A depositional and diagenetic model for the Eocene Sulcis coal basin of SW Sardinia

Abstract

Detailed sedimentological, mineralogical and petrographical analysis of closely spaced cored boreholes has enabled the development of a revised depositional model for the early Eocene coal-bearing Produttivo Formation of the Sulcis Basin. The deposition of autochthonous-hypautochthonous palustrine-lacustrine coals and associated carbonates was interrupted episodically by sedimentation of allochthonous lithocalcirudites and lithocalcarenites. The latter clastics display characteristic upward shoaling tidal flat sequences related to marine incursions. This interpretation is in contrast to the previously accepted fluvial origin of the detrital episodes. The coarse basal transgressive lag deposits consist of various carbonate intraclasts, dolosparite, grains consisting of calcite cement and euhedral-subhedral evaporite-bearing quartz grains. Combined stable isotope and cathodoluminiscence analysis has revealed a complex diagenetic history for the clastic deposits. The potential extrabasinal or intrabasinal provenance of the clasts, in particular the origin of the evaporite relicts, is discussed. The subtropical-tropical coastal marshes of the Florida Everglades (USA) are proposed as a possible modern analogue for the subbituminous Sulcis coals.

New stratigraphic and sedimentological investigations on the Middle Eocene–Early Miocene continental successions in southwestern Sardinia (Italy): Paleogeographic and geodynamic implications

“…(Fig. 1, top left) posed above the ''Lignitifero'' succession, having an age of Latest Paleocene to Middle Eocene (Barca and Costamagna, 2000;Cherchi, 1979;Cocozza et al, 1989;Cocozza et al, 1974;Dreesen et al, 1997;Fanni et al, 1982;Murru and Salvadori, 1987;Pittau, 1974). The boundary between these two units is different depending to the locality: it varies from paraconformable to angular unconformable.…”

The Importance of Baseline Surveys of Near-Surface Gas Geochemistry for CCS Monitoring, as Shown from Onshore Case Studies in Northern and Southern Europe

“…The Produttivo Formation has been affected by E-W and NNW-SSE oriented block faults related to rotation of the Corsica-Sardinian microplate (Poli and Rosi, 2005). Post-eruptive deformation of the volcanic succession is moderate, with vertical faulting causing offsets of up to 40 m (Dreesen et al, 1997). Although the major regional structures occur outside the study area, a number of local fault systems have been recognised based on field observations, airphoto lineaments, and borehole results.…”

“…The Sulcis Basin is filled by Palaeogene marine and continental deposits, Oligocene-Miocene calc-alkaline volcanics, and Neogene to Quaternary fluvial and lacustrine deposits. A regressive sequence within the Palaeogene deposits hosts the coal-bearing Produttivo Formation (Dreesen et al, 1997), which outcrops to the east of the investigated area, ranges in thickness from 40 to 70 m, and dips at 8-10°to the SSW. The OligoceneMiocene volcanics consist of calc-alkaline, basaltic to intermediate lava flows, and calc-alkaline, dacitic to rhyolitic ignimbrites (Beccaluva and Civetta, 1985;Poli and Rosi, 2005).…”

The Palaeocene–Middle Eocene deposits of Sardinia (Italy) and their palaeoclimatic significance

“…Concerning isotopes, δ 13 C values range from −1.87 to −3.30 and δ 18 O from −5.10 to −7.01; these depleted values with respect to standard values of Lower Eocene marine limestones [38] may be interpreted as a diagenetic modifications [12] and therefore will not be used for a palaeoclimatic reconstruction.…”