LARGER BENTHIC FORAMINIFERAL BIOFACIES OF THE OCALA LIMESTONE

Larger foraminifera are used to examine three questions regarding the Late Eocene Ocala Limestone of the Florida Platform: paleoenvironments (restricted or open shelf?), morphology of the northern margin of the platform adjacent to the current-swept Gulf Trough (rimmed shelf or ramp profile?); and carbonate platform response to the terminal Eocene highstand (keep-up, catch-up, or drowned?).

Broadly, three biofacies are recognized upsection:

(1) Fallotella-Discorinopsis-Fabularia Assemblage (FDFA) in chloralgal/miliolid grainstones, representing shallow subtidal facies on a restricted platform (lower Ocala).

(2) Nummulites-Lepidocycina Assemblage (NLA) in packstones and some grainstones, with several subfacies:

(2a) Nummulites (heilprini, willcoxi) with miliolids, Amphistegina, but rare Lepidocyclina, in packstones and grainstones (nummulitic shoals), representing inner- to mid-shelf facies;

(2b) Nummulites spp. and Lepidocyclina ocalana packstones, representing mid-shelf accumulation;

(2c) Nummulites floridanus and Lepidocyclina ocalana with Pseudophragmina and Asterocyclina in packstones or grainstones, representing mid-outer shelf deposits.

(2d) Nummulites floridanus-Lepidocyclina chaperi in bryozoan packstones, also representing mid-outer shelf sedimentation (Rotularia vernoni Zone).

(3) Lepidocyclina-Asterocyclina Assemblage (LAA) in Lepidocyclina coquinas or bryozoan grainstones, with large Lepidocyclina tests encrusted with coralline algae and bryozoa, well-rounded lithoclasts, and intergranular and nodular gypsum; found along the southern flank of the Gulf Trough where the Ocala attains its greatest thickness (> 700 feet).

The change upsection from the FDFA to the NLA clearly represents deepening over most of the platform, from restricted shallow subtidal to open shelf conditions. NLA subfacies indicate further transgression upsection to mid-outer shelf environments within the photic zone. The LAA supports a rimmed shelf /skeletal bank reconstruction for the northern platform margin. Large foram shoals developed both within and along the northern margin of the platform, essentially keeping pace with sea level rise as a non-reefal carbonate ramp.