| 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 | CrossSectionC | CrossSectionB | GeologicMap | CrossSectionA | CorrelationOfMapUnits |
|---|---|---|---|---|---|---|
| MPu | X | X | -- | -- | -- | X |
| Qa3 | X | -- | X | X | -- | X |
| Qe | X | -- | X | X | X | X |
| Kpl | X | X | X | X | -- | X |
| Qg1 | X | -- | -- | X | -- | X |
| Kplr | X | -- | -- | X | -- | X |
| Kph | X | X | -- | X | -- | X |
| Kpu | X | -- | -- | X | X | X |
| Kcgg | X | X | -- | -- | -- | X |
| Qafo | X | -- | X | X | -- | X |
| af | X | -- | X | X | X | X |
| Qa | X | -- | X | X | X | X |
| Qaf | X | -- | X | X | -- | X |
| Kpm | X | -- | -- | X | -- | X |
| Qa2 | X | -- | X | X | -- | X |
| Qg | X | -- | X | -- | X | X |
| Kn | X | X | -- | X | -- | X |
| Qsw | X | -- | -- | X | -- | X |
| Kpmu | X | X | -- | -- | -- | X |
| Qa1 | X | -- | X | X | -- | X |
| OBJECTID | SAMPLEID | LABNUMBER | LATITUDE | LONGITUDE | UNIT | DEPTH | SAMPLEDESC | ALIQUOTS | EQUIVDOSE | OVERDISPER | U | TH | K2O | H2O | COSMICDOSE | DOSERATE | SAROSL |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 4 | LV-RENA-01 | 5434 | 40.38246154785156 | -105.09532165527344 | Qa | 1.07 | fine to medium sand | 43/44 | 3.83 ± 0.13 | 68 ± 10 | 2.68 ± 0.01 | 8.23 ± 0.01 | 1.99 ± 0.01 | 20 ± 3 | 0.247 ± 0.025 | 2.53 ± 0.07 | 1,500 ± 70 |
| 5 | LV-LRM-01 | 5401 | 40.39400100708008 | -105.11799621582031 | Qa3 | 4.89 | medium sand | 27/35 | 63.33 ± 1.77 | 31 ± 5 | 2.20 ± 0.01 | 12.25 ± 0.01 | 3.92 ± 0.01 | 15 ± 3 | 0.166 ± 0.017 | 4.05 ± 0.21 | 15,625 ± 900 |
| 6 | LV-LRM-03 | 5402 | 40.39400100708008 | -105.11799621582031 | Qa3 | 2.74 | medium sand | 44/45 | 63.20 ± 4.76 | 40 ± 4 | 5.31 ± 0.01 | 27.60 ± 0.01 | 2.91 ± 0.01 | 15 ± 3 | 0.223 ± 0.022 | 4.94 ± 0.15 | 12,780 ± 1025 |
| 8 | LV-WOS-01 | 5397 | 40.387001037597656 | -105.01399993896484 | Qa1 | 0.63 | fine sand to silt | 33/35 | 1.62 ± 0.06 | 20 ± 2 | 5.17 ± 0.01 | 20.30 ± 0.01 | 2.62 ± 0.01 | 10 ± 3 | 0.244 ± 0.024 | 4.63 ± 0.14 | 340 ± 15 |
| OBJECTID | SAMPLEID | LABNUMBER | LATITUDE | LONGITUDE | UNIT | DEPTH | SAMPLEDESC | ALIQUOTS | EQUIVDOSE | OVERDISPER | U | TH | K2O | H2O | COSMICDOSE | DOSERATE | SAROSL | FADINGRATE | ANALYSISMETHOD | SEDIMENTDENSITY | RB | ELEVATION | Field |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 10 | LV-LCL-01 | USU-4305 | 40.498291015625 | -105.11740112304688 | Qafo | 0.69 | poorly sorted sand | 14/15 | 60.90 ± 3.77 | None | 4 | 7.37 | 1.05 | 5 | 0.258 | 3.42 ± 0.17 | 17.08 ± 1.86 | 1.26 ± 0.05 (3) | IRSL | 1.9 | 56 | 1.56 | None |
| 11 | LV-LCL-02 | USU-4306 | 40.48976135253906 | -105.11751556396484 | Qafo | 1.10 | poorly sorted sand | 13/19 | 632.34 ± 107.23 | None | 4.9 | 8.62 | 1.12 | 5 | 0.245 | 3.80 ± 0.20 | 166.2 ± 21.8 | 2.83 ± 1.26 (n=3) | IRSL | 1.9 | 59.7 | 1.56 | None |
| 15 | LV-FCW-01 | USU-4307 | 40.43899917602539 | -105.05110168457031 | Qa | 2 | poorly sorted sand | 14/22 | 10.04 ± 0.94 | None | 3.1 | 9.96 | 1.99 | 5 | 10.215 | 3.42 ± 0.14 | 2.94 ± 0.27 | NA | OSL | 1.9 | 92.4 | 1.49 | None |
| OBJECTID | Source | Notes | URL | DataSources_ID |
|---|---|---|---|---|
| 8 | Online geologic dictionary | None | https://glossary.americangeosciences.org/ | AGI |
| 11 | Baylor University | Geoluminescence Dating Research Lab | https://geosciences.artsandsciences.baylor.edu/about-us/facilities/geoluminescence-dating-research-lab | BAYLOR |
| 7 | CGS | Soil borings conducted by private geotech firm and compiled for this publication by the Colorado Geological Survey | https://coloradogeologicalsurvey.org/ | CGS |
| 6 | City of Loveland | Soil borings conducted by private geotech firm and compiled for this publication by the City of Loveland | https://www.lovgov.org/ | COL Compiled |
| 5 | This study | None | None | DAS1 |
| 9 | Online dictionary | None | https://www.merriam-webster.com/dictionary/geotechnical | DICT1 |
| 4 | Division of Water Resources | None | https://dwr.colorado.gov/ | DWR |
| 3 | Colorado Oil and Gas Conservation Commission | None | https://ecmc.state.co.us/#/home | ECMC |
| 2 | 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 |
| 10 | GeMS standard | None | https://ngmdb.usgs.gov/Info/standards/GeMS/ | GeMS1 |
| 13 | American Geosciences Institute | None | https://glossary.americangeosciences.org/ | GEODICT1 |
| 12 | Utah State University | Luminescence Lab | https://www.usu.edu/geo/osl/ | UTAH |
| OBJECTID | MapUnit | Name | FullName | Age | Description | HierarchyKey | ParagraphStyle | Label | Symbol | AreaFillRGB | AreaFillPatternDescription | DescriptionSourceID | GeoMaterial | GeoMaterialConfidence | DescriptionOfMapUnits_ID |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | None | SURFICIAL DEPOSITS | SURFICIAL DEPOSITS | None | Descriptions of soil-carbonate morphology are after Machette (1985) and Birkeland (1999). Water-well data is compiled from Colorado Division of Water Resources (DWR), 2023. Oil- and gas-well data is compiled from Colorado Energy and Carbon Management Commission (ECMC), 2023. | 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 | Artifical fill | Artifical fill | uppermost Holocene | Artificial fill includes riprap and fill material placed during the construction of roads, railroads, buildings, dams, reclamation of quarry areas, and disturbed areas like active quarries. The unit is poorly sorted clay, silt, sand, and rock fragments. Artificial fill may be locally present in residential or commercial areas but may not be thick enough to map. Fill materials can vary in particle size and may locally include refuse of many types like household and industrial waste. Artificial fill may be subject to settlement, slumping, and erosion if not adequately compacted and (or) if it is placed on unstable slopes. The unit is as much as 7 m thick. | 01.01.01 | DMUUnit1 | af | af | 255-255-255 | None | DAS1 | None | None | DMU03 |
| 4 | None | ALLUVIAL DEPOSITS | ALLUVIAL DEPOSITS | None | None | 01.02 | DMUHeading2 | None | None | None | None | DAS1 | None | None | DMU04 |
| 5 | Qa1 | Alluvium one | Alluvium one | Upper Holocene | The unit is mostly moderately to well-sorted silt to medium sand that is generally brown to very dark brown. Alluvium one underlies modern stream channels and low-lying terraces up to 1.5 m high above adjacent streams. An exposure along the Big Thompson River at NW ¼, sec. 21, T. 5 N., R. 68 W. has approximately 1.7 m of unit Qa1 underlain by clast-supported gravel that is presumed to be unit Qa3. The gravel clasts are round to subround and as much as 13 cm in diameter. There are no carbonate rinds on the clasts. The gravels are weakly imbricated. Secondary carbonate is present near the contact of the overlying finer-grained alluvium with the underlying gravelly alluvium. The carbonate is likely deposited, in-part, by groundwater. Sample LV-WOS-01 was collected at this location approximately 0.6 m below ground surface (bgs) and was analyzed by optically stimulated luminescence (OSL) techniques. The sample yielded an age estimate of 340 ± 15 yrs BP. A radiocarbon sample collected from Qa1 along the Little Thompson River in the Berthoud quadrangle yielded an age estimate of 1,530 ± 30 yr BP (Keller and others, 2017). The unit is a potential source of sand and gravel. Areas underlain by the unit have a 1% annual chance of flooding (Zone A and Zone AE) as mapped by the Federal Emergency Management Agency (FEMA, URL link in references). Unit Qa1 may be interbedded with units Qaf and Qsw locally. The unit may be as much as 4 m thick. | 01.02.01 | DMUUnit1 | Qa1 | Qa1 | 254-246-136 | 156-156-156 ESRI 602 gravel closed | DAS1 | None | None | DMU05 |
| 6 | Qa2 | Alluvium two | Alluvium two | Middle to Lower Holocene | The unit is chiefly poorly sorted, massive clay, silt, and sand. Unit Qa2 is brown to yellowish-brown. Discontinuous gravel beds as much as 7.5 cm thick are present locally. Unit Qa2 is also exposed in a quarry in SE ¼, sec. 16, T. 5 N., R. 69 W. Here, the unit is underlain by clast-supported gravel (unit Qa3). At this site, a soil with a moderately developed Bt horizon and Stage I+ to II Bk horizon is exposed. The unit is correlative with unit Qa2 of nearby quadrangles mapped by the Colorado Geological Survey (CGS). Areas underlain by the unit have a 1% annual chance of flooding (Zone AE) and 0.2% annual chance flood hazard or areas of 1% annual chance flood with an average depth less than one foot or with drainage areas of less than one square mile (Zone X), as mapped by the Federal Emergency Management Agency (FEMA, URL link in references). The unit is as much as 1.8 m thick. | 01.02.02 | DMUUnit1 | Qa2 | Qa2 | 255-246-136 | 215-176-158 ESRI 602 gravel closed | DAS1 | None | None | DMU06 |
| 7 | Qa | Alluvium, undivided | Alluvium, undivided | Holocene | The unit is chiefly comprised of moderately sorted silt to medium sand and is brown to yellowish-brown. Deposits are typically homogenous, but discontinuous pebble-gravel lenses may be present locally. Carbonate development up to Stage II may be present locally. The unit underlies ephemeral drainages in the northwest part of the mapped area and Fossil Creek. Samples LV-FCW-01, collected from an exposed terrace deposit in Fossil Creek (NW ¼, sec. 18, T. 6 N., R. 68 W.) and LV-RENA-01, collected in an exposed terrace deposit in SW ¼, sec. 23, T. 5 N., R. 69. W., were analyzed by OSL techniques. Sample LV-FCW-01 was collected approximately 2 m bgs and yielded an age estimate of 2,940 ± 270 yrs BP. Sample LV-RENA-01 was collected approximately 1.1 m bgs and yielded an age estimate of 1,500 ± 70 yrs BP. The area is not mapped by FEMA, but areas underlain by the unit may be prone to stream flooding. The unit is likely as much as 1.5 m thick. | 01.02.03 | DMUUnit1 | Qa | Qa | 254-251-223 | None | DAS1 | None | None | DMU07 |
| 8 | Qa3 | Alluvium three | Alluvium three | Lower Holocene to Upper Pleistocene | The unit is light brown, light brownish-gray, pale brown, brown, and yellowish-brown. Unit Qa3 consists of clast-supported, pebble- to cobble-gravel and moderately sorted silt to sand. Sandy facies are planar- or cross-bedded. Sand lenses are discontinuous and as much as 0.5 m thick. Channel cut-and-fill structures are present in the unit. Gravel beds and lenses are discontinuous and as much as 2.5 m thick. Clasts are subround to round, as much as 13 cm in diameter, and imbricated locally. No carbonate rinds or secondary carbonate have formed on gravel clasts or within the matrix. Clasts are predominantly white granitic rocks with lesser amounts of metamorphic gneiss and quartzites derived from Precambrian bedrock west of the mapped area. Other clasts consist of sedimentary rocks, mostly sandstone, derived from nearby sedimentary bedrock. The unit is a source of sand and gravel. A gravel quarry in SE ¼, sec. 16, T. 5 N., R. 69 W. exposes the unit. Here, two samples, LV-LRM-01 and LV-LRM-03, were collected from sandy facies and analyzed by OSL techniques. Sample LV-LRM-01 was collected approximately 4.9 m bgs and yielded an age estimate of 15,625 ± 900 yrs BP. Sample LV-LRM-03 was collected approximately 2.7 m bgs and yielded an age estimate of 12,780 ± 1,025 yrs BP. The unit is correlative with unit Qa3 of other nearby CGS maps and Broadway Alluvium of nearby USGS geologic maps; unit Qa3 was mapped as Broadway Alluvium by Cole and Braddock (2009). Units of this age are correlative with the Pinedale glaciation, which began around 30 ka (Kellogg and others, 2008), potentially earlier (Madole and others, 2010), and culminated by 12 ka (Kellogg and others, 2008). The unit is as much as 6 m thick. | 01.02.04 | DMUUnit1 | Qa3 | Qa3 | 254-246-136 | 85-255-0 ESRI 602 gravel closed | DAS1 | None | None | DMU08 |
| 13 | Qsw | Sheetwash alluvium | Sheetwash alluvium | Holocene and Upper Pleistocene | The unit is mapped in one location in the northwest part of the quadrangle. It is comprised chiefly of sediment derived from the Pierre Shale and is yellowish-brown, olive-brown, or grayish in color. Sheetwash alluvium is deposited by overland flow during periods of higher-than-normal precipitation and is chiefly mud, clay, and fine sand. There are likely other areas in the quadrangle that are mantled by sheetwash alluvium, but the unit is not thick enough to map. The unit is not a potential source of sand or gravel. Areas underlain by the unit may be prone to hazards related to flooding, expansive soils, and collapsible soils. Unit Qsw is as much as 1.5 m thick. | 01.02.05 | DMUUnit1 | Qsw | Qsw | 255-255-190 | 04-104-104 ESRI 607 sand | DAS1 | None | None | DMU09 |
| 9 | Qg1 | Gravel one | Gravel one | upper Middle Pleistocene | The unit is poorly exposed in the mapped area and almost completely mantled by eolian sediment (unit Qe). In nearby quadrangles, the unit is chiefly clast supported, pebble- and cobble-gravel and silty sand and varies widely in color; dark brown, very dark-brown, yellowish-brown, dark yellowish-brown, and pinkish gray. The unit underlies surfaces at two elevations, 14 m and 17 m above the modern stream channel. Cole and Braddock (2009) mapped the unit as Slocum Alluvium. The unit is correlative with other Qg1 deposits mapped along the Front Range by CGS. Unit Qg1 may be a local source of sand and gravel and is as much as 9 m thick, but usually less. | 01.02.06 | DMUUnit1 | Qg1 | Qg1 | 255-255-215 | 115-255-223 ESRI 605 breccia open | DAS1 | None | None | DMU10 |
| 10 | Qg | Gravel, undivided | Gravel, undivided | Pleistocene(?) | Shown in cross-section only. The unit consists of unit Qg1 and old gravelly alluvium identified in geotechnical boreholes and DWR well-logs. | 01.02.07 | DMUUnit1 | Qg | Qg | 255-255-215 | 168-56-0 ESRI 605 breccia open | DAS1 | None | None | DMU11 |
| 11 | None | MASS-WASTING DEPOSITS | MASS-WASTING DEPOSITS | None | None | 01.03 | DMUHeading2 | None | None | None | None | DAS1 | None | None | DMU12 |
| 12 | Qaf | Alluvial-fan, debris-flow, and stream-alluvium deposits, undivided | Alluvial-fan, debris-flow, and stream-alluvium deposits, undivided | Holocene | The unit is brown, yellowish-brown, or olive-brown, poorly sorted silt, sand, and matrix-supported pebble gravel. The unit is poorly exposed in the mapped area. Sediments comprising the unit are deposited in fan-shaped lobes at the base of relatively steep, relatively short drainages. Clasts and sand grains are locally derived, primarily from the Pierre Shale but may locally include gravel clasts where gravelly alluvium is present in the source areas. Areas underlain by unit Qaf may experience debris flows or sediment-laden stream and overland-flow floods in the future. The unit is not a potential source of sand or gravel and is as much as 2 m thick. | 01.03.01 | DMUUnit1 | Qaf | Qaf | 255-255-190 | 115-178-255 ESRI 602 gravel closed | DAS1 | None | None | DMU13 |
| 14 | Qafo | Old alluvial-fan, debris-flow, and alluvium deposits | Old alluvial-fan, debris-flow, and alluvium deposits | Upper Pleistocene(?) to upper Middle Pleistocene | The unit is chiefly brown to yellowish-brown, poorly sorted silt, sand, and matrix-supported, pebble gravel. Gravel clasts are predominantly angular to subangular and derived from local sandstone bedrock units. Pebble gravel lenses as much as 3 cm thick are typically discontinuous. Less than 5% of clasts are derived from igneous and metamorphic Precambrian bedrock sourced west of the quadrangle. The unit underlies surfaces at roughly three elevations, indicating there was episodic deposition and stream downcutting during the Pleistocene. Less than 1 km northwest of the mapped area, the unit is exposed in a trench. Here, the unit is comprised of poorly sorted, matrix-supported, pebble- to cobble-gravel with clasts as much as 20 cm in diameter. The unit was mapped as Slocum Alluvium by Cole and Braddock (2009). Although there may be alluvium facies within the units, locally, it is primarily fan alluvium and underlies surfaces with fan, apex, and lobate geomorphology; therefore, the deposits are mapped as unit Qafo. Two samples, LV-LCL-01 and LV-LCL-02, were collected for age dating near the northwest corner of the mapped area. They were both analyzed by infrared stimulated luminescence techniques. Sample LV-LCL-01 was collected approximately 0.7 m bgs and yielded an age estimate of 17.8 ± 1.86 ka. Sample LV-LCL-02 was collected approximately 1.1 m bgs and yielded an age estimate of 166.2 ± 21.8 ka. The former age is much too young for the deposit. Owing to it being within 1 m of the ground surface, potential contamination from younger wind-blown sediment or reworking, pedogenic processes, or biotic processes could result in a younger age. The latter age falls within current age estimates of the Slocum Alluvium or Louviers Alluvium (Bull Lake glaciation). Uranium-series dating of a fossil horn core collected from a deposit mapped as Slocum Alluvium near Canon City, CO, yielded an age estimate of 160,000 ± 60,000 yr (Szabo, 1980). The IRSL age estimate falls in the age range reported by Szabo (1980) and is roughly correlative with previous age estimates of the Slocum Alluvium at the same site as the fossil horn core was collected (Scott and Lindvall, 1970; Lewis, 1970). Conversely, the sample may be correlative with the Bull Lake glaciation (170 to 120 ka) and the Louviers Alluvium mapped in the area (Kellogg and others, 2008). The unit may be a local source of sand or gravel and is as much as 3.7 m thick. | 01.03.02 | DMUUnit1 | Qafo | Qafo | 255-255-190 | 230-0-169 esri 602 gravel closed | DAS1 | None | None | DMU14 |
| 15 | None | EOLIAN DEPOSITS | EOLIAN DEPOSITS | None | None | 01.04 | DMUHeading2 | None | None | None | None | DAS1 | None | None | DMU15 |
| 16 | Qe | Eolian deposits | Eolian deposits | Holocene to Upper Pleistocene(?) | The unit is chiefly comprised of moderately to poorly sorted, silt to medium sand. Unit Qe varies in color; yellowish-brown, light yellowish-brown, brown, light-brown, tan, and reddish-brown. The unit is poorly exposed in and mantles much of the southern and eastern portions of the mapped area; however, it is well-documented in CO DWR well logs (URL in references), geotechnical boreholes, and in nearby quadrangles mapped by CGS. Secondary carbonate is present in unit Qe in nearby quadrangles and the unit likely contains varying degrees of soil development within the Loveland quadrangle. Eolian sediment (unit Qe) is not a potential source of sand in the mapped area. Areas underlain by the unit may be prone to hazards associated with collapsible soils. As much as 6 m of eolian sediment mantles the other surficial and bedrock units in the quadrangle. | 01.04.01 | DMUUnit1 | Qe | Qe | 254-249-194 | None | DAS1 | None | None | DMU16 |
| 17 | None | BEDROCK GEOLOGY | BEDROCK GEOLOGY | None | None | 02 | DMUHeading1 | None | None | None | None | DAS1 | None | None | DMU17 |
| 18 | None | Pierre Shale | Pierre Shale | Upper Cretaceous | None | 02.01 | DMUHeading3 | None | None | None | None | DAS1 | None | None | DMU18 |
| 19 | Kpu | Upper member | Upper member | Upper Cretaceous | The unit consists of valley-forming, gray silty shale and friable, yellow to yellowish-brown sandstone. Concretions are present in the unit. The sandstone within the unit may be correlative with unit Kpus in the Berthoud quadrangle (Keller and others, 2017). Eolian sediment (unit Qe) mantles most of the upper member of the Pierre Shale. Soils derived from unit Kpu are typically grayish-green, gray, or light olive-brown in color. The unit contains index fossil ammonites | 02.01.01 | DMUUnit1 | Kpu | Kpu | 137-137-68 | None | DAS1 | None | None | DMU19 |
| 20 | Kplr | Larimer, Richard, and Rocky Ridge members and intervening shales | Larimer, Richard, and Rocky Ridge members and intervening shales | Upper Cretaceous | The unit is comprised of yellow to tan, moderately indurated sandstone. Sandstones are interbedded with friable shales. Interbedded shales weather to a grayish-green, gray, or light olive-brown color. Sandstones are well-exposed in sec. 14 and sec. 23, T. 6 N., R. 69 W. Here, brownish concretions, some containing a shell hash, are present and abundant. Also present in these outcrops are ophiomorpha burrows and other trace fossils. The unit contains index fossil ammonite | 02.01.02 | DMUUnit1 | Kplr | Kplr | 153-235-128 | None | DAS1 | None | None | DMU20 |
| 21 | Kpm | Middle shale member | Middle shale member | Upper Cretaceous | The unit is comprised of erodible, valley-forming, greenish-gray claystone and sandy siltstone that does not crop out well in the mapped area. Bentonite beds are present locally. Index fossil ammonites | 02.01.03 | DMUUnit1 | Kpm | Kpm | 153-255-204 | None | DAS1 | None | None | DMU21 |
| 22 | Kpmu | Middle, Larimer, Richard, Rocky Ridge, and Upper members, undivided | Middle, Larimer, Richard, Rocky Ridge, and Upper members, undivided | Upper Cretaceous | Shown in cross section only. | 02.01.04 | DMUUnit1 | Kpmu | Kpmu | 153-208-204 | None | DAS1 | None | None | DMU22 |
| 23 | Kph | Hygiene Sandstone member | Hygiene Sandstone member | Upper Cretaceous | The upper part of the member is well-indurated, light-gray, sandstone. The middle part of the unit is friable, gray siltstone. The lower part of the unit is weakly indurated gray sandstone that contains concretions. Much of the unit is mantled by alluvium, old fan alluvium, and eolian deposits. The sandstone facies of the member do not crop out well in the mapped area. Index fossil ammonites | 02.01.05 | DMUUnit1 | Kph | Kph | 128-255-0 | None | DAS1 | None | None | DMU23 |
| 24 | Kpl | Lower member | Lower member | Upper Cretaceous | The unit is comprised of dark olive-brown, valley-forming shale and sandy shale. Concretions are present locally. Bentonite beds are present in the lower portion of the member. The unit is not well-exposed in the mapped area because it is easily eroded. Index fossils | 02.01.06 | DMUUnit1 | Kpl | Kpl | 153-173-128 | None | DAS1 | None | None | DMU24 |
| 25 | Kn | Niobrara Formation | Niobrara Formation | Upper Cretaceous | In the region, two members make up most of the unit: the Fort Hays Limestone member at the bottom and the Smoky Hill Shale member above. The lower member is not present in the mapped area but is mapped just west of the quadrangle boundary in the Masonville quadrangle (Braddock and others, 1970). In the quadrangle, the unit crops out as moderately indurated, yellowish-brown, sandy limestone in location on the western part of the mapped area. The member forms prominent hogbacks along the Front Range. Oil and gas well logs indicate the unit is approximately 100 m thick. | 02.02 | DMUUnit1 | Kn | Kn | 235-255-179 | None | DAS1 | None | None | DMU25 |
| 26 | Kcgg | Colorado Group | Colorado Group | Upper Cretaceous | Includes the Carlile Shale (shale and sandstone), Graneros Shale (shale interbedded with sandstone), and Greenhorn Limestone (shale, chalky-shale, and limestone). Approximately 120 to 140 m thick. | 02.03 | DMUUnit1 | Kcgg | Kcgg | 204-255-48 | None | DAS1 | None | None | DMU26 |
| 28 | MPu | Mesozoic and Paleozoic formations, undivided | Mesozoic and Paleozoic formations, undivided | Mesozoic to Paleozoic | Lower Cretaceous to Paleozoic ages formations, undivided. Colorado Energy and Carbon Management Commission (ECMC, link in references) well logs do not record tops. | 02.04 | DMUUnit1 | MPu | MPu | 137-112-68 (25% transparency) | None | DAS1 | None | None | DMU27 |
| OBJECTID | Term | Definition | DefinitionSourceID | Glossary_ID |
|---|---|---|---|---|
| 27 | ? | something unanswered or unknown | DICT1 | GLO01 |
| 28 | 1 sd | a measure of the dispersion of a frequency distribution that is the square root of the arithmetic mean of the squares of the deviation of each of the class frequencies from the arithmetic mean of the frequency distribution | DICT1 | GLO02 |
| 26 | Age | the length of time during which a being or thing has existed; length of life or existence to the time spoken of or referred to | DICT1 | GLO03 |
| 12 | Base frame | A border enclosing the cross section data | DICT1 | GLO04 |
| 13 | Bedding | In this context, bedding refers to a measurement convention used to describe the orientation, or attitude, of a planar geologic feature. A feature's strike is the azimuth of an imagined horizontal line across the plane, and its dip is the angle of inclination measured downward from horizontal. | AGI | GLO05 |
| 23 | Bedrock | A general term for the rock, usually solid, that underlies soil or other unconsolidated, superficial material. A British syn. of the adjectival form is solid, as in solid geology. | AGI | GLO06 |
| 10 | Boundary | A line that marks the limits of an area | DICT1 | GLO07 |
| 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 | GLO08 |
| 30 | CGS LUR | Colorado Geological Survey Land Use Review | CGS | GLO09 |
| 11 | Contact | (a) A plane or irregular surface between two types or ages of rock; examples are faults, intrusive borders, bedding planes separating distinct strata, and unconformities. (b) The surface between two fluids in a reservoir, i.e. oil and gas, oil and water, or gas and water. Syn: interface. adj. Said of a mineral deposit that occurs at the contact of two unlike rock types. | AGI | GLO10 |
| 25 | Deposit type | Groupings for surficial units in the CMU | DAS1 | GLO11 |
| 5 | DMUHeading1 | GeMS hierarchy formatting term | GeMS1 | GLO12 |
| 6 | DMUHeading2 | GeMS hierarchy formatting term | GeMS1 | GLO13 |
| 7 | DMUHeading3 | GeMS hierarchy formatting term | GeMS1 | GLO14 |
| 4 | DMUUnit1 | GeMS hierarchy formatting term | GeMS1 | GLO15 |
| 36 | dome | A region of flat-lying sedimentary rocks is warped or bowed upward to form a structural dome; | GEODICT1 | GLO16 |
| 29 | DWR | Division of Water Resources | DWR | GLO17 |
| 16 | Elev | A hatch mark shown on the edges of geologic cross sections to denote the elevation | DICT1 | GLO18 |
| 3 | Fault | (a) The process of fracturing, frictional slip, and displacement accumulation that produces a fault. (b) The displacement of the crust on a fault or fault array , as in "Active faulting occurs in California". | AGI | GLO19 |
| 18 | FaultMove | Cartographic symbols showing the relative offset on the fault in cross section | DAS1 | GLO20 |
| 15 | Feature | The location of a significant landform or element shown on cross section | DICT1 | GLO21 |
| 9 | Frame | A border enclosing the cross section data | DICT1 | GLO22 |
| 32 | Geotech | Short for Geotechnical. Refers to the use of geology as a science when applied to an engineering problem such as landfill design, highway construction, landslide repair, tunnel construction, sewage system design, and much more. | DICT1 | GLO23 |
| 19 | Geotech Well | A well used as part of the investigation process carried out on site prior to construction. | AGI | GLO24 |
| 31 | ka | Kilo-annum, one thousand (103) 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 "thousands of years before present" in geological literature. It is not equivalent to the elapsed time interval or duration in "thousands of years" (kyr). | AGI | GLO25 |
| 21 | O&G Well | Oil well- well from which petroleum is obtained by pumping or by natural flow. Some statutes define the term on the basis of the gas-oil ratio. Gas well- A well that is capable of producing natural gas or that produces chiefly natural gas. Some statutes define the term on the basis of the gas-oil ratio. | AGI | GLO26 |
| 14 | OSL | Optically-Stimulated Luminescence is a late Quaternary dating technique used to date the last time quartz sediment was exposed to light. As sediment is transported by wind, water, or ice, it is exposed to sunlight and zeroed of any previous luminescence signal. | BAYLOR | GLO27 |
| 24 | Quaternary | The upper system of the Cenozoic Erathem of the Standard Global Chronostratigraphic Scale, above the Tertiary System. Also the time during which these rocks were formed, the Quaternary Period, covering the time span between 1.75 Ma and the present. | AGI | GLO28 |
| 34 | 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 | GLO29 |
| 8 | Surface | The topographic profile of the cross section | DAS1 | GLO30 |
| 20 | Water Feature | The location of a significant water element shown on cross section | DICT1 | GLO32 |
| 22 | Water Well | (a) A well that extracts water from the saturated zone or that yields useful supplies of water. (b) A well that obtains groundwater information or that replenishes groundwater. (c) A well drilled for oil but yielding only water. | AGI | GLO33 |
| 33 | yr | year | DICT1 | GLO34 |
| OBJECTID | MapProperty | MapPropertyValue | MiscellaneousMapInformation_ID |
|---|---|---|---|
| 1 | ACKNOWLEDGMENTS | The following people greatly added to and improved the results of this mapping project: Ralph Shroba (U.S. Geological Survey Emeritus and CGS employee) provided an expert review of the map products. Jonathan White (CGS Mapping Geologist and STATEMAP Program Manager) provided an internal review. Matt Morgan (CGS Director and State Geologist) provided an internal review of the text and contributed knowledge on the local geology. Caitlin Bernier (Pangaea Geospatial) performed map layout and production. Ashton Killen (Colorado School of Mines graduate student and CGS staff) assisted with fieldwork and sample collection. A special thanks to: Brad Fancher with Loveland Ready Mix for allowing access to an important exposure made by quarry excavation. Brian Hayes and Debbie Eley with the City of Loveland Parks & Recreation Department helped coordinate permits and access to city-owned property. Zoe Shark and Matthew Parker with the City of Fort Collins coordinated permits and access to city-owned property. Andy Steinert, Matt Wellick, and Dylan Casey with the USDA-NRCS helped trench and describe soils. Steve Harem with the Larimer County Landfill granted and coordinated access to landfill land and allowing us to trench in two locations to collect samples. | MMI01 |
| 12 | STATEMAP AGREEMENT | This mapping project was funded jointly by the Colorado Geological Survey and the U.S. Geological Survey through the National Cooperative Mapping Program under STATEMAP agreement G22AC00302. | MMI02 |
| 13 | TITLE | GEOLOGIC MAP OF THE LOVELAND QUADRANGLE LARIMER COUNTY, COLORADO | MMI03 |
| 14 | AUTHOR | By Kassandra O. Lindsey | MMI04 |
| 15 | YEAR | 2024 | MMI05 |
| 16 | REFERENCES | Balescu, S., and Lamothe, M., 1994, Comparison of TL and IRSL age estimates of feldspar coarse grains from waterlain sediments: Quaternary Science Review, v. 13, p. 437-444. https://doi.org/10.1016/0277-3791(94)90056-6 Birkeland, P.W., 1999, Soils and geomorphology: New York, Oxford University Press, 430 p. Braddock, W.A., Calvert, R.H., Gawarecki, S.J., and Nutalaya, Prinya, 1970, Geologic map of the Masonville quadrangle, Larimer County, Colorado: U.S. Geological Survey, Map GQ-832, scale 1:24,000. http://doi.org/10.3133/gq832 CO DWR (Colorado Division of Water Resources), 2023, Driller’s logs incorporated with water-well permits. https://dwr.colorado.gov/services/data-information/gis CO ECMC (Colorado Energy and Carbon Management Commission), 2023, Data and maps. https://cogccmap.state.co.us/cogcc_gis_online/ Cole, J.C., and Braddock, W.A., 2009, Geologic map of the Estes Park 30’ x 60’ quadrangle, north-central Colorado: U.S. Geological Survey, Scientific Investigations Map SIM 3039, scale 1:100,000. http://doi.org/10.3133/sim3039 Durcan, J.A., King, G.E., and Duller, G.A.T., 2015, DRAC – Dose rate and age calculator for trapped charge dating: Quaternary Geocryology, v. 28, p. 54-61. https://doi.org/10.1016/j.quageo.2015.03.012 FEMA, FEMA flood map service center: access in February 2023 at https://msc.fema.gov/portal/home Galbraith, R.F., and Roberts, R.G., 2012, Statistical aspects of equivalent dose and error calculation and display in OSL dating – An overview and some recommendations: Quaternary Geochronology, v. 11, p. 1-27. https://doi.org/10.1016/j.quageo.2012.04.020 Guérin, G., Mercier, N., and Adamiec, G., 2011, Dose-rate conversion factors – update: Ancient TL, v. 29, p. 5-8. Huntley, D.J., and Lamothe, M., 2001, Ubiquity of anomalous fading in K-feldspars and the measurement and correction for it in optical dating: Canadian Journal of Earth Sciences, v. 38, p. 1093-1106. https://doi.org/10.1139/e01-013 Keller, S.M., Lindsey, K.O., and Morgan, M.L., 2017, Geologic map of the Berthoud quadrangle, Larimer, Weld, and Boulder counties: Colorado Geological Survey, OF-17-03, scale 1:24,000. 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 2000, 1:100,000. http://doi.org/10.3133/sim3000 Lamothe, M., Auclair, M., Hamzaoui, C., and Huot, S., 2003, Towards a prediction of long-term anomalous fading of feldspar IRSL: Radiation Measurements, v. 37, p. 493-498. https://doi.org/10.1016/S1350-4487(03)00016-7 Lewis, G.E., 1970, New discoveries of Pleistocene bisons and peccaries in Colorado in Geological Survey Research 1970: U.S. Geological Survey Professional Paper 700-B, p. B137-B140. Lindsey, K.O., and Morgan, M.L., 2025, Unpublished geochronological data of unit Qg1 (Slocum Alluvium type section), collected in the Canon City quadrangle, Colorado: Colorado Geological Survey, unpublished data. 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. Madole, R.F., Honke, J., and Langdon, P.G., 2010, Evidence from the Front Range, Colorado, indicates that Pinedale glaciation began before 31,000 yr ago: Geological Society of America, Abstracts and Programs, v. 42, no. 5, p. 363. Machette, M.N., 1985, Calcic soils of the southwestern United States: Geological Society of America Special Paper no. 203, pp 1-21. http://doi.org/10.1130/SPE203 Mejdahl, V., 1979, Thermoluminescence dating: Beta-dose attenuation in quartz grains: Archaeometry, v. 21, p. 61-72. http://doi.org/10.1111/j.1475-4754.1979.tb00241.x Munsell Color, 1994, Munsell soil color charts, 1990 edition revised: Newburgh, NY, Macbeth Division of Kollmorgen Instruments Corp., 14 p. Murray, A.S., and Wintle, A.G., 2003, The single aliquot regenerative dose protocol – Potential for improvements in reliability: Radiation Measurements, v. 37, no. 4-5, p. 377-381. https://doi.org/10.1016/S1350-4487(03)00053-2 Prescott, J.R., and Hutton, J.T., 1994, Cosmic ray contributions to dose rates for luminescence and ESR dating: Radiation Measurements, v. 23, p. 497-500. https://doi.org/10.1016/1350-4487(94)90086- Scott, G.R., and Cobban, W.A., 1965, Geologic and biostratigraphic map of the Pierre Shale between Jarre Creek and Loveland, Colorado: U.S. Geological Survey Miscellaneous Geological Investigations Map I-439, scale 1:48,000. http://doi.org/10.3133/i439 Scott, G.R., and Lindvall, R.M., 1970, Geology of new occurrences of Pleistocene bisons and peccaries in Colorado in Geological Survey Research 1970: U.S. Geological Survey Professional Paper700-B, p. B141-B149. Szabo, B.J., 1980, Results and assessment of Uranium-series datin go f vertebrate fossils from Quaternary alluviums in Colorado: Arctic and Alpine Research, v. 12, no. 1, p. 95-100. https://doi.org/10.1080/00040851.1980.12004166 Wintle, A.G., and Murray, A.S., 2006, A review of quartz optically stimulated luminescence characteristics and their relevance in single-aliquot regeneration dating protocols: Radiation Measurements, v. 41, no. 4, p. 369-391. https://doi.org/10.1016/j.radmeas.2005.11.001 Wallinga, J., Murray, A., and Wintle, A., 2000, The single-aliquot regenerative-dose (SAR) protocol applied to coarse-grain feldspar: Radiation Measurements, v. 32, p. 529-533. https://doi.org/10.1016/S1350-4487(00)00091-3 Weimer, 1996, Guide to petroleum geology and Laramide orogeny, Denver Basin and Front Range, Colorado: U.S. Geological Survey, Bulletin 51, 133 p. https://doi.org/10.58783/cgs.b51.bsvl1261 | MMI06 |
| 17 | 1GEOLOGIC HISTORY | The Loveland quadrangle is situated in the northern part of the Colorado Piedmont section of the Great Plains. The western edge of the Denver Basin underlies the area and is bounded by the Southern Rocky Mountains on the west side. The mapped area is directly south of the Fort Collins 1:24,000-scale quadrangle and contains part of the City of Fort Collins and most of the City of Loveland. The Western Interior Seaway (WIS) occupied most of Colorado during the Late Cretaceous, depositing transgressive and regressive sedimentary rock sequences that underlie the mapped area. The early phase of the Laramide orogeny (~70 Ma) is correlative with the final stages of the WIS in the region (Weimer, 1996). The Carlile Shale, Greenhorn Limestone, and Codell Sandstone (collectively known as the Colorado Group, map unit Kcgg), Niobrara Formation (Kn), and the Pierre Shale (units Kpu, Kplr, Kpm, Kph, and Kpl) record some of the final WIS transgressive and regressive marine sequences. The Pierre Shale members and the upper part of the Niobrara Formation are the only Cretaceous rocks exposed in the mapped area; however, just west of the quadrangle, older Mesozoic and Paleozoic rocks are exposed in the fold belt of the eastern margin of the Southern Rocky Mountains (Braddock and others, 1970). The Pierre Shale and its derived soils contain expansive clay minerals that have a high-swell potential, making areas underlain by the unit prone to swelling and collapsible soil hazards. Major thrust faulting and associated structures are located west of the mapped area, on the Masonville quadrangle (Braddock and others, 1970). A Colorado Energy and Carbon Management Commission (ECMC) oil and gas well located south of the quadrangle boundary (60024) indicates the top of the Niobrara Formation (unit Kn) is at least 150 m higher than it should be. This is based on the assumption that unit Kpl maintains a consistent thickness throughout the section and dips on the western end of the quadrangle boundary start at about 25-degrees and decrease to about 20-degrees where Kph and Kpmu are exposed on the surface. With these assumptions, a thrust fault or high-angle fault can account for the higher Niobrara top at the location of well 60024 (cross-section C-C’). Alternatively, unit Kpl could have undergone structural thinning, owing to its relatively soft, ductile characteristics, allowing unit Kn to more steeply dip on the western side of the mapped area. However, with this hypothesis, unit Kn appears to project to the surface on the Masonville quadrangle where Braddock and others (1970) did not map it. Without more subsurface data, it is difficult to fully identify the structural relationships of these units in this area. All oil and gas data obtained from the ECMC (URL link in references). | MMI07 |
| 18 | 2GEOLOGIC HISTORY | start at about 25-degrees and decrease to about 20-degrees where Kph and Kpmu are exposed on the surface. With these assumptions, a thrust fault or high-angle fault can account for the higher Niobrara top at the location of well 60024 (cross-section C-C’). Alternatively, unit Kpl could have undergone structural thinning, owing to its relatively soft, ductile characteristics, allowing unit Kn to more steeply dip on the western side of the mapped area. However, with this hypothesis, unit Kn appears to project to the surface on the Masonville quadrangle where Braddock and others (1970) did not map it. Without more subsurface data, it is difficult to fully identify the structural relationships of these units in this area. All oil and gas data obtained from the ECMC (URL link in references). The Windsor Wrench Fault Zone is located east of the mapped area (Weimer, 1996). An associated thrust fault and dome are mapped on the Berthoud-Loveland quadrangle border by Keller and others (2017). On the Berthoud quadrangle, there is an approximately 9 m upward inflection of the base of unit Kn. The dome projects to roughly between ECMC wells 06175 and 05073 on the Loveland quadrangle; between wells 06175 and 06110, well logs record a 14 m upward inflection of the tops of units Kn and Kcgg. The thrust fault is more difficult to identify in well logs. There is a noticeable increase in dip beginning on the eastern flank of the dome around wells 05073 and 05074 that becomes relatively consistent through the eastern edge of the quadrangle. The thrust fault projects between wells 06165 and 06181, and there is a difference of approximately 113 m of both the tops of the Niobrara Formation (unit Kn) and Codell Sandstone (unit Kcgg) between the two wells. Owing to the relatively consistent easterly dip of the units in the area of the projected thrust fault, it is possible that it begins to attenuate further north along the fault strike and that the fault only extends into and offsets unit Kcgg, or older, units. All oil and gas data obtained from the ECMC (URL link in references). | MMI08 |
| 19 | 3GEOLOGIC HISTORY | Structural deformation in the area formed traps that contribute to hydrocarbon accumulation in Cretaceous units. The Loveland quadrangle is located in a localized, isolated portion of the Wattenberg Field on the field’s western edge. The Wattenberg Field is a world-class oil and gas production area (Weimer, 1996). In contrast to its hydrocarbon potential, the area within the quadrangle does not contain major groundwater resources because the Fox Hills Sandstone and Laramie Formation and associated aquifers are not present here. There are five alluvial units mapped in the quadrangle. Unit Qg is comprised of unit Qg1 and older gravel documented in well logs and geotechnical boring logs, but eolian sediment (unit Qe) conceals most of the older gravel in the mapped area; therefore, unit Qg is only shown on the cross-section. Unit Qg1, correlative with deposits previously mapped as Slocum Alluvium, crops out along the Big Thompson River and underlies surfaces approximately 14 and 17 m above the stream channel. Unit Qg1 and Qg may be a source of sand and gravel. Perched, localized groundwater may be present within these gravel units. As these Middle Pleistocene to late Middle Pleistocene aged fluvial gravels were deposited, coeval or possibly slightly earlier, river systems were periodically depositing sediments that now comprise unit Qafo. These fan deposits have since been incised, exposing members of the Pierre Shale along the gully margins. Unit Qafo underlies fan-shaped surfaces that are preserved at several (at least three) distinct levels, which may indicate an episodic adjustment in base-level coupled with multiple episodes of deposition during the Pleistocene. Two samples collected from unit Qafo, LV-LCL-01 and LV-LCL-02, were analyzed by infrared stimulated luminescence techniques, and yielded age estimates of 17.8 ± 1.86 ka and 166.2 ± 21.8 ka, respectively. Though the samples were taken at different sites below the same fan surface, the elevations of the samples are within approximately 1 m of each other. This age gap could indicate the great spans of time between depositional periods and indicate that episodic deposition occurred during both the Pinedale glaciation (Late Pleistocene) and Bull Lake glaciation (late Middle Pleistocene). It is more likely that LV-LCL-01 may have been contaminated by younger sediment from pedogenic, biotic, and (or) other geologic processes such as younger eolian sediment deposition and infiltration to the subsurface. The older of the two samples could be correlative with either the early part of the Bull Lake glaciation, which began sometime around 170 ka (Kellogg and others, 2008), potentially as early as 200 ka (Madole, 1991), or with deposits mapped as the Slocum Alluvium along the Front Range. The Slocum Alluvium was dated to around 160,000 ± 60,000 years in Canon City, CO (Szabo, 1980); however, more recent optically stimulated luminescence (OSL) analysis of samples collected by CGS geologist from the same deposit indicates that parts of it may be as young as ~34 ka (Lindsey and Morgan, 2025). Unit Qafo is not a likely source of sand and gravel. Perched groundwater may be present locally, especially in areas underlain by shales and claystones of the Pierre Shale. The clayey minerals form a natural barrier to groundwater flow, leading to locally perched groundwater. | MMI09 |
| 20 | 4GEOLOGIC HISTORY | of the samples are within approximately 1 m of each other. This age gap could indicate the great spans of time between depositional periods and indicate that episodic deposition occurred during both the Pinedale glaciation (Late Pleistocene) and Bull Lake glaciation (late Middle Pleistocene). It is more likely that LV-LCL-01 may have been contaminated by younger sediment from pedogenic, biotic, and (or) other geologic processes such as younger eolian sediment deposition and infiltration to the subsurface. The older of the two samples could be correlative with either the early part of the Bull Lake glaciation, which began sometime around 170 ka (Kellogg and others, 2008), potentially as early as 200 ka (Madole, 1991), or with deposits mapped as the Slocum Alluvium along the Front Range. The Slocum Alluvium was dated to around 160,000 ± 60,000 years in Canon City, CO (Szabo, 1980); however, more recent optically stimulated luminescence (OSL) analysis of samples collected by CGS geologist from the same deposit indicates that parts of it may be as young as ~34 ka (Lindsey and Morgan, 2025). Unit Qafo is not a likely source of sand and gravel. Perched groundwater may be present locally, especially in areas underlain by shales and claystones of the Pierre Shale. The clayey minerals form a natural barrier to groundwater flow, leading to locally perched groundwater. Along the Big Thompson River, a series of younger deposits underlie inset terraces topographically below unit Qg1. The upper part of unit Qa3 records the end of the Pinedale glaciation in the mapped area. Two samples (LV-LRM-01 and LV-LRM-03) were collected from the unit and analyzed by OSL techniques. Sample LV-LRM-01 was collected 4.9 m below ground surface (bgs) and yielded an age estimate of 15,625 ± 900 yrs BP. Sample LV-LRM-03 was collected 2.7 m bgs and yielded an age estimate of 12,780 ± 1,025 yrs BP. Unit Qa2 directly overlies unit Qa3 along the Big Thompson River, suggesting that unit Qa3 forms part of the modern river valley’s subsurface. Deposits mapped as unit Qa3 are a source of sand and gravel. Perched groundwater may be present in the unit, especially it is underlain by the Pierre Shale. Since unit Qa2 was deposited, the river has incised further and deposited Upper Holocene alluvium (unit Qa1) which underlies the modern river channel and recent floodplains. A sample was collected from a cutbank, LV-WOS-01, in a terrace approximately 2 m high. It yielded an OSL age estimate of 340 ± 15 yrs BP. The sample was taken at the base of a sandy alluvial deposit, approximately 0.6 m below ground surface, above the units contact with a clast-supported cobble-gravel assumed to be unit Qa3. The possibility of contamination by younger sediments is uncertain. Units Qa1 and Qa2 are sometimes mapped together as unit Qa in parts of the mapped area where either: (1) the units are not differentiable at this map scale such as along Fossil Creek, or (2) ephemeral drainages have deposited alluvium periodically during the Holocene such as those adjacent to unit Qafo in the western part of the mapped area. Two samples collected from unit Qa, LV-FCW-01 and LV-RENA-01, were analyzed by OSL techniques and yielded age estimates of 2,940 ± 270 yrs BP and 1,500 ± 70 yrs BP, respectively. Areas underlain by Qa2, Qa1, and Qa may be prone to flooding. Other Holocene and Upper Pleistocene deposits include younger debris-flow deposits (unit Qaf) and sheetwash alluvium (unit Qsw), which were deposited during periods of above-average precipitation. Areas underlain by units Qaf and Qsw may be prone to debris flows, overland flow, and (or) stream or sheet flooding. Perched groundwater may be present in these same areas. Eolian sediment (unit Qe), also primarily deposited during the Holocene and potentially during the Upper Pleistocene, in the quadrangle, is mapped primarily in the eastern and southern portions of the mapped area and mantles most of the older Quaternary and bedrock units. Areas underlain by unit Qe may be prone to settlement related to collapsible soils. All water-well logs are obtained from the Colorado Department of Water Resources (URL in references). | MMI10 |
| 21 | 5GEOLOGIC HISTORY | source of sand and gravel. Perched groundwater may be present in the unit, especially if it is underlain by the Pierre Shale. Since unit Qa2 was deposited, the river has incised further and deposited Upper Holocene alluvium (unit Qa1) which underlies the modern river channel and recent floodplains. A sample was collected from a cutbank, LV-WOS-01, in a terrace approximately 2 m high. It yielded an OSL age estimate of 340 ± 15 yrs BP. The sample was taken at the base of a sandy alluvial deposit, approximately 0.6 m below ground surface, above the units contact with a clast-supported cobble-gravel assumed to be unit Qa3. The possibility of contamination by younger sediments is uncertain. Units Qa1 and Qa2 are sometimes mapped together as unit Qa in parts of the mapped area where either: (1) the units are not differentiable at this map scale such as along Fossil Creek, or (2) ephemeral drainages have deposited alluvium periodically during the Holocene such as those adjacent to unit Qafo in the western part of the mapped area. Two samples collected from unit Qa, LV-FCW-01 and LV-RENA-01, were analyzed by OSL techniques and yielded age estimates of 2,940 ± 270 yrs BP and 1,500 ± 70 yrs BP, respectively. Areas underlain by Qa2, Qa1, and Qa may be prone to flooding. Other Holocene and Upper Pleistocene deposits include younger debris-flow deposits (unit Qaf) and sheetwash alluvium (unit Qsw), which were deposited during periods of above-average precipitation. Areas underlain by units Qaf and Qsw may be prone to debris flows, overland flow, and (or) stream or sheet flooding. Perched groundwater may be present in these same areas. Eolian sediment (unit Qe), also primarily deposited during the Holocene and potentially during the Upper Pleistocene, in the quadrangle, is mapped primarily in the eastern and southern portions of the mapped area and mantles most of the older Quaternary and bedrock units. Areas underlain by unit Qe may be prone to settlement related to collapsible soils. All water-well logs are obtained from the Colorado Department of Water Resources (URL in references). | MMI11 |