HR: 09:45h
AN: G11B-08 INVITED     [Abstracts]
TI: Relative geomorphic surface chronology measured by high-resolution LIDAR topography
AU: * Perg, L A
EM: lperg@umn.edu
AF: National Center for Earth-surface Dynamics, Department of Geology and Geophysics, University of Minnesota-Twin Cities, 310 Pillsbury Dr. SE, Minneapolis, MN 55455 United States
AU: Oskin, M E
EM: oskin@unc.edu
AF: University of North Carolina-Chapel Hill, Department of Geological Sciences, Campus Box #3315, Mitchell Hall, Chapel Hill, NC 27599 United States
AU: Blumentritt, D J
EM: blum0123@umn.edu
AF: National Center for Earth-surface Dynamics, Department of Geology and Geophysics, University of Minnesota-Twin Cities, 310 Pillsbury Dr. SE, Minneapolis, MN 55455 United States
AB: LIDAR is a potential tool to establish the relative chronology of geomorphic surfaces over a broad spatial area, with benefit to Quaternary research. Diffusive processes, such as creep, progressively smooth landscapes through time. Detailed elevation data can quantify this smoothing over different topographic wavelengths, and chronologically equivalent surfaces could thus be identified and mapped. Unlike spectral imaging, which relies on weathering changes, LIDAR chronosurfaces could be identified over areas of differing lithology. However, LIDAR chronosurfaces may be adversely impacted by large grain size differences that influence diffusion rates. To accomplish the goal of quantifying surface roughness over time requires first that the relative error within a LIDAR swath and between LIDAR swathes be better understood to determine the minimum resolvable surface feature amplitude and wavelength. One approach to measuring roughness is to sample data collected in the same swath, which minimizes error in instrument location but has the disadvantage of a fixed orientation relative to topographic features; the actual amplitude would need to be calculated in an oblique transect. The other approach is to sample data along an optimal azimuth, which could result in a mismatch in elevations between individual swaths of LIDAR data. Combining LIDAR chronosurface maps with the traditional tools of fieldwork and numerical dating would provide an age model over a broader area than that mapped in the field, along with an additional chronology check. Absolute dating methods (e.g. $^{14}$C, cosmogenic nuclides) are expensive; the chronosurface map provides a framework to develop the most parsimonious dating strategy. Sparser initial sampling for absolute dates reserves resources to more densely sample areas with ambiguous chronosurfaces and to revisit areas with unexpected numerical dates.
DE: 1815 Erosion and sedimentation
DE: 1824 Geomorphology (1625)
DE: 1894 Instruments and techniques
DE: 1294 Instruments and techniques
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting