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Re-Os systematics in black shales: Marking time and the rise of atmospheric oxygen
How do we mark absolute time in sedimentary sections? How do we determine the age of sedimentary rocks when fossils are lacking? How can we use the chemistry of sedimentary rocks to understand earth surface processes in the past? All of these are long-standing questions and current hot topics, and the rhenium-osmium (Re-Os) isotopic system offers some answers.
Like more familiar isotopic systems (e.g., U-Pb, Rb-Sr, Sm-Nd) the decay of 187Re to 187Os can be used to determine the age of geologic materials, and the 187Os/188Os ratio can be used to fingerprint source materials. Re and Os are chalcophile/siderophile elements concentrated in metals, sulfides, and organic material. Both elements are soluble in oxidizing environments but fixed by reduction. Consequently, they are enriched in organic material in shales deposited under suboxic conditions, and concentrated in diagenetic pyrite.
We have successfully dated diagenetic pyrite in 2.32 Ga shale from the Transvaal Group in South Africa. This system also yielded a surprisingly low 187Os/188Os ratio, suggesting that oxidative weathering was still minimal at the earth’s surface at this time, even though sulfur isotope data show that oxygen had already begun to accumulate in the earth’s atmosphere. We are exploring additional shale sequences near the Archean-Proterozoic boundary (~2.5 Ga) to track the rise of atmospheric oxygen through its reflection in Os cycling in surface materials. Preliminary work on other systems shows that some similar shales are disturbed, perhaps by exchange of Re and/or Os between coexisting organic material and sulfides during low-grade metamorphism. Research is underway on direct analysis of chemically extracted organic material to refine methods of dating shales and tracking Os sources through time.
This work was done in collaboration with my colleagues at AIRIE, Holly Stein and Richard Markey, and supported by the National Science Foundation.
Necroforensics
Bio: Jim Reed studied geology at the University of Wyoming and Washington University in St. Louis. He has worked for NASA, Freeport Exploration, AMAX Exploration, and Wold Minerals. In 1983, Jim founded RockWare, a geological software company that services the mining, petroleum, civil engineering. and environmental industries. Jim's role in NecroSearch typically involves the integration and synthesis of disparate date sets into exploration targets.
Back to school and back to the office! Summer is always a great time for geologists. One of the projects we were working on at CGS this summer was the geology of Colorado State Parks. This was an eye opener. We figured that about half of the forty parks would be so boring that we wouldn’t have to do anything with them. NOT. All of them were interesting in their own way.
These parks again highlighted the fantastic diversity of geology that is so spectacularly displayed across the state. We are blessed to have so much within our borders. So, YOU should get out and see more of our fascinating geology-- and CSS field trips are a wonderful way to do so.
One of our trips last spring was a great aid to me in preparing the write-up on the geology of Lathrop State Park and in preparing a talk on the Geology of Huerfano County that was attended by over 100 people. Who knows how our fall trip to Gunnison County might help you in the near future. The geology and scenery in the area is special and Bruce Bartleson is a knowledgeable, fun leader.
The CSS Memorial Fund Committee (Emmett Evanoff, Bruce Bryant, Don Sweetkind, and Jim Cappa) met on April 27, 2005 to evaluate research proposals for the Tweto, Oriel, Eckel, Snyder, and Pierce funds. We received 28 proposals from 21 Universities—from all across the United States. The total was an increase of 4 from the previous year.
We awarded 13 grants totaling $9,950 from the Tweto, Oriel, Eckel, Snyder Fund, and the Pierce Heart Mountain Funds. A total of $3,000 was awarded from the Tweto Fund for research in the Rocky Mountains, which supported four proposals. The Oriel Fund for research in the central and northern Rocky Mountains awarded $2,000 to two proposals. The Eckel Fund for research in engineering geology awarded $1,500 to support two proposals. The Snyder Fund for research on Precambrian geology of the Rocky Mountains awarded $1,350 to two proposals. A total of $2,100 was awarded from the Pierce Heart Mountain Fund, under new guidelines established by the Pierce family last year, for research on the Heart Mountain fault and Quaternary geology. This year two proposals for work related to the Heart Mountain fault was funded as well as one other proposal.
Over the past 22 years (including this year), the Society has helped support the graduate research of 178 students, awarding a total of $135,607(an average of nearly $762 per grant). This achievement is extraordinary for an organization of our size and exemplifies the commitment of its members to promote high quality research in the field of earth. It was an honor and pleasure to serve as Memorial Fund Chair this year and I want to extend a “thank you” to all the Memorial Fund donors that have made these grants possible.
Funds were awarded to the following students and projects
Jennifer L. Aschoff, University of Texas at Austin, Control of Fold-Thrust Belt Transverse Zones on Basinal Sandstone Tongue Development in the Cordilleran Foreland Basin.
Richard S. Barclay, Northwestern University, Linking the Marine and Terrestrial Records of the Cenomanian- Turonian Oceanic Anoxic Event to Test the pCO2 Drawdown Hypothesis Using Fossil Plant Cuticle.
Erica Bigio, University of Arizona, The Integration of Tree-Ring and Alluvial Fan Records of Fire at the Missionary Ridge Fire, Durango Colorado.
Julia Ferguson, University of Illinois, Detailed Stratigraphic Analysis of the Upper Stratified Member of the Wapiti Formation, east-central Absaroka Range, Wyoming.
Kurt L. Frankel, University of Southern California, Tectonic Controls on Erosion in the Southern Rocky Mountains.
Kevin Hadder, Utah State University, Quaternary Stratigraphy and Geochronology of Browns Park, Utah and Colorado.
Jodi Lau, University of Illinois, Paleomagnetic Analysis of the Chinese Wall Trachyandesite, east-central Absaroka Range, Wyoming.
Scott Muggleton, University of New Mexico, Magnetic fabrics as indicators of magma flow and implications for emplacement mechanisms of the Spanish Peaks igneous complex (south-central Colorado).
Thomas Neeley, Colorado State University, 3D strain at transitions in foreland arch geometry: structural modeling of the Beartooth arch – Rattlesnake Mountain transition, NW Wyoming.
Daniel Peppe, Yale University, Integrated stratigraphy of a North American terrestrial Paleocene reference section: implications for long-term climate change and post-extinction biotic recovery.
Kelly R. Probst, University of Florida, Assessing Precambrian crust through a geochemical investigation of Mesozoic plutons in the northwestern Cordillera: Implications for continental reconstructions and metallogenesis.
Dustin Trail, University of Colorado, Identifying the earliest Precambrian crustal components: Detrital zircons from the Beartooth Mountains, Montana.
William Thomas Wilcox, Miami University, Ohio, Biostratigraphic evaluation of the Jurassic Curtis, Summerville, and Stump Formations, central-northeastern Utah.
Western State College will be hosting the 2006 Rocky Mountain Section Meeting of the GSA. The CSS fall field trip will be a preview of some of the field trips associated with this meeting.
Because of the decrease in motel room costs in September, the cost for the trip is $250 and this includes transportation, lodging (double occupancy) and lunches. If you wish to have a single room, then the cost will be $345, but please note that the number of single rooms is limited. Dinners and breakfasts are not included, but we will be staying all three nights in Gunnison that has many good restaurants.
If you are interested in attending this field trip, please fill out the following form, make out a check to the Colorado Scientific Society for $250 per person and send them to: Emmett Evanoff, Department of Earth Sciences, University of Northern Colorado, Greeley, CO, 80639, no later than September 15. You will receive additional information concerning the trip after you register.
| Name: ______________________________ | Address:_________________________________ |
| Phone: _____________________________ | ________________________________________ |
| E-Mail:_____________________________ | _________________________________________ |
| I am interested in attending the following: | Number of Registrants | Amount |
| Gunnison Field Trip,September 22-25, $250/person | __________ | __________ |
| Additional cost of a single room (an additional $95) | __________ | |
| Total Amount Enclosed: | __________ | |
| (make your check out to the Colorado Scientific Society) | __________ |
| Name: ______________________________ | Address:_________________________________ |
| Phone: _____________________________ | ________________________________________ |
| E-Mail:_____________________________ | _________________________________________ |
Denver Gem and Mineral Show, Sep 16, 17, 18, Denver Merchandise Mart, 58th and I-25.
Friends of Mineralogy, USGS, and CSM Geology Museum present “Mineral symposium on agate and cryptocrystalline quartz” at Green Center, CSM, Sept 10, 11, $40. Field trips Sep 12, 13, free (Central City, N. Table Mountain). Contact Pete Modreski, USGS, 303-202-4766, pmodreski@usgs.gov, or Tom Michalski, 303-202-4852, tmichalski@usgs.gov.
Denver Mining Club meets every Monday (except when noted) at Country Buffet near Bowles and Wadsworth (at 8100 W. Crestline Ave.) 11:30 a.m.-1:00 p.m. Sep 12, Paul Jones, St Andrews Goldfield, "Gold exploration and mining activities in Canada and Alaska". Sep 26, Duane Richards, Western Fuels Ass., "Production and marketing of western coal". http://china-resouces.net
Denver International Petroleum Society meets the 2nd Friday of each month at the Wynkoop Brewing Co., 18th and Wynkoop Streets. Reception begins at 11:30 a.m., luncheon at 12 p.m., program at 12:30 p.m. Make reservations (required) by leaving message at (303) 623-5396. Reservations accepted after 8 a.m. on Friday until 10:30 a.m. on Wednesday prior to the meeting. Cancellations accepted until 11:00 am Wednesday prior to the meeting. Cost: $15 for lunches; talk only is available for $2 (make checks payable to "D.I.P.S."). Contact Keith Murray at (303) 986-8554 for information.
Denver Region Exploration Geologists' Society (DREGS) meets in the Mutual Consolidated Water Building, 12700 West 27th Avenue, Lakewood. Social hour 6:00-7:00 p.m. Technical presentation at 7:00 p.m. Meetings are normally scheduled for the first Monday of each month. Sep 12, Andreas Dietrich, CSM, "Bulk rock and melt inclusion geochemistry of Bolivian tin porphyry systems." For information contact Jim Piper, (303) 932-0134, or the website http://www.dregs.org/.
Denver Well Logging Society (DWLS) meets on the third Tuesday of each month, Sept. through May. Lunch and a technical talk at the Wynkoop Brewery begins at 11:30 a.m., 18th and Wynkoop Sts. in Denver. Subject matter usually deals with the application of well logs to oil and gas exploration. Call Elice Wickham at 303-573-2781 for reservations. Web page: http://dwls.spwla.org/.
Rocky Mountain Association of Geologists (RMAG) Reception at 11:30 a.m., lunch at 12:00 p.m., talk at 12:30 p.m. Reservations are taken by recording at 303-623-5396 until 10:30 a.m., Wed. before the luncheon. Cancellations are taken until 11:00 a.m. on Wed. at 303-573-8621. Luncheon cost is $20 payable to RMAG at the door. Reservations are not required for talk only---cost is $3. Meeting location: Denver Petroleum Club, Anaconda Tower, 555-17th St, 37th floor. Web page: http://www.rmag.org.
Rocky Mountain SEPM Reception at 11:30, lunch at noon, speaker at 12:30. Reservations, Dave Uhl:303-389-5092 before noon of preceding Friday. $15.00 lunch, $3 talk only. Wynkoop Brewing Company, 1634 18th St., Denver. David.uhl@EnCana.com Co-AIPG11:30-social, noon-1:30-lunch and speaker. Cost-$25. University Club, 1673 Sherman St., Denver. Reservations: Tom Cavanaugh, 303-458-5550,tcavanaugh@ascg.com. May 3, Kathleen Curry, state representative, "Current Water legislation in the Colorado General Assembly."
University of Colorado at Boulder, Geological Sciences Colloquium Wednesdays, 4:00-5:30 p.m., Rm. 180. Refreshments at 3:30 p.m on the 3rd floor. For info., call 303-492-8141. Web page: http://www.colorado.edu/GeolSci/.
Colorado State University, Dept of Geosciences, Rm 320 Natural Resources Bldg, 4:10 pm. 970-491-5661. www.cnr.colostate.edu/geo/seminars/fall2005.html
Friends of Dinosaur Ridge Web page: http://www.dinoridge.org/. Admission is free, but donations are welcome. For more information, please contact the FODR Visitor Center at (303) 697-3466.
Colorado School of Mines Van Tuyl Lectures Fridays 3:00 p.m. to 4:00 p.m. in Berthoud Hall, room 108. Sep 9, Paul Heller, "Late Cenozoic tilt of the Rky Mtns". Sep 30, Amir Sagy, "Shatter cones and extraterrestrial impact". http://www.mines.edu/academic/geology.html
USGS Geologic Division Colloquium Thursdays, 1:30 p.m., Foord Rm., Building 20, entrance W3, Denver Federal Center. Contact Pete J. Modreski, U.S. Geological Survey, Denver Colorado tel. 303-202-4766, fax 303-202-4767, email:pmodreski@usgs.gov
Western Interior Paleontological Society, Ricketson Auditorium, Denver Museum of Nature and Science, 7 p.m. Free www.wipsppc.com or call 303-663-5868.
For a constantly updated, online geo-calendar, visit the Colorado Geological Survey at: