Apr 122017

We just uploaded the most recent of our STATEMAP mapping products to our online store: the Geologic Map of the Longmont Quadrangle, Boulder and Weld Counties, Colorado. The STATEMAP series in general provides a detailed description of the geology, mineral and ground-water resource potential, and the geologic hazards of an area. This particular 7.5-minute, 1:24,000 quadrangle is located immediately east of the Front Range uplift of Colorado and includes most of the town of Longmont within its borders. The geologic map plates were created via traditional field mapping, structural measurements, photographs, and field notes acquired by the investigators. Richard F. Madole, Scientist Emeritus at the USGS was the lead geologist for the project. This free release from the CGS includes two plates (with a geologic map, cross-section with correlation, oblique 3D view, legend, and description) along with the corresponding GIS data package that allows for digital viewing, all in a single zip file.

From the map history:

The Longmont quadrangle is in the northern part of the Colorado Piedmont, which is a section of the Great Plains that is bounded on the west by the Front Range and on the east by the High Plains section of the Great Plains. It is distinguished primarily by the fact that it has been stripped of the Miocene fluvial rocks (Arikaree and Ogallala Formations) that cover most of the High Plains. Headward erosion of the South Platte and Arkansas Rivers and their tributaries caused most of the stripping. Like much of the Colorado Piedmont, the Longmont quadrangle is an area of low hills and plains underlain by Upper Cretaceous (100–66 Ma) sedimentary rocks. Most of these rocks consist of fine-grained sediment (clay, silt, and fine sand) that accumulated in a broad seaway (Western Interior Seaway). This seaway connected the areas of the present-day Arctic Ocean and the Gulf of Mexico and extended from Minnesota and western Iowa on the east to central Utah on the west.

Even before urbanization, Upper Cretaceous bedrock was exposed in only a few places in the Longmont quadrangle because loess of late Pleistocene age (126 ka to 11.7 ka) blankets about 85 percent of the area. Deposition of most loess is attributed to northwesterly winds, which during the last glaciation (between about 40 ka and 12 ka) were stronger than they are today, blowing across extensive areas upwind from the Longmont quadrangle that are underlain by siltstone, mudstone, and shale. Thus, eolian sediment covers almost all bedrock and surficial deposits (loose, uncemented sediment as opposed to rock) that were at the surface prior to the end of the last glaciation. The floors of the major streams in the Longmont quadrangle also bear the imprint of Pleistocene glaciations. The gravel deposits that are mined in several places along St. Vrain and Boulder Creeks consist mostly of granitic and gneissic rocks that were derived from the Front Range and transported to the piedmont during glaciation. The headwaters of the St. Vrain, Lefthand, and Boulder Creeks were glaciated repeatedly during Pleistocene time. The principal glaciers in these areas were 10–12 miles (16-20 km) long and as much as 600–1150 ft (2-350 m) thick.

This mapping project was funded jointly by the U.S. Geological Survey through the STATEMAP component of the National Cooperative Geologic Mapping Program, which is authorized by the National Geologic Mapping Act of 1997, and also by the CGS using the Colorado Department of Natural Resources Severance Tax Operational Funds. The CGS matching funds come from the severance paid on the production of natural gas, oil, coal, and metals. Geologic maps produced through the STATEMAP program are intended as multi-purpose maps useful for land-use planning, geotechnical engineering, geologic-hazard assessment, mineral-resource development, and ground-water exploration.

Citation: Madole, Richard F. Geologic Map of the Longmont Quadrangle, Boulder and Weld Counties, Colorado. Geology. Open File Reports. Golden, CO: Colorado Geological Survey, April 2017.
Feb 172017
IS-79 Colorado Mineral and Energy Industry Activities 2015-16 (cover)

The current annual Colorado Mineral and Energy Industry Activities report 2015-16 is now available. Following up on the 2014 report, this report, based on 2015 production data, sketches a comprehensive overview of Colorado’s mineral resource production. Of note is the fact that total value of mineral and energy fuels production in Colorado for 2015 is estimated to be $13.43 billion, a 29% decline from the $18.8 billion production value in 2014. The decline was caused primarily by a precipitous decrease in oil and gas market prices which provide 70% of Colorado mineral resource revenue. Oil and gas production actually registered at all-time highs of 127.6 Mbbl and 1,709 Bcf, respectively.

Nonfuel mineral production — including metals, industrial minerals, and construction materials — posted a modest 3.9% increase in revenue. Increased production of crushed stone, cement, and sand and gravel aggregate accounted for the increase. With a 2015 production of 21,790 metric tons of molybdenum from two mines, Colorado is the largest molybdenum producer in the U.S. Although just one mine in the state publicly reported gold production in 2015, Colorado remains the third largest producer of the metal in the U.S. as it was in 2014.

Citation: Cappa, James A., Michael K. O’Keefe, James R. Guilinger, and Karen A. Berry. “IS-79 Colorado Mineral and Energy Industry Activities 2015-16.” Mineral and Energy Industry. Information Series. Golden, CO: Colorado Geological Survey, 2016.
Feb 062017

With all the precipitation in the Rockies this year (we’re at +153% normal snowpack at the moment), we thought we would re-release a publication that highlights at least one important aspect of Colorado snowfall — that is, the significant danger of avalanches. The Snowy Torrents: Avalanche Accidents in the United States 1980-86, compiled and written by Nick Logan and Dale Atkins and illustrated with Larry Scott’s fine pencil drawings, was first published in 1996. We still have a few hard-copies available and, because of that, yes, we do charge for the PDF download. However, Larry went back and re-made the PDF from the original publication file, producing a file that is far better than the rather poor digital scan we had offered previously.

The volume details 146 oft-times harrowing stories surrounding avalanches, the lives they claim, survivors and witnesses, along with assessments as to what happened, why it happened, and what could have been done to prevent loss of life and/or property. The authors are never judgmental, and their clear-eyed accounts contain a wealth of wisdom that will add to the knowledge-base of any winter backcountry enthusiast.

Citation: Logan, Nick, and Dale Atkins. SP-39 The Snowy Torrents: Avalanche Accidents in the United States, 1980–86. Special Publications 39. Denver, CO: Colorado Geological Survey, Department of Natural Resources, 1996.
Jan 312017

A collaboration between the CGS and the Denver Museum of Nature & Science (DMNS) has resulted in a new stratigraphic chart for the state of Colorado. This beautifully (offset-)printed 42″ x 39″ color chart was designed from the ground up to illustrate the Proterozoic to Holocene stratigraphy that spans the state’s many sedimentary basins. A collaborative effort led by Robert Raynolds and James Hagadorn, the chart builds upon the work of dozens of colleagues and updates Richard Pearl’s seminal 1974 stratigraphy chart. The chart leverages the community’s stratigraphic work in both the subsurface and outcrop, and depicts new geochronologic constraints for many units. To facilitate comparison of strata to external forcing factors, the chart employs a linear timescale. Each unit’s dominant depositional environment is depicted as are major mountain building events, erosional events, and regional unconformities. Printed on heavy-duty 100# coated cover stock, these rolled posters may be purchased from the CGS online bookstore. They will make a fine gift for geoscientists, rockhounds, or anyone interested in how Colorado’s magnificent landscapes came to be.

From the chart itself:

Colorado’s stratigraphy is dominated by gaps. The distribution of strata reflects the tectonic and climatic evolution of each of the region’s eleven basin areas, depicted in the map below. To foster comparison of these patterns, we have organized the stratigraphy using a linear timescale and illustrated where orogenic uplift has led to removal of strata or nondeposition. Not all orogenic features are illustrated on the chart. For example, some orogenies caused sediment ponding and accumulation in intermontane basins, such as during the Laramide in northwestern Colorado. In the past ~10 Ma, regional uplift has raised Colorado and has allowed the modern landscapes to be created due to erosion. The chart’s color scheme for stratigraphic units gives a sense of dominant lithologies and depositional environments across basins. Updates to this chart, as well as additional stratigraphic resources, such as stratigraphic and structural cross-sections, may be found at http://coloradostratigraphy.org. To learn more about the unit names on this chart, resources are available at the U.S. Geological Survey’s Geolex site. This chart scaffolds on the work of Richard H. Pearl’s 1977 compilation (Rocky Mountain Association of Geologists, Special Publication 2). With the exception of the Carboniferous and Permian periods, this data has been re-cast against the International Commission on Stratigraphy’s chronostratigraphic chart v. 2015/01, updated at http://stratigraphy.org.

Citation: Raynolds, R. G., and James W. Hagadorn. “MS-53 Colorado Stratigraphy Chart.” Stratigraphic. Map Series 53. Denver, CO: Colorado Geological Survey and the Denver Museum of Nature & Science, January 2017.
Jan 232017

The CGS’s Matt Morgan and Jon White were two of the co-authors on one of the top-ten Geological Society of America (GSA) 2016 book chapters and journal articles, this out of 600 papers. The article describes a comprehensive forensic analysis of the massive West Salt Creek rock avalanche that occurred in late May 2014 in western Colorado (USA). The analysis relied on large-scale (1:1000) structural mapping accomplished via high-resolution unmanned aircraft system imagery along with seismic data generated by more than twenty stations within approximately 500 miles (800 km) of the event. The avalanche was the largest mass-movement slope failure in the historical record of Colorado, and it killed three people, narrowly avoiding destroying a gas wellhead.

Citation: Coe, Jeffrey A., Rex L. Baum, Kate E. Allstadt, Bernard F. Kochevar, Robert G. Schmitt, Matthew L. Morgan, Jonathan L. White, Benjamin T. Stratton, Timothy A. Hayashi, and Jason W. Kean. 2016. “Rock-Avalanche Dynamics Revealed by Large-Scale Field Mapping and Seismic Signals at a Highly Mobile Avalanche in the West Salt Creek Valley, Western Colorado.” Geosphere 12 (2): 607–31. doi:10.1130/GES01265.1.
Jan 132017

We’ve decided to revive one of our most popular print publications — RockTalk — as a blog so that we can continue to bring you interesting, informative, and timely postings related to our mission. This year, 2017, will see 110 years since the founding of the CGS.

The first RockTalk appeared in 1998 and was followed by forty seasonal issues until the most recent one in 2011. We constantly get requests for back issues and to continue publishing, so in accordance with the times, we decided to make the shift to digital media. We hope you will join us by subscribing (to receive an email when we make a new posting, please enter your email in the subscription box in the right-hand column).

Content-wise, we’ll be exploring all of the many aspects of our State Survey mission to:

  • Help reduce the impact of geologic hazards on the citizens of Colorado
  • Promote responsible economic development of mineral and energy resources
  • Provide geologic insight into water resources
  • Provide geologic advice and information to a variety of constituencies

And, along the way, we’ll also post pertinent information on general geology, geoscience research and education, science and engineering policy, and other items that cross our screens. If you have any questions or suggestions, please get in touch!