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Title: Diapirs and Salt Domes The Mechanism of Formation.


Abstract not provided.

Publication Date:
Research Org.:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org.:
USDOE Office of Fossil Energy (FE), Petroleum Reserves (FE-40)
OSTI Identifier:
Report Number(s):
DOE Contract Number:
Resource Type:
Resource Relation:
Conference: Proposed for presentation at the Solution Mining Research Institute 2015 Spring Conference held April 26-29, 2015 in Rochester, NY.
Country of Publication:
United States

Citation Formats

Lord, Anna C. Snider. Diapirs and Salt Domes The Mechanism of Formation.. United States: N. p., 2015. Web.
Lord, Anna C. Snider. Diapirs and Salt Domes The Mechanism of Formation.. United States.
Lord, Anna C. Snider. 2015. "Diapirs and Salt Domes The Mechanism of Formation.". United States. doi:.
title = {Diapirs and Salt Domes The Mechanism of Formation.},
author = {Lord, Anna C. Snider},
abstractNote = {Abstract not provided.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2015,
month = 3

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  • Remnant magnetization of stratiform sulfides within salt dome cap rocks provides a means of dating the timing of mineralization and its relationship with tectonic, sedimentation, and fluid evolution events within the local basin. The Winnfield salt dome in northern Louisiana hosts stratiform laminae of pyrrhotite and other sulfides in anhydrite cap rock. Detailed paleomagnetic analyses indicate the presence of numerous magnetic reversals that can be correlated with the sea-floor magnetic anomaly sequence, thus providing the first direct determination of a salt dome cap rock formation age. The sampled section that represents about two thirds of the total anhydrite thickness formedmore » between 157 and 145 Ma (latest Jurassic). Accumulation rates calculated from these data indicate that the average rate for the oldest cap rock sampled is 5.7 m/m.y. and decreases to 2.8 m/m.y. for the younger strata. The Winnfield diapiric salt contains about 3% anhydrite, indicating the diapir growth rate was at least 30 times faster, a figure that is compatible with independent geologic estimates. The best documented cap rock-hosted sulfide concentrations occur at the Hockley salt dome in south-central Texas. Hockley is a relatively young diapir with the cap rock believed to have developed within the last 45 ma. Sulfides occur throughout the 285-m thick cap rock, but major metal concentrations occur within a 20-m zone within the central cap rock stratigraphy. If this zone formed at comparable rates to the Winnfield cap rock, then the main pulse of Hockley mineralization lasted only a few million years. Paleomagnetic studies are in progress to constrain timing of mineralization of Hockley.« less
  • The authors investigated the characteristics of conductive heat flow and the associated temperature distributions around both a highly conductive salt diapir and a salt sheet embedded in a lower conductivity host rock. For the salt sheet, temperatures in the subsalt formations are emphasized. Even relatively thin sheets can cause a significant change in the subsalt temperature; a sheet 1000 m thick can easily give rise to a temperature decrease of 15/degrees/C or more in the underlying formations. Diapiric effects are of similar magnitude.
  • Dry clay models were used to study fault systems that develop in strata above domal uplifts. Contemporaneous deposition and deformation was modeled by incrementally uplifting a model diapir and depositing additional layers of dry clay on the deformed strata. Variables observed to control structural patterns that developed in the arched and extended strata include: (1) the nature of the contact between the model diapir and the overlying strata, (2) the thickness of the pre-uplift sequence, and (3) the rate of sedimentation with respect to the rate of diapir uplift. Boundary conditions between the model diapir and overlying strata proved verymore » critical in controlling fault patterns. Naturally occurring salt diapir-related faults systems seem best duplicated experimentally by allowing the pre-uplift strata to slide passively along the sides of the uplifting diapir, modeling a non-welded contact. With uplift, two related but distinct systems of extensional faults developed above the crest of the model diapir: (1) a surface-breaking graben complex bounding by inward-dipping normal faults and rooted in the upper levels of the pre-uplift strata, and (2) a blind system of normal faults rooted to the crest of the diapir. The surface-breaking graben complex was observed only in experiments with thin pre-uplift sequences (pre-uplift thickness equaled one-half diapir diameter) and intermediate-thickness pre-uplift sequences (pre-uplift thickness equaled one-and-a-half times diapir diameter). In the thin pre-uplift experiments, the graben complexes were rooted to the top of the diapir. In the intermediate thickness pre-uplift experiments, inwards-dipping, graben-bounding normal faults intersected and diverged at depth, forming conjugate fault sets with grabens situated immediately above pyramid-shaped horsts.« less
  • An inverse procedure is used to remove sediments from around salt diapirs in a manner consistent with evolution of the salt diapir, which also is determined self-consistently by the inverse procedure. The corresponding evolving stress and strain of the sediments are then calculated from use of specified Lame constants, and the times and spatial domains identified where the Coulomb-Mohr rock failure criterion is satisfied, thereby yielding estimates of fault and fracture locations. In addition, the combined evolutionary picture is used to assess thermal focusing by the highly conductive evolving salt, so that thermal anomalies in relation to hydrocarbon maturation aroundmore » the evolving salt and structural development of sediment bed upturning and salt overhang evolution can be timed better relative to hydrocarbon emplacement. Several examples from the Gulf of Mexico are analyzed using this new inversion procedure.« less
  • The authors present a new hypothesis for diapir growth in which deposition and extension interact with coeval salt flow. The hypothesis is based on scaled tectonic experiments in which viscous polymers simulated ductile salt and frictional-plastic, dry sand simulated brittle overburden. The model diapirs all grew by downbuilding beneath accumulating overburdens. Without regional extension, sedimentary differential loading causes salt to rise where the overburden is thinnest. The diapir shape depends on the overburden aggradation rate relative to the flow rate of salt up the diapir conduit. With rapid deposition, strata onlap the diapir, which narrows upward and eventually becomes buriedmore » and inactive. With moderate deposition, strata uplap against vertical diapir flanks. With slow deposition, salt spreads by extrusion or shallow intrusion and steeply overrides toplapped strata; the diapir widens upward until salt supply is depleted. With very slow deposition, subhorizontal tongues of salt override toplapped strata. Thin-skinned regional extension initially promotes piercement by tectonic differential loading, but it also impedes upward salt flow by horizontally stretching the diapir. With rapid extension, the diapir sags and is indented by growth faults and overlain by depotroughs. With moderate extension rates, the diapir widens with time and thus narrows upward. Only where extension is very slow can upward-widening or near-vertical diapir walls form. Changes in rates of aggradation, flow, or extension during diapirism can explain complex geometries, such as inverted teardrop shapes, without invoking shrinking stems. Model results are applied to examples from the Gulf of Mexico and other salt regions.« less