ISOSTATIC BALANCE DURING SEDIMENT LOADING AND UNLOADING IN CONTINENTAL MARGINS

The initiation of a sedimentary basin may be explained by a mechanism which is related to global tectonics and sea-floor spreading. Once the initial shape of a basin is formed, the sediments which were removed and transported from the nearby inland area will be deposited in the basin, where active burial and compaction take place under conditions of isostatic balance.
Cambining concepts of isostasy and sediment compaction, both the subsidence of the crust and the rise or fall of the sedimentary surface in a continental margin basin can be estimated. The first model proposed is here applied to four major basins–the Mississippi, Mackenzie, Niger and Amazon. The sedimentary surface, in general, tends to rise as the radio of depositional area to erosional area decreases and/or porosity at the base of the sedimentary basin increases (undercompaction).
The second model proposed may be applicable for areas of carbonate sedimentation; deposition takes place primarily by chemical and biological processes, regardless of inland erosion.