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Modeling Hydro-Isostasy: Isostatic Flexure Along the Global Coastlines Due to Previous HitSeaNext Hit-Previous HitLevelNext Hit Rise and Fall

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

Ice Age Previous HitseaNext Hit-Previous HitlevelNext Hit cycles are on the Previous HitorderNext Hit 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 Previous HitseaNext Hit Previous HitlevelNext Hit 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 Previous HitseaNext Hit Previous HitlevelNext Hit are disengaged from changes in relative Previous HitseaNext Hit Previous HitlevelNext Hit. Variations in water loading can change the slopes of continental shelves on the Previous HitorderNext Hit of 30%. Hydro-isostasy adds to the magnitude of a Previous HitseaNext Hit Previous HitlevelNext Hit rise, long after the eustatic component of the Previous HitseaNext Hit Previous HitlevelNext Hit rise has ended. A Previous HitseaNext Hit-Previous HitlevelNext Hit 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 Previous HitseaNext Hit Previous HitlevelNext Hit has a similar effect, but opposite in sign. The wedge-shaped unloading pattern, due to a Previous HitseaNext Hit-Previous HitlevelNext Hit 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 Previous HitseaNext Hit Previous HitlevelNext Hit Previous HitcycleNext Hit. While the water depth of a paleo-shoreline gives an estimate of relative Previous HitseaNext Hit-Previous HitlevelNext Hit change, without an estimate of the amount of deflection at this location, eustatic Previous HitseaNext Hit-Previous HitlevelTop change remains unknown.

 

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