Insights into the dolomitization process and porosity modification in sucrosic dolostones, Avon Park Formation (Middle Eocene), East-Central Florida, U.S.A.

Handle URI:
http://hdl.handle.net/10754/561729
Title:
Insights into the dolomitization process and porosity modification in sucrosic dolostones, Avon Park Formation (Middle Eocene), East-Central Florida, U.S.A.
Authors:
Maliva,, Robert G.; Budd, David A.; Clayton, Edward A.; Missimer, Thomas M.; Dickson, John Anthony D
Abstract:
The Avon Park Formation (middle Eocene) in central Florida, U.S.A., contains shallow-water carbonates that have been replaced by dolomite to varying degrees, ranging from partially replaced limestones, to highly porous sucrosic dolostones, to, less commonly, low-porosity dense dolostones. The relationships between dolomitization and porosity and permeability were studied focusing on three 305-m-long cores taken in the City of Daytona Beach. Stable-isotope data from pure dolostones (mean δ 18O = +3.91% V-PDB) indicate dolomite precipitation in Eocene penesaline pore waters, which would be expected to have been at or above saturation with respect to calcite. Nuclear magnetic log-derived porosity and permeability data indicate that dolomitization did not materially change total porosity values at the bed and formation scale, but did result in a general increase in pore size and an associated substantial increase in permeability compared to limestone precursors. Dolomitization differentially affects the porosity and permeability of carbonate strata on the scale of individual crystals, beds, and formations. At the crystal scale, dolomitization occurs in a volume-for-volume manner in which the space occupied by the former porous calcium carbonate is replaced by a solid dolomite crystal with an associated reduction in porosity. Dolomite crystal precipitation was principally responsible for calcite dissolution both at the actual site of dolomite crystal growth and in the adjoining rock mass. Carbonate is passively scavenged from the formation, which results in no significant porosity change at the formation scale. Moldic pores after allochems formed mainly in beds that experienced high degrees of dolomitization, which demonstrates the intimate association of the dolomitization process with carbonate dissolution. The model of force of crystallization-controlled replacement provides a plausible explanation for key observations concerning the dolomitization process in the Avon Park Formation and elsewhere: (1) volume-for-volume replacement at a crystal scale, (2) coupled growth of dolomite crystals and dissolution of host calcium carbonate matrix, and (3) automorphic replacement by euhedral dolomite crystals. The force-of-crystallization model also does not require an influx of externally derived water that is undersaturated with respect to calcite to dissolve calcite, a fact that could simplify diagenetic models of porosity generation in dolostones. The later addition of external carbonate can result in a substantial reduction in porosity by the precipitation of dolomite cement, which could convert a high porosity sucrosic dolostone into a dense "Paleozoic type" dolostone. Copyright © 2011, SEPM (Society for Sedimentary Geology).
KAUST Department:
Water Desalination and Reuse Research Center (WDRC); Water Desalination & Reuse Research Cntr
Publisher:
Society for Sedimentary Geology
Journal:
Journal of Sedimentary Research
Issue Date:
1-Mar-2011
DOI:
10.2110/jsr.2011.18
Type:
Article
ISSN:
15271404
Appears in Collections:
Articles; Water Desalination and Reuse Research Center (WDRC)

Full metadata record

DC FieldValue Language
dc.contributor.authorMaliva,, Robert G.en
dc.contributor.authorBudd, David A.en
dc.contributor.authorClayton, Edward A.en
dc.contributor.authorMissimer, Thomas M.en
dc.contributor.authorDickson, John Anthony Den
dc.date.accessioned2015-08-03T09:03:17Zen
dc.date.available2015-08-03T09:03:17Zen
dc.date.issued2011-03-01en
dc.identifier.issn15271404en
dc.identifier.doi10.2110/jsr.2011.18en
dc.identifier.urihttp://hdl.handle.net/10754/561729en
dc.description.abstractThe Avon Park Formation (middle Eocene) in central Florida, U.S.A., contains shallow-water carbonates that have been replaced by dolomite to varying degrees, ranging from partially replaced limestones, to highly porous sucrosic dolostones, to, less commonly, low-porosity dense dolostones. The relationships between dolomitization and porosity and permeability were studied focusing on three 305-m-long cores taken in the City of Daytona Beach. Stable-isotope data from pure dolostones (mean δ 18O = +3.91% V-PDB) indicate dolomite precipitation in Eocene penesaline pore waters, which would be expected to have been at or above saturation with respect to calcite. Nuclear magnetic log-derived porosity and permeability data indicate that dolomitization did not materially change total porosity values at the bed and formation scale, but did result in a general increase in pore size and an associated substantial increase in permeability compared to limestone precursors. Dolomitization differentially affects the porosity and permeability of carbonate strata on the scale of individual crystals, beds, and formations. At the crystal scale, dolomitization occurs in a volume-for-volume manner in which the space occupied by the former porous calcium carbonate is replaced by a solid dolomite crystal with an associated reduction in porosity. Dolomite crystal precipitation was principally responsible for calcite dissolution both at the actual site of dolomite crystal growth and in the adjoining rock mass. Carbonate is passively scavenged from the formation, which results in no significant porosity change at the formation scale. Moldic pores after allochems formed mainly in beds that experienced high degrees of dolomitization, which demonstrates the intimate association of the dolomitization process with carbonate dissolution. The model of force of crystallization-controlled replacement provides a plausible explanation for key observations concerning the dolomitization process in the Avon Park Formation and elsewhere: (1) volume-for-volume replacement at a crystal scale, (2) coupled growth of dolomite crystals and dissolution of host calcium carbonate matrix, and (3) automorphic replacement by euhedral dolomite crystals. The force-of-crystallization model also does not require an influx of externally derived water that is undersaturated with respect to calcite to dissolve calcite, a fact that could simplify diagenetic models of porosity generation in dolostones. The later addition of external carbonate can result in a substantial reduction in porosity by the precipitation of dolomite cement, which could convert a high porosity sucrosic dolostone into a dense "Paleozoic type" dolostone. Copyright © 2011, SEPM (Society for Sedimentary Geology).en
dc.publisherSociety for Sedimentary Geologyen
dc.titleInsights into the dolomitization process and porosity modification in sucrosic dolostones, Avon Park Formation (Middle Eocene), East-Central Florida, U.S.A.en
dc.typeArticleen
dc.contributor.departmentWater Desalination and Reuse Research Center (WDRC)en
dc.contributor.departmentWater Desalination & Reuse Research Cntren
dc.identifier.journalJournal of Sedimentary Researchen
dc.contributor.institutionSchlumberger Water Services USA, 1567 Hayley Lane, Fort Myers, FL 33907, United Statesen
dc.contributor.institutionDepartment of Geological Sciences, University of Colorado at Boulder, 399 UCB, Boulder, CO 80309, United Statesen
dc.contributor.institutionSchlumberger Water Services USA, 3845 N. Business Center Dr., Tucson, AZ 85705, United Statesen
dc.contributor.institutionDepartment of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, United Kingdomen
kaust.authorMissimer, Thomas M.en
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