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Accueil du site → Doctorat → Allemagne → 2021 → Climate forcing on water column and sedimentary environments of an ancient semi-enclosed basin : insights from the late Miocene (Messinian) Mediterranean Basin

Universität Hamburg (2021)

Climate forcing on water column and sedimentary environments of an ancient semi-enclosed basin : insights from the late Miocene (Messinian) Mediterranean Basin

Sabino, Mathia

Titre : Climate forcing on water column and sedimentary environments of an ancient semi-enclosed basin : insights from the late Miocene (Messinian) Mediterranean Basin

Auteur : Sabino, Mathia

Université de soutenance : Universität Hamburg

Grade : DOKTORGRADES DER NATURWISSENSCHAFTEN 2021

Résumé partiel
The late Miocene (11.6 to 5.3 Ma) was characterized by a global trend of cooling and aridification. In such a scenario, the Mediterranean Basin was experiencing increasing tectonic restriction and climate fluctuations driven by changes in orbital parameters of the Earth (mostly precession). The concurrence of these factors ultimately led to the most dramatic paleoceanographic event in the history of the basin, the Messinian salinity crisis (MSC ; 5.97–5.33 Ma). Although this event is known since more than 50 years, a detailed understanding of the environmental conditions established at the onset and during the MSC has not been reached yet. This is due to the inaccessibility of sediments deposited in the Messinian Mediterranean depocenters (> 1000 m paleodepth), the lack of modern analogs, and the scarcity of body fossils in the stratigraphic record. A so far rarely explored possibility to solve the riddle of the enigmatic environmental change accompanying the MSC onset is the study of sediments deposited at intermediate paleobathymetric depths (200–1000 m). In fact, these sediments represent the link to the still inaccessible early MSC sediments deposited in the depocenters of the late Miocene Mediterranean. The aim of this thesis is to widen our knowledge on the paleoenvironmental conditions established at the MSC onset. Shale/marl couplets from intermediate paleobathymetric settings of the northernmost late Miocene Mediterranean sub-basin, the Piedmont Basin (NW Italy), were investigated. A multiproxy approach was applied, merging organic geochemical proxies (lipid biomarkers ; compound-specific hydrogen (d2H) and carbon (d13C) stable isotopes) with inorganic geochemical proxies (Al, Si, Ti, and Zr ; bulk-rock carbon (d13C) and oxygen (d18O) stable isotopes). Stratigraphic and petrographic studies complemented the investigations. One of the outcomes of this thesis is that prior to the onset of the MSC moister conditions prevailed at precession minima, resulting in enhanced riverine runoff. Such conditions favored phytoplankton blooms in the upper water column and led to a strong thermohaline stratification. Oxygen-depleted and sulfidic conditions developed at the seafloor and in the water column, occasionally extending into the photic zone, promoting deposition of organic-rich shales. Conversely, marls deposited at precession maxima when the climate was drier.

Mots clés  : Messinian salinity crisis ; Organic geochemistry ; Lipid biomarkers ; Compound-specific stable isotopes

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Page publiée le 19 novembre 2021