Paleolimnological implications of Late Holocene sediments in the western Sea of Galilee, Israel.

摘要

A 143-cm UWITEC percussion core, collected from a water depth of ~10 m, about 1 km from the city of Ginosar on the western shore of the Sea of Galilee, was studied to infer input from East Galilee over the last ~4000 years. The core location is offshore the mouths of Amud and Tsalmon, two of the larger streams that drain the northeastern part of the Galilee Mountains and have formed Holocene alluvial deposits. Today these streams are seasonal and during some years have no flow. Changes in core lithology, grain size, elemental chemistry, and bulk carbonate-free 87Sr/86 Sr ratios and epsilonNd values indicate changes in lake levels and sediment delivery from the Galilee. The presence of mm- to cm-thick laminations in the bottom 20 cm of the core indicate that the lake was deeper than today from ~4000 to ~3500 cal yrs BP and became shallower reaching near modern depth by ~3250 cal yrs BP. Summertime daily afternoon windwaves caused by westerly wind coming across the Galilee Mountains creates counterclockwise gyres and sediment resuspension to the depth of about 10 m resulting in accumulation of massive sediments in zones shallower than ~10 m (Serruya, 1978). Two thick flood units were identified, one on top of the other, between 104 and 60 cm. Both show a fining upward trend. The earlier flood shows lithology and 87Sr/86Sr ratios and epsilonNd values similar to Amud drainage basin rocks and soils whereas the later flood shows affinity to Tsalmon drainage basin. Additional minor sediment delivery events are suggested by the presence in the sediment of Late Cretaceous to Eocene marine foraminifer fossils that are known to occur in carbonate rocks and their weathering products (Terra Rossa and Rendzina soils) exposed in the Galilee Mountains. An event that resulted in a hiatus occurred sometime between ~530 and ~1200 cal yrs BP.