Size and abundance variations of Schizosphaerella across the Toarcian Oceanic Anoxic Event in the Sogno Core (Lombardy Basin, Southern Alps)
Articolo
Data di Pubblicazione:
2022
Citazione:
Size and abundance variations of Schizosphaerella across the Toarcian Oceanic Anoxic Event in the Sogno Core (Lombardy Basin, Southern Alps) / G. Faucher, S. Visentin, G. Gambacorta, E. Erba. - In: PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY. - ISSN 0031-0182. - 595:(2022), pp. 110969.1-110969.15. [10.1016/j.palaeo.2022.110969]
Abstract:
Abundance and size variations of nannofossil Schizosphaerella punctulata were quantified in the uppermost
Pliensbachian–Lower Toarcian succession recovered with the Sogno Core (Lombardy Basin, Northern Italy).
High-resolution nannofossil biostratigraphy and C-isotopic chemostratigraphy identified the Jenkyns Event
within the Toarcian oceanic anoxic event (T-OAE) interval. Absolute abundances and morphometric changes of
“small S. punctulata” (< 7 μm), S. punctulata (7–10 μm; 10–14 μm; > 14 μm) and “encrusted S. punctulata”
(specimens with a fringing crust) show large fluctuations across the negative δ13C Jenkyns Event. The Schizo-
sphaerella crisis is further characterized by a decrease in average valve size in the early–middle Jenkyns Event.
The abundance fall was caused by the failure of S. punctulata specimens >7 μm and “encrusted S. punctulata” that
along with the increased relative abundance of small specimens, produced the reduction of average dimensions
also documented in the Lusitanian and Paris Basins, although with a diachronous inception. The average valve
size from the Lombardy Basin is ~2 μm smaller than in these other basins. Hyperthermal conditions associated
with excess CO2 and ocean acidification possibly forced the drastic reduction of S. punctulata abundance/size. In
the pelagic succession of the Sogno Core there is a strong positive correlation between the S. punctulata (> 7 μm)
absolute abundance/size and the CaCO3 content, with a negligible contribution by small specimens (< 7 μm).
Encrusted specimens testify selective neomorphic processes: the diagenetic crust seems diagnostic to separate
S. punctulata from S. astraea.
Tipologia IRIS:
01 - Articolo su periodico
Keywords:
Calcareous nannoplankton; Jurassic; Morphometry; Nannofossils; T-OAE
Elenco autori:
G. Faucher, S. Visentin, G. Gambacorta, E. Erba
Link alla scheda completa:
Link al Full Text: