Calcite cementation in the modern Floridan aquifer: A modern example for confined-aquifer cementation models

Conference · Wed Jan 01 04:00:00 EST 1992 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5935669

Budd, D A; Hammes, U ^[1]

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1. Univ. of Colorado, Boulder, CO (United States). Dept. of Geological Sciences

Over 300 thin sections collected from 13 cores of the Suwannee Fm. in west-central Florida were examined to determine if any calcite cements had formed in these rocks while they have resided in the Floridan aquifer system. Petrographic data indicate that most cements are associated with vadose-zone features and/or mineralogical stabilization, and what all cements are pre-compaction in origin. Cements adjacent to open pores (and thus the most recent) tend to exhibit the low trace-element contents; Mg, Sr, Mn, and Fe contents are typically <1.5 mole %, <150 ppm, <20 ppm, and <25 ppm, respectively. Isotopic compositions of the cements show a wide range in carbon values (+1 to [minus]8 [per thousand], PDB) and a relatively narrow range in oxygen values ([minus]2 to [minus]4 [per thousand], PDB). The petrographic observations suggest that all cements are early diagenetic phases that formed during and immediately after Suwannee deposition. The trace-element and isotopic data support this conclusion. Cements in equilibrium with the confined aquifer would have much higher Fe, Sr, and Mg contents, and would have more negative oxygen isotopic values. It is thus concluded all the cements formed prior to the onset of regionally confined freshwater aquifer conditions. This means a basically inert system with respect to calcite cementation for the last 5 to 10 Ma while these rocks have been part of the confined aquifer. The lack of calcite cementation in the upper Floridan aquifer has significant implications to models of paleo-aquifer cementation inferred from the study of ancient systems. In particular, the capacity of regional confined freshwater aquifers to produce large amounts of cement over geographically widespread areas is probably overestimated. This includes the formation of luminescently zoned cements.

• OSTI ID: 5935669
• Report Number(s): CONF-921058--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 24:7
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
AQUIFERS
CALCITE
CARBONATE MINERALS
CEMENTING
CHEMISTRY
DEVELOPED COUNTRIES
DIAGENESIS
FLORIDA
GEOCHEMISTRY
GEOLOGIC FORMATIONS
GEOLOGIC MODELS
GEOLOGY
ISOTOPE RATIO
MINERALS
NORTH AMERICA
PETROGRAPHY
USA