Holocene hydrological events and human induced environmental changes reflected in a southeastern Mediterranean fluvial archive

By: Avnaim-Katav S., Almogi-Labin A., Agnon A., Porat N., Sivan D.
Published in: Palaeogeography, Palaeoclimatology, Palaeoecology
SDGs : SDG 14  |  Units:   | Time: 2017 |  Link
Description: The chronostratigraphy of an eastern Mediterranean Holocene fluvial sequence reflects global trends (climate and sea-lev el), local modulations (hydrological regime and storm surges) and anthropogenic impact. Two continuous cores retrieved from the Tanninim Stream estuary, on the Carmel coast of Israel, are dated by optically stimulated luminescence (OSL) to span the Holocene. The sedimentology and faunal assemblages are analyzed for reconstructing environmental conditions. Despite time gaps recognized in the fluvial successions, three main depositional periods provide distinctive archives capturing natural and anthropogenic centennial to millennial changes. Alternations between enhanced and reduced fluvial activity associated with humid and dry climate conditions, characterized the early to mid-Holocene fluvial record between about 7.8 and 5.7 ka, and may match eastern Mediterranean climate records. The first humid phase, from 8 to 6 ka, features organic-rich fine sediments and proliferating brackish ostracods, foraminifera and molluscs. The appearance of this biofacies indicates the initiation of seepage from the Yarkon-Tanninim aquifer through the brackish oligohaline Enot Timsah springs. The advancing coastline, due to sea-level rise starting about 5.8 ka, resulted in an increasing supply of quartz sands and marine-transported foraminifera. Relatively fast accumulation of organic-rich fine-grained sediments with enhanced preservation of brackish fauna during the late Holocene is probably associated with maintenance of the Tanninim dams during the early Arab period (7th–8th centuries CE). The last century has been characterized by accelerated sedimentation rates that may be associated with reduced vegetation cover due to modern human activity, and by deposition by a high-energy surge event. This study demonstrates that the lower part of a semi-arid southeastern Mediterranean estuary responds to periods of climatic and sea-level change on a regional scale, and to human impact and abrupt past hydrological events on a local scale. © 2016 Elsevier B.V.