Conodont biostratigraphy around the Carnian/Norian boundary is rather problematic because of the apparent provincialism of most of the conodont species. New biostratigraphic data from Pizzo Mondello, Western Sicily, Italy (a 400 m thick succession of hemipelagic limestones, belonging to the Cherty Limestone), point out clear relationships among the three most widespread conodont genera Carnepigondolella, Metapolygnathus, Epigondolella and allow to identify particular trends in the genera turnovers which affected the real conodonts stratigraphic distribution. The first 48 meters of the section are largely dominated by the genus Carnepigondollella, with some Paragondolellae, only sporadic Metapolygnathids (M. mersinensis along with transitional forms P. noah - M. communisti) and few representatives of Epigondolella orchardi. In the overlaying 17 meters, the genus Carnepigondolella and transitional forms P. noah - M. communisti disappear, replaced by the genus Epigondolella (several E. quadrata). The genus Metapolygnathus is still rare. In the following 10 meters, a mass occurrence of the M. communisti group along with M. primitius is present, while the genus Epigondolella disappears. Another genera overturning takes place in the last 30 meters of the section, where advanced Epigondolellae (triangularis group) almost replace Metapolygnathids (only few M. parvus still occur). After comparisons with sedimentological data (Nicora et al., 2007) and geochemical variations (d13C or d18O; Muttoni et al., 2004), at Pizzo Mondello section, the turnovers of conodont genera around the Carnian/Norian boundary might be likely explained by competition of Carnepigondolella versus Metapolygnathus and, subsequently, of Epigondolella versus Metapolygnathus, or by invasions of conodont species from other domains (North America; see Noyan and Kozur, 2007 and references herein).
|Titolo:||Why generic turnovers in Carnian/Norian conodonts?|
MAZZA, MICHELE (Primo)
|Data di pubblicazione:||giu-2008|
|Settore Scientifico Disciplinare:||Settore GEO/01 - Paleontologia e Paleoecologia|
|Enti collegati al convegno:||Museo di Scienze Naturali Alto Adige|
|Citazione:||Why generic turnovers in Carnian/Norian conodonts? / M. Mazza, M. Rigo. ((Intervento presentato al convegno The Triassic climate: Workshop on Triassic paleoclimatology tenutosi a Bolzano nel 2008.|
|Appare nelle tipologie:||14 - Intervento a convegno non pubblicato|