Implications of Submonthly Oxygen and Carbon Isotope Variations in Late Pleistocene Melanopsis Shells for Regional and Local Hydroclimate in the Upper Jordan River Valley

Many water-stressed regions of the globe have a highly seasonal precipitation regime. However, seasonality in the past and under changing climates is little studied. Submonthly records of sclerochronological delta O-18 and delta C-13 values of Melanopsis shells from the Jordan River Dureijat archaeological site (JRD) in the upper Jordan River valley presented here document the hydrology of paleo-Lake Hula. These records were assessed for changes in seasonal hydrology in the lake and compared with modern shells collected from present-day waterbodies in northern Israel and with models of delta O-18(shell). Results from shells in sediments dating from the last glacial maximum (LGM) to the Bolling-Allerod imply changes in waterbody size that qualitatively parallel changes in the late Pleistocene Lake Lisan levels; Hula Lake was well buffered when Lake Lisan stood at a high stand and poorly buffered when water levels were lower. Furthermore, data from shells dated to the LGM suggest inflowing water with lower delta O-18 values than local rainfall, providing evidence for a greater proportion of snow in the catchment than today. Reconstruction of water delta O-18 and mixing-model calculations suggest that snowmelt contribution to spring water during the LGM may have been more than twice the amount in the modern-day catchment.