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Watton T.J.,Durham University | Watton T.J.,Statoil | Wright K.A.,DONG Energy | Jerram D.A.,DougalEARTH Ltd. | And 2 more authors.
AAPG Bulletin | Year: 2014

Offshore sequences of volcaniclastic rocks (such as hyaloclastite deposits) are poorly understood in terms of their rock properties and their response to compaction and burial. As petroleum exploration targets offshore volcanic rifted margins worldwide, understanding of volcanic rock properties becomes important both in terms of drilling and how the rocks may behave as seals, reservoirs, or permeability pathways. The Hawaiian Scientific Drilling Project phase II in 2001 obtained a 3 km-(2-mi)-long core of volcanic and volcaniclastic rocks that records the emergence of the largest of the Hawaiian islands. Core recovery of 2945 m (9662 ft) resulted in an unparalleled data set of volcanic and volcaniclastic rocks. Detailed logging, optical petrology, and major element analysis of two sections at depths 1831-1870 and 2530-2597 m (6007-6135 and 8300-8520 ft) are compared to recovered petrophysical logs (gamma ray, resistivity, and P-wave velocity). This study concludes deviation in petrophysical properties does not seem to correlate to changes in grain size or clast sorting, but instead correlates with alteration type (zeolite component) and bulk mineralogy (total olivine phenocryst percentage component). These data sets are important in helping to calibrate well-log responses through hyaloclastite intervals in areas of active petroleum exploration such as the North Atlantic (e.g., Faroe-Shetland Basin, United Kingdom, and Faroe Islands, the Norwegian margin and South Atlantic margins bordering Brazil and Angola). © 2014. The American Association of Petroleum Geologists. All rights reserved. Source

Nelson C.E.,Cairn Energy Plc | Jerram D.A.,University of Oslo | Jerram D.A.,DougalEARTH Ltd. | Jerram D.A.,Queensland University of Technology | And 3 more authors.
Marine and Petroleum Geology | Year: 2015

New data are presented on the offshore part of the West Greenland volcanic succession, part of the North Atlantic Igneous Province located in southern Baffin Bay. The data were obtained from the Delta-1 hydrocarbon exploration well, drilled by Cairn Energy in 2011. Wireline log data were collected over the drilled section, providing information on the physical volcanology of the volcanic succession, and 23 sidewall cores were analysed for their geochemical composition. The well encountered 65 lava flows with a well-developed core and crust signature, typical for sub-aerial eruptions. Major and trace element data showed a good correlation with parts of the succession onshore West Greenland. The XRF major and trace element data allowed careful picking of samples for 40Ar/39Ar dating, and the main part of the sequence was found to be early Eocene in age. This coincides with the second main phase of volcanism in onshore West Greenland and is likely to be linked to the change in the tectonic regime in Baffin Bay at this time. This finding substantially expands the area of West Greenland affected by volcanism during the Eocene. © 2015 Elsevier Ltd. Source

Wright K.A.,Durham University | Davies R.J.,Durham University | Jerram D.A.,DougalEARTH Ltd. | Morris J.,Statoil | Fletcher R.,Statoil
Basin Research | Year: 2012

Detailed seismic stratigraphic analysis of 2D seismic data over the Faroe-Shetland Escarpment has identified 13 seismic reflection units that record lava-fed delta deposition during discrete periods of volcanism. Deposition was dominated by progradation, during which the time shoreline migrated a maximum distance of ~44km in an ESE direction. Localised collapse of the delta front followed the end of progradation, as a decrease in volcanic activity left the delta unstable. Comparison with modern lava-fed delta systems on Hawaii suggests that syn-volcanic subsidence is a potential mechanism for apparent relative sea level rise and creation of new accommodation space during lava-fed delta deposition. After the main phase of progradation, retrogradation of the delta occurred during a basinwide syn-volcanic relative sea level rise where the shoreline migrated a maximum distance of ~75km in a NNW direction. This rise in relative sea level was of the order of 175-200m, and was followed by the progradation of smaller, perched lava-fed deltas into the newly created accommodation space. Active delta deposition and the emplacement of lava flows feeding the delta front lasted ~2600 years, although the total duration of the lava-fed delta system, including pauses between eruptions, may have been much longer. © 2011 The Authors. Basin Research © 2011 Blackwell Publishing Ltd, European Association of Geoscientists & Engineers and International Association of Sedimentologists. Source

Cross J.K.,Royal Holloway, University of London | Roberge J.,National Polytechnic Institute of Mexico | Jerram D.A.,DougalEARTH Ltd.
Journal of Volcanology and Geothermal Research | Year: 2012

The explosive activity of Popocatépetl Volcano is a threat to the surrounding densely populated areas and it is therefore important to recognize indicators of change in eruptive style (explosive to dome building) within a short period of time. In this study we present results of vesicle size distributions (VSDs) and compositional analysis of matrix glass from juvenile clasts from five of the main plinian eruptions of Popocatépetl (ca 23-1.2. ka), the 2001 small eruption during partial dome collapse and four eruptions during 1997 (May 11th and June 14th, 15th and 30th). Major element analysis of matrix glass (WDS-EPMA) allows the estimation of the depth from which the erupted magma went into disequilibrium (between crystals and melt), by calculating the equilibrium pressure using the quartz-albite-orthoclase ternary system of Blundy and Cashman (2001). Quantitative interpretation of texture in juvenile (pumice or scoria) clasts via VSD analysis using CSD software was used to link physical changes experienced by magma during ascent, with conditions responsible for eruptions. The extent and style of vesiculation in juvenile clasts is also related to eruption style and duration and has specifically allowed the recognition of changes in vesicular texture that represent variations from explosive to dome building activity (Mangan and Sisson, 2000; Adams et al., 2006). This study highlights a more complicated story in terms of magma storage, than that previously accepted for the Popocatépetl volcanic system and is an important contribution to ongoing research at the volcano. © 2012 Elsevier B.V. Source

Jones M.T.,University of Oslo | Jerram D.A.,University of Oslo | Jerram D.A.,DougalEARTH Ltd. | Jerram D.A.,Queensland University of Technology | And 2 more authors.
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2016

The correlation between large igneous provinces (LIPs), extinction events, and rapid climate change suggests that volcanism can have a detrimental impact on Earth surface conditions. Changes in atmospheric and ocean chemistry, particularly the climate-sensitive carbon and sulphur cycles, are among the most probable processes for inducing global environmental stress. However, the interactions and feedbacks between volcanism and these cycles are numerous and complex, making the characterisation of the response to a LIP challenging. Here we summarise the sources and sinks of carbon and sulphur from large scale volcanism and magmatism using information from modern and ancient systems. For the sources, we review the current understanding of volcanic emissions, and explore the relative contributions and importance of magma-derived degassing versus volatile release from sediments affected by igneous intrusions and lava. In addition, we explore the various ways in which LIPs can reduce atmospheric concentrations of these same elements. The relative influences of each source and sink are in part determined by the mode of LIP emplacement and eruption style, along with the subsequent timescales of such effects. We focus on a few key examples, including the Siberian Traps, the Paraná-Etendeka, and the Central Atlantic Magmatic Province (CAMP), to demonstrate how the environmental impact can vary considerably with differing modes of emplacement, LIP duration, and eruption styles. In particular, we show that the host rocks can have a dominant role as a source or sink of emissions, depending on the lithologies affected by the LIP emplacement. © 2015 Elsevier B.V. Source

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