Diverse origins and timing of formation of basinal brines in the Gulf of Mexico sedimentary basin

J. S. Hanor, Jennifer McIntosh

Research output: Contribution to journalArticle

37 Citations (Scopus)

Abstract

A review of five different field areas in the Gulf of Mexico sedimentary basin (GOM) illustrates some of the potentially diverse chemical and physical processes which have produced basinal brines. The elevated salinities of most of the formation waters in the GOM are ultimately related to the presence of the Middle Jurassic Louann Salt. Some of these brines likely inherited their salinity from evaporated Mesozoic seawater, while other saline fluids have been produced by subsequent dissolution of salt, some of which is occurring today. The timing of the generation of brines has thus not been restricted to the Middle Jurassic. The mechanisms of solute transport that have introduced brines throughout much of the sedimentary section of the GOM are not entirely understood. Free convection driven by spatial variations in formation water temperature and salinity is undoubtedly occurring around some salt structures. However, the driving mechanisms for the broad, diffusive upward solute transport in the northern Gulf rim of Arkansas and northern Louisiana are not known. In the Lower Cretaceous of Texas, fluid flow was much more highly focused, and perhaps episodic. It is clear that many areas of the Gulf basin are hydrologically connected and that large-scale fluid flow, solute transport, and dispersion have occurred. The Na-Mg-Ca-Cl compositions of brines in the areas of the Gulf Coast sedimentary basin reviewed in this article are products of diagenesis and do not reflect the composition of the evaporated marine waters present at the time of sediment deposition. Large differences in Na, Ca, and Mg trends for waters hosted by Mesozoic versus Cenozoic sediments may reflect differences in: (i) the sources of salinity (evaporated seawater for some of the Mesozoic sediments, dissolution of salt for some of the Cenozoic sediments); (ii) sediment lithology (dominantly carbonates for much of the Mesozoic sediments, and dominantly siliciclastics for the Cenozoic sediments); or (iii) residence times of brines associated with these sediments (tens of millions of years versus perhaps days).

Original languageEnglish (US)
Pages (from-to)227-237
Number of pages11
JournalGeofluids
Volume7
Issue number2
DOIs
StatePublished - May 2007

Fingerprint

sedimentary basin
sediment
solute transport
salt
formation water
salinity
fluid flow
Jurassic
dissolution
seawater
gulf
chemical process
diagenesis
residence time
lithology
water temperature
spatial variation
convection
Cretaceous
carbonate

Keywords

  • Basin
  • Brines
  • Gulf of Mexico
  • Salt

ASJC Scopus subject areas

  • Earth and Planetary Sciences(all)

Cite this

Diverse origins and timing of formation of basinal brines in the Gulf of Mexico sedimentary basin. / Hanor, J. S.; McIntosh, Jennifer.

In: Geofluids, Vol. 7, No. 2, 05.2007, p. 227-237.

Research output: Contribution to journalArticle

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