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- Hernandez-Molina, F. J., et al.
(författare)
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Oceanographic processes and morphosedimentary products along the Iberian margins: A new multidisciplinary approach
- 2016
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Ingår i: Marine Geology. - : Elsevier BV. - 0025-3227. ; 378, s. 127-156
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Tidskriftsartikel (refereegranskat)abstract
- Our understanding 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 can generate significant depositional and erosional features on both short and long term time scales. This paper represents a review work, which describes for the first time these oceanographic processes and examines their potential role in the sedimentary features along the Iberian continental margins. This review explores the implications of the studied processes, given their secondary role relative to other factors such as mass-transport and turbiditic processes, and highlights three major results: a) contourite depositional and erosional features are ubiquitous along the margins, indicating that bottom currents and associated oceanographic processes control the physiography and sedimentation; b) the position of interfaces between major water masses and their vertical and spatial variation in time specifically appears to exert primary control in determining major morphologic changes along the slope gradient, including the contourite terraces development; and c) contourites deposits exhibit greater variation than the established fades model suggests. Therefore, a consistent facies model however faces substantial challenges in terms of the wide range of oceanographic processes that can influence in their development. An integrated interpretation of these oceanographic processes requires an understanding of contourites, seafloor features, their spatial and temporal evolution, and the near-bottom flows that form them. 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 margin's sedimentary evolution. Given their complexes, 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.
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| 2. |
- Hernandez Molina, Javier, et al.
(författare)
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Oceanographic processes and products around the Iberian margin: a new multidisciplinary approach : Procesos oceanográficos y sus productos alrededor del margen de Iberia: una nueva aproximación multidisciplinar
- 2015
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Ingår i: Boletín Geológico y Minero. - 0366-0176 .- 0366-0176. ; 126:2-3, s. 279-326
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Tidskriftsartikel (refereegranskat)abstract
- Our understanding of the role of bottom-current and associated oceanographic processes (as overflows, barotropic currents, tides or intermittent processes like giant vertical eddies, deep sea storms, horizontal vortices, internal waves and tsunamis) is rapidly improving. But, most of these oceanographic deep-water processes remains poorly understood and have been rarely observed but believed to be capable of generating depositional and erosional features in many contexts at both short and long term. In present compilation we described these oceanographic processes including examples or their potential role in the sedimentation processes around the Iberia margin. Importance of these processes is highlighted and its implication discussed to demonstrate that these oceanographic processes are very important is affecting the shape and evolution of the Iberian continental margin and adjacent oceanic basins although is not still considered as important as other factors as mass-transport deposits and turbiditic processes. To have a better understanding on the implication of all these oceanographic processes connections have to be made between (contourite) sea-floor features, their spatial and temporal evolution, and the near-bottom flows that form them. The only way to achieve that in next decades is by a more intensive collaboration between specialist from Geology, Oceanography and Benthic Biology in new multi-disciplinary studies. Consequently, further multi-disciplinary approach uses oceanographic data, sea-floor morphology, sediments and seismic characterization will be essential for improve our knowledge of these permanent and intermittent processes around Iberia and evaluate their conceptual and regional role in the margins evolution over time and space.
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| 3. |
- Löwemark, Ludvig, et al.
(författare)
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Late Quaternary spatial and temporal variability in Arctic deep-sea bioturbation and its relation to Mn cycles
- 2012
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Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 0031-0182 .- 1872-616X. ; 365-366, s. 192-208
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Tidskriftsartikel (refereegranskat)abstract
- 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 micro- and 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.
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