| OBJECTID | MapProperty | MapPropertyValue | MiscellaneousMapInformation_ID |
|---|
| 1 | GEOLOGIC HISTORY AND STRUCTURE PARAGRAPHS 1, 2, 3, 4, 5 | 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. | MMI01 |
| 2 | GEOLOGIC HISTORY AND STRUCTURE PARAGRAPHS 6, 7, 8, 9, 10 | 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. | MMI02 |
| 3 | GEOLOGIC HISTORY AND STRUCTURE PARAGRAPHS 11 | 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. | MMI03 |
| 4 | MINERAL RESOURCES, GROUNDWATER RESOURCES, AND GEOLOGIC HAZARDS | 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). | MMI04 |
| 5 | REFERENCES 1 | 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/].
| MMI05 |
| 6 | REFERENCES 2 | 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, in Wayne, W.J., ed., Quaternary geology of the Northern Great Plains, Chap. 15 of Morrison, R.B., ed., Quaternary nonglacial geology - conterminous United States: Geological Society of America, The geology of North America, v. K-2, p. 456-462.
Madole, R.F., 2016, Geologic map of the Longmont quadrangle, Boulder and Weld Counties, Colorado: Colorado Geological Survey Open-File Report 16-05, scale 1:24,000 [also available at https://coloradogeologicalsurvey.org/publications/geologic-map-longmont-quadrangle-boulder-weld-colorado/].
Madole, R.F., VanSistine, D.P., and Michael, J.A., 2005, Distribution of late Quaternary wind-deposited sand in eastern Colorado: U.S. Geological Survey Scientific Investigations Map 2875 (scale 1:700,000) [also available at https://pubs.er.usgs.gov/publication/sim2875].
Matthews, N.E., Vázquez, J.A.; Calvert, A.T., 2015, Age of the Lava Creek supereruption and magma chamber assembly at Yellowstone based on 40Ar/39Ar and U-Pb dating of sanidine and zircon crystals: Geochemistry, Geophysics, Geosystems, v. 16, p. 2508–2528 (also available at https://doi.org/10.1002/2015GC005881].
Muhs, D.R., Aleinikoff, J.N., Stafford, T.W., Jr., Been, Josh, Mahan, S.A., and Cowherd, Scott, 1999, Late Quaternary loess in northeastern Colorado, Part I - age and paleoclimatic significance: Geological Society of America Bulletin, v. 111, n. 12, p. 1861-1875.
Munsell Color, 1991, Munsell soil color charts, 1990 edition revised: Newburgh, NY, Macbeth Division of Kollmorgen Instruments Corp., 14 p.
Murray, Andrew and Wintle, A. G., 2003, The single aliquot regenerative dose protocol: Potential for improvements in reliability: Radiation Measurements, v. 37, p. 377-381.
Nichols, G., 2009, Sedimentology and stratigraphy (second edition): Wiley-Blackwell, Chichester (United Kingdom), 419 p.
Palkovic, M.J., 2020, Geologic map of the Bracewell quadrangle, Weld County, Colorado: Colorado Geological Survey Open-File Report 20-03, scale 1:24,000 [also available at https://coloradogeologicalsurvey.org/publications/geologic-map-bracewell-quadrangle-weld-colorado/].
Palkovic, M.J., Lindsay, K.O., and Morgan, M.L., 2018, Geologic map of the Milliken quadrangle, Weld County, Colorado: Colorado Geological Survey Open-File Report 18-02, scale 1:24,000 [also available at https://coloradogeologicalsurvey.org/publications/geologic-map-milliken-quadrangle-weld-colorado/].
Palkovic, M.J., and Morgan, M.L., 2017, Geologic map of the Johnstown quadrangle, Larimer and Weld Counties, Colorado: Colorado Geological Survey Open-File Report 17-02, scale 1:24,000 [also available at https://coloradogeologicalsurvey.org/publications/geologic-map-johnstown-quadrangle-larimer-weld-colorado/].
Palkovic, M.J., and Morgan, M.L., 2021, Geologic map of the Hardin quadrangle, Weld County, Colorado: Colorado Geological Survey Open-File Report 21-02, scale 1:24,000.
Peng, Liang, and Forman, S.L., 2019, LDAC: An Excel-based program for luminescence equivalent dose and burial age calculations: Ancient TL, v. 37, p. 21–40.
Prescott, J.R., and Hutton, J.T., 1994, Cosmic ray contributions to dose rates for luminescence and ESR dating: large depths and long-term time variations: Radiation Measurements, v. 23, p. 497-500.
Riihimaki, C.A., Anderson, R.S., Safran, E.B., Dethier, D.P., Finkel, R.C., and Bierman, P.R., 2006, Longevity and progressive abandonment of the Rocky Flats surface, Front Range, Colorado: Geomorphology, v. 78, p. 265-278.
Schwochow, S.D., Shroba, R.R., and Wicklein, P.C., 1974, Sand, gravel, and quarry aggregate resources, Colorado Front Range Counties: Colorado Geological Survey Special Publication 5B, Plate 1 [also available at https://coloradogeologicalsurvey.org/publications/atlas-sand-gravel-quarry-aggregate-colorado-front-range/].
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 [also available at https://pubs.usgs.gov/imap/0439/report.pdf (report), https://pubs.usgs.gov/imap/0439/plate-1.pdf (map)].
Shelton, D.C, and Rogers, W.P., 1975, Bedrock surface topography of valley-fill areas, Windsor study area, Larimer and Weld Counties, Colorado: Colorado Geological Survey, Environmental Geology No. 6, map No. 6-1, scale 1:96,000.
Slattery, J.S., Cobban, W.A. McKinney, K.C., Harries, P.J., and Sandness, A.L., 2013, Early Cretaceous to Paleocene paleogeography of the Western Interior Seaway: The interaction of eustasy and tectonism: Wyoming Geological Association 68th Annual Field Conference guidebook, v. 68, p. 22-59.
Spencer, F.D., 1986, Coal geology and coal, oil, and gas resources of the Erie and Frederick quadrangles, Boulder and Weld Counties, Colorado: U.S. Geological Survey Bulletin 1619, 58 p. [also available at https://pubs.usgs.gov/bul/1619/report.pdf].
Topper, Ralf, Spray, K.L., Bellis, W.H., Hamilton, J.L., and Barkmann, P.E., 2003, Ground water atlas of Colorado: Colorado Geological Survey Special Publication 53, 210 p. [also available at https://coloradogeologicalsurvey.org/water/colorado-groundwater-atlas/].
U.S. Department of Agriculture, Natural Resources Conservation Service, 2018, Assessing carbonates in the field with a dilute hydrochloric acid solution: Soil Survey Technical Note 5, 7 p. [also available at https://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/ref/?cid=nrcs142p2_053572]. | MMI06 |
| 26 | REFERENCES 3 | 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. | MMI07 |
| 27 | ACKNOWLEDGMENTS | 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. | MMI08 |
| 28 | STATEMAP AGREEMENT | 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. | MMI09 |
| 29 | TITLE | 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 DOI:https://doi.org/10.58783/cgs.of2208.lfhf7370 | MMI10 |
| 30 | MAP SOURCE | 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) | MMI11 |
| 31 | MAP SOURCE | Notes on the Denver Basin geologic maps, Dechesne, M., and others, 2022, Colorado Geological Survey Open-File Report 11-01 (selected unpublished supporting data) | MMI12 |
| 32 | MAP SOURCE | 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) | MMI13 |
| 33 | MAP SOURCE | 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) | MMI14 |