Fossil record of holococcoliths and selected hetero-holococcolith associations from the Mediterranean (Holocene–late Pleistocene): Evaluation of carbonate diagenesis and palaeoecological–palaeocenographic implications

Abstract

The Holocene-late Pleistocene distribution of holococcoliths, is quantified by light microscopy from cores from the Western Mediterranean, the Aegean Sea and eight eastern Mediterranean cores recovering sapropel S1. The diversity of fossil holococcoliths is much lower than is seen in the plankton, indicating selective preservation. However the holococcolith phases of Syracosphaera pulchra and Helicosphaera carteri are abundantly preserved allowing a comparison of fossil records of heterococcolith and holococcolith phases of these species.In shallow cores a primary palaeocological signal appears to be preserved, suggesting that under suitable circumstances it is possible to use holococcoliths in palaeoceanography. The common occurrence of holococcoliths in the sapropels from these cores suggests low surface-water productivity, supporting previous inferences that productivity enhancement during sapropel deposition was confined to the deep-chlorophyll maximum.In deeper cores there is dramatic decrease in abundance of S. pulchra holococcoliths within sapropel sediments. From comparison of shallow and deep cores and from Emiliania huxleyi preservation data we conclude that this is a preservation signal. Evidently the calyptroliths produced by S. pulchra have a lower preservation potential than the syracoliths produced by H. carteri, we interpret this as a product of their more open structure. D

Diagenetic Mg-rich calcite in Mediterranean sediments: Quantification and impact on foraminiferal Mg/Ca thermometry

“…Overgrowths were observed by Crudeli et al (2004Crudeli et al ( , 2006, while studying nanofossils (Emiliania huxleyi). Crudeli et al (2004) suggested that fluctuations in the abundance of nannofossil morphotypes in the Eastern Mediterranean do not necessarily reflect environmental conditions in surface waters (temperature, fertility, etc.…”

Comparing Living and Holocene Coccolithophore Assemblages in the Aegean Marine Environments

“…Helicosphaera spp. is known to preferentially high productivity waters in the middle photic zone Crudeli et al, 2006). In this study, the genus Helicosphaera is represented mainly by H. carteri, a species with preference in warm waters (Brand, 1994;Baumann et al, 2005) and moderately elevated nutrient levels (Findlay and Giraudeau, 2000;Andruleit and Rogalla, 2002;Ziveri et al, 2004).…”

Mediterranean coccolith ecobiostratigraphy since the penultimate Glacial (the last 145,000years) and ecobioevent traceability

“…The high preservation potentiality of this species has already been reported in late Quaternary Mediterranean sediments, where it occurs with percentage values up to 25-30% . However, we note that Crudeli et al (2006) ruled out from their quantitative counts specimens of E. huxleyi, gephyrocapsids and F. profunda. Thus the abundance reported in the present study for S. pulchra HOL oblonga may even be higher than in the eastern Mediterranean cores.…”

“…A further strong evidence of decreased productivity during MIS 3 and MIS 2 cold spells is the correlation between Miscellaneous taxa and holococcoliths (S. pulchra HOL oblonga) (Figs 4 and 5), that are typical of warm and oligotrophic water and in fact they are especially abundant in the eastern Mediterranean Sea (e.g., Kleijne, 1991;Knappertsbusch, 1993;Winter et al, 1994;Crudeli et al, 2006;Malinverno et al, 2009). The high preservation potentiality of this species has already been reported in late Quaternary Mediterranean sediments, where it occurs with percentage values up to 25-30% .…”