Previous editions of newsletter, and PDF versions.
Emmons Lecture - Kinematic & Erosional Histories of the Nepalese Himalayan Fold-Thrust Belt: Implications for Mid-Crustal Channel Flow
Detrital U-Pb zircon ages, Nd-isotopic data, and conventional petrographic data from foreland basin deposits in Nepal show no evidence of erosion of Tibetan mid-crustal rocks from Eocene to modern times. Conspicuously absent are Cretaceous zircons, juvenile Nd, and volcanic lithic grains, all of which would be expected derivatives from middle crust of the Lhasa terrane in southern Tibet. In view of the fact that Greater Himalayan rocks were transported >150 km southward during Early Miocene time, this indicates that MCCF, if it exists in the Nepalese Himalaya, must be confined to Indian material. Although Greater Himalayan age zircons, Nd-isotopic signatures, and abundant plagioclase appear in the detrital record ca. 22-20 Ma, there is no evidence for erosion of Greater Himalayan medium- to high-grade metamorphic rocks until Late Miocene time (11 Ma). Structural data indicate that the Greater Himalayan rocks were emplaced by the MCT along an extensive regional flat upon essentially undeformed (but metamorphosed) lower Lesser Himalayan rocks, and the present position of the Greater Himalayan topographic front is not coincident with the southward extent of the original MCT sheet. The present, steeply northward-dipping surface outcrop pattern of Greater Himalayan rocks in central and western Nepal resulted from erosion into a regional scale antiformal duplex in Lesser Himalayan rocks that began to develop in Late Miocene time. Thus, the presently configured erosional porthole could not have begun to exist until the Late Miocene. The structural facing directions of Lesser Himalayan rocks below the MCT (the floor of the channel) are consistently upright and northward, precluding turbulent mixing along the base of the channel.
A variety of datasets support the following kinematic history of the Himalayan fold-thrust belt: Eocene-Oligocene thrusting in the Tibetan Himalaya, accompanied by amphibolite-grade metamorphism in the underlying Greater Himalayan rocks; Early Miocene emplacement of the MCT sheet and contemporaneous, but much lesser magnitude, northward slip on the STD; Middle-Late Miocene (post-12 Ma) emplacement of the Ramgarh thrust sheet; Late Miocene growth of the Lesser Himalayan duplex; Pliocene-Pleistocene slip on the Main Boundary thrust; and Pleistocene-Recent slip on thrusts within the frontal Subhimalayan imbricate belt. Considered alongside the detrital unroofing record, this kinematic history is incompatible with large-scale involvement of Tibetan middle crust in channel flow as currently articulated in the literature. Features often considered as diagnostic of MCCF in the Himalaya (such as ductile shear strain and out of sequence thrusting) are equally compatible with critical taper models of thrust belt behavior. On the other hand, a modified MCCF model involving only Indian material south of the Indus suture zone since mid- to Late Miocene time may be compatible with geological data as well as conventional kinematic models for thrust belts.
The Colorado Scientific Society needs your help. We have several opportunities to help on committees. From meeting and scheduling the excellent speakers, to helping choose and organize the fabulous field trips, to helping with family night, student presentation night and outreach. We can each give back a little effort as part of a committee, so no one has to contribute all of the effort to keep us going. Please contact me if you are willing to pitch in a bit, and let me know what kinds of things you’d like to do. We have outstanding and enthusiastic people to work with but we need more.
We are starting another new year! Time to get started on making 2006 a great one. If we don’t, no one will. The Colorado Scientific Society needs your help this year
If you have not yet paid your dues for 2006, the submittal form is on the next page. Thanks!
2005 DUES & FUNDS CONTRIBUTIONS COLORADO SCIENTIFIC SOCIETY
Last Name: __________________________________________
First Name: __________________________________________
Initial: __________________________________________
Current email, if available: __________________________________________
DUES: Dues are for the calendar year (January-December)
Regular Members ($20, CO Front Range) ___________________________
Corresponding Members ($10) ___________________________
Student Members ($5, enrolled in college) ___________________________
MEMORIAL FUNDS: These funds support earth-science research grants to graduate students
throughout the nation. If your contribution is not specified, it will be distributed equally among the funds:
(A) Ogden Tweto Memorial Fund ___________________________________
(B) Steven Oriel Memorial Fund ___________________________________
(C) Edwin Eckel Memorial Fund ___________________________________
(D) Bill Pierce-Heart Mountain Fund ________________________________
(E) George Snyder Memorial Fund __________________________________
This contribution is made in the memory of: _______________________________________________________________
ENDOWMENT FUND: This fund is used to support the Society’s monthly meetings and newsletter,
field trips, family night, annual Emmons Lecture, and special activities.
_______________________________________
TOTAL CONTRIBUTIONS (DUES AND FUNDS):
________________________________________
Please make your checks payable to the Colorado Scientific Society
Send this form & your check to:
Colorado Scientific Society
P.O.Box 150495
Lakewood,CO 80215-0495
Colorado Scientific Society’s regular meetings are held the 3rd Thursday of the month at the American Mountaineering Center in Golden (unless otherwise advertised). Social time begins at 6:30 p.m. and talks start at 7:00 p.m. For more information, contact Chuck Kluth at 303- 904-2939, kluth@earthlink.net
Denver Mining Club meets every Monday (except when noted) at Country Buffet near Bowles and Wadsworth (at 8100 W. Crestline Ave., Littleton) 11:30 a.m.-1:00 p.m. Jan 9, “Ingots—Footprints in metal-mining history”, by Fred Barnard, Western Mineral Appraisers. Jan 16, “The future of renewable energy”, by Irena Bulkley-Hopkins, NREL. Jan 23, “Win some, lose some: the evolution of miling practice on the Comstock Lode”, by Gene Michal, AMAX. Jan 30, “Metallica – an overview”, by Richard Hall, President, Metallica Resources. http://china-resources.net.http://china-resources.net
CSM SEG Student Chapter, Feb 10-11, Short course—Diamonds, by Dr. Karin Hoal, CSM Geology Museum, 13th and Maple, 8:30-4:30.
Colorado AIPG December and annual meeting Reception at 11:30; lunch and speaker, noon to 1:30. University Club, 1673 Sherman St, Denver. Jan 17, “The Alamo impact breccia of Nevada and the quest for the crater”, by Dr. John Warme, CSM. $23 w/ advance reservation, $25 at door. Contact Tom Cavanaugh by C.O.B. on December 9 for reservations at 303-425-1125 or at cavtrac@comcast.net or tcavanaugh@ogenvironmental.com.
Denver International Petroleum Society meets the second Friday of each month at the Wynkoop Brewing Co., 18th and Wynkoop Streets. Reception at 11:30 a.m., lunch at noon, talk at 12:30 p.m. Make reservations (required) by leaving message at (303) 623-5396. Reservations accepted until 10:30 a.m. on Wed prior to the meeting. Cancellations accepted until 11:00 am Wed prior to the meeting. Cost: $15 for lunches; talk only-$2. Contact Keith Murray at (303) 986-8554 for info.
Denver Region Exploration Geologists’ Society (DREGS) meets in the Mutual Consolidated Water Building, 12700 West 27th Avenue, Lakewood. Social hour 6:00-6:30 p.m. Technical presentation at 6:30 p.m. Meetings are normally the first Monday of each month. Jan 9, “Worldwide Uranium Resources”, by Dr. Karen Wenrich, Wenrich Consulting for U. For information contact Jim Piper, (303) 932-0137, 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 noon., 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. Talk only (no reservations)—$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.
University of Colorado at Boulder, Geological Sciences Colloquium Wednesdays, 4:00-5:30 p.m., Rm. 180. Refreshments at 3:30 pm on the 3rd floor. For more information, call 303-492-8141. Web page: http://www.colorado.edu/GeolSci
Friends of Dinosaur Ridge Fireside chats resume in the fall. Web page: http://www.dinoridge.orgAdmission 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 from 3:00 p.m. to 4:00p.m. in Berthoud Hall room 108. For further information, check http://www.mines.edu/academic/geology/calendar
USGS Geologic Division Colloquium. Thursdays, 1:30 p.m., Foord Room, Building 20, Denver Federal Center. For more information contact: Peter J. Modreski, U.S. Geological Survey, Denver, Colorado tel. 303-202-4766, fax 303-202-4767 email pmodreski@usgs.gov.
For a constantly updated, online geo-calendar, visit the Colorado Geological Survey at: