Combined ostracod and planktonic foraminiferal biozonation of the Late Coniacian – Early Maastrichtian in Israel

The distribution and zonation of planktonic foraminifera and ostracods during the Late Coniacian – Early Maastrichtian succession in Israel was studied in detail from six surface sections. The combination of contemporaneous biozones led to a more accurate age determination of the local ostracod zones, according to the Tethyan planktonic foraminiferal zonation. The configuration of the biozones of both taxa presents more datum lines for stratigraphic correlation of the Senonian strata of Israel. Three new ostracod species were described from Campanian sediments: Cytherelloidea zinensis, Loxoconcha hebraica and Cristaeleberis ordinata.


INTRODUCTION
Late Coniacian -Maastrichtian marine formations of the Mount Scopus Group (Flexer, 1968) are widely distributed in Israel. They are mostly composed of chalks, mark, cherts and phosphorites. A renewed interest in Senonian rocks of Israel was evoked after the micropaleontological studies of Moshkovitz (1984; calcareous nannofossils) and Honigstein (1983Honigstein ( , 1984ostracods). Additional biostratigraphic data on ostracods are recorded in Lipson-Benitah et al. (1985; combined with foraminifera) and in Lifshitz et al. (1985). Reiss et al. (1985) summarised multiple bio-and chronostratigraphic data from the Senonian of Israel, based on ranges of indicative species of megafossils (mainly ammonites), planktonic and benthic foraminifera, calcareous nannoplankton, and ostracods. A modified biostratigraphic chart, on the base of ranges of 54 Globotruncanidae species, was presented in Almogi-Labin et al. (1986) and the results were compared with the general European zonation of Robaszynski et al. (1984). In this study, the local ostracod zones are correlated with the more general planktonic foraminiferal zonation.
The combined biozonation i s based on former results (Honigstein, 1983, Reiss et al., 1985 and on six additional surface sections (Table 1, coordinates in Israel grid; Fig. 1). These profiles were chosen to be representative for a detailed bio-, litho-and chronostratigraphic study. Studies on other microfossil groups (from the same "type-" sections) are in preparation. Both planktonic foraminifera and ostracods were studied from the same samples, except those of the Ein Fawwar section (see Fig. 1). The distribution of the planktonic foraminifera and their ranges were determined here by Almogi-Labin and the ostracods by Honigstein and Rosenfeld. The results are depicted in Figs. 3-12. Species with limited taxonomic and stratigraphic importance are omitted, such as Arcaeoglobigerina cretaceu and A . blowi (foraminifera), and Bythocrypris windhami, Cytherella cf. C. austinensis, Bunlonia? aff. 6 . cretacea, Buirdoppilata pondera and Spinoleberis megiddoensis (ostracods). The investigation of more than 400 samples led also to a modification of the general distribution chart of Senonian ostracods from Israel (Fig. 7 ) . A calibrated scheme of ostracod versus planktonic foraminiferal zones is given in Fig.  13.
The samples from the studied sections, their washed residues, as well as the picked foraminifera, are deposited in the Micropaleontological Collection of the Geological Department of the Hebrew University, Jerusalem, catalogued with the Laboratory prefix HU-. The ostracod material is stored at the Micropaleontological Laboratory of the Geological Survey of Israel. Jerusalem.

Planktonic foraminifera
The planktonic foraminiferal fauna which occurs in our material was discussed in detail in Reiss et al. (1985Reiss et al. ( , 1986 and Almogi-Labin et al. (1986), where also Globotruncanidae species were figured. In the present study, species of Heterohelicidae of stratigraphical importance in the Santonian -Campanian were recorded in the distribution charts (Figs. 3, 5 , 7, 11).

CORRELATION USING PLANKTONIC FORAMINIFERAL AND OSTRACOD BIOZONATION
The distribution of the ostracods and planktonic foraminiferal assemblages within the six studied sections (Figs. 3-12), as well as from previous works (Honigstein, 1983;Reiss et al., 1985), led to the following correlations of biozones, as presented in Fig.  13.
The Phyrocythere lata (S-1) assemblage zone of Late Coniacian age (Honigstein, 1984) was correlated in a northern Israel borehole section  with the Marginotruncana angusticarenata zone (Lipson-Benitah, 1980). According to Lipson -Benitah (in press), at least the upper part of the S-1 zone, which was observed in Bar'am ( Fig. 6), Nahal Ya'alon ( Fig. 8) and Nahal Zin (Fig. lo), belong to the lower part of the Dicarinella concavata zone (Robaszynski et al., 1984). The planktonic foraminifera of this The Coniacian/Santonian boundary is problematic, but may be tentatively placed at the top of the S-1 zone. The Santonian succession is represented by high populations of ostracods and foraminifera. The Dicarinella concavata and Dicarinella 'asymetrica zones can be correlated with the Cythereis rosenfeldi rosenfeldi (S-2) and Limburgina miarensis (S-3) assemblage zones. Their biozone boundaries alternate (Ein el Qilt,Bar'am,Nahal Ya'alon,. The Santonian in the Nahal Zin section (Figs. 9-10) is reduced to about 5m; the Dicarinella asymetrica zone was probably therefore not observed because of the poor preservation of the foraminifera however, all ostracod zones were found.
The SantonianICampanian boundary is defined by the common base of the Leguminocythereis dorsocostatus (S-4) and Globotruncanita elevata zones (Figs.  3-10). The Globotrunicanita elevata zone, indicative for the Early Campanian period, correlates to the S-4 zone and it its top, to the base of the Brachycythere beershevaensis ( S -5 ) assemblage zone (Nahal Ya'alon, Fig. 8; Tarqumiya, Fig. 12). The diversity of planktonic foraminifera in the Tarqumiya section (Fig. 11) within the Early Campanian is much higher, the specimens are larger and contain a higher percentage of adults than in the Ein Fawwar exposure (Fig. 3). The ostracod diversity in these sections remains more or less constant, but the total ostracod content in the samples from Ein Fawwar is higher. These observations enhance the general W-E trend of planktonic foraminifera decrease and ostracod increase (Flexer & Honig-Honigstein el al. stein, 1984).
The S-5 zone can be compared with the Late Campanian Globotruncana rosetta and the latest Campanian Globotruncanita calcarata zones . Therefore, the former range of this ostracod zone, which can sometimes be subdivided into the subzones 5a and 5b (Honigstein, 1984: upper part of Early Campanian) must be extended into the Late and latest Campanian. The Late Campanian S-5* subzone was recognised only from southern Israel (Honigstein, 1984;present paper: Nahal Ya'alon, Fig. 8; Nahal Zin, a ;. falsos? Fig. 10). Two new ostracod species were found in the Nahal Zin section within this subzone, accompanying the usually rare and low diversity fauna. The S-5b subzone, contemporaneous with the Globotruncanita calcarata zone (Bar'am;Tarqumiya,, can be differentiated from the S-5a subzone by the first occurrence of Veeniacythereis tenyetensis and Cythereis ornatissirna (Fig. 2). Moreover, a higher ratio of pitted forms of Brachycythere and Protobuntonia versus the reticulated specimens of Ventrocythereis is found in the S-5b subzone. The Campanian/Maastrichtian boundary is not clear-The combination of contemporaneous occurrences of ly defined in the Israeli succession (Reiss et al., 1985, ostracod and planktonic foraminifera1 biozones enables 1986) and cannot precisely be dated by planktonic us to date the local ostracod biostratigraphy according foraminifera (disappearance of Globotruncanita cafcarto the regional Tethyan planktonic foraminiferal zonautu) and the rare ostracod fauna. The Early Maastrich-tion. The use of both taxa, ostracods and planktonic tian is determined in the present study with the foraminifera, provides more datum lines and allows a common range of the Giobotruncana falsostuarli and finer resolution of the Senonian stratigraphy.