Angela Girone

Coccolithophores as proxy of seawater changes at orbital-to-millennial scale during middle Pleistocene Marine Isotope Stages 14–9 in North Atlantic core MD01-2446

Quantitative coccolithophore analyses were performed in core MD01-2446, located in the midlatitude North Atlantic, to reconstruct climatically induced sea surface water conditions throughout Marine Isotope Stages (MIS) 14–9. The data are compared to new and available paleoenvironmental proxies from the same site as well as other nearby North Atlantic records that support the coccolithophore signature at glacial-interglacial to millennial climate scale. Total coccolithophore absolute abundance increases during interglacials but abruptly drops during the colder glacial phases and deglaciations. Coccolithophore warm water taxa (wwt) indicate that MIS11c and MIS9e experienced warmer and more stable conditions throughout the whole photic zone compared to MIS13. MIS11 was a long-lasting warmer and stable interglacial characterized by a climate optimum during MIS11c when a more prominent influence of the subtropical front at the site is inferred. The wwt pattern also suggests distinct interstadial and stadial events lasting about 4–10 kyr. The glacial increases of Gephyrocapsa margereli-G. muellerae 3–4 µm along with higher values of Corg, additionally supported by the total alkenone abundance at Site U1313, indicate more productive surface waters, likely reflecting the migration of the polar front into the midlatitude North Atlantic. Distinctive peaks of G. margereli-muellerae (>4 µm), C. pelagicus pelagicus, Neogloboquadrina pachyderma left coiling, and reworked nannofossils, combined with minima in total nannofossil accumulation rate, are tracers of Heinrich-type events during MIS12 and MIS10. Additional Heinrich-type events are suggested during MIS12 and MIS14 based on biotic proxies, and we discuss possible iceberg sources at these times. Our results improve the understanding of mid-Brunhes paleoclimate and the impact on phytoplankton diversity in the midlatitude North Atlantic region.

PALEOBATHYMETRIC INTERPRETATION OF THE FISH OTOLITHS FROM THE LOWER - MIDDLE QUATERNARY DEPOSITS OF KEPHALLONIA AND ZAKYNTHOS ISLANDS (IONIAN SEA, WESTERN GREECE)

Fish otoliths are herein used to estimate the depositional depth of the Early - Middle Pleistocene deposits at SE Zakynthos and SW Kephallonia Islands (Ionian Sea, Western Greece), through comparison with the modern bathymetric distributions of the identified fish taxa. These estimates provide a more detailed picture of the depth variations for the Gelasian - Ionian stage interval in the study areas. The Lower Pleistocene marine deposits of the Gerakas Formation (SE Zakynthos Island, Ionian Sea) were deposited at average depths of 400-450 meters, with eustacy playing an important role in the depth variability, between 1.95-1.73 Ma. An uplifting episode, followed by subsidence takes place between 1.73-1.66 Ma, taking the area to 200-300 meters of depth, and then back to 400-500 meters. However, the area seems uplifted again to 200-400 meters later on in the Calabrian stage (1.25-0.97 Ma). Sedimentation of the Akrotiri deposits (NW Kephallonia Island, Ionian Sea), during the same chronostratigraphic interval, took place in a similar setting. At the Early Pleistocene (1.95-1.73 Ma) this basin reached depths of 400-450 meters, with uplift and following subsidence taking place between 1.73-1.66 Ma. Overall, the application of fish otolith paleobathymetry in the study areas provide a detailed picture of the depth variations for the Early Quaternary interval and refine the currently hypothesized pattern of tectonic movements.

Climate variability through the Marine isotope Stage 19 in the Bradano Trough (Southern Italy): a multi-proxy record

Abstract from 88th Congress of the Italian Geological Society, 2016-09-07 - 2016-09-09, NaplesAbstract from 88th Congress of the Italian Geological Society, 2016-09-07, 2016-09-09, Naplesbook Edited by D. Calcaterra, S. Mazzoli, F.M. Petti, B. Carmina & A. Zuccari doi: 10.3301/ROL.2016.79

The Montalbano Jonico Section (Southern Italy): A Candidate for the GSSP of the Ionian Stage (Lower–Middle Pleistocene Boundary)

The Lower–Middle Pleistocene Subseries boundary and the Ionian Stage still lack formal ratification. The use of the name “Ionian” as a stage of the Middle Pleistocene follows Cita et al. (2006, 2008) and Gibbard et al. (2009). The GSSP of the Ionian Stage should be defined at a point close to the Matuyama–Brunhes (M–B) reversal, in a marine section exposed on land. However, magnetic reversal is considered as only one of multiple criteria that may be used for the definition of a GSSP (Head et al. 2008). The Montalbano Jonico section (Southern Italy) is a continuous marly–clayey marine succession, well exposed and astronomically calibrated, which extends from 1.24 to 0.645 Ma (Ciaranfi et al. 2009). It spans the interval from Marine Isotope Stage (MIS) 37 to 17/16 and covers, together with the Vrica section, the sedimentary record of the entire Calabrian Stage. The section encompasses MIS 19, whose base corresponds closely to the M–B boundary (Lisiecki and Raymo 2005); unfortunately, the M–B palaeomagnetic reversal was not identified in the Montalbano sediments (Sagnotti et al. 2010). The isotopic signals are considered acceptable for the definition of a boundary stratotype (Remane et al. 1996) and the practice has been recently adopted for the definition of the GSSP of the Serravallian Stage (Hilgen et al. 2010). The interval including MIS 19 is chronologically well constrained and is a maximum flooding surface, as shown by the occurrence of the Neopycnodonte palaeocommunity, and the mesopelagic tropical–subtropical Atlantic teleostean Bonapartia pedaliota marks the base of the interglacial. Evidence of glacio-eustatic sea level rise, correlated with MIS 19 and the M–B boundary, are well known in several geographical areas, supporting the wide traceability of this oxygen isotope shift. The onset of MIS 19 in the Montalbano Jonico section may represent an appropriate stratigraphic horizon for the definition of the GSSP of the Ionian Stage, also fulfilling the additional criteria of Remane et al. (1996) for boundary stratotype definition, such as continuous sedimentation, a high sedimentation rate, an absence of synsedimentary disturbance, and good preservation and protection of the section.