Bulletin No. 64


throughout Brevard County. In general, the "B" marker separates more thinly-bedded strata of the upper Avon Park Formation from more thickly-bedded and massive units of the lower Avon Park Formation.

 Grain-supported limestones are only moderately indurated with generally high interparticle porosity and high permeability. Minimal amounts of pore-occluding cements are present and most of the porosity is primary in origin. Thin section analysis of middle Avon Park grainstones and packstones shows an isopachous fringing rim of cement surrounding individual grains, indicating possible marine phreatic cementation at the site of deposition (Harris et al., 1985). Possibly early marine cementation provided a rigid framework, thereby limiting the effects of compaction-related porosity reduction in these sediments.

 Avon Park Formation dolostones exhibit a wide range of textural diversity due to varying types and degrees of diagenesis. Dolostones have generally subhedral to euhedral crystalline texture and have equigranular to inequigranular crystal fabric (Friedman and Sanders, 1967). Crystal size ranges from microcrystalline to fine. Burrows and vugs commonly contain coarsergrained dolomite crystals than the surrounding matrix. Sucrosic texture is common in very fineto fine-grained dolostones.

 Induration is generally high in all the Avon Park dolostones. Pore type, porosity, and permeability are extremely variable throughout the formation. Porosity types include intercrystalline, moldic, intergranular, vugular, and fracture. Moldic porosity is probably the product of matrix selective dolomitization whereby unaltered calcitic allochems remain in the rock and are later dissolved, possibly during periods of subaerial exposure (Murray, 1960). Dolostones speckled with white calcitic allochems (chiefly foraminifera), alternating with moldic dolostones, throughout much of the Avon Park Formation indicate that partial- or matrix-selective dolomitization was an important diagenetic process affecting these rocks.


 The lowermost Avon Park Formation is characterized by intervals of nodular chert and cherty dolostones. Silicified burrows encased in dolostone were present in the West Melbourne core from 1,700 to 1,705 feet BLS. Also, fracture-filling chert was apparent in cores from several injection wells (Harris #2, South Beaches). The chert is typically black to gray and highly brittle.

 An apparent microfaunal marker horizon occurs within the lower Avon Park Formation in a majority of injection wells. Abundant Operculina cookei occurred at the same approximate stratigraphic level (based on correlation with geophysical log markers) in each well except for the D. B. Lee and West Melbourne sites (Plate 1). The Operculina cookei zone was encountered in the West Melbourne well approximately 80 feet below the equivalent stratigraphic position observed in other wells. The difference in stratigraphic position could be related to inadequate sampling procedures during drilling or poor preservation related to diagenesis. The presence (or absence) of this horizon in the D. B. Lee well was not determined due to limited access to samples.

 Upper Eocene Ocala Limestone

 The Ocala Limestone, as described by Applin and Applin (1944), consists of an upper member of white, poorly-indurated, porous coquina composed chiefly of foraminifera, bryzoan and echinoid fragments and a lower member of cream to white, fine-grained, poorly to moderately indurated, micritic, miliolid-rich limestone. The contacts between the underlying Avon Park Formation and the overlying Hawthorn Group are unconformable (Chen, 1965). In Brevard County, the Ocala consists of white to very light orange, medium grained, poorly to rarely moderately indurated, interbedded packstone and wackestone with occasional grainstone and mudstone. The principal allochems are foraminifera and echinoderm fragments. The Ocala Limestone micro-fauna commonly includes Lepidocyclina ocalana, Amphistegina pinarensis, and various