The Flysch is a particular turbiditic succession that generally is considered as a synorogenic marine deposit in passive margins. Generally, it is composed by an alternation of sandstones and mudstones/siltstones in sup-parallel strata that can be more or lesser rich in carbonate material and fossils. These could have different thickness that strongly depend on the sediment supply and the stage of sedimentation. The Flysch Basins located in the North Eastern Part of the Adria Plate are typical expression of this kind of sedimentary body being supposed as derived during the Dinaric orogenic phase. The basin investigated are the Julian (JB), Brkini (BK), Istrian (IB) and North Dalmatian Flysch Basins (ZB) and show an age between the Maastrichtian and the Lower Eocene. All the basins show elongated form with NW-SE direction being almost parallel to the Dinarides. In the past it has been suggested that the basins were filled in sequence, starting from the oldest one (JB) and following with BK, IB and finally ZB. This theory suggested that the new basin will open only when the previous one was filled. The Julian and North Dalmatian Basins show a complete and well documented stratigraphy, while Brkini and Istrian ones are still incomplete and often studied separating their member, due to the extreme tilting, faulting and overthrusting they have suffered during the Dinaric Phase. In particular, IB is commonly divided in three part, Trieste, Pazin and Kvarner Islands basins. In this work, it will be considered as one since all the three are coeval and their structures seem to be similar suggesting a common evolution. In the past, several authors suggested that the main carbonate fraction supply could derive from the disgregation of the Adriatic Carbonatic Platform located southwest regarding the basins, while the primary siliciclastic sources were located in the Dinarides. This is also suggested by recent provenance studies focused on detrital Cr-spinel, garnet, clinopyroxene and amphibole, which place the main source of these minerals in both the Inner and External Dinarides. In agreement with this thesis, the distribution of the Cr-spinels ratio between peridotitic and magmatic crystals in the basins follows the changing of the ophiolites affinity that outcrops in the suggested source areas. Several authors stated that paleocurrents have been also present flowing from northwest to south east, perpendicular to the suggested main supply flows and parallel to the elongation of the basin bodies. These are interpreted as second suppliers of siliciclastic sediments that could derive from the Alpine Area. Furthermore, the currents could have connected the basins creating a recycle of the old sediments along all the stratigraphy or just for brief moments testified by sudden changes in mineralogy/granulometry/chemistry. In this work trace elements of garnet, rutile and zircon together with the U-Pb geochronology of the zircon are used to locate the provenance area of the siliciclastic fraction of the four flysch basins and to verify possible connection among them. Furthermore, the data will be also useful for better understanding the geodynamic Cretacic-Eocenic evolution of the region.

Il flysch è un particolare tipo di successione torbiditica che è generalmente considerata come un deposito marino sinorogenico di margini passivi. Generalmente è formato da un'alternanza di arenarie e marne/siltiti in strati sub-paralleli che possono essere più o meno ricchi di materiale carbonatico e fossili. Gli strati possono avere spessori variabili che dipendono fortemente dal tipo di sedimento e dallo stadio di sedimentazione. I bacini flyshoidi situati nella parte nordorientale della Placca Adria sono una tipica espressione di questo genere di corpi sedimentari presupponendo che si siano formati durante la fase orogenica Dinarica. I bacini studiati si compongono del Bacino Giulio (JB), Bacino Birchini (BK), Bacino Istriano (IB) e il Bacino Dalmato Settentrionale (ZB), mostrando un'età che varia da Fine Cretacico (Maastrichtiano) fino alla fine dell'Eocene (Isola di Pag, IB). Tutti i bacini mostrano una forma allungata NW-SE e sono paralleli alla catena Dinarica. In passato è stato suggerito che i bacini si siano riempiti in sequenza, dal più vecchio (JB), seguito da BK fino al più giovane (IB), mentre la dinamica di ZB non era stata presa in considerazione. Questa teoria suggerisce che il bacino più "nuovo" si riempisse solo quando quello precedente si fosse riempito completamente. Il bacino Giulio e quello Dalmato hanno una sequenza stratigrafica completa e ben documentata, mentre i bacini Birchini e Istriano risultano ancora mancanti da questo punto di vista, dato che spesso sono stati studiati membro per membro a causa degli effetti orogenici che li hanno smembrati e deformati. In particolare IB è comunemente diviso in tre parti, il Bacino Triestino, il Bacino di Pazin e quello delle Isole del Quarnero. In questo lavoro tratteremo tutti e tre i bacini come fossero uno, data la stessa età di formazione e le strutture tettoniche simili che suggeriscono un'evoluzione comune. In passato, numerosi autori hanno suggerito che la frazione carbonatica sia stata prevalentemente fornita dalla disgregazione della Piattaforma Carbonatica Adriatica posta direttamente a Sud-Est rispetto ai bacini, mentre la sorgente primaria della frazione silicoclastica è stata localizzata all’interno delle Dinaridi. Questo è stato suggerito anche da recenti studi di provenienza improntati su Cr-spinello, granati, clinopirosseni e anfiboli detritici, che posizionano la loro sorgente nelle Dinaridi Interne ed Esterne. In accordo con questa ipotesi, il rapporto tra Cr-Spinelli magmatici e peridotitici segue il cambiamento litologico delle ofioliti che affiorano vicino le ipotetiche aree di sorgenza. Numerosi autori hanno suggerito che le paleocorrenti durante il periodo di deposizione avessero una direzione NW-SE, perpendicolare alla direzione principale di derivazione del materiale silicoclastico, e parallelo alla direzione della catena Dinarica. Queste sono state interpretate come sorgenti secondarie di materiale silicoclastico che potrebbe derivare anche dall’area Alpina. Inoltre, queste correnti potrebbero aver connesso i bacini creando un riciclo di sedimento lungo tutta la stratigrafia o per un breve periodo. L’evidenza potrebbe essere suggerita da un netto cambio di mineralogia/granulometria/chimica. In questo lavoro di tesi, sono stati analizzati gli elementi in traccia di granati, rutili e zirconi assieme alla geocronologia U/Pb di questi ultimi. I dati verranno usati per localizzare la zona di provenienza della frazione silicoclastica dei quattro bacini e verificare un’eventuale connessione tra loro.

Zircon dating and trace element content of transparent heavy minerals in sandstones from the NE Alps and Outer Dinarides flysch basins / Velicogna, Matteo. - (2020 Mar 20).

Zircon dating and trace element content of transparent heavy minerals in sandstones from the NE Alps and Outer Dinarides flysch basins

VELICOGNA, MATTEO
2020-03-20

Abstract

The Flysch is a particular turbiditic succession that generally is considered as a synorogenic marine deposit in passive margins. Generally, it is composed by an alternation of sandstones and mudstones/siltstones in sup-parallel strata that can be more or lesser rich in carbonate material and fossils. These could have different thickness that strongly depend on the sediment supply and the stage of sedimentation. The Flysch Basins located in the North Eastern Part of the Adria Plate are typical expression of this kind of sedimentary body being supposed as derived during the Dinaric orogenic phase. The basin investigated are the Julian (JB), Brkini (BK), Istrian (IB) and North Dalmatian Flysch Basins (ZB) and show an age between the Maastrichtian and the Lower Eocene. All the basins show elongated form with NW-SE direction being almost parallel to the Dinarides. In the past it has been suggested that the basins were filled in sequence, starting from the oldest one (JB) and following with BK, IB and finally ZB. This theory suggested that the new basin will open only when the previous one was filled. The Julian and North Dalmatian Basins show a complete and well documented stratigraphy, while Brkini and Istrian ones are still incomplete and often studied separating their member, due to the extreme tilting, faulting and overthrusting they have suffered during the Dinaric Phase. In particular, IB is commonly divided in three part, Trieste, Pazin and Kvarner Islands basins. In this work, it will be considered as one since all the three are coeval and their structures seem to be similar suggesting a common evolution. In the past, several authors suggested that the main carbonate fraction supply could derive from the disgregation of the Adriatic Carbonatic Platform located southwest regarding the basins, while the primary siliciclastic sources were located in the Dinarides. This is also suggested by recent provenance studies focused on detrital Cr-spinel, garnet, clinopyroxene and amphibole, which place the main source of these minerals in both the Inner and External Dinarides. In agreement with this thesis, the distribution of the Cr-spinels ratio between peridotitic and magmatic crystals in the basins follows the changing of the ophiolites affinity that outcrops in the suggested source areas. Several authors stated that paleocurrents have been also present flowing from northwest to south east, perpendicular to the suggested main supply flows and parallel to the elongation of the basin bodies. These are interpreted as second suppliers of siliciclastic sediments that could derive from the Alpine Area. Furthermore, the currents could have connected the basins creating a recycle of the old sediments along all the stratigraphy or just for brief moments testified by sudden changes in mineralogy/granulometry/chemistry. In this work trace elements of garnet, rutile and zircon together with the U-Pb geochronology of the zircon are used to locate the provenance area of the siliciclastic fraction of the four flysch basins and to verify possible connection among them. Furthermore, the data will be also useful for better understanding the geodynamic Cretacic-Eocenic evolution of the region.
20-mar-2020
LENAZ, DAVIDE
PRINCIVALLE, FRANCESCO
32
2018/2019
Settore GEO/06 - Mineralogia
Università degli Studi di Trieste
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11368/2961202
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