Water/rock interaction efficiency and seawater dolomitization in the Eocene Avon Park Formation, Floridan Aquifer

Conference · Tue May 01 04:00:00 EDT 1990 · AAPG Bulletin (American Association of Petroleum Geologists); (USA)

OSTI ID:6742233

Cander, H S ^[1]

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1. Univ. of Texas, Austin (USA)

The Floridan aquifer has often been proposed as a system of extensive meteoric carbonate diagenesis and mixing zone dolomitization. However, the dominance of marine isotope (C, O, {sup 87}Sr/{sup 86}Sr) and trace element (Sr, Fe, Mn) compositions in dolomites and limestones in the Eocene Avon Park Formation, Floridan aquifer, suggests that the very active low temperature meteoric groundwater system has, over the past 40 m.y., been an inefficient mechanism of diagenesis. {delta}{sup 18}O values of all but two replacement dolomites sampled range from +2.0 to +5.1 (PDB) with high Sr concentrations (90-325 ppm), indicating dolomitization by near-normal marine water involving no significant interaction with meteoric groundwater. The two {delta}{sup 18}O-depleted (0.0 {plus minus} 1) dolomites have low Sr concentrations ({approximately}100 ppm) suggesting limited recrystallization in meteoric water. Several dolomite samples have radiogenic {sup 87}Sr/{sup 86}Sr compositions (0.70810-0.70883 {plus minus} 2), but have heavy oxygen isotope compositions (> +2.0) and high Sr concentrations (<200 ppm) suggesting precipitation from cold Miocene age or younger seawater that circulated through the Florida platform. Most limestone stable isotope compositions cluster around marine values (({delta}{sup 18}O = {minus}1 to +1, PDB) {delta}{sup 13}C = +0.5 to +2.5) and have Eocene seawater {sup 87}Sr/{sup 86}Sr compositions (0.70775 {plus minus} 2 to 0.70779 {plus minus} 2) with 400 to 500 ppm Sr. Isotopic compositions of limestones from the east coast of Florida are all within these ranges. Only some limestones from central Florida and the west coast contain depleted stable isotopic compositions and low Sr concentrations. The sample with the most depleted stable isotope values has a radiogenic {sup 87}Sr/{sup 86}Sr composition (0.70870 {plus minus} 2), suggesting that diagenetic meteoric water migrated through post-Miocene strata.

• OSTI ID: 6742233
• Report Number(s): CONF-900605--
• Conference Information: Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (USA) Journal Volume: 74:5
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METAL COMPOUNDS
ALKALINE EARTH METALS
AQUIFERS
BETA DECAY RADIOISOTOPES
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBONATE MINERALS
CARBONATE ROCKS
CARBONATES
CENOZOIC ERA
DIAGENESIS
DOLOMITE
ELECTRON CAPTURE RADIOISOTOPES
ELEMENTS
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
FEDERAL REGION IV
FLORIDA
GEOLOGIC AGES
GEOLOGIC FORMATIONS
HOURS LIVING RADIOISOTOPES
INTERMEDIATE MASS NUCLEI
IRON
ISOMERIC TRANSITION ISOTOPES
ISOTOPE RATIO
ISOTOPES
LIGHT NUCLEI
LIMESTONE
MAGNESIUM CARBONATES
MAGNESIUM COMPOUNDS
MANGANESE
METALS
MINERALS
NORTH AMERICA
NUCLEI
OXYGEN 18
OXYGEN COMPOUNDS
OXYGEN ISOTOPES
RADIOISOTOPES
ROCKS
SEDIMENTARY ROCKS
STABLE ISOTOPES
STRONTIUM
STRONTIUM 86
STRONTIUM 87
STRONTIUM ISOTOPES
TERTIARY PERIOD
TRANSITION ELEMENTS
USA