Hiatal duration of correlative sequence boundaries from Oligocene–Pliocene mixed carbonate/siliciclastic sediments of the south Florida Platform

Abstract

Abstract Sequence boundaries defined by regional unconformities in mixed carbonate/siliciclastic sediments have a variable duration from the margin to the interior of the Florida Platform. Factors controlling the timing and duration of these unconformities include a combination of global (eustatic) and regional mechanisms (sediment supply, current intensification). Integrated chronostratigraphies developed from a transect of continuous cores in the south-central interior to the southern margin of the Florida Platform show an increase in duration of the hiatal gaps along correlative sequence boundaries toward the platform edge. Two sequence boundaries are correlated across the south Florida Platform and mark formation contacts. The lower sequence boundary (SB-A) marks the Suwannee Limestone/Arcadia Formation contact and is of significantly less duration in the platform interior (southwest peninsular Florida, ∼2.0 m.y.) than at the south platform margin (middle Florida Keys, ∼8.1 m.y.). The hiatal gap along the upper sequence boundary (SB-B), marking the Arcadia Formation overlain by Miocene–Pliocene sediments that vary in age and composition regionally, records the same increase from the central part of the platform (southwest Florida, Arcadia Fm/Peace River Fm, ∼1.6 m.y.) to the south platform edge (lower Florida Keys, Arcadia Fm/Stock Island Fm, ∼11.5 m.y.). Eustatic fluctuations affected the relative sedimentation rates of the mixed sediments in the platform interior and at the margin. Most notably, the large eustatic fall at the end of the Early Oligocene terminated carbonate deposition of the Suwannee Limestone (SB-A). Sediment accumulation on the platform interior was more temporally continuous than at the margin because of greater siliciclastic input from the north. The strengthening of marine currents beginning in the Middle Miocene limited sediment accumulation across the southern platform margin (SB-B) and possibly caused erosion of the margin carbonates, increasing the duration of the hiatal gap on top of the Arcadia Formation.