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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 47 (1963)

Issue: 12. (December)

First Page: 2077

Last Page: 2077

Title: Saline Waters of Sedimentary Rocks: ABSTRACT

Author(s): Donald E. White

Article Type: Meeting abstract


Most saline waters of marine sedimentary rocks were probably similar initially to present-day ocean water. Many early diagenetic changes are closely related to organic content and bacterial activity; ion exchanges and perhaps some other early changes are inorganic.

Recent studies indicate that compaction of sediments and escape of interstitial water begin with deposition and continue for millions of years. Fine-grained sediments behave as semi-permeable membranes, permitting selective escape of water and concentrating dissolved components in remaining pore fluids. With increasing salinity, proportions of some ions also change, especially with calcium increasing relative to sodium. Most explanations favor liquid-solid cation exchange reactions; some evidence also suggests selective escape of Na, carbon dioxide (as HCO3?), boron (as H3BO3?), and possibly ammonium ions. If rates of escape do indeed differ, they are probably related to size and electrical charge of the dissolved hydrated components. Carbonates may di solve as carbon dioxide escapes, increasing calcium in the retained brine. Original ocean water in contact with normal sediments has thus evolved to connate (redefined) or fossil water vastly different in composition, and these changes must be closely related to the origin of petroleum. Rates of migration and evolution depend on the environment.

Chemical and isotopic criteria also clarify the origin of saline waters other than those of normal marine sediments, including connate waters of evaporites; waters of relatively low salinity that have dissolved evaporites; sulphate and bicarbonate waters of oil fields; waters driven from sedimentary rocks during progressive metamorphism; and magmatic waters that have migrated into sedimentary rocks. Relatively complete analyses of waters from oil fields and elsewhere illustrate some of the principles involved, but extensive additional studies are needed.

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