GeoSed - Associazione Italiana per la Geologia del Sedimentario
Dipartimento di Scienze della Terra dell'Università di Siena
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Table of Contents


Vol. 9 - 2010

Vol. 8 - 2009

Vol. 7 - 2008
SP 1 - 2008

Vol. 6 - 2007
Vol. 5 - 2006
Vol. 4 - 2005
Vol. 3 - 2004
Vol. 2 - 2003
Vol. 1 - 2001-2002

Notes for Authors
(PDF - 80 kb)



GeoActa Special Publication 1 2008


Acquisto online

GeoActa
an international Journal of Earth Sciences



Mauro Aldinucci, Francesca Donia, Luca Maria Foresi, Roberto Mazzei, Federica Riforgiato, Fabio Sandrelli
Dipartimento di Scienze della Terra, Università di Siena, Via Laterina 8, 53100 Siena, Italy - aldinuccimau@unisi.it; fnc-donia@libero.it; foresi@unisi.it; mazzei@unisi.it; riforgiato@unisi.it; sandrelli@unisi.it
Giulio Bigazzi
Istituto Geoscienze e Georisorse- CNR, Via Moruzzi 1, 56100 Pisa, Italy - g.bigazzi@igg.cnr.it
Barbara Dall'Antonia, Simone Da Prato, Massimo D'Orazio, Giovanni Zanchetta
Dipartimento di Scienze della Terra, Università di Pisa, Via S. Maria 53, 56126, Pisa, Italy – barbarad@dst.unisi.it; dorazio@dst.unipi.it; zanchetta@dst.unipi.it

The upper Messinian post-evaporitic succession of Serredi Quarry (southern Tuscany, Italy): new stratigraphic data and geochronology of an ash layer


Volume 4, 2005, pages 159-164

PDF (1119 KB)
Abstract

An ash layer, about 1 cm thick, has been found during a reinvestigation of the upper Messinian-Zanclean succession exposed at Serredi Quarry (Fine Basin, Northern Apennines), one of the best known Neogene Tuscan sections.

The Serredi Quarry succession (about 175 m thick) has been subdivided into three intervals: the lower (18 m thick) and middle (132 m thick) ones are separated by an unconformity and are both referable to the Messinian post-evaporitic phase, whereas the upper interval (25 m thick) represents marl deposition following the Pliocene transgression. The lower interval consists of relatively deep-lacustrine, anoxic, thinly laminated mudstones with subordinate sands, whereas the middle one includes lacustrine mudstones (occasionally with pedogenic features) with sands, diagenetic gypsum-rich mudstones, limestones, gravels and selenite gypsum draped by gypsarenites. These lithofacies are typically arranged into marginal-lake, cyclical stacking patterns.

The ash layer is located in the lower interval. It is faintly laminated and composed of almost pure fine-grained glass shards and rare pumices. These characteristics suggest a primary deposition from a pyroclastic fallout. Chemical analyses were carried out on well preserved pumices and glass shards were used for fission-tracks dating, which provided an age of 5.35 ± 0.32 Ma. Nevertheless, its age can be further constrained by the fact that i) the ash layer is about 145 m below the Miocene-Pliocene boundary, and ii) the intervening deposits mainly consist of mudstones with occasional pedogenic features, which are likely to comprise sedimentary hiatuses. Accordingly, the ash layer probably emplaced in the older part of the determined age interval.

On the whole, the geochronology, geochemistry and the stratigraphic framework of the first ash layer found in the post-evaporitic deposits of Tuscany could represent valuable tools for regional stratigraphic studies on the Lago Mare phase and long-distance correlation.


Keywords: Lago Mare, Messinian, Stratigraphy, Ash layer, Geochronology.