--> Abstract: Modeling Hydro-Isostasy: Isostatic Flexure Along the Global Coastlines Due to Sea-Level Rise and Fall, by Eric W. Hutton and James P. Syvitski; #90078 (2008)

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Modeling Hydro-Isostasy: Isostatic Flexure Along the Global Coastlines Due to Sea-Level Rise and Fall

Eric W. Hutton and James P. Syvitski
U. Colorado at Boulder, Boulder, CO

Ice Age sea-level cycles are on the order of 100 m, causing changes in the overlying load on continental shelves worldwide. These load changes cause the lithosphere to deflect along the Earth’s coastlines. Based on a one-dimensional elastic flexure model, an analytic solution for the deflection of a linear slope, due to sea level rise and fall, is derived. This analytic solution allows a global database of deflection estimates for continental shelves, due to increases in water loading and the shape of LGM continental margins. Thus, changes in eustatic sea level are disengaged from changes in relative sea level. Variations in water loading can change the slopes of continental shelves on the order of 30%. Hydro-isostasy adds to the magnitude of a sea level rise, long after the eustatic component of the sea level rise has ended. A sea-level rise over a continental shelf will produce a wedge-shaped loading pattern that increases from the landward shoreline until it reaches its maximum at the lowstand shoreline. This asymmetric loading pattern causes a steepening of the shelf. A fall in sea level has a similar effect, but opposite in sign. The wedge-shaped unloading pattern, due to a sea-level drop, causes a decrease in shelf gradient and an increase in the total shoreline regression. Quantifying this effect is essential to reconstructing stream gradients, or accommodation estimates through a sea level cycle. While the water depth of a paleo-shoreline gives an estimate of relative sea-level change, without an estimate of the amount of deflection at this location, eustatic sea-level change remains unknown.

 

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas