SESS 5_16022011_edi as.pub Il Quaternario Italian Journal of Quaternary Sciences 24, (Abstract AIQUA, Roma 02/2011), Congresso AIQUA Il Quaternario Italiano: conoscenze e prospettive Roma 24 e 25 febbraio 2011 Quantitative analyses have been performed in high temporal resolution (one sample per 0.6-0.8 kyr) on calcareous nannofossil assemblages from core KC01B throughout the Pleistocene interval spanning Marine Isotope Stages (MIS) 9-13. This interval includes the Mid-Brunhes Event (MBE, JANSEN et al., 1986), a time of significant climate modification that experienced a warm and prolonged interglacial, MIS 11, considered the modern analogous of the Holocene. The MBE is also characterized by an increase of atmospheric CO2 and a global increased CaCO3 accumulation mainly linked to enhanced coccolithophores production associated with a high proliferation of Gephyrocapsa Genus in many oceanic settings (BARKER et al., 2006, cum biblio). The core KC01B, recovered by R/V Marion Dufresne at the water depth of 3643 meter in the Ionian Sea, represents a reference section for Pleistocene chronostratigraphy due to its continuous sedimentary record and richness in sapropel and tephra layers which contributed to establish the Astronomical Tuned Neogene Time Scale (LOURENS et al., 2004). The analyses revealed that the nannofossil assemblages mainly consist of Gephyrocapsa caribbeanica and G. muellerae, differently from the living and surface sediment associations recorded in Mediterranean Sea (KNAPPERTSBUSCH, 1993). Gephyrocapsa may reach up to 90% in the total assemblages. Other abundant taxa are “small placoliths”, and Florisphaera profunda, a deep dweller photic zone taxon indicative of deep nutricline (MOLFINO & MCINTYRE, 1990). These taxa have been used to obtain a paleoproductivity proxy (N index) according to FLORES et al. (2000). Comparison of abundance patterns of all taxa and N index with the planktonic oxygen isotope curve (ROSSIGNOL- STICK et al., 1998; LOURENS, 2004) provides details on the meaning of species fluctuations through the glacial/interglacial cycles. The pattern of classical “warm and oligotrophic” taxa does not have a clear positive relation with interglacials as it occurs in the oceans, suggesting a primary response to oligotrophic conditions rather than to temperature changes. In addition it shows opposite trends with respect to N index that has high values mainly during interglacials and glacial/interglacial transitions, especially from MIS 12 to MIS 11. G. muellerae mainly increases during glacial periods, in agreement with its known ecological preference for cold surface waters (BOLLMANN, 1997), whereas G. caribbeanica has higher abundance during interglacials and at the transition MIS 12/11, thus implying ecological preference for eutrophic and nutrient-rich surface waters during the investigated interval, according to LOPEZ-OTALVARO et al. (2008). A distinct interval of absence or extreme rarity of taxa indicative of warm and stratified surface waters (i.e. Umbilicosphaera sibogae) has been recorded through late MIS 12 and lower MIS 11 when also F. profunda decreases, suggesting persistent cold/cool conditions up to about 410 kyr in the early interglacial MIS 11, before the lowest CALCAREOUS NANNOFOSSIL ASSEMBLAGES AT CORE KC01B (IONIAN SEA) THROUGH OXYGEN MARINE ISOTOPE STAGES 9-13 Francesca Tarantino1, Patrizia Maiorano1, Maria Marino1, Gert J. De Lange2 & Lucas Lourens2 1 Dipartimento di Geologia e Geofisica, Università degli Studi di Bari “Aldo Moro”, Bari 2 Department of Earth Sciences – Geochemistry, Faculty of Geosciences, Utrecht University Corresponding author: F. Tarantino ABSTRACT: Tarantino F. et al., Calcareous nannofossil assemblages at core KC01B (Ionian Sea) through oxygen Marine Isotope Stages 9-13 (IT ISSN 0394-3356, 2011). Calcareous nannofossil assemblages from deep sea core KC01B in Ionian Sea have been analysed in high sample resolution (0.6-0.8 kyr) through the Pleistocene Marine Isotope Stages (MIS) 9-13 interval, which includes significant climate changes during the known Mid-Brunhes Event. Collected data show complex relationships between coccolithophores modification and environmental parameters. RIASSUNTO: Tarantino F. et al., Associazioni a nannofossili calcarei durante gli stadi isotopici 9-13 nella carota KC01B (Mar Ionio) (IT ISSN 0394-3356, 2011) Sono state studiate le associazioni a nannofossili calcarei nella carota di mare profondo KC01B recuperata nel Mar Ionio. Le analisi, condotte in alta risoluzione temporale (0,6-0,8 kyr) indicano complesse relazioni the le modificazioni delle associazioni e i cambiamenti dei parametri ambientali durante un intervallo di importanti variazioni climatiche conosciuto come Mid-Brunhes Event. Key words: calcareous nannofossils, Ionian Sea, core KC01B, MIS 9-13. Parole chiave: nannofossili calcarei, Mar Ionio, carota KC01B, MIS 9-13 219 - 220 220 Ms. received: Testo ricevuto il values of d18O (at about 405 kyr); also unstable and more productive conditions may have occurred at MIS 12/11 transition. Distinct peaks of Helicosphaera carteri mark the MIS 12/11 transition which seem in agreement with its ecological preferences for decreased salinity and high turbidity level (COLMENERO-HIDALGO et al. 2004) and possible r-selected life strategy. These results agree with the higher primary productivity during glacial-interglacial transitions documented in oceanic setting by LIU et al. (2003) who also retain that higher biogenic calcification (planktonic foraminifers and coccoliths) may lead the lightest δ18O. The preliminary data of the present study indicate that the modifications of nannofossil assemblages have relation with the global climate changes known in oceans during the investigated interval; however additional environmental factors different from the temperature alone (the complex local Ionian hydrography, the variability of surface Atlantic water influence at the core location, the nutrient availability in the photic zone) have to be considered to fully explain the poorly known paleoecology of selected taxa in Mediterranean Sea. REFERENCES BARKER S., ARCHER D., BOOTH L., ELDERFIELD H., HENDERIKS J. & RICKABY R. E. M. (2006) - Globally increased pelagic carbonate production during the Mid-Bruhnes dissolution interval and the CO2 paradox of MIS 11. Quaternary Science Reviews, 25, 3278-3293. BOLLMAN J. (1997) - Morphology and biogeography of Gephyrocapsa coccoliths in Holocene sediments. Marine Micropaleontology, 29, 319- 350. COLMENERO-HIDALGO E., FLORES J.A., SIERRO J., BARCENA M.A., LOWEMARK L., SCHONFELD J. & GRIMALT J.O. (2004) - Ocean surface water response to short-term climate changes revealed by coccolithophores from the Gulf of Cadiz (NE Atlantic) and Alboran Sea (W Mediterranean). Paleogeogr. Paleoclim. Paleoecol. 205, 317–336. FLORES J.A., GERSONDE R., SIERRO F. J. & NIEBLER H.-S. (2000) - Southern Ocean Pleistocene calcareous nannofossil events: calibration with isotope and geomagnetic stratigraphies. Marine Micropaleontology, 40, 377-402. KNAPPERTSBUSCH M. (1993) - Geographic distribution of living and Holocene coccolithophores in the Mediterranean Sea. Marine Micropaleontology, 21, 219 - 247. JANSEN J.H.F., KUIJPERS A. & TROELSTRA S.R. (1986) - A Mid-Brunhes Climatic Event: Long- Term Changes in Global Atmosphere and Ocean Circulation. Scienze 2, vol. 232, no. 4750, 619 – 622. LÓPEZ-OTÁLVARO G. E., FLORES J. A., FRANCISCO JAVIER SIERRO F. J. & CACHO I. (2008) - Variations in coccolithophorid production in the Eastern Equatorial Pacific at ODP Site 1240 over the last seven glacial–interglacial cycles. Marine Micropaleontology, 69, 52–69. LIU Z., XU J., TIAN J. & WANG P. (2003) - Calcium carbonate pump during Quaternary glacial cycles in the South China Sea. Chinese Science Bullettin, 48 (17), 1862-1869. LOURENS L. (2004) - Revised tuning of Ocean Drilling Program Site 964 and KC01B (Mediterranean) and implications for the d18O, tephra, calcareous nannofossil, and geomagnetic reversal chronologies of the past 1.1 Myr. Paleoceanography, 19, PA3010. LOURENS L., HILGEN F., SHACKLETON N. J., LASKAR J. & WILSON, D. (2004) - The Neogene Period, In: Gradstein F. M., Ogg J. G., & Smith A. G. (Eds) - A Geological Time Scale. Cambridge University Press, 409–440. MOLFINO B. & MCINTYRE A. (1990) - Nutricline variation in the equatorial Atlantic coincident with the Younger Dryas. Paleoceanography, 5 (6), 997 -1008. ROSSIGNOL-STRICK M., PATERNE M., BASSINOT F., EMEIS K.-C. & DE LANGE G. J. (1998) - An unusual mid-Pleistocene monsoon period over Africa and Asia. Nature, 392, 269-272. F. Tarantino et al. January 14, 2011 14 gennaio 2011