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 | GeologicMap | CrossSectionC | CrossSectionA | CrossSectionB | CrossSectionD | CorrelationOfMapUnits |
---|---|---|---|---|---|---|---|
Kcgg | X | -- | -- | X | -- | -- | X |
Kph | X | -- | -- | X | -- | -- | X |
Qa2 | X | X | X | -- | X | X | X |
Qa3 | X | X | X | -- | X | X | X |
Kplr | X | -- | -- | X | -- | -- | X |
Kpm | X | -- | -- | X | -- | -- | X |
Qg2 | X | X | -- | -- | -- | X | X |
Kd | X | -- | -- | X | -- | -- | X |
af | X | X | -- | -- | -- | -- | X |
Kpt/Kpu | X | X | X | X | X | X | X |
Qa1 | X | X | X | -- | X | X | X |
Qg1 | X | X | -- | -- | -- | -- | X |
No data | X | -- | X | X | X | X | -- |
Kpl | X | -- | -- | X | -- | -- | X |
Kn | X | -- | -- | X | -- | -- | X |
water | X | X | -- | -- | X | -- | -- |
Qa | X | X | -- | -- | X | -- | X |
gp | X | X | -- | -- | -- | -- | -- |
Kfh | X | X | -- | X | -- | -- | X |
Qe | X | X | X | -- | X | X | X |
OBJECTID | Source | Notes | URL | DataSources_ID | /tr>/thead>
---|---|---|---|---|
9/td> | Baylor University Geosciences/td> | None/td> | https://geosciences.artsandsciences.baylor.edu//td> | BAYLOR/td>/tr> |
8/td> | Beta Analytics, Inc/td> | None/td> | https://www.radiocarbon.com//td> | BETA/td>/tr> |
11/td> | Colorado Geological Survey (CGS) (geotechnical borehole data)/td> | None/td> | None/td> | CGS/td>/tr> |
6/td> | Colorado Oil and Gas Conservation Commission/td> | None/td> | https://co.colorado.gov/natural-resources-colorado-oil-and-gas-conservation-commission/td> | COGCC/td>/tr> |
2/td> | This study/td> | None/td> | None/td> | DAS1/td>/tr> |
3/td> | Online dictionary/td> | None/td> | https://www.dictionary.com/td> | DICT1/td>/tr> |
7/td> | Division of Water Resources/td> | None/td> | https://dwr.colorado.gov//td> | DWR1/td>/tr> |
1/td> | 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./td> | None/td> | https://ngmdb.usgs.gov/fgdc_gds/geolsymstd.php/td> | FGDC-STD-013-2006/td>/tr> |
5/td> | GeMS standard/td> | None/td> | https://ngmdb.usgs.gov/Info/standards/GeMS//td> | GeMS1/td>/tr> |
4/td> | Online geologic dictionary/td> | None/td> | https://geology.com/geology-dictionary.shtml/td> | GEODICT1/td>/tr> |
10/td> | Guide to the petroleum geology and the Laramide orogeny, Denver Basin and the Front Range, Weimer, R.J., 1996 (fault traces at ground surface)/td> | None/td> | https://coloradogeologicalsurvey.org/publications/denver-basin-front-range-colorado-petroleum-geology-laramide-orogen/td> | WEIMER/td>/tr> |
12/td> | Town of Windsor (geotechnical borehole data, particle size analyses)/td> | None/td> | None/td> | WINDSOR/td>/tr> |
OBJECTID | MapUnit | Name | FullName | Age | Description | HierarchyKey | ParagraphStyle | Label | Symbol | AreaFillRGB | AreaFillPatternDescription | DescriptionSourceID | GeoMaterial | GeoMaterialConfidence | DescriptionOfMapUnits_ID | /tr>/thead>
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
2/td> | None/td> | SURFICIAL DEPOSITS/td> | SURFICIAL DEPOSITS/td> | None/td> | For more detail on grain size, sorting, color, secondary calcium carbonate, and other characteristics of surficial map units see Table 1; general characteristics are presented below in the text describing the map units. For details on geologic hazards (e.g., flood potential) of map units, see the Plate 2 section on Mineral Resources, Groundwater Resources, and Geologic Hazards. For radiocarbon and optically stimulated luminescence (OSL) ages of select map units see Table 2 and for results of grain-size analyses of Quaternary units see Table 3. Subdivision of the Quaternary follows the International Chronostratigraphic Chart, v 2020/01 (International Commission on Stratigraphy, International Union of Geological Sciences, 2020). Particle-size designation is according to the Udden-Wentworth grain-size scale (see Nichols, 2009), but (in Table 1) modified such that each sand-size category is divided into a coarser (U) and a finer (L) sub-category with the aid of a sand grain-size card (US GeoSupply, Incorporated, 2020). For example, very coarse (vc) sand is divided into the categories vcU (very coarse – coarser) and vcL (very coarse – finer). In Table 1 the colors are designated with the aid of Munsell soil color charts (Munsell Color, 1991). Description of soil-carbonate morphology is after Machette (1985), and the type of effervescence of sediment or soil observed when treated with dilute hydrochloric acid is according to U.S. Department of Agriculture (2018)./td> | 01/td> | DMUHeading1/td> | SURFICIAL DEPOSITS/td> | None/td> | None/td> | None/td> | DAS1/td> | None/td> | None/td> | DMU01/td>/tr> |
3/td> | None/td> | HUMAN-MADE DEPOSITS/td> | None/td> | None/td> | None/td> | 01-01/td> | DMUHeading2/td> | HUMAN-MADE DEPOSITS/td> | None/td> | None/td> | None/td> | DAS1/td> | None/td> | None/td> | DMU02/td>/tr> |
4/td> | af/td> | Artifical fill/td> | Artifical fill/td> | Upper Holocene/td> | Mostly riprap, fill material, and, locally, refuse placed during construction of roads, railroads, buildings, dams, and landfills. The fill deposits generally consist of unsorted clay, silt, sand, and rock fragments. Typically, the unit is less than 6 m thick. Some deposits of artificial fill are not mapped because they are too small to show at map scale. Artificial fill may be subject to settlement, slumping, and erosion if not adequately compacted and (or) if placed on unstable slopes./td> | 01-01-01/td> | DMUUnit1/td> | af/td> | af/td> | 255-255-255/td> | None/td> | DAS1/td> | "Made" or human-engineered land/td> | High/td> | DMU03/td>/tr> |
5/td> | None/td> | ALLUVIAL DEPOSITS/td> | ALLUVIAL DEPOSITS/td> | None/td> | None/td> | 01-02/td> | DMUHeading2/td> | ALLUVIAL DEPOSITS/td> | None/td> | None/td> | None/td> | DAS1/td> | None/td> | None/td> | DMU04/td>/tr> |
6/td> | Qa1/td> | Alluvium one/td> | Alluvium one/td> | Upper Holocene/td> | Unit Qa1 occupies active and historically active channels of the Cache la Poudre River and Big Thompson River. In these channels the coarse-grained sediment of the unit typically forms point bars of gravelly sand or sand, with the bars being up to several meters wide, up to 20 m long, and as high as 0.6 m above stream level. Sand content increases with depth in some point bars. Sand in point bars ranges from medium to very coarse and is light gray and gray (hue 10YR), angular to subrounded, moderately sorted, loose, and without secondary carbonate. Sand composition is 85 percent quartz, 10 percent feldspar and other nonopaque minerals (including mica), and 5 percent opaques. Gravel ranges from granules up to cobbles 17 cm in diameter (or largest dimension) and the clasts are subrounded to rounded. Gravel consists of granitics, granitic gneiss, dark fine-grained metamorphics, quartzite, vein quartz, and rare sandstone and volcanics. Fine-grained sediment is locally present in channel bottoms and banks. It is mostly a dark-brown mixture of clay, silt, and very fine to fine sand, and can form a veneer 6 to 8 cm thick overlying coarser sediment. Thickness of unit Qa1 is not known but may be 2 m or less. Within the Windsor quadrangle unit Qa1 is not likely to be a potential source of sand and gravel because of the paucity and relatively small size of point bars. Areas mapped as unit Qa1 are prone to flooding./td> | 01-02-01/td> | DMUUnit1/td> | Qa1/td> | Qa1/td> | 254-246-136/td> | 156-156-156 ESRI 601 gravel open/td> | DAS1/td> | Alluvial sediment, mostly fine-grained/td> | High/td> | DMU05/td>/tr> |
7/td> | Qa/td> | Alluvium/td> | Alluvium/td> | Upper Holocene/td> | Unit Qa covers the flat valley floor of Fossil Creek, a tributary to the Cache la Poudre River, and occurs in small tributary drainages to that river and to the Big Thompson River. In its physical properties and position in the landscape unit Qa correlates with unit Qa of Sheep Draw, also tributary to the Cache la Poudre River, in the Bracewell quadrangle adjacent to the east (Palkovic, 2020), and to unit Qa in tributaries to St. Vrain Creek in the Johnstown quadrangle adjacent to the south (Palkovic and Morgan, 2017). Based upon radiocarbon ages in Box Elder Creek (in the Hardin quadrangle, ~45 km to the southeast; Palkovic and Morgan, 2021), unit Qa sediments appear to coeval with unit Qa2 sediments in the South Platte River valley (Keller and Morgan, 2022). By analogy, the unit Qa sediments of the Windsor quadrangle may be coeval with unit Qa2 in the valleys of the Cache la Poudre River and Big Thompson River. Generally, in the Colorado Piedmont quadrangles mapped by the Colorado Geological Survey (CGS), unit Qa sediments are finer-grained than unit Qa2 sediments, probably because of the smaller stream discharges and velocities in unit Qa tributary streams compared to those of the unit Qa2 streams receiving the tributaries. Unit Qa is poorly exposed in the Windsor quadrangle. Based upon data from one field station (a trench to which access was not possible), three geotechnical boreholes, and one water well, unit Qa consists of brown (hue 10YR) clay, silty to sandy clay, and clayey sand. Thicknesses from water well drillers’ logs (Colorado Division of Water Resources [DWR]), 2021; and geotechnical boreholes (Colorado Geological Survey [CGS], 2021; Town of Windsor, 2021) boreholes are 2.1 m, 4.3 m, and 4.9 m deep. The chart for correlation of map units for the Windsor quadrangle is presented in Plate 2. Contacts between unit Qa and older units Qe and Qa3 are not exposed in the quadrangle. Based upon relative ages of the geologic units, however, units Qa and Qa2 possibly are locally incised into unit Qe (eolian sediment). On the basis of one geotechnical borehole, unit Qa in the valley of Fossil Creek may overlie unit Qa3. This is analogous to unit Qa demonstrably overlying unit Qa3 in the Box Elder Creek valley in the Hardin quadrangle. Areas mapped as Qa may be prone to flooding (see Mineral Resources, Groundwater Resources, and Geologic Hazards in Plate 2). /td> | 01-02-02/td> | DMUUnit1/td> | Qa/td> | Qa/td> | 254-246-136/td> | None/td> | DAS1/td> | Alluvial sediment, mostly fine-grained/td> | High/td> | DMU06/td>/tr> |
8/td> | Qa2/td> | Qa2/td> | Alluvium two/td> | Upper Holocene/td> | Unit Qa2 (mapped as post-Piney Creek alluvium by some researchers in the region) occupies the flood plains of the Cache la Poudre River and Big Thompson River (see Quaternary cross sections B-B’, C-C’, and D-D’). The unit is locally exposed in cut banks along both rivers and in some gravel pits. Unit Qa2 underlies the lower (younger) terrace in both river valleys; the higher (older) terrace overlies alluvium three, unit Qa3. The unit Qa2 fill-cut terrace is ~1.6 m above active streams, and unit Qa2 overlies an eroded surface on the valley-fill sediments of unit Qa3. As indicated from water well drillers’ logs (Colorado DWR, 2021) and geotechnical boreholes (CGS, 2021; Town of Windsor, 2021), where cross section B-B’ crosses the Cache la Poudre River valley, unit Qa2 thickness ranges from 2 to 5 m; where cross section C-C’ crosses the valley the thickness ranges from 2 to 4 m. Where cross section D-D’ crosses the Big Thompson River valley, unit Qa2 thickness ranges from 2 to 4 m. Bedding in cut banks was observed at only one location and was indistinct. Fresh unit Qa2 exposures at two gravel pits in the Big Thompson River valley were unbedded. At one of these gravel pits a unit Qa2 channel, with ~ 1 m of relief, is incised in gravel of underlying unit Qa3. In the Windsor quadrangle and elsewhere in the Colorado Piedmont, unit Qa2 can be readily distinguished from unit Qa3. Unit Qa2 consists mostly of dark-colored sand whereas unit Qa3 consists mostly of light-colored sandy gravel and gravelly sand (see Table 1 for unit colors). Unit Qa2 is moderately to strongly cohesive whereas unit Qa3 is weakly cohesive. The stratigraphic relationship of unit Qa2 overlying unit Qa3 is supported by radiocarbon ages of both units sampled at the same location in the St. Vrain Creek valley ~40 km to the southwest near Longmont, Colorado (Madole, 2016). Elsewhere in the piedmont the sequence is confirmed by visual observation, radiocarbon and optically stimulated luminescence (OSL) ages, and water well data. On the basis of deposit type and position in the landscape, unit Qa2 likely correlates with unit Qa2 of the adjacent Bracewell, Johnstown, and Greeley quadrangles (Palkovic, 2020; Palkovic and Morgan, 2017; and Keller and Morgan, 2020). In the Windsor quadrangle unit Qa2 is fine-grained and generally unbedded. It consists of silty clay or clayey silt with very fine to medium sand, very fine to medium sand, and coarse to very coarse sand, with the sand containing subordinate fines (clay and silt). Gravel content is minor at locations where it is found. Unit Qa2 grain size analyses in geotechnical reports indicate that in 22 analyses among six project sites (Table 3), unit Qa2 consists on average of 41 percent fines (clay and silt), 57 percent sand, and 2 percent gravel (Colorado Geological Survey, 2021; Town of Windsor, 2021). The finer-grained, lower-energy Qa2 sediments are interpreted to be lower-energy beds, probably overbank deposits, and these are preponderant in exposures. The coarse-grained sediments are interpreted to be higher-energy beds, probably former active channels, and these are subordinate in exposures. No visible secondary carbonate was observed, but locally the unit ranges from no effervescence to weak to violent effervescence. At a unit Qa2 exposure in the Coulson Excavating gravel pit in the Big Thompson River valley, radiocarbon analyses of were performed for material immediately overlying unit Qa3 (sample location WA019BC14B, 2.4 m below ground surface), and for material at the top of the exposure (sample location WA019BC14A, 0.3 m below ground surface). The lower sample yielded an age of 4,360 +/- 30 yr B.P. (calibrated), and the upper sample yielded an age of 3,590 +/- 30 B.P. (calibrated). Both ages are Late Holocene and are comparable to unit Qa2 radiocarbon ages in other Colorado Piedmont quadrangles mapped by the CGS. Unit Qa2 in the Windsor quadrangle is unlikely to be a potential source of sand and gravel because most of the deposit is dominantly fines or contains significant fines. Areas mapped as Qa2 are prone to flooding, as during the September 2013 flood events along the Front Range (see Mineral Resources, Groundwater Resources, and Geologic Hazards in Plate 2)./td> | 01-02-03/td> | DMUUnit1/td> | Qa2/td> | Qa2/td> | 254-246-136/td> | 215-176-158 601 gravel open/td> | DAS1/td> | Alluvial sediment, mostly fine-grained/td> | High/td> | DMU07/td>/tr> |
9/td> | Qa3/td> | Alluvium three/td> | Alluvium three/td> | Upper Pleistocene/td> | Unit Qa3 (mapped as Broadway Alluvium by some researchers in the region) is volumetrically the largest alluvial unit in the Cache la Poudre River valley and the Big Thompson River valley. Locally it is overlain by either unit Qa2 (alluvium two) or unit Qe (eolian sediment). A small area of unit Qa3 is exposed on the south side of the Big Thompson River valley, where a terrace of composed of this deposit extends northwest into the Windsor quadrangle from the Johnstown quadrangle; part of the terrace has been removed by a gravel pit. On the north side of the Cache la Poudre River valley, in the northeast quarter of the quadrangle, unit Qa3 forms a terrace several kilometers wide and extending across the quadrangle from northwest to southeast. This terrace is 4 to 5 m higher than the unit Qa2 terrace adjacent to the southwest; it is mapped by Colton (1976) in the geologic map of the Boulder-Fort Collins-Greeley area and by Palkovic (2020) in the geologic map of the Bracewell quadrangle (adjacent to the east). In the Fossil Creek valley east of Fossil Creek Reservoir, in the northwest corner of the quadrangle, unit Qa3 may underlie unit Qa, although there are no local water well data to support this possibility. In nearby quadrangles (e.g., Greeley and Valley View School) in the Colorado Piedmont, tributary valleys like that of Fossil Creek are buried valleys filled with unit Qa3 overlain by unit Qe or unit Qa (Keller and Morgan, 2020, 2022). Where cross section B-B’ crosses the Cache la Poudre River valley, unit Qa3 thickness from water well drillers’ logs (Colorado DWR, 2021) ranges from 3 to 8 m and depth to bedrock (Pierre Shale) ranges from 7 to 10 m; where cross section C-C’ crosses the valley the thickness ranges from 2 to 4 m and bedrock depth ranges from 4 to 9 m. Cross section B-B’ shows that the greatest thickness is in the center of the valley, and that the unit tapers to the southwest and northeast. Where cross section D-D’ crosses the Big Thompson River valley, unit Qa3 thickness ranges from 2 to 4 m and depth to bedrock ranges from 5 to 6 m. The Windsor region bedrock surface topography map of Shelton and Rogers (1975) shows that in the Windsor quadrangle the thalweg gradients of the Cache la Poudre River and Big Thompson River both are ~ 2 m per km to the southeast. In the part of the Colorado Piedmont north and northwest of Denver, unit Qa3 is areally and volumetrically the largest alluvium in the South Platte River valley and its major tributary valleys. This is evidenced by cross sections in Lindsey and others (2005); by CGS mapping in the Johnstown quadrangle adjoining the Windsor quadrangle to the south (Palkovic and Morgan, 2017), Bracewell quadrangle adjacent to the east (Palkovic, 2020), and Greeley quadrangle 20 km to the east (Keller and Morgan, 2020); and by U.S. Geological Survey geologic maps of the Masters quadrangle (Berry and others, 2015a) and Orchard quadrangle (Berry and others, 2015b), ~70 km to the southeast. According to Madole (2016), unit Qa3 alluvium consists of vertical sequences of superposed, longitudinal bars of sand and gravel deposited by braided streams. These sequences locally contain finer-grained layers that probably are overbank deposits. In the water-well driller’s logs used to assemble cross sections B-B’, C-C’, and D-D’, unit Qa3 consists of sandy gravel and gravelly sand (lower portion of unit), sand (lower or middle portions of unit), and clayey sand and sandy clay (upper portion of unit, and local interbeds in sandy gravel and gravelly sand). Unit Qa3 grain size analyses in geotechnical reports indicate that in 28 analyses among eight project sites (Table 3), unit Qa3 consists on average of 9 percent fines (clay and silt), 51 percent sand, and 40 percent gravel (Colorado Geological Survey, 2021; Town of Windsor, 2021). In gravel pit faces in the Big Thompson River valley, layers constituting unit Qa3 are ~20 cm to ~1 m thick, with sandy gravel and gravelly sand layers being interbedded with medium to coarse sand layers having low to moderate gravel content. Fines content in the sandy gravel and gravelly sand locally is sufficient to cause the material to be stiff and cohesive, but usually the gravel is only moderately cohesive. Fines content in the sand layers is low. Bedding at a scale of 10 to 20 cm is discernable but indistinct in the sandy gravel and gravelly sand layers; the sand layers locally have planar bedding at a scale of several millimeters and high-angle cross bedding at a scale of 1 to 2 cm. At the Coulson Excavating pit in the Big Thompson River valley, the uppermost unit Qa3 gravel is incised by a unit Qa2 channel having ~ 1 m of relief. Two samples were collected from unit Qa3 for optically stimulated luminescence (OSL) dating. Sample WA019AOSL, from the Coulson Excavating Co. gravel pit near the center of the Big Thompson River valley, was at the top of a gravel layer and near the contact with overlying unit Qa2. The sample yielded an age estimate of 1,035 +/- 50 yr (~0.1 ky). This age is in error because unit Qa3 here is overlain by unit Qa2 having radiocarbon ages of ~4.4 ky (bottom of unit Qa2) and ~3.6 ky (top of unit Qa2). The error may be due to exposure to light during sampling. Sample WA091COSL, from the Loveland Ready Mix Concrete, Inc. gravel pit, also near the center of the Big Thompson River valley, was in a laminated sand layer lying between two gravel layers. The sample yielded an age estimate of 16,285 +/- 9.8 yr (~16 ky), which is Late Holocene in age. In the Cache la Poudre River valley, in the terrace adjoining that valley on the northeast, and in the Big Thompson River valley, unit Qa3 is an important shallow alluvial aquifer. In both river valleys the deposit is historically and presently an important aggregate resource./td> | 01-02-04/td> | DMUUnit1/td> | Qa3/td> | Qa3/td> | 255-255-115/td> | 76-230-0 601 gravel open/td> | DAS1/td> | Alluvial sediment, mostly coarse-grained/td> | High/td> | DMU08/td>/tr> |
11/td> | Qg1/td> | Gravel deposit one/td> | Gravel deposit one/td> | Middle Pleistocene/td> | Two areas of unit Qg1 lie along the edge of the upland adjacent to and northeast of the Cache la Poudre River valley, in the northeast corner of the quadrangle. In the Timnath quadrangle, ~5 km northwest of the above areas, ~2 m of the gravel is exposed in the face of a small gravel pit. All the locations are at an elevation of ~6 m above the valley floor. Here the unit is mapped as Slocum Alluvium by Colton (1976). Access was denied to an excavated exposure (~2 m high) on the east side of Hollister Lake Drive, but from the road this exposure could be seen to be poorly sorted, moderately to well-rounded sandy gravel or gravelly sand, with clasts as large as small cobbles. The material is stiff and cohesive, many pebbles and cobbles have carbonate rinds, and there is a Bk secondary carbonate horizon (possibly Stage II) ~1 m thick. At this site the mapped extent of the unit is based upon the National Resource Conservation Service (NRCS) soils map of the quadrangle (Crabb, 1980), which shows the location to be underlain by Cascajo gravelly silt loam. Also on the edge of the upland, in the Timnath quadrangle and ~ 5 km to the northwest of the above locations, there is a fresh excavation face of ~3 m of unit Qg1. Here the unit is a very poorly sorted, rounded to well-rounded, very cohesive, granule to cobble gravel with a sand fraction. There are abundant carbonate rinds on the gravel clasts and the mass has pervasive Stage III to IV secondary carbonate development. /td> | 01-02-06/td> | DMUUnit1/td> | Qg1/td> | Qg1/td> | 255-255-215/td> | 115-255-223 ESRI 605 breccia open/td> | DAS1/td> | Alluvial sediment, mostly coarse-grained/td> | High/td> | DMU09/td>/tr> |
12/td> | Qg2/td> | Gravel deposit two/td> | Gravel deposit two/td> | Middle Pleistocene/td> | Unit Qg2 is poorly exposed in a road cut along Colorado Highway 54 in the southwest corner of the quadrangle, where ~0.6 m of the deposit overlies weathered Pierre Shale. The location is in the upland adjacent to and southwest of the Big Thompson River valley, ~1 km to the northeast, and is at an elevation of ~37 m above the valley floor. At this exposure the unit is mapped as Verdos Alluvium by Colton (1976). From 1.5 to 7 km southeast of this exposure there is a line of several unit Qg2 areas, trending parallel to the river valley, mapped both by Colton (1976) and Palkovic and Morgan (2017). In the Windsor quadrangle the deposit is mostly clay and silt with a subordinate gravel fraction ranging from pebbles to cobbles. Carbonate rinds are abundant on the clasts, and the mass has pervasive stage IV secondary carbonate development. The mapped extent of the unit is based upon the NRCS soils map of the quadrangle (Crabb, 1980), which shows the location to be underlain by Larim gravelly sandy loam./td> | 01-02-07/td> | DMUUnit1/td> | Qg2/td> | Qg2/td> | 255-255-215/td> | 0-112-255 ESRI 605 breccia open/td> | DAS1/td> | Alluvial sediment, mostly coarse-grained/td> | High/td> | DMU10/td>/tr> |
13/td> | None/td> | EOLIAN DEPOSITS/td> | EOLIAN DEPOSITS/td> | None/td> | None/td> | 01-03/td> | DMUHeading2/td> | None/td> | None/td> | None/td> | None/td> | DAS1/td> | None/td> | None/td> | DMU11/td>/tr> |
14/td> | Qe/td> | Eolian sediment/td> | Eolian sediment/td> | Lower Holocene and Upper Pleistocene/td> | Eolian sediment of unit Qe covers approximately three-quarters of the quadrangle, occupying the large upland area between the valleys of the Cache la Poudre River and Big Thompson River, and the smaller upland areas respectively northeast of and southwest of these valleys. It overlies the Pierre Shale in most of the upland between the river valleys, overlies the same unit along much of the swath of dissected slope on the southwest side of the Cache la Poudre River valley, overlies the unit Qa3 terrace adjacent to and northeast of the Cache la Poudre valley (cross section B-B’), and overlies the Fox Hills Sandstone in the area along the east quadrangle boundary and south of the Cache la Poudre River valley. Mapping of unit Qe in the Windsor quadrangle is supported by observations in construction excavations and road cuts, and by sample holes made during field work, grain size analyses from geotechnical reports (CGS, 2021; Town of Windsor, 2021), water-well drillers’ logs (Colorado DWR, 2021), and the NRCS soils map for the quadrangle (Crabb, 1980). As in other Colorado Piedmont quadrangles mapped by the CGS, unit Qe mostly occupies uplands, but per Madole (2016) is not associated with particular landforms and can be present over a broad range of elevations. On the basis of its position in the landscape, lithologic characteristics, and secondary calcium carbonate development, unit Qe in the Windsor quadrangle is similar to that in the Longmont (Madole, 2016), Milliken (Palkovic and others, 2018), Greeley (Keller and Morgan, 2020), Valley View School (Keller and Morgan, 2022) quadrangles and in other Colorado Piedmont quadrangles mapped by the CGS. In cross sections B-B’, C-C’, and D-D’, water-well drillers’ logs (Colorado DWR, 2021) and geotechnical boreholes (CGS, 2021; Town of Windsor, 2021) indicate that unit Qe thickness values range from 1 to 11 m. Most thickness values are in the range of 2 to 7 m and a small number of values fall between 1 and 2 m and between 7 and 11 m. In the Windsor quadrangle most unit Qe exposures are composed of silty clay or clayey silt, with a minor fraction of very fine to medium sand (estimated in the field to be from <1 percent to 5 percent), and very rare granules and small pebbles. A minority of exposures consist of fines and very fine sand, or very fine to very coarse sand with a subordinate fines fraction. Unit Qe grain size analyses in geotechnical reports show that in 73 analyses among seven project sites (Table 3), unit Qe consists on average of 81 percent fines (clay and silt), 19 percent sand, and no gravel (Town of Windsor, 2021). The fines fraction is usually sufficient to impart moderate cohesion although cohesion locally can be either weak or strong. Unit Qe is massive in the excavations where it is exposed (as is the case in excavations in other piedmont quadrangles mapped by the CGS). Colors are dark grayish brown, dark yellowish brown, brown, pale and very pale brown, and light yellowish brown. Most unit Qe exposures do not have visible secondary carbonate, but some have carbonate filaments and nodules 1 to 2 mm in thickness or diameter, respectively, and a few locations have scattered carbonate nodules from 3 to 9 cm in diameter. Only two locations have a continuous Bk horizon and Stage III secondary carbonate development. Most unit Qe exposures have strong to violent effervescence with dilute hydrochloric acid, a a few have only weak to moderate effervescence. In the Timnath quadrangle adjacent to the north, in a foundation excavation 0.6 km north of Kerns and 1.6 km north of the Windsor quadrangle, radiocarbon samples were taken from the top of the unit Qe exposure and the lowest exposed unit Qe. Sample WS028C14A (upper sample) yielded an age of 2,320 +/- 30 yr and sample WS028C14B (lower sample) yielded an age of 6,580 +/- 30 yr, both of which ages are Holocene. Within the Windsor quadrangle unit Qe is not a likely potential source of clean sand because of its relatively high content of fines. The area mapped as unit Qe locally may contain collapsible (hydrocompactive) soils or swelling soils./td> | 01-03-01/td> | DMUUnit1/td> | Qe/td> | Qe/td> | 254-249-194/td> | None/td> | DAS1/td> | Loess/td> | High/td> | DMU12/td>/tr> |
15/td> | None/td> | BEDROCK GEOLOGY/td> | BEDROCK GEOLOGY/td> | None/td> | Within the Windsor quadrangle, the only bedrock units mapped at the ground surface are the Fox Hills Sandstone and underlying Pierre Shale. Bedrock units are shown in cross section A-A’ (Plate 2). The description of the Fox Hills Sandstone is from Spencer (1986), who investigated this unit in detail in the Frederick and Erie quadrangles ~43 km south of the Windsor quadrangle. Descriptions of Pierre Shale members are adapted from Scott and Cobban (1965), supplemented by descriptions by Braddock and others (1988) in the geologic map of the Carter Lake Reservoir quadrangle, 26 km to the southwest, where these units are described in outcrop. Descriptions of older units are adapted from Braddock and others (1988). Thickness values for the Fox Hills Sandstone are from Spencer (1986) and cross section A-A’. Thickness values for older bedrock units are from cross section A-A', which was prepared with the aid of oil and gas well logs from the Energy and Carbon Management Commission (ECMC) (2021). /td> | 02/td> | DMUHeading1/td> | BEDROCK GEOLOGY/td> | None/td> | None/td> | None/td> | DAS1/td> | None/td> | None/td> | DMU13/td>/tr> |
16/td> | Kfh/td> | Fox Hills Sandstone/td> | Fox Hills Sandstone/td> | Upper Cretaceous/td> | Greenish-buff, fine- to coarse-grained quartzose sandstone; cross bedded in the lower part, grading upward to a light-yellow and white, massive, fine- to medium-grained sandstone. Total thickness is 46 to 91 m, of which the basal 12 to 27 m is exposed in the Windsor quadrangle. The contact of the Fox Hills Sandstone with the underlying Pierre Shale is from field mapping. Data for this contact are not included in the oil and gas well logs used for the cross section. /td> | 02-01/td> | DMUUnit1/td> | Kfh/td> | Kfh/td> | 234-242-213/td> | None/td> | DAS1/td> | Sandstone/td> | High/td> | DMU14/td>/tr> |
17/td> | None/td> | Pierre Shale/td> | Pierre Shale/td> | Upper Cretaceous/td> | Marine strata composed of dark-gray shale, siltstone, and fine-grained sandstone. Bentonite beds, rich in weathered volcanic ash, are common in its lower part and calcareous concretions are common throughout. The various members of the Pierre Shale contain index fossil ammonite species (Scott and Cobban, 1965)./td> | 02-02/td> | DMUUnit1/td> | None/td> | None/td> | None/td> | None/td> | DAS1/td> | None/td> | None/td> | DMU15/td>/tr> |
18/td> | Kpt/Kpu/td> | Uppermost transition member and upper shale member, undivided/td> | Uppermost transition member and upper shale member, undivided/td> | Upper Cretaceous/td> | These two members are combined in cross section A-A' because they are not distinguished in the oil and gas well data used to prepare the cross section. Both members are observed in outcrop ~28 km southwest of the Windsor quadrangle (Scott and Cobban, 1965). In general, the members consist of friable sandstone and soft shaly sandstone containing thin-bedded sandy shale and calcareous sandstone concretions. Combined thickness of the two members is ~1,060 m per Scott and Cobban (1965), but COGCC data indicate a thickness of 945 to 1189 m in cross section A-A’./td> | 02-02-01/td> | DMUUnit2/td> | Kpt/td> | Kpt/td> | 137-137-68/td> | None/td> | DAS1/td> | Sandstone/td> | High/td> | DMU16/td>/tr> |
19/td> | Kplr/td> | Larimer and Rocky Ridge Sandstone Members and intervening shale, undivided/td> | Larimer and Rocky Ridge Sandstone Members and intervening shale, undivided/td> | Upper Cretaceous/td> | The Larimer and Rocky Ridge Sandstone Members are well-indurated, light gray to light brown, medium-grained sandstones, composed mostly of quartz with minor feldspar and biotite. Combined thickness is 34 to 43 m in cross section A-A’./td> | 02-02-02/td> | DMUUnit2/td> | Kplr/td> | Kplr/td> | 153-235-128/td> | None/td> | DAS1/td> | Sandstone/td> | High/td> | DMU17/td>/tr> |
20/td> | Kpm/td> | Middle shale member/td> | Middle shale member/td> | Upper Cretaceous/td> | This unit consists of highly friable, greenish-gray claystone and sandy siltstone, and contains bentonite beds. Thickness is 116 to 213 m in cross section A-A’./td> | 02-02-03/td> | DMUUnit2/td> | Kpm/td> | Kpm/td> | 153-255-204/td> | None/td> | DAS1/td> | Mostly mudstone/td> | High/td> | DMU18/td>/tr> |
21/td> | Kph/td> | Hygiene Sandstone member/td> | Hygiene Sandstone member/td> | Upper Cretaceous/td> | The upper part of the unit is well-indurated, light-gray, fine- to medium-grained sandstone composed mostly of quartz, minor feldspar, and minor opaque minerals. The middle part of the unit is medium-gray siltstone; the lower part is a friable, gray concretionary sandstone. Thickness is 98 to 152 m in cross section A-A’./td> | 02-02-04/td> | DMUUnit2/td> | Kph/td> | Kph/td> | 128-255-0/td> | None/td> | DAS1/td> | Mostly sandstone/td> | High/td> | DMU19/td>/tr> |
22/td> | Kpl/td> | Lower shale member/td> | Lower shale member/td> | Upper Cretaceous/td> | Dark olive-gray shale and sandy shale containing limestone and ironstone concretions; bentonite beds are common in the lower part of the unit. Thickness is 671 to 762 m in cross section A-A’./td> | 02-02-05/td> | DMUUnit2/td> | Kpl/td> | Kpl/td> | 153-173-128/td> | None/td> | DAS1/td> | Mudstone/td> | High/td> | DMU20/td>/tr> |
23/td> | Kn/td> | Niobrara Formation, undivided/td> | Niobrara Formation, undivided/td> | Upper Cretaceous/td> | Very fissile, dark-gray shale containing thin (5 m) micritic limestone layers. Unit is an important oil and gas source in the quadrangle and in much of the Denver Basin (see Plate 2 and section on Mineral Resources, Groundwater Resources, and Geologic Hazards). Thickness is 88 to 125 m in cross section A-A’/td> | 02-03/td> | DMUUnit1/td> | Kn/td> | Kn/td> | 235-255-179/td> | None/td> | DAS1/td> | Mostly mudstone/td> | High/td> | DMU21/td>/tr> |
24/td> | Kcgg/td> | Colorado Group - Carlile Shale, Greenhorn Limestone, Graneros Shale, and Mowry Shale, undivided/td> | Colorado Group - Carlile Shale, Greenhorn Limestone, Graneros Shale, and Mowry Shale, undivided/td> | Upper Cretaceous/td> | Olive-gray silty claystone and sandy claystone; dark-gray limestone and olive-gray, calcareous, silty claystone and siltstone; dark-gray to grayish-black siltstone and claystone and siliceous shale. Combined thickness is 98 to 137 m in cross section A-A’./td> | 02-04/td> | DMUUnit1/td> | Kcgg/td> | Kcgg/td> | 204-255-48/td> | None/td> | DAS1/td> | Mostly mudstone/td> | High/td> | DMU22/td>/tr> |
25/td> | Kd/td> | Dakota Group: South Platte Formation and Lytle Formation, undivided/td> | Dakota Group: South Platte Formation and Lytle Formation, undivided/td> | Upper Cretaceous/td> | Unit consists of gray to light-brown, well-sorted, fine- to medium-grained sandstone; dark-gray carbonaceous shale; gray to light-brown, fine-grained sandstone; and gray to light-brown, coarse-grained, conglomeratic sandstone. Combined thickness is 107 m in the one well completely penetrating this unit in cross section A-A’./td> | 02-05/td> | DMUUnit1/td> | Kd/td> | Kd/td> | 205-205-102/td> | None/td> | DAS1/td> | Sandstone/td> | High/td> | DMU23/td>/tr> |
26/td> | gp/td> | gravel pit/td> | gravel pit/td> | Upper Holocene/td> | Sand or gravel pit/td> | 03/td> | DMUHeading1/td> | gp/td> | gp/td> | None/td> | diagonal hatch 3 pt 210-210-210 + 0.4 pt 25-25-147/td> | DAS1/td> | "Made" or human-engineered land/td> | High/td> | DMU25/td>/tr> |
27/td> | water/td> | water/td> | water/td> | Holocene/td> | water/td> | 04/td> | DMUHeading1/td> | water/td> | water/td> | 151-219-242/td> | None/td> | DAS1/td> | Water or ice/td> | High/td> | DMU26/td>/tr> |
28/td> | No data/td> | No data/td> | No data/td> | None/td> | None/td> | 05/td> | DMUHeading1/td> | No data/td> | No data/td> | None/td> | None/td> | DAS1/td> | Unmapped area/td> | High/td> | DMU27/td>/tr> |
OBJECTID | Term | Definition | DefinitionSourceID | Glossary_ID | /tr>/thead>
---|---|---|---|---|
29/td> | 1 SD/td> | 1 standard deviation. 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./td> | GEODICT1/td> | GLO01/td>/tr> |
12/td> | AGE/td> | 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/td> | DICT1/td> | GLO02/td>/tr> |
14/td> | Bedding/td> | 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./td> | GEODICT1/td> | GLO03/td>/tr> |
15/td> | Bedrock Section/td> | A graphic representation of the intersection of the geological bodies in the subsurface with a vertical plane of a certain orientation showing relationships in the bedrock/td> | GEODICT1/td> | GLO04/td>/tr> |
13/td> | BOREHOLE/td> | A hole that is drilled into the earth, as in exploratory well drilling or in building construction; A hole bored into the ground to collect samples for analysis or to extract oil or water/td> | GEODICT1/td> | GLO05/td>/tr> |
11/td> | boundary/td> | The edge or border of something, or the part near it/td> | DICT1/td> | GLO06/td>/tr> |
16/td> | C14/td> | Carbon-14, or radiocarbon, is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby and colleagues to date archaeological, geological and hydrogeological samples/td> | GEODICT1/td> | GLO07/td>/tr> |
30/td> | cal BP/td> | Age unit for C14 geochronology samples/td> | GEODICT1/td> | GLO08/td>/tr> |
1/td> | certain/td> | 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./td> | FGDC-STD-013-2006/td> | GLO09/td>/tr> |
5/td> | contact/td> | A geological contact is a boundary which separates one rock body from another. A contact can be formed during deposition, by the intrusion of magma, or through faulting or other deformation of rock beds that brings distinct rock bodies into contact./td> | GEODICT1/td> | GLO10/td>/tr> |
17/td> | DEPOSIT TYPE/td> | Groupings for surficial units in the CMU/td> | DAS1/td> | GLO11/td>/tr> |
7/td> | DMUHeading1/td> | GeMS hierarchy formatting term/td> | GeMS1/td> | GLO12/td>/tr> |
8/td> | DMUHeading2/td> | GeMS hierarchy formatting term/td> | GeMS1/td> | GLO13/td>/tr> |
9/td> | DMUUnit1/td> | GeMS hierarchy formatting term/td> | GeMS1/td> | GLO14/td>/tr> |
10/td> | DMUUnit2/td> | GeMS hierarchy formatting term/td> | GeMS1/td> | GLO15/td>/tr> |
18/td> | DWR/td> | Division of Water Resources/td> | DWR1/td> | GLO16/td>/tr> |
19/td> | DWR Well/td> | Division of Water Resources water well: Wells (bore holes) that penetrate artesian aquifers. Water will rise up the well casing to the pressure level of the aquifer. Artesian flow describes the natural flow to the surface of water from confined aquifers./td> | DWR1/td> | GLO17/td>/tr> |
27/td> | fault/td> | 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./td> | GEODICT1/td> | GLO19/td>/tr> |
20/td> | GEOTECH/td> | 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./td> | GEODICT1/td> | GLO20/td>/tr> |
21/td> | Geotech Well/td> | A well used as part of the investigation process carried out on site prior to construction. /td> | GEODICT1/td> | GLO21/td>/tr> |
28/td> | High/td> | unusual or considerable in degree, power, intensity, etc. /td> | DICT1/td> | GLO22/td>/tr> |
3/td> | HIGH-ANGLE FAULT/td> | A fault is a fracture or zone of fractures between two blocks of rock. Faults allow the blocks to move relative to each other. High-angle indicates the relative movement of the blocks on either side of the fault/td> | GEODICT1/td> | GLO23/td>/tr> |
23/td> | Oil and Gas Well/td> | An oil well is a boring in the Earth that is designed to bring petroleum oil hydrocarbons to the surface. Usually some natural gas is released as associated petroleum gas along with the oil. A well that is designed to produce only gas may be termed a gas well./td> | GEODICT1/td> | GLO25/td>/tr> |
22/td> | OSL/td> | 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./td> | GEODICT1/td> | GLO26/td>/tr> |
24/td> | Quaternary Section/td> | A graphic representation of the intersection of the geological bodies in the subsurface with a vertical plane of a certain orientation showing relationships in the Quaternary units/td> | GEODICT1/td> | GLO27/td>/tr> |
25/td> | Syncline/td> | A trough-shaped fold with youngest strata in the center/td> | GEODICT1/td> | GLO28/td>/tr> |
6/td> | water/td> | a colorless, transparent, odorless liquid that forms the seas, lakes, rivers, and rain and is the basis of the fluids of living organisms. /td> | DICT1/td> | GLO29/td>/tr> |
26/td> | Water/td> | a colorless, transparent, odorless liquid that forms the seas, lakes, rivers, and rain and is the basis of the fluids of living organisms. /td> | DICT1/td> | GLO30/td>/tr> |
4/td> | WFZ/td> | A fault is a fracture or zone of fractures between two blocks of rock. Faults allow the blocks to move relative to each other. In a strike slip fault system the movement runs parallel to the strike of the fault under consideration. A wrench fault, also called lateral fault, has a fault surface which is vertical to subvertical./td> | GEODICT1/td> | GLO31/td>/tr> |
32/td> | yr/td> | the time taken by the earth to make one revolution around the sun/td> | GEODICT1/td> | GLO32/td>/tr> |
OBJECTID | QuaternaryUnit | NumOfSamples | NumOfSites | GravelAvg | GravelRange | SandAvg | SandRange | FinesAvg | FinesRange | /tr>/thead>
---|---|---|---|---|---|---|---|---|---|
1/td> | Eolian sediment (Qe)/td> | 73/td> | 7/td> | NA3/td> | NA3/td> | 19/td> | 15-49/td> | 81/td> | 47-96/td>/tr> |
2/td> | Alluvium two (Qa2)/td> | 22/td> | 6/td> | 2/td> | 0-10/td> | 57/td> | 24-92/td> | 41/td> | 2-72/td>/tr> |
3/td> | Alluvium three (Qa3)/td> | 28/td> | 8/td> | 40/td> | 12-64/td> | 51/td> | 32-82/td> | 9/td> | 3-28/td>/tr> |
OBJECTID | MapProperty | MapPropertyValue | MiscellaneousMapInformation_ID | /tr>/thead>
---|---|---|---|
1/td> | GEOLOGIC HISTORY AND STRUCTURE PARAGRAPHS 1, 2, 3, 4, 5/td> | The Windsor quadrangle lies in the northern part of the Colorado Piedmont, where topographic relief is relatively low; the quadrangle has 94 m difference between its lowest and highest elevations. The quadrangle contains some continuous, elongate outcrop areas of weathered bedrock, notably along the dissected southwest side of the Cache la Poudre River valley (geologic map, Plate 1). There are upland locations where weathered bedrock lies just below a thin residual soil cover, as in the area northeast of the intersection of Interstate Highway 25 and Colorado Highway 34. Fresh bedrock was observed only in the lower faces of gravel pits in the Big Thompson River valley. Unconsolidated Quaternary deposits cover most of the quadrangle, and the few natural exposures of these surficial units are along river cut banks. Topographically, most of the Windsor quadrangle consists of a broad, northwest-to-southeast-trending swath of upland bounded on the southwest and northeast by the valleys of the Big Thompson River and Cache la Poudre River, respectively. The quadrangle is drained by these two southeast-flowing rivers and their tributary streams, and their valleys are ~1 km and ~5 km wide, respectively. The present-day landscape of the Colorado Piedmont results from the downcutting and geomorphic evolution of the South Platte River and Arkansas River drainage basins mainly during late Neogene and Quaternary time. This began with removal of Paleogene and Neogene rocks and sediments that once covered Upper Cretaceous strata in the basins (Madole, 1991). The predominant Quaternary deposits in the piedmont, including those in the Windsor quadrangle and surrounding area, are fluvial sediments of the South Platte River and its major tributaries, and eolian sediments deflated from alluvium in the stream valleys and from upwind bedrock exposures (Madole, 1991; 2016). The Windsor quadrangle is in the central part of the Greeley Arch, a structural saddle separating the Denver Basin to the south from the Cheyenne Basin to the north (Dechesne and others, 2011). Cross section A-A’ (Plate 2) indicates that bedrock strata in the quadrangle are essentially flat-lying, except between wells Wicked #1 and Jeffers #2 where the local dip is ~5° east. This eastward dip may be due to Laramide deformation along the west side of the Denver Basin during Late Cretaceous and Paleogene time, as indicated in the Figure 5 cross section of Dechesne and others (2011). The Windsor quadrangle is ~110 km north of this cross section, but is on the west margin of the basin, as is the west side of the cross section where strata are shown as eastward-dipping. In Windsor quadrangle outcrops of Pierre Shale, located at the intersection of Colorado Highway 392 and Larimer County Road 3 (geologic map, Plate 1), two of four attitude measurements (strike 10°, dip 8° east; strike 175°, dip 9° east) are in accord with a north-south regional strike along the western side of the Denver Basin and a gentle eastward dip due to Laramide deformation. Two measurements (strike 40°, dip 9° southeast; strike 47°, dip 5° southeast) are not in accord with this setting. Their locations lie ~0.4 km east of the surface trace of the Windsor wrench fault zone (geologic map, Plate 1) and it is possible that the two discordant attitudes resulted from deformation associated with fault movement along the zone. The Windsor wrench fault zone trends south-southwest to north-northeast across the western side of the quadrangle, as presented in a structure map of central Denver Basin fault zones in Weimer (1996) and included in the geologic map of the present report (Plate 1). As shown in cross section A-A’ (Plate 2), the surface trace of the zone on the geologic map is confirmed by a fault inferred to lie between oil and gas wells Kness #1 and Encore #1C 12HZ. This fault is downthrown 140 m to the east, in accord with the Windsor wrench fault zone being downthrown to the east (Weimer, 1996). Right-lateral movement along this oblique-slip fault zone occurred during Cretaceous time and was intermittent from 110 to 65 Ma (Weimer, 1996), an interval that includes the beginning of the Laramide orogeny. Cross section A-A’ also intersects two high-angle faults not presented in Weimer (1996) but inferred from the displacements observed between oil and gas wells. Data are insufficient to indicate if the faults are normal or reverse, both are downthrown to the west, and their displacements are 64 m (west fault) and 68 m (east fault). The trend of the syncline of Weimer (1996) (geologic map, Plate 1) parallels the trend of the Windsor wrench fault zone and runs through the City of Windsor. In cross section A-A’ the syncline is confirmed by oil and gas well data. All the bedrock units shown in cross section A-A’ are Cretaceous formations deposited in the Western Interior Seaway, which at its maximum extent reached from the Arctic Ocean to the Gulf of Mexico and divided the North American continent. From Middle Jurassic into Late Cretaceous time the seaway occupied the Western Interior Foreland Basin adjacent to the east of the Cordilleran Orogenic Belt. The basin and orogenic belt were formed as North America drifted westward away from Europe, and the Pacific (Panthalassan) oceanic crust was subducted beneath the North America Plate. The Laramide orogeny during Late Cretaceous and Paleogene time, along with a drop in eustatic sea level, caused the Western Interior Seaway to retreat from the interior of North America (Slattery and others, 2013). The Late Cretaceous Fox Hills Sandstone is the youngest of the marine deposits present in the Windsor quadrangle and represents near-shore and beach environments on the west side of the retreating seaway. The Late Cretaceous Laramie Formation, youngest of the Cretaceous units in the Colorado Piedmont, overlies the Fox Hills Sandstone in nearby quadrangles (notably Frederick and Erie, ~43 km to the south), but in the Windsor quadrangle this unit has presumably been lost to erosion. The Laramie Formation consists of terrestrial sediments deposited inland from the seaway. During Pliocene time in the Colorado Piedmont, major streams incised rocks and sediments of Neogene and Paleogene age as well as Upper Cretaceous sedimentary rocks; no rocks or sediments of Paleogene or Neogene age remain in the Windsor quadrangle. The incision resulted in the development of the South Platte River and its major and minor tributaries. Some of these tributaries, however, especially minor ones, may have formed later during the Quaternary. The stream network within and near the Windsor quadrangle includes the Big Thompson River and the Cache la Poudre River, both of which are southeast-flowing tributaries to the east-flowing South Platte River. In the northern Colorado Piedmont there are many buried paleovalleys in minor tributaries to the major South Platte River tributaries, and the paleovalleys are filled with alluvium three (Qa3) and covered with eolian sediment (Qe) (see, for example, the paleovalleys in the Greeley quadrangle; Keller and Morgan, 2020). The paleovalleys are associated with present-day minor drainages but locally have very little surface expression. They are more easily discernable in lidar imagery than in topographic maps or even by field observation, but some of the paleovalleys can be traced by concentrations of water wells completed in the valley-filling alluvium. The portion of the Fossil Creek valley downstream from Fossil Creek Reservoir, in the northwest corner of the Windsor quadrangle, appears in lidar imagery to be such a paleovalley, but there are no supporting water well data at this location. /td> | MMI01/td>/tr> |
2/td> | GEOLOGIC HISTORY AND STRUCTURE PARAGRAPHS 6, 7, 8, 9, 10/td> | Within the Windsor quadrangle the Quaternary alluvial map units were deposited by the Cache la Poudre River and Big Thompson River and their tributaries, or (at a few places) possibly by rivers ancestral to these two streams. From oldest to youngest the alluvial deposits are unit Qg2 (gravel two, also called Verdos Alluvium), unit Qg1 (gravel one, also called Slocum Alluvium), unit Qa3 (alluvium three, also called Broadway Alluvium), unit Qa2 (alluvium three, also called post-Piney Creek alluvium), and unit Qa (alluvium, undivided). Unit Qa connects laterally with unit Qa2 and the two probably are coeval. The positions of the above units in the landscape and relative to each other are shown in cross sections B-B’, C-C’, and D-D’. The Quaternary history of the Windsor quadrangle and environs begins with deposition of Early and Middle Pleistocene stream and alluvial-fan gravels, termed “old alluvium” by Lindsey and others (2005). These deposits include the Late Pliocene Nussbaum Alluvium and (from older to younger) the Rocky Flats, Verdos, and Slocum alluviums. The Slocum Alluvium and Verdos Alluvium, gravel one (Qg1) and gravel two (Qg2) respectively in Colorado Geological Survey nomenclature, are present in the Windsor quadrangle. From Early to Middle Pleistocene time there were periods of incision as well as periods of alluvial deposition, and, probably, eolian deposition. The incision and lateral cutting of surrounding, fine-grained, less-resistant alluvial deposits and bedrock left isolated remnants of the older, more resistant “old alluvium” at higher elevations. Lindsey and others (2005) recognize occurrences of dissected alluvial fans and terrace gravels of Middle Pleistocene age extending as far as 5 km east of Fort Lupton (~43 km south of the Windsor quadrangle). These deposits include the Rocky Flats and Verdos alluviums. The Rocky Flats Alluvium is not mapped in the Windsor quadrangle but has been mapped elsewhere in the northern Colorado Piedmont; it ranges in estimated age from ~400 ka to 2 Ma (Middle to Early Pleistocene; Riihimaki and others, 2006). Verdos Alluvium (unit Qg2) is mapped in the southeast corner of the Windsor quadrangle by Colton (1976) and during the field work for the present study, in the Johnstown quadrangle (adjacent to the south) by Palkovic and Morgan (2017), and in the Greeley quadrangle (~20 km to the east) (Keller and Morgan, 2020). Its estimated age ranges from between 410 and 475 ky and up to ~631 ky (see unit Qg2 section in Description of Map Units section, Greeley quadrangle, in Keller and Morgan, 2020). As summarized in Berry and others (2019), the maximum age for the Verdos Alluvium is constrained by the underlying Lava Creek B ash, erupted from the Yellowstone Plateau volcanic field at ~631 ka (Matthews and others, 2015, cited in Berry and others, 2019). The ash is present in Verdos Alluvium at sites along the South Platte River northeast of Fort Morgan; although at many sites the ash is likely to be reworked. The ash is present within and at the top of Verdos Alluvium as well as at the base. The age assignments of these Early and Middle Pleistocene Colorado Piedmont alluvial deposits are based chiefly upon the following: height above present stream level near the east side of the Front Range hogback belt; tentative correlation with marine oxygen isotope stages; and assumption of a nonlinear rate of stream incision since the deposition of the Lava Creek B tephra at ~631 ka. The above age estimate of the Verdos Alluvium is based chiefly on its stratigraphic relationship with Lava Creek B tephra but also on soil carbonate morphology in the greater Denver area (Kellogg and others, 2008); there are also younger age estimates for this alluvium. In the Windsor quadrangle unit Qg2 is located near the Big Thompson River, and in the Johnstown quadrangle (adjacent to the south) areas of unit Qg2 lie in a swath roughly parallel with the trend of the river. This unit may have been deposited by an ancestral Big Thompson River. The Slocum alluvium (unit Qg1) is mapped in the northeast corner of the Windsor quadrangle by Colton (1976) and during the field work for the present study. In the Windsor quadrangle and Timnath quadrangle (adjacent to the north), areas of unit Qg1 (mapped as Qs, or Slocum alluvium, by Colton, 1976) lie in a swath along the northeast side of the Cache la Poudre River Valley. This unit may have been deposited by an ancestral Cache la Poudre River. The age of the Slocum Alluvium is 220 to 390 ky (Kellogg and others, 2008). After the deposition of unit Qg2 (Verdos Alluvium), at some time during the period from ~631 ka to 410 ka, an episode of incision removed most of this unit from the northern Colorado Piedmont. Unit Qg1 (Slocum Alluvium) was deposited during a subsequent episode of aggradation, at some time during the period from 390 to 220 ka (the age range of Slocum Alluvium given in Kellogg and others, 2008). Another incision episode then removed most of unit Qg1 from the landscape. It is possible, but not proven, that Louviers Alluvium (unit Qa4 in Colorado Geological survey nomenclature) could have been deposited in the valleys of the Cache la Poudre River and Big Thompson River during an aggradation period from 170 to 120 ka (the age range of Louviers Alluvium given in Kellogg and others, 2008) and now underlies unit Qa3 (Broadway Alluvium). In the Gowanda quadrangle (~28 km to the south) Louviers Alluvium underlies unit Qa3 in the valley of St. Vrain Creek and has an age of ~151 ky (Keller and others, 2019). (Note that in the Plate 2 Quaternary cross sections all alluvium below unit Qa2 and above bedrock is shown as being unit Qa3.) Later, unit Qa3 filled the valleys of the Cache la Poudre River and Big Thompson River during an aggradation episode from 30 to 12 ka (the age range of Broadway Alluvium given in Kellogg and others, 2008). During the period from ~10 to ~4 ka unit Qe (eolian sediment) was deposited in much of Windsor quadrangle and other quadrangles in the region (see eolian sediment radiocarbon ages in Table 2 of this report; Keller and Morgan, 2018; Keller and others, 2019; and Keller and Morgan, 2020). The older ages in the above period fall within an early Holocene episode of eastern Colorado loess deposition spanning approximately 11 to 9 ka (Muhs and others, 1999). Unit Qe in the Windsor quadrangle lacks sufficient silt to be termed loess or sandy loess, but it may be coeval at least in part with loess deposition and may have derived its sand content from unit Qa3 alluvium exposed along the Cache la Poudre River. Unit Qe was deposited on the unit Qa3 terrace on the northeast side of the Cache la Poudre River valley and on most of the Windsor quadrangle upland. In the valleys of the Cache la Poudre River and Big Thompson River, unit Qa3 was incised and then, during the period after ~4 ka, the incision was partially filled with unit Qa2 (post-Piney Creek) alluvium. In the Cache la Poudre River valley both the older unit Qa3 terrace and the younger unit Qa2 terrace are prominent in lidar imagery. The area of unit Qe overlying the Qa3 terrace along the Cache la Poudre River also was incised during this time. It was probably after ~4 ka that unit Qa was deposited in drainages tributary to the two rivers, contemporary with deposition of unit Qa2. Unit Qa2 in the river valleys then was partially incised and the incisions subsequently partially filled by unit Qa1. Modify as necessary when new Qa2 C14 and Qa3 OSL ages are received./td> | MMI02/td>/tr> |
3/td> | GEOLOGIC HISTORY AND STRUCTURE PARAGRAPHS 11/td> | From Late Pleistocene to Late Holocene time, eolian sand (unit Qes) was deposited over much of the northeastern plains of Colorado and nearly as far west as Boulder (Madole and others, 2005), but is not present in the Windsor quadrangle./td> | MMI03/td>/tr> |
4/td> | MINERAL RESOURCES, GROUNDWATER RESOURCES, AND GEOLOGIC HAZARDS/td> | Within the Windsor quadrangle there are four active construction permits (for aggregate production) in the valley of the Cache la Poudre River and three in the valley of the Big Thompson River; the quadrangle has no other active or inactive construction or mining permits (Colorado Division of Reclamation and Mine Safety [DRMS] AUGER interactive map, 2022). Of the total seven permits, five are for sand and gravel extraction and two are for gravel only; five permits are in Larimer County and two are in Weld County. The pits at all seven locations are discernable on the lidar image for the quadrangle and all are excavated in the interbedded alluvial sand and gravel of unit Qa3. Two of the pits (Coulson Excavating Co. and Loveland Ready Mix Concrete, Inc.) in the Big Thompson River valley are locations for the unit Qa3 optically stimulated luminescence (OSL) samples and ages presented in this report (see Description of Map Units in Plate 1 and Table 2 in Plate 2). All seven permit sites lie in portions of the river valleys mapped by Schwochow and others (1974) as flood-plain and valley-fill deposits of relatively clean and sound gravel. For the years 2020 and 2021 the annual aggregate production in Larimer County was ~1.3 million and ~1.2 million metric tons, respectively (Larimer County Assessor's Office, oral commun., 2022). For the same years the annual aggregate production in Weld County was ~14.7 million and 15.2 million metric tons, respectively (Weld County Assessor's Office, oral commun., 2021). The Windsor quadrangle lies on the northwest margin of the Wattenberg field, a prolific oil and gas producing area located mostly in Weld County and Adams County but impinging a little into Larimer County. As of summer 2021, the Windsor quadrangle was an active area for hydrocarbon production. Oil and gas infrastructure is prominent in the south part of the quadrangle in the rural upland between the valleys of the Big Thompson River and Cache la Poudre River. As of 2021 the Wattenberg field was the fourth-largest oil field and ninth-largest natural gas field in the U.S. (U.S. Energy Information Administration, 2021). Production in the Wattenberg field is principally from the Niobrara Formation but also from the Colorado Group and Dakota Group. In 2021 the field produced ~117 million barrels of oil and ~958 billion MCF (thousand cubic ft) of natural gas (Colorado Oil and Gas Conservation Commission, 2022). Of the 256 water wells in the Windsor quadrangle, all but 32 are completed in unit Qa3 alluvium in the valleys of the Big Thompson River and Cache la Poudre River. The alluvium consists of interbedded layers of sand, gravel, and clay and is underlain by the Pierre Shale. In the Colorado Piedmont this alluvium is found along the valleys of the South Platte River and its major tributaries, as well as in minor tributary paleovalleys (buried valleys) to these streams. In cross sections B-B’, C-C’, and D-D’ the thickness of the unit Qa3 aquifer ranges between 2 and 8 m. The upland wells of the Windsor quadrangle are completed in eolian sediment (unit Qe) and more rarely in the Pierre Shale; these wells are as deep as 14 m. The uppermost bedrock aquifer in the northern Colorado Piedmont is the Laramie-Fox Hills aquifer, described in Topper and others (2003). The Laramie Formation is absent in the Windsor quadrangle and there is only a small and relatively thin area of Fox Hills Sandstone present (along the east boundary). The Laramie-Fox Hills aquifer thus is not an important groundwater resource in the quadrangle. During the catastrophic September 2013 regional flood events along the Colorado Front Range there were some fatalities, large-scale damage to property and infrastructure, and some adverse environmental effects. In the Windsor quadrangle, in the valleys of the Cache la Poudre River and Big Thompson River, flood waters covered much of the area mapped as alluvium one (unit Qa1) and alluvium two (unit Qa2) (Town of Windsor, 2013; Coloradoan, 2019). In the Windsor quadrangle the areas of units Qa1 and Qa2 in both river valleys are designated as Federal Emergency Management Agency 100-yr flood zones by Larimer County (Larimer County Land Information Locator, 2022) and Weld County (Weld County Property Portal, 2022). Eolian sediment (unit Qe) locally may, owing to hydrocompaction, be susceptible to collapse when under load and in a wet or saturated condition. Soil engineers refer to these deposits as collapsible soils. The fine-grained fractions (silt and especially clay) of these deposits give them relatively high compressive strength and shear strength under dry conditions. When wet or saturated and under load, however, the fine-grained particles in these deposits can be displaced into a denser configuration such that the void space between particles is reduced. Compaction and associated decrease in volume can cause settlement at and near the ground surface, potentially resulting in damage to any overlying structures and (or) infrastructure (White and Greenman, 2008). Near Greeley in June 2014 there was an apparent wastewater injection-induced earthquake of moment-magnitude (Mw) 3.2 and Modified Mercalli intensity IV, great enough to be felt throughout the Front Range (Yeck and others, 2016). The epicenter for the earthquake was in a historically aseismic part of Colorado, ~4 km northeast of the east end of the City of Greeley/Weld County Municipal airport, and ~2.5 km northeast of a high-rate oilfield injection well. The well was being used for wastewater disposal into the Pennsylvanian-Permian Fountain Formation overlying the Precambrian crystalline basement. The monthly rate of oilfield wastewater injection in Weld County had increased significantly over the period of 2010 to 2014. Suspecting that the nearby injection well had caused the earthquake, the Colorado Oil and Gas Conservation Commission temporarily halted injection activity. The University of Colorado, with support from other agencies, then rapidly installed a local seismic monitoring network. The bottom of the well was cemented to prevent hydraulic communication between the injection zone and the basement rocks, and injection then was resumed at a lower rate. During the following 16 months (through about October 2015) there were no earthquakes greater than Mw 1.5 associated with the injection well (Yeck and others, 2016). During the period from October 2015 through February 2020 there were 21 earthquakes in the Greeley quadrangle. Half of the earthquakes ranged from local Richter magnitude (Ml) 1 to 1.9 and half ranged from 2.1 to 3 Ml (U.S. Geological Survey Online Earthquake Catalog, February 2020, cited in Keller and Morgan, 2020). (Local Richter magnitude and moment-magnitude are nearly equivalent for small earthquakes.) The local seismicity is believed to be induced by continuing injection-well operations, although the cause of these earthquakes is still a subject of debate. The Town of Windsor lies ~20 km west of the June 2014 earthquake epicenter in the Greeley quadrangle. For the period from the beginning of June 2014 through the end of April 2022 there was no recorded seismic activity in the Windsor quadrangle (U.S. Geological Survey Online Earthquake Catalog, May 2022)./td> | MMI04/td>/tr> |
5/td> | REFERENCES 1/td> | Berry, M.E., Slate, J.L., Paces, J.B., Hanson, P.R., and Brandt, T.R., 2015a, Geologic map of the Masters 7.5’ quadrangle, Weld and Morgan Counties, Colorado, U.S. Geological Survey Special Investigations Map 3344, scale 1:24,000 Berry, M.E., Slate, J.L., Hanson, P.R., and Brandt, T.R., 2015b, Geologic map of the Orchard 7.5’ quadrangle, Morgan County, Colorado, U.S. Geological Survey Special Investigations Map 3331, scale 1:24,000 Berry, M.E., Slate, J.L., and Taylor, E.M., 2019, Pleistocene and Holocene landscape development of the South Platte River corridor, northeastern Colorado: U.S. Geological Survey Scientific Investigations Report 2019–5020, 22 p. [also available at https://pubs.er.usgs.gov/search?q= Pleistocene+and+Holocene+landscape+development+of+the+South+Platte+River+corridor%2C+ northeastern+Colorado]. Braddock, W.A., Nutalaya, P., and Colton, R.B., 1988, Geologic map of the Carter Lake Reservoir quadrangle, Boulder and Larimer Counties, Colorado: U.S. Geological Survey Geologic Quadrangle Map GQ-1628, scale 1:24,000 [also available at https://pubs.er.usgs.gov/publication/ gq1628]. Colorado Department of Natural Resources, Division of Water Resources, 2021, Drillers' logs incorporated with water-well permits [available at https://gis.colorado.gov/dnrviewer/Index.html? viewer=mapviewer]. Colorado Division of Reclamation, Mining, and Safety, 2020, Reports and Data, GIS Data, AUGER (map of mine permits) [available at https://gis.colorado.gov/dnrviewer/Index.html? viewer=drms]. Colorado Geological Survey, 2020, Geotechnical boring logs from the Colorado Geological Survey ongoing land use review program: geotechnical logs incorporated with various unpublished site investigation reports, on file at Colorado State Archives, Denver, Colorado. Colorado Oil and Gas Conservation Commission, 2021, Oil and gas production data [available at https://cogcc.state.co.us/data.html#/cogis]. Coloradoan, 2019, See the destruction caused by September 2013 flood: online article, July 19, 2019; https://www.coloradoan.com/picture-gallery/news/local/fort-collins/2018/09/11/photos-impact-september-2013-flood-northern-colorado/1270078002/ Colton, R.B., 1976, Geologic map of the Boulder-Fort Collins-Greeley area, Colorado: U.S. Geological Survey Geologic Investigations Series I-855-G, scale 1:100,000 [also available at https://pubs.usgs.gov/imap/855/G/i-855-g_v1.1.pdf]. Crabb, J.A., 1980, Soil survey of Weld County, Colorado, southern part: U.S. Department of Agriculture, U.S. Soil Conservation Service, Washington, DC, 135 p., 35 maps, scale 1:24,000. Dechesne, Marieke, Raynolds, R.G., Barkmann, P.E., and Johnson, K.R., 2011, Notes on the Denver Basin geologic maps - bedrock geology, structure, and isopach maps of the Upper Cretaceous to Paleogene strata between Greeley and Colorado Springs, Colorado: Colorado Geological Survey Open-File Report 11-01, 35 p. [also available at https://coloradogeologicalsurvey.org/publications/geologic-map-stratigraphy-notes-denver-basin-colorado/]. /td> | MMI05/td>/tr> |
6/td> | REFERENCES 2/td> | 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.
International Union of Geological Sciences, International Commission on Stratigraphy, 2020, International Chronostratigraphic Chart, v 2020/01.
Keller, S.M., and Morgan, M.L., 2018, Geologic map of the Frederick quadrangle, Weld and Boulder Counties, Colorado: Colorado Geological Survey Open-File Report 18-01, scale 1:24,000 [also available at https://coloradogeologicalsurvey.org/publications/geologic-map-frederick-quadrangle-weld-broomfield-colorado/].
Keller, S.M., and Morgan, M.L., 2020, Geologic map of the Greeley quadrangle, Weld County, Colorado: Colorado Geological Survey Open-File Report 20-05, scale 1:24,000 [also available at https://coloradogeologicalsurvey.org/publications/geologic-map-greeley-quadrangle-weld-colorado/].
Keller, S.M., and Morgan, M.L., 2022, Geologic map of the Valley View School quadrangle, Weld County, Colorado: Colorado Geological Survey Open-File Report xx-yy, scale 1:24,000 [also available at zz] [in publication?]
Keller, S.M., Lindsey, K.O., and Morgan, M.L., 2019, Geologic map of the Gowanda quadrangle, Weld County, Colorado: Colorado Geological Survey Open-File Report 19-02, scale 1:24,000.
Kellogg, K.S., Shroba, R.R., Bryant, Bruce, and Premo, W.R., 2008, Geologic map of the Denver
West 30′ × 60′ quadrangle, north-central Colorado: U.S. Geological Survey Scientific
Investigations Map SIM–3000, scale 1:100,000, 48 p. pamphlet [also available at
https://doi.org/10.3133/sim3000].
Larimer County, Colorado, 2022, Larimer County Land Information Locator: Online interactive map; https://maps1.larimer.org/gvh/?Viewer=LIL&run=Theme&theme=Land%20Information&run=Parcel&parcel=
Lindsey, D.A., Langer, W.H., and Knepper, D.H., Jr., 2005, Stratigraphy, lithology, and sedimentary features of Quaternary alluvial deposits of the South Platte River and some of its tributaries east of the Front Range, Colorado: U.S. Geological Survey Professional Paper 1705, 70 p. [also available at https://pubs.usgs.gov/pp/2005/1705/pdf/PP1705.pdf].
Machette, M.N., 1985, Calcic soils of the southwestern United States: Geological Society of America Special Paper 2013, 21 p.
Madole, R.F., 1991, Colorado Piedmont, | MMI06/td>/tr> |
26/td> | REFERENCES 3/td> | U.S. Energy Information Administration, 2021, Colorado state profile and energy estimates, https://www.eia.gov/state/analysis.php?sid=CO U.S. Geological Survey, 2022, Earthquake Hazards Program - Online Earthquake Catalog (web site); https://earthquake.usgs.gov/earthquakes/search/. US GeoSupply, Incorporated, 2020, Grain size card comparator: Grand Junction, Colorado, view at https://www.usgeosupply.com/collections/reference-charts. Weimer, R.J., 1996, Guide to the petroleum geology and Laramide orogeny, Denver Basin and Front Range, Colorado: Colorado Geological Survey Bulletin 51, 133 p. [also available at https://coloradogeologicalsurvey.org/publications/denver-basin-front-range-colorado-petroleum-geology-laramide-orogeny/]. Weld County (Colorado), 2022, FEMA January 2016 flood plain mapping update for Weld County: Weld County web site, Planning and Zoning, Floodplain Management [available at https://www.co.weld.co.us/maps/propertyportal/]. White, J.L., and Greenman, C., 2008, Collapsible soils in Colorado: Colorado Geological Survey Engineering Geology 14, 108 p. [also available at https://coloradogeologicalsurvey.org/2018/28848-collapsible-soils/]. Windsor (Town of), Colorado, Community Development, 2021, Geotechnical reports for various building projects, prepared by various geotechnical consulting firms, containing geotechnical borehole logs. Windsor (Town of), 2013, Road closure update: Civic Alert posting, September 13, 2013; https://windsorgov.com/CivicAlerts.aspx?AID=367&ARC=1289 Wintle, A.G., and Murray, Andrew, 2006, A review of optically stimulated luminescence characteristic and their relevance in single-aliquot regeneration dating protocols: Radiation Measurements, v. 41. p. 369-391. Yeck, W.L., Benz, H.M., Weingarten, M., and Nakai, J., 2016, Rapid response, monitoring, and mitigation of induced seismicity near Greeley, Colorado: Seismological Research Letters, v. 87, n. 4, p. 837-847. /td> | MMI07/td>/tr> |
27/td> | ACKNOWLEDGMENTS/td> | The authors sincerely thank the following for their assistance with the Windsor quadrangle mapping project. Ralph Shroba, Scientist Emeritus with the U.S. Geological Survey and geologist with the Colorado Geological Survey (CGS), was the peer reviewer and his valuable suggestions improved this map. Scot Fitzgerald of the CGS assembled the lidar imagery for the quadrangle and surrounding area. Steven L. Forman of Baylor University, Waco, Texas performed the optically stimulated luminescence (OSL) analyses and Beta Analytic, Inc. in Miami, Florida performed the radiocarbon analyses. Jill Carlson of the CGS assisted in obtaining geotechnical logs associated with CGS land-use reviews. David Eisenbraun, Senior Planner with the Town of Windsor, provided copies of geotechnical reports for local building projects and these reports contained a great number of shallow borehole logs. Kyren Bogolub of the CGS assisted with the evaluation of seismic hazards. Matthew Morgan, State Geologist and CGS Director, reviewed the final publication and Caitlin Bernier of Pangaea Geospatial, Gunnison, Colorado produced the final map plates and GIS files. Coulson Excavating Co. and Loveland Ready Mix, Inc. allowed us to visit and sample their aggregate pits on the Big Thompson River valley. We also thank the many other landowners in the Windsor quadrangle who permitted us to visit and work on their properties, and the contractors who allowed us to examine and sample trenches and foundation excavations. All this assistance was invaluable to our geologic research and facilitated the completion of this geologic map./td> | MMI08/td>/tr> |
28/td> | STATEMAP AGREEMENT/td> | This mapping project was funded jointly by the Colorado Geological Survey and the U.S. Geological Survey through the National Cooperative Geologic Mapping Program under STATEMAP agreement G21AC10708-00./td> | MMI09/td>/tr> |
29/td> | TITLE/td> | GEOLOGIC MAP OF THE WINDSOR QUADRANGLE, LARIMER AND WELD COUNTIES, COLORADO By Stephen M. Keller and Alexander E. Marr 2022 OPEN-FILE REPORT 22-08 | MMI10/td>/tr> |
30/td> | MAP SOURCE/td> | Geologic map of the Carter Lake Reservoir quadrangle, Boulder and Larimer Counties, Colorado, Braddock, P.W. and others, 1988 (description of formations below Pierre Shale)/td> | MMI11/td>/tr> |
31/td> | MAP SOURCE/td> | Notes on the Denver Basin geologic maps, Dechesne, M., and others, 2022, Colorado Geological Survey Open-File Report 11-01 (selected unpublished supporting data)/td> | MMI12/td>/tr> |
32/td> | MAP SOURCE/td> | Geologic and biostratigraphic map of the Pierre Shale between Jarre Creek and Loveland, Colorado, Scott, G.R., and Cobban, W.A., 1965 (description of Pierre Shale)/td> | MMI13/td>/tr> |
33/td> | MAP SOURCE/td> | Coal geology and coal, oil, and gas resources of the Erie and Frederick quadrangles, Boulder and Weld Counties, Colorado, Spencer, F.D., 1986 (description of Fox Hills Sandstone)/td> | MMI14/td>/tr> |
OBJECTID | GrainSizeDist | Bedding | Sorting | Roundness | Color | SandComp | GravelComp | Cohesion | SecondCarb | Soils | Map_Unit | /tr>/thead>
---|---|---|---|---|---|---|---|---|---|---|---|
1/td> | Sand is medium (mL) to coarse (cU) or very coarse (vcU) sand; gravel is granules to cobbles (up to 9 cm)/td> | (Could not be observed)/td> | Poor to moderate/td> | Sand is subangular to subrounded; gravel is subrounded to rounded/td> | Gray and light gray of hue 10YR/td> | Quartz 75-85% , feldspar and others 10-15%, opaques 5-10%/td> | Granitics, gneiss, fine-grained dark metamorphics, vein quartz, red sandstone, minor volcanics/td> | Loose or weak/td> | None/td> | Riverwash/td> | Qa1/td>/tr> |
4/td> | Sandy gravel or gravelly sand, poorly sorted mixture of 50% sand and 50% gravel; sand is very fine (vfL) to fine (fU) with ~25% medium (mL); gravel is from granules to cobbles (up to 20 cm)/td> | Indistinct bedding indicated by alignment of clasts/td> | Very poorly sorted/td> | Sand is subangular to subrounded; gravel is rounded to well rounded/td> | Pale brown of hue 10YR/td> | Quartz 75%, feldspar and others 20%, <5% opaques/td> | Granitics, gneiss, dark-colored fine-grained metamorphics, vein quartz, quartzite/td> | Weak to moderate/td> | Carbonate rinds on many pebbles and cobbles; sand matrix has pervasive stage III or stage IV secondary carbonate/td> | Cascajo gravelly silt loam/td> | Qg1/td>/tr> |
5/td> | Matrix of clay- and silt-sized secondary carbonate, with <30% gravel of pebbles and cobbles (up to 30 cm)/td> | Exposure too poor to see bedding/td> | Poorly sorted/td> | Gravel subrounded to rounded/td> | Pinkish white of hue 7.5YR/td> | Not applicable/td> | Granitics, gneiss, vein quartz, quartzite/td> | Very cohesive/td> | Stage IV secondary carbonate, carbonate rinds 3 mm thick on cobbles/td> | Larim gravelly sandy loam/td> | Qg2/td>/tr> |
6/td> | Most locations are silty clay or clayey silt, with minor sand ranging from very fine (vfL) to medium (mL); locally, very fine (vfL) to medium (mU) sand with minor fines, and very fine (vfL) to medium (mU) or very coarse (vcU) sand, with minor fines/td> | Massive/td> | Moderately to well sorted/td> | Mostly silt and clay, did not record sand roundness/td> | Very pale brown, pale brown, light yellowish brown, brown, grayish brown, dark grayish brown of hue 10YR/td> | Mostly silt and clay, did not record sand composition/td> | Not applicable/td> | Moderately to strongly cohesive/td> | Most locations have moderate to violent effervescence but no visible carbonate; some locations have scattered carbonate filaments and nodules 1-3 mm; rare locations have nodules up to 9 cm, or nearly continuous carbonate zones (stage III)/td> | Colby loam, Kim loam, Nunn clay loam, Vona sandy loam, Wiley silt loam/td> | Qe/td>/tr> |