10:30 am - UTIG Seminar Series: Sean Gulick, UTIG
UTIG Seminar Series: Sean Gulick, UTIG
||August 28, 2015 at 10:30 am
||August 28, 2015 at 11:30 am|
| ||Location:||PRC, 10100 Burnet Road, Bldg 196, Rm 1.603, Austin, TX 78758|
| ||Contact:||Sean Gulick, email@example.com, 512-471-0483 |
| ||URL:||Event Link|
"Unroofing the St. Elias Mountains: Quantifying Sediment Flux in an Collisional, Glaciated Margin Using the Deep Sea Record"
Erosion, sediment production and routing on a tectonically active continental margin reflect both tectonic and climatic processes; partitioning the relative importance of these processes remains controversial. Gulf of Alaska contains a preserved sedimentary record of Yakutat Terrane collision with North America. Because tectonic convergence in the coastal St. Elias orogen has been roughly constant for 6 Myr, variations in its eroded sediments preserved in the offshore Surveyor Fan constrain a budget of tectonic material influx, erosion, and sediment output. Seismically imaged sediment volumes calibrated with chronologies derived from Integrated Ocean Drilling Program boreholes shows that erosion accelerated in response to Northern Hemisphere glacial intensification (~2.7 Ma) and that the 900-km long Surveyor Channel inception appears to correlate with this event. However, tectonic influx exceeded integrated sediment efflux over the interval 2.8-1.2 Ma. Volumetric erosion accelerated following the onset of quasi-periodic (~100-kyr) glacial cycles in the mid-Pleistocene climate transition (1.2-0.7 Ma). Since then erosion and transport of material out of the orogen has outpaced tectonic influx by 70-100%. Such a rapid net mass loss explains apparent increases in exhumation rates inferred onshore from exposure dates and mapped out-of-sequence fault patterns. The 1.2 Myr mass budget imbalance must relax back toward equilibrium in balance with tectonic influx over the time scale of orogenic wedge response (Myrs). The St. Elias Range provides a key example of how active orogenic systems respond to transient mass fluxes, and the possible influence climate driven erosive processes that diverge from equilibrium on the million-year scale.