A detailed magnetostratigraphic investiga- tion of the Pignola-Abriola section of Norian to Rhaetian age permits the identification of 22 magnetic polarity reversals grouped in 10 magnetozones. We correlate the magneto- stratigraphy of the Pignola-Abriola section with the Newark astrochronological polarity time scale (APTS). In total, 19 correlation options were tested, and only one (option 7) yielded a statistically significant correlation that was consistent with the available infor- mation on the stratigraphic age of the Newark APTS. After some adjustments to minimize erratic variations in sediment accumulation rates, a final correlation (option 7.1) was used to generate an age model of sedimentation for the Pignola-Abriola section. The Pignola- Abriola section has been correlated with Rhaetian sections from the literature, notably the current global boundary stratotype sec- tion and point candidate for the base of the Rhaetian at Steinbergkogel, Austria, where the Norian-Rhaetian boundary is proposed to be placed at a stratigraphic level contain- ing the first appearance datum (FAD) of conodont Misikella posthernsteini, traced on the Newark APTS to ca. 209–210 Ma. Issues regarding the taxonomy of M. posthernsteini, a species characterized by transitional forms with its ancestor Misikella hernsteini, lead us to propose the alternative option of placing the Norian-Rhaetian boundary at a prominent negative δ13C spike observed in the Pignola- org Abriola section at meter 44.5, 50 cm below the level containing the FAD of M. posthernsteini sensu stricto and close to the base of radiolarian Proparvicingula moniliformis zone. This level has been magnetostratigraphically cor- related to Newark magnetozone E20r.2r at ca. 205.7 Ma. Assuming an age of ca. 201.3 Ma for the Triassic-Jurassic boundary, the Rhaetian Stage would have a duration of ~4.4 m.y.
Magnetostratigraphy, biostratigraphy, and chemostratigraphy of the Pignola-Abriola section: New constraints for the Norian-Rhaetian boundary
MARON, MATTEO;RIGO, MANUEL;ZAFFANI, MARIACHIARA;
2015
Abstract
A detailed magnetostratigraphic investiga- tion of the Pignola-Abriola section of Norian to Rhaetian age permits the identification of 22 magnetic polarity reversals grouped in 10 magnetozones. We correlate the magneto- stratigraphy of the Pignola-Abriola section with the Newark astrochronological polarity time scale (APTS). In total, 19 correlation options were tested, and only one (option 7) yielded a statistically significant correlation that was consistent with the available infor- mation on the stratigraphic age of the Newark APTS. After some adjustments to minimize erratic variations in sediment accumulation rates, a final correlation (option 7.1) was used to generate an age model of sedimentation for the Pignola-Abriola section. The Pignola- Abriola section has been correlated with Rhaetian sections from the literature, notably the current global boundary stratotype sec- tion and point candidate for the base of the Rhaetian at Steinbergkogel, Austria, where the Norian-Rhaetian boundary is proposed to be placed at a stratigraphic level contain- ing the first appearance datum (FAD) of conodont Misikella posthernsteini, traced on the Newark APTS to ca. 209–210 Ma. Issues regarding the taxonomy of M. posthernsteini, a species characterized by transitional forms with its ancestor Misikella hernsteini, lead us to propose the alternative option of placing the Norian-Rhaetian boundary at a prominent negative δ13C spike observed in the Pignola- org Abriola section at meter 44.5, 50 cm below the level containing the FAD of M. posthernsteini sensu stricto and close to the base of radiolarian Proparvicingula moniliformis zone. This level has been magnetostratigraphically cor- related to Newark magnetozone E20r.2r at ca. 205.7 Ma. Assuming an age of ca. 201.3 Ma for the Triassic-Jurassic boundary, the Rhaetian Stage would have a duration of ~4.4 m.y.
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