23 research outputs found
Lateral variability of ichnological content in muddy contourites: Weak bottom currents affecting organismsâ behavior
Although bioturbation is commonly recognized in contourites, only a few studies have analyzed the
ichnological content of these deposits in detail. These studies have mainly focused on meso-scale
bigradational sequence (a coarsening upward followed by a fining-upward sequence resulting from
variations in current velocity). Here we present data from gravitational cores collected along the
NW Iberian Margin showing systematic variation in ichnological content across proximal to distal
depocenters within a large-scale elongated contourite drift. Data demonstrate that tracemakersâ
behavior varies depending on the distance relative to the bottom current core. Trace fossils are
already known to be a useful tool for studying of contouritic deposits and are even used as criterion
for differentiating associated facies (e.g., turbidites, debrites), though not without controversy. We
propose a mechanism by which the distance to the bottom current core exerts tangible influence on
specific macro-benthic tracemaker communities in contourite deposits. This parameter itself reflects
other bottom current features, such as hydrodynamic energy, grain size, nutrient transport, etc.
Ichnological analysis can thus resolve cryptic features of contourite drift depositional settings.The contribution and research by JD was funded through the European Unionâs Horizon 2020 research and
innovation programme under the Marie SkĆodowska-Curie grant agreement No 792314 (ICON-SE). The
research of FJR-T was funded by project CGL2015-66835-P (SecretarĂa de Estado de Investigacion, Desarrollo e
Innovacion, Spain), Research Group RNM-178 (Junta de AndalucĂa), and Scientific Excellence Unit UCE-2016-
05 (Universidad de Granada). AMâs research is funded by the I2C program of the Xunta de Galicia Postdoctoral
programme (ED481B 2016/029-0). The research was conducted as part of âThe Drifters Research Groupâ (RHUL)
and âIchnology and Palaeoenvironment Research Groupâ (UGR) programs
Radiocarbon geochronology of the sediments of the SĂŁo Paulo Bight (southern Brazilian upper margin)
Biogeography and conservation in Southeast Asia: how 2.7 million years of repeated environmental fluctuations affect todayâs patterns and the future of the remaining refugial-phase biodiversity
How many seals were there? The global shelf loss during the Last Glacial Maximum and its effect on the size and distribution of grey seal populations
The tagging studies were funded by the Natural Environment Research Council, UK; the Atlantic seal research program, Department of Fisheries and Oceans, Canada and NSERCD Discovery grants, Canada. This work also received funding from the MASTS pooling initiative (The Marine Alliance for Science and Technology for Scotland) and their support is gratefully acknowledged. MASTS is funded by the Scottish Funding Council (grant reference HR09011) and contributing institutions. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Predicting how marine mammal populations act to habitat changes will be essential for developing conservation management strategies by marine mammal ecologists in the 21st century. Responses to previous environmental change may be informative in the development of predictive models. Here we describe the likely effects of the last ice age on grey seal population size and distribution. We use satellite telemetry data to define grey seal foraging habitat in terms of the temperature and depth ranges exploited by the contemporary populations. We estimate the available extent of such habitat in the North Atlantic at present and at the last glacial maximum (LGM); taking account of glacial and seasonal sea-ice coverage, estimated reductions of sea-level (123m) and seawater temperature hind-casts from GLAMAP-2000. Most of the extensive continental shelf waters (North Sea, Baltic Sea and Scotian Shelf), currently supporting >95% of grey seals, were unavailable at the LGM. A combination of lower sea-level and extensive ice-sheets, massively increased seasonal sea-ice coverage and southerly extent of cold water would have pushed grey seals into areas with no significant shelf waters. The habitat during the LGM might have been as small as 4%, when compared to todayâs extent and grey seal populations may have fallen to similarly. An alternative scenario involving a major change to a pelagic/bathy-pelagic foraging niche cannot be discounted. However, hooded seals that appear to out-compete and effectively exclude grey seals from such habitat currently dominate that niche. If as seems likely, the grey seal population fell to very low levels it would have remained low for several thousand years before expanding into current habitats over the last 12000 years or so.Publisher PDFPeer reviewe