Wide coastal sectors of north-eastern Sicily are shaped by high rates of tectonic Pleistocene uplift of the area and concurrent glacio-eustatic sea level changes leading to the formation of terraces, characterised by basal marine sediments topped by continental vertebrate-bearing sediments, and caves with evidence of marine submersion. A tidal notch and associated organogenic crusts, formed by the vermetid gastropod Dendropoma cristatum found in a cave near Taormina located at an elevation of 130 m a.s.l. just above the terrace produced during the Tyrrhenian (MIS 5.5), were examined. This represents the first record of extensive vermetid bioconstructions inside a cave and a particular morphology of D. cristatum shells, which include coiled initial parts and straight distal elongated parts, with numerous internal septa. These specimens were preserved in a restricted area, with extended portions aligned parallel to each other and facing downward from a sub-horizontal step along a wall. The location of the vermetid crusts and the particular ecological requirements of this species (presently forming bioconstructions in exposed rocky shores characterised by high light intensity and water energy) points to a cave which was semi-submerged and widely open to the water energy at the time of its colonisation. The particular Dendropoma shell morphology has been interpreted as an adaptation to reach penetrating water flow rich in food and oxygen, also seen in other organisms from cave habitats. Apparent ages of the Dendropoma shells and the continental calcite crust obtained with the U-Th dating method are not consistent with the stratigraphic position of the cave and are significantly younger than expected. As observed for other dating results on the same species (and other molluscs), this indicates an alteration of the system during diagenesis and suggests caution in the use of certain species as stratigraphic constraints.
|Titolo:||Exceptional Pleistocene vermetid crusts preserved in a cave located 130 m above sea level near Taormina (NE Sicily)|
|Data di pubblicazione:||2018|
|Appare nelle tipologie:||1.1 Articolo in rivista|