The importance of missing strain in deep water fold and thrust belts

Deep water fold and thrust belts (DWFTBs) are sedimentary wedges that accommodate plate-scale deformation on both active and passive continental margins. Internally, these wedges consist of individual structures that strongly influence sediment dispersal, bathymetry and fluid migration. Most DWFTB studies investigate basin- and intra-wedge- scale processes using seismic reflection profiles, yet are inherently limited by seismic resolution. Of critical importance is strain distribution and its accommodation on discrete faults compared to distributed deformation. Recent studies have considered strain distribution by investigating regional reflection DWFTBs profiles within coupled systems, which contain down-dip compression and up-dip extension. There is broad agreement of a mis-balance in compression versus extension, with ∼5% excess in the latter associated with horizontal compaction, yet this remains unproven. Using two exceptionally well exposed outcrops in the Spanish Pyrenees we consider deformation of DWFTB at a scale comparable to, and beyond, seismic resolution for the first time. By coupling outcrop observations (decametre to hectometre scale) with a re-evaluation of seismic profiles from the Orange Basin, South Africa, which contains one of the best imaged DWFTBs globally, we provide a unique insight into the deformation from metre to margin scale. Our observations reveal hitherto unrecognised second order structures that account for the majority of the previously recognised missing strain. This re-evaluation implies that ∼5% missing strain should be accounted for in all DWFTBs, therefore existing studies using restorations of the sediment wedge will have underestimated crustal shortening in active margins, or sedimentary shortening in gravity driven systems by this amount. In contrast to previous studies, our observations imply that the majority of this strain is accommodated on discrete fault surfaces and this can explain the occurrence and location of a range of intra-wedge processes that are intimately linked to structures including sediment dispersal, fluid migration pathways and reservoir compartmentalisation

Impacts of anthropogenic noise on marine life: Publication patterns, new discoveries, and future directions in research and management

Anthropogenic underwater noise is now recognized as a world-wide problem, and recent studies have shown a broad range of negative effects in a variety of taxa. Underwater noise from shipping is increasingly recognized as a significant and pervasive pollutant with the potential to impact marine ecosystems on a global scale. We reviewed six regional case studies as examples of recent research and management activities relating to ocean noise in a variety of taxonomic groups, locations, and approaches. However, as no six projects could ever cover all taxa, sites and noise sources, a brief bibliometric analysis places these case studies into the broader historical and topical context of the peer-reviewed ocean noise literature as a whole. The case studies highlighted emerging knowledge of impacts, including the ways that non-injurious effects can still accumulate at the population level, and detailed approaches to guide ocean noise management. They build a compelling case that a number of anthropogenic noise types can affect a variety of marine taxa. Meanwhile, the bibliometric analyses revealed an increasing diversity of ocean noise topics covered and journal outlets since the 1940s. This could be seen in terms of both the expansion of the literature from more physical interests to ecological impacts of noise, management and policy, and consideration of a widening range of taxa. However, if our scientific knowledge base is ever to get ahead of the curve of rapid industrialization of the ocean, we are going to have to identify naïve populations and relatively pristine seas, and construct mechanistic models, so that we can predict impacts before they occur, and guide effective mitigation for the most vulnerable populations