Unconformity related and deep burial diagenesis, Upper Knox carbonates, southern and central Appalachians
Early cemented Upper Knox (pre-unconformity) carbonates appear to have escaped much subsequent diagenesis, possibly due to early loss of permeability. A regional unconfined aquifer system accompanied the Knox unconformity,from which it was sourced. Waters moving rapidly by free flow through developing cavern systems, were undersaturated with respect to both aragonite and calcite resulting in large scale dissolution of limestone interbeds and development of interstratal-karstic collapse breccias. Localized concentrations of intrastratal karst below the unconformity may relate to a paleowater table or a paleo-mixing zone. Aquifer stagnation and precipitation of Fe and Mn-rich cements probably accompanied Middle Ordovician transgression and subsequent sedimentation. Middle Ordovician uplift along the eastern basin margin generated tectonic highlands that sourced meteoric fluids which moved downdip in a confined aquifer, flushing earlier stagnant porewater depositing a second generation of nonluminescent cement. Increasing burial beneath thick foreland basin clastics resulted in aquifer stagnation and dull cement precipitation. Episodic dewatering of Appalachian basinal shales was accompanied by rapid migration of warm, saline brines. Fluids moving along earlier intrastratal karstic conduits resulted in localized dissolution of carbonates and massive brecciation of intrastratal karst fills. Major porosity reduction occurred by precipitation of Fe-poor saddle dolomite, locally interstratified with sphalerite and associated minor hydrocarbons. Latest cements are minor Fe-rich calcite and silica.
- Research Organization:
- Virginia Tech, Blacksburg (USA)
- OSTI ID:
- 6458759
- Report Number(s):
- CONF-8510489-
- Journal Information:
- Geol. Soc. Am., Abstr. Programs; (United States), Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Vol. 17; ISSN GAAPB
- Country of Publication:
- United States
- Language:
- English
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Unconformity-sourced aquifer cements and later burial cements, Mississippian limestone, Kentucky and Virginia
Knox unconformity in subsurface of northern Ohio
Related Subjects
580400* -- Geochemistry-- (-1989)
ALKALINE EARTH METAL COMPOUNDS
APPALACHIAN MOUNTAINS
AQUIFERS
ARAGONITE
CALCITE
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBONATE MINERALS
CARBONATE ROCKS
CARBONATES
CHEMICAL REACTIONS
DIAGENESIS
DISSOLUTION
FEDERAL REGION III
FEDERAL REGION IV
GEOLOGIC FORMATIONS
GEOLOGIC HISTORY
GROUND WATER
HYDROGEN COMPOUNDS
MINERALS
MOUNTAINS
NORTH AMERICA
OXYGEN COMPOUNDS
PERMEABILITY
POROSITY
PRECIPITATION
ROCK-FLUID INTERACTIONS
ROCKS
SEDIMENTARY ROCKS
SEPARATION PROCESSES
TENNESSEE
USA
VIRGINIA
WATER