A paleomagnetic and geochemical record of the upper Cochiti reversal and two subsequent precessional cycles from Southern Sicily (Italy)

Self Cite

172

108

A new chronology for the late Miocene of the Mediterranean is presented by combining magnetostratigraphic, biostratigraphic (planktonic foraminifera and dinoflagellates) and cycle-stratigraphic data. Long and continuous upper Miocene sections on Gavdos (Metochia section) and Sicily (Gibliscemi section) display cyclic alternations of homogeneous marls and sapropels and can be correlated on the basis of their distinct cyclic patterns. The Metochia section yields a good paleomagnetic signal and the position of 17 polarity reversals can be determined. The resulting polarity sequence allows an unambiguous correlation to the geomagnetic polarity time scale (GFTS). The paleomagnetic signal in the Gibliscemi section is too weak to determine a reliable polarity sequence, except for the lowermost part of the section. Detailed biostratigraphic analysis results in the identification of 13 planktonic foraminiferal and 9 dinoflagellate bioevents, which can all be accurately dated. The Tortonian/Messinian boundary, defined by the First Regular Occurrence (FRO) of the G. conomiozeu group, is determined in chron C3Br.k with an age of 7.12 Ma, according to the GPTS (CK95) of Cande and Kent [l].

Section: Integrated Stratigraphic Frameworkmentioning

confidence: 99%

Late Miocene magnetostratigraphy, biostratigraphy and cyclostratigraphy in the Mediterranean

Krijgsman¹,

Hilgen

Langereis³

et al. 1995

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172

108

“…Mostly, fine-grained sediments (clays, marls) were sampled with a low sedimentation rate (typically 5 cm=ka) and over a sufficiently large interval, thus averaging out, to a large extent, secular variation. In addition, early post-depositional processes typically smooth out the finer-scale variations of the geomagnetic field [37].…”

Section: Sections and Samplingmentioning

confidence: 99%

A Late Pleistocene clockwise rotation phase of Zakynthos (Greece) and implications for the evolution of the western Aegean arc

Duermeijer¹,

Krijgsman²,

Langereis³

et al. 1999

Palaeomagnetic measurements have been carried out on Eocene to Pleistocene sediments on the Ionian island of Zakynthos, NW Greece. Magnetostratigraphic constraints, biostratigraphic analyses of planktonic foraminifera and calcareous nannofossils provide a reliable time frame for these deposits. The results show that no significant rotation occurred between 8.11 and 0.77 Ma, but that Zakynthos underwent a 21.6º š 7.4º clockwise rotation between 0.77 Ma and Recent. Thus, our data indicate a rapid rotational event, in contrast to continuous rotation since 5 Ma as previously postulated [Laj et al., Tectonophysics 86 (1982) 45-67]. We speculate this late Pleistocene tectonic rotation phase to be linked to rapid uplift in the Greek region which results from rebound processes caused by (African) slab detachment underneath the Ionian islands.

“…The "lock-in depth" or depth lag may then be considerably larger [5]. Post-depositional diagenetic processes controlled by changing redox conditions, may, in addition, lead to the migration of Fe ions, which can cause a CRM at a depth of more than 1 m below the sediment-water interface [1,16]. Rock magnetic parameters may give an indication of the change in the character and concentration of the magnetic minerals.…”

Section: Rock Magnetismmentioning

confidence: 99%

“…Van Hoof et al [1] have suggested that, due to the changing paleoredox conditions, a migration of Fe z+ and Mn into mainly the lower white (i.e., on top of grey and below beige) layers will take place, leading to the formation of secondary magnetite. Therefore, a maximum delay in the lower white layer is most likely.…”

Section: Comparison Of the Upper Thvera Records From Sicily And Calabriamentioning

confidence: 99%

The upper and lower Thvera sedimentary geomagnetic reversal records from southern Sicily

Hoof¹,

Langereis²

1992

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Detailed paleomagnetic records of the upper and lower Thvera polarity transitions have been determined from Pliocenc marine marls in southern Sicily. The dominant magnetic mineral is fine grained magnetite. The two transitions have VGP paths following a great circle passing South America and the west coast of North America. There are strong indications that the VGP paths result from smoothing of the non-antipodal stable directions before and after the transitions. The upper Thvera transitional record is preceded by two excursions and followed by a third one. The first excursion is a sedimentary artefact caused by post-depositional migration of magnetic minerals and the third one by is caused by weathering of the sediment. The upper Thvera transition from Sicily is compared with the record from Calabria, about 250 km away. The two records show similarities as well as differences: both transitions have identical VGP paths, but in Calabria the transition is recorded lower in the sediment, the first and third excursions have different characters and the second one is not present. Apparently the registration of transitions of the Earth's magnetic field in sediments is strongly influenced by smoothing and diagenetic processes after deposition.