34 research outputs found
Onshore carboniferous basins : third review report
focussed on achieving a better understanding of the Bowland Shale in northern England. The broad
aim is to understand the geological variability of the formation from a basin- through to microscale,
and assess the impact of variability on hydrocarbon generation, storage and production (for
example, the co-incidence or otherwise of factors including organic content and kerogen type;
mineralogy; and engineering behaviour).
This report is the third summary report describing activities of the consortium, covering the period
October 2015 – June 2016. A series of 3 inter-related work packages are designed to improve
understanding of the Bowland Shale of northern England. The original numbering of these is
retained to allow continuity between previous progress reports. Specifically, these work packages
address:
1. Work Package 1,2: Basin analysis of the Pennine Basin; Characterization of shale facies;
2. Work Package 3: Development of chemical stratigraphies through prospective parts of the
stratigraphic column;
3. Work Package 4: Hydromechanical behaviour of shales.
Two work packages outside the consortium are also considered, namely
4. Retrieval of new materials to test
5. Reprocessing of 3D seismic data to assess rock properties
Descriptions of previous activities have been released, covering the period July 2014 to March
2015 (Hough et al., 2015a), and the period April 2015 to September 2015 (Hough et al., 2015b).
The consortium currently has 4 sponsors who each contribute £25 000 per year; BGS contributes
around £200 000 annually, which results in an annual budget of approximately £300 000. The
consortium is planned to last 3 years initially, and started in July 2014 with a scheduled end date
of June 2017
A snapshot of the oldest active galactic nuclei feedback phases
Active galactic nuclei inject large amounts of energy into their host galaxies and surrounding environment, shaping their properties and evolution1,2. In particular, active-galactic-nuclei jets inflate cosmic-ray lobes, which can rise buoyantly as light ‘bubbles’ in the surrounding medium3, displacing and heating the encountered thermal gas and thus halting its spontaneous cooling. These bubbles have been identified in a wide range of systems4,5. However, due to the short synchrotron lifetime of electrons, the most advanced phases of their evolution have remained observationally unconstrained, preventing us from fully understand their coupling with the external medium, and thus active galactic nuclei feedback. Simple subsonic hydrodynamic models6,7 predict that the pressure gradients, naturally present around the buoyantly rising bubbles, transform them into toroidal structures, resembling mushroom clouds in a stratified atmosphere. The way and timescales on which these tori will eventually disrupt depend on various factors including magnetic fields and plasma viscosity8,9. Here we report observations below 200 MHz, sensitive to the oldest radio-emitting particles, showing the late evolution of multiple generations of cosmic-ray active-galactic-nuclei bubbles in a galaxy group with unprecedented level of detail. The bubbles’ buoyancy power can efficiently offset the radiative cooling of the intragroup medium. However, the bubbles still have not thoroughly mixed with the thermal gas, after hundreds of million years, probably under the action of magnetic fields