Oxygen availability effects on early diagenetic calcite dissolution in the Arabian Sea as inferred from calcareous dinoflagellate cysts

摘要: In oceanic regions with high primary production, such as the Arabian Sea, signals of proxies are often altered by diagenetic processes. The present study aims at assessing effects early diagenesis on calcareous dinoflagellate cysts, which represent a relatively new tool for reconstructing paleoenvironmental conditions within photic zone. For this purpose, surface sediment samples from and below oxygen minimum zone (OMZ) northeastern southwestern Sea have been analysed quantitatively their cyst content. calculated accumulation rates (ARs), relative abundances fragmentation values were compared to bottom water (BWO) content ARs organic carbon sample positions. Different patterns found in part Sea. SW, no relationship between BWO is distinguishable, distribution thought largely reflect production. NE, much higher all species OMZ comparison it. This interpreted result better calcite preservation OMZ, presumably due reduced oxic degradation matter. differential drop individual lower boundary NE well species-specific change abundance fragmentation, indicate different sensitivity dissolution species. These results show that can both absolute has be considered if using them reconstructions. Furthermore, it shown considerable occur above carbonate saturation horizon productive areas. However, substantially increased, soon concentrations too low OM. Under (within near OMZ), main factor controlling matter (OM) appears concentrations. levels (below f1500 m depth Sea) there seems an increasing influence bioturbation sedimentation rate OM its exposure time. presents example highly basin differences processes lead signal either dominated production (off Somalia) or secondary alteration Pakistan), although areas, depleted present. estimating metabolic CO2 (and probably H2S oxidation), not only but also other geochemical paleoredoxconditions included D 2002 Elsevier Science B.V. All rights reserved.