C Ferrara

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

Abstract The Palaeocene of southern Sardinia includes a continental ferruginous sedimentation, with a high content of Al and Fe, indicative of a subhumid tropical climate. The subsequent microcodium carbonated detrital microcodium levels, containing an abundant quartzose fraction, rather suggest semiarid conditions. In SW Sardinia, the marine deposits, referred to Late Thanetian–Lower Ypresian (=Ilerdian) times, are limestones including larger foraminifers and contain significant amounts of quartz. A lower content of detrital kaolinite points a sediment source from the surrounding areas with a semiarid climate. The occurrence, at the top of this unit, of small trochospiral rotaliids and larger amount of detrital kaolinite suggests a transition to a rainy tropical climate in the adjacent areas. These limestones pass gradually to carbonate sediments characterized by large amounts of detrital kaolinite and intercalated coal layers, with pollen of tropical palms, attributed to the Late Ypresian (=Cuisian)–Early Lutetian and referred to a humid-subhumid tropical climate.

Coastal dunes vulnerability. GAVAM checklist method used at three mediterranean microtidal wave dominated beaches (Gulf of Cagliari)

The study shows the results achieved by using Geomorphology, Aeolian, Vegetation, Anthropogenic, Marine influences, (GAVAM) checklist, in three coastal dune zones of beaches located in southern Sardinia. The aim is the experimentation of reproducibility of GAVAM checklist in three Mediterranean microtidal wave dominated beaches.The studied dune zones are located at three Site of Community Importance (SCI) sites: ITB 042230 Porto Campana, ITB 042218 Stagno di Piscinni e ITB 040020 Isola dei Cavoli, Serpentara, Punta Molentis (southern Sardinia).By the application of GAVAM checklist the Partial Index Vulnerability (IVp) and the Dune Vulnerability Index (DVI) or total (IV) values are sequentially derived. IV index either partial or total ranges between 0 and 1, and as the index increases, the ability of the dune system to withstand further interventions decreases.The methodology has allowed an objective deduction to both potential vulnerability and the main source of imposed changes, as well major threats/stress factors have been assessed. DVI values range between 0.47 e 0.59 and indicate medium to high vulnerability.Moreover, the use of aerial photographs also highlighted the need for the implementation of the checklist using additional parameters related to fluvial-lacustrine processes and of particular anthropogenic activities.

Paleocene palustrine and ephemeral alluvial facies in southern Sardinia (Italy)

Paleocene ephemeral alluvial and palustrine deposits have been recognized in several small outcrops in southern Sardinia. Three sedimentary units have been distinguished: the basal one, mainly terrigenous, made up of alluvial pedogenized deposits, the intermediate one, entirely carbonate, made up of pedogenized fresh water deposits, and the third one, terrigenous-carbonate, recording the beginning of the Thanetian marine ingression in Sardinia. The carbonate deposits are the most developed and are mainly characterized by the presence of Microcodium, both with corn-cob aggregates, in some cases forming palisades or reef-like buildups, and with disarticulated grains forming resedimented deposits; charophyte stems and gyrogonites and stromatolites are also present, in some cases frequent. Deposits rich in charophyte stems indicate the presence of perennial water ponds. Alternances of humid and dry periods favoured erosive fluctuations, as indicated by the frequence of resedimented intraclasts of fresh water sediments, biotic remains as charophytes and stromatolites and, over all, detrital disaggregated Microcodium grains. The studied small outcrops are the only remnants of a probably wide Paleocene continental sedimentary cover, and provide informations on a variety of depositional facies, which are useful proxies for depicting a landscape with wetlands and detrital Microcodium deposits, similar to the coheval continental landscape widespread in southern France and in northeastern Spain.