Megabed di Missaglia
Représentation et statut
- Couleur CMYK
- (0%,0%,0%,100%)
- Rang
- Banc lithostratigraphique
- Usage
- Ce terme est en usage.
- Status
- terme local (informel)
Nomenclature
- Deutsch
- Missaglia-Megabed
- Français
- Mégabed de Missaglia
- Italiano
- Megabed di Missaglia
- English
- Missaglia Megabed
- Origine du nom
- Missaglia (Italia)
- Variantes historiques
- Missaglia Megabed = Megabed di Missaglia (Bernoulli et al. 1981)
Description
- Épaisseur
- 25-30 m
Paléogéographie et tectonique
- Paléogéographie
- Bassin lombard
- Termes génériques
Références
- Définition
-
(1981) :
The Missaglia megabed, a catastrophic deposit in the Upper Cretaceous Bergamo Flysch, northern Italy. Eclogae geol. Helv. 74/2, 421–442
p.421: The thickest of these intervals, the Missaglia Megabed. is intercalated into the Upper Santonian-Campanian Bergamo Flysch and can be traced over at least 12. presumably over 25 km. It overlies 6 m of pebbly mudstone with plastically deformed slabs of basinal marls of Aptian to Middle Cenomanian age, of turbiditic flysch sandstones and of cobbles and boulders of Liassic shallow-water and Cretaceous pelagic limestones set in a fluidally deformed silty matrix. The megabed itself consists of a 1 m thick basal conglomerate grading upwards into 25-30 m of coarse-tail graded calcarenite. calcisiltite and marlstone. In contrast to the terrigenous turbidites of the Lombardian Flysch, the Missaglia Megabed mainly contains along its base fragments of Upper Cretaceous pelagic limestones, of Jurassic shallow-water and pelagic limestones the same as in the sequence of the Trento Plateau, and. in the arenitic-pelitic interval, size-sorted tests of planktic foraminifera of Albian to Early Campanian age. quartz grains, bioclastic silt and redeposited coccolith ooze. The source area of the megabed is thus thought to have been a submerged high, possibly the Trento Plateau to the east and the emplacement of the catastrophic deposit is seen in connection with synsedimentary tectonics along the boundary faults which confined the Lombardian Basin during the Late Cretaceous. The sediment volume displaced by the Missaglia event must be larger than 4 km3 and probably exceeds 20 km3.