Abstract
An environmental and geochemical investigation of 33 surficial sediments of the continental shelf north and north east of Lesvos Island Greece was undertaken to study the mineralogy and geochemistry of the sediments and understand the distribution and sources of various major and trace elements. Texturally all the sediments contain high amounts of mud and clay indicating a uniform facies at depths between 30m - 300m. The sediments are a mixture of terrigenous components (albite, K-feldspar, muscovite, quartz, illite, amphibole and biogenic components (calcite, Mgcalcite, aragonite). Pyrite and glauconite are ascribed to diagenesis. There are four distinctive groups of elements each of which includes related elements, derived from different natural sources on land or in the marine basin. The first group (Ca, Sr) reflects the biogenous carbonate fraction and is negatively correlated against every other element determined. A second (Si, Al, Fe, Na, K, Ti, Ba and Zr) group reflects the aluminosilicate minerals derived from the alteration of volcanic rocks, and a third group (Mg, Ni, Cr, C and Zn) reflects the aluminosilicate minerals derived from the alteration of ultrabasic rocks (peridotites) and the organic carbon. The group of Fe, Mn, Zn and Y is a diagenetic association reflecting the distribution of these elements with pyrite. The association of Cu with Zn reflects a mineralization control in the sediment area. Finally, La and Ce are associated with the K-bearing minerals, while P is related to K and Fe-finegrained minerals. The concentrations of heavy metals in the sediments are normal comparing to the contents of other AEGEAN SEA sediments and are due to natural lithogenic sources.
Highlights
It is known that the continental shelf represents a complex sedimentary environment
Because the shelf sediments are affected by recent tectonics they may be composed of relict, reworked or recent sediments in various combinations
More information on the chemical composition of south Aegean Sea sediments has been reported by Smith & Cronan [5]
Summary
It is known that the continental shelf represents a complex sedimentary environment. Various physical, geological and geochemical processes control sediment deposition in this environment.The distribution of elements in shelf sediments is affected by several factors such as sedimentation rates which are much higher and physico-chemical conditions which are quite different than those in the open ocean. Geological and geochemical processes control sediment deposition in this environment. Few marine geological studies have been carried out of bottom sediments of the Aegean Sea and these have provided sparse information on the chemical composition of the sediments [2,3,4]. More information on the chemical composition of south Aegean Sea sediments has been reported by Smith & Cronan [5]. The first mineralogical – geochemical study of the Lesvos Sea sediments was that of Kelepertsis & Chatsidimitriadis [6].
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