--> ABSTRACT: A Foramol Type Carbonate Ramp in Tropical-Subtropical Setting: The Link Between Tectonics and Nutrients, by M. Brandano, G. Civitelli, and L. Corda; #90906(2001)

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M. Brandano, G. Civitelli, and L. Corda

Dipartimento Scienze della Terra Università "La Sapienza" Roma (Italy)

ABSTRACT: A Foramol Type Carbonate Ramp in Tropical-Subtropical Setting: The Link Between Tectonics and Nutrients

Carbonate platforms are built and modified by depositional and erosional processes, ruled over by the interaction of eustasy, subsidence, sediment production and climate. Relative sea-level changes depend on eustasy and subsidence whereas climate and nutrients control the sediment-producing biota and thus the type and amount of sediment being produced (Pomar & Ward, 1999).

This study investigates a Late Aquitanian-Serravallian isolated carbonate ramp characterized by the lack of inner ramp facies. This ramp, developed in the Central Mediterranean area (Central Appennines), exhibits Miocene carbonates unconformably overlying the Upper Cretaceous limestones.

The ramp depositional profile in the Early Burdigalian was reconstructed using the relative position of facies belts, and the dependence of some biota components upon light penetration. The ramp was divided into two environmental subdivisions: middle ramp and outer ramp (inner ramp is missing). In the middle ramp the most abundant lithofacies are medium-to-coarse-grained red algae-mollusklarger foraminifera packstones, rhodolith rudstones, and, in the inner sector, scattered coralboundstones. The presence of red algae and larger foraminifera such as Heterostegina, Operculina, Elphidium and Amphistegina place this depositional environment in the mesophotic zone.

The outer ramp can be divided into three parts: a proximal outer ramp characterized by coarsegrained echinoid-foraminiferal packstones and pectinid-bryozoan floatstones; an intermediate outer ramp with fine to medium-grained echinoid-planktonic foraminiferal packstones; a distal outer ramp with sponge-echinoid-planktonic foraminiferal wackestones-packstones, often bioturbated. The faunal association suggests that this depositional environment was situated in the aphotic zone.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado