Mechanisms, distribution, and subsurface implications of clastic injectites

Understanding how clastic injectites form is important, as they are increasingly being recognised as significant components of sedimentary basin-fills, but are not predicted by standard sedimentary facies models. This study focuses on exhumed examples of injectites from the Karoo Basin, South Africa, and utilises a multidisciplinary approach to investigate clastic injectites across a variety of scales. Small-scale analysis of injectites allows a classification of fracture patterns preserved on sill and dyke margins. These are used to interpret propagation direction through brittle, fine grained sediments under a laminar flow regime at depth in closed fracture networks. In contrast, shallow injectites, where they do not extrude, are identified by; fewer dykes, less stratigraphy crosscut, lower volume of injected material, and in some cases burrows on injectite margins—suggesting exploitation of injectite networks close to the surface. These insights are applied to larger-scale (100s m to km) analysis, where extensive outcrop and well constrained paleogeography permits the injectite geometry to be related to parent sandstone facies and architecture. The influence of fluid flow pre-, syn- and post-injection is investigated across multiple scales. A model for the predictive distribution of injectites is proposed, which highlights the close association of basin-floor stratigraphic traps and sub-seismic clastic injectites.The outcrop data permits construction of forward seismic models demonstrate injectite architecture is scale invariant, which supports the use of outcrop-scale data in seismic-scale interpretations. The integration of outcrop panels, well log data, forward seismic models and subsurface seismic sections has aided the identification of injectites in the subsurface and therefore the ability to discriminate between clastic injectites and parent sandbodies. The increased predictability in the location and character of injectites allows subsurface uncertainty in the impact of clastic injectites on hydrocarbon reservoirs to be reduced

Introduction : Subsurface sand remobilization and injection

Acknowledgement Thanks are due for informal information provided on the Nanaimo, Tierra del Fuego and Neoquen basins (David Hodgson), the East Carpathian Fold Belt (Alexandra Tamas) and the Paraná Basin (Gus- tavo Zvirtes). Funding This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.Peer reviewedPublisher PD

An Iron Age and early Roman farmstead at Calvestone Road, Cawston, near Rugby: excavations in 2012

A programme of archaeological investigation was undertaken by Cotswold Archaeology (CA) prior to housing development to the east of Calvestone Road, Cawston, on the outskirts of Rugby. The work comprised an archaeological excavation over three areas followed by a watching brief on parts of the site not subject to excavation. In Area 1 lay an Iron Age subrectangular enclosure whose ditch had been re-cut on at least three occasions. The enclosure contained evidence for an Iron Age farmstead, including a possible roundhouse. Areas 2 and 3 also revealed evidence of occupation during the Iron Age. Later, in the 1st century AD, the site was remodelled with the laying out of a series of larger enclosures and the development of a trackway. The site was abandoned during the Roman period with no evidence for continued occupation beyond c AD 200. Medieval and post-medieval furrows indicate that later the area was laid down to arable.This report presents the results of the excavation and places them within the context of settlement, the economy and the environment of the Iron Age and Roman periods. The likely function of each feature and structure encountered is considered and compared with other Iron Age and Roman sites

Southern Ocean humpback whale trophic ecology. I. Combining multiple stable isotope methods elucidates diet, trophic position and foraging areas

Southern Ocean humpback whales Megaptera novaeangliae are capital breeders, breeding in the warm tropics/subtropics in the winter and migrating to nutrient-rich Antarctic feeding grounds in the summer. The classic feeding model is for the species to fast while migrating and breeding, surviving on blubber energy stores. Whilst northern hemisphere humpback whales are generalists, southern hemisphere counterparts are perceived as krill specialists, but for many populations, uncertainties remain regarding their diet and preferred feeding locations. This study used bulk and compound-specific stable isotope analyses and isoscape-based feeding location assignments to assess the diet, trophic ecology and likely feeding areas of humpback whales sampled in the Ross Sea region and around the Balleny Islands. Sampled whales had a mixed diet of plankton, krill and fish, similar to the diet of northern hemisphere humpback whales. Proportions of fish consumed varied but were often high (2-60%), thus challenging the widely held paradigm of Southern Ocean humpback whales being exclusive krill feeders. These whales had lower δ15N values and trophic position estimates than their northern hemisphere counterparts, likely due to lower Southern Ocean baseline δ15N surface water values and a lower percentage consumption of fish, respectively. Most whales fed in the Ross Sea shelf/slope and Balleny Islands high-productivity regions, but some isotopically distinct whales (mostly males) fed at higher trophic levels either around the Balleny Islands and frontal upwelling areas to the north, or en route to Antarctica in temperate waters off southern Australia and New Zealand. These results support other observations of humpback whales feeding during migration, highlighting the species' dietary plasticity, which may increase their foraging and breeding success and provide them with greater resilience to anthropogenically mediated ecological change. This study highlights the importance of combining in situ field data with regional-scale isoscapes to reliably assess trophic structure and animal feeding locations, and to better inform ecosystem conservation and management of marine protected areas.</p