Coastal carbonate systems: evolving paleoclimatic and paleoenvironmental proxies to relative sea-level change

Ancient coastal carbonate depositional systems provide exceptional records of past changes in relative sea level– globally and locally (tectonics) – and of paleoenvironmental variations. Here we present new work on carbonate outcrops within the UNESCO Rocca di Cerere Geopark in central Sicily (Caltanissetta and Enna districts). They show superb sub-vertical cliffs made of Pleistocene packstones with clinoforms which provide a high-resolution record of relative sea-level changes that correlate with precession cycles. Regionally these successions deposited during Plio-Quaternary forced regression caused by late-orogenic uplift. However, their deposition within local thrust top basins was modulated by local uplift and tectonic tilting. Collectively these global, regional, and local processes are recorded by offlapping of successive depositional cycles. Moreover, the high-resolution photogrammetric surveys we developed, revealed that the underlying anticlines tilted the original beds of almost 20°. The packstones are derived from fauna: micro-habitat variations have been here traced by changes in sediment provenance, fossil assemblages, and preservation. The resultant stratal architectures reflect the interplay between the efficiency of this carbonate factory, the environmental conditions, the minute siliciclastic input, and the evolution of accommodation space. Bio- and magneto-stratigraphy were fundamental to date, the parasequences, while organic and inorganic chemistry, benthic foraminifera assemblages, as well as stable isotopes analyses (δ¹⁸O and δ¹³C) are used as environmental and climatic proxies (where possible) to reconstruct coastal dynamics (physical and biological), in relation to the tectonic history and sea-level change.
These outcrops provide analogues to interpret stratal patterns in subsurface examples where these types of strata form important aquifers – and shallow gas reservoirs.