Experimentos de disolución de CaCO_3 en foraminíferos bentónicos aglutinados del Paleoceno-Eoceno en Zumaya (Cuenca Vasco-Cantábrica, España)

Durante el evento de calentamiento global conocido como Máximo Térmico del Paleoceno-Eoceno (PETM por sus siglas en inglés; hace ~55.8 Ma) tuvo lugar la mayor extinción de foraminíferos bentónicos de medios profundos de todo el Cenozoico. Mucho se ha especulado sobre las causas de dicha extinción, que incluyen cambios en la productividad y/o en la oxigenación de las aguas, cambios metabólicos y en la composición del aporte alimenticio al fondo marino, o la acidificación de los océanos relacionada con el aporte masivo de isótopos de carbono ligero al sistema océano-atmósfera, entre otros. En el presente estudio se analiza el potencial de la acidificación como agente desencadenante de las extinciones. En el corte de Zumaya (Cuenca Vasco-Cantábrica), el Eoceno inicial está marcado por un intervalo de 4 m con muy bajo contenido en CaCO3. Con el fin de analizar si la disolución del carbonato tuvo una incidencia directa sobre las extinciones del PETM, se han realizado experimentos de disolución en diversas especies de foraminíferos bentónicos aglutinados procedentes de Zumaya. En general, las especies aglutinadas que no desaparecen en el intervalo de máxima disolución en Zumaya son aquellas que fueron poco o nada afectadas por los experimentos de disolución, pues no presentan partículas y/o cemento calcáreo. No obstante, algunas especies que se extinguieron y/o desaparecieron localmente durante el Eoceno inicial, como Dorothia cylindracea, Spiroplectammina spectabilis y Haplophragmoides cf. walteri, resultaron ser resistentes a la disolución. Estos resultados sugieren que, además de la acidificación, debieron darse otros factores que contribuyeron a la desestabilización de las asociaciones de foraminíferos bentónicos

Updating a Paleogene magnetobiochronological time scale through graphical integration

All studies focused on the evaluation of paleoecological variability over geological time must be linked to a specific age or time interval, which can be defined using different time scales (biostratigraphic, chronostratigraphic, geochronological or orbital). Therefore, integrated time scales are essential to allow comparisons of data from different locations and/or to assess evolutionary and other events through time. Here we use a new method to update a Paleogene magnetobiochronological time scale, with the following contributions: • The update of the Paleogene magnetobiochronological scale was made by graphical correlation with new age models and adding calcareous nannoplankton and planktonic foraminiferal biozones from different authors. • An excel file structure was proposed to plot any kind of data in MATLAB software, as long as they are associated with some of the scales shown in our updated version of Paleogene magnetobiochronology. • The excel file structure facilitates the analysis of long-term trends of taxonomic groups throughout the Paleogene, and of their evolution in a period characterized by intense climate variability

Turnover and stability in the deep sea: Benthic foraminifera as tracers of Paleogene global change

Benthic foraminifera are the most common meiofaunal unicellular deep-sea biota, forming skeletons used as proxies for past climate change. We aim to increase understanding of past non-analog oceans and ecosystems by evaluating deep-sea benthic foraminiferal responses to global environmental changes over latest Cretaceous through Oligocene times (67–23 million years ago). Earth suffered an asteroid impact at the end of the Cretaceous (~instantaneous; 66 Ma), episodes of rapid global warming during the Paleocene-Eocene Thermal Maximum (PETM; ~56 Ma) and other hyperthermals (millennial timescales), followed by gradual, but punctuated cooling (timescales of hundred thousands of years) from a world without polar ice sheets to a world with a large Antarctic ice sheet. Here we present the first compilation of quantitative data on deep-sea foraminifera at sites in all the world''s oceans, aiming to build a first unique, uniform database that allows comparison of deep-sea faunal turnover across the uppermost Cretaceous through Paleogene. We document variability in space and time of benthic foraminiferal diversity: lack of extinction at the asteroid impact even though other marine and terrestrial groups suffered mass extinction; major extinction at the PETM followed by recovery and diversification; and gradual but fundamental turnover during gradual cooling and increase in polar ice volume (possibly linked to changes in the oceanic carbon cycle). High latitude cooling from ~45 Ma on, i.e., after the end of the Early Eocene Climate Optimum (53.2–49.2 Ma), may have made the middle Eocene a critical period of several millions of years of faunal turnover and establishment of latitudinal diversity gradients. This compilation thus illuminates the penetration of global change at very different rates into the largest and one of the most stable habitats on Earth, the deep sea with its highly diverse biota