Flow transformations and mud partitioning across submarine fan fringes

Highly efficient sediment gravity flows can bypass mid-fan channels and lobes and deposit significant volumes of sand, mud, and particulate organic matter in outer-fan and basin-plain settings. The Serpukhovian to Bashkirian fill in the Shannon Basin, western Ireland, includes deep-water fan deposits (Ross Sandstone Fm) that gradationally overlie basin-floor shales (Clare Shale Fm). As part of a broader progradational succession, the upward transition from muddy basin floor to sandy fan preserves the stacked deposits of settings present prior to, and outboard of, mid-fan channels and lobes. Three fully cored boreholes and associated wireline data constrain the facies tracts in an 18-km-long panel oriented oblique to original depositional dip. Two distal successions dominated by hybrid event beds (HEBs) are recognized, separated by a prominent condensed section. The lower Cos-heen system includes m-thick, tabular HEBs with prominent linked debrites that pass down dip into much thinner sandstones overlain by sand-speckled mudstone caps that thicken distally before thinning. The latter are interpreted as secondary mudflows released following reconstitution of more thoroughly mixed sections of the up-dip linked debrites. Significant bypass and accumulation of mud by this mechanism helped heal local topography and maintain a relatively flat sea floor, promoting an overall tabular geometry for the deposits of larger volume hybrid flows reaching the distal sector of the basin. The overlying distal Ross system fringe is characterized by very fine- to fine-grained sandstones and is lateral to compensationally stacked lobes farther to the west. It has a progradational (at least initially) stacking pattern, facies transitions developed over shorter length scales, and includes outsized event beds, but these are thinner than those in the Cosheen system. Common banding and evidence for turbulence suppression by dispersed clay rather than entrained mud clasts indicate that these were transitional flows. In this case, event beds are inferred to taper distally, with significant mud emplaced by plug flow retained as caps to sandy event beds rather than bypassing down-dip. Different flow transformation mechanisms thus impacted how mud was partitioned across the fringe of the two systems, and this influenced bed geometries, larger scale bed stacking patterns, and stratigraphy. Whereas the flow-efficiency concept stresses the ability of flows to carry sand in a basinward direction, it is also imperative to consider the variable efficiency of mud transport given the operation of clay-induced flow transformations. These can either promote bypass or trigger premature fallout of mud, with implications for how systems fill accommodation, bed-scale facies transitions, and the burial and preservation of particulate organic carbon fractionated along with the clay in deep-water system fringes.Science Foundation IrelandGeological Survey Ireland (GSI) Griffith Geoscience AwardEquinor AS

Ammonoid biostratigraphy of the Shannon Basin, western Ireland

THESIS 11042This study concerns ammonoid faunas from a classic turbidite succession, the Ross Sandstone Formation [Serpukhovian-Bashkirian) of the Shannon Basin, western Ireland. In addition to coastal exposures, a set of 12 behind-outcrop wells w e r e examined and sampled for biostratigraphy. More than 3,000 fossil specimens from the Clare Shale Formation and Ross Sandstone Formation were investigated. Given current lack of published information on the taxonomy of crushed ammonoid material, new systematic data on 14 Serpukhovian-Bashkirian ammonoids for which ontogenetic information was previously incomplete or lacking are presented. This information furthers knowledge of ammonoid ontogeny and also leads to more confident identification of ammonoids preserved as flattened external moulds. Marine fossils were commonly reported as confined to thin ammonoid-rich layers ("marine bands") bounded by barren strata, leading to a suggestion, based on examples from the Pennines, that fossil occurrence may be controlled by variations in salinity. While ammonoids are indeed concentrated in laterally extensive black shale bands, taken to represent intervals of sediment starvation, several new ammonoid-bearing horizons have been found in between the "marine bands" in the Shannon Basin, which are therefore better referred to as "condensed sections" or "ammonoid bands". The presence of ammonoids at various intervals outside the condensed sections is good evidence for normal marine salinity in the Ross Sands tone and associated Clare Shale Formation. The presence of normal marine faunas outside the traditional "marine bands" suggests that salinity values of the Shannon Basin and, by implication, other deep-water basins may well have been normal between periods of sediment starvation. Early biostratigraphic work in the basin recognized the presence of four ammonoid bands within the Ross Sandstone Formation. During the course of this study and in conjunction with research at University College Dublin, ten ammonoid-rich horizons [including eight condensed sections) have been identified within the Ross Sandstone. Faunal assemblages from the five main highly-condensed sections in the Ross Sandstone Formation are described in detail in this study, which is also the first to present details of abundance and pro portion of ammonoid taxa at localities within the Ross Sandstone Formation. These new biostratigraphic data, coupled with the lithostratigraphical correlations, provide the most detailed dataset for the Ross Sandstone Formation to date, also allowing biostratigraphy to be cross-checked against lithostratigraphical correlations. Overall, biostratigraphy was not as high-resolution as one might have hoped, in the sense that statistical analysis of the faunal assemblages does not always confirm that bands which are known to correlate by physical means are indeed indistinguishable. While some assemblages in condensed sections proved to be globally distinctive, most were not, and some were only locally distinctive; therefore most bands in the Ross Sandstone Formation cannot be confidently linked to a given ammonoid band in the Western European framework. This puts the validity of ammonoid-bearing condensed sections both in intrabasinal and extrabasinal correlation into question

“Following the Science”: In Search of Evidence-Based Policy for Indoor Air Pollution from Radon in Ireland

Radon, a naturally occurring radioactive gas that can accumulate inside dwellings, represents the second biggest cause of lung cancer globally. In Ireland, radon is linked to approximately 300 lung cancer cases every year, equating to 12% of all lung cancer deaths. Despite the health risks posed by radon air pollution, Ireland lacks well-defined and universally applicable air pollution-related public health policies. Through purposive literature sampling, we critically examine the case of indoor radon policy development in Ireland. Specifically, we analyse the evidence-based policymaking process relating to indoor radon pollution from three different knowledge dimensions, namely political, scientific, and practical knowledge. In doing so, we identify various challenges inherent to pollution-related public policymaking. We highlight the difficulties of balancing and integrating information from multiple disciplines and perspectives and argue that input from multiple scientific areas is crucial, but can only be achieved through continued, dialogic communication between stakeholders. On the basis of our analysis, we suggest that a transdisciplinary perspective, defined as a holistic approach which subordinates disciplines and looks at the dynamics of whole systems, will allow evidence-based policymaking to be effective. We end with recommendations for evidence-based policymaking when it comes to public health hazards such as radon, which are applicable to sustainable air pollution management beyond Ireland