Los Alamos Women in Science
Northern Chapter of the New Mexico Network for
Women in Science and Engineering

Tuesday, March 14, 2000
12:00 am - 1:30 pm, Otowi bldg, room E128, LANL
(2 floors below cafeteria)


TALK at 12:10:
Claudia J. Lewis, EES-1, LANL
"Using Quaternary dating methods, stratigraphy and patterns
of stream incision to constrain models of post-orogenic rock uplift:
Preliminary results from the Ebro basin, Spain"

"In the central Ebro basin (Spain) and adjacent Pyrenees, we are testing models of post-tectonic rock uplift using patterns of stream incision constrained by Quaternary stratigraphic and dating methods. To reveal spatial distribution and rates of incision, we correlate terrace remnants along principal rivers orthogonal to the Pyrenean axis, determine numeric ages, and reconstruct paleo-longitudinal stream profiles for comparison to modern profiles. The large separation between terraces in this area, and their great longitudinal and lateral extent, facilitate mapping and correlation of terrace remnants and measurements of terrace deformation. Because ages are critical for calculating incision rates, we use various Quaternary chronometric methods including radiocarbon, luminescence, and cosmogenic nuclide profile dating, and magnetostratigraphy. We also use time-related trends in soil development on surfaces as a primary means of correlating terrace remnants, since numeric dating techniques are expensive and dateable material relatively rare. We recently completed field descriptions and sampling of a spectacular terrace sequence along the lower Rio Cinca. Broad terrace treads are overlain by <10 m of well-sorted, stratified sandy gravel, suggesting a predominance of strath terraces and therefore age-equivalent terrace treads and deposits. Terrace soils show strong time-related trends related to pedogenic accumulation of calcium carbonate, including carbonate mass, degree of carbonate cementation, thickness and strength of horizonation, and total profile thickness. Soils are clearly invaluable for maximizing age control and developing regional correlations among terrace sequences. Based on general comparisons with soils formed in similar semi-arid environments in the western U.S., we assign tentative age estimates (possibly correlating with glacial outwash events) as follows: T4, 50-80 ka; T5, 150-250 ka; and T8, 600-800 ka. Strath heights of 35-40 m (T4), 55-60 m (T5), and 115-120 m (T8) above the modern channel suggest preliminary incision rates of 0.1-0.8 mm/yr. Ultimately, this project will provide a precise Quaternary chronology, a basin-wide correlation of river terraces, and a model of post-tectonic rock uplift that will prove essential to Quaternary studies on the Iberian peninsula and elsewhere."

"The 20-minute technical talk will be preceded by where I've been and where I'm going."

Nonmembers Welcome!  

Sideroom C is reserved from 11:30 to 1:30 for people who like to eat earlier or later, and informal discussion. You are welcome to come for just the talk at noon, and questions are encouraged!

For driving directions to Otowi bldg (TA-3, building 261) at LANL, see: http://www.lanl.gov/tools/maps
(direct link to map showing the Otowi Building: http://nis-www.lanl.gov/cgi-bin/wthi?ta=3&bldg=261).
Room E128 is on the 1st floor (2 floors below the cafeteria) just south of the stairwell.




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LAWIS Lunch-Time Talk Organizer: Huyen Dinh, dinh@lanl.gov, 665-0737
LAWIS home page: http://home.lanl.gov/lawis
NMNWSE home page: http://www.nmnwse.org