| 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 |
| 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 |
| MapUnit | DescriptionOfMapUnits | CrossSectionA | GeologicMap | CrossSectionC | CrossSectionB | CorrelationOfMapUnits |
|---|---|---|---|---|---|---|
| Xhp | X | -- | X | -- | -- | X |
| Ygsm | X | -- | X | -- | X | X |
| Ygb | X | -- | X | -- | -- | X |
| Xbsg | X | -- | X | -- | -- | X |
| Qa | X | -- | X | -- | -- | X |
| Qtp/Qls | X | -- | X | -- | -- | X |
| PEqm | X | -- | X | X | -- | X |
| Yg | X | X | X | X | X | X |
| Xqt | X | -- | X | -- | -- | X |
| YXp | X | -- | X | -- | -- | X |
| Xb | X | X | X | -- | -- | X |
| Xh | X | X | X | -- | -- | X |
| Xag-1 | X | X | X | -- | -- | X |
| Xag-2 | X | -- | X | -- | -- | X |
| Ygmp | X | -- | X | -- | -- | X |
| Qrg | X | -- | X | -- | -- | X |
| water | X | -- | X | -- | -- | -- |
| Qac | X | -- | X | -- | -- | X |
| Qtp | X | -- | X | -- | -- | X |
| Qls | X | -- | X | -- | -- | X |
| Qtal | X | -- | X | -- | -- | X |
| Xsb | X | X | X | X | X | X |
| Qf | X | -- | X | -- | -- | X |
| OBJECTID | Source | Notes | URL | DataSources_ID |
|---|---|---|---|---|
| 4 | Boise State University | None | https://www.boisestate.edu/earth-isotope/ | BOISE |
| 2 | Colorado School of Mines | Zhaoshan Chang's lab | https://geology.mines.edu/laboratories/la-icp-ms-laboratory/ | CSM |
| 5 | this study | None | None | DAS1 |
| 6 | Dictionary | None | www.dictionary.com | DICT1 |
| 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 |
| 8 | GeMS standard | None | https://ngmdb.usgs.gov/Info/standards/GeMS/ | GEMS1 |
| 7 | Geologic dictionary | None | https://glossary.americangeosciences.org/ | GEODICT1 |
| 3 | US Geological Survey | Chris Holm Denoma's lab | https://www.usgs.gov/media/images/plasma-laboratory | USGS |
| OBJECTID | MapUnit | Name | FullName | Age | Description | HierarchyKey | ParagraphStyle | Label | Symbol | AreaFillRGB | AreaFillPatternDescription | DescriptionSourceID | GeoMaterial | GeoMaterialConfidence | DescriptionOfMapUnits_ID |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 13 | None | SURFICIAL DEPOSITS | SURFICIAL DEPOSITS | None | None | 01 | DMU-Heading1 | None | None | None | None | DAS1 | None | None | DMU01 |
| 1 | None | ALLUVIAL AND COLLUVIAL DEPOSITS | ALLUVIAL AND COLLUVIAL DEPOSITS | None | None | 01-01 | DMU-Heading2 | None | None | None | None | DAS1 | None | None | DMU02 |
| 2 | Qtal | Talus deposits | Talus deposits | Holocene | Poorly sorted, angular to subangular cobbles and boulders along the sides of steep slopes and cliffs in fans and aprons. Thickness is approximately 2–15 m. | 01-01-01 | DMU Unit 1 | Qtal | Qtal | 255-255-190 | 0-0-0 ESRI 24k Geology 605 Breccia | DAS1 | Debris flows, landslides, and other localized mass-movement sediment | High | DMU03 |
| 3 | Qa | Alluvium | Alluvium | Holocene to Pleistocene | Interbedded clay, silt, sand, gravel, and cobbles along streams and washes. Locally contains organic-rich sediments from meadows, marshes, and beaver ponds. Estimated thickness is 1–5 m. | 01-01-02 | DMU Unit 1 | Qa | Qa | 255-255-215 | None | DAS1 | Alluvial sediment | High | DMU04 |
| 32 | Qf | Fan deposits | Fan deposits | Holocene and uppermost Pleistocene | Lobate, hummocky fan-shaped deposits at base of slope to the southwest of Montezuma town site. Unit consists of poorly to moderately sorted, weakly to moderately stratified, granule to boulder gravel with a clayey sandy silt matrix. Surface morphology is characterized by channels and levees produced by debris flows. Deposits laterally thin as individual flow events spread across adjacent surfaces. Deposits delineate general locations of debris flow hazards to structures, roads, and other infrastructure. Thickness approximately 0.5-5 m. | 01-01-03 | DMU Unit 1 | Qf | Qf | 230-230-53 | None | DAS1 | Debris flows, landslides, and other localized mass-movement sediment | High | DMU05 |
| 31 | Qac | Alluvium and colluvium | Alluvium and colluvium | Holocene to upper Middle Pleistocene | Undifferentiated, unconsolidated, non- to weakly stratified, poorly to moderately sorted, sandy, silty, clayey, angular to subrounded, granule- to boulder-gravel deposits that mantle abandoned erosional surfaces, fill local depressions, and form a thin slope veneer downslope from bedrock outcrops. Primarily transported and deposited by most recent slopewash and other local gravitational-driven processes, but includes older diamicton glacial erratics and periglacial solifluction/ice-wedging deposits on the west side of the quadrangle. Estimated thickness 2-15 m. | 01-01-04 | DMU Unit 1 | Qac | Qac | 255-230-203 | 115-223-255 24k Geology ESRI 612 | DAS1 | Colluvium and other widespread mass-movement sediment | High | DMU06 |
| 6 | None | MASS-WASTING DEPOSITS | MASS-WASTING DEPOSITS | None | None | 01-02 | DMU-Heading2 | None | None | None | None | DAS1 | None | None | DMU07 |
| 7 | Qrg | Rock-glacier deposits | Rock-glacier deposits | Holocene and uppermost Pleistocene | Lobate and tongue-shaped deposits consisting primarily of cobbles to boulders with steep flanks and fronts. Deposits interpreted as active by creep and other down-slope, gravity-driven processes. Estimated thickness is 2–30 m. | 01-02-01 | DMU Unit 1 | Qrg | Qrg | 207-194-160 | 0-0-0 ESRI 24k Geology 602 Gravel open | DAS1 | Debris flows, landslides, and other localized mass-movement sediment | Medium | DMU08 |
| 8 | Qls | Landslide deposits | Landslide deposits | Holocene to Upper Pleistocene | Unsorted and unstratified rock debris and sediments, with hummocky topography, headwall scarps, and lobate toes. Locally includes rockfall deposits. Thickness is estimated at 5–50 m. | 01-02-02 | DMU Unit 1 | Qls | Qls | 255-223-79 | None | DAS1 | Debris flows, landslides, and other localized mass-movement sediment | High | DMU09 |
| 33 | Qtp/Qls | Till of Pinedale age reworked into landslide deposits | Till of Pinedale age reworked into landslide deposits | Holocene and Upper Pleistocene | Unsorted, subangular to subrounded, granule to boulder debris with little to no stratification, in a clayey, sandy, silt matrix. Deposits are located in the south-central margin of the quadrangle within a southeast-facing drainage covered by ice during the Pinedale glacial maximum. Postglacial gravitationally driven processes have remobilized till into younger landslide deposits. An apparent lobate remnant of a latest Pleistocene recessional moraine is within the drainage. Thickness approximately 1-5 m. | 01-02-03 | None | Qtp/Qls | Qtp/Qls | 255-223-79 | 115-223-255 24k Geology ESRI 612 | DAS1 | Debris flows, landslides, and other localized mass-movement sediment | High | DMU10 |
| 9 | None | GLACIAL DEPOSITS | GLACIAL DEPOSITS | None | None | 01-03 | DMU-Heading2 | None | None | None | None | DAS1 | None | None | DMU11 |
| 10 | Qtp | Till of Pinedale glaciation | Till of Pinedale glaciation | Upper Pleistocene | Rounded to subrounded, unsorted boulder- to gravel-sized clasts in a sandy-silty matrix. Original glacial landforms, including lateral and terminal moraines, are well preserved, and commonly contain undrained kettles and depressions. Thickness is about 2–30 m. | 01-03-01 | DMU Unit 1 | Qtp | Qtp | 233-202-160 | None | DAS1 | Glacial till | High | DMU12 |
| 11 | None | CENOZOIC INTRUSIVE ROCKS | CENOZOIC INTRUSIVE ROCKS | None | None | 01-04 | DMU-Heading2 | None | None | None | None | DAS1 | None | None | DMU13 |
| 12 | PEqm | Quartz monzonite porphyry | Quartz monzonite porphyry | Eocene | White to light gray, medium- to coarse-grained, porphyritic quartz monzonite with up to 3-cm long blocky to tabular phenocrysts of orthoclase, quartz, and plagioclase. Lesser constituents include biotite, muscovite, hornblende, magnetite, and titanite. Unit makes up the main body of the Montezuma stock, located in the northern half of the Montezuma quadrangle, with dikes exposed throughout the quadrangle. In the southern half of the quadrangle, outcrops of the map unit are rare, and locations are determined primarily by float mapping. The main stock is massive, with two orthogonal joint sets, dipping steeply NW and shallowly S-SE, and a less well-defined set dipping steeply NW and SE. Dikes and sills, weathered rust-orange and extending from a main outcrop of the stock, commonly have a hypabyssal texture, with a very fine-grained light-gray matrix and phenocrysts of quartz and feldspar. U-Pb zircon age yields 38.8 ± 0.5 Ma (Rosera and others, 2021). | 01-04-01 | DMU Unit 1 | PEqm | :qm | 229-148-114 | None | DAS1 | Intrusive igneous rock | High | DMU14 |
| 14 | None | BEDROCK GEOLOGY | BEDROCK GEOLOGY | None | None | 02 | DMU-Heading1 | None | None | None | None | DAS1 | None | None | DMU15 |
| 27 | None | PROTEROZOIC INTRUSIVE ROCKS | PROTEROZOIC INTRUSIVE ROCKS | None | None | 02-01 | DMU-Heading2 | None | None | None | None | DAS1 | None | None | DMU16 |
| 15 | Ygb | Biotite granite | Biotite granite | Mesoproterozoic | Medium- to dark-gray, medium-grained, weakly to moderately foliated granite composed of feldspar (58%), quartz (30%), biotite (10%) and muscovite (2%). White feldspar phenocrysts are up to 2 cm in length. Feldspar in this unit was interpreted in the field to be predominantly plagioclase based on color and habit. The unit is rarely observed in the mapping area and is potentially correlative with a phase of the Granite (Yg). It is separated based on differences in grain size, color, and mineralogy, particularly the interpreted higher proportion of plagioclase feldspar compared to microcline. | 02-01-01 | DMU Unit 1 | Ygb | Ygb | 240-150-180 | None | DAS1 | Intrusive igneous rock | High | DMU17 |
| 28 | Ygsm | Mixed biotite-quartz gneiss and schist with Silver Plume granite | Mixed biotite-quartz gneiss and schist with Silver Plume granite | Mesoproterozoic | Light gray to pink K-feldspar porphyritic granite (Yg) with abundant xenoliths of gray to dark gray biotite-quartz gneiss containing plagioclase (50%), quartz (25%), biotite (15%), and potassium feldspar (10%). Variable amounts of amphibolite (up to 10%) are locally present in the xenoliths. Lithology changes at the meter or smaller scale. May represent an intrusive contact or a margin where metamorphic xenoliths are incorporated into the granite. The granite observed in this unit is interpreted to possibly represent a phase of the Silver Plume Granite. | 02-01-02 | DMU Unit 1 | Ygsm | Ygsm | 251-178-104 | None | DAS1 | Schist and gneiss, of sedimentary-rock origin | Medium | DMU18 |
| 16 | Yg | Granite | Granite | Mesoproterozoic | Light gray to salmon pink equigranular to porphyritic two mica granite composed of microcline (50%), quartz (25%), plagioclase feldspar (15%), biotite (5%), muscovite (3%), and minor magnetite (2%). The unit is weakly to moderately foliated, with magmatic foliation along its contacts, as well as a NW-dipping tectonic foliation within the granite, formed by tightly packed 1-4 cm long feldspar phenocrysts. Joints are generally randomly oriented at the meter-scale throughout the intrusion. Lovering (1935) interpreted this granite as a satellite pluton of the nearby Silver Plume Granite, an extensive, porphyritic Mesoproterozoic two-mica granite with a reported U-Pb zircon age of 1424 ± 6 Ma (du Bray and others, 2018). This unit forms extensive cohesive exposures throughout the eastern half of the Montezuma quadrangle, with smaller pods and dikes throughout the northern half of the quadrangle. | 02-01-03 | DMU Unit 1 | Yg | Yg | 251-212-205 | 255-255-255 ESRI 24k Geology 725 Massive igneous rock | DAS1 | Intrusive igneous rock | High | DMU19 |
| 17 | Ygmp | Megacrystic K-feldspar granite | Megacrystic K-feldspar granite | Mesoproterozoic | Pink to light gray, medium- to coarse-grained porphyritic granite with up to 60% K-spar, up to 35% plagioclase (white) feldspar, 20-30% quartz, biotite (5-20%) and locally minor hornblende. Mineral compositions vary locally. Contains phenocrysts up to 3 cm in length composed of up to 95% potassium (pink) feldspar. May represent a phase of the 1442 ± 2 Ma (Aleinikoff and others, 1993) Mount Blue Sky batholith. | 02-01-04 | DMU Unit 1 | Ygmp | Ygmp | 213-125-179 | None | DAS1 | Coarse-grained intrusive igneous rock | High | DMU20 |
| 18 | YXp | Older pegmatite | Older pegmatite | Mesoproterozoic to Paleoproterozoic (?) | Undifferentiated pegmatite pods and dikes in Paleoproterozoic host rock. Pegmatite is coarse- to very coarse-grained, white to pink, and contains feldspar (65%), quartz (25%), muscovite up to 5% and (or) biotite up to 5%, and minor opaques such as magnetite and pyrite (1%). Thin veinlets of biotite within larger quartz and feldspar grains and along fractures are common in thin section. This unit is generally weakly to moderately foliated and dikes and pods commonly parallel local folds in the metamorphic host rocks. | 02-01-05 | DMU Unit 1 | YXp | YXp | 251-212-205 | 156-156-156 ESRI 24k Geology 721 Massive igneous rocks | DAS1 | Coarse-grained intrusive igneous rock | High | DMU21 |
| 19 | Xag-2 | Altered felsic gneiss 2 | Altered felsic gneiss 2 | Paleoproterozoic (?) | Brown, weather resistant, moderately to strongly foliated, altered felsic gneiss layer containing quartz (40%), feldspar (50%), muscovite (5%), biotite (3%), and minor chlorite. This unit contains local quartzite in discontinuous lenses and thin layers. Does not effervesce in acid. In outcrop, the unit resembles calc-silicate gneiss. Gradational contacts are observed with units Xsb and Xh. | 02-01-06 | DMU Unit 1 | Xag-2 | Xag-2 | 243-137-144 | None | DAS1 | Intrusive igneous rock | Low | DMU22 |
| 20 | Xag-1 | Altered felsic gneiss 1 | Altered felsic gneiss 1 | Paleoproterozoic (?) | Greenish, weather resistant, weakly to moderately foliated, altered felsic gneiss layer containing quartz (24%), feldspar (67%), muscovite (6%) calcite (1%), and chlorite (1%). This unit contains local biotite and rutile. Calcite occurs partly in micrometer-scale veins. Contains local quartzite, commonly as lenses or pods. Effervesces in acid. In outcrop, the unit resembles calc-silicate gneiss. Contacts with units Xsb and Xh are gradational. | 02-01-07 | DMU Unit 1 | Xag-1 | Xag-1 | 251-212-205 | None | DAS1 | Intrusive igneous rock | Low | DMU23 |
| 21 | None | PROTEROZOIC METAMORPHIC ROCKS | PROTEROZOIC METAMORPHIC ROCKS | None | None | 02-02 | DMU-Heading2 | None | None | None | None | DAS1 | None | None | DMU24 |
| 22 | Xhp | Hornblende-plagioclase gneiss | Hornblende-plagioclase gneiss | Paleoproterozoic (?) | Gray to dark-gray, well-foliated, fine-grained gneiss composed of variable amounts of hornblende and plagioclase. Biotite and quartz are common, with significant local variations in composition. The unit is commonly migmatitic and locally deformed. Schistose layers contain a higher percentage of biotite and quartz. The unit is exposed only in the northeast corner of the quadrangle. | 02-02-01 | DMU Unit 1 | Xhp | Xhp | 208-208-189 | None | DAS1 | Metaigneous rock | Medium | DMU25 |
| 23 | Xh | Hornblende gneiss and amphibolite | Hornblende gneiss and amphibolite | Paleoproterozoic (?) | Well-foliated gray to dark gray equigranular fine- to medium-grained gneiss composed of hornblende (typically ~50%, but variable), K-feldspar (25%), plagioclase (~10%), quartz (~10%), and minor garnet, clinopyroxene, and biotite (~5% combined). This unit contains local amphibolite with up to 80% hornblende. Segregated layers of aligned grains of hornblende and of feldspar and quartz can be distinguished in thin section. Forms a gradational contact with both altered felsic gneiss units (Xag-1 and Xag-2). Previously described as the Swandyke Hornblende Gneiss of Lovering (1935). | 02-02-02 | DMU Unit 1 | Xh | Xh | 208-208-148 | None | DAS1 | Meta-mafic rock | Medium | DMU26 |
| 24 | Xbsg | Biotite-sillimanite gneiss | Biotite-sillimanite gneiss | Paleoproterozoic (?) | Gray to black gneiss composed of quartz (50%), biotite (20-30%), feldspar (5%), muscovite (5%), and up to 10% sillimanite locally. Characterized by whitish, elongate sillimanite fibrous grains ranging from 0.5 mm to 3 cm in length. Locally has interbedded Xb and Xsb units. | 02-02-03 | DMU Unit 1 | Xbsg | Xbsg | 139-133-122 | None | DAS1 | Schist and gneiss, of sedimentary-rock origin | High | DMU27 |
| 30 | Xqt | Quartzite | Quartzite | Paleoproterozoic (?) | Well-sorted, fine-grained white to gray arenitic quartzite, with primarily quartz, and minor feldspar, magnetite, pyrite, apatite, and zircon. Occurs as lenses or pods in unit Xag-1 and Xag-2, but contacts are not observed. The estimated thickness of the quartzite is 5 – 10 m. Layering resembles cross-bedding. Its maximum depositional age is ~1.77 Ga (Plate 2). | 02-02-04 | DMU Unit 1 | Xqt | Xqt | None | None | DAS1 | Quartzite | High | DMU28 |
| 25 | Xb | Biotite-gneiss and schist | Biotite-gneiss and schist | Paleoproterozoic (?) | Gray to dark gray rock containing plagioclase (50%), quartz (25%), biotite (15%), potassium feldspar (10%), and locally variable amounts of amphibole (likely hornblende) up to 10%. Unit is locally migmatitic and folded. Local pegmatites are parallel to foliation. | 02-02-05 | DMU Unit 1 | Xb | Xb | 179-153-153 | None | DAS1 | Schist and gneiss, of sedimentary-rock origin | High | DMU29 |
| 26 | Xsb | Interlayered biotite-sillimanite gneiss and schist, biotite-quartz gneiss and schist, and pegmatite | Interlayered biotite-sillimanite gneiss and schist, biotite-quartz gneiss and schist, and pegmatite | Paleoproterozoic (?) | Generally heterogeneous light gray to black interbedded fine- to medium-grained metasedimentary gneisses and schists with highly variable amounts of quartz, plagioclase, microcline, muscovite, and local garnet. Sillimanite-rich areas (up to 10%) are characterized by abundant whitish elongate sillimanite fibrolite aggregates ranging from 0.5 mm to 5 cm in length and are accompanied with higher concentrations of biotite (up to 40% locally). Zircon (<1%) is observed in thin section as inclusions within other mineral grains, particularly in quartz and biotite. Locally, the unit contains interlayered occurrences of units Xag-1, Xag-2, Xb, and Xbsg that are too small to map individually. This unit is locally folded and migmatitic. This unit was previously described as Idaho Springs Formation of Lovering (1935). | 02-02-06 | DMU Unit 1 | Xsb | Xsb | 204-235-153 | None | DAS1 | Schist and gneiss, of sedimentary-rock origin | High | DMU30 |
| 29 | water | water | water | None | None | 03 | DMU-Heading1 | None | water | 190-232-255 | None | DAS1 | Water or ice | High | DMU31 |
| OBJECTID | Term | Definition | DefinitionSourceID | Glossary_ID |
|---|---|---|---|---|
| 19 | 2SD | A statistic used as a measure of the dispersion or variation in a distribution or set of data, equal to the square root of the arithmetic mean of the squares of the deviations from the arithmetic mean. 2SD = 2 standard deviations. | DICT1 | GLO01 |
| 23 | A-A' | notation for cross section A-A' | DAS1 | GLO02 |
| 37 | Age Brackets | Age groupings in the CMU | DAS1 | GLO03 |
| 12 | antiform | A fold in rock strata with a convex upward shape. The rocks in the core of an antiform are the oldest. | GEODICT1 | GLO04 |
| 24 | B-B' | notation for cross section B-B' | DAS1 | GLO05 |
| 9 | border | The edge or boundary of something, or the part near it | DICT1 | GLO06 |
| 8 | boundary | A line that marks the limits of an area | DICT1 | GLO07 |
| 25 | C-C' | notation for cross section C-C' | DAS1 | GLO08 |
| 34 | carto lines | Non-geographic features used to add context or details | DAS1 | GLO09 |
| 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 | GLO10 |
| 4 | contact | A geological contact is a boundary which separates | GEODICT1 | GLO11 |
| 21 | Deposit Type | Groupings for surficial units in the CMU | DAS1 | GLO12 |
| 6 | DMU-Heading1 | GeMS hierarchy formatting term | GEMS1 | GLO13 |
| 7 | DMU-Heading2 | GeMS hierarchy formatting term | GEMS1 | GLO14 |
| 5 | DMU Unit 1 | GeMS hierarchy formatting term | GEMS1 | GLO15 |
| 13 | elev tick | A hatch mark shown on the edges of geologic cross sections to denote the elevation | DAS1 | GLO16 |
| 3 | 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. | GEODICT1 | GLO17 |
| 11 | fold | A curve or bend of a planar structure such as rock strata, bedding planes, foliation, or cleavage. A fold is usually a product of deformation, although its definition is descriptive and not genetic and may include primary structures. | GEODICT1 | GLO18 |
| 35 | Fold_Hinge | Inclined symmetric minor fold hinge showing bearing and plunge | FGDC-STD-013-2006 | GLO19 |
| 36 | Fold_Hinge_Small | Inclined fold hinge of generic (type or orientation unspecified) small, minor fold showing bearing and plunge | FGDC-STD-013-2006 | GLO20 |
| 33 | foliation | The planar or layered characteristics of metamorphic rocks that are evidence of the pressures and/or temperatures to which the rock was exposed. These can be structural such as cleavage, textural such as mineral grain flattening or elongation, or compositional such as mineral segregation banding. | GEODICT1 | GLO21 |
| 38 | High | unusual or considerable in degree, power, intensity, etc. | DICT1 | GLO22 |
| 18 | joint | A planar fracture in rock along which there has been no displacement. Most rock units exposed at Earth's surface have sets of near-vertical, parallel joints that formed in response to unloading or tectonic activity. | GEODICT1 | GLO23 |
| 14 | LA-ICP-MS | LA-ICP-MS (Laser Ablation Inductively Coupled Plasma Mass Spectrometry) is a powerful analytical technology that enables highly sensitive elemental and isotopic analysis to be performed directly on solid samples. LA-ICP-MS begins with a laser beam focused on the sample surface to generate fine particles – a process known as Laser Ablation. The ablated particles are then transported to the secondary excitation source of the ICP-MS instrument for digestion and ionization of the sampled mass. The excited ions in the plasma torch are subsequently introduced to a mass spectrometer detector for both elemental and isotopic analysis. | GEODICT1 | GLO24 |
| 22 | 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). | GEODICT1 | GLO25 |
| 40 | Low | of lesser degree, size, or amount than average or ordinary | DICT1 | GLO26 |
| 17 | Ma | mega annum or millions of years | GEODICT1 | GLO27 |
| 39 | Medium | something intermediate in nature or degree | DICT1 | GLO28 |
| 29 | plunging antiform | A fold in rock strata with a convex upward shape of which the hinge line is inclined to the horizontal. The rocks in the core of an antiform are the oldest. Arrow shows direction of plunge. | GEODICT1 | GLO29 |
| 26 | plunging synform | A trough-shaped fold with youngest strata in the center of which the hinge line is inclined to the horizontal. Arrow shows direction of plunge. | GEODICT1 | GLO30 |
| 28 | river | water channel features encountered along the line of section | DAS1 | GLO31 |
| 20 | synform | A trough-shaped fold with youngest strata in the center. | GEODICT1 | GLO32 |
| 15 | trail | a marked or established path or route | DICT1 | GLO33 |
| 27 | U-Pb detrital zircon | radiometric dating technique | GEODICT1 | GLO34 |
| 30 | U-Pb zircon | radiometric dating technique | GEODICT1 | GLO35 |
| 10 | water | a colorless, transparent, odorless liquid that forms the seas, lakes, rivers, and rain and is the basis of the fluids of living organisms. | DICT1 | GLO36 |
| OBJECTID | MapProperty | MapPropertyValue | MiscellaneousMapInformation_ID |
|---|---|---|---|
| 1 | GeologicSetting | The Montezuma 7.5’ quadrangle lies within Clear Creek, Park, and Summit counties in Colorado, and is located approximately 70 km WSW of Denver. Proterozoic metamorphic and igneous bedrock underlies most of the quadrangle, with younger surficial deposits such as glacial till and alluvium overlying bedrock, primarily in the valleys. The Montezuma quadrangle was previously mapped at a 1:62,500 scale by Lovering (1935) and was included in the 1:100,000 scale map of the Denver West 30' by 60' quadrangle (Kellogg and others, 2008).
The basement rocks in the Montezuma 7.5’ quadrangle are primarily composed of Paleoproterozoic metasedimentary and metaigneous rocks. The main lithologies include biotite-quartz gneiss, sillimanite-biotite gneiss/schist, and interlayered biotite-quartz gneiss/schist with pegmatites. These units have previously collectively been referred to as the Idaho Springs Formation of Lovering (1935). Hornblende gneiss is also exposed in the quadrangle. These metamorphosed units were intruded by Mesoproterozoic igneous rocks. Two main Mesoproterozoic granitoid intrusions are exposed in the Montezuma 7.5’ quadrangle. The ~1442 Ma (Aleinikoff and others, 1993; Powell and others, 2022) megacrystic K-feldspar granite of the Mount Blue Sky (formerly Mount Evans) batholith (map unit Ygmp) is exposed in the southeastern corner of the quadrangle. The ~1424 Ma (du Bray and others, 2018) Silver Plume batholith (Yg) is exposed in the eastern and central parts of the quadrangle. The ~38.8 Ma (Rosera and others, 2021; this study) quartz monzonite of the Montezuma stock (P | MMI1 |
| 2 | U-PB-LA-ICPMSGeochron | Five igneous rock samples were collected for U-Pb zircon geochronology to constrain ages of deformation (samples AB-394, EB-C-2, EB-SRC-1, and EB-MG-1) and to analyze inherited zircon to investigate basement below the exposed surface rock (sample EB-MS-1). Two metasedimentary rock samples were collected for U-Pb detrital zircon analysis to constrain their maximum depositional ages and provenance (samples AB-499 and Q623). Four samples of metasedimentary rock were collected for in-situ monazite analysis to constrain deformational and depositional ages (samples 243PL, 269XAP, 397XFL, and 626XFL). These samples were analyzed using laser ablation inductively coupled mass spectrometry (LA-ICP-MS) methods (Shockley, 2021; Bora, 2024; Borsook, 2025). Results are summarized in Table 1 and Figures 2–5.
Sample AB-499 was collected from a was selected from a more quartzo-feldspathic part of the sillimanite-bearing biotite schist (map unit Xsb) in the northwestern part of the quadrangle. The purpose was to constrain its maximum depositional age, and ages of deformation and metamorphism. This sample yielded five different age populations: ~2.68 Ga, ~2.57 Ga, ~2.01-1.80 Ga, ~1.77 Ga, and ~1.73 Ga (Fig. 2A-C; Borsook, 2025). Weighted means of 207Pb/206Pb ages of these populations are indicated in Figure 2C. The youngest population of nine zircon grains weighted mean 207Pb/206Pb age of 1729 ± 15 Ma, interpreted as the maximum depositional age. Quartzite sample Q623 was collected from the Snake River Cirque to determine its maximum depositional age, age of metamorphism, and to constrain the age of the F2 folds that deformed the quartzite and adjacent units. The sample yielded two small ~2.57 Ga and ~1.90 Ga populations and a large ~1.77 Ga population, with weighted means of 207Pb/206Pb ages as indicated in Figure 2F. The maximum depositional age is that of the 1768.6 ± 8.2 Ma population (MSWD = 0.73; n=82; Fig. 2C), or possibly as young as the 1713 ± 21 Ma weighted mean of 207Pb/206Pb ages of the 15 youngest analyses (MSWD = 0.33). Based on the two samples, deformation and metamorphism was younger than ~1.73 Ga.
Sample AB-394 was collected from a folded pegmatite (Plate 1; map unit YXp) in the northern half of the Montezuma quadrangle to constrain the age of D2 deformation (Borsook, 2025). While nearly all data are discordant (Fig. 3A), four populations can be distinguished based on discordia chords though data (Fig. 3A) and on clusters on the float bar chart (Fig. 3B). They are ~1.93 Ga, ~1.71 Ga, ~1.60 Ga and ~1.42 Ga (Fig. 3A, B; Borsook, 2025). The two younger populations cannot be explained by lead loss from the ~1.7 Ga or older zircon and may be indicative of one or two Mesoproterozoic events. Sample EB-SRC-1 was collected from a folded granite within biotite-quartz gneiss (Plate 1; map unit Xb) in the southern half of the Montezuma quadrangle to constrain the age of F2 folding in the region (Bora, 2024). A discordia chord through 35 discordant zircons yields an upper intercept of 1669 ± 18 Ma (MSWD = 17; Fig. 3C; Bora, 2024). Sample EB-C-2 was collected from a folded pegmatite (Plate 1; map unit YXp within Xb) to constrain the age of F3 folding (Bora, 2024). This sample contains discordant data only, as a result of significant lead loss and common lead. A discordia chord through the six youngest 207Pb/206Pb ages yielded an upper intercept age of 1994 ± 100 Ma (MSWD = 33; Fig. 2B; Bora, 2024). The youngest single grain 207Pb/206Pb age from the sample is 1770 ± 23 Ma (Bora, 2024). No solid conclusions can be drawn based on these samples because of discordancy due to substantial Pb loss and/or common Pb (Fig. 3A; Bora 2024; Borsook, 2025). The data are consistent with constraints from other samples (see above and below) suggesting that F2 and F3 folding occurred after ~1.7 Ga, and that a Mesoproterozoic event affected the area.
Sample EB-MG-1 was collected from a large exposure of a K-feldspar phenocrystic granite (Plate 1; map unit Ygmp) immediately east of the southeastern corner of the Montezuma quadrangle. The crystallization age, based on the weighted mean of 207Pb/206Pb ages of the 34 concordant data with the most consistent data is 1441.0 ± 8.5 Ma (Fig. 4A, B; Bora, 2024). This is consistent with previously published ages of the Mount Blue Sky batholith (Aleinikoff and others, 1993; Powell and others, 2022) and therefore this granite was included in unit Ygmp (Powell and others, 2022). Sample EB-MS-1 was collected from the main body of the Montezuma Stock (Plate 1; map unit P | MMI2 |
| 3 | Resources1 | Several historic metal mining districts exist within the Montezuma quadrangle. The largest of these is the Montezuma Mining District, while the Hall Valley, Peru Creek, Geneva Creek, Snake River, Chihuahua, and the southwestern portion of the Peru-Argentine districts occupy the smaller mining districts in the quadrangle. The Montezuma Mining District is composed of two major vein systems. The intrusion of the ~38.8 Ma Montezuma stock in the northern half of the quadrangle is responsible for the formation of Cordilleran-style veins, which are indicative of a subepithermal setting about a central hydrothermal source and are temporally and spatially related to felsic igneous centers (Pyanoe, 2015). Many of these veins crosscut the Montezuma stock. Expressions of these veins and the mineralized rock at the surface are characterized by limonite and vuggy quartz, indicative of oxidation under supergene conditions (Botinelly, 1979; Pyanoe, 2015; Shockley, 2021). Most of the economic value was contained in silver, with copper, gold, and lead present in minor amounts. Gold in the Peru Creek Mining District occurs in polymetallic veins of sphalerite-galena-pyrite-chalcopyrite + silver minerals (Burnell, 2015). The Peru and Geneva Creek districts have previously been grouped within the larger Montezuma Mining District (Vanderwilt, 1947; Burnell, 2015). More information on these mining districts can be found in Lovering (1935), Lovering and Goddard (1950), and Burnell (2015). | MMI3 |
| 4 | References | Aleinikoff, J.N., Reed, J.C., Jr., and Dewitt, E., 1993, The Mount Evans batholith in the Colorado Front Range — Revision of its age and reinterpretation of its structure: Geological Society of America Bulletin, v. 105, p. 791–806. Arbogast, B.F., Knepper, D.H., Langer Jr., W.H., Cappa, J.A., Keller, J.W., Widmann, B.L., Ellefsen, K.J., Klein, T.L., Lucius, J.E., and Dersch, J. S., 2011, Development of Industrial Minerals in Colorado: U.S. Geological Survey Circular 1368, 87 p. Bookstrom, A.A., Naeser, C.W., and Shannon, J.R., 1987, Isotopic age determinations, unaltered and hydrothermally altered igneous rocks, north-central Colorado mineral belt: Isochron/West, v. 49, p. 13–20. Bora, E.T., 2024, Bedrock and surficial geology of the southern half of the Montezuma 7.5’ quadrangle, central Front Range, Colorado, USA: M.S. Thesis, Colorado School of Mines, Golden, CO, USA, 81p. Borsook, A.J., 2025, The Proterozoic geology of the northern half of the Montezuma 7.5-minute quadrangle, Central Front Range, Colorado, USA: M.S. Thesis, Colorado School of Mines, Golden, CO, USA, 101 p. Botinelly, T., 1979, Mineralogy as a guide for exploration in the Montezuma district, central Colorado: U.S. Geological Survey Open-file Report, 70-1177, 16 p. Burnell, J.R., 2015, Historic mining districts of Colorado: Colorado Geological Survey On-Line Report ON-008-08. Chapin, C.E., 2012, Origin of the Colorado Mineral Belt: Geosphere, v. 8, p. 28–43. Dahms, D.E., 2004, Glacial limits in the middle and southern Rocky Mountains, USA, south of the Yellowstone Ice Cap: in: J. Ehlers, P.L. Gibbard (Eds.), Quaternary Glaciations—extent and chronology, part II, Developments in Quaternary Sciences 2. Elsevier, Amsterdam, p. 275–288. Davis, M.W. and Streufert, R.K., 1990, Gold occurrences of Colorado: Colorado Geological Survey Resource Series 28, 101 p. du Bray, E.A., Holm-Denoma, C.S., Lund, K, and Premo, W.R., 2018, Review of the Geochemistry and Metallogeny of Approximately 1.4 Ga Granitoid Intrusions of the Conterminous United States: Scientific Investigations Report 2017 - 5111, 44 p. Horton, J.D., and San Juan, C.A., 2016, Prospect- and mine-related features from U.S. Geological Survey 7.5- and 15-minute topographic quadrangle maps of the United States (ver. 10.0, May 2023): U.S. Geological Survey data release. Kellogg, K.S., Shroba, R.R., Bryant, B., and Premo, W.R., 2008, Geologic Map of the Denver West 30′ × 60′ Quadrangle, North-Central Colorado: U.S. Geological Survey Scientific Investigations Map 3000, scale 1:100,000, 48-p. pamphlet. Kellogg, K.S., Shroba, R.R., Ruleman, C.A., Bohannon, R.G., McIntosh, W.C., Premo, W.R., Cosca, M.A., Moscati, R.J., and Brandt, T.R., 2017, Geologic Map of the Upper Arkansas River Valley Region, north-central Colorado: U.S. Geological Survey Investigations Map 3382, scale 1:50,000, pamphlet, 80 p. Lovering, T.S., 1935, Geology and ore deposits of the Montezuma quadrangle. Colorado: U.S. Geological Survey Professional Paper 178, 119 p. Lovering, T.S., and Goddard, E.N., 1950, Geology and ore deposits of the Front Range, Colorado: U.S. Geological Survey Professional Paper 223, 319 p. Mahatma, A.A., Kuiper, Y.D., Holm-Denoma, C.S., 2022, Evidence for the ~1.4 Ga Picuris orogeny in the central Colorado Front Range: Precambrian Research, v. 382, 106878 (16p.) McFaul, E.J., Mason, G.T., Ferguson, W.B., and Lipin, B.R., 2000, U.S. Geological Survey mineral databases; MRDS and MAS/MILS: U.S. Geological Survey Data Series 522. Powell, L., 2020, The Proterozoic geology of the northern half of the Mount Evans 7.5-minute Quadrangle: M.S. Thesis, Colorado School of Mines, Golden, CO, USA, 58 p. Powell, L., Mahatma, A.A., Kuiper, Y.D., and Ruleman, C.A., 2022, Geologic map of the Mount Evans quadrangle, Clear Creek and Park Counties, Colorado: United States Geological Survey Publications Warehouse, Colorado Geological Survey Open File Report 22–11, scale 1:24,000. Pyanoe, D., 2015, Fluid inclusion and metal ratio analysis of Cordilleran Pb-Zn-Cu-(Ag-Au) veins of the Montezuma district: Summit County Colorado, USA. M.S. Thesis, Colorado State University, Fort Collins, CO, USA, 131 p. Robinson, C.S., Warner, L.A., and Wahlstrom, E.E., 1974, General geology of the Harold D. Roberts Tunnel, Colorado: U.S. Geological Survey Professional Paper 831–B, 46 p. Rosera, J.M., Gaynor, S.P., and Coleman, D.S., 2021, Spatio-temporal shifts in magmatism and mineralization in northern Colorado beginning the late Eocene: Economic Geology, v. 116, p. 987–1010. Ruleman, C.A, Bohannon, R.G., Bryant, B., Shroba, R.R., and Premo, W.R., 2011, Geologic map of the Bailey 30’ x 60’ quadrangle, north-central Colorado: U.S. Geological Survey Scientific Investigations Map 3156, scale 1:100,000, pamphlet, 38 p. Ruleman, C.A., Frothingham, M.G., Brandt, T.R., Shaw, C.A., Caffee, M.W., Brugger, K.A., and Goehring, B.M., 2020, Geologic Map of the Homestake Reservoir 7.5’ quadrangle, Lake, Pitkin, and Eagle Counties, Colorado: U.S. Geological Survey Scientific Investigations Map 3452, scale 1:24,000. Schweitzer, P.N., 2019, Record quality tables for the Mineral Resources Data System (MRDS): U.S. Geological Survey Data Series 20, https://doi.org/10.5066/P9DYLWMP Shockley, D., 2021, Proterozoic Structural History of the Montezuma Mining District in the Central Colorado Front Range: M.S. Thesis, Colorado School of Mines, Golden, CO, USA, 101 p. Shroba, R.R., Kellogg, K.S., and Brandt, T.R., 2014, Geologic Map of the Granite 7.5’ quadrangle, Lake and Chaffee Counties, Colorado: U.S. Geological Survey Scientific Investigations Map 3294, scale 1:24,000, pamphlet 31 p. Tweto, O., and Sims, P.K., 1963, Precambrian ancestry of the Colorado Mineral Belt. Geological Society of America Bulletin, v. 74, no. 8, p. 991-1014. Vanderwilt, J.W., 1947. Mineral Resources of Colorado. Colorado Mineral Resources Board, Denver, Colorado. Warner, L.A., and Robinson, C.S., 1967, Geology of the Harold D. Roberts tunnel, Colorado: station 468+49 to east portal: Geological Society of America Bulletin, v. 78, p. 87–120. | MMI4 |
| 5 | Acknowledgments | Primary mappers (Erick Bora and Ariel Borsook) were supported by EDMAP FY24 No: G21AC10505. Thanks to the Colorado Geological Survey for providing funds for map production and publication. Spencer Sicho provided valuable field assistance and analysis of joints. Pangaea Geospatial produced the map plates and GIS files for this publication. Emily Perman created the 3D oblique. Michael O’Keeffe (CGS) reviewed the Resources section of this sheet. This map publication benefitted from reviews by Jeremy Workman (USGS) and Matt Morgan (CGS). Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. | MMI5 |
| 6 | Resources2 | According to the USGS Mineral Resources Data System (MRDS) (McFaul and others, 2000; Schweitzer, 2019), there are over 100 historic mines within the Montezuma quadrangle, primarily in the northern and western areas of the quadrangle. All mines are metallic mines, with copper, gold, lead, gold, silver, and zinc being the primary commodities. The main ore minerals include chalcopyrite, galena, pyrite, silver (associated with tetrahedrite and tennantite), and sphalerite (McFaul and others, 2000). Minor ore minerals include ankerite, molybdenum, bismuth, tetrahedrite, pyrite, and gold (McFaul and others, 2000; Horton and San Juan, 2016, Schweitzer, 2019). In the east adjacent Mount Blue Sky (formerly Mount Evans) quadrangle, placer claims are located in the South Clear Creek and Geneva Creek drainage areas around Duck Creek and Bruno Gulch (Powell and others, 2022). These placer deposits are believed to be associated with polymetallic vein deposits within the Geneva Creek headwaters and Argentine Peak in the Montezuma quadrangle (Davis and Streufert, 1990; Powell and others, 2022). Similarly to the adjacent Mount Blue Sky quadrangle, the Proterozoic metamorphic (e.g. Xhp, Xh, Xbsg, Xb, Xsb, Xag-1, and Xag-2) and igneous (e.g. units Ygb, Ygsm, Yg, Ygmp, and YXp) basement units do not represent significant metallic commodities. Although veins are prevalent in these units, they are generally subeconomic in value, with only small pyrite crystals sporadically present (Warner and Robinson, 1967; Shockley, 2021). The general vein orientation within the Proterozoic rocks along the trace of the Harold D. Roberts tunnel is inconsistent with the ~020° - 030° trace of the interpreted Montezuma Shear Zone of Warner and Robinson (1967), and the Montezuma Shear Zone is better described as a zone of brittle fractures (Shockley, 2021). There is no evidence along this fracture zone or elsewhere in the Montezuma quadrangle that Proterozoic structures controlled mineralization (Shockley, 2021). Arbogast and others (2011) stated that several kilometer-scale granites in Colorado (including the Silver Plume Granite, unit Yg) are desirable as building stones due to their textures, colors, and crystal sizes. Granites make excellent building materials as the rock weathers slowly and can withstand large amounts of pressure (Arbogast and others, 2011). Potential local sources of sand and gravel in the quadrangle include units Qa, Qac, and Qtp although there is no direct evidence of these deposits being collected. | MMI6 |
| 8 | DOI | https://doi.org/10.58783/cgs.of2309/jjry6780 | MMI7 |
| 9 | OF Number | 23-09 | MMI8 |
| 10 | EDMAP number | G21AC10505 | MMI9 |