The Rotzo Formation (Lower Jurassic) is characterized by a rich paleontological content. It is famous all around the world mostly thanks to its great amount of big aberrant bivalves, among which the genus Lithiotis, described in the second half of the nineteenth century. The unusual shape of Lithiotis and Cochlearites shells, extremely elongated and narrow, characterized by a spoon-like body space placed in a high position, rarely preserved, seems suggest their adaptation to soft and muddy bottoms with an high sedimentation rate. Microfossils of the Rotzo Formation consist of benthic foraminifera, calcareous algae, ostracods and coprolites. Foraminifera are mainly benthic agglutinated species belonging to the superfamily Lituolacea (suborder Textulariina), while lamellar and porcellaneous-walled species are very rare. The Rotzo Formation extensively outcrops in the Valbona Pass area, where the following aspects are here illustrated and discussed. 1) Palaeobiology of the marly units: Pholadomya athesiana assemblage; Gresslya elongata and Lychnothyris rotzoana assemblage. 2) Sedimentary and biotic evolution of the ?Cochlearites micromound of Monte Toraro; the “Lithiotis” mound of Cima di Valbona 3) Palaeobiology and palaeoenvironment of black shales: The Eomiodon assemblage.
The Rotzo Formation (Lower Jurassic) at the Valbona Pass (Vicenza Province)
POSENATO, Renato;BASSI, Davide;FUGAGNOLI, Anna
2005
Abstract
The Rotzo Formation (Lower Jurassic) is characterized by a rich paleontological content. It is famous all around the world mostly thanks to its great amount of big aberrant bivalves, among which the genus Lithiotis, described in the second half of the nineteenth century. The unusual shape of Lithiotis and Cochlearites shells, extremely elongated and narrow, characterized by a spoon-like body space placed in a high position, rarely preserved, seems suggest their adaptation to soft and muddy bottoms with an high sedimentation rate. Microfossils of the Rotzo Formation consist of benthic foraminifera, calcareous algae, ostracods and coprolites. Foraminifera are mainly benthic agglutinated species belonging to the superfamily Lituolacea (suborder Textulariina), while lamellar and porcellaneous-walled species are very rare. The Rotzo Formation extensively outcrops in the Valbona Pass area, where the following aspects are here illustrated and discussed. 1) Palaeobiology of the marly units: Pholadomya athesiana assemblage; Gresslya elongata and Lychnothyris rotzoana assemblage. 2) Sedimentary and biotic evolution of the ?Cochlearites micromound of Monte Toraro; the “Lithiotis” mound of Cima di Valbona 3) Palaeobiology and palaeoenvironment of black shales: The Eomiodon assemblage.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
