A refined ammonoid biostratigraphy is reported for a critical interval of the Bagolino section (Giudicarie Area, Northern Italy), a candidate for the Anisian/Ladinian stage boundary. The Avisianum Subzone has been documented, and its boundary with the Crassus Subzone has been redefined, on the basis of new findings of Reitziites reitzi, Aplococeras aff. smitbi, Aplococeras avisianum, Halilu-cites riisticus, Parasturia sp. and other significant ammonoids. Six potential criteria for the definition of the Anisian/Ladinian boundary can now be considered in this single stratigraphic section, so that the FO of Eoprotracbyceras atrionii is no longer the unescapable choice at Bagolino. Despite several drawbacks, including the absence of paly-nomorphs and daonellid bivalves, the thermal history preventing the recover)- of magnetic and isotopic signals, and a lower sedimentation rate with respect to many other sections of the Southern Alps, the Bagolino section is here accepted as stratotype for the Anisian/Ladinian boundary, but further paleontological and sedimentological studies should be considered.
Refined ammonoid biochronostratigraphy of the Bagolino section (Lombardian Alps, Italy), GSSP candidate for the base of the Ladinian stage
GIANOLLA, Piero;
2003
Abstract
A refined ammonoid biostratigraphy is reported for a critical interval of the Bagolino section (Giudicarie Area, Northern Italy), a candidate for the Anisian/Ladinian stage boundary. The Avisianum Subzone has been documented, and its boundary with the Crassus Subzone has been redefined, on the basis of new findings of Reitziites reitzi, Aplococeras aff. smitbi, Aplococeras avisianum, Halilu-cites riisticus, Parasturia sp. and other significant ammonoids. Six potential criteria for the definition of the Anisian/Ladinian boundary can now be considered in this single stratigraphic section, so that the FO of Eoprotracbyceras atrionii is no longer the unescapable choice at Bagolino. Despite several drawbacks, including the absence of paly-nomorphs and daonellid bivalves, the thermal history preventing the recover)- of magnetic and isotopic signals, and a lower sedimentation rate with respect to many other sections of the Southern Alps, the Bagolino section is here accepted as stratotype for the Anisian/Ladinian boundary, but further paleontological and sedimentological studies should be considered.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
