HR: 09:00h
AN: G21D-05 INVITED     [Abstracts]
TI: Late Pleistocene sedimentation increase in the Gulf of Mexico and modeling of time-dependent long-wavelength flexural subsidence
AU: * Ivins, E R
EM: eri@fryxell.jpl.nasa.gov
AF: JPL/Caltech, MS 300-233 JPL/Caltech 4800 Oak Grove Dr., Pasadena, CA 91109-8099 United States
AU: Blom, R G
EM: ronald.blom@jpl.nasa.gov
AF: JPL/Caltech, MS 300-233 JPL/Caltech 4800 Oak Grove Dr., Pasadena, CA 91109-8099 United States
AU: Wu, X
EM: Xiaoping.Wu@jpl.nasa.gov
AF: JPL/Caltech, MS 300-233 JPL/Caltech 4800 Oak Grove Dr., Pasadena, CA 91109-8099 United States
AU: Dokka, R
EM: rkdokka@c4g.lsu.edu
AF: Louisiana Spatial Reference Center and Center for GeoInformatics, Louisiana State University, Baton Rouge, LA 70803 United States
AB: Global climate change occurring near the transition from Pliocene to Pleistocene epochs is the most likely source for increased rates of sedimentary deposition into the world's catchment basins. During the Pleistocene the periodicity in sedimentation rate has periods of roughly 20,000, 41,000 and 100,000 years: having a distinct fingerprint of the Milankovich orbital forcing periods (Molnar 2004). We model the forcing of the time-dependent flexure of the Gulf of Mexico by continent-wide sediment transport rate variability over the past 4 Ma. Reconstructions of changes in sediment dispersal occurring during the Late Cenozoic indicate that glacioeustasy also plays a significant role along the shore of the Northern Gulf of Mexico Basin (Galloway 2001). We employ both spherically layered and gravitating viscoelastic half-space models employing an elastic lithosphere and using Maxwell time constants that are tuned to both regional and global seismic tomography. The latter data are consistent with a rheologically stiffer than average sub-crustal environment. Hydroisostatic loading is also included in the modeling. Paleosealevel indicators, tide gauges and recent GPS results provide rich data sources for inverse modeling of the load history and solid earth rheology. The sediment rate changes are modeled, in part, as pulsed great megaflood erosional events known to be active during Glacial to Interglacial transitions (Brown and Kennett 1998). Although the model is relatively crude in both space and time, preliminary results indicate that the subsidence rate caused by long-term sedimentary changes could sustain subsidence rates of 1 - 10 mm/yr during the past 5,000 years over many hundreds of kilometers of coastline. We also discuss the gravity change and self-gravitationally induced sea level variability predicted by the models. Refinement of such modeling in space and time is a major challenge for the future. However, long-wavelength analysis of ongoing Gulf vertical motions complement the study of more local phenomenon, wherein anthropogenic-related subsidence, growth fault-related land motion and sediment compaction may drive a very concentrated large-amplitude subsidence at present-day.
DE: 1211 Non-tectonic deformation
DE: 1605 Abrupt/rapid climate change (4901, 8408)
DE: 1641 Sea level change (1222, 1225, 4556)
DE: 1862 Sediment transport (4558)
DE: 7218 Lithosphere (1236)
SC: Geodesy [G]
MN: Fall Meeting 2005