Percorrer por autor "Flores, José-Abel"
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- Coccolithophores as proxy of seawater changes at orbital-to-millennial scale during middle Pleistocene Marine Isotope Stages 14-9 in North Atlantic core MD01-2446Publication . Marino, Maria; Maiorano, Patrizia; Tarantino, Francesca; Voelker, Antje; Capotondi, Lucilla; Girone, Angela; Lirer, Fabrizio; Flores, José-Abel; Naafs, B. David A.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.
- 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.
- A new perspective of the Alboran Upwelling System reconstruction during the Marine Isotope Stage 11: a high-resolution coccolithophore recordPublication . González-Lanchas, Alba; Flores, José-Abel; Sierro, Francisco J.; Bárcena, María Ángeles; Rigual-Hernández, Andrés S.; Oliveira, Dulce; Azibeiro, Lucía A.; Marino, Maria; Maiorano, Patrizia; Cortina, Aleix; Cacho, Isabel; Grimalt, Joan O.A high-resolution study of the MIS 12/MIS 11 transition and the MIS 11 (430-376 kyr) coccolithophore assemblages at Ocean Drilling Program Site 977 was conducted to reconstruct the palaeoceanographic and climatic changes in the Alboran Sea from the variability in surface water conditions. The nannofossil record was integrated with the planktonic oxygen and carbon stable isotopes, as well as the U-37(k') Sea Surface Temperature (SST) at the studied site during the investigated interval. The coccolithophore primary productivity, reconstructed from the PPP (primary productivity proxy = absolute values of Gephyrocapsa caribbeanica + small Gephyrocapsa group) revealed pronounced fluctuations, that were strongly associated with variations in the intensity of the regional Alboran Upwelling System. The comparison of the nannoplankton record with opal phytolith content for the studied site and the already available pollen record at the nearby Integrated Ocean Drilling Program Site U1385, suggests an association of the upwelling dynamics with the variability of the North Atlantic Oscillation-like (NAO-like) phase. High PPP during positive (+) NAO-like phases is the result of intensified upwelling, owing to the complete development of the surface hydrological structures at the Alboran Sea. This scenario was identified during the MIS 12/MIS 11 transition (428-422 kyr), the late MIS 11c (405-397 kyr), and MIS11 b to MIS 11a (397-376 kyr). Two short-term minima in the PPP and SST were observed during MIS 11 b and were coeval with the North Atlantic Heinrich-type (Ht) events Ht3 (similar to 390 kyr) and Ht2 (similar to 384 kyr). Increased abundance of the subpolar Coccolithus pelagicus subsp. pelagicus and Gephyrocapsa muellerae was consistent with the inflow of cold surface waters into the Mediterranean Sea during the Ht events. Lowered PPP during negative (-) NAO-like phases is the result of moderate upwelling by the incomplete development of surface hydrological structures at the Alboran Sea. This scenario is expressed during the early MIS 11c (422-405 kyr). Overall, the results of our study provide evidence of the important role of atmospheric circulation patterns in the North Atlantic region for controlling phytoplankton primary production and oceanographic circulation dynamics in the Western Mediterranean during MIS 11.
- Tropical ecosystem shifts at the Eocene–Oligocene transition in the southwestern Caribbean regionPublication . Trejos-Tamayo, Raúl; Garzón, Darwin; Ochoa, Diana; Plata-Torres, Angelo; Frontalini, Fabrizio; Vallejo-Hincapié, Felipe; Abrantes, Fatima; Magalhães, Vitor; Arias-Villegas, Viviana; Jaramillo, Carlos; Escobar, Jaime; Curtis, Jason H.; Flores, José-Abel; Osorio-Tabares, Constanza; Duque Castaño, Monica Liliana; Bedoya, Erika; Pardo-Trujillo, AndrésThe Eocene-Oligocene transition (EOT; similar to 34 Ma) marks a pivotal climatic shift from a warm, ice-free world to a cooler, glaciated climate driven by a significant decline in atmospheric pCO2 levels. This global cooling event, characterized by the first major Antarctic glaciation and a similar to 50 m sea-level fall, triggered selective extinctions in marine ecosystems and restructured sedimentary processes, making it one of the most significant climatic events of the Cenozoic. While the global impacts of the EOT are well documented, its effects on the marine environment of NW South America remain poorly understood. This region's unique position as a connection between the Pacific and Atlantic oceans before the closure of the Central American Seaway provides a valuable window into tropical ecosystem responses during this period. This study integrates micropaleontological and geochemical data from the ANH-SJ-1 drill core in the Colombian Caribbean to evaluate the impacts of global climatic shifts on tropical marine ecosystems. Palynological indicators, including the terrestrial/marine (T/M) index, along with XRF-derived elemental ratios (Zr/Rb, Ti/Al, K/Al, and K/Rb), reflect enhanced continental input during the EOT. These patterns suggest intensified erosion and detrital transport to bathyal depths, likely driven by rapid sea-level fall and hypopycnal flows. Calcareous nannofossil trophic indices reveal elevated surface productivity, likely fueled by increased continental nutrient influx, supported by higher Ba/Ti ratios that indicate enhanced organic matter export to the seafloor. The resulting oxygen depletion favored infaunal over epifaunal benthic foraminifera, marking a shift in community structure. Improved carbonate preservation across the transition, evidenced by a shift from agglutinated to calcareous benthic foraminifera and higher Ca/Ti ratios, reflects a deepening of the carbonate compensation depth (CCD), likely due to enhanced alkalinity from continental weathering. A positive delta 13Corg excursion (similar to 0.84 parts per thousand) aligns with global records and supports contributions from organic carbon oxidation, volcanic inputs, and weathering. Although limited by the number of available samples and low fossil abundances in some intervals, our multiproxy approach enables a coherent reconstruction of environmental dynamics. The ANH-SJ-1 record highlights the sensitivity of tropical systems to global climatic shifts and reinforces the importance of tropical data for understanding Cenozoic climate evolution and anticipating future ecosystem responses.