“SHOULD WE BE CONCERNED ABOUT EARTHQUAKES IN COLORADO?”
Colorado Geological Survey
In general, Colorado is not considered to be at risk from significant earthquake damage. The state is ranked 30th in the nation in terms of Annualized Earthquake Losses by the Federal Emergency Management Agency and Denver is rated by the USGS National Seismic Hazard maps as having about the same seismic risk as Atlanta, Georgia. However, a growing body of data suggests that Colorado may be at greater risk than previously recognized. Colorado has the second largest heat flow anomaly in the North American continent, fifty-nine peaks over 14,000 feet in elevation, and extensive Neogene deformation indicating an active tectonic province. The catalog of Quaternary faults has steadily increased from none in 1960 to nearly ninety in 1998 with many areas of the state unexamined. The large 1882 earthquake has been definitively located in the northern Front Range. Studies of Quaternary faults in Colorado have resulted in thirteen faults being assigned a “maximum credible earthquake” >Mw 6.25 and as high as Mw 7.5. With Colorado’s rapidly growing population (3rd fastest in the nation) significant, additional research needs to be directed toward Colorado’s earthquake hazard.
“A TRAVERSE IN TIBET: CULTURES AND CONTINENTS IN COLLISION.”
Consulting Geologist, Longmont, CO
The dramatic effects of plate tectonics have given us the topographic features of the Himalayan mountain front and the Tibetan plateau. Huge thrust faults carry delaminated continental crust and associated passive margin sediments up and southwards across the northern fringe of India. The suture zone marking the vanished Tethys Seaway is defined by ophiolites and deep-sea trench sediments that now lie exposed to the sun on the Tibetan Plateau. Confrontations of similar magnitude exist between cultures in Asia and Western life-styles, contrasting worlds brought increasingly into contact by the efficiency of communication and ease of travel. This talk will examine some of the manifestations of both styles of collision. The future behavior of the plates may be the easier of the two outcomes to predict.
February 2002 – Emmons Lecture
“TRANSTENSION IN ARCS AND OROGENS”
John F. Dewey
Department of Geology, Uuniversity of California at Davis
Transtension is oblique extension, a combination of coaxial zone-orthogonal extension and non-coaxial zone-parallel shear. It is typical of extensional zones for many reasons, mainly because plate boundary and deformation zones are rarely perfectly orthogonal to plate and block boundaries. The transport direction (TD) is defined as the slip vector between the separating blocks or plates. The instantaneous extension direction (Xi) is not parallel with TD but bisects the angle between TD and the zone boundary orthogonal. The finite extension direction (X) rotates towards TD. Lines, planes, and structures in the obtuse angle between TD and the zone orthogonal rotate, with vorticity, towards TD; those in the acute angle rotate against vorticity towards TD. Where the angle (a ) between TD and the zone orthogonal is less than 70.5º, the principle shortening direction (Zi) is vertical and the intermediate (shortening) direction (Yi) is horizontal. This generates sub-horizontal foliation and vertical dykes and fissures and steeply dipping conjugate normal faults intersecting in Yi and folds and constrictional stretching lineations parallel with X. Where a is greater than 70.5º, Zi is horizontal and Yi is vertical, generating vertical foliation and conjugate strike-slip faults (Riedels and anti-Riedels) an folds and lineations prallel with X. Thus, TD can be calculated for any deformation zone where the angle a /2 can be determined; this is of enormous potential in determining relative plate motions.
Transtension is of great importance but is, as yet, very poorly understood in convergent plate boundary zones. Intra-oceanic juvenile arcs are dominated by transtension where subduction rollback occurs with motion of the over-riding plate away from the trench line. In Newfoundland, a fine example of a transtensionally-distended Cambria-Ordovician arc with oblique dykes and horizontally stretched pillows and supra-subduction-zone ophiolites is superbly exposed with a complicated polyphase structural and igneous history.
Transtension dominated the late extensional “collapse” of several orogens. Orogenic transtension leads to tectonic denudation by crustal thinning and extensional detachment and the development of high temperature/and low-pressure metamorphic assemblages with subhorizontal foliations and stretching directions, so typical of the Tasman Belt of Australia and the Variscan belt of Europe. Transtensional Xi and X parallel folds are expressed as periclines and “corrugations” in extensional detachments in the Cenozoic Basin and Range and in the Silurian Caledonides of western Norway.
“TERROIR – THE CONNECTION BETWEEN WINE AND GEOLOGY”
Department of Geology, Washington State University, Pullman, WA, Meinert@wsu.edu
Terroir is a relatively simple term to describe the complex interplay of climate, soil, geology, and other physical factors that influence the character and quality of wine. Although the term has long been used in France, it is increasingly being used in other parts of the world to try to better understand the cause and effect of great wine. This talk will focus on the terroir of Washington State, which is second only to California in terms of wine produced in the United States. This is somewhat surprising in that Washington has a relatively short history of wine production by international standards. Although the first Vitis vinifera grapes were planted in 1825 by the Hudson’s Bay Company along the banks of the Columbia River in southwest Washington, commercial production extends back only about 100 years and most of the state’s 155+ wineries were started in the past 15 years (there were only 19 wineries when the author moved to Washington in 1981).
Washington is a region of superlatives, both oenological and geological, with exposures of some of the world’s largest and most spectacular flood basalts, dune and loess fields, and glacial outburst flood deposits. All of these play a part in the terroirs of Washington State wines. In addition, recent volcanic activity such as the well-known 1980 eruption of Mt. St. Helens continues to shape the oenological and geological landscape. Most Washington State vineyards are located between latitudes 45° and 48° N, well to the north of the more widely known California vineyards but parallel to some of the great French wine regions such as Burgundy and Bordeaux. This northerly latitude provides about two hours more summer sunlight than occurs in California wine regions. In addition, most Washington vineyards lie in the rain shadow of the Cascade volcanic arc, and many vineyard soils have a compo-nent of ash from Mt. St. Helens and other Cascade volcanic eruptions such as the much larger Mt. Mazama eruption (6,850 yr BP) which formed present day Crater Lake in Oregon.
Although there is considerable local variability, most Washington vineyards are located on Quaternary sediments and soils that overlie Miocene basaltic rocks of the Columbia River flood basalt province. Many of the Quaternary sediments are related to cataclysmic glacial outburst floods that formed the spectacular geomorphic features of the Channeled Scablands. This in itself is one of the great geologic stories of all time, and the fact that it is intimately related to superlative wine makes a discussion of Washington wine and terroir particularly worthwhile. The fact that some of the geological and soil features are unique to this part of the world suggests the possibility that Washington wines (including Cabernet Sauvignon, Chardonnay, Merlot, Riesling, and Syrah) may develop flavour and quality characteristics that set them apart from other wine-producing areas.
April 2002 – Annual Family Night
“GEOLOGY GOES HOLLYWOOD AND OTHER PUBLIC PERCEPTIONS OF GEOSCIENCE”
Sonoma State University, Sonoma, California
If the way geology is portrayed in such cultural vehicles as Dante’s Peak (remember that SUV sashaying across hot lava?) and Star Trek (how did the cave floors of all those unexplored planets get so flat?) is any indication, America is either scientifically ignorant or has a rich vein of wry humor. While I hope it’s the latter, some of the reviews my books get suggest that it’s the former. It’s enough to make me want to found a geology anti-defamation league.
The media appear to be here to stay, so I suggest instead that we bend it to our will. Geologists are natural storytellers, and telling stories is the media’s stock in trade. The human species is just as easily entertained, and are better informed, by reality-based stories as by fantasy. Certainly the public’s interest in the geology snaps to attention each time the earth shakes, spews molten rock, or disappears under water. And many people evidence an authentic longing to know more about the oblate spheroid they live on. How many of us have heard phrases like, “I’ve always had a secret desire to [be a geologist] [know more about geology] [study dinosaurs], but [I knew I couldn’t do the math] [my parents wanted me to study dentistry instead] [I was born female in the wrong generation], so…”
Visual, auditory, and literary storytelling is as powerful a tool for influencing public opinion as it ever was. The media consciously and unconsciously sell not only reality and fantasy, but also cultural values and valuation. The stories people hear strongly influence their political, ethical, religious, and scientific beliefs. It is important therefore that we understand and fully utilize this tool, and emerge not only as sympathetic protagonists rather than flat, passionless, often ominous antagonists in someone else’s story, but also as authors of an advancing culture.
Sarah Andrews is the author of seven forensic geology mystery novels and is a lecturer in Geology at Sonoma State University. She holds a B.A. from Colorado College and an M.S. from Colorado State University and is the recipient of the 1999 AAPG Journalism Award and the 1997 RMAG Journalism Award.
The hilarious and thought-provoking video “Geology Goes Hollywood,” produced by Dr. Dorothy Stout and edited by Deborah Steller, will be shown for the second part of this media-oriented family-night program.
“OVERVIEW OF CIVILIAN SATELLITE IMAGING SYSTEMS – HOW IT IS REVOLUTIONIZING WORLDWIDE MINERAL EXPLORATION”
Sandra L. Perry
Perry Remote Sensing LLC, Englewood, Colorado
Civilian imaging satellites have been in orbit since 1972 and have provided a valuable database for a variety of earth science applications. Digital image analysis of these satellite data systems has aided vegetation mapping and monitoring, mineral & hydrocarbon exploration, agricultural uses and planning, archeology, and global change observations. From a mineral exploration standpoint, image analysis has provided timely, ready-to-go information that offers both geological and logistics information for worldwide operations. In the last three years, new satellite systems have revolutionized how mineral explorationists and field geologists conduct international exploration. These new systems offer higher spectral and spatial resolution detail, which coupled with global positioning systems (GPS) and geographic information systems (GIS) makes fieldwork more effective and efficient. With more demanding needs for metals worldwide, satellite imagery together with GPS and GIS have become necessary tools for the field geologist. This presentation will summarize applications of satellite imagery for international mineral exploration and field geology.
“THE USOI LANDSLIDE DAM AND LAKE SAREZ, SOUTHEASTERN TAJIKISTAN”
Robert L. Schuster
U.S. Geological Survey, Golden, Colorado
In 1911, a massive earthquake-triggered rock slide (volume: ~2 km3) dammed the Murgab River in the Pamir Range of southeastern Tajikistan. The still-existing blockage is 600 m high, by far the largest dam, natural or man-made, in the world. Lake Sarez, impounded by this natural dam, is about 60 km long, with a maximum depth of approximately 550 m, and a volume of about 17 km3. The lake has never overtopped the dam; instead, it exits the downstream face as several large springs that regroup to form the Murgab River. There currently is about 50 m of freeboard between the lake surface and the lowest point of the dam crest, and the lake is rising at about 20 cm/yr.
If this natural dam were to fail, a worst-case scenario would endanger some five million people in the Bartang, Panj, and Amu Darya valleys downstream. Dam failure potentially could be due to: (1) seismic shaking, (2) catastrophic overtopping caused by a landslide entering the lake at high velocity from the valley wall, (3) surface erosion due to natural overtopping by the slowly rising lake, (4) internal erosion (piping), (5) instability caused by pressure of the lake against the dam, or (6) instability of the slopes that form the dam faces. Because of the high cost of installing physical remediation to the dam in this rugged mountain area (there are no roads to the dam), the main protective measures now being undertaken are hydrological monitoring at the dam and installation of a flood early-warning system downstream.
Recent studies of the Usoi landslide and natural dam and Lake Sarez, which have been funded mostly by the World Bank, the Swiss government, the Government of Tajikistan, and USAID, with cooperation from FOCUS Humanitarian Assistance, have been carried out mainly by Stucky Consulting Engineers of Lausanne, Switzerland. Field studies currently are “on hold” because of the situation in Afghanistan, but Stucky engineers and geologists currently are planning to return to the field in May of 2002.
“THE USGS NATIONAL WATER QUALITY ASSESSMENT PROGRAM AND WATER QUALITY IN THE UPPER COLORADO RIVER BASIN”
Norm E. Spahry
USGS National Water Quality Assessment
Streams and rivers in the Upper Colorado River Basin (UCOL) are very different in the two major physiographic provinces. In general, streams within the Southern Rocky Mountains are characterized by lower sediment and dissolved-solids concentrations, cooler temperatures, and somewhat higher gradients than streams in the Colorado Plateau. Sediment, salinity, and nutrient (nitrogen and phosphorus) concentrations increase along the major rivers as the water flows from the upstream areas in the Southern Rocky Mountains down through the Colorado Plateau.
Coupled with the general differences due to physiography and geology are the effects of different land uses. Recreation and urban development are becoming major land-use issues throughout the basin, precious metal mining was historically prevalent in the Southern Rocky Mountains, and intensive agriculture is located in the valleys of the Colorado Plateau.
Most of the streams and rivers sampled within the UCOL met State and Federal water-quality guidelines. Major exceptions to this statement were trace-element concentrations in some streams in the Southern Rocky Mountains and selenium concentrations in some streams in the Colorado Plateau. The talk will discuss other selected findings regarding nutrient concentrations, algae, mining areas, pesticides, and herbicides.
“SAND DUNES ON THE GREAT PLAINS AND THEIR NOT-SO-ANCIENT HISTORY”
Daniel R. Muhs
U.S. Geological Survey, Denver, Colorado
Eolian (wind-blown) deposits, such as sand dunes, are both a blessing and a curse: they contain a valuable record of past climate changes but are deposits that could be reactivated in the future, with serious consequences for the natural resources, food supply, infrastructure, and wildlife of the country. In this talk, new geologic and historic records of eolian sands of the U.S. Great Plains will be presented. In addition, I will assess the potential for renewed activity of wind-blown sediments under possible future drought conditions.
Sand dunes are extensive on the Great Plains. The Nebraska Sand Hills region is the largest sand sea, active or stabilized, in North America. Dunes also occur over large areas of eastern Colorado and New Mexico, western Kansas, and the panhandles of Texas and Oklahoma. Modern winds on the Great Plains are stronger than in most of the world’s deserts. However, sand dunes on the Great Plains are inactive at present because of a sparse cover of grass and associated grassland community plants, such as sage, yucca, and cactus.
Previously, it was thought that most sand dunes on the Great Plains were last active during the last glacial period, at least 12,000 years ago. New radiocarbon ages show that most dunes on the Great Plains have been active in the past 3,000 years. In addition, accounts of early explorers show that many dunes were active during the 19th century. Examination of aerial photographs in the National Archives shows that some dunes, stable now, were active during the 1930s “dust bowl” drought. Thus, it can no longer be assumed that these dunes are ice-age features that have little threat of reactivation in the future.
Great Plains dunes have been active, therefore, under interglacial climatic conditions that are only slightly different from the present. If the dunes are reactivated in the future, either from human-caused global warming or natural climatic variation, there would be significant impacts on the region. Stabilized dune fields at present form some of the most important areas of grazing land. Areas immediately downwind of the dunes are important croplands. Interstate highways and railroads are also downwind of large dune fields. Many interdune areas, particularly in the Nebraska and North Dakota, are wetlands that support wildlife. Thus, reactivation of Great Plains dunes would have significant impacts on both human society and wildlife of the region.
“DETERMINING THE EFFECTS OF WASTEWATER POLLUTANTS ON THE DILLON RESERVOIR WATERSHED, COLORADO, USING A WATERSHED-SCALE WATER QUALITY MODEL”
Paula Jo Lemonds
Department of Geology and Geological Engineering
Colorado School of Mines
With over 1,000 onsite wastewater systems (OWS) in the Dillon Reservoir watershed located in Summit County, Colorado, the effects of effluent from these systems are important for watershed water quality management. Thin soils hinder the attenuation of wastewater effluent and can allow nutrients to reach groundwater resources or surface water bodies. The objective of this study is to quantify the influence of OWS pollutants on the ground water and surface water using a watershed-scale water quality model. The EPA’s Better Assessment Science Integrating Point and Nonpoint Sources (BASINS) and the Soil and Water Assessment Tool (SWAT), which is interfaced with BASINS 3.0, were applied to this problem. SWAT utilizes physically based data, simulates land use and management scenarios, and takes into account process interactions through a GIS environment. Water-quality data from groundwater and surface water samples, as well as streamflow and groundwater hydraulic head measurements are being collected at three focus areas in the watershed. Data collected upstream and downstream of each of these sites show a change in the signature of nitrate and phosphorus, two wastewater constituents. This information is used to evaluate the performance of the model, which uses national public-access databases for initial model development.
“RE-OS DATES FOR THE MALANJKHAND DEPOSIT, AN ARCHEAN TO E. PROTEROZOIC PORPHYRY”
Aaron Zimmerman (presenter, undergraduate student), Stein, H., Hannah, J., Markey, R., Sarkar, S.C., and Pal, A.B.
Colorado State University
The Malanjkhand Cu(Mo) ore deposit, a subduction related porphyry located in Central India, is one of a handful of Archean to Early Proterozoic porphyry deposits found worldwide. As a result, the age, genesis, and classification of the deposit are highly debated in the literature. The Re-Os geochronometer provides a means for quelling the debate, and the analyses show a variety of well constrained dates corresponding to multiple mineralization events.
The dates are derived from a series of samples corresponding to the differing rock types seen at the site. The host rock is a potassically altered and deformed granodiorite with disseminated molybdenite and iron sulfides. The pluton is cut by planar, steeply dipping, quartz veins containing stringers and blebs of sulfides including molybdenite and chalcopyrite.
Based on 5 different molybdenite samples, the geologic history is that the host granite was the first to be mineralized at 2493 ± 3 Ma. At 2491 ± 8 Ma, small quartz veins are mineralized in small fractures in the host granite. Large quartz dikes form next at ~2476 Ma and at ~2452 Ma. The entire history is well constrained by replicate analyses and field relationships.
The dates show that the deposit is Archean to Early Proterozoic in age and the Re concentrations are similar to those seen in younger subduction-related porphyry systems. Only by using the Re-Os geochronometer can highly precise dates distinguish the numerous mineralization events that occurred at Malanjkhand.
“HYDROGEOLOGIC INVESTIGATION INTO THE EFFECTS OF MANAGED RECHARGE ON WATER QUALITY, LOWER SOUTH PLATTE RIVER”
Jamey T. Watt (presenter, M.S. student), Sanford, William E, Stednick, John, and Durnford, Deanna
Colorado State University
In order to meet in-stream flow requirements at the Colorado-Nebraska border, managed recharge along the lower South Platte River Basin is being used as a method for flow augmentation. The site is located on the Colorado Division of Wildlife’s Tamarack Ranch State Wildlife Area in northeastern Colorado. During late winter/early spring, when there is no call for water from the South Platte, approximately 20 acre-feet per day of water is pumped from the alluvial aquifer near the river into a recharge pond approximately 1 km away. The goal is to have water return to the river during low flow periods prior to snow melt runoff in order to augment in-stream flows for endangered species in Nebraska. In this talk, we will present current findings on the areal and temporal distribution of water quality parameters (including nitrate, sulfate, alkalinity, DO, and specific conductance) within the alluvial aquifer between the recharge pond and the South Platte River. Data collected to date suggest 1) a zone of higher nitrate levels along the alluvial aquifer nearer the river; 2) the sulfate concentrations of the water pumped into the recharge pond is similar to that of the alluvial aquifer than to the river water; and 3) there appears to be a smaller contribution from the river during pumping than initially expected. In addition, we will present the preliminary results of a tracer test performed to address recharge pathways and timing. The understanding of the pathways and flow rates is important in determining the influence of the recharge water on groundwater and surface water quality, especially in light of the increasing use of flow augmentation along the length of the lower South Platte River.
“JONAH AND PINEDALE FIELDS, GREEN RIVER BASIN, WYOMING CASE STUDY OF TWO EMERGING GIANT GAS FIELDS”
The Jonah-Pinedale area has undergone a renaissance in the last decade to become one of the fastest growing producing trends in the Rocky Mountain region. Combined production from both fields is rapidly expanding and pipeline capacity will be hard pressed to keep up with future production growth.
Jonah Field was discovered in 1986, but due to market conditions and ineffective stimulation methods, the production was not economic. In 1992, McMurry Oil Company bought the field and invoked new drilling and completion technology that unlocked the full potential of the play. The acquisition of 3D seismic resulted in a revolutionary new image of the subsurface, including the existence of the Western Bounding Fault and the Southern Boundary Fault that form the boundary of the pressure compartment. In the last few years, Jonah Field has become the largest gas producing field in the Rockies.
The first drilling activity in the Pinedale area was in 1939. In 1971 the area became widely recognized as a proposed site of an experimental subsurface nuclear stimulation, but the event never occurred. The field was dormant until the successful application of similar drilling and completion techniques in nearby Jonah Field revitalized the area. Recent acquisition of 3D seismic over the anticline has generated an improved image of the feature and will allow optimization of development drilling. Estimates vary, but up to 500 wells may be drilled on the anticline when it is fully developed.
“SECRETS OF SULFURIC ACID CAVES”
Miller, Dyer, & Co.
Many caves in the Guadalupe Mountains of New Mexico and west Texas contain sulfates, clays and other minerals that are byproducts of the dissolution of limestone by sulfuric acid. Guadalupe caves such as Carlsbad Cavern and Lechuguilla Cave also contain enigmatic mineral formations with shapes that suggest that they were formed by, or nucleated around, filamentous or colonial bacteria. However, the processes that formed Guadalupe caves ceased about 4 Ma, and the characteristics of these possible life forms are unknown. To test the hypotheses that life existed in these caves while they were forming, several modern sulfur caves were studied. These include the Kane Caves of Wyoming, Cueva de Villa Luz in Mexico, the Frasassi Caves of central Italy, and Movile Cave in Romania. These caves are being formed today by the action of sulfuric acid on limestone. In addition, they support a remarkable abundance of life forms, including microbes that thrive in total darkness in low-pH environments and in an atmosphere filled with toxic gases. The life forms in these extreme environments attracted the attention of scientists who see them as possible analogs for life elsewhere in the universe.
December 2002 – Presidental Address
“A GEOLOGICAL EXCURSION IN NEW ZEALAND: COLLISIONAL SHORTENING AND DRAINAGE DIVIDE MIGRATION IN THE SOUTHERN ALPS”
Colorado School of Mines
New Zealand is a geologically fascinating and beautifully scenic land that is not only tectonically very active, but also serves to illustrate many of the geological processes involved in mountain building. In 2000-2001 I was fortunate to spend a sabbatical year on South Island and to study some of these processes. I will report on the general tectonics of New Zealand and will focus on river piracy that has resulted from crustal shortening adjacent to an active plate boundary. New Zealand started its rock life as part of Gondwanaland, snuggled up against Australia and Antarctica. Cretaceous rifting relieved it of this burden and produced a passive continental margin on the east coast that has been somewhat creaky ever since; 20-10 million year old volcanoes are still exposed along this coast. Subsequently, New Zealand took the form of microplates which jostled about and finally slid past one another as New Zealand evolved from being home to a transform plate boundary to an oblique collisional plate boundary, the Alpine fault. As along the San Andreas plate boundary in California, strain is distributed for at least 220 km into the plate and is expressed as faults and folds. The Alpine fault transitions into a diffuse southwest-vergent subduction zone to the south (Puysegur trench), and it splays to the northeast into a broad zone of oblique wrench faults before changing to a northeast-vergent subduction zone (Hikurangi trough) along the east coast of North Island. North Island today contains an extensional back arc region with beautiful stratovolcanoes and geothermal springs known to be modern, active mineralizing systems.
The Alpine fault is an obliquely convergent plate boundary and shows ~480 km of dextral offset and up to 25 km of vertical separation since the Miocene. The convergent component is illustrated by the 4 km-high Mt. Cook, and by impressive exposures of mylonitic garnet amphibolite thrust over Recent gravels. The Main Divide region of the Southern Alps is being progressively shortened in response to the convergent component of plate motion, and the rocks of the Main Divide region are being transported westwards towards the plate boundary. This lateral migration of the continental divide has resulted in a jog in the otherwise linear divide, and in the capture of south-flowing streams, which became west-flowing streams. The region of the divide jog was localized in a zone of cross faulting, along which hydrothermal fluid flow concentrated, forming quartz-carbonate-(± Au) veins. These and other vein systems in the Southern Alps show that metamorphic dewatering in an evolving orogen contributes to the precious-metal budget of such tectonic regimes, including some of the Au placers to the east.