## GeMS validation of OF-22-07_SpinneyMountain.gdb

File written by GeMS_ValidateDatabase.py, version of 5/15/2024
Tue Apr 15 14:49:18 2025
Runtime parameters
Database path: C:\Data\Pangaea\CGS\2022SpinneyMountain\CO_2022_OF-22-07_SpinneyMountain\OF-22-07_SpinneyMountain\OF-22-07_SpinneyMountain_Database\OF-22-07_SpinneyMountain.gdb
Output directory: C:\Data\Pangaea\CGS\2022SpinneyMountain\validation
Metadata file: C:\Data\Pangaea\CGS\2022SpinneyMountain\CO_2022_OF-22-07_SpinneyMountain\OF-22-07_SpinneyMountain\OF-22-07_SpinneyMountain_Database\OF-22-07_SpinneyMountain-metadata_EAP.xml
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.
The database-level FGDC metadata are formally correct although the metadata record should be reviewed to verify that it is meaningful.
This file should be accompanied by OF-22-07_SpinneyMountain.gdb-ValidationErrors.html and OF-22-07_SpinneyMountain-metadata_EAP.xml_errors.txt 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:

- No overlaps or internal gaps in map-unit polygon layer
- Contacts and faults in single feature class
- Map-unit polygon boundaries are covered by contacts and faults lines

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 96 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
OBLIQUEAnno
ObliqueFrame
oblique_line
Fault_Movement_Pts
OrientationPointsAnno
MapUnitPolysAnno
GeochronPointsAnno
ContactsAndFaultsAnno
GeologicLinesAnno
CMUAnno
CMUMapUnitPolysAnno
CSAPoints
CSA_MapUnitPolysAnno
CSACartoLines
CSBPoints
CSBMapUnitPolysAnno
CSBCartoLines

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

MapUnit | DescriptionOfMapUnits | GeologicMap | CrossSectionA | CrossSectionB | CorrelationOfMapUnits
--- | --- | --- | --- | --- | ---
Qaf | X | X | -- | -- | X
Xgb | X | -- | -- | -- | X
PEsp | X | X | X | X | X
PEal | X | X | -- | X | X
Kd | X | X | X | -- | X
Qls | X | X | -- | -- | X
Xgnsf | X | X | -- | -- | X
Xgd | X | X | X | X | X
PEtcw | X | X | -- | -- | X
PEec | X | X | X | -- | X
PEald | X | X | -- | -- | X
Kp | X | X | X | -- | X
Xa | X | X | -- | -- | X
Qsw | X | X | -- | -- | X
Xbgn | X | X | -- | X | X
YXd | X | X | X | -- | X
YXp | X | -- | -- | -- | X
Kn | X | -- | X | -- | X
Jm | X | -- | X | -- | X
Qasp3 | X | X | -- | -- | X
Qgtc2 | X | X | -- | -- | X
Qacg3 | X | X | -- | -- | X
Qatc4 | X | X | -- | -- | X
w | X | X | -- | -- | --
PEalh | X | X | -- | -- | X
Qafo | X | X | -- | -- | X
Na | X | -- | X | -- | X
Xgns | X | X | X | -- | X
Qasp4 | X | X | -- | -- | X
Qa | X | X | -- | -- | X
Yg | X | X | -- | -- | X
Jg | X | -- | X | -- | X
PEwm | X | X | -- | X | X
PEb | X | X | -- | X | X
Qac | X | X | -- | -- | X
Qau | X | X | -- | -- | X
Kb | X | -- | X | -- | X
af | X | X | -- | -- | X
PEalr | X | X | -- | -- | X
PEalf | X | X | -- | X | X
PEtc | X | X | X | -- | X

### Contents of Nonspatial Tables

#### DataSources

OBJECTID | Source | Notes | URL | DataSources_ID
--- | --- | --- | --- | ---
4 | Glossary of geologic terms | None | https://www.americangeosciences.org/pubs/glossary | AGI
8 | BSU Isotope Lab | None | https://www.boisestate.edu/earth-isotope/ | BSU
2 | this study | None | None | DAS1
5 | Online dictionary | None | https://www.merriam-webster.com/dictionary/deposit#dictionary-entry-2 | DICT
1 | Federal 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. | None | https://ngmdb.usgs.gov/fgdc_gds/geolsymstd.php | FGDC-STD-013-2006
3 | GeMS standard | None | https://ngmdb.usgs.gov/Info/standards/GeMS/ | GeMS
7 | OSU Geochronology Lab | None | https://osu-argon.org/ | OSU
6 | USGS Plasma Lab | None | https://www.usgs.gov/media/images/plasma-lab-major-instrumentation | PLASMA

#### DescriptionOfMapUnits

OBJECTID | MapUnit | Name | FullName | Age | Description | HierarchyKey | ParagraphStyle | Label | Symbol | AreaFillRGB | AreaFillPatternDescription | DescriptionSourceID | GeoMaterial | GeoMaterialConfidence | DescriptionOfMapUnits_ID
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
1 | None | SURFICIAL DEPOSITS | SURFICIAL DEPOSITS | None | Colors are determined with the aid of Munsell soil color charts (Munsell Color, 1991). Soil-carbonate development was assessed after Machette (1985). | 01 | DMUHeading1 | None | None | None | None | DAS1 | None | None | DMU01
2 | None | HUMAN-MADE DEPOSITS | HUMAN-MADE DEPOSITS | None | None | 01.01 | DMUHeading2 | None | None | None | None | DAS1 | None | None | DMU02
3 | af | Artificial fill | Artificial fill | uppermost Holocene | Includes riprap and fill placed during the construction of the Spinney Mountain Reservoir dam and associated structures and roadways. The unit generally consists of clay, silt, sand, and rock fragments. The unit may exceed 25 m in thickness. Artificial fill may be subject to settlement, slumping, and erosion if not adequately compacted and (or) if it is placed on unstable slopes. | 01.01.01 | DMUUnit1 | af | af | 255-255-255 | None | DAS1 | "Made" or human-engineered land | High | DMU03
4 | None | ALLUVIAL DEPOSITS | ALLUVIAL DEPOSITS | None | None | 01.02 | DMUHeading2 | None | None | None | None | DAS1 | None | None | DMU04
5 | Qa | Alluvium | Alluvium | Holocene | The unit is unstratified to weakly stratified, poorly sorted silt to sand, and dark yellowish brown (10YR 3/4 and 10YR 3/6) in color. Sand grains are predominantly subround quartz. The unit underlies the modern channel, adjacent floodplains, and low-lying terraces approximately 1.5 m above the modern channel in Chase Gulch, along the South Platte River, and Three Mile Creek. The unit is interbedded with units Qaf and Qsw locally, especially in Chase Gulch and along Three Mile Creek. Epis and others (1979) mapped the unit as Piney Creek Alluvium (Qp). The Piney Creek Alluvium or unit Qa2 along the Colorado Front Range has been dated between 11,950 ± 0.24 cal years BP (bulk carbon; Berry and others, 2015) and 960 ± 30 cal years BP (bulk carbon; Lindsey and others, 2018). Unit Qa postdates unit Qasp3 and Qatc3 in the mapped area and includes Post-Piney Creek Alluvium or unit Qa1 from CGS mapping along the Colorado Front Range, which is Late Holocene in age. The unit is not a likely source of sand and gravel. The unit is hydraulically connected to the South Platte River and underlies areas that are mapped within the 1-percent annual chance flood zone (FEMA Flood Map Service Center). Unit Qa may be as much as 3 m thick. | 01.02.01 | DMUUnit1 | Qa | Qa | 255-255-222 | None | DAS1 | Alluvial sediment | High | DMU05
6 | None | ALLUVIUM OF THE SOUTH PLATTE RIVER | ALLUVIUM OF THE SOUTH PLATTE RIVER | None | None | 01.02.02 | DMUHeading3 | None | None | None | None | DAS1 | None | None | DMU06
7 | Qasp3 | Alluvium three of the South Platte River | Alluvium three of the South Platte River | Lower Holocene and Upper Pleistocene | The unit consists of poorly sorted, clast-supported gravel with a matrix of dark yellowish-brown (10YR 3/4 and 10YR 3/6) silt to coarse sand. Sand grains are predominantly subround to round quartz. Gravel clasts are subround to round and are usually as much as 2.5 cm in diameter but can be as much as 75 cm in diameter. Clast compositions are approximately 60% volcanic breccia and andesite sourced from local bedrock units, 20% tan and white quartzite, 15% pinkish metamorphic rocks, and 5% vein quartz. Clasts have continuous carbonate rinds up to 1 mm thick. The unit differs from Three Mile Creek alluvium in that Three Mile Creek deposits consist almost exclusively of locally derived volcanic rocks. It differs from Chase Gulch alluvium in that clasts in Chase Gulch deposits are predominantly derived from local Precambrian bedrock. The unit is interbedded with Qaf and Qsw locally. The unit was mapped as Wisconsin outwash by Stark and others (1949). Epis and others (1979) later mapped the unit as Pinedale outwash or Pinedale fans. The Pinedale glaciation is correlative with the end of the Wisconsin glaciation in the area and culminated between ~15 and ~14 ka in the area (Young and others, 2011; Schweinsberg and others, 2020). Optically stimulated luminescence samples collected from similar material in secondary drainages in the adjacent (to the west) Guffey NW quadrangle estimate the age of the unit to be between 12,365 ± 570 (SAR) years BP and 20,835 ± 2205 (SAR) years BP. The unit is likely correlative with the Broadway Alluvium or Qa3 in CGS mapping along the Colorado Front Range. The unit is a source of sand and gravel. The unit may be hydraulically connected to the South Platte River and can be as much as 5 m thick. | 01.02.02.01 | DMUUnit2 | Qasp3 | Qasp3 | 255-255-179 | 38-115-0 ESRI 24k Geology 601 gravel, open | DAS1 | Alluvial sediment | High | DMU07
8 | Qasp4 | Alluvium four of the South Platte River | Alluvium four of the South Platte River | upper Middle and Upper Pleistocene | The unit consists of poorly sorted, clast-supported gravel and the matrix is dark-brown (7.5YR 3/3) to dark yellowish-brown (10YR 4/4), silt to coarse sand. Sand grains are predominantly subround to round quartz. Gravel clasts are subangular to subround and are 2.5 cm in diameter. A minor fraction of the clasts is as much as 50 cm in diameter. Clast types are predominantly volcanic breccia, andesite, tan quartzite, and Wall Mountain Tuff (PEwm). Vein quartz and metamorphic rocks comprise as much as 15% of the gravel clasts. Continuous carbonate rinds are present and can be as much as 1.5 mm thick, locally. The unit underlies terraces 20 m above the modern channel. Unit Qasp4 was mapped as the Como Surface, and Wisconsin outwash by Stark and others (1949). They suggest the Como Surface is pre-Illinoian in age. The Pinedale glaciation is correlative with the end of the Wisconsin glaciation in the area and culminated between ~15 and ~14 ka in Colorado (Young and others, 2011; Schweinsberg and others, 2020). Later it was mapped as Bull Lake Outwash (Qbo) by Epis and others (1979). The youngest credible boulders dated from Bull Lake age moraines are approximately 132 to 120 ka, suggesting the Bull Lake glaciation culminated some time after that (Schweinsberg and others, 2020). By virtue of the unit’s height above modern channels and soil development observed in similar material in the adjacent (to the west) Guffey NW quadrangle, the unit is likely late Middle to Late Pleistocene in age. The unit is likely correlative with the Louviers Alluvium or unit Qa4 in CGS mapping along the Colorado Front Range. Unit Qasp4 is not a likely source of sand and gravel and is not hydraulically connected to the South Platte River. Unit Qasp4 is approximately 6 m thick. | 01.02.02.02 | DMUUnit2 | Qasp4 | Qasp4 | 255-255-102 | 38-115-0 ESRI 24k Geology 601 gravel, open | DAS1 | Alluvial sediment | High | DMU08
9 | None | ALLUVIUM OF CHASE GULCH | ALLUVIUM OF CHASE GULCH | None | None | 01.02.03 | DMUHeading3 | None | None | None | None | DAS1 | None | None | DMU09
10 | Qacg3 | Chase Gulch alluvium three | Chase Gulch alluvium three | Lower Holocene and Upper Pleistocene | The unit consists of moderately sorted, pebble-gravel and is brown (10YR 5/3, 4/3) in color. The matrix is fine to coarse sand, comprised predominantly of quartz and feldspar. Pebble clasts are granitic, sourced from nearby Precambrian bedrock. Although soil development is poor, unit Qacg3 effervesces throughout when exposed to dilute hydrochloric acid (HCl). This could be related to groundwater or atmospheric conditions instead of pedogenic processes. The unit underlies terraces approximately 2 m above the ephemeral channel in Chase Gulch and is locally interbedded with unit Qaf. The unit grades laterally into unit Qasp3 but differs from it in that unit Qacg3 has no quartzite clasts and is comprised almost entirely of clasts derived from local Precambrian bedrock. Stark and others (1949) mapped the unit as Wisconsin outwash. Later, Epis and others (1979) mapped it as Pinedale fans (Qpf). The Pinedale glaciation is correlative with the end of the Wisconsin glaciation in the area and culminated between ~15 and ~14 ka in Colorado (Young and others, 2011; Schweinsberg and others, 2020). Since the unit grades laterally into unit Qasp3, the unit is likely Late Pleistocene in age. Unit Qacg3 may be a potential source of sand and gravel and it is likely hydraulically connected to the South Platte River. The unit is as much as 3.5 m thick. | 01.02.03.01 | DMUUnit2 | Qacg3 | Qacg3 | 255-255-179 | 0-169-230 ESRI 24k Geology 601 gravel, open | DAS1 | Alluvial sediment | High | DMU10
11 | None | ALLUVIUM OF THREE MILE CREEK | ALLUVIUM OF THREE MILE CREEK | None | None | 01.02.04 | DMUHeading3 | None | None | None | None | DAS1 | None | None | DMU11
12 | Qatc4 | Alluvium four of Three Mile Creek | Alluvium four of Three Mile Creek | upper Middle and Upper Pleistocene | The unit underlies terraces adjacent to Three Mile Creek and adjacent to unnamed, ephemeral drainages south and southeast of Three Mile Creek. Deposits are mapped as one unit because they are very similar in clast composition and size, and underlie terraces at similar heights. The unit is predominantly clast supported gravel with interbedded sandy layers that are typically dark brown (10YR 3/3) to brown (10YR 4/3) in color. The matrix is poorly sorted silt to coarse sand. Sandier lenses are usually poorly sorted silt and sand. Clast types are subangular to subround and as much as 15 cm in diameter. Clasts are 80% dark gray to black volcanic clasts with lesser amounts of pink metamorphic rocks, and tan- and pink-volcanic clasts. The unit is interlayered locally with units Qaf and Qsw. The unit underlies terraces 10 to 15 m high adjacent to Three Mile Creek and 4 to 14 m high adjacent to unnamed channels. Unit Qatc4 was partially mapped as a part of the Como Surface by Stark and others (1949), which they estimate to be pre-Illinoian in age. Later, Epis and others (1979) mapped it as Bull Lake Alluvium (Qba) or Slocum Alluvium (Qs). The youngest credible boulders dated from Bull Lake age moraines are approximately 132 to 120 ka, suggesting the Bull Lake glaciation culminated sometime after that in the area (Schweinsberg and others, 2020). The Slocum Alluvium has been dated to approximately 160,000 ± 60,000 years BP based on U-series dating of fossil bones and soil development in the Canon City area (Szabo, 1980). Samples collected from the same site and analyzed by OSL techniques yielded age estimates of ~34 to ~38.5 ka (Colorado Geological Survey, unpublished data). These OSL samples were collected near the top of the deposit. The age of the Slocum Alluvium is unclear. The Slocum Alluvium is typically considered pre-Bull Lake, but the Bull Lake glaciation is thought have occurred as early as 200 to 170 ka (Madole, 1991; Kellogg and others, 2009). By virtue of the unit’s height above modern channels and the topographic continuity between surfaces adjacent to unnamed drainages, the unit is likely correlative with the Bull Lake glaciation and is late Middle to Late Pleistocene in age. It is not a likely source of sand and gravel and is likely not hydraulically connected to the South Platte River. The unit is as much as 4 m thick. | 01.02.04.01 | DMUUnit2 | Qatc4 | Qatc4 | 255-255-102 | 169-0-230 ESRI 24k Geology 601 gravel, open | DAS1 | Alluvial sediment | High | DMU12
13 | Qgtc2 | Gravel two of Three Mile Creek | Gravel two of Three Mile Creek | Middle Pleistocene | The unit consists of clast-supported gravel. Matrix was evaluated at the surface and is dark-brown (10YR 3/3) to brown (10YR 4/3) in color. The matrix is poorly sorted silt to sand. Clasts are subround to round and consist of locally derived volcanic clasts that can reach 60 cm in diameter. Clasts mantling the surface of the terrace did not have carbonate rinds. The unit underlies terraces approximately 65 m above modern channels. Epis and others (1979) mapped the unit as Verdos Alluvium (Qv). The Verdos Alluvium has been dated to approximately 620,000 years BP based on the presence of Lava Creek B ash present in some deposits (Madole, 1991). By virtue of the unit’s height above modern channels, the unit is likely correlative with the Verdos Alluvium or unit Qg2 from CGS mapping along the Colorado Front Range. Unit Qgtc2 is not a likely source of sand and gravel and is not hydraulically connected to the South Platte River. The unit is as much as 16 m thick. | 01.02.04.02 | DMUUnit2 | Qgtc2 | Qgtc2 | 255-235-102 | 169-0-230 ESRI 24k Geology 601 gravel, open | DAS1 | Alluvial sediment | High | DMU13
14 | None | MASS-WASTING DEPOSITS | MASS-WASTING DEPOSITS | None | None | 01.03 | DMUHeading2 | None | None | None | None | DAS1 | None | None | DMU14
17 | Qls | Landslide deposits | Landslide deposits | Holocene and Pleistocene | Landslide deposits consist of poorly sorted clay to boulder-sized clasts. Landslide deposits in the mapped area initiate exclusively at or near the contact between either the Tallahassee Creek Conglomerate (PEtc, PEtcw) or the Wall Mountain Tuff (PEwm) and the underlying South Park Formation (PEsp). Landslides are usually rotational, translational, earthflows, or some combination of the three. Younger landslide deposits have well-defined hummocky surface morphology and usually have well-defined head scarps, whereas older landslides have more subdued morphology and may not have well-defined head scarps. Variations in morphology indicate landslides have initiated periodically since at least the Middle Pleistocene. Landslide runouts can be as much as 600 m. Areas with similar geology may be prone to landslide initiation and related hazards. The unit is not a source of sand and gravel. Landslide deposits are as much as 40 m thick. | 01.03.01 | DMUUnit1 | Qls | Qls | 255-255-222 | 0-0-0 ESRI 24k Geology 502 periglacial | DAS1 | Debris flows, landslides, and other localized mass-movement sediment | High | DMU15
19 | None | ALLUVIAL AND MASS-WASTING DEPOSITS | ALLUVIAL AND MASS-WASTING DEPOSITS | None | None | 01.04 | DMUHeading2 | None | None | None | None | DAS1 | None | None | DMU16
15 | Qaf | Alluvial-fan and debris-fan deposits, undivided | Alluvial-fan and debris-fan deposits, undivided | Holocene to upper Middle Pleistocene | The unit is a mixture of alluvium, debris-flow, and alluvial-fan deposits. Debris-flow and alluvial-fan deposits are usually deposited during high seasonal precipitation. Mudflows (hyperconcentrated flows) and debris flows deposit these units in distinct facies. Mudflow facies are poorly sorted mud to medium sand with little to no gravel clasts. Debris-flow facies consist of matrix-supported gravels. The matrix is usually poorly sorted mud to sand, and gravels are angular to subangular clasts sourced from local bedrock. Unit color varies across the mapped area depending on source area geology; deposits sourced from volcanic bedrock are dark brown (10YR 3/3) to brown (10YR 4/3) in color whereas deposits sourced from Precambrian bedrock are brown (10YR 5/3, 4/3) in color. Rainfall from above-average seasonal precipitation entrains sediment from drainage headwalls, valley floors, and, in some cases, landslides. Mudflows and debris flows deposit the unit in fan-shaped lobes on low slopes at the base of relatively narrow, steep, and short ephemeral streams. Predominantly, unit Qaf is a sequence of several distinct deposits emplaced by separate events. An individual event deposit is usually 1 m thick or less. Debris-flow, mudflow, and alluvial-fan deposits are interlayered with alluvium locally. Alluvium is usually homogenous or weakly stratified silt and sand with pebble-gravel lenses less than 5 cm thick. Epis and others (1979) mapped some deposits as Bull Lake Alluvium (Qba). Owing to the height of these deposits above the modern South Platte River, they are likely correlative with the Bull Lake glaciation and are late Middle to Late Pleistocene in age. The youngest credible boulders dated from Bull Lake age moraines are approximately 132 to 120 ka, suggesting the Bull Lake glaciation culminated some time after that (Schweinsberg and others, 2020). Unit Qaf is likely interbedded locally with fluvial gravels but is distinguished from them in that clasts in Qaf deposits are more angular compared to fluvial gravel clasts. The unit also underlies lobate, undulating surfaces compared to fluvial terraces which usually have elongated, relatively flat morphology. Unit Qaf is not a likely source of sand and gravel. Certain deposits close to the South Platte River and Spinney Mountain Reservoir may be hydraulically connected. Areas underlain by the unit may be prone to hazards related to future debris flow and mudflow events. Deposits in the map area are as much as 4 m thick. | 01.04.01 | DMUUnit1 | Qaf | Qaf | 255-255-222 | 255-0-0 ESRI 24k Geology 601 gravel, open | DAS1 | Sediment | High | DMU17
18 | Qsw | Sheetwash alluvium | Sheetwash alluvium | Holocene and Upper Pleistocene | The unit consists of unstratified, homogenous silt to sand with dispersed pebble-sized clasts. Clasts and grains are angular to subround. The unit is derived from the Wall Mountain Tuff (PEwm), the South Park Formation (PEsp), and volcanic bedrock units. Overland flow deposited unit Qsw in apron- and fan-shaped sheets on relatively moderate to low slopes sporadically throughout the Holocene and Late Pleistocene. The unit is interbedded with unit Qaf and Qatc4 locally. Unit Qsw is not a source of sand and gravel and is not hydraulically connected to the South Platte River. Areas underlain by the unit may be prone to flooding and debris flows during years with high seasonal precipitation. The unit is probably as much as 2 m thick. | 01.04.02 | DMUUnit1 | Qsw | Qsw | 255-255-222 | 0-0-0 ESRI 24k Geology 607 sand | DAS1 | Alluvial sediment | None | DMU18
20 | Qac | Alluvium and colluvium, undivided | Alluvium and colluvium, unidived | Holocene and Pleistocene | The unit consists of poorly sorted sand and gravel. Gravel clasts are locally derived, angular to subangular clasts as much as 0.5 m in diameter. Gravity deposits colluvium as a wedge-shaped apron on steep to moderate slopes below steep bedrock exposures. Areas underlain by unit Qac may be subject to rockfall and associated hazards. The unit is as much as 2 m thick. | 01.04.03 | DMUUnit1 | Qac | Qac | 255-255-222 | 0-0-0 ESRI 24k Geology 605 breccia, open | DAS1 | Sediment | High | DMU19
21 | Qau | Alluvium, sheetwash, and debris-flow deposits, undivided | Alluvium, sheetwash, and debris-flow deposits, unidivided | Holocene and Upper Pleistocene | The unit consists of interbedded debris-flow, sheetwash, and alluvial deposits of varying ages underlying ephemeral channels. Where Precambrian clasts crop out in the source area, the unit is brown (10YR 5/3, 4/3) in color, compared to dark brown (10YR 3/3) to brown (10YR 4/3) in areas the unit is derived from volcanic bedrock. Debris-flow deposits are matrix-supported gravel deposits. Clasts are angular to subangular and as much as 0.3 m in diameter. Debris-flow deposits are as much as 1 m thick. Sheetwash alluvium is homogenous to stratified silty sand to pebble gravel. Clasts are angular to subangular. Alluvial deposits are usually silty sand to coarse sand and range from homogenous to well-stratified. Soil development ranges widely across the mapped area, from no soil development to A/Bt/Bk sequences with Stage II carbonate development. Sediments are usually deposited during high-energy, high-volume storm events (Barkmann and others, 2018). The unit is not a source of sand and gravel. The unit is locally hydraulically connected to the South Platte River. Areas underlain by the unit may be prone to flooding and debris flows, and their related hazards. The unit is typically 1.5 m thick. | 01.04.04 | DMUUnit1 | Qau | Qau | 255-255-222 | 0-0-0 ESRI 24k Geology 601 gravel, open | DAS1 | Sediment | High | DMU20
16 | Qafo | Old alluvial-fan and debris-fan deposits, undivided | Old alluvial-fan and debris-fan deposits, undivided | upper Middle to Middle Pleistocene | The unit consists of poorly sorted gravel with a clay and sand matrix and color varies across the mapped area depending on source area geology. In the north part of the mapped area, Precambrian bedrock crops out in source areas for Qafo deposits. The unit is usually brown (10YR 5/3, 4/3) in color and Precambrian clasts in these deposits are angular to subround and generally pebble-sized. Thin (<2 m) Qafo deposits mantle surfaces with lobate, undulating morphology approximately 8 to 10 m above modern channels. In many locations, bedrock is within 1 m of the surface and crops out along the edges of the deposits. In the southeastern part of the mapped area, volcanic bedrock is the predominant unit that crops out in source areas for Qafo deposits, and the unit is usually dark brown (10YR 3/3) to brown (10YR 4/3) in color. Angular to subround brown to gray volcanic clasts 15 cm in diameter mantle surfaces 2.5 to 6 m high. The unit is topographically higher than unit Qaf. The unit differs from fluvial gravel in that clasts in unit Qafo are more angular and unit Qafo underlies lobate, undulating surfaces compared to fluvial terraces which usually have elongated and relatively flat morphology. Epis and others (1979) mapped these deposits as Bull Lake Alluvium (Qba). The youngest credible boulders dated from Bull Lake age moraines are approximately 132 to 120 ka, suggesting the Bull Lake glaciation culminated some time after that (Schweinsberg and others, 2020). By virtue of heights above stream channels and the level of erosion of the surfaces, deposits in the north part of the map area are likely older than those in the southeastern part of the map area. They may be as old as early Middle Pleistocene. Deposits in the southeastern part of the mapped area are likely late Middle to Late Pleistocene in age. Unit Qaf is likely interbedded with fluvial gravel locally. The unit is as much as 4 m thick. | 01.04.05 | DMUUnit1 | Qafo | Qafo | 255-255-179 | 255-0-0 ESRI 24k Geology 601 gravel, open | DAS1 | Sediment | High | DMU21
22 | None | BEDROCK GEOLOGY | BEDROCK GEOLOGY | None | Bedrock unit classifications follow those of Carpenter and others (2016). Chemical classification of extrusive igneous rocks is that of Le Bas and others (1986). Chemical classification of intrusive igneous rocks is that of Middlemost (1994) and Frost and Frost (2008). Geologic terms follow the definitions of Neuendorf and others (2005). | 02 | DMUHeading1 | None | None | None | None | DAS1 | None | None | DMU22
23 | Na | Arkosic sandstone and conglomerate | Arkosic sandstone and conglomerate | Neogene? | Poorly lithified, arkosic sandstone and conglomerate with a minimum thickness of 500 m. Shown only on cross-section. | 02.01 | DMUUnit1 | Na | Na | 254-232-187 | None | DAS1 | Clastic sedimentary rock | High | DMU23
24 | PEtc | Tallahassee Creek Conglomerate | Tallahassee Creek Conglomerate | Eocene | Orangish-tan to greenish-gray boulder conglomerate. Though boulders are the most noticeable constituent, all sizes of gravel are present in a matrix of muddy, tuffaceous sandstone. Some of the boulders are up to 2 m in diameter. West of County Rd. 59, they include local rock types such as granitic gneiss, granite, pegmatite, Thirtynine Mile Andesite, and Wall Mountain Tuff. In some places, the uppermost part of the formation consists entirely of boulders of Wall Mountain Tuff (tuff boulder lithofacies, described separately below). East of County Rd. 59, only granitic boulders are present. The Tallahassee Creek Conglomerate lacks bedding, and the gravel clasts are matrix-supported. The conglomerate forms low, boulder-strewn hills north and east of the Thirtynine Mile Andesite, and south of Spinney Mountain. It appears to have filled paleovalleys on a landscape with considerable topographic relief. The Tallahassee Creek Conglomerate overlies the Balfour and South Park formations, and the Thirtynine Mile Andesite with angular unconformity. Rockfall is common around the sides of conglomerate-capped hills. The formation is approximately 2 to 36 m thick. | 02.02 | DMUUnit1 | :tc | PEtc | 255-179-102 | None | DAS1 | Clastic sedimentary rock | High | DMU24
25 | PEtcw | Tallahassee Creek Conglomerate, tuff boulder lithofacies | Tallahassee Creek Conglomerate, tuff boulder lithofacies | Eocene | This lithofacies is similar to the rest of the Tallahassee Creek Conglomerate, except that the boulders consist almost entirely of blocks of Wall Mountain Tuff up to 2 m in diameter. The lithofacies weathers to form fields of tuff boulders that resist weathering and cap ridges. On the quadrangle, this lithofacies occurs in two places near outcrops of Wall Mountain Tuff. The outcrop on the boundary between sec. 6 and 7, T. 13 S., R. 73 W., is especially striking because the tuff blocks extend from the tuff outcrop in a narrow band and appear to fill a meandering paleochannel. The tuff boulder lithofacies is conformable with the remainder of the Tallahassee Creek Conglomerate. Approximately 20 miles southwest of the mapped area, Epis and Chapin (1974) described a similar unit, which they called the Stirrup Ranch Tuff. Lipman and Bachman (2015) reinterpreted the Stirrup Ranch Tuff as flood deposits derived from the Wall Mountain Tuff. The boulder tuff lithofacies on the Spinney Mountain quadrangle appears to be very similar to the Stirrup Ranch Tuff, if not the same unit. However, further mapping is needed to confirm or disprove this hypothesis. The thickness of the lithofacies is variable, ranging from 6 to 36 m. | 02.02.01 | DMUUnit2 | :tcw | PEtcw | 235-153-0 | None | DAS1 | Clastic sedimentary rock | High | DMU25
26 | PEal | Thirtynine Mile Andesite, lower member | Thirtynine Mile Andesite, lower member | Eocene | Gray to very dark-gray and purplish-gray volcanic breccia and massive volcanic rocks of mostly andesitic composition. Matrix-supported conglomerate is a minor constituent. Breccias compose >80% of the unit, and the remaining <20% is composed of massive volcanic rock and conglomerate. Unit PEal is correlative with the middle andesite series of Barkmann and others (2018) and appears to be correlative with the lower member of the Thirtynine Mile Andesite of Epis and Chapin (1974). Four units within the lower member are mapped separately, and are described below. These include a unit with thicker and more abundant lava flows (unit PEalf) in the upper part of the member, a hornblende andesite porphyry flow (PEalh), a diorite plug (PEald), and some small rhyodacite flows, dikes, and plugs (PEalr). The breccias are composed of sand- to cobble-sized angular fragments of aphanitic to porphyroaphanitic igneous rocks in a matrix of similar appearance. Some breccias are matrix-supported, and some are clast-supported. Pyroxene is the most common phenocryst, though plagioclase and rarely hornblende were also observed. These breccias are interpreted to be autobreccias where matrix lithology and monomict clast lithology are identical. Unbrecciated volcanic rocks are also present in a myriad of small flows, dikes, and plugs. The lithology is similar to that of the volcanic breccias. Dikes are approximately 2 to 5 m wide, and flows are 1 to 2 m thick. Compositionally these rocks are mostly andesite and basaltic andesite, though minor basalt is also present. Geochemical analysis of a representative sample from the Antero NE quadrangle yielded a trachyandesite composition. Sanidine from that sample yielded an 40Ar/39Ar single crystal fusion mini-plateau age of 34.44 ± 0.05 Ma (Barkman and others, 2018). Volcanic layering in the flows is about 15 cm to 1 m thick. Both the brecciated and unbrecciated volcanic rocks are magnetic to varying degrees, and some contain vesicles filled with zeolites. Two types of volcaniclastic conglomerates occur in the unit. One is composed of pebble- to cobble-sized clasts of Thirtynine Mile Andesite in a matrix of reddish-to orangish-brown muddy sand. It is clast-supported but lacks bedding. The other is composed of granule- to cobble-sized clasts of glassy Thirtynine Mile Andesite in a matrix of light-gray vitric tuff. It occurs in beds 5 to 25 cm thick. These are interpreted as volcaniclastic debris-flow and alluvial deposits. The lower member is relatively nonresistant, and crops out poorly. It underlies gentle, rolling, grassy hills, through which groundwater migrates readily. The dikes, flows, and plugs are somewhat more resistant and less permeable than the breccias. The dikes tend to be aligned with the structural grain of the map area. North-northwest is the most prevalent orientation, but east-northeast is also common. The dikes appear to have been formed by magma intruding cracks and fissures in the highly fractured footwall of the Elkhorn fault system. Unit PEal makes a gradational contact with unit PEb. The contact is defined at the base of the lowest lava flow or breccia. Thickness is about 42 m. | 02.03 | DMUUnit1 | :al | PEal | 207-191-242 | None | DAS1 | Extrusive igneous material | High | DMU26
27 | PEalf | Flow-rich facies | Thirtynine Mile Andesite, flow-rich facies | Eocene | This facies occurs in the upper part of the member. Lithologically it is similar to the rest of the lower member in that most of the rocks are andesite or basaltic andesite with minor basalt. A basalt porphyry on Rogers Mountain is 63% plagioclase, 25% pyroxene, 10% magnetite, and 2% hornblende. Geochemically it is 47.3% SiO2, 15.7% Al2O3, 11.8% Fe2O3, 8.45% CaO, 5.82% MgO, 3.24% Na2O, 2.34% K2O, 0.008% Cr2O3, 1.64%TiO2, 0.18% MnO, 0.68% P2O5, 0.13% SrO, and 0.16% BaO (trachybasalt). Unbrecciated lava flows tend to be thicker (3 to 15 m), more extensive, and more numerous in comparison to the rest of the lower member. They make up >20% of the unit. The flow-rich facies is also more resistant to erosion. It forms steeper topography, and the lava flows tend to form ledges. The flows also form barriers to groundwater infiltration, perching the water table. Trees and lush vegetation can grow in places. Marshes, bogs, and springs are common. The contact with the lower part of unit PEal is gradational and is defined where the topography becomes noticeably steeper and more ledgy. The flow-rich facies appears to be transitional between the lower part of the lower member with its sparse, thin, brecciated flows, and the upper member of the Thirtynine Mile Andesite, with its abundant thick, unbrecciated flows. Rockfall is a hazard around ledges. As much as 200 m of the facies are exposed in the map area. | 02.03.01 | DMUUnit2 | :alf | PEalf | 170-102-205 | None | DAS1 | Extrusive igneous material | High | DMU27
28 | PEalr | Rhyodacite dikes and flows | Thirtynine Mile Andesite, rhyodacite dikes and flows | Eocene | Orangish-pink rhyodacite porphyry that weathers to reddish-brown. Phenocrysts of biotite, hornblende, and plagioclase are < 1 mm in diameter. The rock is about 14% plagioclase phenocrysts, 1% biotite phenocrysts, 4% hornblende phenocrysts, and 81% microcrystalline feldspar laths. The laths and phenocrysts are flow-aligned. Geochemically it is 69.3% SiO2, 16.8% Al2O3, 2.14% Fe2O3, 2.15% CaO, 0.38% MgO, 4.13% Na2O, 5.20% K2O, 0.003% Cr2O3, 0.38% TiO2, 0.02% MnO, 0.17% P2O5, 0.07% SrO, and 0.24% BaO (borderline rhyolite/trachydacite). In places it is thinly layered (5 to 10 cm) but there are also thicker breccia layers (1 to 3 m). The unit is resistant to erosion and tends to form ridges. Contacts are sharp. The flow in the southwestern corner of the map area has a basal ash layer and a vitrophyre. Dating of biotite in this flow yielded an 40Ar/39Ar plateau age of 34.73 ± 0.08 Ma. Though its composition is significantly different from the rest of the lower andesite member, the date shows that the rhyodacite is approximately coeval with it, and thus is likely a part of it. Rockfall is a hazard on slopes. The flow is about 36 m thick, and the dikes are 5-10 m thick. | 02.03.02 | DMUUnit2 | :alr | PEalr | 223-115-255 | None | DAS1 | Igneous rock | High | DMU28
29 | PEalh | Hornblende andesite flow | Thirtynine Mile Andesite, hornblende andesite flow | Eocene | Very dark-gray hornblende andesite porphyry that weathers to dark reddish-gray. Phenocrysts of hornblende and plagioclase are <3mm in diameter. Plagioclase phenocrysts are zoned and albite-twinned. The phenocrysts occur in a matrix of flow-aligned, microcrystalline plagioclase. The rock is 89% microcrystalline plagioclase, 9% plagioclase phenocrysts, and 2% hornblende phenocrysts. Minor glass and magnetite are also present. Geochemically it is 59.3% SiO2, 17.6% Al2O3, 4.42% Fe2O3, 3.89% CaO, 1.17% MgO, 3.92% Na2O, 4.60% K2O, 0.003% Cr2O3, 0.54% TiO2, 0.14% MnO, 0.26% P2O5, 0.07% SrO, and 0.13% BaO (trachyandesite). Parts of the flow are vesicular; the vesicles are filled with zeolites. The unit forms ridges with a sharp lower contact. Rockfall is a hazard on slopes. A maximum thickness of 85 m is exposed on the quadrangle. | 02.03.03 | DMUUnit2 | :alh | PEalh | 212-128-194 | None | DAS1 | Intermediate-composition lava flows | High | DMU29
30 | PEald | Diorite plug | Thirtynine Mile Andesite, diorite plug | Eocene | Medium-gray, fine-grained diorite, weathering to light reddish-gray. The mineral composition of the rock is 66% plagioclase, 22% olivine, 3% pyroxene, and 9% magnetite. Geochemically it is a monzodiorite with 50.1% SiO2, 16.4% Al2O3, 11.0% Fe2O3, 6.58% CaO, 4.17% MgO, 3.68% Na2O, 3.50% K2O, 0.004% Cr2O3, 1.43% TiO2, 0.20% MnO, 1.01% P2O5, 0.15% SrO, and 0.19% BaO. The plug contains no discernable structure. It resists erosion and forms a prominent hill. Its contact with the surrounding rock is sharp. Rockfall is a hazard on slopes. Approximately 24 m of the plug are exposed in the map area. | 02.03.04 | DMUUnit2 | :ald | PEald | 168-0-132 | None | DAS1 | Intrusive igneous rock | High | DMU30
31 | PEb | Balfour Formation | Balfour Formation | Eocene | Volcaniclastic sandstone, siltstone, and shale. The sandstone is light tan, weathering to orangish tan or orangish brown. It is a fine to coarse, and commonly contains granules. It is a matrix-rich lithic sandstone with numerous volcaniclasts and rip-up clasts of white tuffaceous mudstone. Coarser beds may be up to 15 cm thick; finer beds are about 3 to 5 cm thick, and are commonly interbedded with siltstone or shale. Siltstone and mud shale are gray to tan in color and weather to orangish tan. They are commonly laminated, fissile, brittle, and tuffaceous. 40Ar/39 dating of sanidine in a tuff sample on the Guffey NW quadrangle (Houck and others, 2025) yielded an age of 34.81 +/- 0.04 Ma. This age is slightly older than that of unit PEal, which overlies it. Soft sediment deformation occurs in unit PEb, especially in S ½ sec. 12, T. 13 S., R. 74 W. The unit forms valleys with gentle slopes. It weathers into yellowish-brown silty soils that are highly prone to sheetwash, making it poorly exposed. On the quadrangle, it is present only south of the Gulch Road fault and west of the Rogers Ranch fault. Its thickness in the map area does not exceed 30 m. | 02.04 | DMUUnit1 | :b | PEb | 242-224-255 | None | DAS1 | Sedimentary and extrusive igneous material | High | DMU31
32 | PEwm | Wall Mountain Tuff | Wall Mountain Tuff | Eocene | Light orangish-pink, densely welded, crystal-vitric ash flow tuff that weathers to tan. The tuff is rhyolitic in composition. Crystals include clear sanidine and black biotite. Secondary quartz is common. Volcanic layering is about 1 cm thick and is defined by flattened pumice clasts 2 to 3 cm long. A single-crystal total fusion 40Ar/39Ar analysis of sanidine from a sample collected on the Antero Northeast quadrangle (Barkmann and others, 2018) yielded an age of 37.07 ± 0.08 Ma. The Wall Mountain Tuff is resistant to erosion and forms prominent ridges. It nonconformably overlies Proterozoic rocks and overlies the South Park Formation with angular unconformity. Rockfall is a hazard on slopes. A maximum of approximately 115 m is exposed in the map area. | 02.05 | DMUUnit1 | :wm | PEwm | 135-33-255 | None | DAS1 | Felsic-composition pyroclastic flows | High | DMU32
33 | PEec | Elkhorn conglomerate | Elkhorn conglomerate | Paleocene? | Yellowish-tan to yellowish-brown, very poorly lithified, boulder conglomerate. The conglomerate is composed of subrounded granules, pebbles, cobbles, and boulders in a sandy, silty matrix. Clasts are the detritus of Proterozoic igneous and metamorphic rocks such as granite, pegmatite, and granite gneiss, that occur in the adjacent hanging wall of the Elkhorn thrust fault. The conglomerate is matrix-supported and is weakly bedded. The unit forms a steep apron on the downthrown side of the Elkhorn fault. It lies with angular unconformity over Cretaceous rocks. Its relationship with the Proterozoic rocks is variable. It may overlie them nonconfomably, or be in fault contact with them. Examples of both occur on the Elkhorn quadrangle (Ruleman and Bohannon, 2008) and the Sulphur Mountain quadrangle (Bohannon and Ruleman, 2009). It is interpreted to be equivalent to the Elkhorn conglomerate of Barkmann and others (2017), the syntectonic conglomerate of Ruleman and others (2011), the Elkhorn thrust conglomerate of Ruleman and Bohannon (2008), and the conglomerate and breccia of Bohannon and Ruleman (2009). It is thought to be derived from a local scarp created by the hanging wall of the Elkhorn thrust fault (Bohannon and Ruleman, 2009). Detrital zircon analysis of 134 zircon grains yielded 130 grains with an average age of 1708.2 Ma, 3 grains with an average age of 1509 Ma, and one grain with an age of 63.5 Ma. Thus, the maximum depositional age of the unit is Paleocene. Though the unit could be younger, one might expect that the abundant Eocene, Oligocene, and Miocene volcanic activity in the area would have contributed younger zircons. The Elkhorn conglomerate produces numerous falling rocks. Boulders in the unit are used for landscaping at Spinney Mountain State Park. Thickness in the map area is as much as 60 m. | 02.06 | DMUUnit1 | :ec | PEec | 255-235-179 | 0-0-0 ESRI 24k Geology 605 breccia, open | DAS1 | Clastic sediment | High | DMU33
34 | PEsp | South Park Formation, undivided | South Park Formation, undivided | Paleocene | Poorly exposed volcaniclastic mudstone, sandstone, and conglomerate. The sandstones and conglomerates are light grayish tan to peach-colored. Conglomerates contain granules, pebbles, and cobbles of K-feldspar, chert, quartz, and quartzite that are subangular to subrounded. The basal part of the section also contains well-rounded cobbles of gray-green to tan intermediate volcanic rocks that are diagnostic of the South Park Formation in the mapped area. Sandstones, some of which are conglomeratic, are matrix-rich, fine to coarse, and poorly sorted. They are feldspathic and lithic. Some of the sandstones and conglomerates are massive and matrix-supported. Others are clast-supported, and occur in thin beds, or in trough cross-bed sets about 15 cm thick. Mudstones are bright red to dark reddish-brown. They lack bedding, and break into clasts about 5 mm in diameter. In comparison to quadrangles to the west and northwest, the South Park Formation on the Spinney Mountain quadrangle has a higher proportion of mudstone and sandstone that is easily eroded. It has a lower proportion of conglomerate and lacks boulder conglomerate, which tends to be more resistant. Consequently, it is a valley former in the mapped area, with sparse ridges underlain by conglomerate beds. It nonconformably overlies Proterozoic rocks east of the Rogers fault. West of the Rogers fault it presumably overlies the Cretaceous rocks with angular unconformity, as it does on the Guffey NW quadrangle. However, this isn’t known with certainty. It is prone to swelling soils. A thickness of about 45 to 60 m is exposed on the quadrangle. | 02.07 | DMUUnit1 | :sp | PEsp | 235-204-153 | None | DAS1 | Clastic sedimentary rock | High | DMU34
35 | Kp | Pierre Shale | Pierre Shale | Upper Cretaceous | Medium- to dark-gray, fissile, predominantly calcareous shale with thin (< 10 cm) beds of brownish-gray to olive-drab sandstone and siltstone. The Pierre Shale is recessive and outcrops are rare on the quadrangle. It weathers to form soft, collapsible, olive-tan soil. It may have a “popcorn” appearance from swelling and shrinking of clay. On the adjoining Guffey NW quadrangle the Pierre Shale conformably overlies the Niobrara Formation. It is prone to landslides and swelling soils. In areas where strata are dipping, the overlying soils may be prone to heaving. With the exception of sandstone beds and local fracturing, the Pierre Shale has very limited potential to yield water to wells. Sawatzky (1967) estimated that the unit may be up to 1,585 m thick in South Park, but less than 25 m are exposed on the quadrangle. | 02.08 | DMUUnit1 | Kp | Kp | 204-255-153 | None | DAS1 | Clastic sedimentary rock | High | DMU35
36 | Kn | Niobrara Formation | Niobrara Formation | Upper Cretaceous | Chalky limestone and shale, approximately 60 m thick. Shown only on cross-section. | 02.09 | DMUUnit1 | Kn | Kn | 235-255-179 | None | DAS1 | Sedimentary rock | High | DMU36
37 | Kb | Benton Group | Benton Group | Upper Cretaceous | Gray shale with minor limestone and sandstone, approximately 85 m thick. Shown only on cross-section. | 02.10 | DMUUnit1 | Kb | Kb | 153-173-128 | None | DAS1 | Sedimentary rock | High | DMU37
38 | Kd | Dakota Sandstone | Dakota Sandstone | Lower Cretaceous | Cream-colored, fine- to medium-grained quartz sandstone in thick laminae defined by normally graded beds. An outcrop is exposed in the footwall of the Elkhorn thrust fault that is highly fractured and is steeply dipping to overturned. On the adjoining Guffey NW quadrangle it is approximately 70 m thick in the McDannald #1 stratigraphic test (API 05-093-5007; sec. 32, T. 11 S., R. 75 W.). In the well it sits disconformably on the Morrison Formation. However, only a few meters of Dakota Sandstone are exposed on the Spinney Mountain quadrangle. | 02.11 | DMUUnit1 | Kd | Kd | 179-205-102 | None | DAS1 | Mostly sandstone | High | DMU38
39 | Jm | Morrison Formation | Morrison Formation | Upper Jurassic | Variegated mudstone, siltstone, and sandstone, approximately 45 m thick. Shown only on cross-section. | 02.12 | DMUUnit1 | Jm | Jm | 43-194-141 | None | DAS1 | Clastic sedimentary rock | High | DMU39
40 | Jg | Garo Sandstone | Garo Sandstone | Jurassic | Pinkish-tan quartz sandstone, approximately 40 m thick. Shown only on cross-section. | 02.13 | DMUUnit1 | Jg | Jg | 6-140-108 | None | DAS1 | Mostly sandstone | High | DMU40
41 | Yg | Equigranular medium-grained granite | Equigranular medium-grained granite | Mesoproterozoic | Light gray, light pinkish-gray, or light orangish-gray medium-grained hypidiomorphic granular biotite-bearing granite. Modal mineralogy includes anhedral to subhedral quartz with undulatory extinction, subhedral alkali feldspar, subhedral plagioclase and subhedral biotite. Locally muscovite and (or) garnet-bearing. Geochemical samples plot in the granite field of the plutonic TAS diagram of Middlemost (1994) and are ferroan, peraluminous, and alkali-calcic by the classification diagrams of Frost and Frost (2008). Unit Yg occurs as dikes cutting unit Xgd, up to ~150 m wide, that most commonly follow unit Xgd foliation but are also observed to cut foliation where the host rock is low-strain. Locally, unit Yg has a weak foliation defined by aligned biotite that parallels the fabric in unit Xgd, which could suggest that intrusion of unit Yg was late synkinematic to deformation that imparted foliation to unit Xgd. | 02.14 | DMUUnit1 | Yg | Yg | 133-155-163 | None | DAS1 | Intrusive igneous rock | High | DMU41
42 | YXd | Quartz diorite dike | Quartz diorite dike | Paleoproterozoic or Mesoproterozoic | Dark-gray, fine- to medium-grained hypidiomorphic granular biotite quartz diorite. Composed of aligned bronze-black biotite, recrystallized quartz with undulatory extinction, plagioclase, and minor secondary magnetite. Unit YXd occurs at a single locality southeast of Spinney Mountain where it intrudes unit Xgd. Unit YXd is best exposed where transected by a roadcut and outcrop is otherwise limited to hillslope subcrop. Foliation and lineation within unit YXd are defined by aligned biotite and parallel the fabric within the surrounding unit Xgd. | 02.15 | DMUUnit1 | YXd | YXd | 179-153-102 | None | DAS1 | Intrusive igneous rock | High | DMU42
43 | YXp | Pegmatite dikes | Pegmatite dikes | Proterozoic | Pink, white, and pinkish-gray pegmatitic granite and alkali feldspar granite. Composed of pink euhedral or subhedral, commonly perthitic alkali feldspar, subhedral or anhedral quartz, and subhedral myrmekitic plagioclase, with sparse euhedral muscovite and rare euhedral or subhedral tourmaline. Observed pegmatite dikes are generally not zoned. Unit YXp occurs as decimeter- to meter-scale thickness dikes intruding other Proterozoic units. Unit YXp dikes that intrude unit Xgns are most commonly parallel to the gneissic foliation in that unit and less commonly cut foliation. Unit YXp dikes that intrude unit Xgd most commonly parallel foliation in that unit, though dikes cutting foliation are also observed. Mapped dikes generally form outcrop ridges more resistant than the units they intrude. Numerous pegmatite dikes with widths smaller than mappable scale are not depicted on the map. | 02.16 | DMUUnit1 | YXp | YXp | None | 255-0-0 01.03.01 | DAS1 | Coarse-grained, felsic-composition intrusive igneous rock | High | DMU43
44 | Xgd | Porphyritic granodioritic gneiss | Porphyritic granodioritic gneiss | Paleoproterozoic | Pinkish-gray, weakly foliated, coarse-grained hypidiomorphic porphyritic biotite granodioritic and granitic augen gneiss. Modal mineralogy includes subhedral plagioclase, pink subhedral or euhedral alkali feldspar, anhedral quartz, and biotite. Locally, unit Xgd is muscovite- or hornblende-bearing. Light sericitic alteration of feldspar and chloritic alteration of mica are present in most samples, as are epidote-rimmed opaque Fe-oxide alteration products. Where unstrained, alkali feldspar phenocrysts are as large as 7 cm, and are commonly poikilitic with inclusions of biotite, quartz, or plagioclase. Centimeter- to meter-scale biotite-rich enclaves are common, as are foliated xenoliths of unit Xgbn near the contact with that unit. Geochemical samples span the granodiorite and granite fields of the plutonic TAS diagram of Middlemost (1994) and are ferroan, calcic to calc-alkalic, and peraluminous by the classification diagrams of Frost and Frost (2008). U-Pb zircon analysis yielded an age of 1712.9±6.4 Ma. Most commonly, unit Xgd has a subplanar, gently undulating, north-dipping foliation defined by aligned biotite and a weak down-dip lineation defined by elongate clots of biotite. In localized shear zones where the unit is more highly strained, the foliation and lineation are defined by recrystallized quartz and feldspar. Unit Xgd is the most aerially extensive Proterozoic unit in the mapped area and is found in both the hanging wall and footwall of the Elkhorn thrust. This unit forms cliffs near Stoll Mountain, and foliation-parallel bedrock ledges on pediment surfaces. Unit Xgd intrudes units Xa, Xbgn, and Xgns. Rockfall is a hazard on slopes. | 02.17 | DMUUnit1 | Xgd | Xgd | 128-179-179 | None | DAS1 | Metamorphic rock | High | DMU44
45 | Xgb | Gabbro dike | Gabbro dike | Paleoproterozoic | Dark greenish-gray, biotite-bearing hornblende gabbro dike. Orangish-brown on weathered outcrops and erodes easily to greenish-gray grus. Medium-grained, hypidiomorphic, and inequigranular. Composed of sericitized tabular plagioclase, serpentinized clinopyroxene, subhedral amphibole and red-brown pleochroic biotite. Unit Xgb occurs at a single locality on the southeastern slope of Spinney Mountain as a meter- to decameter-scale thick dike where it intrudes unit Xgns and is intruded by unit Xgd. A geochemical sample of unit Xgb plots in the gabbro field of the plutonic TAS diagram of Middlemost (1994) and in the tholeiitic field on the AFM diagram of Irvine and Baragar (1971). | 02.18 | DMUUnit1 | Xgb | Xgb | None | 255-0-0 01.03.03 | DAS1 | Intrusive igneous rock | High | DMU45
46 | Xa | Amphibolite | Amphibolite | Paleoproterozoic | Dark-gray or dark greenish-gray, fine-grained biotite amphibolite. Granofelsic to weakly foliated, with foliation defined by aligned amphibole and biotite. Contains prismatic subhedral hornblende, equant to tabular subhedral and anhedral plagioclase, anhedral quartz, and minor chloritized biotite. Sparse clots of recrystallized plagioclase as large as 12 mm and hornblende as large as 6 mm may be relict phenocrysts and could suggest an originally porphyritic texture. A geochemical sample of unit Xa plots at the boundary of the basalt and basaltic andesite fields of a TAS diagram (Le Bas and others, 1986) and in the calc-alkaline field of an AFM diagram (Irvine and Baragar 1971). Unit Xa occurs in a single locality northeast of Elevenmile Reservoir, where it is intruded by units Xgd and Yg. | 02.19 | DMUUnit1 | Xa | Xa | 179-179-102 | None | DAS1 | Metamorphic rock | High | DMU46
47 | Xbgn | Biotite Gneiss | Biotite Gneiss | Paleoproterozoic | Light-gray to gray, fine to medium-grained biotite granodioritic gneiss. Most outcrops have foliation defined by gneissic layering or stromatic migmatitic texture, but are gradational into low-strain zones of fine- to medium-grained hypidiomorphic granular biotite granite and granodiorite. Low-strain zones have equant subhedral alkali feldspar, zoned tabular subhedral plagioclase, anhedral quartz, fine-grained anhedral biotite, and are locally muscovite-bearing. Gneissic foliation within unit Xbgn is either parallel or slightly oblique to the foliation within unit Xgd. Folding of foliation is common, typically as decimeter-scale open folds but also as cm-scale ptygmatic folding. A single geochemical sample plots in the granite field of the plutonic TAS diagram of Middlemost (1994) and is ferroan, calc-alkalic, and peraluminous by the classification diagrams of Frost and Frost (2008). Unit Xbgn is exposed in rounded topographic knobs on Stoll Mountain where it is intruded by unit Xgd. Xenoliths of unit Xbgn are present within unit Xgd; most are only a few meters in diameter but one is sufficiently large to be depicted on the map. | 02.20 | DMUUnit1 | Xbgn | Xbgn | 222-204-179 | None | DAS1 | Metamorphic rock | High | DMU47
48 | Xgns | Spinney Mountain gneiss and schist, undivided | Spinney Mountain gneiss and schist, undivided | Paleoproterozoic | Unit Xgns includes a lithologically complex suite of gneiss and schist. The dominant lithologies are banded quartzofeldspathic biotite gneiss, light-gray, weakly foliated, fine-grained biotite (± muscovite) granitic gneiss, and silvery-gray, garnet-bearing biotite muscovite quartz schist, with lesser proportions of dark-gray, fine- to medium-grained granofelsic amphibolite, and stromatic migmatite with granitic leucosome and biotite gneiss melanosome. A feldspathic subunit (Xgnsf) is mapped separately (see below). Unit Xgns is intruded by numerous pegmatitic, granodioritic, and aplitic dikes most commonly parallel to foliation. Map-scale pegmatite dikes are depicted separately as unit YXp but smaller dikes are not separated. Gneissic and schistose foliation dips steeply to shallowly west-southwest. Lineation defined by aligned biotite or recrystallized quartz and feldspar plunges shallowly south on average. Rockfall is a hazard on slopes. | 02.21 | DMUUnit1 | Xgns | Xgns | 179-204-204 | None | DAS1 | Metamorphic rock | High | DMU48
49 | Xgnsf | Spinney Mountain gneiss, feldspathic subunit | Spinney Mountain gneiss, feldspathic subunit | Paleoproterozoic | Dominated by dark-gray, medium-grained biotite granodiorite and granodioritic gneiss. Where low strain, hypidomorphic granular granodiorite includes subhedral alkali feldspar, subhedral plagioclase, anhedral or subhedral biotite, anhedral quartz, and locally trace amounts of muscovite. Higher strain domains have gneissic banding but lack the lithologic diversity of unit Xgns. Weakly to strongly foliated with foliation defined by aligned platy biotite that wraps around feldspar clasts. Lineation is defined by aligned elongate axes of biotite and recrystallized tails of quartz and feldspars. A single geochemical sample plots in the granodiorite field of the plutonic TAS diagram of Middlemost (1994), and is ferroan, calcic to calc-alkalic, and peraluminous by the classification diagrams of Frost and Frost (2008). U-Pb zircon analysis yielded an age of 1708.7±6.6 Ma. Unit Xgnsf is separated from unit Xgns where biotite granodiorite is the dominant lithology; the contact is gradational and approximately located. Unit Xgnsf occurs on the west side of Spinney Mountain and as foliation-parallel bodies within the undivided unit Xgns. Rockfall is a hazard on slopes. | 02.21.01 | DMUUnit2 | Xgnsf | Xgnsf | 222-235-222 | None | DAS1 | Metamorphic rock | High | DMU49
50 | w | water | water | Holocene | None | 03 | DMUUnit1 | None | w | 151-219-242 | None | DAS1 | Water or ice | High | DMU50

#### Glossary

OBJECTID | Term | Definition | DefinitionSourceID | Glossary_ID
--- | --- | --- | --- | ---
54 | 2SD | The square root of the average of the squares of deviations about the mean of a set of data. It is a statistical measure of dispersion [stat]. Symbol: σ. Syn: root-mean-square deviation. 2SD indicated the error mesaure was 2 standard deviations | AGI | GLO01
51 | Age | the length of an existence extending from the beginning to any given time | DICT | GLO02
29 | anticline_certain | A fold, generally convex upward, whose core contains the stratigraphically older rocks. Identity and existence certain, location accurate | AGI | GLO03
40 | anticline_concealed2 | A fold, generally convex upward, whose core contains the stratigraphically older rocks. Identity and existence certain, location concealed | AGI | GLO04
30 | Ar-Ar | A variation of the potassium-argon age method in which the sample to be dated is first irradiated with neutrons, converting some potassium-39 to argon-39. Argon is then extracted from the sample (either in one step or incrementally), and its isotopic composition analyzed. The amount of argon-39 is a measure of potassium content, and the ratio of radiogenic argon-40 to argon-39 is a function of age. It is sometimes possible to detect extraneous argon, and to determine whether or not the dated material has been disturbed by later thermal or chemical events (Miller, 1972). | AGI | GLO05
25 | bedding | The orientation of a structural element (plane or line) relative to a horizontal plane. Attitudes of planes are expressed by strike and dip (or dip direction and dip), whereas attitudes of lines are expressed by bearing (or trend, azimuth) and plunge. | AGI | GLO06
1 | certain | Identity 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-013-2006 | GLO07
9 | contact | A plane or irregular surface between two types or ages of rock; examples are faults, intrusive borders, bedding planes separating distinct strata, and unconformities. | AGI | GLO08
47 | Cross Section Line | A line on a map, indicating the position of a profile section. It is the profile line of the section as seen in plan. | AGI | GLO09
23 | dbl sided arrow | Symbol representating the reversal of movement on a fault | DAS1 | GLO10
52 | Deposit | type of matter deposited by a natural process | DICT | GLO11
53 | Dike | A tabular igneous intrusion that cuts across the bedding or foliation of the country rock. Also spelled: dyke. | AGI | GLO12
6 | DMUHeading1 | GeMS hierarchy term | GeMS | GLO13
3 | DMUHeading2 | GeMS hierarchy term | GeMS | GLO14
13 | DMUHeading3 | GeMS hierarchy term | GeMS | GLO15
4 | DMUUnit1 | GeMS hierarchy term | GeMS | GLO16
10 | DMUUnit2 | GeMS hierarchy term | GeMS | GLO17
44 | DZ | Detrital zircon | DAS1 | GLO18
42 | ElevFt | A hatch mark shown on the edges of geologic cross sections to denote the elevation in feet | DAS1 | GLO19
21 | ElevM | A hatch mark shown on the edges of geologic cross sections to denote the elevation in meters | DAS1 | GLO20
34 | estimated bedding | The estimated orientation of a structural element (plane or line) relative to a horizontal plane. Attitudes of planes are expressed by strike and dip (or dip direction and dip), whereas attitudes of lines are expressed by bearing (or trend, azimuth) and plunge. | AGI | GLO21
11 | fault | A fault is a fracture or zone of fractures between two blocks of rock. Faults allow the blocks to move relative to each other; a planar surface of rupture along which geologic units have been fractured and then displaced. Identity and existence certain, location accurate | AGI | GLO22
24 | fault movement | Symbology showing relative fault movement | DAS1 | GLO23
17 | Fault_approximate | A fault is a fracture or zone of fractures between two blocks of rock. Faults allow the blocks to move relative to each other; a planar surface of rupture along which geologic units have been fractured and then displaced. Identity and existence certain, location approximate | AGI | GLO24
18 | Fault_approximate_questionable | A fault is a fracture or zone of fractures between two blocks of rock. Faults allow the blocks to move relative to each other; a planar surface of rupture along which geologic units have been fractured and then displaced. Identity or existence questionable, location approximate | AGI | GLO25
7 | Fault_certain | A fault is a fracture or zone of fractures between two blocks of rock. Faults allow the blocks to move relative to each other; a planar surface of rupture along which geologic units have been fractured and then displaced. Identity and existence certain, location accurate | AGI | GLO26
14 | Fault_concealed | A fault is a fracture or zone of fractures between two blocks of rock. Faults allow the blocks to move relative to each other; a planar surface of rupture along which geologic units have been fractured and then displaced. Identity and existence certain, location concealed | AGI | GLO27
12 | Fault_concealed_questionable | A fault is a fracture or zone of fractures between two blocks of rock. Faults allow the blocks to move relative to each other; a planar surface of rupture along which geologic units have been fractured and then displaced. Identity or existence questionable, location concealed | AGI | GLO28
15 | Fault_inferred | A fault is a fracture or zone of fractures between two blocks of rock. Faults allow the blocks to move relative to each other; a planar surface of rupture along which geologic units have been fractured and then displaced. Identity and existence certain, location inferred | AGI | GLO29
19 | foliation | A general term for a planar arrangement of textural or structural features in any type of rock, esp. the locally planar fabric in a rock defined by a fissility, a preferred orientation of crystal planes in mineral grains, a preferred orientation of inequant grain shapes, or from compositional banding. In igneous rocks, planar parallelism of flaky or tabular minerals and mineral aggregates, slabby xenoliths, or flattened vesicles as well as compositional layering. In metamorphic rocks, planar parallelism of flaky minerals and compositional layering. Adj: foliate . | AGI | GLO30
55 | High | exceeding the common degree or measure; strong; intense; exalted in rank, station, eminence, etc.; of exalted character or quality | DICT | GLO55
41 | Inclined fault | An inclined fault is a fracture or zone of fractures between two blocks of rock in which the fault blocks are sloped or slanting. Faults allow the blocks to move relative to each other; a planar surface of rupture along which geologic units have been fractured and then displaced. | AGI | GLO31
26 | Inclined gneissic layering | A type of foliation in metamorphic rock defined by compositional banding. Typically, gneissic banding consists of alternating dark (mafic) and light (felsic or silicic) bands of rock. Gneissic banding may reflect original compositional layering in the protolith, or lit-par-lit intrusion, or metamorphic differentiation by diffusion, or transposition. | AGI | GLO32
38 | Inclined hinge of minor fold | The locus of maximum curvature or bending in a folded surface, usually a line. On this map, these are minor. | AGI | GLO33
37 | Inclined lineation | A general, nongeneric term for a locally linear structure or fabric in a rock, e.g. flow lines, scratches, striae, slickensides or slickenfibers on a single surface; linear arrangements of components in sediments; or axes of folds. Lineation in metamorphic rocks includes aligned rod-shaped and/or elongate minerals grains, crenulation fold axes, and the lines of intersection between bedding and cleavage or any two sets of oriented surfaces (O'Leary et al., 1976; El-Etr, 1976). | AGI | GLO34
22 | Inclined mineral lineation | A linear fabric element defined by the preferred orientation of inequant mineral grains (e.g. prismatic grains of horneblende) or elongated grain aggregates. | AGI | GLO35
31 | Inclined mylonitic foliation | A fine-grained, foliated rock, commonly with poor fissility and possessing a distinct lineation. Usually found in narrow, planar zones of localized ductile deformation, although kilometer-scale zones exist. Mylonites are often inferred to indicate extensive simple shear, but they may also record pure shear or volume loss or both. Introduced by Lapworth in 1885 and originally thought to have formed by the crushing and milling of minerals, it is now understood to form by one or more of the crystal plastic deformation mechanisms (Holmes, 1920). Cf: blastomylonite; cataclasite; microbreccia; protomylonite; ultramylonite. | AGI | GLO36
27 | Lineation on fault surface | A general, nongeneric term for a locally linear structure or fabric in a rock, e.g. flow lines, scratches, striae, slickensides or slickenfibers on a single surface, in this case on a fault plane | AGI | GLO37
50 | Ma | Mega-annum, one million (106) years. Informal SI notation, where annum is age in years before present, with "present" fixed as 1950. This term has largely replaced the various abbreviations for "millions of years before present" in geological literature. It is not equivalent to the elapsed time interval or duration in "millions of years" (myr). | AGI | GLO38
36 | Mylonitic shear zone | A parallel-sided zone of localized shearing displacement, which may be recognized by sigmoidal mineral-filled veins, locally well-developed cleavage or foliation, wholesale grain-size reduction or mylonitization, or some combination of these features (Ramsay & Graham, 1970). | AGI | GLO39
2 | questionable | Identity 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-013-2006 | GLO40
43 | river feature | Location of river featuire shown in cross section | DAS1 | GLO41
16 | Scarp | (a) A line of cliffs produced by faulting or by erosion. The term is an abbreviated form of escarpment, and the two terms commonly have the same meaning, although "scarp" is more often applied to cliffs formed by faulting. See also: fault scarp; erosion scarp. (b) A relatively straight, clifflike face or slope of considerable linear extent, breaking the general continuity of the land by separating surfaces lying at different levels, as along the margin of a plateau or mesa. A scarp may be of any height but does not describe properly a slope of highly irregular outline. Cf: scarp slope. (c) beach scarp. (d) The headscarp of a landslide. | AGI | GLO42
20 | syncline | A fold of which the core contains the stratigraphically younger rocks; it is generally concave upward. Identity and existence certain, location accurate | AGI | GLO43
49 | syncline_certain | A fold of which the core contains the stratigraphically younger rocks; it is generally concave upward. Identity and existence certain, location accurate | AGI | GLO44
35 | syncline_certain3 | A fold of which the core contains the stratigraphically younger rocks; it is generally concave upward. Identity and existence certain, location accurate | AGI | GLO45
46 | syncline_concealed | A fold of which the core contains the stratigraphically younger rocks; it is generally concave upward. Identity and existence certain, location concealed | AGI | GLO46
28 | syncline_concealed2 | A fold of which the core contains the stratigraphically younger rocks; it is generally concave upward. Identity and existence certain, location concealed | AGI | GLO47
5 | Thrust fault_certain | A fault with a dip of 45° or less over much of its extent, on which the hanging wall has moved upward relative to the footwall. Identity and existence certain, location accurate. Sawteeth on upper (tectonically higher) plate. | AGI | GLO48
8 | Thrust fault_concealed | A fault with a dip of 45° or less over much of its extent, on which the hanging wall has moved upward relative to the footwall. Concelaed indicates that the fault is covered. Identity and existence certain, location concealed. Sawteeth on upper (tectonically higher) plate | AGI | GLO49
48 | U-Pb | Calculation of an age in years for geologic material based on the known radioactive decay rate of uranium-238 to lead-206 and uranium-235 to lead-207. It is part of the more inclusive uranium-thorium-lead age method in which the parent-daughter pairs are considered simultaneously. Syn: lead-uranium age method. | AGI | GLO50
39 | volcanic layering | A succession of tabular units exhibiting distinct variation in mineralogic, textural or structural characteristics within igneous, sedimentary, or metamorphic rocks; or the formation of tabular bodies at different rock type, one upon the other, in a particular rock; e.g. the phenomenon in plutonic rocks resulting from crystal settling in magma. Describes high-temperature sedimentation features of igneous rocks and tabular mineral segregation in metamorphic rocks. Bedding and stratification refer to layering in sedimentary rocks. Cf: rhythmic layering; phase layering. | AGI | GLO51
33 | Xgb dike - certain | A tabular igneous intrusion (Xgb) that cuts across the bedding or foliation of the country rock. Also spelled: dyke. Identity and existence certain, location accurate | AGI | GLO52
32 | YXp dike - approximate | A tabular igneous intrusion (Xgb) that cuts across the bedding or foliation of the country rock. Also spelled: dyke. Identity and existence certain, location approximate | AGI | GLO53
45 | YXp dike - certain | A tabular igneous intrusion (YXp) that cuts across the bedding or foliation of the country rock. Also spelled: dyke. Identity and existence certain, location accurate | AGI | GLO54

#### MiscellaneousMapInformation

OBJECTID | MapProperty | MapPropertyValue | MiscellaneousMapInformation_ID
--- | --- | --- | ---
1 | ACKNOWLEDGMENTS | A 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 Monty Downare and family of Elk Mountain Cattle Company, Justin Osborne and Le Ann Markham (Colorado State Land Board), Richard Marreel, Rogers Mountain Ranch, Darcy Mount (Colorado Parks and Wildlife), Jordan Worrell (Aurora Water), and the Denver Water 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. Vince Matthews and Matt Morgan reviewed the map and accompanying materials, providing many helpful suggestions that substantially improved the final product. | MMI01
2 | REGIONAL SETTING | The Spinney Mountain quadrangle is located at the southeastern end of South Park in central Colorado. It spans the Elkhorn fault system, a major structural feature that forms the western boundary of the Front Range uplift (Ruleman and others, 2011). On the eastern side of the fault, the bedrock at the land surface is mostly Proterozoic metamorphic and intrusive igneous rocks. The South Platte River runs through the quadrangle, roughly along the fault system, and is impounded for two water supply reservoirs (Spinney Mountain and Elevenmile). Numerous surficial deposits are present along the river and its tributaries. The map is also at the north end of the Eocene Thirtynine Mile volcanic field, so it contains numerous and varied volcanic rocks. Volcanic and volcaniclastic rocks form most of the bedrock at the land surface on the western (downthrown) side of the fault system. | MMI02
3 | MAJOR STRUCTURAL FEATURES | Many periods of tectonism have affected the rock formations on this quadrangle, but those that are the most evident today are: 1) the Paleoproterozic Colorado Orogeny, 2) the late Paleozoic ancestral Rocky Mountains Orogeny, 3) the Late Cretaceous to Eocene Laramide Orogeny, 4) Eocene-Oligocene tectonics, and 5) Neogene Rio Grande rifting. Evidence of tectonic activity during all five of these periods exists on the quadrangle, as does evidence of reactivation of several structural features. The most prominent features are as follows: | MMI03
4 | HARTSEL UPLIFT | The Hartsel uplift underlies the quadrangle. Faulting in the uplift has divided the quadrangle into structural blocks that moved independently of each other at various times in geologic history. One set of faults is oriented at approximately N30W. It includes the Pabst-Howe, Rogers, and Elevenmile faults, and the Elkhorn fault system. The other set is oriented at approximately N65E. It includes the Gulch Road, Thunder Ridge, Wiedersphan, and Cross Creek faults. | MMI04
5 | ELKHORN FAULT SYSTEM | The Elkhorn fault system includes the West side, Elkhorn, and East side-Chase Gulch faults, as well as associated unnamed fault strands, the Spinney syncline, and an additional unnamed syncline. It extends about 30 km north of the map area. To the south, it appears to die out (Scott and others, 1978). The down-to-the-west West side fault thrusts Cretaceous rocks over unlithified alluvium. The down-to-the-west Elkhorn fault thrusts Paleoproterozoic rocks over Cretaceous and Paleocene (?) rocks. The down-to-the-east East side-Chase Gulch fault sets Paleoproterozoic rocks against poorly lithified alluvial sediments of likely Neogene age. | MMI05
6 | WEST SIDE THRUST FAULT | The West side thrust fault is about 1200-1500 m long with a trace oriented at about N20W. It is an up-to-the-east fault that offsets Quaternary surficial deposits and exhibits a scarp with an average height of 1.86 m (Heerschap, 2003). Shaffer (1980) considered the possibility that the scarp could have been formed by a landslide or by gravitational spreading, but trenching confirmed that the scarp was formed by fault movement. The fault was trenched in four places (Shaffer, 1980). The average dip of the fault plane was found to be 6 to 43 degrees to the northeast. Vertical displacement of bedrock is 4 to 15 m and net displacement is 15 to 30 m. Net displacement of the surficial deposits is 2.4 m. The last fault movement is thought to have been between 13,000 and 30,000 years ago. Analysis of the scarp morphology (Heerschap, 2003) suggests that the West side fault last moved <15,000 years ago, and possibly <5000 years ago. Shaffer (1980) estimated that a surface rupture of the fault would produce a ground displacement of 5 to 10 cm. | MMI06
7 | ELKHORN THRUST FAULT | The Elkhorn thrust fault is approximately 30 km long. In the map area it trends northwest. It is an up-to-the-east fault with a net displacement inferred to be about 600 to 1200 m. Its major movement is thought to have taken place during the Paleocene Epoch (Sawatsky, 1967; Shaffer, 1980; Ruleman and others, 2011). Two synclines occur on the downthrown side of the fault. The doubly plunging Spinney syncline deforms the South Park Formation. The syncline is deformed and truncated by the Gulch Road fault. A smaller, south-plunging syncline occurs in the Elkhorn conglomerate, adjacent to the Elkhorn fault. Both the South Park Formation and the Elkhorn conglomerate are thought to be Paleocene in age. The synclines formed after the deposition of these sediments. As the Tallahassee Creek Conglomerate is not folded on the west limb of the Spinney syncline, the syncline formed before the deposition of the Tallahassee Creek Conglomerate. | MMI07
8 | EAST SIDE-CHASE GULCH FAULT | The East side-Chase Gulch fault extends about 19 km north from Spinney Mountain. In the map area it trends northwest. Rocky Mountain Energy drilled through the fault plane and found it to dip at a minimum of 50 degrees to the east. Just north of the South Platte River, it is nearly vertical (Shaffer, 1980). To the south, the fault appears to continue along the western shore of Elevenmile Reservoir. At the ground surface and at shallow depths, the fault is down-to-the-east. In NW ¼ NW ¼ sec. 12, T 13 S., R 74 W, Rocky Mountain Energy drilled through nearly 500 m of arkosic sandstone and conglomerate on the downthrown side of the fault (Shaffer, 1980). South of the Gulch Road fault, the gravity gradient across the East side-Chase Gulch fault decreases substantially (Boler and others, 1982), implying a smaller displacement south of the Gulch Road fault. Possibly some of the strain was transferred to the Rogers fault. We follow the interpretation of Shaffer (1980) that the Chase Gulch and East side faults merge at depth with the Elkhorn fault and reactivated the older thrust fault with normal-sense kinematics. We depict this relationship at depth on cross section A-A’, and on cross section B-B’ depict a single east-dipping fault surface that accommodated both reverse- and normal-sense displacement. Portions of the East side-Chase Gulch fault show evidence of possible Quaternary movement. Scarps are visible on the east side of Spinney Mountain. Their average height is 2.26 m (Heerschap, 2003). On the west side of Elevenmile Reservoir, Quaternary alluvium in unit Qasp4 is preserved on the east side of the fault. Differential erosion was considered as a possible cause of the scarps, but was discounted when trenching and cores showed evidence of Late Pleistocene fault movement (Shaffer, 1080). The trenches showed about 9 vertical meters of down-to-the-east Quaternary movement. The last movement is thought to have been between 13,000 and 30,000 years ago. Analysis of fault scarp morphology suggests that the last movement was about 15,000 years ago (Heerschap, 2003). The maximum credible earthquake for the East side-Chase Gulch fault is estimated to be magnitude 6.2, which would cause an estimated displacement of 25 cm (Shaffer, 1980). However, these estimates assume that the East side-Chase Gulch and Elevenmile faults are connected to each other. Evidence for a connection wasn’t found during this mapping project, but this may be due to poor exposure. | MMI08
9 | ROGERS FAULT | The Rogers fault is oriented parallel to the Elkhorn fault system. It is a down-to-the-west fault with at least 240 m of displacement. It offsets the Thirtynine Mile Andesite but not the Tallahassee Creek Conglomerate, indicating that its last movement was in the Eocene Epoch. | MMI09
10 | ELEVENMILE FAULT | The Elevenmile fault is a splay of the Rogers fault. It is 4.8 km long and trends N14W. It is a down-to-the-east fault. A scarp can be seen along the fault that displaces units Qatc4 and Qaf by about 1.8 m. Groundwater ponds west of the fault trace in the valleys of Union and Gilead creeks. The scarp is similar to those of the East side and West side faults, so it is inferred that the last movement also took place 13,000 to 30,000 years ago (Shaffer, 1980). Analysis of the fault scarp morphology showed that the average scarp height is 1.41 m and suggests that the last movement on the fault was >15,000 years ago (Heerschap, 2003). The maximum credible earthquake on the fault is one of magnitude 6.2, and this is predicted to result in a displacement of 25 cm (Shaffer, 1980). As was noted in discussion of the East side-Chase Gulch fault, this is based on the assumption that the Elevenmile fault is connected to the East side-Chase Gulch fault. | MMI10
11 | PABST-HOWE FAULT | The Pabst-Howe fault is also a northwest-trending, down-to-the-west fault that parallels the Elkhorn fault system. On the adjoining Guffey NW quadrangle, approximately 2500 m of displacement (Durrani, 1980) is associated with a prominent gravity gradient (Boler and others, 1982). To the south, it either dies out or is concealed under the Thirtynine Mile Andesite. | MMI11
12 | GULCH ROAD FAULT | The Gulch Road fault is the northernmost in a series of four faults oriented at about N50E to N70E. It extends for a distance of at least 12 km from the Currant Creek fault on the Guffey NW quadrangle to the Elkhorn fault system on the Spinney Mountain quadrangle. It coincides with the southern edges of gravity lows on both the Guffey NW and Spinney Mountain quadrangles (Boler and others, 1982). The Spinney syncline is truncated abruptly at the fault, as is a large syncline on the Guffey NW quadrangle. The earliest and largest movement was down-to-the-north. It occurred after the deposition of the South Park Formation, but before the deposition of the Thirtynine Mile Andesite. A later, down-to-the-south movement occurred to deform the Tallahassee Creek Conglomerate. The Gulch Road fault is a major structure that appears to have compartmentalized strain in the rocks north and south of it. | MMI12
13 | THUNDER RIDGE FAULT | The Thunder Ridge fault is a northeast-trending, questionable fault that may crosscut the Wall Mountain Tuff and continue below the Tallahassee Creek Conglomerate. Its sense of motion is unknown. | MMI13
14 | WIEDERSPHAN FAULT | The Wiedersphan fault is a northeast-trending, down-to-the-south fault that is marked by a line of hydrothermal alteration along the fault trace. It does not appear to crosscut the Tallahassee Creek Conglomerate. Exposure of the Balfour Formation is not adequate to determine whether the fault crosscuts it. The fact that the lower member of the Thirtynine Mile Andesite is preserved only south of it suggests that the last episode of fault movement may have occurred after deposition of the Thirtynine Mile Andesite, but before deposition of the Tallahassee Creek Conglomerate. | MMI14
15 | CROSS CREEK FAULT | The Cross Creek fault is a northeast-trending fault that may have experienced an episode of down-to-the-north movement prior to the deposition of the Wall Mountain Tuff. Alternatively, the tuff on the south side of the fault may have been deposited on an erosional remnant of unit Xgd. After the tuff was deposited, the fault experienced down-to-the-south movement that deformed the tuff on the north side of the fault. Presumably, this occurred before the deposition of the Tallahassee Creek Conglomerate because the conglomerate was not deformed or offset by the fault. | MMI15
16 | STRATIGRAPHY AND STRUCTUAL EVOLUTION | The oldest units in the quadrangle are high-grade Proterozoic gneisses, amphibolite, and granodiorite (units Xbgn, Xgns, and Xa) exposed in the hanging wall of the Elkhorn thrust. A sample collected from unit Xgnsf (sample number SM586) yielded a 207Pb/206Pb zircon age of 1708.7±6.6 Ma. At least three deformation events are recorded by fabrics in unit Xgns; isoclinal folds demonstrate transposition of an early fabric to parallelism with the dominant gneissic foliation that dips steeply to shallowly WSW. This foliation is gently folded around a shallowly NNW-plunging axis. These oldest units are intruded by an extensive porphyritic granodioritic gneiss (unit Xgd). A sample collected from this unit yielded a 207Pb/206Pb zircon age of 1712.9±6.4 Ma. Foliation within unit Xgd is largely N- or NE-dipping with a down-dip lineation. This foliation parallels the foliation within unit Xgns near where unit Xgd intrudes unit Xgns. Foliation in units Xa and Xbgn largely parallels that within unit Xgd. Unit Yg, which intrudes unit Xgd, generally lacks foliation and either intrudes parallel to or cuts oblique to the foliation in unit Xgd. However, sparse observations of a weak foliation defined by aligned biotite grains within unit Yg that parallels the unit Xgd foliation could suggest late synkinematic intrusion. NW- and NNW- striking brittle faults, one with apparent SE-down separation, cut the Proterozoic units exposed on the slopes of Stoll Mountain, though the timing of this faulting is unclear. Jointing in Proterozoic rocks is dominated by subvertical planes ranging from WNW to NNE striking, though other joint orientations are also observed. As groundwater movement in the Proterozoic rocks occurs in joints, the joint orientations are helpful in understanding how movement will occur in areas underlain by these rocks. | MMI16
17 | 2STRATIGRAPHY AND STRUCTUAL EVOLUTION | The widespread distribution of lower and middle Paleozoic sedimentary rocks in central Colorado (Ross and Tweto, 1980) suggests that these rocks were originally deposited on the Spinney Mountain quadrangle but were later eroded. During the late Paleozoic Era, the quadrangle was part of the Frontrangia uplift (Mallory, 1958). If upper Paleozoic sediments were ever deposited in this area, they too were subsequently eroded, likely along with the remaining lower and middle Paleozoic rocks. The Mesozoic Era is thought to have been a time of local tectonic quiescence. In the map area, the Garo (Jg) and Morrison (Jm) formations were deposited during the Jurassic Period, in continental environments. As the Western Interior Seaway encroached on the area, the Dakota Sandstone (Kd), Benton Group (Kb), Niobrara Formation (Kn), and Pierre Shale (Kp) were deposited in marginal marine and marine environments. The Laramide Orogeny began in the latest Mesozoic to earliest Cenozoic era, when the Jurassic and Cretaceous rocks were folded and faulted. Subsequently, during the Paleocene Epoch, the debris flows and alluvium of the South Park Formation (PEsp) and Elkhorn conglomerate (PEec) were deposited with angular unconformity on the Cretaceous rocks. After deposition, these formations were also folded and faulted. The Elkhorn fault system, the Rogers fault, and the Pabst-Howe fault appear to have been active at this time, with down-to-the-west movement. The Gulch Road and Cross Creek faults were also active, with down-to-the-north movement. The next-oldest rock formation preserved on the quadrangle is the Wall Mountain Tuff (PEwm), which was emplaced in the Eocene Epoch as a massive pyroclastic flow. It is preserved at the surface only on the fault block bounded by the Rogers, Gulch Road, and East side/Chase Gulch faults. Following deposition of the Wall Mountain Tuff, the Thirtynine Mile volcanic series was emplaced in the late Eocene Epoch. The oldest formation in the series (the Balfour Formation; PEb) was deposited as volcaniclastic alluvial, debris flow, and lacustrine sediments. This was followed by emplacement of the volcanic breccias and lava flows of the lower member of the Thirtynine Mile Andesite. The lower part of the lower member (PEal) is mostly volcanic breccias with minor unbrecciated flows that issued from a great number of small vents in the map area. The upper part of the lower member (PEalf) has noticeably more and thicker unbrecciated flows. Though most of the lower member is pyroxene andesite porphyry, small areas of rhyodacite porphyry (PEalr), hornblende andesite porphyry (PEalh), and a diorite plug (PEald) were also found. In the latest Eocene Epoch, the Tallahassee Creek Conglomerate (PEtc) was deposited as debris flows and alluvial sediments in paleovalleys that formed after the deposition of the Thirtynine Mile volcanic series. Late in Tallahassee Creek time, a facies consisting almost entirely of Wall Mountain Tuff boulders (PEtcw) was deposited in proximity to the Wall Mountain Tuff outcrops. Though the main pulse of the Laramide Orogeny in this area appears to have been in Paleocene time, a high level of tectonic activity continued throughout the Eocene Epoch. The Wall Mountain Tuff, Thirtynine Mile volcanic series, and Tallahassee Creek Conglomerate are separated from each other by angular unconformities. The north-northwest trending Rogers fault shows evidence of down-to-the-west Eocene movement, which is the same sense of motion that the north-northwest trending faults (Rogers, Pabst-Howe, and Elkhorn system) had during the Paleocene phase of the Laramide Orogeny. However, the northeast-trending Gulch Road, Wiedersphan, and Cross Creek faults show evidence of down-to-the-south Eocene motion. This is the opposite of the sense of motion that occurred on the Gulch Road and Cross Creek faults during the Paleocene phase of the orogeny. These relationships suggest that the Eocene tectonic activity in the map area did not result solely from the continuation of the Laramide stress field. Rather, there was a change in the Eocene stress field that caused movement reversals on the northeast-trending faults. Given the large amount of magmatic activity that occurred beneath the map area during the formation of the Thirtynine Mile Andesite, magma movements could have been one possible contributing factor to the change in the stress field. The only possible Oligocene, Miocene, or Pliocene rocks preserved in the map area are on the downthrown side of the East side-Chase Gulch fault. Their preservation likely resulted from down-to-the-east, late Paleogene to Neogene movements on these faults. This normal fault movement may have been related to the opening of the Rio Grande Rift (Shaffer, 1980). The next available information about the geologic history of the quadrangle comes from Quaternary surficial deposits and possible fault scarps. Inset alluvial terraces remain as evidence of active fluvial systems during the Holocene and Pleistocene. The inset relationship of the terraces indicates a repetitive cycle of deposition and incision by the ancestral South Platte River and its tributaries, leaving older, isolated, gravel-capped surfaces at higher elevations in the landscape. The oldest gravel deposited by ancestral stream systems in the mapped area is unit Qgtc2 (Middle Pleistocene). | MMI17
18 | 3STRATIGRAPHY AND STRUCTUAL EVOLUTION | During the Late Pleistocene and Early Holocene, glacial ice covered higher elevations west of the mapped area. When the Bull Lake and Pinedale glaciations culminated, there was significant water in the drainage networks adjacent to and within the mapped area. Four units record periods of deposition in gravelly alluvium mapped as units Qatc4, Qasp4, Qasp3, and Qacg3. Units Qatc4 and Qasp4 are roughly correlative with the end of the Bull Lake Glaciation which culminated around 120 ka in the Arkansas River valley (Schweinsberg and others, 2020). Lower terraces underlain by units Qasp3 and Qacg3 are roughly correlative with the end of the Pinedale Glaciation, which culminated around 14 to 15 ka (Young and others, 2011; Schweinsberg and others, 2020). During the Middle and Late Holocene, modern drainages deposited unit Qa on low-lying terraces and floodplains adjacent to the South Platte River, Threemile Creek, and Chase Gulch. Throughout the Early Pleistocene and Holocene, rainstorm events deposited units Qaf, Qafo, Qau, and Qsw in the mapped area. Unit Qafo southwest of Eleven Mile Reservoir was likely deposited predominantly during the Late Pleistocene. The unit underlies fan-shaped surfaces that are topographically lower than unit Qatc4, which is interpreted as correlative with the end of the Bull Lake Glaciation. Deposits in the northeast corner are fairly thin, approximately 1.5 m thick. Given how thin the deposits are and their higher relative elevations to nearby drainages compared to deposits southwest of Eleven Mile Reservoir, the unit mapped in the northeast corner is likely older than in the south. It is at least as old as pre-Bull Lake (Middle Pleistocene) and may be as old as Eocene in age (Epis and others, 1979). Unit Qaf is topographically lower than unit Qafo but likely deposited in very similar ways during the Holocene. If the scarps on the West side, Chase Gulch, East side, and Elevenmile faults were formed by fault movement, then that movement occurred after deposition of unit Qaf. Inferred Quaternary movement on the West side fault was down-to-the-west (reverse movement), whereas inferred Quaternary movement on the Chase Gulch, East side, and Elevenmile faults was down-to-the-east (normal movement). This movement may have resulted from continued activity in the Rio Grande Rift (Shaffer, 1980). Wall Mountain Tuff clasts are deposited as unit Qac in an apron-shaped landform below an outcrop near the northwest tip of Eleven Mile Reservoir. Clasts rolled or fell away from the outcrop sporadically during the Pleistocene and Holocene. Landslides initiated near contacts with or within relatively weak bedrock units and have deposited unit Qls during the Pleistocene and Holocene. | MMI18
19 | REFERENCES | Barkmann, P. E., Houck, K. J., Dechesne, M., Lovekin, J. R., and Johnson, E. P., 2017, Geologic map of the Hartsel quadrangle, Park County, Colorado: Colorado Geological Survey Open-file Report 17-04, scale 1:24,000. Barkmann, P.E., Houck, K.J., McGee, Katheryne, and Miggins, D.P., 2018, Geologic map of the Antero Reservoir NE quadrangle, Park County, Colorado: Colorado Geological Survey, OF-18-05, scale 1:24,000. Berry, M.E., Slate, J L ., Paces, J.B., Hanson, P.R ., and Brandt, T.R ., 2015, Geologic map of the Masters 7.5’ quadrangle, Weld and Morgan Counties, Colorado: U .S . Geological Survey Scientific Investigations Map 3344, 10 p. appendix, 1 sheet, 1:24,000 scale. Bohannon, R. G., and Ruleman, C. A., 2009, Geologic map of the Sulphur Mountain quadrangle, Park County, Colorado: U. S. Geological Survey Scientific Investigations Map 3082, scale 1:24,000. Boler, F. M., Klein, D. K., and Kleinkopf, M. D., 1982, Bouguer gravity map of the Pueblo 1x2 degree quadrangle, south-central Colorado: U. S. Geological Survey Miscellaneous Investigations Map I-1419-A, scale 1:250,000. Carpenter, M. B., Keane, C. M., and Cantner, K., 2016, The Geoscience Handbook 2016: Alexandria, Virginia, American Geological Institute. Durrani, J. A., 1980, Seismic investigation of the tectonic and stratigraphic history, eastern South Park, Park County, Colorado: Colorado School of Mines unpublished PhD thesis, 138 p., 40 plates. 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. Epis, R.C., Wobus, R.A., and Scott, G.R., 1979, Geologic map of the Guffey quadrangle, Park County, Colorado: U.S. Geological Survey, Miscellaneous Investigations Series Map I-1180, scale 1:62,500. FEMA Flood Map Service Center, https://msc.fema.gov/portal/home, visited 12/2024. 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. Heerschap, L.K., 2003, Spinney Mountain faults: unpublished report prepared by Colorado Geological Survey for FEMA, 36 p. Houck, K. J., Temple, J., Lindsay, K. O., Barkmann, P. E., and Miggins, D. P., 2025, Geologic map of the Guffey NW quadrangle, Park County, Colorado: Colorado Geological Survey Open-file Report 21-05, scale 1:24,000. Irvine, T.N., and Baragar, W.R.A., 1971, A Guide to the Chemical Classification of the Common Volcanic Rocks: Canadian Journal of Earth Sciences, v. 8, doi:10.1139/e71-055. Kellogg, K.S., Shroba, R.R., Bryant, Bruce, Premo, W.R., 2008, Geologic map of the Denver West 30’ x 60’ quadrangle, North-Central Colorado: U.S. Geological Survey, Scientific Investigations Map 3000, 1:100,000. http://doi.org/10.3133/sim3000 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. Lindsey, K.O., Sawyer, D., and Temple, J., 2018, Geologic map of the Florence quadrangle, Fremont County, Colorado: Colorado Geologic Survey, OF-18-04, scale 1:24,000. Lipman, P. W., and Bachmann, O., 2015, Ignimbrites to batholiths: integrating perspectives from geological, geophysical, and geochronological data: Geosphere, v. 11, no. 3, p. 705-743. Machette, M.N., 1985, Calcic soils of the southwestern United States: Geological Society of America Special Paper no. 203, pp. 1-21. Madole, R.F., 1991, Colorado Piedmont section, in, Wayne, W.J., and others, Quaternary geology of the northern Great Plains, Chap. 15, in Morrison, R.B., ed., Quaternary non-glacial geology: Conterminous U.S.: Geological Society of America, The geology of North America, v. K-2, p. 456-462. 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. Middlemost, E.A.K., 1994, Naming materials in the magma/igneous rock system: Earth Science Reviews, v. 37, doi:10.1016/0012-8252(94)90029-9. 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. 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. Ruleman, C. A., and Bohannon, R. G., 2008, Geologic map of the Elkhorn Quadrangle, Park County, Colorado: U. S. Geological Survey Scientific Investigations Map 3043, scale 1:24,000. Ruleman, C. A., Bohannon, R. G., Bryant, B., Shroba, R. R., and Premo, W. R., 2011, Geologic map of the Bailey 30’x60’ quadrangle, north-central Colorado: U. S. Geological Survey Scientific Investigations Map 3156, scale 1:100,000, booklet, 38 p. Sawatzky , D.L., 1967, Tectonic style along the Elkhorn thrust, eastern South Park and western Front Range, Park County, Colorado: Colorado School of Mines, PhD Dissertation, Golden, Colorado, 172 p. Schweinsberg, A.D., Briner, J.P., Licciardi, J.M., Shroba, R.R., and Leonard, E.M., 2020, Cosmogenic 10Be exposure dating of Bull Lake and Pinedale moraine sequences in the Upper Arkansas River valley, Colorado Rocky Mountain, USA: Quaternary Research, v. 95, pp. 125-139. Scott, G. R., Taylor, R. B., Epis, R. C., and Wobus, R. A., 1978, Geologic map of the Pueblo 1x2 degree quadrangle, south-central Colorado: U. S. Geological Survey Miscellaneous Investigations Map I-1022, scale 1:250,000. Shaffer, M.E., 1980, Seismic hazard evaluation, Spinney Mountain project, Park County, Colorado: unpublished report prepared by Converse Ward Davis Dixon, Inc., Report 78-5129, for R.W. Beck and Associated and the City of Aurora, Colorado, 77 p. 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. Szabo, J.B., 1980, Results and assessment of Uranium-series dating of vertebrate fossils from Quaternary alluvium in Colorado: Arctic and Alpine Research, v. 12, no. 1, p. 95-100 Young, E.N., Briner, J.P., Leonard, E.M., Licciardi, J.M., and Keenan, L., 2011, Assessing climatic and nonclimatic forcing of Pinedale glaciation and deglaciation in the western United States: Geology, v. 39, no. 2, pp. 171-174. | MMI19
20 | STATEMAP AGREEMENT NUMBER | G21AC10708-00 | MMI20
21 | AUTHORS | Karen J. Houck, Skyler Mavor, Kassandra O. Lindsey, Daniel P. Miggins | MMI21
22 | OF NUMBER | 22-07 | MMI22
23 | DOI LINK | https://doi.org/10.58783/cgs.of2207.avzy3933 | MMI23

### 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.
DataSources, nonspatial table, 8 rows
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GeochronPointsAnno, annotation polygon feature class, 4 rows
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GeologicMap_topology, topology
CorrelationOfMapUnits, feature dataset
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CMULines, simple polyline feature class, 55 rows
CMUAnno, annotation polygon feature class, 33 rows
CMUMapUnitPolysAnno, annotation polygon feature class, 40 rows
CrossSectionA, feature dataset
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CSAContactsAndFaults, simple polyline feature class, 37 rows
CSAPoints, simple point feature class, 14 rows
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CSACartoLines, simple polyline feature class, 3 rows
CrossSectionB, feature dataset
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CSBContactsAndFaults, simple polyline feature class, 24 rows
CSBPoints, simple point feature class, 10 rows
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oblique_line, simple polyline feature class, 1 rows