Naslov
Climate-driven changes among successive organic walled phytoplankton assemblages during the Toarcian Oceanic Anoxic Event

Autori
Baranyi, Viktoria ; Pálfy, József ; Riding, James B. ; Gorog, Agnes, Raucsik, Bela

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Abstract Book / - , 2014, 9-10

Skup
9th European Palaeobotany-Palynology Conference

Mjesto i datum
Padova, Italija, 26.08.2014. - 31.08.2014

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
T-OAE, palynology, dinoflagellates, Mecsek

Sažetak
Major palaeoenvironmental and palaeoceanographic changes occurred during the Late Pliensbachian– Early Toarcian and led to the perturbation of the global carbon cycle that culminated in the Toarcian Oceanic Anoxic Event (T-OAE) affecting both terrestrial and marine ecosystems. In this study we document the impact of these events on the marine microplankton assemblages based on palynological studies of the black shale-bearing Réka Valley section (Mecsek Mts, SW Hungary) and assess the coeval palaeoenvironmental changes by comparison of other European organic walled phytoplankton assemblages. Quantitative analyses using multivariate statistical methods (CA, NMDS, PCA) were carried out on palynomorphs and palynofacies in 33 samples, allowing to distinguish five successive assemblages in the Réka Valley section. The assemblages from the black shale differ significantly from those in the underlying and overlying strata. The underlying beds are dominated by different types of dinoflagellates, although diversity is low. The beds immediately below the black shale are characterized by peak abundance of the dinocyst Nannoceratopsis. The black shale totally lacks dinocysts, but is rich in small sphaerical palynomorphs (‘sphaeromorphs’) that are assigned to prasinophytes. A low diversity microplankton assemblage with rich sporomorph associations and high amount of pteridophyte spores characterize the beds above the black shale. The recorded changes of the palynomorph assemblages reflect the T-OAE and accompanying paleoenvironmental changes. The Early Toarcian global warming enhanced the hydrological cycle and increased the riverine input into the sedimentary basin of the Mecsek Mts., then located on the epicontinental margin of the Tethys Ocean. Subsequent reduction of salinity of surface waters and increased nutrient levels in the oceans led to blooms of eurihaline oppurtunistic species (e. g. Nannoceratopsis spp.). The low salinity surface waters prohibited the vertical exchange of dissolved oxygen and nutrients in the water column. The anoxic or dysoxic conditons at the bottom and dysoxia in the water column, together with changes of nutrient availability in the photic zone were tolerated only by prasinophytes. The T-OAE was followed by a prolonged phase of recolonisation with few dinoflagellates and locally high amount of terrestrial palynomorphs. Paleoenvironmental changes detected in the Réka Valley section are either global or regional, based on the scale of their impact. Regional changes, such as enhanced runoff, riverine input, lower salinity of surface waters and blooms of eurihaline Nannoceratopsis spp., occur at regional scale, in sections related to the epicontinental areas (e. g. Yorkshire, Wales, S Germany). However, the extinction of selected dinoflagellate species, a temporary dinoflagellate „blackout” and a prasinophyte peak are recognized in Tethyan areas (Central Italy) as well, indicating climate-driven global paleoenvironmental changes.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

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