Effects of Asthenosphere Melting, Regional Thermoisostasy, and Sediment Loading on the Thermomechanical Subsidence of Extensional Sedimentary Basins
- Raymond A. Price
Published Online: 18 MAR 2013
Copyright 1989 by the American Geophysical Union
Origin and Evolution of Sedimentary Basins and Their Energy and Mineral Resources
How to Cite
Stephenson, R. A., Nakiboglu, S. M. and Kelly, M. A. (1989) Effects of Asthenosphere Melting, Regional Thermoisostasy, and Sediment Loading on the Thermomechanical Subsidence of Extensional Sedimentary Basins, in Origin and Evolution of Sedimentary Basins and Their Energy and Mineral Resources (ed R. A. Price), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM048p0017
- Published Online: 18 MAR 2013
- Published Print: 1 JAN 1989
Print ISBN: 9780875904528
Online ISBN: 9781118666654
- Sedimentary basins—Congresses;
- Mines and mineral resources—Congresses;
- Power resources—Congresses
The general characteristics of the evolution of many sedimentary basins, especially those found at rifted or sheared continental margins, are conventionally explained by models of crustal subsidence driven by the thermal contraction ofan anomalously hot lithosphere. A rigorous threedimensional thermomechanical model of sedimentary basin formation is examined that comprises a sedimentary basin overlying a thinned, rheologically layered (elastic-viscoelastic) lithosphere in turn overlying an inviscid asthenosphere. Active sediment deposition, at a specified rate, occurs within the overlying basin and the thermal state of the sedimentary basin is fully coupled with that of the lithosphere. Temperatures in the model are governed by the effects of vertical and horizontal thermal conduction such that the lithosphere-asthenosphere boundary is defined as a (partial) melt isotherm or phase change boundary which migrates vertically depending on the transient thermal state. Vertical deformations of the lithosphere result from the purely mechanical effects of sediment loading as well as from changes in the ambient temperature field. The temperature anomalies contribute to these deformations not only by setting up body forces but also by creating thermal in-plane forces and associated bending moments.
Conventional local isostatic and simple elastic plate models of sedimentary loading on a thermally perturbed lithosphere may be inadequate because of the important interactions of thermal and mechanical forces. Several thermomechanical processes inherent to the present model have the tendency to reduce or retard the thermal subsidence mechanism. These include the regional isostatic compensation of the thermal body forces, given regional compensation of the sediment load, and the implicit accompanying effects of the thermal bending moments; lithospheric thickening (or thinning) due to the basal phase change which is accompanied by the introduction (or removal) of latent heat; the displacement of hot asthenospheric material by sedimentary loading; and the insulating effect of the thickening, low thermal conductivity, sedimentary sequence atop the cooling, thickening thermal lithosphere.