Search

Nāri-calcrete is a calcareous formation common in the semiarid Mediterranean region of the Levant. The profile studied in Nazareth (Galilee) is 2.75 m thick and divided into the four conventional layers, i.e. a chalky bedrock, a powdery lower nāri, an indurated and platy upper nāri, and a laminar crust capping the profile. In this study, mercury intrusion porosimetry (MIP) is used to assess the genetic processes at work in the formation of nāri-calcrete. Based on the former work by Yaalon and Singer (1974) and MIP results, various parameters are proposed to describe the different layers: total porosity (N P ), trapped porosity (N T ), permeability (K), and strength (σ c ). These parameters are compared to each other for each layer, as well as with their respective calcium carbonate contents. An unexpected relationship shows that the more CaCO 3 is present, the more porous the layer of the nāri. Consequently, the lower nāri is interpreted as a weathering layer of the parent chalk, whereas the upper nāri, which is the most porous and the richest in CaCO 3 , results from in situ recrystallization. The upper nāri permeability precludes it from playing the role of a “plugged horizon” to explain the formation of the laminar crust. In conclusion, the nāri-calcrete in Nazareth questions the conventional model of calcrete genesis as its cementation is due to in situ redistribution of CaCO 3 rather than its translocation. These results strengthen Yaalon and Singer (1974)'s conclusions. [ABSTRACT FROM AUTHOR]

The abundant and diverse calcareous nannofossil assemblages found in the sediments of two ODP cores from the Western (Site 975B, South Balearic Basin) and Eastern (Site 969B, Mediterranean Ridge) Mediterranean Sea have been taken into account for the paleoenvironmental reconstruction of the surface water conditions during the first 490 kyrs immediately following the end of the Messinian Salinity Crisis, chronostratigraphically settled at 5.332 Ma. The areal distribution of the calcareous nannofossils is closely linked to their ecological and environmental affinities, mostly driven by temperature, salinity, nutrients or other chemical parameters of the water masses. Hence, taxa (or groups of taxa) showing well-known ecological behaviors were considered, and different environmental evolutions were recognized for the two sectors of the Mediterranean Basin during the early Zanclean (early Pliocene). Specifically, in the Western Mediterranean a switching from a warm and oligotrophic water environment, showing normal open-marine conditions, to a colder and eutrophic one, characterized by a decrease in salinity rates and the development of a more restricted environment, can be recorded. Conversely, in the Eastern Mediterranean the environmental setting immediately following the MSC is indicative of temperate waters and normal open-marine conditions, which evolves, in the younger layers, to a warmer environment characterized by high salinity rates and typical of a restricted marine context. The timing of the environmental transitions recognized at the two sites has been set through the Principal Component Analysis. Taxa and groups of taxa reflecting precise ecological affinities have been handled together and a transition interval have been defined between 5.20/5.15 Ma and 5.06/4.98 Ma, and between 5.10 Ma and 4.92 Ma in the Western and Eastern Mediterranean, respectively. [ABSTRACT FROM AUTHOR]