Exp Shoreline Trans Regr

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Exp Shoreline Trans Regr
Chris Paola, St. Anthony Falls Laboratory & Dept. of Geology and Geophysics, University of Minnesota; XES 96-1 at the Experimental Earthscape Facility, St. Anthony Falls Hydraulic Laboratory.

*Basin is c. 1.6 m long x 1 m wide, the floor subsides in a sag-like geometry.

*Sediment consists of fine grained quartz and coal sand. The coal sand is less dense it tends to be transported farther out into the basin, acting as a proxy for finer grained sediment in real systems.

*1st segment: Slow base level fall. Absolute base level fall takes place at rates similar to basin subsidence. The geometry and rates of subsidence of the basin floor is balanced such that the shoreline progrades from a zone of relative base-level rise (i.e. absolute base level fall is slower than basin subsidence producing a slow relative rise) into a zone of relative base-level fall (i.e. rate of all of absolute base level is faster than basin subsidence). A nickpoint rapidly cuts headward back to the source. As the nickpoint retreats, the slight increase in sediment supplied just downstream forces deposition. Thus as the knickpoint steps to the right so to does the attendant zone of aggradation. Over time the valley widens into a broad basin-scale unconformity.
See discussion in Heller et al., (2001) Geomorphology and
Sequence Stratigraphy Due To Slow And Rapid Base-level Changes In An Experimental Subsiding Basin (XES 96-1): AAPG Bulletin.

*2nd Segment: Rapid base level fall. Incised valley development during a rapid fall in base level. Key features are labeled. The incised valley that forms in relatively narrow, steep walled, and lengthens basinward as the delta at the valley mouth is incised by continued base level fall. Growth faults develop during base level fall.

*3rd Segment: A block view of the final stratigraphy generated from experiment XES 96-1 is shown, courtesy of Lincoln Pratson, Duke University. This block shows the distribution of ‘sandstone’ (quartz sand, shown in white) and ‘shale’ (actually coal sand seen as black) at the end of the experiment. The parts of the basin fill are labeled.

Fly through: red, blue and green frames relate to cross sections in Heller et al., 2001., the center line, a line 210 mm to the left of the center line (looking downstream), and a line at 370 mm to the left of the center line, respectively. The movie is useful in that you can correlate horizons across the block. For example, you can follow the geometry of growth faults, sequence boundaries or other markers, across the basin.

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Uploaded: Jan24 12
Last Modified: 2012-01-24 11:07:21
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Chris Paola, St. Anthony Falls Laboratory & Dept. of Geology and Geophysics, University of Minnesota;
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