QUANTITATIVE CALCAREOUS NANNOFOSSIL BIOSTRATIGRAPHY OF PLIOCENE AND PLEISTOCENE SEDIMENTS FROM THE ERATOSTHENES SEAMOUNT REGION IN THE EASTERN MEDITERRANEAN 1

Quantitative methods were used to document the abundance patterns of selected Pleistocene and Pliocene calcareous nannofossil species from four Ocean Drilling Program sites in the Eratosthenes Seamount region of the Eastern Mediterranean. Results show that many similarities exist between the species abundance patterns reported in this study and the abundance patterns from other geologic sequences in the Western and Central Mediterranean. Unconformities, likely associated with Pleistocene tectonic movement of the subducting Eratosthenes Seamount, limit the correlation of some biostratigraphic events. Despite the limitations caused by local tectonic erosion at Sites 965, 966, and 968, the geologic section recovered from Site 967 appears minimally affected and presents a high-resolution reference section for the Eastern Mediterranean. Three biostratigraphic events are proposed to refine correlation of the Pliocene geologic sections in the Eastern Mediterranean. 7 us lo ica ec a th do m e f th aphic n are t curcorn of rities henes earlier cola Ions in 88). logic cterisstratin are diterunzonal vents INTRODUCTION Ocean Drilling Program (ODP) Leg 160 drilled holes at 11 sites in the Central and Eastern Mediterranean Sea. This study details the quantitatively derived abundance patterns of selected Pleistocene and Pliocene calcareous nannofossil species observed in samples collected from four of the Leg 160 sites. Sites 965, 966, 967, and 968 were drilled along a south-to-north transect across the Eratosthenes Seamount in the Eastern Mediterranean (Fig. 1). The sedimentary cover on the Eratosthenes Seamount can be generally divided into three lithologic units: (1) Pleistocene through Pliocene nannofossil and foraminiferal oozes that contain numerous sapropel layers, (2) Miocene reefal carbonates devoid of planktonic microfossils, and (3) middle Eocene and Upper Cretaceous chalks, which contain numerous, albeit poorly preserved, microfossil assemblages (Emeis, Robertson, Richter, et al., 1996). The Pleistocene and Pliocene sediments collected from the Eratosthenes cores reflect a history of pelagic and hemipelagic sedimentation in a tectonically active depositional environment. In each hole studied, incomplete geologic sections that contain unconformities are evidenced from missing biostratigraphic zones or unrealistically compressed zones. The lack of synchroneity in the unconformities among holes suggests that local erosion related to faulting and slope failure along the flanks of the subducting seamount has likely resulted in the apparent hiatuses. Previous studies have proposed Neogene Mediterranean zonation schemes (Schmidt, 1973; Müller, 1978; Ellis and Lohman, 19 Raffi and Rio, 1979; and Rio et al., 1990). Other studies have quantitative methods to collect species abundance data from geo sections in the Central and Western Mediterranean and graph display the abundance patterns of significant nannofossil sp (Driever, 1981, 1988; Rio, 1982; Rio et al., 1990; Channell et 1992; Sprovieri, 1993; and Castradori, 1993). This study follows zonation scheme and quantitative methods of Rio et al. (1990) to ument the abundance patterns of selected species collected fro Eratosthenes Seamount region of the Eastern Mediterranean. Th mary focus of this study is on the biostratigraphic applications o 1Robertson, A.H. F. , Emeis, K. -C. , Richter, C. , and Camerlenghi, A. (Eds.), 1998. Proc. ODP, Sci. Results, 160: College Station, TX (Ocean Drilling Program). 2Texas Microscopy, 4812 Hanover Drive, Flower Mound, TX 75028, U.S.A. 3Present address: BP Exploration, PO Box 4587, Houston, TX 77210-4857, U.S.A. staer1@airmail.net 9; ed gic lly ies l. , e cthe prie observed species abundance trends to determine if biostratigr events documented from the Central and Western Mediterranea present in the Eratosthenes region, and to determine if events no rently used in the Rio et al. (1990) zonation scheme are useful for relation in sections throughout the Mediterranean. A discussio the species abundance trends is included to emphasize simila and differences between abundance patterns from the Eratost Seamount sites and the abundance patterns presented from studies of the Tyrrhenian Sea (Rio et al., 1990), Monte San Ni section in Southern Sicily (Channell et al., 1992; Driever, 1988), ian Sea (Castradori, 1993), Aghios Vlassios and Finikia section Crete (Driever, 1988), and Singa section in Calabria (Driever, 19 Through comparison of the Eratosthenes sites to other geo sections, this study suggests that many of the abundance chara tics of Pliocene and Pleistocene species that are used as bio graphic markers in both the Central and Western Mediterranea consistent markers in the Eratosthenes region of the Eastern Me ranean. Additionally, the study provides further evidence that ab dance characteristics of three discoasters, currently unused as markers in the Rio et al. (1990) zonal scheme, are consistent e Figure 1. Location of drill sites along a south-to-north transect above the Eratosthenes Seamount in the Eastern Mediterranean. Bathymetry is in meters.