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SUMMARY:SCALING LAWS FOR AGGRADATION AND PROGRADATION  OF THE STRATIGRAPHI
 C RECORD - Peter Sadler\, University of California at Riverside
DTSTART:20120515T153000Z
DTEND:20120515T163000Z
UID:TALK36790@talks.cam.ac.uk
CONTACT:John Maclennan
DESCRIPTION:Aggradation\, progradation and accommodation of stratified sed
 iments are unsteady\, reversible processes.  Their net rates scale inverse
 ly with averaging time.  Although isolated rate determinations have little
  predictive value\, the shapes and slopes of empirical scaling law relatio
 nships between the logarithms of rate and averaging time or the logarithms
  of distance and averaging time reveal properties of the accumulation proc
 ess\, including the contributions of periodic and stochastic components.  
 The intersections\, ratios and products of pairs of scaling laws reveal ch
 aracteristic dimensions of the stratigraphic record.  The negative slope o
 f the scaling law for sediment aggradation steepens with stratigraphic inc
 ompleteness\; i.e. the proportion of time represented by hiatus.  For peri
 tidal carbonates\, the scaling law predicts characteristic hiatus duration
 s at Milankovitch time-scales.  The intersection of two scaling laws revea
 ls the expected time scale at which the rates balance.  Thus\, scaling law
 s for shallow marine aggradation and accommodation intersect at the charac
 teristic time scales of upward-shallowing cyclothems.  The ratio of aggrad
 ation to progradation rates is time scale dependent for floodplains and co
 ntinental shelves.  At averaging times shorter than Milankovitch scales\, 
 progradation shows positive feedback and aggradation has negative feedback
 .  At longer time scales the relationship reverses.  Thus\, the expected s
 hape of composite\, clinoform\, time-stratigraphic units is time- and size
 -scale dependent.  The product of aggradation and progradation rates is se
 diment flux.  For terrigenous passive margins this product is not time sca
 le dependent.  Passive margins may be characterized by a constant expected
  sediment flux at all time- and size-scales from ripples to whole shelves.
   
LOCATION:Harker 1 seminar room\, Department of Earth Sciences
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