Pliocene-Pleistocene stratigraphic paleobiology at Altavilla Milicia (Palermo, Sicily): tectonic, climatic and eustatic forcing

Abstract

<p>The integration of sedimentary facies analysis, ichnology and benthic mollusc quantitative paleoecology allowed to interpret factors controlling deposition of the Altavilla Milicia alluvial to marine succession, near Palermo, Sicily. Two major composite units are recognised, separated by an angular unconformity and internally subdivided into elementary depositional sequences. Calcareous nannoplankton biostratigraphy allowed to recognize the upper Pliocene and lower Pleistocene, a time interval that covers the onset of the Quaternary glaciation. The main asset of the succession is driven by tectonic compression and accommodation by transpressional faults, a regime that led to a change in the direction of fluvial sediment delivery, from axial to transverse with respect to the basin elongation. High-frequency eustatic changes have driven the formation of elementary depositional sequences. The upper Piacenzian is characterised by marine bioclastic strata, deposited during maximum flooding intervals of the two large composite units. Mixed carbonate-siliciclastic lithosomes show a good correlation with shallow marine shell-rich detrital carbonates of Northern and Southern Italy and with Mediterranean deep-water sapropel clusters, suggesting common climatic forcing. Some tropical species previously thought to disappear from the Mediterranean at around 3.0 Ma, are instead present in the upper Piacenzian of Sicily. The study suggests that the Pliocene macrobenthos with tropical affinities disappeared from different sectors of the Mediterranean at different times.</p>

NATURAL CASTS OF <em>ENTOBIA</em> FROM THE LATE CAENOZOIC OF SICILY

“…This is well-known for its richly-fossiliferous deposits and high-diversity shelly assemblages occurring along the right flank of the Milicia creek (Altavilla s.s. succession in Moroni & Paonita 1964;unit ALT in Dominici et al 2020) [included in the "Marly-Arenaceous Formation of Belice", BLC of Catalano et al 2013]. High-frequency eustatic variations drove the formation of the Altavilla succession in shoreface-to-offshore transition and delta-front environments (Dell'Angelo et al 2012;Dominici et al 2020). Within the Altavilla sandstones, cyclicity is highlighted by the alternation of shelly or cemented strata with thicker, uncemented ones, possibly produced by the alternation of dry and wet conditions under climatic forcing (Dominici et al 2020).…”

“…High-frequency eustatic variations drove the formation of the Altavilla succession in shoreface-to-offshore transition and delta-front environments (Dell'Angelo et al 2012;Dominici et al 2020). Within the Altavilla sandstones, cyclicity is highlighted by the alternation of shelly or cemented strata with thicker, uncemented ones, possibly produced by the alternation of dry and wet conditions under climatic forcing (Dominici et al 2020). Though trace fossils are very abundant, particularly on mollusc shells, where bioerosion structures produced by polychaetes and entobians are locally very common, ichnological studies have only recently been undertaken (Dávid et al 2017;Dominici et al 2017Dominici et al , 2020.…”

“…The sample from site S1 was collected from the lower bed of a triplet of yellowish, cemented sandstone beds attributable to the Gelasian (Dominici et al 2020). These cemented beds alternate with uncemented sandy beds with scattered small pebbles (Fig.…”

“…2C, D). The bed containing the studied sample formed in a shoreface delta-front environment under conditions of sediment starvation and winnowing (Dominici et al 2020). This bed overlies an uncemented yellowish bed with a Corbula-Pelecyora bivalve association, about 2 m-thick.…”

“…The knowledge of the Entobia association for Italian sites is rather scarce and almost limited to the study of late Caenozoic calcarenites from Puglia, in South Italy (Bromley & D'Alessandro 1984). To our knowledge, nothing is known on fossil sponge traces from Sicily, except for a doubtful Mesozoic case (Cherchi & Schroeder 2012) and Plio-Pleistocene borings found on Mesozoic limestone blocks and in an oyster shell bed (Dávid et al 2017;Dominici et al 2020).…”