Stratigraphy and Isotope Records of Middle and Late Pleistocene Mollusks from a Continuous Corehole in the Hula Basin, Northern Jordan Valley, Israel

Abstract

Morphological changes in Melanopsis shells and the sudden disappearance of Viviparus were observed in a continuous core, representing about 700,000 yr, taken from the L-12 corehole in the Hula Basin, northern Jordan Valley, Israel. Two major events in δ¹⁸O values are recorded. The first, at about 435,000 yr B.P., is accompanied by a shift in δ¹³C values and indicates a shallowing phase with slightly higher evaporation. This event is concurrent with the abundant occurrence of a monotypic “distorted” Melanopsis, suggesting an “ecophenotypic event” during deposition of the lake's Pleistocene lower Lacustrine beds. The second major isotopic event is evidenced in the lower part of the section as a gradual depletion in ¹⁸O toward the bottom of the corehole. Minor shifts of 1–20‰ in the oxygen isotope content along the core may represent changes in the δ¹⁸O values of the water from glacial to interglacial periods representing the major climatic cycles of the Pleistocene. Five of these cycles were observed along the core.