Subsurface late Cenozoic palynostratigraphy of the Hula basin, Israel

128 pollen spectra obtained from a 2 871 m deep borehole in the Hula Basin, north-eastern Israel, are the basis for a palynostratigraphic subdivision of the late Cenozoic sequence in this region. The upper part of this sequence was previously studied in detail in other boreholes, and together serve for a paleoclimatic reconstruction. The sequence is divided into 14 distinct palynostratigraphic zones. The lowermost two of Miocene age, the succeeding two of Pilocene and the upper 10 of the Quaternary. The penetrated sequence consists of alternations of lacustrine, paludine, fluviatile and volcanic rocks. The middle Miocene Mb palynozone comprises at least 300 meters, the base of which was not penetrated, of fluviatile sediments of the Herod formation and volcanics of the Lower Basalt, which had been deposited in a river system leading eastwards to the Persian Gulf. The late Miocene Mc consists of some 500 m of fluviatile sedimens and basalts, for which no correlative outcrop is known. It is not clear whether these have been deposited in a taphrogenic basin in the Hula area or in a drainage system leading to such a basin existing in these times in the central Jordon Valley. The Pliocene palynozones, Pa and Pb, comprise mainly lacustrine and fluviate sediments with some volcanics deposited in an intermediate basin leading to the Mediterranean, in which the Kefat Gil'adi group was laid down. The Preglacial Pleistocene QI palynozones represents a river system flowing from the east to the Mediterranean, for which the Hula was only an intermediate basin. The sediments are interfingrred by flows of the Cover Basalt. Palynozones QII through OX are mostly lacustrine or paludine deposits, have been formed in the Hula Basin since its downfaulting started at the beginning of the Glacial Pleistocene. Ever since, the Hula is part of the Levantine faulting system, or the Jordan-Dead Sea rift. These sediments are also intercalated by some basalt flows. The pollen spectra indicate that the vegetation was tropical to subtropical in middle Miocene times, disertic in late Miocene, temperate in the Pliocene, warm humid temperate in Preglacial Pleistocene times and Mediterranean from the beginning of the Glacial Pleistocene, a character the flora retained through the present day. Pluvials and interpluvials of the Glacial Pleistocene caused changes in the vegetation cover, with some dominance of certain plants over others, all within the Mediterranean nature.