Pliocene-Pleistocene Calcareous Nannofossil Distribution Patterns in the Western Mediterranean

A detailed quantitative calcareous nannofossil analysis has been performed on 138 samples from the astronomically dated Monte del Casino section with the aim to identify and precisely date the most important calcareous nannofossil events across the Tortonian=Messinian boundary in the Mediterranean, and to unravel paleoceanographic conditions at times of sapropel formation during the Late Miocene. From the biostratigraphic perspective, the genus Amaurolithus provides three successive first occurrences (FOs): A. primus, A. cf. amplificus and A. delicatus, dated at 7.446, 7.434 and 7.226 Ma, respectively. Other bioevents include the base and top of the 'small reticulofenestrids' Acme, dated at 7.644 and 6.697 Ma, and the FO, FCO and LO of R. rotaria, dated at 7.405, 7.226 and 6.771 Ma. These events appear to be useful in improving biostratigraphic resolution in the Tortonian-Messinian boundary interval, at least for the Mediterranean. Quantitative analysis revealed changes in the calcareous nannofossil assemblage associated with the sapropels. The observed fluctuations suggest a single mechanism for sapropel formation in the Mediterranean during the late Neogene. Sapropels are characterized by a decrease in the total number of coccoliths, interpreted mainly as a reduction in calcareous nannofossil production due to increased siliceous plankton production during spring blooms; and an increase in reworked specimens, interpreted to reflect enhanced continental input via river run-off. An increase in abundance of the genus Rhabdosphaera can be explained by opportunistic behavior at the end of the spring bloom when nutrient levels start to become impoverished. As far as sea surface water temperature indicators are concerned, warm water D. pentaradiatus shows positive fluctuations in sapropels while cooler water D. intercalaris and C. pelagicus show negative fluctuations.

Section: Methodsmentioning

confidence: 99%

Section: Helicosphaera Sellii Fcomentioning

confidence: 99%

Calcareous nannofossil biostratigraphy of the M. del Casino section (northern Apennines, Italy) and paleoceanographic conditions at times of Late Miocene sapropel formation

Negri

Giunta

Hilgen

et al. 1999

“…The reader is referred to and Perch-Nielsen (1985) for the taxonomy of the calcareous nannofossil species considered in this paper. Advantages and limits of the application of the data-collecting methods are discussed in Backman and Shackleton (1983) and Rio et al (1990b), to which the reader is referred as well.…”

Section: Calcareous Nannofossilsmentioning

confidence: 99%

“…A variable degree of dissolution of other elements of the nannofossil assemblage (i.e., helicoliths and placoliths) is observed in these layers. Discoasterids are known to be dissolution-resistant and their percentages may be used as an indicator of the dissolution intensity (see references in Rio et al, 1990b). The high-frequency variations in discoasterid abundances are therefore interpreted as a preservational signal.…”

Section: The Discoasterid Groupmentioning

confidence: 99%

Integrated stratigraphy and astronomical calibration of the Serravallian/Tortonian boundary section at Monte Gibliscemi (Sicily, Italy)

Hilgen

Krijgsman²,

Raffi

et al. 2000

Self Cite

118

148

Results are presented of an integrated stratigraphic (calcareous plankton biostratigraphy, cyclostratigraphy and magnetostratigraphy) study of the Serravallian=Tortonian (S=T) boundary section of Monte Gibliscemi (Sicily, Italy). Astronomical calibration of the sedimentary cycles provides absolute ages for calcareous plankton bio-events in the interval between 9.8 and 12.1 Ma. The first occurrence (FO) of Neogloboquadrina acostaensis, usually taken to delimit the S=T boundary, is dated astronomically at 11.781 Ma, pre-dating the migratory arrival of the species at low latitudes in the Atlantic by almost 2 million years. In contrast to delayed low-latitude arrival of N. acostaensis, Paragloborotalia mayeri shows a delayed low-latitude extinction of slightly more than 0.7 million years with respect to the Mediterranean (last occurrence (LO) at 10.49 Ma at Ceara Rise; LO at 11.205 Ma in the Mediterranean). The Discoaster hamatus FO, dated at 10.150 Ma, is clearly delayed with respect to the open ocean. The ages of D. kugleri first and last common occurrence (FCO and LCO), Catinaster coalitus FO, Coccolithus miopelagicus last (regular) occurrence (L(R)O) and the D. hamatus=neohamatus cross-over, however, are in good to excellent agreement with astronomically tuned ages for the same events at Ceara Rise (tropical Atlantic), suggesting that both independently established timescales are consistent with one another. The lack of a reliable magnetostratigraphy hampers a direct comparison with the geomagnetic polarity timescale of Cande and Kent (1995; CK95), but ages of calcareous nannofossil events suggests that CK95 is significantly younger over the studied time interval. Approximate astronomical ages for the polarity reversals were obtained by exporting astronomical ages of selected nannofossil events from Ceara Rise (and the Mediterranean) to eastern equatorial Pacific ODP Leg 138 Site 845, which has a reliable magnetostratigraphy.Our data from the Rio Mazzapiedi-Castellania section reveal that the base of the Tortonian stratotype corresponds almost exactly with the first regular occurrence (FRO) of N. acostaensis s.s. as defined in the present study, dated at 10.554 Ma. An extrapolated age of 11.8 Ma calculated for the top of the Serravallian stratotype indicates that there is a gap between the top of the Serravallian and the base of the Tortonian stratotype, potentially rendering all bio-events in the interval between 11.8 and 10.554 Ma suitable for delimiting the S=T boundary. Despite the tectonic deformation and the lack of a magnetostratigraphy, Gibliscemi remains a candidate to define the S=T boundary by means of the Tortonian global boundary stratotype section and point (GSSP). © 2000 Elsevier Science B.V. All rights reserved.Ł Corresponding author. E-mail: fhilgen@geo.uu.nl 0377-8398/00/$ -see front matter © 2000 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 7 -8 3 9 8 ( 0 0 ) 0 0 0 0 8 -6 182 F.J. Hilgen et al. / Marine Micropaleontology 38 (2000)

“…Emiliania huxleyi appeared in the late Pleistocene becoming a major component of the coccolith assemblages from the base of the E. huxleyi Acme Zone, quantitatively defined and dated at 85 ka by Rio et al (1990), replacing Gephyrocapsa (Gartner, 1977;Thierstein et al, 1977;Rio et al, 1990;Raffi et al, 1993;Young, 1998). The dominance of E. huxleyi in the upper photic zone nannoflora of the Holocene and latest late Pleistocene is well documented both globally (e.g.…”

Section: Holocene -Latest Late Pleistocene Reticulofenestridsmentioning

confidence: 99%

Abnormal carbonate diagenesis in Holocene–late Pleistocene sapropel-associated sediments from the Eastern Mediterranean; evidence from Emiliania huxleyi coccolith morphology

Crudeli

Young

Erba

et al. 2004

In studying the Holocene -late Pleistocene record of the Eastern Mediterranean, considerable Emiliania huxleyi size/shape variation not clearly assignable to primary or secondary calcification was observed. Accordingly, different morphotypes were distinguished by light microscope (LM).A subsequent scanning electron microscope (SEM) analysis of selected samples has indicated that Emiliania huxleyi coccoliths are variably affected by carbonate diagenesis in these sediments. A series of diagenetic stages were qualitatively defined, comprising well-preserved specimens, three overgrowth (OG1 to OG3) and one etching (E1) stage. Comparing SEM and LM observations, a tentative correlation between the E. huxleyi calcified LM-morphotypes and E. huxleyi SEM-overgrowth stages is proposed here.Our study not only indicates that Emiliania huxleyi coccoliths are strongly influenced by carbonate diagenesis, but also that they show effects of carbonate precipitation and dissolution much more clearly than other coccoliths. The relative abundances of the different LM-morphotypes were used to define an E. huxleyi overgrowth index (EXO) that qualitatively estimates carbonate precipitation/dissolution on coccoliths in this sediment. This resulted in definition of five ''Diagenetic'' intervals (D1 to D5). Deposition of sapropel S1 was a time of good preservation with variable dissolution and no overgrowth of E. huxleyi coccoliths, whereas calcite overgrowth was high during the Last Glacial Maximum (LGM) and interglacial period and, to a lesser extent, during the Younger Dryas and through the last 5 ka. D