Abstract: Carbonate Porosity Modification by Halite Impregnation and Dissolution in Devonian of Saskatchewan
A. C. Kendall, C. E. Dunn
Carbonate porosity in the Dawson Bay and lower Souris River (Davidson Member) Formation is to be avoided in Saskatchewan, for it allows water access to the underlying Prairie Evaporite, rendering potash extraction hazardous. The Dawson Bay and Davidson units are depositional cycles terminating with bedded halites. Porosity is salt plugged beneath these halite beds but commonly is open beyond their limits. Where halite has been dissolved, the former halite plugging has preserved prehalite porosity from late diagenetic modification. Halite introduction was also responsible for some porosity formation.
Carbonate deposits suffered partial synsedimentary lithification with formation of nodular or mottled limestones. Later diagenetic displacive-halite growth was restricted to unlithified-nodule matrices and burrow fills, indicating that halite introduction also was early diagenetic. Halite-moldic porosity is present where halite has been dissolved.
Molds created by synsedimentary dissolution of aragonite shells are halite plugged but beyond regions of halite impregnation the shell molds are filled by late-diagenetic carbonate cement. Unlithified parts of the sediment suffered severe compaction prior to halite impregnation despite very shallow sediment overburden. Halite-impregnated sediments largely are undolomitized but those marginal to bedded halites may be affected markedly. Halite impregnation prevented access of the dolomitizing brines.
AAPG Search and Discovery Article #90968©1977 AAPG-SEPM Annual Convention and Exhibition, Washington, DC