New magnetostratigraphic data have been obtained from the Norian/Rhaetian boundary section of Pignola-Abriola (Southern Apennines, Italy), which consists in 60 m of basinal cherty limestones. A total of 10 magnetozones have been identified and calibrated with conodont and radiolarian biostratigraphy. The Pignola-Abriola section was cor- related to the Newark APTS with a statistical method under the assumption that stratigraphic depth is a linear proxy of time. The section was slid aside the Newark APTS producing a total of 19 possible correlation options that were evaluated by linear regression of the age-depth tie points. Then, a student t-test was applied to the linear regression coefficients to isolate the most reliable correlation options. According to our best correlation option, the Pignola-Abriola section covers the interval from E13r (∼217 Ma) to E20r (∼205 Ma) in the Newark APTS. The Norian/Rhaetian boundary based on the FAD of conodont Misikella posthernsteini and the base of the Propar- vicingula moniliformis radiolarian Zone 1 at Pignola-Abriola (Giordano et al., 2010: Lethaia 43, 573–586) falls on the Newark APTS at ∼205.4 Ma within magnetozone E20r. The magnetostratigraphy of the Pignola-Abriola section has been successfully correlated to other Late Triassic magnetostratigraphic sections from the literature spanning the Norian/Rhaetian boundary (Steinbergkogel, Oyuklu, Brumano and Pizzo Mondello) . Our magne- tostratigraphic correlation reveals an apparent discrepancy in the first appearance of conodont M. posthernsteini between Pignola-Abriola and Steinbergkogel/Oyuklu. However, we infer that the forms attributed to M. posth- ernsteini at Steinbergkogel/Oyuklu are more similar to what we refer to as M. hernsteini/posthernsteini transition at Pignola-Abriola, a solution that virtually eliminates the discrepancy. Considering the taxonomic complexity of the M. hernsteini/posthernsteini lineage, we propose to place the Norian/Rhaetian boundary in correspondence of a marked negative shift of d13Corgobserved at Pignola-Abriola at ∼41.5 m (close to the FAD of M. posthern- steini),which, according to the correlation with the Newark APTS, would have an age of ∼205.6 Ma. According to this new definition of the Norian/Rhaetian boundary, the Rhaetian is ∼4.5 Myr-long.

Magnetostratigraphic data from the Pignola-Abriola section (Southern Apennines, Italy): new constraints for the Norian/Rhaetian boundary

ZAFFANI, MARIACHIARA;RIGO, MANUEL
2014

Abstract

New magnetostratigraphic data have been obtained from the Norian/Rhaetian boundary section of Pignola-Abriola (Southern Apennines, Italy), which consists in 60 m of basinal cherty limestones. A total of 10 magnetozones have been identified and calibrated with conodont and radiolarian biostratigraphy. The Pignola-Abriola section was cor- related to the Newark APTS with a statistical method under the assumption that stratigraphic depth is a linear proxy of time. The section was slid aside the Newark APTS producing a total of 19 possible correlation options that were evaluated by linear regression of the age-depth tie points. Then, a student t-test was applied to the linear regression coefficients to isolate the most reliable correlation options. According to our best correlation option, the Pignola-Abriola section covers the interval from E13r (∼217 Ma) to E20r (∼205 Ma) in the Newark APTS. The Norian/Rhaetian boundary based on the FAD of conodont Misikella posthernsteini and the base of the Propar- vicingula moniliformis radiolarian Zone 1 at Pignola-Abriola (Giordano et al., 2010: Lethaia 43, 573–586) falls on the Newark APTS at ∼205.4 Ma within magnetozone E20r. The magnetostratigraphy of the Pignola-Abriola section has been successfully correlated to other Late Triassic magnetostratigraphic sections from the literature spanning the Norian/Rhaetian boundary (Steinbergkogel, Oyuklu, Brumano and Pizzo Mondello) . Our magne- tostratigraphic correlation reveals an apparent discrepancy in the first appearance of conodont M. posthernsteini between Pignola-Abriola and Steinbergkogel/Oyuklu. However, we infer that the forms attributed to M. posth- ernsteini at Steinbergkogel/Oyuklu are more similar to what we refer to as M. hernsteini/posthernsteini transition at Pignola-Abriola, a solution that virtually eliminates the discrepancy. Considering the taxonomic complexity of the M. hernsteini/posthernsteini lineage, we propose to place the Norian/Rhaetian boundary in correspondence of a marked negative shift of d13Corgobserved at Pignola-Abriola at ∼41.5 m (close to the FAD of M. posthern- steini),which, according to the correlation with the Newark APTS, would have an age of ∼205.6 Ma. According to this new definition of the Norian/Rhaetian boundary, the Rhaetian is ∼4.5 Myr-long.
File in questo prodotto:
Non ci sono file associati a questo prodotto.
Pubblicazioni consigliate

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11577/2958349
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus ND
  • ???jsp.display-item.citation.isi??? ND
social impact