27. MICROFABRIC AND MICROCOMPOSITIONAL STUDIES OF PLIOCENE AND QUATERNARY SAPROPELS FROM THE EASTERN MEDITERRANEAN1Alan E.S. Kemp,2 Richard B. Pearce,2 Jennifer Pike,2 and John E.A. Marshall3 |
ABSTRACTAn electron-microscope analysis of the microfabrics and microcomposition of Mediterranean sapropels revealed distinctive types of lamina components and significant variation in preservation of laminae. Individual laminae are composed predominantly of (1) terrigenous silty clay, (2) organic (carbon) material, and (3) diatoms. Opal is rarely present, and where preserved, diatom floras show evidence for variable silica dissolution. It is suggested that most sapropels originally included abundant diatoms, but that these subsequently dissolved, and that the most commonly preserved lamina style of alternating organic and terrigenous laminae represents a "remnant" fabric. The diatom floras within the sapropels are consistent with palynofacies data that provide evidence for increased fluvial input, which leads to enhanced stratification. The preservation of fabrics within sapropels indicates increasing dominance of bottom-water anoxia during the sedimentation of individual sapropels. The bioturbation of the upper part of some sapropel horizons may reflect conditions after cessation of sapropel deposition. The evidence from microfabric studies thus supports models of sapropel formation involving increased nutrient input and water column stratification. |
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