Hauling field gear up Gothic Mountain…
Integrates glacial chronology, floodplain hydrostratigraphy, and cosmogenic dating methods to reconstruct landscape evolution and groundwater systems across Colorado's mountain watersheds.
The mountains surrounding the Rocky Mountain Biological Laboratory in Gothic, Colorado, owe their dramatic shape and the chemistry of their streams to a long history of geologic and climatic events. Quaternary geology — the study of the most recent 2.6 million years of Earth history — and hydrogeology — the study of how water moves through rock and sediment — together explain why the East River runs the way it does, why some slopes carry talus and rock glaciers while others hold meadows, and why water chemistry varies dramatically from one tributary to the next. Understanding this physical foundation matters because the soils, aquifers, and stream networks that sustain Gunnison Basin ecosystems are direct inheritances from past glaciations, volcanic events, and erosion.
Several concepts run through the findings that follow. The Last Glacial Maximum (LGM) refers to the most recent peak of ice sheet and alpine glacier extent, roughly 20,000 years ago, when valley glaciers carved many of the U-shaped valleys around Crested Butte. Glacial advances during and after this period left terminal moraines (ridges of debris pushed to a glacier's farthest reach) and glacial striae (scratches on bedrock made by ice-borne rocks). Researchers reconstruct former ice extent through paleoglacier reconstruction, often using cosmogenic exposure dating — a technique that counts rare isotopes like beryllium-10 that build up in rock surfaces only after ice retreats and exposes them to cosmic rays. Rock glaciers — slow-moving tongues of rock and ice — are smaller cousins of true glaciers and serve as sensitive recorders of cooler climate intervals during the Holocene (the past ~11,700 years).
The basin's bedrock framework is equally important. The Laramide Orogeny, a mountain-building event roughly 70 to 40 million years ago, uplifted the Southern Rockies, and later caldera volcanism in the San Juans blanketed much of southwestern Colorado in ash and lava. Older sedimentary rocks, including the Cretaceous Mancos Shale and Mesaverde and Williams Fork formations, record ancient seaways through transgressive-regressive cycles. Different lithologic compositions — shale, sandstone, volcanic rock, granite — produce different stream chemistries through chemical weathering, the slow dissolution of minerals that delivers solutes to streams and consumes atmospheric CO2. Surface geomorphic features like landslides, moraines, and rock glaciers all create distinctive flowpaths that influence both water chemistry and surface runoff.
Early geological characterization of the region began with broad reconnaissance mapping. Cross and Larsen described the volcanic and sedimentary framework of the San Juan region , while Miller and colleagues mapped the Precambrian basement and Paleozoic cover of the southern Sangre de Cristo Mountains . Rankin's stratigraphic work on the Upper Cretaceous Colorado Group established that formations such as the Greenhorn limestone and Carlile shale could be traced across northern New Mexico and southern Colorado, providing a stratigraphic backbone for later studies .
Computational simulation of avalanche flow physics to predict runout distance and impact parameters
The spatial organization of sedimentary deposits and their hydraulic properties within floodplain aquifers
Interpretation of ancient environmental conditions based on fossil assemblages
Alteration of rocks by pressure and temperature conditions related to igneous intrusions that changes rock pore structure and mineralogy
Field mapping of volcanic rocks in thirteen 7.5-minute quadrangles combined with petrologic studies and high-resolution age determinations. Includes s...
Standard method for determining exposure ages of rock surfaces using in-situ produced cosmogenic ¹⁰Be nuclides measured by accelerator mass spectromet...
Laser ablation inductively coupled plasma mass spectrometry used for U-Pb detrital zircon geochronology analysis. Supports mapping and stratigraphic i...
Regional assessments of major aquifer systems providing quantitative assessments of water occurrence, movement, and availability. Includes classificat...
Numerical modeling approach combining energy-mass balance calculations with ice-flow modeling to reconstruct past glacier extents and determine paleoc...
Spectroscopic technique for quantitative determination of chemical elements in samples.
Chemical analysis method for determining precious metal concentrations in mineral samples.
The data here are associated with Quaternary Research manuscript Latest Pleistocene glacial chronology and paleoclimate reconstruction for the East Ri...
This dataset contains solute chemistry data and GPS coordinates for surface water samples collected in the East River watershed in the Elk and West El...
This Data Release provides tabular and geospatial data digitized by the U.S. Geological Survey (USGS) from a U.S. Bureau of Mines (USBoM) report title...
The Homestake Reservoir 7.5' quadrangle lies at the northwestern end of the Upper Arkansas Valley, and headwaters of the Arkansas River, and the Roari...
Geologic mapping, characterization of geologic structures, and sampling for geochronology was completed in two areas of the northwestern Sangre de Cri...
Quaternary research in the Elk Mountains and adjacent ranges took shape later. Retzer documented at least three glacial advances on Grand Mesa, recognizing that ice sheets had overtopped the mesa rim and that successive moraines differed strikingly in soil development — evidence of very different ages (Retzer, 1954). Decades later, Brugger applied cosmogenic 10Be and 36Cl dating to terminal moraines in the Taylor River drainage, providing the first numerical ages for late Pleistocene glaciation in the central Colorado Rockies (Brugger, 2007).
Across the Elk Mountains and Sawatch Range, paleoglacier reconstructions converge on a striking picture of Last Glacial Maximum climate. Using equilibrium-line altitudes from 22 reconstructed paleoglaciers and a degree-day mass-balance model, Brugger concluded that mean summer temperatures during the LGM were about 7°C cooler than present, and that this estimate is robust even allowing for modest precipitation changes (Brugger, 2010). This finding is consistent with independent reconstructions from across the Southern and Central Rockies. Schweinsberg and colleagues refined the timing of these events in the upper Arkansas River valley, reporting Pinedale terminal moraine ages averaging 21.8 ± 0.7 ka and outburst-flood terraces dating to roughly 19–21 ka, sharpening understanding of how mountain glaciers responded to global climate forcing (Schweinsberg et al., 2016).
Glacial signals continued into the Holocene at smaller scales. Refsnider and Brugger used lichen growth on rock glaciers in the Elk Mountains and Sawatch Range to identify three statistically distinct episodes of rock glacier activity at approximately 3080, 2070, and 1150 years before present, each interpreted as a discrete cooler interval (Refsnider & Brugger, 2007). The oldest episode aligns with widely documented Neoglacial cooling across the southern Rockies, while the younger two correspond to regional Audubon-age activity not always captured in other climate proxies.
The bedrock and surficial framework also controls modern water and slope behavior. Stratigraphic work demonstrated that key Cretaceous units such as the Greenhorn limestone can be mapped continuously across northern New Mexico, while overlying Mancos shales cannot be reliably subdivided in the field (Rankin, 1944). Sedimentologic analysis of the Dakota Sandstone documented dominant southeasterly paleocurrents sourced from the San Luis and Apishapa uplifts, helping reconstruct ancient drainage networks that influenced today's aquifer architecture (Campbell, 1976). On modern landscapes, avalanche modeling by Mears showed that tree removal and wind loading can extend a 300-year avalanche runout by roughly 50 meters — far enough to reach structures previously considered safe — a direct reminder that surface processes and human modification interact on geologic templates (Mears, 2006).
Early work from the 1930s through the 1970s established the stratigraphic and structural framework, while cosmogenic dating studies in the 2000s and 2010s pinned numerical ages onto glacial features. Research since 2020 has shifted toward integrating these long-term records with the modern critical zone — the thin layer where rock, water, and life interact. Quirk and colleagues recently extended the cosmogenic chronology directly into the East River watershed at Gothic, dating the retreat of the East River glacier from its maximum position to roughly 17–18 ka, with recessional stands between 13 and 15 ka (Quirk et al., 2024). Their paleoclimate reconstruction provides the first rigorous local glacial timeline for the watershed that anchors much of RMBL's contemporary ecohydrology research.
A second emerging direction connects geology directly to stream chemistry and the carbon cycle. Slosson and colleagues measured solute concentrations across Rocky Mountain watersheds with contrasting bedrock and land cover, demonstrating that landforms like landslides, moraines, and rock glaciers each generate distinct flowpaths and weathering signatures that modify the CO2 budget of mountain rivers (Slosson et al., 2025). New paleontological work on Cretaceous formations in northwestern Colorado is simultaneously refining understanding of the deeper sedimentary record (Eberle et al., 2024); (Crothers et al., 2026).
Many questions remain. How precisely did glacier retreat in the East River watershed track regional climate transitions such as Heinrich Event 1 and the Bølling-Allerød warming, and can the timing be refined enough to test ecological responses on the landscape that RMBL scientists study today? How do solute generation and CO2 drawdown vary between rock-glacier-dominated and moraine-dominated subcatchments, and how will these contributions change as alpine permafrost degrades? How will reductions in winter snowpack and changes to montane forest cover alter avalanche runout, slope stability, and floodplain aquifer recharge in coming decades? Answering these questions will require continued integration of geochronology, geomorphic mapping, and high-frequency hydrochemistry — the kind of cross-disciplinary work the Knowledge Fabric is designed to support.
Brugger, K. A. (2007). Cosmogenic 10Be and 36Cl ages from late Pleistocene terminal moraine complexes in the Taylor River drainage basin, central Colorado, USA. Quaternary Science Reviews. →
Brugger, K. A. (2010). Climate in the southern Sawatch Range and Elk Mountains, Colorado, U.S.A., during the last glacial maximum: inferences using a simple degree-day model. Arctic, Antarctic, and Alpine Research. →
Campbell, C. V. (1976). Sedimentology of braided alluvial interval of Dakota Sandstone, northeastern New Mexico. →
Cross, W., Larsen, E. S. (1935). A brief review of the geology of the San Juan region of southwestern Colorado. →
Crothers, R., et al. (2026). An actinopterygian-dominated fish fauna from the Upper Cretaceous Williams Fork Formation, northwestern Colorado. Cretaceous Research. →
Eberle, J. J., et al. (2024). A new Late Cretaceous metatherian from the Williams Fork Formation, Colorado. PLOS ONE. →
Mears, A. I. (2006). Avalanche size increase resulting from tree removal and wind loading — a case study from central Colorado using Aval-1D. →
Miller, J. P., Montgomery, A., Sutherland, P. K. (1963). Geology of part of the southern Sangre de Cristo Mountains, New Mexico. →
Quirk, B. J., et al. (2024). Latest Pleistocene glacial chronology and paleoclimate reconstruction for the East River watershed, Colorado, USA. Quaternary Research. →
Rankin, C. H. (1944). Stratigraphy of the Colorado group, Upper Cretaceous, in northern New Mexico. →
Refsnider, K. A., Brugger, K. A. (2007). Rock glaciers in Central Colorado, U.S.A., as indicators of Holocene climate change. Arctic, Antarctic and Alpine Research. →
Retzer, J. L. (1954). Glacial advances and soil development, Grand Mesa, Colorado. American Journal of Science. →
Schweinsberg, A. D., et al. (2016). Pinedale glacial history of the upper Arkansas River valley. Geological Society of America eBooks. →
Slosson, J., et al. (2025). Linking surface processes, solute generation, and CO2 budgets across lithological and land cover gradients in Rocky Mountain watersheds. Water Resources Research. →
The most recent time during the last glacial period when ice sheets were at their greatest extent
Measurement of ¹⁴C content to distinguish between modern plant-derived and ancient shale-derived organic carbon sources
Forward movement of ice sheets that leave behind terminal moraines and other glacial deposits
Temporal correlation of rock units based on fossil content
Reconstruction of past glacier extents and ice thickness using geomorphic evidence and numerical modeling
Linear scratches and grooves carved into bedrock by glacial ice movement
Late Cretaceous geological time intervals
Cycles of sea level rise and fall that control sediment deposition patterns in marine basins
Evidence of marine or estuarine conditions during sediment deposition based on presence of marine taxa
Analysis of pollen from archaeological site sediments to reconstruct past vegetation.
Scanning electron microscopy with cathodoluminescence imaging for characterizing zircon internal structure.
Detailed measurement and quantification of sedimentary structure types and their relative abundances in stratigraphic sections, including calculation ...
Fire assay for gold and silver, and spectrographic analysis for 40 elements including copper, lead, molybdenum, tungsten, and uranium.
Systematic sampling and isotopic analysis of carbon, oxygen, strontium, and sulfur from carbonate and sulfate minerals to determine paleoenvironmental...
In-field filtering of water samples using 0.2 µm polyethersulfone syringe filters. Removes particulate matter from surface water and groundwater sampl...
This Data Release provides tabular and geospatial data digitized by the U.S. Geological Survey (USGS) from a U.S. Bureau of Mines (USBoM) report title...
This data set includes a GIS geologic map database of an Early Proterozoic metavolcanic and metasedimentary terrane extensively intruded by Early and ...
This data release includes Al-26/Be-10 cosmogenic nuclide concentrations and burial isochron ages for three locations in central Colorado, USA, with p...
The Upper Colorado River Basin has a drainage area of about 113,500 square miles in western Colorado, eastern Utah, southwestern Wyoming, northeastern...
This archived Paleoclimatology Study is available from the NOAA National Centers for Environmental Information (NCEI), under the World Data Service (W...
Thirteen geospatial datasets were developed to characterize the shallow groundwater system in the Lower Gunnison River Basin, Colorado. These geospati...
This Laser ablation ICPMS U-Pb detrital zircon data set supports mapping and stratigraphic interpretations of the Upper Devonian Ignacio Formation in ...
On May 25, 2014, a rain-on-snow induced rock avalanche occurred in the West Salt Creek Valley on the northern flank of Grand Mesa in western Colorado....
This dataset consists of contours showing the generalized depth to water for the shallow groundwater system in the Lower Gunnison River Basin in Delta...
This dataset consists of contours showing the generalized saturated thickness of the shallow groundwater system in the Lower Gunnison River Basin in D...
Cement Creek Cave geochronologic (CEMENT) FAUNMAP (Neotoma)
Cement Creek Cave specimen stable isotope (CEMENT) Faunal Isotope Database (Neotoma)
This Data Release provides tabular and geospatial data digitized by the U.S. Geological Survey (USGS) from a U.S. Bureau of Mines (USBoM) report title...
The Upper Colorado River Basin has a drainage area of about 113,500 square miles in western Colorado, eastern Utah, southwestern Wyoming, northeastern...
The San Juan Mountains in southwestern Colorado have long been recognized as a site of exceptionally voluminous mid-Tertiary volcanism, including at l...
This archived Paleoclimatology Study is available from the NOAA National Centers for Environmental Information (NCEI), under the World Data Service (W...
This Laser ablation ICPMS U-Pb detrital zircon data set supports mapping and stratigraphic interpretations of the Upper Devonian Ignacio Formation in ...
The San Juan Mountains in southwestern Colorado have long been recognized as a site of exceptionally voluminous mid-Tertiary volcanism, including at l...
This data release includes Al-26/Be-10 cosmogenic nuclide concentrations and burial isochron ages for three locations in central Colorado, USA, with p...
This Data Release provides tabular and geospatial data digitized by the U.S. Geological Survey (USGS) from a U.S. Bureau of Mines (USBoM) report title...
This Laser ablation ICPMS U-Pb detrital zircon data set supports mapping and stratigraphic interpretations of the Upper Devonian Ignacio Formation in ...
On May 25, 2014, a rain-on-snow induced rock avalanche occurred in the West Salt Creek Valley on the northern flank of Grand Mesa in western Colorado....
This dataset accompanies publication: Minor, S.A., Caine, J.S., Ruleman, C.A., Fridrich, C.J., Chan, C.F., Brandt, T.R., Morgan,L.E., Cosca, M.A., and...
Geologic mapping, characterization of geologic structures, and sampling for geochronology was completed in two areas of the northwestern Sangre de Cri...
This dataset consists of isopach contours showing the generalized thickness of regolith sediments (alluvium, colluvium, and weathered bedrock) overlyi...
This release presents the GIS data (in GDB, shapefile, and e00 [coverage] formats) and metadata for a 1:24,000-scale geologic map of the Poncha Pass a...
Tree ring data from the International Tree Ring Data Bank and World Data Center for Paleoclimatology archives. Most data sets include raw treering mea...
Geologic mapping, characterization of geologic structures, and sampling for geochronology was completed in two areas of the northwestern Sangre de Cri...
Six bulk soil samples and seventeen detrital charcoal samples from sites TRCR1, TRCR2, TRCR4, TRCR5, and TRCR6 along Taylor River in Gunnison County, ...
The Chance Gulch site, 5GN817, is an 8000 year old camp located about 2.5 miles southeast of the town of Gunnison, Colorado. The site is situated with...
This data release includes Al-26/Be-10 cosmogenic nuclide concentrations and burial isochron ages for three locations in central Colorado, USA, with p...
Reported here are argon age data for samples collected to better understand lower Colorado River corridor landscape evolution, the history of the Colo...
This release presents the GIS data (in GDB, shapefile, and e00 [coverage] formats) and metadata for a 1:24,000-scale geologic map of the Poncha Pass a...
The San Juan Mountains in southwestern Colorado have long been recognized as a site of exceptionally voluminous mid-Tertiary volcanism, including at l...
The Upper Colorado River Basin has a drainage area of about 113,500 square miles in western Colorado, eastern Utah, southwestern Wyoming, northeastern...
Site 5GN2404, situated on a south-facing slope overlooking the Gunnison River Valley, was examined as part of work on the Blue Mesa-Skito Transmission...
This data release includes data collected from the Villa Grove helicopter magnetic survey in northern San Luis Valley and Poncha Pass region in south-...
Tree ring data from the International Tree Ring Data Bank and World Data Center for Paleoclimatology archives. Most data sets include raw treering mea...
This Laser ablation ICPMS U-Pb detrital zircon data set supports mapping and stratigraphic interpretations of the Upper Devonian Ignacio Formation in ...
The Upper Colorado River Basin has a drainage area of about 113,500 square miles in western Colorado, eastern Utah, southwestern Wyoming, northeastern...
This dataset accompanies publication: Minor, S.A., Caine, J.S., Ruleman, C.A., Fridrich, C.J., Chan, C.F., Brandt, T.R., Morgan,L.E., Cosca, M.A., and...
The San Juan Mountains in southwestern Colorado have long been recognized as a site of exceptionally voluminous mid-Tertiary volcanism, including at l...
This dataset was collected by Leah E. Morgan and Michael A. Cosca in the Argon Geochronology Laboratory of the USGS in Denver, Colorado in 2015. The d...