Legacy product - no abstract available

Legacy product - no abstract available

Legacy product - no abstract available

Recently acquired seismic reflection and gravity potential field data was used to investigate the distribution of volcanic facies and large scale structural architecture of the Mentelle Basin, located on the southwestern margin of Australia. Isochron and seismic facies maps were used to identify the thickness and distribution of volcanic facies. These maps show that volcanism is generally confined to the Western Mentelle Basin, with two distinct areas of thick volcanic deposits occurring to the centre and north of the area. Two and three dimensional gravity forward models were created in IGMAS+. Two dimensional gravity modelling shows that the crust is extremely thin in the Western Mentelle (c.10km), associated with two mantle highs observed to the north and centre of the Western Mentelle. The crust thickens from the Eastern Mentelle (>20km) towards mainland Australia and the Naturaliste Plateau. The two modelled mantle highs coincide with the two seismically defined areas of thick volcanic deposits. Analogue models indicate that rift related volcanism is generally confined to the locus of extension where the pressure is lowest. Thus results of gravity modelling and seismic interpretation in this study indicate that Jurassic - Cretaceous extension was focussed in the Western Mentelle. This conclusion conforms to models of rift related basin formation, where the flanks of the basin are uplifted; an angular unconformity in the Eastern Mentelle may support the occurrence of rift-flank uplift in this area as a result of asthenospheric rise and rifting while the deposition of volcanic material was focussed in the Western Mentelle.

Large atmospheric acoustic sources such as: volcanic eruptions, bolides (terminating meteorite explosions), the ocean surface, chemical and nuclear detonations generate copious quantities of infrasound (low frequency sound) that can propagate several thousand kilometres. Using the appropriate recording equipment, infrasound from various sources can be detected and used to infer certain knowledge about the source mechanism or atmosphere through which it travelled. Each year an Infrasound Technology Workshop is organised to provide researchers from various international institutions the opportunity to meet with colleagues and present current research results in an informal setting. The Infrasound Technology Workshop 2004 was hosted by Geoscience Australia in Hobart, Tasmania from 29 November to 3 December 2004. The Workshop was organised in cooperation with the Provisional Technical Secretariat of the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) in Vienna. Listed below is the complete list of abstracts submitted to the special Volcano infrasound session in author's surname order. General Infrasound sessions were also held at the Workshop, see Geocat #69548 to view the 27 submitted abstracts.

Legacy product - no abstract available

Legacy product - no abstract available

This report deals with the volcanic activity at Tuluman Volcano in St .Andrew Strait, 25 miles south of Lorengau in the Admiralty group. In the first of the three papers, which constitute the report, a description is given of the activity from June 1953, when the eruption began, to the end of July-1954. Part II describes further submarine activity in October and November 1954, and the condition of the active centres at that time. In Part III a more detailed description of the eruptive activity is given and the eruption and the associated phenomena are reviewed at some length. Volcanic activity in the St. Andrew Strait has originated from at least five, separate centres, from one of which another cone has been formed by a branching-off from the main conduit. As a result, three islands, two of which have been subsequently joined, have been built up above sea level. The name Tuluman Islands is proposed for these islands, and individual cones are numbered according to the chronological order in which they have been formed. The geographical position of the Tuluman Islands and their topography are also discussed.

Legacy product - no abstract available

Understanding the hydrology of cold seep environments is crucial to perform accurate estimates of fluid and chemical fluxes at sedimentary wedges. Shallow convection processes may affect fluid flux estimates and could favor the destabilization of gas hydrate accumulations, increasing the sediment-ocean methane flux. Evidence for the occurrence of convection at cold seeps, however, is still limited. We use the concentration of 14C (D14C) in carbonate crusts formed at cold seeps of the eastern Mediterranean Sea as a tracer for convective recirculation of seawater-derived fluids. A numerical model is applied to investigate the controls on 14C incorporation in cold seep carbonates. Our simulations show that increased amounts of CH4 in the expelled fluids result in elevated crust D14C, while high Ca2+ and HCO3 concentrations produce the opposite effect. Convection is the only transport process that can significantly increase crust D14C. Advection, bioirrigation, eddy diffusion and bioturbation instead, have little effect on, or produce a decrease of, crust D14C. In addition, the presence of old or modern carbon (MC) in host sediments prior to cementation and the 14C-decay associated to the time needed to form the crust contribute in defining the D14C of carbonate crusts. We then use the model to reproduce the 14C content of the eastern Mediterranean Sea crusts to constrain the chemical and hydrological conditions that led to their formation. Some crusts contain relatively low amounts of 14C (-945.0<D14C - <-930.2) which, assuming no ageing after crust formation, can be reproduced without considering convection. . Other crusts from two sites (the Amsterdam and Napoli mud volcanoes), instead, have a very high 14C-content (-899.0<D14C - <-838.4) which can only be reproduced by the model if convection mixes deep fluids with seawater.