Flysch di Bergamo
Représentation et statut
- Couleur RGB
- R: 215 G: 215 B: 105
- Rang
- Formation lithostratigraphique
- Usage
- Ce terme est en usage.
- Status
- terme informel
Nomenclature
- Deutsch
- Bergamo-Flysch
- Français
- Flysch de Bergamo
- Italiano
- Flysch di Bergamo
- English
- Bergamo Flysch
- Origine du nom
-
Bergamo (Italia)
- Variantes historiques
-
obere bunte Mergel und Mergelkalke (Vonderschmitt 1938), Flysch di Bergamo (Gelati & Passeri 1967), Bergamo Flysch (Bichsel & Häring 1981, Bernoulli et al. 1981)
Description
- Épaisseur
- 400-1000 (Bichsel & Häring 1981)
Hiérarchie et succession
- Unité hiérarchiquement supérieure
- Unités hiérarchiquement subordonnées
- Unités sus-jacentes
- Unités sous-jacentes
Âge
- Âge au sommet
-
- Campanien tardif
- Âge à la base
-
- Santonien tardif
Géographie
- Extension géographique
- Lombardia centrale (Brianza, Bergamasco).
Paléogéographie et tectonique
-
- Südalpine Flysche
- Paléogéographie
- Bassin lombard
- Termes génériques
- Type de protolithe
-
- sédimentaire
- Conditions de formation
-
outer-fan sediments (Bichsel & Haering 1981)
Références
- Définition
- (1967) : Il Flysch di Bergamo, nuova formazione cretacica delle Prealpi Lombarde. Riv. It. Paleont. Strat. 73/3, 835–849
- Révision
-
(1981) :
Facies evolution of Late Cretaceous flysch in Lombardy (northern Italy). Eclogae geol. Helv. 74/2, 383–420
p.396: The term Bergamo Flysch was introduced by Gelati & Passeri (1967). The Bergamo Flysch is exposed mainly between the eastern Brianza and the river Oglio. with a thickness of about 1000 m in the Brianza and of at least 400 m in the Sarnico area. The lower boundary of the Bergamo Flysch is marked everywhere by the Sarnico Sandstone, or by the Piano di Sirone and is dated by Dicarinella assymetrica (Sigal), Globotruncana fornicata Plummer and Globotruncana lapparenti Bolli as Late Santonian. In the Bergamasco as well as in the central and eastern Brianza, the Bergamo Flysch is already succeeded in the Middle Campanian by marly Scaglia cinerea (Piano di Brenno) (Kleboth, in prep.).
In contrast to the siliciclastic sediments of the Sarnico Sandstone, the Bergamo Flysch contains abundant carbonate particles and displays a great variability in composition. The calcareous fraction consists mainly of carbonate fragments displaced from a (?)Late Cretaceous shallow-water area (echinoderms, red algae, bryozoa, miliolids, agglutinating foraminifera and pellet-like, strongly micritized red algal and shell fragments). The Bergamo Flysch is characterized by classical turbidites often with complete Bouma sequences, usually building up acyclic successions, but locally with huge negative cycles, up to 80 m thick.
The individual turbidite beds range from 20 to 200 cm in thickness representing mainly facies D1-2 and C1-2 and occasionally B2. Locally, also symmetrical cycles (thickening and coarsening/thinning and fining upward) up to 30 m thick occur. The sandstones show a grain size variation from fine sand up to well rounded broadly channelized conglomerates (max. diameter 5 cm). The sand/shale ratio varies from 1:2 at the base and the top to 5:1 in the middle part of a cycle. On the whole, these features are consistent with the definition of the outer-fan facies association.