinear features, like folds, have a bearing sense (often called their trend) which is taken as the direction in which they point at an angle downward. The amount of the this angle, measured from the horizontal, is the the plunge of the linear feature.GEODICT1GLO34
26foliationThe planar or layered characteristics of metamorphic rocks that are evidence of the pressures and/or temperatures to which the rock was exposed. These can be structural such as cleavage, textural such as mineral grain flattening or elongation, or compositional such as mineral segregation banding.GEODICT1GLO35
46GAGiga Anum. Years x 10 to the 9th powerGEODICT1GLO36
37Geology YbdLinear geologic featuresGEODICT1GLO37
38Geology YdLinear geologic featuresGEODICT1GLO38
44HighGeMS term for the relative confidence assigned to GeoMaterialConfidence valueGEMS1GLO39
48Ka1000 yearsGEODICT1GLO40
47MAMega Anum. Years x 10 to the 6th powerGEODICT1GLO41
45MediumGeMS term for the relative confidence assigned to GeoMaterialConfidence valueGEMS1GLO42
27OSLOptically-Stimulated Luminescence is a late Quaternary dating technique used to date the last time quartz sediment was exposed to light. As sediment is transported by wind, water, or ice, it is exposed to sunlight and zeroed of any previous luminescence signal.GEODICT1GLO43
4questionableIdentity of a feature cannot be determined using relevant observations and scientific judgment; therefore, one cannot be reasonably confident in the credibility of this interpretation. For example, IdentityConfidence = questionable is appropriate when a geologist reasons "I can see some kind of planar feature that separates map units in this outcrop, but I cannot be certain if it is a contact or a fault."FGDC-STD-013-2006GLO44
28synclineA trough-shaped fold with youngest strata in the centerGEODICT1GLO45
29syncline_approximateA trough-shaped fold with youngest strata in the center. Syncline_approximate indicates the existence is certain and the location is approximateGEODICT1GLO46
30syncline_concealedA trough-shaped fold with youngest strata in the center. Syncline_concealed indicates the existence is certain and the location is concealedGEODICT1GLO47
31syncline_inferredA trough-shaped fold with youngest strata in the center. Syncline_inferred indicates the existence is questionable and the location is inferredGEODICT1GLO48
51Uranium exploration drill holeA drill hole is a circular hole made by drilling; to explore for valuable minerals, water or petroleum or to obtain geologic information. In this case, the drilling was for uranium exploration. GEODICT1GLO50
32volcanic layeringInclined flow banding, lamination, layering, or foliation in igneous rock showing strike and dip in igneous rock—Showing strike and dipGEODICT1GLO49

MiscellaneousMapInformation

OBJECTIDMapPropertyMapPropertyValueMiscellaneousMapInformation_ID
1Statemap Agreement NumberThis mapping project was funded jointly by the Colorado Geological Survey and the U.S. Geological Survey through the National Cooperative Geologic Mapping Program under STATEMAP agreement G19AC00233.MMI01
2AuthorsBy Karen J. Houck, Jay Temple, Kassandra O. Lindsey, Lauren D. Broes, and Daniel P. MigginsMMI02
3Regional SettingThe Agate Mountain quadrangle is located at the southern end of South Park, in central Colorado. It spans a high mountain valley (the Wagon Tongue graben), along with portions of a ridge (Kaufman Ridge, in the southwestern part of the quadrangle), and an upland (the Hartsel uplift, in the northeastern part). A drainage divide, oriented approximately northwest-southeast, extends across the quadrangle. South of the divide, Badger Creek and Wagon Tongue Creek are in the Arkansas River drainage basin. North of the divide, Agate Creek and Little Agate Creek are in the South Platte River drainage basin. At an elevation of 3040 m, Agate Mountain is the highest point on the quadrangle. Kaufman Ridge, the Wagon Tongue graben, and the Hartsel uplift comprise three fault-bounded structural blocks, which were active and moved independently of each other in the late Paleozoic, late Mesozoic, and Cenozoic eras. The Rye Slough fault separates Kaufman Ridge on the west from the Wagon Tongue graben on the east. The Agate Creek and Little Agate Creek faults separate the Wagon Tongue graben on the west from the Hartsel uplift on the east.MMI03
4Major Structural FeaturesMany periods of tectonism affected the rock formations on this quadrangle, but those that are the most evident are: 1) the ancestral Rocky Mountains orogeny (late Paleozoic), 2) the Laramide orogeny (Late Cretaceous to Eocene), 3) Eocene-Oligocene tectonics, and 4) Rio Grande rifting (Neogene). Evidence for reactivation of several structural features exists on the quadrangle. The most prominent structural features are as follows:MMI04
5Major Structural FeaturesThe Hartsel uplift underlies the northeastern part of the quadrangle. The lack of lower and middle Paleozoic rocks beneath erosional remnants of late Paleozoic rocks on the uplift indicates that it was part of the Frontrangia uplift (Mallory, 1958) during the late Paleozoic. The lack of Mesozoic rocks indicates that it was again a positive feature during the Laramide orogeny. The thin sequence of Eocene and Oligocene rocks and the lack of Miocene rocks indicate that the uplift was also a positive feature during the Eocene, Oligocene, and Miocene.MMI05
6Major Structural FeaturesAgate Creek and Little Agate Creek faults, together with the unnamed west-northwest trending fault along Agate Creek, form the western boundary of the Hartsel uplift. No fault plane exposures were found on the quadrangle; we interpret them to be high-angle reverse faults. Subsurface data indicate down-to-west movement of as much as 520 m.MMI06
7Major Structural FeaturesKaufman Ridge underlies the southwestern corner of the quadrangle. The presence of lower and middle Paleozoic rocks beneath a thick sequence of upper Paleozoic rocks indicates that Kaufman Ridge was part of the central Colorado trough (De Voto, 1972) during the late Paleozoic. The absence of Mesozoic rocks indicates that it became a positive feature during the Laramide orogeny. Erosional detritus from Kaufman Ridge occurs in the Eocene, Oligocene, and Miocene rocks in the Wagon Tongue graben (described below), indicating that the ridge continued to be a positive feature during those epochs.MMI07
8Major Structural FeaturesRye Slough fault forms the eastern boundary of Kaufman Ridge. It was mapped by Wallace and others (1999) on the Gribbles Park quadrangle to the south. During the current mapping project, it was found to extend northward onto the Agate Mountain quadrangle. No fault plane exposures were found, and it is interpreted to be a high-angle fault dipping to the east. Subsurface data indicate that fault movement was down-to-west during the late Paleozoic, and down-to-east during the Laramide, Eocene-Oligocene, and Neogene tectonic episodes. The top of the Proterozoic rocks is currently about 450 m lower on the east side of the fault relative to the west side, as depicted in cross-section B-B’. Drill holes west of cross-section line A-A’ on the adjoining Castle Rock Gulch quadrangle show similar displacement of the top of the Proterozoic rocks (Wyoming Mineral Corporation, unpublished uranium exploration data). MMI08
9Major Structural FeaturesWagon Tongue graben is bounded on the west by the Rye Slough fault, and on the east by the Agate Creek, Little Agate Creek, and associated faults. In the graben, the Proterozoic rocks are overlain by several hundred meters of arkosic sediments; lower and middle Paleozoic rocks are not present. Lithologic summaries from drill holes identify these arkosic sediments as the Echo Park Alluvium, but the Echo Park and Minturn/Maroon formations look very similar in this part of South Park. The most obvious difference is that the Minturn/Maroon formations contain interbedded carbonates with Paleozoic marine fossils. Carbonates and possible Paleozoic rocks were noted in some of the subsurface descriptions, and both of the small arkose outcrops on the quadrangle are capped by fossiliferous marine carbonates. For these reasons, it seems likely that at least some of the arkosic rocks in the subsurface belong to the Minturn/Maroon formations. In other parts of South Park, the composite thickness of the Minturn and Maroon formations is over 3000 meters. If these formations are present in the Wagon Tongue graben, they are relatively thin. The arkosic rocks are overlain by relatively thick layers of Wall Mountain Tuff, Tallahassee Creek Formation, Antero Formation, and Wagontongue Formation. In the northern drill holes, the logger had difficulty identifying the contact between the Tallahassee Creek and Antero formations, logging them as undifferentiated. This supports the interpretation that the contact between the two is gradational in this part of South Park. Cenozoic movement on the Rye Slough fault was likely greater than on the Agate Creek and Little Agate Creek faults. These relationships suggest that the Wagon Tongue graben is better described as a half-graben. If the above interpretations about the Wagon Tongue graben are correct, then the area that is now the graben was part of the Frontrangia uplift in the late Paleozoic. It was also uplifted during the Laramide orogeny, but during the Eocene, Oligocene, and Miocene epochs it subsided and accumulated locally derived sediments.MMI09
10Major Structural FeaturesTrump fault and associated structures occur in the northern and central parts of the quadrangle, in the Wagon Tongue graben. The fault is named for the abandoned townsite of Trump, located approximately 3.5 km north of the fault. It is a high-angle, down-to-south fault with approximately 300 m of displacement on the Antero-Wagontongue contact, and strikes N50E. At least one similar, unnamed fault occurs to the north of it. A syncline occurs southeast of the Trump fault, the westernmost in a series of folds between the Trump fault and the Little Agate Creek fault to the east.MMI10
11Major Structural FeaturesWagon Tongue Creek fault occurs in the southern part of the quadrangle, in the Wagon Tongue graben. It is a high-angle, down-to-north fault that offsets the Antero-Wagontongue contact by about 30-60 m. A large syncline occurs on the downthrown side of the fault; it may have formed as a result of fault movement. The Wagon Tongue Creek fault has the same orientation as the Trump fault.MMI11
12Stratigraphy and Structural EvolutionProterozoic rocks crop out at the surface on both Kaufman Ridge and the Hartsel uplift. The oldest comprise a suite of granites and granitic gneisses, (units Ygp, YXgg, YXfg, and YXg). These were cut by ductile shear zones with mylonites (Yd) trending northeast and west-northwest. The mylonite in the southwest corner of the quadrangle is on a fault that was later reactivated to offset the Manitou Formation (Om). The mylonites in the southeast part of the quadrangle have the same orientation as the Wagon Tongue Creek fault, and the mylonites in the northern part of the quadrangle have the same orientation as the Trump fault and the unnamed fault on Agate Creek. Though some of these faults have moved as recently as the Neogene, they likely have their origins in structures that first formed in the Proterozoic. Northeast trending shear zones are likely reflective of regional transpressive, contractional shortening coeval to emplacement of these rocks during the Berthoud orogeny (Sims and others, 2001). The Proterozoic rocks have prominent jointing, and these joints are the main conduits for groundwater movement in these rocks. The diagram below shows the orientations of joints measured in the Proterozoic rocks. They, too, are similar to the orientations of the major faults and mylonites in the area.MMI12
13Stratigraphy and Structural EvolutionThe granite suite was metamorphosed in places, causing foliations and augen to develop. Afterward, the Proterozoic rocks were intruded by alkali feldspar granite (unit Ya). A brittle-ductile shear zone cut the unit in the northern part of the map area, forming mylonite unit Ybd. Dikes and small bodies of pegmatite and aplite (unit Yp) intruded the Proterozoic rocks, especially in and around unit Ya. Mafic dike Yi intruded unit Ygp on the northern edge of the map; it trends parallel to the west-northwest shear zones in the area.MMI13
14Stratigraphy and Structural EvolutionThe distribution of the lower and middle Paleozoic sedimentary rock formations over a broad area (Ross and Tweto, 1980) implies that these rocks were originally deposited over the entire quadrangle, but were subsequently eroded away on the Hartsel uplift and the area that became the Wagon Tongue graben. They crop out only in the southwestern corner, on the east side of Kaufman Ridge. Formations include the Manitou (Om), Harding (Oh), Fremont (Of), Dyer (Dd), and Leadville (Ml). They were deposited as shallow marine sediments on a continental shelf that was, for the most part, tectonically stable. Each formation is bounded by unconformities, indicating long periods of exposure and erosion between episodes of deposition. The upper surfaces of the carbonate formations developed karst in places, and chert was later precipitated in voids.MMI14
15Stratigraphy and Structural EvolutionDuring the late Paleozoic Era, the quadrangle was at the boundary between the Frontrangia uplift to the east and the central Colorado trough to the west. On the Antero NE quadrangle to the north, the Agate Creek fault bounds the western edge of the uplift (Barkmann and others, 2018). However, subsurface data indicate that the Rye Slough fault is the bounding fault on the Agate Mountain quadrangle. West of the fault, approximately 300 m of Ordovician through Mississippian rocks, as well as the lower part of the Belden Formation (Pb), overlie the Proterozoic rocks. Where not removed by erosion or faulting, approximately 3300 m of additional Pennsylvanian and Permian(?) rocks are present in this part of the central Colorado trough. East of the Rye Slough fault, less than 600 m of probable upper Minturn and lower Maroon formations (P*mm) overlie the Proterozoic rocks in the 15 drill holes studied for this project. The Ordovician, Devonian, and Mississippian rocks, Belden Formation, lower Minturn Formation, Coffman Member, and Minturn evaporites are all missing. The preceding discussion implies that a large east-west fault exists in the northern part of this quadrangle or the southern part of the Antero NE quadrangle. This down-to-north fault would have connected the Agate Creek fault and Rye Slough fault, forming part of the boundary between the late Paleozoic central Colorado trough and the Frontrangia uplift. The Belden Formation was deposited in the central Colorado trough, under marginal marine conditions. The upper Minturn and lower Maroon formations were deposited in river valleys and shallow seas on the Hartsel uplift. The sandstones and conglomerates are formed of arkosic sediments shed from Proterozoic rocks on the uplift, and the carbonates (P*mmc) were formed as mounds in shallow marine water around the edges of the uplift. An important consequence of the late Paleozoic geologic history within the mapped area is that there are few or no evaporites underlying the quadrangle. On Kaufman Ridge they have been eroded away, and they were probably never deposited in the Wagon Tongue graben or on the Hartsel uplift. Thus, the subsidence problems and groundwater contamination problems caused by evaporite rocks in other parts of South Park are not likely to occur on the Agate Mountain quadrangle, except possibly in the northwestern corner.MMI15
16Stratigraphy and Structural EvolutionThe regional distribution of Mesozoic sedimentary rock formations over a broad area of the western United States implies that these rocks were originally deposited over the entire quadrangle but were subsequently eroded away during or after the Laramide orogeny. The orogeny began in the Late Cretaceous and continued into the Eocene (Raynolds, 1997). It was dominated by contractional deformation; the Paleozoic rocks cropping out on the quadrangle are steeply tilted as a consequence of this compression.MMI16
17Stratigraphy and Structural EvolutionNear the end of the Laramide orogeny, the Hartsel uplift was segmented into several internal basins and uplifts. Arkosic sediments mapped as Echo Park Alluvium accumulated in alluvial fans within the basins as they developed (Epis and Chapin, 1974; Chapin and Cather, 1983). No Echo Park Alluvium was seen in surface outcrops, but cuttings from drill holes in the northwestern and central parts of the quadrangle were identified as possible Echo Park Alluvium. Because the arkosic sediments in the upper Minturn and lower Maroon formations are very similar to those in the Echo Park Alluvium, they are shown as undifferentiated (:P*) in the cross-sections.MMI17
18Stratigraphy and Structural EvolutionFaulting and folding continued after the Laramide orogeny, but was accompanied by widespread volcanism. Eocene and Oligocene rock formations on the quadrangle record volcanism accompanied by fluvial and lacustrine sedimentation from approximately 37 to 33 Ma. Steeply dipping Wall Mountain Tuff (:wm) occurs on the western and southern flanks of the Proterozoic erosional remnants of the Hartsel uplift. The silicic tuff is thought to be the deposit of a single, large pyroclastic flow that came from a volcano located somewhere to the west (Epis and Chapin, 1974). The orientation of the dipping tuff mimics the paleotopography of the uplift, implying that the pyroclastic flow was obstructed by the uplift and came to rest against it. The Wall Mountain Tuff event was followed by andesitic volcanism that produced lava flows and lahar deposits of the middle andesite series of the Thirtynine Mile volcanics (unit :am; Barkmann and others, 2018). These flows and lahars are thought to have come from the Guffey volcanic center, located approximately 18 km to the east (Epis and Chapin, 1974). In the east-central part of the quadrangle, outcrops of a trachydacite autobreccia (:ab) occur around the unnamed fault along Agate Creek. The autobreccia is strongly altered, with large patches of calcite in the matrix. It may be altered :am, or it may be a separate volcanic unit. Erosional remnants of a prominent rhyolitic volcanic breccia (:bb) from an unknown source cap the andesitic volcanic rocks. The breccia includes ignimbrites and lahars that were deposited on the eastern part of the quadrangle. In the northeastern part of the quadrangle, the rhyolite breccia is overlain by a trachybasalt lava flow (:bs), which may be an erosional remnant of the upper andesite series of the Thirtynine Mile volcanics. It is also thought to have originated in the Guffey volcanic center (Epis and Chapin, 1974). Following deposition of the Thirtynine Mile volcanics, volcaniclastic sediments of the Tallahassee Creek Conglomerate (:tc) were deposited on the quadrangle as debris flows, fluvial deposits, and lacustrine deposits. Lacustrine limestone formed unit :tcl. Near the end of the deposition of the Tallahassee Creek Conglomerate, repeated eruptions of Mt. Aetna blanketed parts of the quadrangle with thick deposits of ash and pumice, some of which were reworked into fluvial and lacustrine deposits of the Antero Formation (:a; McIntosh and Chapin, 2004). Most of the pyroclastic flows in the Antero Formation on the quadrangle are unwelded, but one small welded tuff formed unit :at. Limestone precipitated in lakes to form unit :al. Following a period of erosion, eruption of the Bonanza caldera blanketed the southern part of the quadrangle with rhyolitic pyroclastic flows that became the Gribbles Park Tuff. During deposition of these volcanic and volcaniclastic formations, the Wagon Tongue graben subsided and received thick accumulations. Kaufman Ridge and the Hartsel uplift subsided much less, and received thinner accumulations. On Kaufman Ridge, the accumulations were mainly in paleovalleys (Wallace and Keller, 2003). On the Hartsel uplift, the volcanic and volcaniclastic rocks are more widely distributed. Gravel clast compositions indicate that Kaufman Ridge was a source of sediment during deposition of the Tallahassee Creek Conglomerate, and to a lesser extent, the Hartsel uplift. During deposition of the Antero Formation, the Thirtynine Mile volcanics on the Hartsel uplift were a major source of sediment. Kaufman Ridge also supplied a lesser amount of sediment in the western part of the quadrangle. Faults and folds deform the Antero Formation, and an angular unconformity separates it from the Wagontongue Formation, indicating that tectonic activity continued after deposition of the Antero Formation.MMI18
19Stratigraphy and Structural EvolutionDuring the Miocene Epoch, the Wagontongue Formation (Nwt) was deposited over the Antero Formation and Gribbles Park Tuff, in the Wagon Tongue graben. It, too, is composed of volcaniclastic deposits. Deposits on the west side of the quadrangle contain clasts from Kaufman Ridge, and deposits from the east side contain clasts from the Thirtynine Mile volcanic series on the Hartsel uplift. This indicates that Kaufman Ridge and the Hartsel uplift were still positive features during the Miocene. Fluvial channel and debris flow deposits are common adjacent to the edges of the uplifts, whereas the central area contains more fine-grained deposits with paleosols. These are interpreted to be alluvial fan and alluvial plain deposits, respectively, which accumulated in the Wagon Tongue graben between the Rye Slough and Little Agate Creek faults. Folds and faults deform the Wagon Tongue Formation. Some of the faults have hundreds of meters of offset. This deformation is coeval with the opening of the Rio Grande rift.MMI19
20Stratigraphy and Structural EvolutionThroughout the Pleistocene, much of the high-elevation terrain (above 3000 m) in the region was covered by snow and ice during periods of glaciation. Units Qg and Qgo consist of coarse-grained sediments deposited during interglacial periods when stream discharge was greater than modern times. During these interglacial periods, streams carrying a significant amount of sediment from the high-elevation glaciated areas deposited it as gravel in river valleys. Later fluvial downcutting left fluvial terraces, such as those along Agate, Little Agate, Wagon Tongue, and Badger creeks, along portions of their channel lengths. Agate and Little Agate creeks flow west-northwest through the northern portion of the quadrangle. Sediments transported by these creeks were predominantly derived from the Thirtynine Mile volcanic field. In the southern part of the quadrangle, Wagon Tongue and Badger creeks originate near Agate Mountain and flow south-southwest. Sediments in these creeks are eroded from volcanic bedrock units and also reworked from the Wagontongue Formation. Since the Late Pleistocene, modern channels have continued to undergo periods of incision and aggradation. The deposits consist of Holocene alluvial terraces and sediment in associated floodplains that are underlain by units Qa2 and Qa1. Ephemeral streams draining higher elevations in the quadrangle are underlain by unit Qau which was likely deposited throughout the Holocene by seasonal storm events. Sediments were transported and deposited as relatively thin (around 1.5 m in thickness) alluvium within ephemeral stream channels. Unit Qsw was deposited in a similar way, except during storm events water transported sediment by overland flow rather than channelized flow. MMI20
21Stratigraphy and Structural EvolutionDebris-flow fan deposits (Qdf) are locally interbedded with units Qa1 and Qa2, especially along Wagon Tongue and Badger creeks. Their position in the landscape and stratigraphic relationship with other deposits indicates repeated debris-flow events. These have probably occurred during above-average precipitation events since the Late Pleistocene, and they continue to be potential geologic hazards today. Landslides (Qls) in the quadrangle have occurred at or near the contact with unit Qgo and the underlying Wagontongue Formation. Landsliding was probably caused by increases in pore pressure from above-average annual precipitation or storm events during the Pleistocene and Holocene.MMI21
22ACKNOWLEDGMENTSA project of this nature is not possible without the help and cooperation of many landowners and land management agencies. We thank everyone who graciously allowed us to map on their property. We especially thank Guy Gould and Kim Davis of Sipal Ranch, Monty Downare and family of Elk Mountain Cattle Company, and Justin Osborne and Le Ann Markham of the Colorado State Land Board. We also thank Cindy Jones of Park County GIS for providing us with digital map files showing land ownership in our mapping area. Charlie Klausner of Hartsel Springs Lodge kindly provided living accommodations while we were working on the project. Fred Grigsby, former exploration manager at Wyoming Mineral Corporation, provided access to his uranium drill hole data, which greatly improved the cross-sections and structural interpretation. After Fred passed away, Dorothy Grigsby and Joe Grigsby kindly donated Fred’s electric logs, gamma ray logs, and lithologic descriptions of cuttings to the Arthur Lakes Library at Colorado School of Mines, where they are available for inspection. Laura Craven and Sara Mack of the Natural Resources Conservation Service graciously provided detailed assessments, official soil profile descriptions, and aided in the excavation of both soil pits. We especially thank Bob Kirkham for facilitating access to the drill hole data, and for helpful discussions about the geology of the area. Vince Matthews and Matt Morgan reviewed the map and accompanying materials, providing many helpful suggestions that substantially improved the final product.MMI22
23REFERENCESBarkmann, P. E., Houck, K J., McGee, K., and Miggins, D. P., 2018, Geologic map of the Antero Reservoir NE quadrangle, Park County, Colorado: Colorado Geological Survey Open-File Report 18-05, scale 1:24,000. Birkeland, P.W., 1999, Soils and Geomorphology, Third Edition: Oxford University Press, 430 p. Carpenter, M. B., Keane, C. M., and Cantner, K., 2016, The Geoscience Handbook 2016: Alexandria, Virginia, American Geological Institute. Chapin, C. E., and Cather, S. M., 1983, Eocene tectonics and sedimentation in the Colorado Plateau-Rocky Mountain area, in, Lowell, J. D., and Gries, R., eds., Rocky Mountain foreland basins and uplifts: Denver, Rocky Mountain Association of Geologists, p. 33-56. Cohen, K.M., Finney, S.C., Gibbard, P.L., and Fan, J.-X., 2022, The International Chronostratigraphic Chart: Episodes, V. 36, p. 199-204 De Voto, R.H., 1971, Geologic history of South Park and geology of the Antero Reservoir quadrangle, Colorado: Colorado School of Mines Quarterly, v. 66, no. 3, 90 p. De Voto, R. H., 1972, Pennsylvanian and Permian stratigraphy and tectonism in central Colorado: Colorado School of Mines Quarterly, v. 67, no. 4, p. 139-185. Epis, R. C., and Chapin, C. E., 1974, Stratigraphic nomenclature of the Thirtynine Mile volcanic field, central Colorado: U. S. Geological Survey Bulletin 1395-C, 23 pp. Fisher, R.V., 1960, Classification of volcanic breccias: Geological Society of America Bulletin, v. 71, p. 973-982. Frost, B.R., Barnes, C.G., Collins, W.J., Arculus, R.J., Ellis, D.J., and Frost, C.D., 2001, A Geochemical Classification for Granitic Rocks: Journal of Petrology, v. 42, no. 11, p. 2033–2048. Frost, B.R., and Frost, C.D., 2008, A Geochemical Classification for Feldspathic Igneous Rocks: Journal of Petrology, v. 49, no. 11, p. 1955–1969. Frost, C.D., and Frost, B.R., 2011, On Ferroan (A-type) Granitoids: their Compositional Variability and Modes of Origin: Journal of Petrology, v. 52, no. 1, p. 39–53. Kirkham, R. M., Houck, K. J., Carroll, C. J., and Heberton-Morimoto, A. D., 2012, Antero Reservoir quadrangle geologic map, Park and Chaffee counties, Colorado: Colorado Geological Survey Open-File Report, scale 1:24,000. Le Bas, M. J., Le Maitre, R. W., Streckeisen, A., and Zanettin, B., 1986, A chemical classification of volcanic rocks based on the total alkali-silica diagram: Journal of Petrology, v. 27, p. 745-750. Machette, M.N., 1985, Calcic soils of the southwestern United States: Geological Society of America Special Paper no. 203, pp. 1-21. McIntosh, W.C., and Chapin, C.E., 2004, Geochronology of the central Colorado volcanic field, in Cather, S.M., McIntosh, W.C., and Kelley, S.A., eds., Tectonics, geochronology, and volcanism in the southern Rocky Mountains and Rio Grande rift: New Mexico Bureau of Geology and Mineral Resources Bulletin 160, p. 205-237. Mallory, W. W., 1958, Pennsylvanian coarse arkosic red beds and associated mountains in Colorado, in, Curtis, B. F., ed., Symposium on Pennsylvanian rocks in Colorado and adjacent areas: Rocky Mountain Association of Geologists, p. 17-20. Munsell Color Company, 1991, Munsell soil color charts: Baltimore, MD, Munsell Color Company. Neuendorf, K. E., Mehl, J. P., Jr., and Jackson, J. A., 2005, Glossary of Geology, Fifth Edition: Alexandria, Virginia, American Geological Institute, 779 p. Raynolds, R. G., 1997, Synorogenic and post-orogenic strata in the central Front Range, Colorado, in, Bolyard, D. W., and Sonnenberg, S. A., eds., Geologic history of the Colorado Front Range: Denver, Rocky Mountain Association of Geologists Symposium, p. 43-48. Ross, R. J., and Tweto, O., 1980, Lower Paleozoic sediments and tectonics in Colorado, in, Kent, H. C., and Porter, K. W., Colorado Geology: Denver, Rocky Mountain Association of Geologists, p. 47-56. Scott, G.R., 1965, Nonglacial Quaternary geology of the southern and middle Rocky Mountains, in Wright, E.W., and Frey, D.G., eds., The Quaternary of the United States: Princeton University Press, pp. 243-254. Sims, P.K., Bankey, V., and Finn, C.A., 2001, Preliminary Precambrian basement map of Colorado-- A geologic interpretation of an aeromagnetic anomaly map: U.S. Geological Survey Open File Report 01-0364, accessed March 13, 2020, at https://pubs.usgs.gov/of/2001/ofr-01-0364/colo_of_text.html. Stark, J.T., Johnson, J.H., Behre, Jr, C.H., Powers, W.E., Howland, A.L., and Gould, D.B., 1949, Geology and origin of South Park, Colorado: Geological Society of America Memoirs, v. 33, 198 p., scale 1:62,000. Wallace, C. A., Cappa, J. A., and Lawson, A. D., 1999, Geologic map of the Gribbles Park quadrangle, Park and Fremont counties, Colorado: Colorado Geological Survey, OF-99-3, scale 1:24,000. Wallace, C.A., and Keller, J.W., 2003, Geologic map of the Castle Rock Gulch quadrangle, Chaffee and Park Counties, Colorado: Colorado Geological Survey, OF-01-01, scale 1:24,000. MMI23
24Year2020MMI24
25TitleGEOLOGIC MAP OF THE AGATE MOUNTAIN QUADRANGLE, PARK COUNTY, COLORADOMMI26
26DOI linkhttps://doi.org/10.58783/cgs.of2002.gfnp2602MMI27
27Open-file numberOF-20-02MMI28

Database Inventory

This summary of database content is provided as a convenience to GIS analysts, reviewers, and others. It is not part of the GeMS compliance criteria.

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