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Calcareous plankton bio-chronostratigraphy of the Maltese Lower Globigerina Limestone member

Baldassini N., Mazzei R., Foresi L., Riforgiato F., Salvatorini G.

Acta Geologica Polonica

2013

Vol. 63, no. 1

105-135

The planktonic foraminifera and calcareous nannofossil biostratigraphy of the Maltese Lower Globigerina Limestone member has been investigated. The member was dated to early planktonic foraminiferal P22 Zone and nannofossil NP25 Zone (upper Chattian). A climate-stratigraphic approach, based on the quantitative analyses of calcareous nannofossils, was used additionally to achieve a more precise chronology. The species Coccolithus pelagicus (diameter [is less than or equal to]11 [mu]m) and the genus Umbilicosphaera were selected for the recognition of cold and warm surface waters intervals respectively. The ratio of their percentages enabled the construction of a Climatic Factor (CLF) curve. The CLF values were consistent with a warm climatic phase, which is probably represented by the portion of the oxygen stable isotope curve of Miller et al. above the Oi2c event and below the beginning of the cooling trend that culminates in the Mi1 event. Considering these two climatic events and the upper boundary of the NP25 Zone, it can be inferred that the deposition of the Lower Globigerina Limestone member took place between 25.1 and 24.3 Ma.