High-resolution quantitative analyses of the planktonic foraminifera and calcareous nannofossils content have been carried out on IODP Leg 342 - Hole U1406A (Northwest Atlantic Ocean) in the core interval 10H2-2H4, plotting the abundance distributions of the biostratigraphically and quantitatively most significant species. Qualitative analyses have been used to identify the precise depth of marker bioevents. For almost the whole succession, remarkable magnetostratigraphic data were provided by previous literature. All chrons and subchrons in the interval C6Cn-C6AAr were recognized in core interval 10H2-4H1 and calibrated to the GPTS 2012, but no magnetostratigraphic data are available for the highest portion. The investigated succession falls between Sphenolithus delphix FO (First Occurrence) -uppermost Chattian bioevent- in core 10H2 and the Sphenolithus belemnos LO (Last Occurrence) -Burdigalian bioevent- in core 2H5, embracing the O7 (uppermost part)-M3 foraminiferal zone interval and the CN1b - CNM5 calcareous nannofossil zone interval. A calcareous plankton biochronological framework have been produced integrating calcareous plankton and magnetostratigraphic data. Calculated ages for the most significant recognized bioevents are: S. delphix FO 23.35 Ma, S. delphix LO 23.02 Ma, Paragloborotalia kugleri FO 23.00 Ma, Globoquadrina dehiscens FO 22.59 Ma, Sphenolitus disbelemnos FO 22.56 Ma, Helicosphaera carteri FCO (First Common Occurrence) 22.18 Ma, P. kugleri LO 21.23 Ma. Two hiatus have been recognized within core 4H, despite the previous literature that indicated only one. The first one in core 4H5 spans the interval 21.17-19.01 Ma and coincides with a phosphate-rich layer; the second in core 4H2 spans the interval from 18.87 Ma to 18.21 Ma and correspond to a glaconite-rich layer. The results obtained from Hole U1406A allow some considerations about potential reference bioevents concerning the still open issue of Burdigalian GSSP (Global Stratotype Section and Point).
Integrated Quantitative Calcareous Plankton Bio-Magnetostratigraphy of the Early Miocene from IODP Leg 342, Hole U1406A, New found land Ridge, NW Atlantic Ocean
2019
Abstract
High-resolution quantitative analyses of the planktonic foraminifera and calcareous nannofossils content have been carried out on IODP Leg 342 - Hole U1406A (Northwest Atlantic Ocean) in the core interval 10H2-2H4, plotting the abundance distributions of the biostratigraphically and quantitatively most significant species. Qualitative analyses have been used to identify the precise depth of marker bioevents. For almost the whole succession, remarkable magnetostratigraphic data were provided by previous literature. All chrons and subchrons in the interval C6Cn-C6AAr were recognized in core interval 10H2-4H1 and calibrated to the GPTS 2012, but no magnetostratigraphic data are available for the highest portion. The investigated succession falls between Sphenolithus delphix FO (First Occurrence) -uppermost Chattian bioevent- in core 10H2 and the Sphenolithus belemnos LO (Last Occurrence) -Burdigalian bioevent- in core 2H5, embracing the O7 (uppermost part)-M3 foraminiferal zone interval and the CN1b - CNM5 calcareous nannofossil zone interval. A calcareous plankton biochronological framework have been produced integrating calcareous plankton and magnetostratigraphic data. Calculated ages for the most significant recognized bioevents are: S. delphix FO 23.35 Ma, S. delphix LO 23.02 Ma, Paragloborotalia kugleri FO 23.00 Ma, Globoquadrina dehiscens FO 22.59 Ma, Sphenolitus disbelemnos FO 22.56 Ma, Helicosphaera carteri FCO (First Common Occurrence) 22.18 Ma, P. kugleri LO 21.23 Ma. Two hiatus have been recognized within core 4H, despite the previous literature that indicated only one. The first one in core 4H5 spans the interval 21.17-19.01 Ma and coincides with a phosphate-rich layer; the second in core 4H2 spans the interval from 18.87 Ma to 18.21 Ma and correspond to a glaconite-rich layer. The results obtained from Hole U1406A allow some considerations about potential reference bioevents concerning the still open issue of Burdigalian GSSP (Global Stratotype Section and Point).I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
