The imprint of the geological inheritage and present dynamics on uruguayan inner shelf sediments (south-western Atlantic)

The Uruguayan continental shelf is characterised by a unique hydrographic system, composed of the Río de la Plata buoyant plume (RdlP-BP), and by water masses of contrasting thermohaline characteristics. Below the RdlP-BP the southward-flowing Subtropical Shelf Water and the northward-flowing Subantarctic Shelf Water converge at the Subtropical Shelf Front, which is the shelf extension of the Brazil-Malvinas Confluence. Three main sedimentary environments can be described associated with; I) “Atlantic coastal sands” (i.e. onshore from the palaeovalley); II) the SW-NE running “RdlP palaeovalley” and; III) “Relict sands” (i.e., offshore of the RdlP palaeovalley). Three exposed sedimentary units (U1 to U3) identified from acoustic profiles and sediment cores (sedimentary characteristics of stratigraphic units) almost entirely restricted to the palaeovalley. The transect here studied intersects these three environments contributing thus with the description of the morphological setting and sedimentary coverture. Physical and geochemical data were integrated and used to characterise the sedimentary facies previously described in the inner shelf and to understand environmental control on the development of these facies. Sediments from U1 show the terrestrial imprint of the RdlP and drier regional conditions, while sediments that characterised U3 indicate a sandy facies (quartz and bioclasts: whole and fragmented shells and polychaetes tubes) corresponding to an ancient coast. This last (with approximately 11 m height), is probably related to sea-level stabilization, between 20 and 25 m occurring during the Upper Pleistocene and Holocene for the South-Western Atlantic. The sediment from U3 reflects the colder and drier conditions prevailing in the region during the formation of this facies (13.7 and 9.7 cal ka BP). Eroded sediments (e.g., from U3; ancient coast) are deposited inside the palaeovalley and on the onshore region (between the palaeovalley and coastal sands). Also, U1 extends from the palaeovalley covering the onshore region. The outcrop of warmer oceanic shelf waters was probably a consequence of the geomorphology of the palaeovalley (edge of the palaeovalley) and related to the still fall presence of waters typical of the austral warm season when higher advection of Brazil Current occurs over the shelf. In this regard, the mound-like feature should induce bottom water to rise, operating as a ramp. Productivity proxies (Si/Ti, Ba/Ti, Ca/Ti and P/Ti) present the highest values in these stations (S16-S18), reflecting the imprint of the upwelling in the sediment. The information reported in this work is particularly important to better understand sedimentological dynamics in the Uruguayan inner shelf and the Southwestern Atlantic region. It is also important for elaborating more precise paleoenvironmental and palaeoceanographic reconstructions

Deep pockmarks as natural sediment traps: a case study from southern Santos Basin (SW Atlantic upper slope)

This study examines the role of deep pockmarks in acting as natural sediment traps. Multibeam bathymetry, single-channel seismic and sediment samples data were used for describing the morphology of pockmarks as well as the nature of sediments inside and outside these depressed features, in an area of Santos Basin (SW Atlantic upper slope), dominated by the strong flow of Brazil Current. Results show that the grain size and chemical composition of sediments inside pockmarks are distinct from the outside. Also, radiocarbon dating shows that Holocene ages are found only in samples located inside the pockmarks. Combination of sedimentological, geochemical and geochronological data allowed to recognise that deep pockmarks might present distinct sediment deposition processes when compared with those of shallow pockmarks, in which turbulence impedes sediment deposition, as reported in the literature.The authors acknowledge the crew and researchers of the two surveys held in 2016 and 2017, onboard R.V. Alpha Crucis. The São Paulo Science Foundation (FAPESP, grants 2014/08266-2, 2016/22194-7 and 2015/17763-2) funded this work. Partnerships between MM.de M., U.S. and F.L-S., are funded by FAPESP (grant 2017/50191-8) and the Brazilian National Research Council (CNPq, grant 401041/2014-0), respectively. M.M.de M. acknowledges CNPq for the research grants 303132/2014-0 and 300962/2018-5. This study was financedin partby the Coordenação deAperfeiçoamento dePessoal de Nível Superior – Brasil (CAPES) – Finance Code 001 (R.B.R. MSc. Scholarship)

International regulatory responses to global challenges in marine pollution and climate change

Marine pollution, also referred to as \u27pollution of the marine environment\u27, may occur as a result of different activities. Examples are land-based activities, vessel-related activitiese, dumping at sea, atmospheric and offshore hydrocarbon exploration, seabed mining, and so on. As discussed in Chapter 4, these types of marine pollution are often transboundary in nature and are harmful to human health and marine ecosystem. Similarly, climate change is a global issue involving the interests of all States. The Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), finalized and published in 2014, has further confirmed the existence of global warming when compared with the previous IPCC reports. It indicates that climate change has negatively affected natural and human systems on all continents and across the oceans, and asserts that 280substantial and sustained reduction of greenhouse gas (GHG) emissions would contribute to the tackling of climate change. 1 International issues need international responses. Both the marine pollution and climate change are issues with international dimensions, and thus require the global regulation by the international community