Diversità, morfologie di crescita e tafonomia: fattori di controllo del fabric nelle successioni carbonatiche a alghe corallinacee

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Benthic assemblages, diversity controls and environmental parameters: assessing different scales of complexity in coralline algal and large foraminiferal carbonates in the Paleogene

Benthic assemblages, diversity controls and environmental parameters are analysed at different scales of complexity in coralline algal and larger foraminiferal carbonates in the Paleogene successions of NE Italy

Coralline red algae in the Middle-Upper Eocene shallow water carbonates of the Colli Berici (north-eastern Italy).

The paper illustrates the coralline red algal (Corallinales, Rhodophyta) facies occurring in the middle-upper Eocene shallow water carbonate successions of the Colli Berici (Vicenza, northeastern Italy). Coralline assemblages are described in terms of growth-forms, taxonomy, taphonomic signatures. Larger benthic foraminifera are also described and illustrated. Palaeoecological and palaeoenvironmental settings are described and illustrated by the modelization of the shallow water carbonate platform which developed in the Colli Berici during the middle-late Eocene

Larger foraminiferal and coralline algal benthic communities of Upper Eocene and Upper Oligocene carbonates: responses to different trophic resources.

Trophic gradients in shallow water carbonate settings from Late Eocene to Late Oligocene are detected by using larger foraminiferal and coralline algal assemblages. The studied successions are from the Veentian area, north-east Italy

Temperature and nutrient controls of coralline algal and larger foraminiferal dominated Paleogene Tethyan carbonates

This study is based on facies and diversity patterns of late Eocene (Priabonian), early Oligocene (Rupelian) and late Oligocene (Chattian) LF and CCA communities occurring in neritic carbonate settings from the northern margins of the Western Tethys in northeastern Italy. Recent taxonomic re-assessments of coralline algae have shown important differences in species diversity from the Priabonian to the Chattian. During the Priabonian and the Chattian, melobesioids and mastophoroids are diverse and abundant, sporolithaceans are present with a moderately richness, Lithophylloideae are absent. During the Rupelian, although the corallines as a carbonate producer are very prominant, the diversity as such is markedly lower and is restricted to few melobesioid species. We discuss possible causes for these mid-latitude shallow-water carbonate benthic communities. We suggest that evolutionary and extinction events together with global and regional changes in temperature and trophic resources provide the key for understanding these dramatic changes in floral and faunal diversities

Facies successions and depositional interpretation of Upper Oligocene carbonates from north-eastern Italy.

Facis analysis of shallow water carbonates outcropping in the Venetian area is presented

Components, facies and ramps: Redefining Upper Oligocene shallow water carbonates using coralline red algae and larger foraminifera (Venetian area, northeast Italy)

Chattian mixed carbonate-siliciclastic deposits from two palaeogeographic units of Southern Alps, the Lessini Shelf and Venetian foreland basin of northeast Italy, are studied with respect to facies distributions and controlling ecological factors on dominant biogenic components. These ramp depositional systems are located in the western Southern Alps on the Lessini Shelf, and in the eastern Southern Alps in the Venetian foreland basin. The successions show an extensive geographic distribution of at least 150 km×40 km at the southern margin of the Southern Alps. Palaeoenvironments are inferred following microfacies characteristics and floral and faunal indicators, especially those of coralline red algae and larger foraminifera. An inner- to middle homoclinal ramp morphology is reconstructed based on facies distributions and taxonomic and coralline algal growth-form proxy data. The distribution along depositional strike shows variation from thinner, carbonate dominated sequence in the west (Monti Berici and Monti Lessini) to a more variable, mixed carbonate-siliciclastic dominated environment to the east (Vittorio Veneto, Alpago). Facies character and occurrence are controlled by local hydrodynamic conditions and varying water turbidity of the studied ramp depositional system. The general facies succession shows a transgressive sequence from the proximal inner- to proximal middle ramp. A shoal belt of trough cross-bedded sandstones occurs in a proximal inner ramp position in all of the studied areas. In a gentle-dipping homoclinal ramp, most benthic organisms inhabited the relatively quite environments off these shoals in a distal inner ramp setting. Basinward environments (proximal middle ramp) constitute areas of maximal carbonate production and consist primarily of larger foraminiferal facies and rhodolith pavements. Larger foraminifera, represented by two larger foraminiferal assemblages, are most diversified in the shallower settings (near the fair-weather wave base, distal inner/proximal middle ramp), whereas coralline algae predominate in deeper areas (proximal middle ramp) constructing extensive rhodolith pavements. Rhodolith pavements are distinguished with respect to rhodolith shape, size, growth-forms and coralline algal taxonomic composition. Larger foraminifera are interpreted with respect to shell structures, shell architectures and comparable Recent counterparts. The analysed benthic communities thrived in a mesotrophic regime within trophic gradients constrained by fluvial influence. Coralline algal dominance and a moderately diverse larger foraminiferal assemblage suggest a tropical/warm temperate transition. The considerable stability imposed on sediments by the rhodolith pavement must also have significantly contributed to the maintenance of a middle ramp profile bulge. This study will contribute to a better understanding of Oligocene carbonates which have received less attention than their Eocene or Miocene counterparts