DECLINE OF THE MAASTRICHTIAN PELAGIC ECOSYSTEM BASED ON PLANKTIC FORAMINIFERA ASSEMBLAGE CHANGE - IMPLICATION FOR THE TERMINAL CRETACEOUS FAUNAL CRISIS

An outer shelf-upper slope tropical Tethyan pelagic environment existe d over southern Israel during Maastrichtian time. Planktic foraminifer a in the >63 and >149 mu m size fractions from four sections in this a rea were studied quantitatively for a high-resolution ecostratigraphic analysis of the pre-Cretaceous-Tertiary (K-T) paleoenvironment. Durin g the Maastrichtian, 41% of the planktic foraminifera species became e xtinct, mostly keeled Globotruncanidae, which also became quantitative ly reduced near the end of the Maastrichtian from as much as 35% to on ly 5% of the planktic foraminifera population, Evolutionary replacemen t of extinct species by new forms nearly ceased in that interval. Two major opportunistic blooms of Guembelitria took place, associated with reduced abundances of keeled forms and the dominant species Heterohel ix globulosa. The first bloom occurred within the upper Gansserina gan sseri to lower Abathomphalus mayaroensis Zones and the second within t he Plummerita hantkeninoides Zone. The extinctions, concomitant change s in faunal dominance, and opportunist blooms indicate that the pelagi c ecosystem in the Negev area experienced multiple stresses during the Maastrichtian. The planktic foraminiferal assemblages were taxonomica lly impoverished and in decline prior to the K-T boundary crisis.