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Book Chapter

Initiation of Upward-Moving Gravity Structures

By
Published:
January 01, 1984

Abstract

True (Newtonian) liquids will rise spontaneously by buoyancy if a density inversion exists even from a perfectly flat source layer. But for solids to rise, some kind of imperfection is required to trigger growth, even though the source layer is potentially mobile.

This heterogeneity can be either in the source layer (the mother layer of buoyant material) or in its overburden. Lateral variations in thickness, density, viscosity, or temperature can all initiate upward movement of a buoyant source layer. Some geologic heterogeneities in the source layer are listed below.

Initial heterogeneities can be present in a salt layer as a result of accumulation in a graben in a rifted terrane or as a result of lateral facies changes (fig. 1). Heterogeneities may be imposed by faulting or folding of the source layer. Faulting can be basement involved or thin-skinned, as discussed in unit 10 (fig. 1). In each case the diapir is likely to form on the upthrown side of the fault where the load is less. Detached faults usually sole out within the ductile source layer, whether this is salt or shale.

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AAPG Continuing Education Course Notes Series

Structural and Depositional Styles of Gulf Coast Tertiary Continental Margins: Application to Hydrocarbon Exploration

Martin P.A. Jackson
Martin P.A. Jackson
Bureau of Economic Geology, The University of Texas at Austin
Search for other works by this author on:
William E. Galloway
William E. Galloway
Bureau of Economic Geology, The University of Texas at Austin
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American Association of Petroleum Geologists
Volume
25
ISBN electronic:
9781629811543
Publication date:
January 01, 1984

GeoRef

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