HR: 1330h
AN: T43A-01    [Abstracts]
TI: Seismic Reflections in a Materially Uniform Sedimentary System
AU: * Tono, H L
EM: henrique.tono@duke.edu
AF: Duke University, Division of Earth and Ocean Sciences 103 Old Chemistry Box 90229, Durham, NC 27708 United States
AU: Pratson, L F
EM: lincoln.pratson@duke.edu
AF: Duke University, Division of Earth and Ocean Sciences 103 Old Chemistry Box 90229, Durham, NC 27708 United States
AB: Following the rules of sequence stratigraphy, seismic profile interpreters regularly encounter reflections that are associated with sequence timeline boundaries, whereas from a physical standpoint they represent acoustic boundaries. What produces reflections from materially uniform sections where no contrasts in bulk material impedances exist? In an attempt to understand whether grain size sorting associated with sediment deposition can create physical conditions resulting in discrete changes in acoustic impedance, we undertook a laboratory investigation of seismic reflections from time-separated and grain size controlled sediment deposits. Two-layer deposits were created in several separate tanks by introducing two, time separated, pulses of sediment. The bulk properties of the sediments were identical, including their grain size distributions. In sediments with narrow distributions only weak reflectors are observed. In sediments with increasing broader distributions of grain sizes, increasingly stronger reflections were observed, with the distribution width correlating with the reflection amplitude. Evidently, the more heterogeneous in terms of grain size an otherwise uniform package of sediments is, the more likely it is to yield timeline associated reflections, indicating that sedimentary processes can create events that are both timelines and acoustic boundaries.
DE: 0935 Seismic methods (3025)
DE: 5102 Acoustic properties
SC: Tectonophysics [T]
MN: 2005 Joint Assembly