The recent drilling of IODP Site U1553, located in the Southern Ocean (Campbell Plateau), has provided a continuous sequence of deep marine sediments covering the late Eocene to early Oligocene interval, a crucial period for understanding the processes that led to the glaciation that characterizes the Eocene-Oligocene transition (EOT). The good state of preservation of the calcareous nannofossils and the high resolution of the sampling allowed us to perform accurate biostratigraphic, morphometric, and ecological analyses aimed at refining the biozonation of the Southern Ocean and reconstructing the response of marine ecosystems to the rapid climate changes of this interval. Twelve bioevents were recognized in approximately 79 m of succession, providing a detailed biostrachronostratigraphic picture. In addition, accurate biometric analyses documented the morphological transition from R. clatrata (8-10 μm) to R. oamaruensis (≥14 μm), mediated by intermediate forms called R. oamaruensis small (10-12 μm) and medium (12-14 μm), allowing us to improve the Southern Ocean biostratigraphic framework.Paleoecological analyses, mainly based onPCA and specific indices (TWWT and EI), have allowed us to quantify variations in taxon distribution, highlighting previously undocumented climatic phases, such as the “pre-LEE” (pre-Late Eocene Event) and the “TTI” (Temperate Transition Interval). The general trend shows a progressive decline in temperate-oligotrophic taxa and an increase in cold and eutrophic forms, in line with the evolution towards stable glacial conditions (Icehouse). Overall, the results from site U1553 provide an integrated picture combining biostratigraphy, morphological evolution, and paleoceanographic and paleoclimatic reconstructions, improving our understanding of the processes that accompanied the transition to the glacial state that characterized the Southern Ocean in the Oligocene.
Nannofossili calcarei dell’Oceano Meridionale nell’intervallo Eocene-Oligocene: implicazioni paleoecologiche, paleoclimatiche e paleoceanografiche / Catelli, V.. - (2026).
Nannofossili calcarei dell’Oceano Meridionale nell’intervallo Eocene-Oligocene: implicazioni paleoecologiche, paleoclimatiche e paleoceanografiche
CATELLI, VALENTINA
2026-01-01
Abstract
The recent drilling of IODP Site U1553, located in the Southern Ocean (Campbell Plateau), has provided a continuous sequence of deep marine sediments covering the late Eocene to early Oligocene interval, a crucial period for understanding the processes that led to the glaciation that characterizes the Eocene-Oligocene transition (EOT). The good state of preservation of the calcareous nannofossils and the high resolution of the sampling allowed us to perform accurate biostratigraphic, morphometric, and ecological analyses aimed at refining the biozonation of the Southern Ocean and reconstructing the response of marine ecosystems to the rapid climate changes of this interval. Twelve bioevents were recognized in approximately 79 m of succession, providing a detailed biostrachronostratigraphic picture. In addition, accurate biometric analyses documented the morphological transition from R. clatrata (8-10 μm) to R. oamaruensis (≥14 μm), mediated by intermediate forms called R. oamaruensis small (10-12 μm) and medium (12-14 μm), allowing us to improve the Southern Ocean biostratigraphic framework.Paleoecological analyses, mainly based onPCA and specific indices (TWWT and EI), have allowed us to quantify variations in taxon distribution, highlighting previously undocumented climatic phases, such as the “pre-LEE” (pre-Late Eocene Event) and the “TTI” (Temperate Transition Interval). The general trend shows a progressive decline in temperate-oligotrophic taxa and an increase in cold and eutrophic forms, in line with the evolution towards stable glacial conditions (Icehouse). Overall, the results from site U1553 provide an integrated picture combining biostratigraphy, morphological evolution, and paleoceanographic and paleoclimatic reconstructions, improving our understanding of the processes that accompanied the transition to the glacial state that characterized the Southern Ocean in the Oligocene.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
