Oceanographic processes and products around the Iberian margin: a new multidisciplinary approach

Our understanding of the role of bottom currents and associated oceanographic processes (e.g, overflows, barotropic tidal currents) including intermittent processes (e.g, vertical eddies, deep sea storms, horizontal vortices, internal waves and tsunamis) is rapidly evolving. Many deep-water processes remain poorly understood due to limited direct observations, but may generate significant depositional and erosional features on both short-and long-term time scales. This paper describes these oceanographic processes and examines their potential role in the sedimentary features around the Iberian margin. The paper explores the implications of the processes studied, given their secondary role relative to other factors such as mass-transport and turbiditic processes. An integrated interpretation of these oceanographic processes requires an understanding of contourites, sea-floor features, their spatial and temporal evolution, and the near-bottom flows that form them. Given their complex, three-dimensional and temporally-variable nature, integration of these processes into sedimentary, oceanographic and climatological frameworks will require a multidisciplinary approach that includes Geology, Physical Oceanography, Paleoceanography and Benthic Biology. This approach will synthesize oceanographic data, seafloor morphology, sediments and seismic images to improve our knowledge of permanent and intermittent processes around Iberia, and evaluate their conceptual and regional role in the sedimentary evolution of the margin. © 2015, Instituto Geologico y Minero de Espana. All rights reservedEl conocimiento del papel de las corrientes de fondo y los procesos oceanográficos asociados (overflows, corrientes de marea barotrópicas, etc), incluyendo procesos intermitentes (eddies, tormentas profundas, ondas internas, tsunamis, etc), está evolucionando rápidamente. Muchos de estos procesos son poco conocidos, en parte debido a que las observaciones directas son limitadas, si bien pueden generar importantes rasgos deposicionales y/o erosivos a escalas temporales de corto o largo periodo. Este artículo describe dichos procesos oceanográficos y examina su influencia en la presencia de rasgos sedimentarios alrededor del margen Ibérico. El trabajo discute las implicaciones de dichos procesos y el papel secundario que juegan en relación a otros factores tales como los procesos de transporte gravitacionales en masa y los turbidíticos. Para un mejor conocimiento de la sedimentación marina profunda, y en concreto de los sistemas contorníticos, se requiere de una interpretación de estos procesos oceanográficos, cuál es su evolución espacial y temporal, cómo afectan a las corrientes de fondo y cómo se ven afectados por la topografía submarina. Sin embargo, dada su complejidad y su variable naturaleza tridimensional y temporal, es necesario que estos procesos se integren en un marco sedimentológico, oceanográfico y climatológico con un enfoque multidisciplinar que incluyan la Geología, la Oceanografía Física, la Paleoceanografía y la Biología bentónica. Esta integración requiere de una mayor compilación de datos oceanográficos, de un mejor conocimiento de la morfología del fondo marino, y de una mejor caracterización de los sedimentos en ambientes profundos. Todo ello permitirá mejorar nuestro conocimiento de los procesos permanentes e intermitentes alrededor de Iberia y evaluar su verdadero efecto en la evolución sedimentaria delos márgenes continentales que le rodeanPostprint0,000

Stagnant, oxygen reduced environment in the inner Kveithola Trough (Barents Sea): Preliminary report from the CORIBAR cruise (R/V Maria S. Merian, July-August 2013).

The Kveithola Through is a small, confined, sedimentary system that hosted a fast flowing ice stream during the last glacial maximum (Rüther et al., 2012; Bjarnadóttir et al., 2013). The inner area of the through contains a morphologically-complex sediment drift formed by two depocentres separated by the innermost Grounding Zone Wedge testifying the episodic retreat of the Kveithola ice stream after LGM (Rebesco et al., 2011). Bathymetry and seismic reflectors suggest a dynamic environment accompanied the build-up of the sediment drift with persistent currents scoop-out the northern moat (Hanebuth et al., 2013). Such a type of environment is in discordance with the present bottom environmental characteristics. Surface sediments in the Kveithola drift area are fine grained, soft and soupy with a “jellylike” consistency. The sea-bottom surface is usually cracked and slightly hummocky with cm-large, open holes similar to burrows, and small, mounded feature with a shallow depression on the top filled by black, organic matter rich sediments (Fig. 1). Indurated/cemented worm burrows were also observed. The sediments have a strong smell of H2S and they are mostly black, organic matter rich, with abundant worm tubes and occasionally reddish polychaetes living into the soft sediment surface (Fig. 1). The lack of any sediment structures indicating bottom currents and the presence of a benthic foraminiferal fauna typical of oxygen-depleted environments, suggest that the inner Kveithola through is presently a stagnant environment and the above described sedimentary structures are re-interpreted and associated to surface fluid escape

Why are some handaxes symmetrical? Testing the influence of handaxe morphology on butchery effectiveness

The morphology of Acheulean handaxes continues to be a subject of debate amongst Lower Palaeolithic archaeologists, with some arguing that many handaxes are over-engineered for a subsistence function alone. This study aims to provide an empirical foundation for these debates by testing the relationship between a range of morphological variables, including symmetry, and the effectiveness of handaxes for butchery. Sixty handaxes were used to butcher 30 fallow deer by both a professional and a non-professional butcher. Regression analysis on the resultant data set indicates that while frontal symmetry may explain a small amount of variance in the effectiveness of handaxes for butchery, a large percentage of variance remains unexplained by symmetry or any of the other morphological variables under consideration. © 2006 Elsevier Ltd. All rights reserved

Late Quaternary spatial and temporal variability in Arctic deep-sea bioturbation and its relation to Mn cycles

Changes in intensity and composition of bioturbation and trace fossils in deep-sea settings are directly related to changes in environmental parameters such as food availability, bottom water oxygenation, or substrate consistency. Because trace fossils are practically always preserved in situ, and are often present in environments where other environmental indicators are scarce or may have been compromised or removed by diagenetic processes, the trace fossils provide an important source of paleoenvironmental information in regions such as the deep Arctic Ocean. Detailed analysis of X-ray radiographs from 12 piston and gravity cores from a transect spanning from the Makarov Basin to the Yermak Plateau via the Lomonosov Ridge, the Morris Jesup Rise, and the Gakkel Ridge reveal both spatial and temporal variations in an ichnofauna consisting of Chondrites, Nereites, Phycosiphon, Planolites, Scolicia, Trichichnus, Zoophycos, as well as deformational biogenic structures. The spatial variability in abundance and diversity is in close correspondence to observed patterns in the distribution of modern benthos, suggesting that food availability and food flux to the sea floor are the most important parameters controlling variations in bioturbation in the Arctic Ocean. The most diverse ichnofaunas were observed at sites on the central Lomonosov Ridge that today have partially ice free conditions and relatively high summer productivity. In contrast, the most sparse ichnofauna was observed in the ice-infested region on the Lomonosov Ridge north of Greenland. Since primary productivity, and therefore also the food flux at a certain location, is ultimately controlled by the geographical position in relation to ice margin and the continental shelves, temporal variations in abundance and diversity of trace fossils have the potential to reveal changes in food flux, and consequently sea ice conditions on glacial–interglacial time scales. Down core analysis reveal clearly increased abundance and diversity during interglacial/ interstadial intervals that were identified through strongly enhanced Mn levels and the presence of microand nannofossils. Warm stages are characterized by larger trace fossils such as Scolicia, Planolites or Nereites, while cold stages typically display an ichnofauna dominated by small deep penetrating trace fossils such as Chondrites or Trichichnus. The presence of biogenic structures in glacial intervals clearly show that the Arctic deep waters must have remained fairly well ventilated also during glacials, thereby lending support to the hypothesis that the conspicuous brown layers rich in Mn which are found ubiquitously over the Arctic basins are related to input from rivers and coastal erosion during sea level high-stands rather than redox processes in the water column and on the sea floor. However, the X-ray radiograph study also revealed the presence of apparently post-sedimentary, diagenetically formed Mn-layers which are not directly related to Mn input from rivers and shelves. These observations thus bolster the hypothesis that the bioturbated, brownish Mn-rich layers can be used for stratigraphic correlation over large distances in the Arctic Ocean, but only if post sedimentary diagenetic layers can be identified and accounted for in the Mn-cycle stratigraphy