Description: Sediment delivery to the abyssal regions of the oceans is an integral process in the source to sink cycle of material derived from adjacent continents and islands. The Zambezi River, the largest in southern Africa, delivers vast amounts of material to the inner continental shelf of central Mozambique. The aim of this contribution is to better constrain sediment transport pathways to the abyssal plains using the latest, regional, high-resolution multibeam bathymetry data available, taking into account the effects of bottom water circulation, antecedent basin morphology and sea-level change. Results show that sediment transport and delivery to the abyssal plains is partitioned into three distinct domains; southern, central and northern. Sediment partitioning is primarily controlled by changes in continental shelf and shelf-break morphology under the influence of a clockwise rotating shelf circulation system. However, changes in sealevel have an overarching control on sediment delivery to particular domains. During highstand conditions, such as today, limited sediment delivery to the submarine Zambezi Valley and Channel is proposed, with increased sediment delivery to the deepwater basin being envisaged during regression and lowstand conditions. However, there is a pronounced along-strike variation in sediment transport during the sea-level cycle due to changes in the width, depth and orientation of the shelf. This combination of features outlines a sequence stratigraphic concept not generally considered in the strike-aligned shelf-slope-abyssal continuum.

Description: The tectonic opening of the Fram Strait (FS) was critical to the water exchange between the Atlantic Ocean and the Arctic Ocean, and caused the transition from a restricted to a ventilated Arctic Ocean during early Miocene. If and how the water exchange between the Arctic Ocean and the North Atlantic influenced the global current system is still disputed. We apply a fully coupled atmosphere–ocean–sea-ice model to investigate stratification and ocean circulation in the Arctic Ocean in response to the opening of the FS during early-to-middle Miocene. Progressive widening of the FS gateway in our simulation causes a moderate warming, while salinity conditions in the Nordic Seas remain similar. On the contrary, with increasing FS width, Arctic temperatures remain unchanged and salinity changes appear to steadily become stronger. For a sill depth of ~ 1500 m, we achieve ventilation of the Arctic Ocean due to enhanced import of saline Atlantic water through an FS width of ~ 105 km. Moreover, at this width and depth, we detect a modern-like three-layer stratification in the Arctic Ocean. The exchange flow through FS is characterized by vertical separation of a low-salinity cold outflow from the Arctic Ocean confined to a thin upper layer, an intermediate saline inflow from the Atlantic Ocean below, and a cold bottom Arctic outflow. Using a significantly shallower and narrower FS during the early Miocene, our study suggests that the ventilation mechanisms and stratification in the Arctic Ocean are comparable to the present-day characteristics.

Description: The transfer of sediment from the upper continental slope to rise is poorly documented along the southeast African passive margin. New swath bathymetric and sub-bottom data collected in the Natal Valley, southwest Indian Ocean, provide insight into the evolution of the Tugela canyon and fan system. Several distinct downslope changes in canyon morphology are noted. The canyon increases in relief and widens with depth. Basement outcrop is restricted to the head of the canyon becoming less prominent with depth. Step-like terracing of the canyon walls and floor becomes prominent in the mid-slope portions of the canyon and is related to a marked increase in the cross sectional asymmetry of the canyon profile. The contemporary Tugela canyon rests within a depression of the last phase of infilling. The canyon is the product of downslope erosion, and incision, caused by several phases of hinterland uplift in the mid Oligocene, mid Miocene and late Pliocene. Each phase was followed by pelagic infilling of the palaeo-canyon form. Downslope, the uplift phases are preserved in the cut-terraces and axial incisions within the main canyon thalweg. The contemporary canyon is a moribund feature, sediment starvation of the shelf area by current sweeping of the Agulhas current has decreased the material available for canyon incision and fan development. Additional current sweeping by the North Atlantic Deep Water current has stunted the development of the associated fan complex.

Description: The Mozambique Basin is one of the oldest extensional sedimentary basins developed along the eastern African margin. The basin hosts a continuous record of sediments since the Jurassic separation of Antarctica from Africa. The objectives of this study were to extend the regional stratigraphic framework north of the Zambezi Delta into the deep abyssal plains and review the early evolution of the Mozambique Basin using nine multi-channel seismic reflection profiles. We identify six major stratigraphic units that were deposited in Jurassic, Early Cretaceous, Late Cretaceous, Paleogene, Neogene and Quaternary times. Mesozoic sedimentation rates of 5-10 cm/kyr and 1-3 cm/kyr during the Paleogene are calculated in the deeper basin. The presence of shales in neighbouring wells on the shelf implies an euxinic environment in the rapidly subsiding basin until Early Cretaceous times. The Mesozoic sediments have a high seismic velocity that exceeds 4.5 km/s, except in a distinct Early Cretaceous low-velocity (3.7 km/s) zone that may indicate the presence of undercompacted, overpressured shales. In spite of the fact that the Zambezi catchment was much smaller in pre-Miocene times, the high Late Cretaceous sedimentation rates can be attributed to rapid denudation of the African continent after a major tectonic uplift episode at approximately 90 Ma. Increased sediment influx into the basin from the Zambezi in Late Cretaceous times resulted in the formation of an elongated submarine fan lobe into the Mozambique Channel north of Beira High. Strong north-south bottom currents commenced within the channel in Late Cretaceous times, forcing the aggradation of sediments on the southern flank of the lobe. In addition, we observe several current-controlled sediment deposits in the deeper basin that are influenced by north-south bottom currents. Low Paleogene sedimentation rates are attributed to a sediment-starved basin during a relative quiet tectonic phase onshore.

Description: During the RV Polarstern cruise ARK-XXIII-3 in the summer of 2008, seismic reflection and refraction data along an almost 1200 km long transect along 81�N latitude were acquired across the Amundsen Basin, Lomonosov Ridge, Makarov Basin, Mendeleev Ridge and parts of the Canada Basin. The seismic data are dominated by an unconformity/reflector band that is observed along the entire transect that separates a flat-lying well-stratified upper unit from the underlying sediment sequences. In our interpretation this reflector band spans a time interval from breakup of the Lomonosov Ridge from the Siberian/Barents shelves around 56 - 65 Ma to the top of the Oligocene. The velocity-depth functions indicate total sediment thicknesses ranging from 1200 to 2000 m on the Lomonosov Ridge, to 5500-6300 m within the deepest part of the Makarov Basin around 168�E, to 1000 e1500 m on the western flank of the Mendeleev Ridge, and, finally, to ~4000 m within the Canada Basin. The data show that stretched continental crust of the Lomonosov Ridge extends farther into the Makarov Basin than previously known. Horst and graben structures indicate that approximately 50% of the Makarov Basin along the 81�N transect is underlain by stretched continental crust. These structures most likely formed during a rift phase which is older than 56 Ma. Thick Mendeleev Ridge crust (up to 33 km) occupies the remaining portion of the basin. It is likely that the formation of this magmatic crust overprinted older oceanic crust during the Cretaceous Quiet Period (84e120 Ma).

Description: The glaciated Greenland continental margins contain favorable conditions for hydrate formation if gas is present. No gas hydrates have been encountered in the drilling of offshore wells, however, and only a limited focus has been placed on academic-led hydrate research to date. Nevertheless, analyses of 2D and 3D seismic reflection data have revealed the occurrence of BSRs, DHIs, chimneys and pockmarks. These seismic features all suggest the presence of gas and gas hydrates within three different sections of the Greenland margin. Seismic amplitude observations in Melville Bay, offshore northwest Greenland, indicate the existence of a *220 m thick gas hydrate deposit over a 50 m high gas column. It is suggested that the paleo-topography of the area has forced the migration of fluid into the overlying stratigraphy. In the Disco area, offshore central West Greenland, seismic observations together with heatflow measurements and sediment core samples suggest that gas and gas hydrates exist in regions with sub-cropping Cretaceous to Paleocene strata and in areas covered by thick postglacial sediments. Finally, 2D seismic reflection data indicate gas and gas hydrate deposits of potentially abiotic origin within the northeast Greenland margin and Molloy Basin, adjacent to the ocean spreading systems in the Fram Strait.