The Judea Group (Late Albian–Turonian) is a lithologically diverse sequence of shallow-water carbonates deposited across the Israel-Sinai sub-plate. The biostratigraphy of the Judea Gr. has primarily been constructed using ammonites, ostracods and foraminifera. The Judea Gr. is the least studied in terms of the calcareous nannofossils.
Three boreholes were chosen for the biostratigraphic analysis in the Northern Negev (Israel). The study area lies on the western flank of the Northern Negev Anticlinorium, which contributes to the northeast-trending Syrian Arc system. For biostratigraphy, 69 samples from Kohal 1 (31°45'N 35°15'E), 57 samples from Massada 1 (31°30'N 35°37'E) and 43 samples from Zohar 1 (31°13'12"N 35°13'23"E) were taken at 0.3–18 m intervals.
The boreholes penetrate the Hazera Fm. with following members: Hevyon (dolomite, limestone, marls, clayey marls), 'En Yorqe'am (interbedded fossiliferous marlstone, argillaceous limestone, and dolomite), Zafit (dolomite, limestone interbedded with marlstone), and Avnon (chalk, marlstone, and nodular limestone, and dolomite).
The calcareous nannofossil assemblages are poorly preserved and quite impoverished and consist of 33 taxa (Kohal-1, Zohar-1) and 39 taxa (Massada-1).
In the Northern Negev Hazera Fm., the nannofossils and ostracod data identify the Hevyon Member as Early Cenomanian (Massada-1: nannofossil Zones UC1 and UC2, ostracod Zone UC-1) and Late Albian–Early Cenomanian (Zohar-1 nannofossil Zones: undivided interval Zones UC0–UC1 and Zone UC2; Kohal-1 nannofossil Subzones/Zones: UC0a-b, UC0c–UC1, UC2a, UC2b-c). Nannofossils from the 'En Yor'qeam Member specify the Early – Late Cenomanian age (nannofossil Zones UC2, undivided zones UC3–UC4) and the ostracod data suggest the Late Cenomanian age (Zone UC-3) in the Massada-1 and Kohal-1 boreholes. The Zafit member is the Middle – Late Cenomanian in all three boreholes Massada-1, Kohal-1 and Zohar-1 (nannofossil Zones: undivided interval UC3-UC4 Zones, Subzone UC5a). The Avnon Member is Late Cenomanian (nannofossil Subzones UC5a and UC5b) in Kohal-1.