Depositional model and paleodepth reconstruction of a coral-rich, mixed siliciclastic-carbonate system: the Burdigalian of Capo Testa (northern Sardinia, Italy)

Abstract

This study presents a detailed facies analysis and paleodepth reconstruction of a coral-rich mixed siliciclastic-carbonate system Burdigalian in age, outcropping in the northern sector of Sardinia (Capo Testa). Excellent exposures of continuous sea-cliff outcrops around the southwestern and northeastern area of Capo Testa promontory allowed us to: (1) trace stratigraphic surfaces; (2) document stratal geometries; (3) discern details of the lithofacies and, (4) reconstruct the paleodepths of the different depositional environments. A total of seven sedimentary facies has been recognized and interpreted: siliciclastic conglomerate and coarse bioclastic sandstone (F1), fine- to medium-grained hybrid sandstone (F2, scleractinian coral domestone (F3), bioclastic packstone to floatstone with platy Porites (F4), red algae floatstone to rudstone (F5), larger benthic foraminifers (LBF) bioclastic rudstone floatstone in a packstone matrix (F6), molluscan floatstone in a bioclastic packstone matrix (F7). The investigated system is characterized by nearshore to shoreface deposits with a conspicuous terrigenous content that grades seaward into deeper zones where coral patch-reefs developed in association with adjacent areas colonized by seagrass meadows. The more distal facies are constituted by scattered encrusting tabular colonies of Porites in growth position occurring in a deeper and lower-energy environment. The paleodepth interval that is observed in the Capo Testa outcrop ranges from 0 to 50 m.