Flysch di Pontida
Back to Formazione (del Piano) di SironeRepresentation and status
- Color RGB
- R: 190 G: 190 B: 110
- Rank
- lithostratigraphic Formation
- Validity
- Unit is not in Use
- Status
- informal term
Nomenclature
- Deutsch
- Pontida-Flysch
- Français
- Flysch de Pontida
- Italiano
- Flysch di Pontida
- English
- Pontida Flysch
- Origin of the Name
-
Pontida (Italia)
- Historical Variants
-
Flysch grigio (Vento 1951), Formazione di Pontida (De Rosa & Rizzini 1967, Bichsel & Häring 1981, Bersezio et al. 1990), Pontida Formation (Bernoulli et al. 1981)
Description
- Thickness
- Ca. 300 m.; max. 450 m (Bichsel & Häring 1981)
Hierarchy and sequence
- Superordinate unit
- Units at roof
- Units at floor
Age
- Age at top
-
- Late Coniacian
- Age at base
-
- Early Turonian
Geography
- Geographical extent
- Lombardia centrale (Brianza).
Palaenography and tectonic
-
- Südalpine Flysche
- Tectonic unit (resp. main category)
- Kind of protolith
-
- sedimentary
- Conditions of formation
-
Deposizione abissala / depositi di piana di bacino (Bichsel & Haering 1981)
References
- Definition
-
(1981) :
Facies evolution of Late Cretaceous flysch in Lombardy (northern Italy). Eclogae geol. Helv. 74/2, 383–420
p.391: The term Pontida Formation was first used by de Rosa & Rizzini (1967) for the succession of turbiditic sandstones and marls in the Pontida area (section 31, p. 406; Fig. 1, G). The expression "Flysch grigio", introduced by Venzo (1951) is a synonym.
The individual turbidites, mainly Tb-e and Tc-e Bouma sequences, ranging from 5 to 100 cm in thickness, have a wide lateral continuity and are bound by even and parallel surfaces. The sandstone/shale ratio is 1:3 (facies D). The turbidites are acyclically arranged; the Pontida Formation displays the diagnostic features of a basin-plain facies association (Fig. 3). The sandstones are grey, brown weathering, of
fine to medium grain. Three main lithologie types can be distinguished: Lithic arenites are composed of siliciclastic fragments such as quartz, crystalline rocks, chert, feldspar and mica. Bioclastic arenites are mainly composed of detrital carbonate particles, such as fragments of echinoderms, molluscs (Inoceramus and rudists), microfossils and lithoclasts derived from the Mesozoic formations of the southern Alps. Foraminiferal arenites: composed mainly of planktonic foraminifera (50-80%) together with silt-sized quartz grains and mica.