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Shelf-edge deltas (SEDs) forming during periods of relative sea level fall and lowstand are generally efficient in transferring sediments to the slope and basins, and their identification in subsurface data is often considered a good indication of coeval development of slope and basin-floor turbidite reservoirs. This study investigates the seismic stratigraphic evolution of a forced-regressive and normal regressive shelf-edge delta (Bonaparte SED) that accumulated on the edge of the NW Australian margin during the late Quaternary. High resolution 2D and 3D reflection seismic data allow reconstruction of the main episodes of delta progradation and understanding of the extrinsic and intrinsic controls on their deposition. The lack of a significant turbidite system forming off the shelf-edge delta throughout the Quaternary is a striking feature of the Bonaparte SED. Instead, slope sedimentation is dominated by the accumulation of plume-derived mud belts and their reworking through mass-transport processes. Seismic geomorphology permits interpretation of the process regime of the youngest shelf-edge depocentre by applying a new process-based shallow-marine classification scheme to the 3D seismic attribute data. Results suggest either a tide or wave dominated delta with fluvial processes being of tertiary significance. A tide or wave-dominated, fluvial-affected shelf-edge delta classification is consistent with the paleogeographical reconstruction of the margin during the last glacial maximum (ca. 25 ka BP). The comparison of this mixed-process shelf-edge delta and starved slope system with a fluvial-dominated counterpart with significant sandy slope deposits emphasizes the potential of assessing the process regime of shelf-edge deltas as a rapid, first approach for predicting the presence or absence of coeval slope and basin-floor reservoirs. [ABSTRACT FROM AUTHOR]

Abstract: Increasing emphasis is being placed on low mastectomy rates. Our objective was to investigate factors influencing rates of mastectomy and breast conserving surgery. A group of 171 patients (27%) who could have had breast conserving surgery (BCS) but chose mastectomy was identified as well as all patients who underwent BCS over a 6 year period. A questionnaire asking patient's attitudes to factors which could influence their choice of operation was compiled and sent to this study group. Results showed surgical advice to be the most important factor, with significantly more influence in BCS patients. No significant difference was found in distance to treatment between the groups. Shorter duration radiotherapy would have made 47% of mastectomy patients more likely to accept BCS. BCS rates are a poor measure of quality of patient care. More emphasis should be put on choices offered to patients rather than overall uptake of a specific choice. [Copyright &y& Elsevier]

The aim of this paper is to present a methodology to rapidly evaluate the strain energy density (SED) and the notch stress intensity factor (NSIF) of a wide range of sharp V-notched SEN(T) specimens. A dislocation based method is used to find the solution of the boundary value problem. As a post-processing stage, computation of the local strain energy density over a circular sector surrounding the point of singularity is performed. NSIFs are then assessed bymeans of the strain energy approach (SEA) for several opening angles and specimen widths. Comparisons of local strain energy results with full-term solutions obtained by finite element analysis (FEA) are provided in order to validate the method and to establish the limitations of the NSIF approach for the case under consideration. The procedure presented in this work is shown to provide accurate results for the range of notch depth to specimen width ratios a/L b 0.4. The validity of the single-parameter characterisation when the boundary effect becomes significant is also discussed. [ABSTRACT FROM AUTHOR]

A major challenge in sequence stratigraphy is objectively identifying stratigraphic surfaces and sequences across multiple scales of observation. Identification is commonly dependent on the resolution of the data used (i.e., seismic vs. well data), its dimension (i.e., 1D vs. 2D vs. 3D) or the criteria chosen to select sequence boundaries. Through shelf-edge trajectory analysis, the clinothem (i.e., highest order seismic sequence identified on seismic data) can constitute the elementary building block of an observation-based and data-driven quantitative workflow to develop sequence stratigraphic frameworks across different orders and ranks of hierarchy. Here, we use high-quality 3D seismic data to interpret a Late Tithonian–Early Cretaceous shelf margin, the Lower Barrow Group (LBG), developed in the Northern Carnarvon Basin on the North West Shelf of Australia. Based on full-volume seismic interpretation techniques that integrate the 3D variability of the data when identifying seismic unconformities, a high-resolution seismic stratigraphic framework was built (73 interpreted clinothems with an average time duration of ~63,000 yrs). The computation of high-frequency shelf-edge trajectory angle (T se) curves on selected seismic cross-sections is used to objectively pick sequence stratigraphic surfaces based on the accommodation succession method, thereby highlighting small changes in trajectory and proposing a method reproducible by interpreters based on the same quantitative data. Within the D. lobispinosum interval (142.3–140.9 Ma), the definition of stratigraphic sequences and composite stratigraphic sequences through this workflow is used to discriminate the controls at high and low temporal frequency on the vertical and lateral variability (which is here quantified) of this shelf-slope-basin system. The results show that the high-frequency interplay between short-term glacio-eustasy (i.e., Milankovitch eccentricity cycles of ~100,000 yrs) and sediment supply (locus of fluvial input along the margin) impacted the three-dimensional stratigraphic architecture of the LBG. In contrast, tectonic subsidence had a significant impact on the stratigraphic architecture of the LBG within the main depocentre at lower temporal frequency by overprinting the eustatic signal and accelerating/decelerating the rates of accommodation creation. However, identification of long-term glacio-eustatic Milankovitch cycles (~400,000 yrs) outside the main depocentre, where the rates of accommodation creation due to rift-related subsidence are moderate, also suggests low-frequency eustatic control. Therefore, the vertical and lateral variability of the LBG results from variations in sediment supply and subsidence regime under local (i.e., process regime, currents), regional (i.e., tectonics) and global (i.e., eustasy, climate) forcing parameters interplaying across timescales. In contrast to standard sequence stratigraphic workflows that are based on model-dependent choices to select sequence boundaries, quantitative 3D seismic stratigraphy constitutes an improved method to interpret 3D seismic data in shelf-margin depositional systems within a sequence stratigraphic framework, which provides an observation-based and model-independent tool allowing the definition of stratigraphic sequences with results that are reproducible across multiple stratigraphers. This work highlights the need for developing new sequence stratigraphic tools and methods that integrate the 4D variability of depositional systems and moves beyond the two-dimensionality inherent to current sequence stratigraphic methods. Quantitative 3D seismic stratigraphy represents a first step towards the creation of 3D sequence stratigraphic workflows that could improve the prediction of stratigraphic patterns and facies relationships (source, reservoir, seal distribution) across shelf margins. • A high-resolution seismic stratigraphic framework was built using 3D seismic data. • Shelf-edge trajectory angle curves are used to pick sequence stratigraphic surfaces. • Lateral and vertical variability of the clinothems is quantified. • Controls are identified at high and low temporal frequency. • Quantitative 3D seismic stratigraphy represents a first step towards 3D sequence stratigraphy. [ABSTRACT FROM AUTHOR]