Abstract

The approximately 300-m (984.2 ft)-thick Oligo–Miocene carbonates of the Perla field consist of an overall deepening-upward sequence predominantly composed of larger benthic foraminifera and red algae (oligophotic production) with a minor contribution from shallow-water (euphotic) carbonate components (green algae and corals). Two types of facies successions occur. In the lower part, lithofacies persistently occur in transgressive-regressive sequences bounded by erosional surfaces (Type 1). In Type 1 successions, the interactive analysis of the skeletal components and textures, along with the order of the facies succession (Walther’s Law) permit the establishment of the depositional model, the architecture of the building blocks, and their stacking patterns. Deposited in a context of tectonic subsidence, the building blocks progressively onlapped with backstepping configuration onto a paleoisland.

In the upper part, volumetrically less important, lithofacies recurrence is sporadic, while fining-upward successions are common. They commonly have gray-black coloration (pyrite, phosphate, and glauconite) and planktonic foraminifers and nannofossils are abundant (Type 2). They are interpreted as gravity-flow deposits deposited below a chemocline. This requires a younger carbonate factory updip of the cored area, consistent with the subsidence, to supply the rhodolith-rich deposits of the upper part of the Perla limestone.

A gentle distally steepened ramp model (distal bulge) is considered. Nevertheless, waves fail to explain the facies distribution in the Perla ramp; the turbulence induced by breaking internal waves is the best candidate to explain the facies distribution in the outer ramp.