The age of the Miocene-Pliocene boundary in the Capo Rossello area (Sicily)

116

The results of a detailed magnetostratigraphic and biostratigraphic study of late Pliocene to early Pleistocene marine marl sequences from the Monte Singa and Crotone areas in Calabria, Italy are presented.The magnetostratigraphy from the Monte Singa sequence ranges from below the Gauss/Matuyama boundary up to and including the lower Olduvai boundary. Normal polarities at a level corresponding to isotope stage 81 most probably represent the R~union subchron. From the lower Olduvai boundary upward, a reliable magnetostratigraphy could not be established due to increased weathering of the marls, resulting in mainly secondary magnetizations.The magnetostratigraphy from the composite sequence of the Crotone area belongs to a large part of the Matuyama Chron and includes the Olduvai subchron. The position of the lower and upper boundaries of the Olduvai subzone could be established more precisely than from earlier results. Moreover, the upper boundary of the Olduvai subzone poses an ambiguity: a relatively long normal polarity interval representing the main Olduvai subchron and corresponding to a duration of 115 ka is followed by a short (30 ka) reversed subchron and the short (15 ka) normal Vrica subchron. Another option, and more in accordance with the duration of the Olduvai subchron in literature, would be to consider the complete N-R-N polarity succession with a total duration of 160 ka as representing the Olduvai subchron, implying that this Olduvai subchron has a short reversed interval in its upper part.Linear interpolation and extrapolation yield ages for the most important late Pliocene-early Pleistocene biostratigraphic datum levels. An age of 1.69 Ma is found for the Pliocene-Pleistocene boundary, using the conventional polarity time scale dated with radiometric results. However Hilgen [1], in correlating the sapropel groups and patterns to the precession curve of the Earth's orbit, obtained significantly different ages for the polarity transitions of the present study. According to this astronomically calibrated polarity time scale, the age of the Pliocene-Pleistocene boundary is 1.81 Ma.

Section: Introductionmentioning

confidence: 99%

Integrated magnetostratigraphy and biostratigraphy of the upper Pliocene-lower Pleistocene from the Monte Singa and Crotone areas in Calabria, Italy

Zijderveld¹,

Hilgen²,

Langereis³

et al. 1991

116

“…1) [11]. The Eraclea Minoa section forms the basal part of the Rosscllo composite section [12] and it consists of marine marls of the Pliocene Trubi Formation (Fig.…”

Section: Geological Setting and Samplingmentioning

confidence: 99%

“…The average sedimentation rate during the Thvera subchronozone has been established at 4.4 (upper Thvera) to 5.0 (lower Thvera) cm/kyr [11,13,16]. The sedimentation rate during the deposition of the grey and beige marls could be somewhat higher due to increased continental run-off and a constant carbonate flux [14], or somewhat lower due to increased carbonate production in the white marls while the flux of the non-carbonate fraction is constant [31].…”

Section: The Sicilian Lower and Upper Tht~era Recordsmentioning

confidence: 99%

“…9) by averaging the directions over a sedimentary interval just before or after the transitions where the changes in directions are due to noise. The stable directions of the polarity zones before, during and after the Thvera subchronozone from the magnetostratigraphic study of the Eraclea Minoa by Hilgen and Langereis [11] are shown in Table 1, together with the near transitional directions. The mean directions of the previous reversed polarity zone and the Thvera subchronozone show a marginally positive reversal test (class C) [26], while the mean directions of the subsequent polarity zone and the Thvera subchronozone, as well as the near transitional directions, have negative reversal tests.…”

Section: The Sicilian Lower and Upper Tht~era Recordsmentioning

confidence: 99%

See 1 more Smart Citation

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

Hoof¹,

Langereis²

1992

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.

“…This distinct lithohorizon reflects the re-establishment of open-marine conditions in the Mediterranean following the Messinian salinity crisis at the beginning of the Pliocene [6]. Accurate, first-order age estimates for this horizon have been obtained from several sections other than Capo Rossello and range from 4.81 to 4.93 Ma [7][8][9]. All these ages are based on the straightforward calibration of magnetostratigraphic records to the geomagnetic polarity time scale (GPTS) of Berggren et al ( [1], BKFV85) in combination with a downward extrapolation of the sediment accumulation rate and/or the average duration of sedimentary cycles.…”

Section: Introductionmentioning

confidence: 99%

A critical re-evaluation of the Miocene/Pliocene boundary as defined in the Mediterranean

Hilgen

Langereis²

1993

A critical re-evaluation of the Miocene/Pliocene (M/P) boundary as defined--informally--in the Mediterranean is presented. We show that ages reported earlier for this boundary (ranging from 4.81 to 4.93 Ma) do not imply any diachroneity of the basal Zanclean lithohorizon which reflects the Pliocene flooding of the Mediterranean and defines the M/P boundary. These ages most likely represent an artefact resulting from intraformational variations in sedimentation rate and inconsistent interpretation of coluor variations in terms of sedimentary cycles. The best estimate for the age of this boundary arrives at 4. Because of its presumably global paleoclimatological significance, the M/P boundary as currently defined in the Mediterranean is preferred to a redefinition of this boundary at the Gilbert/Chron 5 boundary in a continuous open-marine sequence outside the Mediterranean. In addition, this redefinition would lead to unnecessary confusion in global chronostratigraphy.