Paleoenvironmental implications of magnetofossil occurrences in the Eocene-Oligocene marine sediments from the Monte Cagnero Section (Central Italy): Preliminary results
Abstract
The Monte Cagnero sedimentary section, which outcrops in the northeastern Apennines near Urbania in the Umbria-Marche Basin (Italy), contains well-exposed strata spanning the middle Eocene to lower Oligocene interval. We report results of environmental magnetism, nannofossils, and foraminiferal investigations from Bartonian to Rupelian at Monte Cagnero section. The data show a significant turnover in the paleoenvironmental parameters from 78 m.s.l. ( 38.7 Ma) to 102.5 m.s.l. ( 35.3 Ma). This interval with low magnetic susceptibility, IRM and ARM intensity below 35.3 Ma, does not contain a reliable paleomagnetic record, in contrast to that from the overlying, more strongly magnetized sediments. The upper section, from 35.3 Ma to 33.5 Ma, shown high IRM and ARM intensity, with high concentration of magnetofossils (SD magnetite particles determined by FORC diagrams and IRM acquisition curves), with high paleomagnetic stability and clearly defined magnetic polarity zonations. Nannofossils assemblages also suggest oligotrophic conditions associated with low nutrients contents, coincident with low magnetic intensity. The eutrophic conditions are observed in the high intensity magnetic interval. Our preliminary results suggest that magnetofossil abundance is therefore an important determinant of the paleomagnetic recording fidelity of Monte Cagnero sediments. Similar results were obtained in Eocene-Oligocene sections from Neo-Tethys, South Atlantic and Southern Oceans, suggesting a global event of low magnetization that coincides with a global cooling trend, started in the middle Eocene. However, further work is needed to assess the mechanisms of whether the preserved inorganic remains of magnetotactic bacteria can provide a useful paleomagnetic record.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMGP43D0799S
- Keywords:
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- 1505 Biogenic magnetic minerals;
- GEOMAGNETISM AND PALEOMAGNETISMDE: 1512 Environmental magnetism;
- GEOMAGNETISM AND PALEOMAGNETISMDE: 1527 Paleomagnetism applied to geologic processes;
- GEOMAGNETISM AND PALEOMAGNETISMDE: 1540 Rock and mineral magnetism;
- GEOMAGNETISM AND PALEOMAGNETISM