Correlations by Planktonic Foraminifera of Some Tertiary Localities in Northern Italy

Abstract

Twenty-one localities in northern Italy have been correlated by means of planktonic foraminifera. They occur in the opima (N2= P21) to insueta zones (N7-8), and in the acostaensis (N16) and G. dutertrei (N17) zones. Correlation of many of the localities with the radiolarian C. virginis Zone (Sanfilippo et al., 1973) suggests that this zone extends relatively lower (to at least the upper part of the N2 Zone) in Italy. Correlations by planktonic foraminifera of some Tertiary localities in northern Italy INTRODUCTION Italian localities were examined in order to compare the correlations obtained by the use of planktonic foraminifera with those of Sanfilippo et al. (1973) using Radiolaria, primarily, but also diatoms, silicoflagellates, and calcareous nannofossils. The samples were collected by W. R. Riedel, and a preliminary report, including the descriptions of sample localities, was made by Sanfilippo (1971). Only those samples containing adequate species for correlation are included here. DISCUSSION The ranges of the 21 species used for correlation are shown in table 1. These ranges are based on published information; the papers chiefly relied on are included in the bibliography. Special weight was given to those published by Baumann (1970) in his study of the Paleogene of the central Appenine region. For brevity, to avoid taxonomic discussion, some species are retained in their conventional genera, contrary to my present belief. The correlation of the samples with the foraminiferal zones of Bolli (1966, 1970) and Blow (1969), as well as with Tertiary Italian stages, is shown in table 2. Berggren's (1972) correlation of these zones with the Italian stages is used. Only the species believed to be significant for correlation are listed for each sample. Thus, species included in table 1 are not necessarily listed when present. Catapsydrax dissimilis appears to be one of the most solution-resistant species and is usually abundant, when present. For this reason, the absence of this species from WRE-67 samples 76-78 was considered to be significant. The range of Globigerinita glutinata is apparently lower than is shown by many workers, with the exception of Jenkins (1971 ), who extended the range down into the Waitakian Stage which, according to Berggren (1972), should be correlated with Zone N2 (P21) and Zone N3 (P22). On the other hand, Globoquadrina dehiscens, which Jenkins also reported from the Waitakian, apparently does not extend below middle N4 (middle kugleri Zone) in the present samples. This range is in general agreement with that given by Vervloet (1966) in his study of the Tertiary of the southern Piemonte area of northern Italy. These correlations are relatively similar to those obtained by using other fossil groups; Sanfilippo et al. (1973) assigned the bulk of the samples to the radiolarian Calocycletta virginis Zone. This zone in the tropics has usually been correlated with foraminiferal zones from within N3 (P22) to N6 (e. g., Berggren, 1972), thus placing the top in micropaleontology, vol. 19, no. 2, pp. 235-238, april, 1973 235 This content downloaded from 157.55.39.176 on Sat, 09 Apr 2016 06:10:47 UTC All use subject to http://about.jstor.org/terms