81 research outputs found
Polyphase folding at upper structural levels in the Borbera valley (Northern Apennines, Italy): implications for the tectonic evolution of the linkage area between Alps and Apennines
The Borbera Valley (northwestern Italy) is located in a complex geological area where the linkage between Alps and Apennines occurs. In this area the Antola Unit (Late Cretaceous–Palaeocene) is unconformably overlain by the Upper Eocene–Miocene succession of the Tertiary Piedmont Basin. The structural analysis indicates the occurrence of a folding phase of Late Oligocene–Early Miocene age, characterised by recumbent F2 folds. These folds are superposed onto D1 structures related to an early folding phase of Middle Eocene, affecting only the Antola Unit. The occurrence of map-scale D2 folding phase structures that affect the Tertiary Piedmont Basin succession suggests that the linkage area between Alps and Apennines was reactivated during the Late Oligocene–Early Miocene
Considerazioni preliminari sulla paleogeografia del dominio toscano interno tra il Trias superiore ed il Miocene medio
Statistical analysis of gravel deposits: a powerfull tool for reconstructing changes in landscape evolution
rnformat1on about the geomorph1c-sedimentary landscape evolution in response
to tecton1cs an d/or relat1ve sea-level changes. The Lower Pleistocene deposits
croppmg aut 1n the Lower Cec1na Valley are a useful means far reconstructing
past changes m the supply area because they represent an ancient coastal
zone. When marine sediments are reworked and conglomeratic layers are
d1scont1nuous the clast litholog1cal analys1s becomes an invaluable tool to
determine stratigraphic correlations between outcrops. Grave l deposits are
part1cular powerfully far th1s arm because they reflect the lithologies cropping
out m the anc1ent dramage area s. Three gravel layers have bee n recognized in
the study area, belong1ng to three d1fferent Allostratigraphic Units (AUs) and
clearly d1splaced by tectonics. Two statistica l analyses of gravel clasts,
mtegrated by facres and paleontolagical data, from the Lower Pleistocene
deposits in the Lower Cecina Valley {Tuscany, Italy) have been combined to
unravel changes in the palaeo-drainage system. Data from sixteen outcrops
were collected and 6400 clasts described. Although facies analysis,
mrcrofmacro-palaeontology and petrographic characteristics of the gravel
depos1ts have h1ghllghted the presence of three Aus, clast lithology difference
has resulted to be the mai n discriminator in their identificati an. Cluster and
principal component analyses of the 6400 clasts have permitted to i m prove the
stratrgraphy of the Lower Plerstocene depos1ts and to constrain the re-routing
ofthe_lower palaeo-Cecina River from a supposedly SE-NW to the present E-W
drrect1on. The dramage systems in zone characterized by the presence of
half-grabens with intrabasin transfer zones tends to intersect the main tectonic
lineaments in arder to cut the footwall and pass to the hanging-wall basins. By
contrast,_ when transfer zones are not present the drainage system tends to
arrange 1tself parai lei to the depression of the half-graben and remains in the
hanging-wall, like the major river of the Tuscany. The absence of deltaic
depos1ts related to the dra1nage system of the paleo-Cecina River in the
outsk1rt of the study area confrrm that during the beginning of the Early
Pleistocene the river flowed northward. The diversion of the paleo-Cecina River
took piace dunng the Early Pleistocene when a strike-slip fault started to create
the Lower Cecina Valley
Note Illustrative del Foglio 217 Neviano degli Arduini della Carta Geologica d'Italia a scala 1: 50.000
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