The preservation of productivity proxies is discussed separately because Ba has been extensively used as a recorder of past productivity in all Mediterranean basins and deserves particular attention. Regardless of the poor understanding of the mechanisms of barite Dactolisib in the water column, barite has shown to be a useful proxy for reconstructing paleoproductivity responsible for sapropel deposition events in the eastern Mediterranean, and for other productivity fluctuations in the western regions as discussed above. Barite preservation in marine sediments has been discussed and investigated (e.g., McManus et?al., 1998, Schenau et?al., 2001, Robin et?al., 2003 and van Beek et?al., 2003) though uncertainties remain regarding the diverse parameters influencing such preservation (Schenau et?al., 2001, Paytan and Griffith, 2007 and Griffith and Paytan, 2012). Deep-water saturation state, sedimentation rates, and pore water chemistry are major controls on preservation. In high productivity regions and oxic pelagic settings, a substantial part of the marine barite that originated in the water column and/or sediment–water interface is preserved (Paytan and Kastner, 1996). Most of the known sapropel records show Ba profiles suggesting no diagenetic overprinting (Fig. 9). Especially the most recent sapropel, S1, shows a Ba profile that delineates the original sapropel layer, despite organic matter oxidation and Fe and Mn diagenetic remobilization; the Ba enrichment in S1 sapropel is associated with well-preserved marine barite (Fig. 8) (Martinez-Ruiz et al., 2000). Similarly, preserved marine barite has also been observed in western Mediterranean records of high productivity intervals (Rodrigo-Gámiz et al., 2011). Even though diagenetic remobilization of Ba has been observed in certain sapropel layers (Van Os et al., 1994), the overall Ba productivity record in the Mediterranean is well preserved. The marine origin of barite in the sapropels is supported by its size, habit and the contemporaneous seawater sulfate isotopic composition (Paytan et al., 2004). In the Black Sea for instance, there is an intense overprint of the Ba signal due to methanogenesis (Henkel et al., 2012). However, no correlation of Ba profiles with those of trace elements that have been mobilized has been observed in the Mediterranean.
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