Browsing by Author "Trotta, Samanta"
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- Early Pleistocene calcareous nannofossil assemblages from the Gulf of Cadiz reveal glacial-interglacial and millennial-scale variabilityPublication . Trotta, Samanta; Marino, Maria; H L Voelker, Antje; Rodrigues, Teresa; Maiorano, Patrizia; Flores, José-Abel; Girone, Angela; Addante, Marina; Balestra, BarbaraCoccolithophore high resolution (300 years) quantitative analyses have been carried out on Early Pleistocene sediment samples from Integrated Ocean Drilling Program Site U1387 retrieved in the Gulf of Cadiz. The studied interval is well constrained by the delta 18O chronological frame and covers marine isotope stage (MIS) 48 to MIS 45, from 1465.9 ka to 1389.9 ka. The aim is to investigate paleoenvironmental changes during a poorly known interval of the "41 ky world" and understand how climate dynamics controlled coccolithophore abundance and variation at orbital up to millennial scale. Assemblage composition variation and Principal Component Analysis (PCA) indicate that temperature and nutrient availability are the main factors influencing coccolithophores. Precession forcing combined with hydrological and atmospheric dynamics affect changes in coccolithophore assemblage composition and abundance highlighting glacial-interglacial cycles and a millennial scale variability, which is more evident during glacials than during interglacials. Interglacial MIS 47 onset is more abrupt than MIS 45 inception in relation to a more prominent insolation maximum, which favors the sharp increase and highest abundance of warm water taxa in the early MIS 47. Short-term abundance peaks of C. pelagicus spp. pelagicus during glacials document polar-subpolar melting water influx into the Gulf of Cadiz and southward migration of the subpolar front during episodes of high volume ice-sheet in the north hemisphere and reduced Atlantic Meridional Overturning circulation. In late MIS 48 the lowest coccolithophore productivity, induced by colder and stratified surface waters, a terminal stadial has been inferred. Enhanced short-term glacial productivity is favored by higher mixing and nutrient content in surface water due to the strengthened westerly winds during symbolscript phases. This promotes arid condition and upwelling along the studied site. The interglacial short-term coccolithophore productivity increases are associated with insolation maxima and enhanced nutrients of land origin during more humid periods led by -NAO-like phases, which induce the southward position of the westerlies and higher precipitation in the Mediterranean region and North Africa, in agreement with the contemporary sapropel occurrences in Mediterranean Sea. Our data-set suggests a connection between climate dynamics in the Gulf of Cadiz and east of Gibraltar Strait during the Early Pleistocene as well as a relationship with the north hemisphere ice-sheet dynamics.
- High-frequency glacial climate instability during the early pleistocene: insights from IODP site U1387 (Gulf of Cadiz)Publication . Trotta, Samanta; Duque Castaño, Monica Liliana; Rodrigues, Teresa; Voelker, Antje; Maiorano, Patrizia; Balestra, Barbara; Flores, José-Abel; Siniscalchi, Agata; Addante, Marina; Marino, MariaWe provide new high-resolution data on alkenone-derived sea surface temperature (SST) and calcareous plankton key taxa in temporally well constrained, high resolution benthic and planktonic oxygen isotope records at Integrated Ocean Drilling Program site U1387 in the Gulf of Cadiz. The investigated time interval encompasses the Early Pleistocene marine isotope stages (MIS) 48 to MIS 43. The aim is to evidence millennial climate variability during glacial phases of the “41 kyr world” and understand the impact of North Atlantic climate dynamics on the southern Portuguese margin. Neogloboquadrina pachyderma and Coccolithus pelagicus ssp. pelagicus record prominent, short-term abundance peaks concurrent with short-term SST minima and heavier values of ™18O in late MIS 48 and in the middle of MIS 46 and MIS 44. Superimposed on the obliquity and precession forcing, the wavelet analysis carried out on selected proxies (planktonic ™18O, N. pachyderma, C. pelagicus ssp. pelagicus, alkenone derived sea surface temperature) highlighted the occurrence of a higher frequency climate variability.
- Multiproxy record of suborbital-scale climate changes in the Algero-Balearic Basin during late MIS 20-Termination IXPublication . Quivelli, Ornella; Marino, Maria; Rodrigues, Teresa; Girone, Angela; Maiorano, Patrizia; Bertini, Adele; Niccolini, Gabriele; Trotta, Samanta; Bassinot, FranckHigh-resolution quantitative analyses have been carried out in samples from the Ocean Drilling Program (ODP) Site 975 in the Algero-Balearic basin through late Marine Isotope Stage (MIS 20)-Termination IX (800-784 ka). The multi-proxy study combines data of planktonic delta O-18, delta C-13, calcareous plankton (coccolithophores, foraminifera), palynomorphs, alkenone-based sea surface temperature (SST), % alkenone tetraunsatured (% C-37:4), and terrigenous biomarkers (C-23-C-31 n-alkanes, C-22-C-30 n-alkanols) with the aim to reconstruct climate-induced paleoenvironmental changes at orbital-submillennial scale, in a crucial time interval of the Early-Midde Pleistocene transition. The surface water delta O-18(sw) has been reconstructed from delta O-18(G.bulloides) and alkenone-based SST as a proxy for salinity changes. The late MIS 20 has been subdivided in several phases based on evidence of (i) meltwater events of polar origin or from surrounding mountain glaciers, (ii) changes in the production rate of Western Mediterranean Deep Water (WMDW) and in deep water ventilation, (iii) variation in terrestrial input and river discharge, and iv) variations in the strength of the north westerlies, and polar front shift. Following a glacial stadial (lasting ca 3 kyr) marked by the strongest WMDW production, coeval with a boreal summer insolation minimum and a marked low sea level, the latest MIS 20 is characterized by a terminal stadial event (lasting ca 3.5 kyr), which is traced by the occurrence of cold-low salinity water, pointing to meltwater advection at the site location. Short-term warm and cool events occurred through Termination IX during sea level rise and insolation increase, preceding the onset of full MIS 19c, characterized by an organic rich layer (ORL) associated with insolation cycle 74. The succession of these climate and oceanographic events has been compared to evidences from other Mediterranean sites, highlighting similar basin-wide patterns, which recall the climate evolution of Termination I. The comparison of our results with the climate proxies from the Integrated Ocean Drilling Program (IODP) Site U1385 located west of Iberian margin made it possible to point at the connection between Mediterranean oceanographic and atmospheric dynamics and the northern hemisphere ice-sheet instability, providing insight on the relationship with the Atlantic meridional overturning circulation and thermal front migration. (C) 2021 Elsevier Ltd. All rights reserved.
- A southern Portuguese Margin Perspective of Marine Isotope Stage 47—An interglacial in the 41 kyr WorldPublication . Voelker, Antje; Rodrigues, Teresa; Trotta, Samanta; Marino, Maria; Kuhnert, HenningIn order to better understand interglacial climate variability within the 41 kyr world, we produced high-resolution climate records for interglacial Marine Isotope Stage (MIS) 47 (1424-1452 ka) at IODP Site U1387 (36 degrees 48 ' N, 7 degrees 43 ' W) on the southern Portuguese margin. Using benthic and planktonic foraminifera stable isotope records, U-37(k') sea-surface temperature (SST), and plankton assemblage data we investigated Mediterranean Outflow Water (MOW) and surface water conditions. The MOW-level records indicate a poorly ventilated and sluggish bottom current during the MIS 48/MIS 47 transition in association with the insolation maximum, whereas a well-ventilated MOW formed a contourite layer during the second insolation maximum. The benthic delta O-18 record shows a fairly abrupt change during the deglaciation of MIS 48, while the surface waters experienced a terminal stadial event that was associated with initial cooling and freshening followed by stepwise warming until interglacial SST was reached at 1450 ka. Interglacial conditions with SST of 24 degrees C or higher persisted until 1427 ka, although warm SST prevailed into MIS 46. The persistent and prolonged warmth is attributed to a northward expansion of the subtropical gyre during MIS 47 as reflected by the dominance of subtropical-tropical planktonic foraminifera species and the presence of warm water coccolithophores taxa.