Martino, Mariarosaria (2020) Stratigrafia integrata di successioni carbonatiche di mare basso del giurassico superiore–cretacico inferiore dell’appennino meridionale. [Tesi di dottorato]


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Item Type: Tesi di dottorato
Resource language: Italiano
Title: Stratigrafia integrata di successioni carbonatiche di mare basso del giurassico superiore–cretacico inferiore dell’appennino meridionale
Date: 26 October 2020
Number of Pages: 144
Institution: Università degli Studi di Napoli Federico II
Department: Scienze della Terra, dell'Ambiente e delle Risorse
Dottorato: Scienze della Terra, dell'ambiente e delle risorse
Ciclo di dottorato: 32
Coordinatore del Corso di dottorato:
Barattolo, FilippoUNSPECIFIED
Date: 26 October 2020
Number of Pages: 144
Keywords: Piattaforma carbonatica; Biostratigrafia; Stratigrafia sequenziale; Ciclostratigrafia
Settori scientifico-disciplinari del MIUR: Area 04 - Scienze della terra > GEO/01 - Paleontologia e paleoecologia
Area 04 - Scienze della terra > GEO/02 - Geologia stratigrafica e sedimentologica
Date Deposited: 02 Nov 2020 09:08
Last Modified: 28 Oct 2021 12:40

Collection description

Shallow-water carbonate records are often characterised by low stratigraphic resolution and poor chronostratigraphic calibration despite abundant and diversified fossil content. In particular, the Kimmeridgian – Tithonian boundary has been affected by the increase in production of pelagic carbonates linked to the rise of the eustatic curve related to the opening of the South Atlantic Ocean. Later, during the Jurassic – Cretaceous transition, the formation of epicontinental areas with restricted sea water circulation caused by the fall of sea level, promoted the evolution of endemic species. Consequently, the discovery of biostratigraphic markers still remain a task to carry on at the Jurassic-Cretaceous transition which is characterised by only low‐amplitude changes in the C isotope curve. The missing of C isotope excursions and spikes in the record of marine carbonates reveal a further difficulty to obtain accurate stratigraphic markers during this time. The early Cretaceous records, instead, are punctuated by several carbonate production crises and perturbations of the global carbon cycle (Weissert, Faraoni and Selli events). Unlike coeval northern Tethyan carbonate platforms, the Apennine platform did not drown during this time interval but responded to palaeoenvironmental and palaeoceanographic perturbations by biofacies changes that are here studied starting from the late Valanginian to the late Barremian. Possible bioevents are investigated in this PhD thesis by an integrated stratigraphy to contribute to definition and duration of the stages around the Jurassic-Cretaceous boundary and of the early Cretaceous. Multidisciplinary studies based on sedimentology, biostratigraphy, cyclo-sequence stratigraphy of shallow-water carbonates show that the bio-sedimentary system is controlled by internal and/or external processes. Understanding the role of these processes is therefore crucial to analyse how platform ecosystems respond to global environmental perturbations as well as is fundamental to perform a solid anchorage of the biostratigraphic data to the global events and geochronology. In this dissertation, two isolated carbonate platform sections in the southern Apennines (Italy) have been analysed: the Petina section (Monte Forloso, Alburni Mountain) and the San Lorenzello section (Monte Monaco di Gioia, Matese Mountain). Fossil assemblages, combined with lithofacies characteristics, are used to reconstruct the paleoenvironmental history of the sections, which represent inner sectors of a wide and shallow carbonate platform influenced by waves, with a high-energy zone of migrating sandy shoals separating a more open from a more restricted lagoonal settings. Here sea-level oscillations induced frequent and cyclic emersions of the platform, testified by karstification and pedogenesis superimposed on marine carbonates. A hierarchy of shallowing-upward cycles (elementary cycles, bundles and superbundles), linked to Earth’s orbital oscillations, has been individuated. Numerous green algae and foraminifera bioevents have been identified and several biozones have been defined (four for Petina and six for San Lorenzello). A considerable refinement of the biostratigraphy is carried out, so that the Petina section is attributed to Kimmeridgian p.p. – Berriasian p.p. while the San Lorenzello section to the Valanginian p.p. – Barremian p.p. In particular the best anchoring to the southern Tethys biozonal schemes has been performed also by the carbon-isotope correlation of the San Lorezello section to the other Tethys platforms and basins, producing a better agreement between the position of the Valanginian-Hauterivian boundary indicated by biostratigraphy and that indicated by C-isotopes. Superbundles and superbundle groups (lower-frequency cycles, T/RFTs) have been interpreted in terms of depositional sequences. Most of the Trangressive/Regressive Facies Trends (T/RFTs) boundaries have been correlated with the “global” Sequence Boundaries and to the Late Jurassic–Early Cretaceous eustatic curve of Haq (2014; 2018). Based on these correlations, the most T/RFTS disconformities would appear controlled by eustatism. Finally, the chronostratigraphic calibration of the biostratigraphic events, performed by correlation to the eustatic curve, shows a correlation between benthic foraminiferal and calcareous algae turnover phases and eustatic events. The Kimmeridgian–Berriasian time is characterised by few bioevents, but it is evident that the latest Jurassic time shows the occurrence of relative more species at least until to the base of the Tithonian, according to the long-term sea level rise, while the disappearance events are concentrated during the sea level fall characterising the Tithonian-Berrasian interval. The late Valanginian-Hauterivian time appear to be characterised by a relevant neritic biota recovery following the global crisis (Weissert event). A major renewal for dasycladales more than for foraminifera would coincide with a return to warmer temperatures after the late Valanginian cooler episode. On the other hand, the gradual disappearance of species, mostly concerning the dasycladaleans, are mainly concentrated in the Barremian long-term sea level fall. This could testify the progressive and slow decay of platform environmental conditions preluding the carbonate production crisis documented immediately before and during the OAE1a.


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