A possible deep-water non-evaporitic unit equivalent of the Messinian Lower Evaporites has been recognised in the NorthernApennine foredeep. This unit, whose existence is implicitly admitted in the two-step model of the Mediterranean Messinian salinitycrisis is documented here for the first time; it occurs throughout the Apennine foredeep basin below a thick horizon of resedimentedgypsum deposits, usually ascribed to the Lower Evaporites. Actually, the Lower Evaporites of the Apennine foredeep basin includeboth shallow-water, in situ precipitated facies and deep-water, resedimented facies deposited in distinct depocenters. The usuallyenvisaged coeval nature of the two deposits has been recently challenged in several works based on a) physical–stratigraphicconsiderations about the downbasin correlation of the Messinian erosional surface cutting on top the in situ evaporites with thesharp base of the resedimented evaporites unit and b) the common occurrence of a barren unit below the resedimented evaporiteswhich has no obvious equivalents in pre-evaporitic successions underlying the in situ precipitated evaporites.In this work a multidisciplinary study has been carried out on a 140 m-thick composite section (Fanantello section) to definitelyassess the age and palaeoenvironmental characteristics of the unit underlying the resedimented gypsum deposits. The topmost partof the section comprises a 60 m-thick succession of barren euxinic shales falling entirely within a reversed polarity chron andcharacterised by a) the complete disappearance of Foraminifera, b) the occurrence of high salinity tolerant thecosomatouspteropods (Creseis sp.) c) the abundance peaks of the calcareous nannofossil Sphenolithus abies (interpreted as related to highlystressed likely hyperhaline conditions), d) the appearance of hyperhaline and/or stratified water molecular indicators(gammacerane, b0.2 pristane/phytane ratio, b1 n-alkanes odd–even predominance).Based on a multidisciplinary integrated stratigraphic approach this barren interval, is here proposed to be a deeper-water timeequivalentof the in situ primary Lower Evaporites, thus
|Data di pubblicazione:||2007|
|Titolo:||The deep-water counterpart of the Messinian Lower Evaporites in the Apennine foredeep: the Fanantello core (Northern Apennines, Italy).|
|Autori:||Manzi, V; Roveri, M; Gennari, R; Bertini, A; Biffi, U; Giunta, S; Iaccarino, S; Lanci, L; Lugli, Stefano; Negri, A; Riva, A; Rossi, M; Taviani, M.|
|Digital Object Identifier (DOI):||10.1016/j.palaeo.2007.04.012|
|Appare nelle tipologie:||Articolo su rivista|
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