Past Field Trips

The Colorado Scientific Society usually has a Spring and a Fall field trip. They generate trip guides, maps and other illustrations, and pictures of people learning and enjoying themselves. The most recent field trips are listed first.

The field trip guides for some field trip’s can be downloaded, usually as PDFs. The size of files larger than 3 MB is called out in the link, e.g. “Quaternary San Luis Basin, Ancient Lake Alamosa, 2007 (PDF 4.6 MB)”.

Some field trips have so much information they have their own pages. Please follow the links.


Geology of the Upper Arkansas Valley, September 2018

CSS 2018 Fall Field Trip, September 15-16, 2018
Led by Karl Kellogg, Cal Ruleman, and Scott Minor, USGS

We spent two days examining diverse geologic features of the beautiful Upper Arkansas Valley:

  • Proterozoic sedimentation, volcanism, and plutonism
  • Laramide Orogeny structural features
  • Northern Rio Grande Rift and Upper Arkansas Valley magmatism, tectonism, and sedimentation
  • Pre-rift intrusive rocks and Oligocene and Eocene volcanic rocks
  • Glacial history and deposits including catastrophic outwash floods
  • Mineral deposits (gold, silver, copper, zinc, lead, fluorspar, and others)
  • Landslide, alluvial, mass-movement, eolian, and wetland deposits

This field trip deserves its own page, with all the details: Geology of the Upper Arkansas Valley, September 2018

Front Range Pleistocene Geomorphology and Mysterious Gravel Deposits

April 15, 2018
Leaders: Cal Ruleman (USGS), Bob Raynolds (Denver Museum of Nature and Science), and Beth Simmons (retired)

We explored several sites along the I-70 corridor and up along Highway 103 on the northeast shoulder of the Mount Evans massif. We began with an overview of the previous work within the area and relationships that have been previously established, from the Eocene Rocky Mountain erosional surface to Pleistocene incision rates and the timing for onset of major Pleistocene glacial epochs. After our meeting spot overview, our first stop was at the Genessee Park-I-70 junction with discussions pertaining to geomorphology east and west of the Floyd Hill Divide. We then went to the Casino Parkway and the large exposure of the Central City Gravel. Here we had time for personal observation of the deposit and geomorphic relationships. We discussed probable mechanisms for deposition and relationships to distal fan surfaces and chronologic relationships to the east on the Great Plains. We continued up Chicago Creek at Idaho Springs with stops at Last Glacial Maximum (Pinedale) moraines and till deposits for comparison with the Central City Gravel. Proceeding up Highway 103 to Echo Lake and Juniper Pass we observed geomorphic similarities between Bear and Clear Creeks with probable coeval glacial-induced landscape incision. Cal provided a new perspective for future investigations involving Pleistocene geomorphic development of the Rocky Mountain-Great Plains region.

Looking west above Clear Creek

Incision profile across Clear Creek

This field trip deserves its own page, with all the details: Front Range Pleistocene Geomorphology and Mysterious Gravel Deposits


CSS Flat Tops/White River Plateau Field Trip

August 26-27, 2017

Emphasizing the Devonian in Colorado and its extinction events, we toured the Paleozoic section exposed on the Flat Tops.  Participants also discussed other topics including glacial history and the incision of Colorado River.

Note: Dr. James Hagadorn of the Denver Museum of Nature and Science planned to lead this trip, but coming over from Denver he hit a deer and totaled his car. Fortunately, James was OK.  Linda Soar, who has volunteered with DMNS on Flat Tops for years, explained the Devonian and Mississippian sections and fossils near Bison Lake and by the Crane Park quarry.

Saturday, Aug. 25, we drove to Dotsero on I70 and took the Coffee Pot Road up to the Flat Tops. We camped at the White Owl Campground, which is on top of the Flat Tops at 10,680 feet.

Morning at White Owl Lake

Sunday, Aug 26, Look at Devonian section west of Bison Lake and by the Crane Park quarry.

Stop 1: Bison Lake Section – We spent the morning examining the Dyer Formation facies and fossils at Bison Lake, including examination of its contacts with the underlying Parting Sandstone and the overlying Leadville Limestone, and the end-Famennian extinction interval.  Ate lunch above Bison Lake.

Devonian beds west of Bison Lake

Stop 2: Crane Park Quarry – Early afternoon – examined the Gooey Lagoon & discuss its origin. We also examined vertebrate teeth-bearing lags, as well as the knobbly-bedded facies of the Dyer exposed at Crane Park Quarry.

Head for home. Some of us headed back Sunday evening. Others avoided the weekend traffic and enjoyed another night at the White Owl Campground.

Follow this link for an interactive Forest Service map that covers the Flat Tops.

Geologic Wonders of the Hart(sel) of South Park

June 25, 2017
Leader: Peter Barkmann, Colorado Geological Survey

South Park geologic map

This field trip explored the Hartsel area, starting with a look at the Precambrian granodiorite and its cross-cutting pegmatite sheets. We then saw the onlap of the Late Paleozoic central Colorado trough sediments onto the ancestral Front Range highland and the Garo Sandstone healing cover. Our transect then looked at the Laramide synorogenic South Park Formation with its complex stratigraphic story. Last but not least was the Neogene transformation from compression to extension with a fascinating story of Neogene tectonic closure of intermontane fluvial systems and progressive integration and incision driven by middle to late Pleistocene glacial episodes.

This field trip deserves its own page, with all the details: Field Trips 2017, Geologic Wonders of the Hartsel of South Park


Basement hosted sandstone dikes of the Colorado Front Range

June 25, 2016
Basement hosted sandstone dikes of the Colorado Front Range: structural and other field  relations, and contemplation of origins

Leaders:  Christine Smith Siddoway, Colorado College, and Scott Lundstrom, USGS

New research in the southern Front Range reveals a Neoproterozoic ancestry for some of the range-bounding faults, due to their association with basement-hosted sandstone dikes that indicate Neoproterozoic age [1],  based on detrital zircon (DZ) sedimentary provenance that includes characteristic components from the Grenville Orogen.  Informally named Tava sandstone, DZ data indicate that the sandstone dikes and other large associated fault-bounded bodies formed during the Cryogenian Period, and as such the Tava sandstone provides a ‘waypoint’ in the vast span of time between emplacement of the Pikes Peak Granite at ~1.1 Ga and the deposition of Cambrian Sawatch Sandstone upon the Great Unconformity. In other words, it offers access to exploration of paleoenvironments that previously have been inconceivable.

Sandstone injectites are formed by liquefaction, remobilization and intrusion of sand into fractures within host rock, that in most circumstances involves upward injection from buried sands into overlying sediments/sedimentary rocks in active sedimentary  basins.  Hence the occurrence in Colorado of detrital, nonmetamorphosed injectites within crystalline basement is distinctive, and may require different geological circumstances for downward injection.   The sedimentary injectites likely are a product of ’natural fracking’ of the sort that may have been achieved by large magnitude earthquakes,    transient subglacial hydraulic conditions of large ice sheets, or regional scale mass wasting (rock slab failure)  — possibilities that we hope to explore with CSS members who participate in the field trip.

Exposures of Tava sandstone along the Ute Pass Fault system may be found from Penrose, CO in the south, northwestward to Pine, CO, but this trip will focus on accessible sites near Buffalo Creek, and then proceed to Crystola and Manitou Springs where large associated sandstone bodies can be examined.  The road-side stops require no hiking, but the Crystola and Manitou Springs stops (the latter only if there is time) involve hikes upslope, over rough terrain.

[1] Siddoway, C.S. and Gehrels, G.E. (2014)  Basement-hosted sandstone dikes of Colorado:  a vestige of the Neoproterozoic revealed through detrital zircon provenance analysis:  Lithosphere 6(6): 403–408  doi:10.1130/L390.1

New discoveries of dinosaur tracks & markings at Dinosaur Ridge, Morrison CO

June 18, 2016
Leader: Dr. Martin Lockley

Several of Martin’s new discoveries here have been in the news. He showed them to us for creative discussion and debate!


Green Mountain kimberlite pipe, Boulder Colorado

July 27, 2013
Leader: Pete Modreski

A short day hike to visit the most accessible and best exposed kimberlite pipe in Colorado. The Green Mountain kimberlite is located within Boulder Open Space and Mountain Parks, between Flagstaff Mountain and Green Mountain. The hike to the site, starting at the “Realization Point” trailhead, is only about one mile each way, mostly via the Ranger and Greenman trails, but it does involve negotiating a fairly steep grass/dirt hillside off-trail to cross a side valley to the kimberlite outcrop. Total elevation climb on the hike is about 500 feet. The pipe forms a good outcrop, about 140 feet in diameter, surrounded by Boulder Creek Granodiorite. This pipe, age about 600Ma (?), is the southernmost kimberlite of the State Line Kim-berlite District, and is the only kimberlite of the district in which diamonds have not been confirmed to have been found. The classic kimberlite indicator minerals, pyrope garnet, chrome diopside, and magnesian ilmenite, can be seen in the rock.

Recap of CSS 2013 Summer Field Trip by Pete Modreski
About 24 of us met in Boulder the morning of July 27 to hike to the Green Mountain kimberlite pipe. Our CSS folks were joined by some members of the Florissant Scientific Society. We had a pleasant hike up through the woods, everyone reached the pipe (and made it back too), and this group photo shows our crowd, all sitting/standing on the small knob formed by the outcrop of the pipe, which underlies the small clearing within the otherwise mostly forested mountainside. We were back at the Realization Point trail-head at 1 p.m., just as promised. A few of us enjoyed a side stop on the drive back down from Flagstaff Mountain; a rhyodacite sill intruded into the Fountain Formation, nicely exposed at the Crown Rock trailhead.


Catastrophic Glacial Outburst Floods on the Upper Arkansas River

Field Trip from Leadville to Buena Vista – September 29, 2012
Led by Keenan Lee and Cal Ruleman

The Floods
During the Pleistocene, glaciers from the Sawatch Range flowed down three contiguous tributary valleys to the Arkansas River near Granite, Colorado. The Lake Creek glacier probably pushed the Arkansas River out of its channel, and the Clear Creek and Pine Creek glaciers crossed the river and rammed into granite walls on the far side of the valley. These glaciers formed an ice dam about 670 ft high that blocked the Arkansas River and created a large lake about 600 ft deep that extended 12 miles upstream below Leadville.
When the ice dam broke, the lake drained catastrophically. The outburst flood tore out the ends of the moraines and carried the detritus down the valley in a torrent of dirty water that deposited a sheet of flood boulders 60 ft thick in less than a day. Many flood boulders are tens of feet in diameter, and some can be found 150 ft up on the valley wall.
At least four catastrophic floods swept the Upper Arkansas Valley, together called the Three Glaciers Floods. Field evidence documents well the last two floods, but only patches of older flood boulders attest to two earlier floods. The most recent flood dates to the Last Glacial Maximum, or Pinedale age, with a cosmogenic age of 17-19 ka. The oldest flood is older than 760 ka, and the second flood is older than 640 ka. The age of the third, or penultimate, flood is currently under debate. Perhaps field trip participants can judge the field evidence and contribute to a solution.

The Field Trip
The trip will begin in Leadville and cover 50 miles with 10 stops, ending in Buena Vista. Stops will include overviews of the three glacial systems, a view of the glacial damsite from atop a lateral moraine, ice-rafted boulders at the shoreline of Three Glaciers Lake, flood boulder deposits, flood boulders 150 ft above the modern Arkansas River, remnants of the two oldest floods, and the granddaddy flood boulder 61 ft long.

Look at the flyer: CSS_Glacial Flood on Arkansas flyer, Sept-2012

The field trip guide with high-res illustrations: CSS Glacial Flood on Arkansas River, Trip Guide, Sept-2012 (PDF 8.1 MB)

The Geology of the Upper Arkansas Valley, 2018 Field Trip also explored this area and events.

July 2012:  Family Friendly CSS Field Trip – Pegmatites near Harris Park

On Saturday, July 21, about 15 CSS members and friends (including a couple of children) met to collect pegmatite minerals near Harris Park, Colo. Our destination was pegmatite mining claims belonging to the Littleton Gem and Mineral Club, and our visit was courtesy of that club. CSS President Pete Modreski (also a member of the Littleton mineral club) led the trip. The site is at about 9000’ elevation in Pike National Forest, north of US-285, and lies at the foot of the “Pegmatite Points” ridge east of Rosalie Peak. It lies within an offshoot of the Pikes Peak batholith, formerly known as the Rosalie Lobe (until it was discerned that the granite on Mt. Rosalie is really part of an older pluton) and now called the Lone Rock pluton, believed to be a cupola connected to the main Pikes Peak batholith at depth. Small pegmatite dikes cut through the granite on the wooded hillsides, and are host to crystals of smoky quartz and microcline; some of the feldspar is the blue-green variety, amazonite, for which Colorado is famed for among mineral collectors. Associated minerals can include albite, fluorite, topaz, goethite, hematite, and others.
A few people in the group found good specimens of quartz crystals, some of which were smoky and some not, plus microcline crystals and small amounts of fluorite. The elusive amazonite wasn’t much in evidence, beyond a few cleavage scraps left behind from previous “digs,” nor was any topaz found. But it was a beautiful day and all had a good time, and the small creek to ford just before reaching the claim site proved passable for everyone’s vehicles!
President’s Message, by Pete Modreski

June 2012: Cumbres & Toltec Scenic Railroad Geology Train Excursion

On Sunday, June 24, the Cumbres & Toltec Scenic Railroad operated a special train from Antonito, Colorado, to Chama, New Mexico, specifically for geologists. This train stopped at many  outcrops and cuts along the right of way to allow geologists to mingle, take photographs, and collect rock samples.


Late Cenozoic Evolution of the Colorado with optional bike trip down Glenwood Canyon

CSS 2011 Fall Field Trip

Fall 2011 Field Trip Flyer


The Grand Loop Field Trip—A Tribute to Bruce Bryant


The Victor Mine

Front Range Tertiary and Quaternary Geology – Honoring Glenn Scott

The trip featured the geology of the western Colorado Piedmont and adjoining Front Range, and focused in particular on Quaternary geology and geomorphology, Tertiary erosion surfaces, and zonation of the Pierre Shale, topics to which Glenn has made major contributions.

See details in the flyer: 2009 Front Range Field Trip to Honor Glen Scott


Amazonite-bearing pegmatites in the  Pikes Peak Batholith, near Harris Park, Park County, CO

New Insights into the Geologic and Geomorphic Evolution of South Park Basin

Trip to the northern Never Summer Range volcanic field – “The search for Braddock’s Caldera”


Quaternary Geology of the San Luis Basin near Alamosa, Colorado with Ancient Lake Alamosa

Led by Michael Machette, U.S. Geological Survey

GIS recreation of Lake Alamosa at about 500 thousand years ago.
View is to the NNE from San Luis Hills.

June 2-3, 2007: The CSS spring field trip was led by Mike Machette to ancient Lake Alamosa, the Plio-Pleistocene lake that occupied a large part of the San Luis Valley. On this trip, participants examined various lake features, such as spits, bars and lagoon deposits, discussed the timing and ultimate overflow of the lake, peat and tufa deposits, and visited the Quaternary Mesita Volcano. The trip also visited the Sangre de Cristo fault zone and its scarps near Fort Garland, some of which are as young as early Holocene. There was a brief stop near Kenosha Pass to arm wave at the eastern margin of South Park where mapping by USGS has shown possible late Quaternary faults.
Download the field trip guide for the Quaternary San Luis Basin and Ancient Lake Alamosa (PDF):
Quaternary San Luis Basin, Ancient Lake Alamosa, 2007 (PDF 4.6 MB)

Mining History of Colorful Central City

Florissant Fossil Beds National Monument


CSS Fall Field Trip to the Paradox Basin

The 2006 Fall Field Trip for the Colorado Scientific Society was to the Paradox Basin, on September 29- October 1, 2006. The trip leader was Don Rasmussen, who has worked in the Basin for more than 30 years and has led numerous field excursions for universities and industry into the region. The trip began and ended in the La Quinta Hotel parking lot in Moab, Utah.



Gunnison Area

Trip Leaders: Bruce Bartleson and Alan Stork. Western State College; and Pete Modreski, USGS


The 2005 CSS fall field trip was to the Gunnison/Crested Butte area in central Colorado. The first day included traveling to Gunnison, then a half-day tour of the Powderhorn carbonatite. The second day’s topic was the structure of the Ancestral and Laramide Rockies as seen in the Elk Mountains near Crested Butte.  Stops for the second day included discussions of the structures around Almont and Jack’s Cabin, Crested Butte/Gothic, and Schofield Park. We went on a hike up to Schofield Basin and the Hasley Pass area to see an excellent view of the Elk Range thrust fault. The third day’s topic was the Tertiary volcanism and igneous activity in the Gunnison Basin. Stops will include the Ohio Creek valley to see the West Elk laccolith cluster and a series of 10 Ma basalt flows on Red Mountain. We will also see the ash-flow tuffs from the San Juans near Blue Mesa Reservoir and a drive up Red Creek to a great view of the 30 Ma West Elk Volcano. The fourth day included the travel back to Denver with stops along the route.

Western State College hosted the 2006 Rocky Mountain Section Meeting of the GSA. The CSS fall field trip was be a preview of some of the field trips associated with this meeting.

South Platte Country field trip, White Cloud Pegmatite + the 1996 Buffalo Creek fire and flood

Led by Pete Modreski
June 11, 2005

Some Fieldtrip Images
A field trip to visit (1) the White Cloud Pegmatite, part of the South Platte Pegmatite District within the Pikes Peak Batholith, and (2) to see erosion, sedimentation, and ecological recovery in the aftermath of the June 1996 Buffalo Creek forest fire and flash flood. The trip will involve a 2-3 mile (round trip) hike beginning at the Colorado Trail footbridge just south of the confluence of the North and South Forks of the South Platte River. The hike will take us partly on the Colorado Trail, off-trail down a steep 400′ hillside, and downstream along the wide gravel bed of Spring Creek.

Spanish Peaks

Led by Dr. Brian Penn
May 14, 2005

View of West Spanish Peaks showing radiating dikes and an igneous plug

Buffalo Creek Field Trip, June, 2005

Trip led by Pete Modreski.
Get the field guide here: Buffalo Creek Field Trip_June 11, 2005

Volcanic and Plutonic rocks of Table Mountain

Led by Harald Drewes
April 23, 2005


Southward view showing the Ralston “dikes” and North and South Table Mountains. The lava flows capping the Table Mountains are thought to have originated from Ralston dikes.

Download the North Table Mountain field trip guide

Pictures from the CSS 2005 North Table Mountain field trip

Spring 2004

Symposium Field Trip: The Tectonics and Precambrian Geology of the Front Range between Golden and Marshall

Led by Robert J. Weimer and Lisa A. Lytle, Colorado School of Mines
Sunday, 4 April 2004

The Colorado Scientific Society is presenting a field trip in conjunction with the Symposium of the Geology of the Front Range. The field trip will examine the tectonic features along the margin and some of the Precambrian features of within the Front Range between Golden and Marshall. Bob Weimer and Lisa Lytle are the primary field trip leaders, and speakers from the symposium are encouraged to provide additional commentary.


Upper Cretaceous, lower Paleocene, and early Eocene rocks of the Denver Basin

The first 2003 Colorado Scientific Society brown-bag field trip was held on Saturday, June 21. The trip examined the Upper Cretaceous, lower Paleocene, and early Eocene rocks of the Denver Basin; it was led by Bob Raynolds of the Denver Museum of Nature and Science. Bob vividly linked the stratigraphy, tectonics, and groundwater resources of these rocks into a comprehensive story of the Laramide development of the Denver Basin and the Front Range. Highlights of the trip included a grand overview at Daniels Park, a climb to another spectacular overlook on Wildcat Mountain, a walk into the depths of Castlewood Canyon, and finally a view of the lower Eocene paleosol near Parker. The trip’s 19 participants enjoyed the first non-rainy Saturday in June.

Field trip to the northern San Juan Volcanic Field

Sept. 2003
Field trip led by Peter Lipman.
Get field guide here: Field Trip to Northern San Juan Volcanic Field

Field trip to the Pawnee Buttes

Spring 2003
Led by Emmett Evanoff

2003 Spring field trip to Pawnee Buttes

And: Rocks and Faunas, Ogallala Group, Pawnee Buttes Area, Weld County, CO by Richard H. Tedford.

Fall 2002

Jackson Hole, Wyoming and the Tetons

Hayden survey sketch of Teton Valley from Upper GrosVentre Butte.


(click for detail)

The Fall 2002 Field Trip for the Colorado Scientific Society will visit Jackson Hole, Wyoming. Not only is Jackson Hole and the Teton Range one of the most spectacular landscapes in the United States, but this trip will be at a time when the fall colors should still be in all of their glory. The field trip leaders will be Ken Pierce, Jack Reed, and Lisa Morgan, all of the U.S.G.S. Ken (past president of the CSS) has worked out a detailed glacial history of the valley. Jack Reed (another past president) has studied the Precambrian rocks of the Teton Range, and is currently working with J. D. Love on the second edition to the geologic guide, the Creation of the Teton Landscape. Lisa Morgan has been investigating the Tertiary geology of Jackson Hole, and has determined the timing of the rise of the Teton Range. All three leaders are now experienced field trip guides, and will provide an excellent learning experience. The trip will be from Friday, 20 September to Monday, 23 September.