Plate boundaries and evolution of the Solomon Sea region

The Solomon Sea Plate was widely developed during late Oligocene, separating the proto-West Melanesian Arc from the proto-Trobriand Arc. Spreading in the Bismarck Sea and in the Woodlark Basin resulted from interaction between the Pacific and Australian Plates, specifically from the collision of the proto-West Melanesian Arc with north New Guinea, which occurred after arc reversal. This model explains the extensive Miocene, Pliocene, and Quaternary volcanism of the Papua New Guinea mainland as it related to southward subduction of the Trobriand Trough. Our interpreted plate motions are concordant with the geological evidence onshore and also with complex tectonic features in the Solomon Sea Basin Region.     

Benthic Metabolism and Standing Stock in the Central and Northern Deep Red Sea

Abstract. Benthic metabolism and standing stocks were investigated in the deep Red Sea between 21^o and 27^oN, Activity was assessed by the determination of respiration rates with a shipboard method and by calculating oxygen consumption from the activity in the electron transport system. We attempted to compare results from different latitudes within the warm Red Sea and with data from cold Atlantic environments. Our investigations were part of an environmental risk assessment to evaluate future mining of metalliferous sediments from the Atlantis II Deep.     

Gravity anomalies over inactive fracture zones in the central North Atlantic

The basement topography and the free-air gravity along two profiles in the central North Atlantic between 16° and 25° N, crossing a number of fracture zones, were divided in three wavelength intervals. Two-dimensional modelling shows that the short wavelength (>50 km) gravity is well explained by uncompensated topography (mainly spreading topography). For the long wavelengths (>200 km) there is no correlation of topography and gravity. In principle this topography is compensated. Residual anomalies comprise the Ridge effect as well as regional anomalies related to depth anomalies. The 50 to 200km band-pass filtered topography and gravity contain relevant information on fracture zones. Models require a base of the crust that parallels the topography rather than a form of regional compensation. For an explanation of this crustal model that has the appearance of frozen in normal faults we have to consider the typical morphology as created in the transform domain. The geophysical processes that cause this morphology are still an object of study.     

Optimum design of a servo-controlled breathing regulator for underwater divers

This article deals with the analysis, synthesis and performance evaluation of the flow and dynamic characteristics of the new class of servo-controlled breathing regulators for underwater divers.Emphasis on such a class of regulators has been stimulated by their tremendous potential in extending the dive depth and duration because they reduce the diver breathing effort to a great extent. This would eliminate the unnecessary exhaustion of the diver under such extreme diving conditions and accordingly improve his work efficiency underwater.The study aims at developing rational design procedures and guides that would enable the regulator designers to select the optimal design parameters of this class of regulators. Such design guides are based on the analysis of the flow and dynamic characteristics of the servo-controlled regulator as well as the basic principle of the theory of optimum control.The study presents also experimental evaluation techniques of the dynamic characteristics of this class of regulators in order to provide common quantitative means for comparison with the conventional regulator designs.The presented results emphasize the merits and the potential of the servo-controlled regulators as essential tools of supporting the life of divers underwater.     

A locking-compass for in situ sample orientation

A mechanically-actuated locking-compass was designed for mounting on corers to record equipment orientation during the sampling process, thereby providing magnetic orientation data on the recovered deep-sea core. Locking occurs upon impact by the corer with the sea-floor; after retrieval, the device is easily unlocked and reset for another station. Compass construction makes use of commercially available parts, requires no welding and little machining, and thus allows inexpensive and easy assembly at sea.     

Petroleum hydrocarbons in sediments of Southampton water estuary

The sediments of Southampton Water were analysed for petroleum hydrocarbons to determine the fate of petrochemical refinery waste in the estuary. Much of the petroleum hydrocarbons appears to be removed by adsorption onto estuarine sediments close to source. Surface sediment concentrations range from 3·1mg/g dry weight near a refinery to 0·5 mg/g dry weight at locations distant from the refinery.The absence of any change with depth in total hydrocarbon concentrations from some sediment cores and the presence of distinct ‘oil’ horizons in others suggests that mixing of sediments in the area is very random. Sedimentation rates in areas where a distinct oil horizon was observed ranged from 1 to 3cm a year.     

Ocean bottom refraction seismograph (OBRS)

This paper describes a pop-up ocean bottom seismograph designed primarily for refraction surveys both on the continental shelf and in deep sea. Its development is the extension of our system based on seismic detectors located on the sea floor with radio transmission of seismic signals and used for seismic refraction studies on the continental shelf. The seismic detectors (vertical geophone or hydrophone and two orthogonally mounted horizontal geophones) are located outside of the pressure vessel on the main frame. Optionally, the seismic sensors may be decoupled from the main frame assembly. This decoupling is performed by a mobile arm positioning the separate three component sensor package on the sea floor.Contribution No. 455 of the Département Scientifique, Centre Océanologique de Bretagne.     

Optimization of an ocean thermal energy conversion system

The optimum performance of a simple Rankine cycle ocean thermal energy conversion plant is investigated analytically. It is shown that the ratio of maximum net power output to heat exchanger surface area varies as H(Δt − t₀)² where H describes the overall heat transfer properties of the evaporator and condenser, Δt is the temperature difference between the warm and cold sea water supplies, and t₀ is a parameter depending primarily upon the pressure drops across the warm and cold sea water pumping systems. The model is relatively insensitive to the choice of working fluid, although ammonia is used as the illustrative example.