Sediment routing in the Zagros foreland basin: Drainage reorganization and a shift from axial to transverse sediment dispersal in the Kurdistan region of Iraq

In the northwestern sector of the Zagros foreland basin, axial fluvial systems initially delivered fine-grained sediments from northwestern source regions into a contiguous basin, and later transverse fluvial systems delivered coarse-grained sediments from northeastern sources into a structurally partitioned basin by fold-thrust deformation. Here we integrate sedimentologic, stratigraphic, palaeomagnetic and geochronologic data from the northwestern Zagros foreland basin to define the Neogene history of deposition and sediment routing in response to progressive advance of the Zagros fold-thrust belt. This study constrains the depositional environments, timing of deposition and provenance of nonmarine clastic deposits of the Injana (Upper Fars), Mukdadiya (Lower Bakhtiari) and Bai-Hasan (Upper Bakhtiari) Formations in the Kurdistan region of Iraq. Sediments of the Injana Formation (~12.4–7.75 Ma) were transported axially (orogen-parallel) from northwest to southeast by meandering and low-sinuosity channel belt system. In contrast, during deposition of the Mukdadiya Formation (~7.75–5 Ma), sediments were delivered transversely (orogen-perpendicular) from northeast to southwest by braided and low-sinuosity channel belt system in distributive fluvial megafans. By ~5 Ma, the northwestern Zagros foreland basin became partitioned by growth of the Mountain Front Flexure and considerable gravel was introduced in localized alluvial fans derived from growing topographic highs. Foredeep accumulation rates during deposition of the Injana, Mukdadiya and Bai-Hasan Formations averaged 350, 400 and 600 m/Myr respectively, suggesting accelerated accommodation generation in a rapidly subsiding basin governed by flexural subsidence. Detrital zircon U-Pb age spectra show that in addition to sources of Mesozoic-Cenozoic cover strata, the Injana Formation was derived chiefly from Palaeozoic-Precambrian (including Carboniferous and latest Neoproterozoic) strata in an axial position to the northwest, likely from the Bitlis-Puturge Massif and broader Eastern Anatolia. In contrast, the Mukdadiya and Bai-Hasan Formations yield distinctive Palaeogene U-Pb age peaks, particularly in the southeastern sector of the study region, consistent with transverse delivery from the arc-related terranes of the Walash and Naopurdan volcano-sedimentary groups (Gaveh-Rud domain?) and Urumieh-Dokhtar magmatic arc to the northeast. These temporal and spatial variations in stratigraphic framework, depositional environments, sediment routing and compositional provenance reveal a major drainage reorganization during Neogene shortening in the Zagros fold-thrust belt. Whereas axial fluvial systems initially dominated the foreland basin during early orogenesis in the Kurdistan region of Iraq, transverse fluvial systems were subsequently established and delivered major sediment volumes to the foreland as a consequence of the abrupt deformation advance and associated topographic growth in the Zagros.     

Cadmium release caused by the die-back of the saltmarsh cord grass Spartina anglica in Poole Harbour (UK)

As in many other areas, the perennial cord grass Spartina anglica C.E. Hubbard has been extremely successful at colonising the English and Irish south coasts, but it is dying back for reasons that are not completely understood. The present study considers the relationship between die-back and metal concentrations in estuarine sediment. No obvious impact of the metal contamination on the S. anglica growth/die-back could be detected in the study zone, Poole Harbour, although the die-back did seem to have substantially influenced the metal concentrations in the sediments of the estuary. Based on core profiles, the remaining patches of S. anglica still retain elevated concentrations and the overall cadmium concentrations in the sediments have risen since 1925. However, considerable quantities of the cadmium stored in the sediment by S. anglica appear to have been washed out rapidly in the die-back zones. Should serious erosion of the saltmarsh occur, triggered for example by sea-level rise, then sudden and high levels of cadmium release may cause harmful effects to marine biota.     

Storm surge induced flux through multiple tidal passes of Lake Pontchartrain estuary during Hurricanes Gustav and Ike

In September 2008, Hurricanes Gustav and Ike generated major storm surges which impacted the Lake Pontchartrain estuary in Louisiana. This paper presents analyses of in situ measurements acquired during these storm events. The main data used in the analyses were from three bottom mounted moorings equipped with conductivity, temperature, and depth sensors, acoustic Doppler current profilers (ADCPs), and a semi-permanent laterally mounted horizontal acoustic Doppler profiler (ADP). These moorings were deployed in the three major tidal channels that connect Lake Pontchartrain with the coastal ocean. A process similar to tidal straining was observed: the vertical shear of the horizontal velocity was negligible during the inundation stage, but a shear of 0.8 m/s over a less than 5 m water column was recorded during the receding stage, 2–3 times the normal tidal oscillations. The surge reached its peak in the Industrial Canal 1.4–2.1 h before those in the other two channels. The inward flux of water lasted for a shorter time period than that of the outward flux. The inward flux was also observed to have much smaller magnitude than the outward flux (∼960–1200 vs. 2100–3100 million m³). The imbalance was believed to have been caused by the additional water into Lake Pontchartrain through some small rivers and inundation over the land plus rainfall from the hurricanes. The flux through the Industrial Canal was 8–12%, while the flux through the other two tidal passes ranged between 17% and 70% of the total, but mostly split roughly half-half of the remaining (∼88–92% of the total).     

How U.S. ocean policy and market power can reform the coral reef wildlife trade

As the world’s largest importer of marine ornamental species for the aquaria, curio, home décor, and jewelry industries, the United States has an opportunity to leverage its considerable market power to promote more sustainable trade and reduce the effects of ornamental trade stress on coral reefs worldwide. Evidence indicates that collection of some coral reef animals for these trades has caused virtual elimination of local populations, major changes in age structure, and promotion of collection practices that destroy reef habitats. Management and enforcement of collection activities in major source countries such as Indonesia and the Philippines remain weak. Strengthening US trade laws and enforcement capabilities combined with increasing consumer and industry demand for responsible conservation can create strong incentives for improving management in source countries. This is particularly important in light of the March 2010 failure of the parties to the Convention on International Trade in Endangered Species (CITES) to take action on key groups of corals.     

Socio-economic drivers and indicators for artisanal coastal fisheries in Pacific island countries and territories and their use for fisheries management strategies

This is the first regional study of artisanal fisheries in Pacific Island countries and territories that demonstrated that the future of the region's artisanal fishery sector and the livelihood of coastal communities will be highly dependent on alternative subsistence and income sources, which are necessary to reduce fishing pressure to a sustainable level to maintain ecosystem services and food security. The overall objective of this study was to identify socio-economic indicators and drivers to improve the understanding of the dynamics between socio-economic conditions and current exploitation levels of finfish and invertebrates of coastal communities in 17 Pacific Island countries and territories. We showed that exploitation rates and thus possible overexploitation are not solely the consequence of a simple demographic growth process but are in fact a result of the choices people have. Our results confirmed a close relationship between resource exploitation rates and economic development at the national level and the availability of alternative income opportunities at the community level. Multivariate analysis results suggest that communities in countries with somewhat unfavourable conditions and limited access to alternatives and fishing households in communities with overall favourable economic conditions are at highest vulnerability as they have the highest dependence on coastal fisheries resources. Alternative economic opportunities at the national scale and availability of alternative income at the community level vary significantly between cultural groups. Based on our results, the development of management strategies with realistic expectations of ensuring livelihood of coastal communities and sustainable resource use in Pacific Island countries and territories requires a hierarchical and integral approach. Major drivers identified at the regional, cultural and local levels should be used to identify priorities, to assess overall advantages and limitations at the different levels as well as the vulnerability of communities targeted, and to develop strategies accordingly.     

Unsteady hydromechanics of a steering podded propeller unit

Unsteady forces, torques and bending moments were predicted for a model podded propulsor unit at various azimuth angles. Predictions in time history include propeller shaft thrust, propulsor unit thrust, normal forces to the propeller shaft bearing, total forces acting on the propulsor unit, propeller shaft torque, blade spindle torque, in-plane and out-of-plane bending moments, and propulsor unit stock shaft torque and bending moments. Analysis was performed for averaged forces and their fluctuations as well. A time-domain unsteady multi-body panel method code, PROPELLA, was further developed for this prediction work. Predictions were compared with a set of time averaged in-house experimental data for a puller-type podded propulsor configuration in the first quadrant operation. Unsteady fluctuations of forces were predicted numerically. Analysis was made for the bending moment on propeller blades, shaft and the propulsor unit stock shaft for azimuth angles from 0° to 45°. It indicates that the magnitude and fluctuation of the forces are significant and they are essential for structural strength and design optimization. The predicted bending moment and global forces on the propulsor unit provide some useful data for ship maneuvering motion and simulation in off-design conditions.     

Suspended matter in surface waters of the eastern Gulf of Guinea

Suspended matter in the surface waters of the eastern Gulf of Guinea was studied in relation to the prevailing oceanic currents and the sediment composition and source. A confused current system arises from the confluence of the Guinea Current and the South Equatorial Current in this area. Sediment-laden water is transported to the south of Fernando Póo into the Gulf in a south-westerly direction. The southeasterly flowing Guinea Current along the western edge of the Niger delta and the enormous sediment loads of the distributaries in this area contribute to a major lobe of suspended matter off the southwestern nose of the delta. Sediment concentration is inversely related to salinity in the northeastern Gulf. Sediment is also swept northwestward from the continental shelf of Gabon and the Congo Republic into the Gulf. Diatoms are the most abundant constituents with lesser amounts of organic aggregates and two varieties of fecal pellets.