The Messinian Vena del Gesso Basin in the Northern Apennines is filled by very thick (up to 35 m) beds of coarse crystalline gypsum (selenite) associated with thinner carbonate and shaly (euxinic) intercalations. The conventional Usiglio model of salt fractionation does not apply to this evaporitic sequence for the following reasons: carbonate which underlies gypsum is not evaporitic but algal in origin; most gypsum did not precipitate from surface brines but at and below a sediment‐water interface occupied by algal mats; a significant portion (10–80%) of gypsum beds is composed of redeposited selenite which was removed from the margins and transported toward the centre of the basin by slope‐controlled currents and gravity flows (debris flows).
We call this process cannibalistic because of its intraformational character (connected with evaporative fall of water level) and volumetric importance.
A recurrent vertical pattern of six main facies (euxinic to gypsum fanglo‐merates) is interpreted as a bathymetric, regressive cycle controlled by both sedi‐mentological and tectonic‐eustatic factors. The inferred environmental setting is a residual turbidite trough (Marnoso‐arenacea) evolving abruptly toward lagoonal conditions and filled up to sea level by evaporitic and mechanical (mostly fluvial) processes. Repeated inundations of restricted‐marine water started the depositional cycle thirteen or fourteen times.
A detailed quantitative calcareous nannofossil analysis has been performed on 138 samples from the astronomically dated Monte del Casino section with the aim to identify and precisely date the most important calcareous nannofossil events across the Tortonian=Messinian boundary in the Mediterranean, and to unravel paleoceanographic conditions at times of sapropel formation during the Late Miocene. From the biostratigraphic perspective, the genus Amaurolithus provides three successive first occurrences (FOs): A. primus, A. cf. amplificus and A. delicatus, dated at 7.446, 7.434 and 7.226 Ma, respectively. Other bioevents include the base and top of the 'small reticulofenestrids' Acme, dated at 7.644 and 6.697 Ma, and the FO, FCO and LO of R. rotaria, dated at 7.405, 7.226 and 6.771 Ma. These events appear to be useful in improving biostratigraphic resolution in the Tortonian-Messinian boundary interval, at least for the Mediterranean. Quantitative analysis revealed changes in the calcareous nannofossil assemblage associated with the sapropels. The observed fluctuations suggest a single mechanism for sapropel formation in the Mediterranean during the late Neogene. Sapropels are characterized by a decrease in the total number of coccoliths, interpreted mainly as a reduction in calcareous nannofossil production due to increased siliceous plankton production during spring blooms; and an increase in reworked specimens, interpreted to reflect enhanced continental input via river run-off. An increase in abundance of the genus Rhabdosphaera can be explained by opportunistic behavior at the end of the spring bloom when nutrient levels start to become impoverished. As far as sea surface water temperature indicators are concerned, warm water D. pentaradiatus shows positive fluctuations in sapropels while cooler water D. intercalaris and C. pelagicus show negative fluctuations.
We describe a new palaeobotanical site at Bubano quarry on the easternmost Po plain, northern Italy. Pollen and macrofossils from river and marsh sediments demonstrate the occurrence of Picea in a Pinus sylvestris forest growing in a radius of some tens of kilometres south of the sedimentation place, at the beginning of the Lateglacial interstadial. The Late-glacial and Holocene history of Picea in the northern Apennines is reconstructed on the basis of the palaeobotanical record. The sharp climatic continentality increase eastwards across the northern Apennines from the Tyrrhenian to the Adriatic coast is considered significant for the survival of Picea during the Late-glacial. The most critical phase of survival is related to the moisture changes and consequent Abies competition associated with the last glacial-interglacial transition and the early Holocene. The residual spruce populations expanded during the middle Holocene. The history of Picea in the northern Apennines is a case of ineffective interglacial spread of tree populations from pre-existing stands of LGM (Last Glacial Maximum) and Late-glacial age.
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