Hydrographic, Deltaic and Benthogenic Controls of Sediment Dispersal in the Gulf of İskenderun, SE Turkey (E. Mediterranean)

Abstract

Grain size, carbonate and organic carbon data obtained from a total of 73 surficial bottom sediments together with some available hydrographic data were used to investigate the major depositional characteristics and the sediment transport paths on the shelves of the Gulf of İskenderun.Sediments with more than 30% biogenic carbonate composed of a variety of benthic organisms' remains have formed a belt on the sea-floor of the gulf entrance which extends northwards to the offshore Ceyhan Delta and eastward along the southern coast. North-westerly and easterly flowing open-sea currents, low terrigenous sedimentation, bathymetry and high topographic relief of the coastal hinterland seems to be responsible for the formation of this benthogenic bottom zone. The two other benthogenic bottom zones found in the eastern and north-eastern parts of the gulf are under the influences of increased anthropogenic activities and ephemeral fluviatile input of terrigenous material.The typical seaward profile of the offshore Ceyhan Delta, near-shore delta-front, pro-delta and offshore facies, was actively modified by current action. The ratio of silt – clay, clay – medium silt, clay – coarse silt, and fine silt – coarse silt fractions of the sediments revealed the occurrences of at least two distinct patterns of concentric zonal depositions, which are in good agreement with the prevailing hydraulic gyre regimes in the gulf. These depositional zonal patterns are characterized by the increased fractionation processes that separate finer-grained and coarser-grained fractions whereby clay contents increase towards the centres of these gyres, predominantly in an offshore direction. Similar zonal deposition was also mirrored by the organic carbon contents of sediments.We propose patterns of water movement and sediment pathways in the Gulf of İskenderun based upon the interpretation of water-current data and analysis of sedimentological data. Particular conditions for transportation and deposition of terrigenous materials and benthic accumulation are discussed. This model produces a database for understanding dispersal of pollutants in association with water and fine-grained sediment in this gulf.opyright 1998 Academic Press Limited