The Ebro Deep-Sea Fan system

The Ebro Fan System consists of en echelon channel-levee complexes, 50×20 km in area and 200-m thick. A few strong reflectors in a generally transparent seismic facies identify the sand-rich channel floors and levee crests. Numerous continuous acoustic reflectors characterize overbank turbidites and hemipelagites that blanket abandoned channel-levee complexes. The interlobe areas between channel complexes fill with homogeneous mud and sand from mass flow and overbank deposition; these exhibit a transparent seismic character. The steep continental rise and sediment “drainage” of Valencia Trough at the end of the channel-levee complexes prevent the development of distributary channels and midfan lobe deposits.     

Estimating Deep Seafloor Interface and Volume Roughness Parameters Using the Multibeam-Hydrosweep System

Utilizing a hull-mounted, multinarrow beam echosounder onboard RV Polarstern, we measured variation of acoustic backscatter with incidence angles at two different sites in the Southern Oceans (Agulhas Plateau and the Riiser Larsen Sea). We modeled the data, using a composite roughness model, including water-sediment interface roughness and sediment volume roughness parameters. The model effectively uses the near normal incidence angle backscatter to determine the seafloor interface roughness parameters employing Helmholtz-Kirchhoff theory. Beyond 20° incidence angles, an application of Rayleigh-Rice theory is made by using a necessary splicing technique (combining both of the theories at 20° incidence angle). The estimated interface and volume roughness parameters are found to be in accordance with the known area geology.     

Picophytoplankton: A major contributor to planktonic biomass and primary production in a eutrophic,river-dominated estuary

Biomass and primary productivity of picophytoplankton (PP; phytoplankton <3 μm) and larger phytoplankton (>3 μm) were determined during an annual cycle along the salinity gradient in North Carolina’s Neuse River Estuary (NRE), a eutrophic, microtidal estuary. The PP were a major component of total phytoplankton biomass and productivity, contributing ∼35–44% of the total chlorophyll a (Chl a) and 42–55% of the total primary productivity. Chl a and productivity of PP decreased from the upper to lower estuary, although the PP contribution relative to larger phytoplankton remained nearly constant. Significant PP growth occurred in the spring, but PP productivity and biomass were maximal in summer. PP productivity and biomass were positively correlated with temperature and dissolved inorganic phosphorus concentrations, which were maximal in summer due to release from sediments. Biomass and productivity of PP and >3 μm phytoplankton were also positively correlated, suggesting that growth conditions favoring the onset of blooms of larger phytoplankton species will similarly affect PP. High PP productivity and biomass in the NRE support the notion that PP play an important role in the production and eutrophication potentials of this estuary. High PP productivity and biomass have been noted in several other temperate estuaries, all sharing a common feature with the NRE—long residence time. These findings challenge the assumption that PP relative importance should be minimal in eutrophic systems.     

Zur Kenntnis der präkambrischen,schichtgebundenen Molybdänitvorkommen in Südnorwegen

The southern Norwegian molybdenum deposits have hitherto been looked upon as typical examples of deposits of pneumatolytic — catathermal origin formed by emanations from intrusive granites. It is now demonstrated that all these deposits are to be found stratabound in a series of grey gneisses. They are accompanied by varying amounts of graphite and apatite of biogenetic origin and all of them show the same sulphide and oxide ore mineral paragenesis. It is concluded that the concentration and precipitation of metals took place in marine environments. Both the ores and their host rocks later underwent the same highmetamorphic processes.     

Quaternary seismic stratigraphy of the North Sea Fan: glacially-fed gravity flow aprons, hemipelagic sediments, and large submarine slides

Approximately 1000 km of high resolution sleeve-gun array transects on the North Sea Fan, located at the mouth of the Norwegian Channel, reveal three dominant styles of sedimentation within a thick (> 900 m) Quaternary sediment wedge comprising numerous sequences. These are interpreted as: terrigenous hemipelagic sedimentation, large scale translational slides, and aprons of glaciogenic debris flow deposits contributing to considerable fan construction. Four large, buried translational slides involved sediment volumes upwards of 3000 km³ each and preceded the similarly dimensioned “first” Storegga Slide on the NE fan flank. Several thick (> 100 m) terrigenous hemipelagic deposits apparently represent long-lived (150–200 kyr) periods of sedimentation whose distribution indicates fan input via the Norwegian Channel. The upper sequences are each made upper sequences are each made up of one or several thick (> 100 m) aprons comprising stacked lensoid and/or lobate forms which range from 2 to 40 km in width and 15 to 60 m in thickness. They characterize debris flows attributed to periodic input from several phases of a Norwegian Channel ice stream reaching the shelf edge. Subsidence in the outer Norwegian Channel allowed preservation of several glaciation cycles represented by sheet erosion-bounded tills and progradational units. Much of the shelf/slope transition has been preserved, allowing a preliminary chronology of the fan sequences through correlation with borehole sediments in the Norwegian Channel. Debris flows, which signal the initial shelf-edge glaciation, are not recognized from the initial glaciation in the Channel (> 1.1 Myr) but are associated with a Middle Pleistocene and all following glacial erosion surfaces (GES) in the outer Norwegian Channel. This was followed by six further sequences, probably totalling over 13,000 km³ of sediment. At least four of these were shelf-edge ice-maximum events the last of which was Late Weichselian age (¹⁴C AMS). Considering earlier glaciation-related hemipelagic sedimentation, material since removed by the large slides, and extensive unmapped areas, total Quaternary fan sedimentation was in the vicinity of 20,000 km³.     

The dynamical behaviour of aN-shell model for an expanding universe

We consider a homogeneous expanding universe consisting of dust which is represented byN concentric massive spherical shells. We assume an explosive perturbation of the innermost shell at some instant of time. The effect of shell crossing and exchange of energy is investigated by deriving the equations of motion and obtaining their stationary and quasi-stationary solutions. Existing equilibrium stages and the density distribution for theN-shell system are discussed. Gravodynamics is a primary source for an understanding of gravitational clustering.