HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Full Text (PDF) Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Straub, K. M. Articles by George, T. GeoRef GeoRef Citation

Compensational Stacking of Channelized Sedimentary Deposits

¹ Department of Geology and Geophysics, St Anthony Falls Laboratory, University of Minnesota, Minneapolis, Minnesota 55414, U.S.A.; present address: Department of Earth and Environmental Sciences, Tulane University, New Orleans, Louisiana 70118, U.S.A.; kmstraub{at}tulane.edu
² Department of Geology and Geophysics, St Anthony Falls Laboratory, University of Minnesota, Minneapolis, Minnesota 55414, U.S.A.
³ Department of Geological Sciences, The University of Texas at Austin, Austin, Texas 78712, U.S.A.
⁴ Department of Geology and Geophysics, St Anthony Falls Laboratory, University of Minnesota, Minneapolis, Minnesota 55414, U.S.A.; present address: Shell International Exploration and Production, Inc., Houston, Texas 77001, U.S.A.
⁵ Department of Geological Sciences, The University of Texas at Austin, Austin, Texas 78712, U.S.A.; present address: ConocoPhillips Company, Houston, Texas 77079, U.S.A.

Compensational stacking, the tendency for sediment transport systems to preferentially fill topographic lows through deposition, is a concept widely used in the interpretation of the stratigraphic record. We propose a metric to quantify the degree of compensation by comparing observed stacking patterns in subsiding basins to what would be expected from uncorrelated random stacking. This method uses the rate of decay of spatial variability in sedimentation between picked depositional horizons with increasing vertical stratigraphic averaging distance. We present data from six sedimentary basins where this decay can be measured. The depositional environments range from river deltas to deep-water minibasins, and scales range from meters to 1.5 km in thickness. The decrease in standard deviation of sedimentation divided by subsidence with increasing vertical averaging distance is well described by a power law in each study basin. We term the exponent in this power law the compensation index, ; its value is 0.5 for uncorrelated random stacking and 1.0 for perfect compensational stacking. Values less than 0.5 indicate anti-compensation, i.e., a tendency of depositional units to stack on top of one another. Parameters controlling the magnitude of include the frequency of system-scale avulsions and the temporal variability in deposition rates. Data describing the decay in the standard deviation of sedimentation/subsidence from the six studied basins collapse approximately onto a single power-law trend with = 0.75 when the measurement window is standardized by the mean channel depth of each system. Channel depth thus emerges as a fundamental length scale in stratigraphic architecture across environments. Although further study will likely reveal measurable variability in between depositional environments, the overall power-law collapse presented here suggests that a stacking behavior midway between purely random and perfect compensation is a good starting point in quantitatively estimating the stratigraphic arrangement of sedimentary deposits.