Fluvio-Marine Sediment Partitioning as a Function of Basin Water Depth

Progradational fluvio-deltaic systems tend towards but cannot reach equilibrium, a state in which the longitudinal profile does not change shape and all sediment is bypassed beyond the shoreline. They cannot reach equilibrium because progradation of the shoreline requires aggradation along the longitudinal profile. Therefore progradation provides a negative feedback, unless relative sea level falls at a sufficient rate to cause non-aggradational extension of the longitudinal profile. How closely fluvio-deltaic systems approach equilibrium is dependent on their progradation rate, which is controlled by water depth and downstream allogenic controls, and governs sediment partitioning between the fluvial, deltaic, and marine domains. Here, six analogue models of coastal fluvio-deltaic systems and small prograding shelf margins are examined to better understand the effect of water depth, subsidence, and relative sea-level variations upon longitudinal patterns of sediment partitioning and grain-size distribution that eventually determine large-scale stratigraphic architecture. Fluvio-deltaic systems prograding in relatively deep-water environments are characterized by relatively low progradation rates compared to shallow-water systems. This allows these deeper water systems to approach equilibrium more closely, enabling them to construct less concave and steeper longitudinal profiles that provide low accommodation to fluvial systems. Glacio-eustatic sea-level variations and subsidence modulate the effects of water depth on the longitudinal profile. Systems are closest to equilibrium during falling relative sea level and early lowstand, resulting in efficient sediment transport towards the shoreline at those times. Additionally, the strength of the response to relative sea-level fall differs dependent on water depth. In systems prograding into deep water, relative sea-level fall causes higher sediment bypass rates and generates significantly stronger erosion than in shallow-water systems, which increases the probability of incised-valley formation. Water depth in the receiving basin thus forms a first-order control on the sediment partitioning along the longitudinal profile of fluvio-deltaic systems and the shelf clinoform style. It also forms a control on the availability of sand-grade sediment at the shoreline that can potentially be remobilized and redistributed into deeper marine environments. Key findings are subsequently applied to literature of selected shelf clinoform successions

The detached self: Investigating the effect of depersonalisation on self-bias in the visual remapping of touch.

There is a growing consensus that our most fundamental sense of self is structured by the ongoing integration of sensory and motor information related to our own body. Depersonalisation (DP) is an intriguing form of altered subjective experience in which people report feelings of unreality and detachment from their sense of self. The current study used the visual remapping of touch (VRT) paradigm to explore self-bias in visual–tactile integration in non-clinical participants reporting high and low levels of depersonalisation experiences. We found that the high-DP group showed an increased overall VRT effect but a no-self-face bias, instead showing a greater VRT effect when observing the face of another person. In addition, across all participants, self-bias was negatively predicted by the occurrence of anomalous body experiences. These results indicate disrupted integration of tactile and visual representations of the bodily self in those experiencing high levels of DP and provide greater understanding of how disruptions in multisensory perception of the self may underlie the phenomenology of depersonalisation

The role of self-regulation in predicting sleep hygiene in university students

University students have poor sleep hygiene, leading to poorer health. Facets of self-regulation such as planning, behavioural inhibition, cognitive flexibility and working memory were explored in relation to three sleep hygiene behaviours: Avoiding stress or anxiety before bed, avoiding going to bed hungry or thirsty, and making the bedroom restful. One hundred and thirty-seven participants took part in an Internet-based survey over two time points separated by a period of two weeks. Only cognitive flexibility and behavioural inhibition correlated with sleep hygiene. Cognitive flexibility significantly predicted an aspect of sleep hygiene after controlling for past behaviour. However, when past behaviour was controlled for, behavioural inhibition no longer predicted sleep hygiene. Thus, cognitive flexibility may play a role in explaining sleep hygiene; however, behavioural inhibition does not appear as important as previously assumed. Further research could build on this study to determine whether cognitive flexibility can be experimentally improved

Deep CO₂ in the end-Triassic Central Atlantic Magmatic Province

Large Igneous Province eruptions coincide with many major Phanerozoic mass extinctions, suggesting a cause-effect relationship where volcanic degassing triggers global climatic changes. In order to fully understand this relationship, it is necessary to constrain the quantity and type of degassed magmatic volatiles, and to determine the depth of their source and the timing of eruption. Here we present direct evidence of abundant CO2 in basaltic rocks from the end-Triassic Central Atlantic Magmatic Province (CAMP), through investigation of gas exsolution bubbles preserved by melt inclusions. Our results indicate abundance of CO2 and a mantle and/or lower-middle crustal origin for at least part of the degassed carbon. The presence of deep carbon is a key control on the emplacement mode of CAMP magmas, favouring rapid eruption pulses (a few centuries each). Our estimates suggest that the amount of CO2 that each CAMP magmatic pulse injected into the end-Triassic atmosphere is comparable to the amount of anthropogenic emissions projected for the 21st century. Such large volumes of volcanic CO2 likely contributed to end-Triassic global warming and ocean acidification

The Impact of Global Warming and Anoxia on Marine Benthic Community Dynamics: an Example from the Toarcian (Early Jurassic)

The Pliensbachian-Toarcian (Early Jurassic) fossil record is an archive of natural data of benthic community response to global warming and marine long-term hypoxia and anoxia. In the early Toarcian mean temperatures increased by the same order of magnitude as that predicted for the near future; laminated, organic-rich, black shales were deposited in many shallow water epicontinental basins; and a biotic crisis occurred in the marine realm, with the extinction of approximately 5% of families and 26% of genera. High-resolution quantitative abundance data of benthic invertebrates were collected from the Cleveland Basin (North Yorkshire, UK), and analysed with multivariate statistical methods to detect how the fauna responded to environmental changes during the early Toarcian. Twelve biofacies were identified. Their changes through time closely resemble the pattern of faunal degradation and recovery observed in modern habitats affected by anoxia. All four successional stages of community structure recorded in modern studies are recognised in the fossil data (i.e. Stage III: climax; II: transitional; I: pioneer; 0: highly disturbed). Two main faunal turnover events occurred: (i) at the onset of anoxia, with the extinction of most benthic species and the survival of a few adapted to thrive in low-oxygen conditions (Stages I to 0) and (ii) in the recovery, when newly evolved species colonized the re-oxygenated soft sediments and the path of recovery did not retrace of pattern of ecological degradation (Stages I to II). The ordination of samples coupled with sedimentological and palaeotemperature proxy data indicate that the onset of anoxia and the extinction horizon coincide with both a rise in temperature and sea level. Our study of how faunal associations co-vary with long and short term sea level and temperature changes has implications for predicting the long-term effects of “dead zones” in modern oceans

Earliest Triassic microbialites in the South China Block and other areas; controls on their growth and distribution

Earliest Triassic microbialites (ETMs) and inorganic carbonate crystal fans formed after the end-Permian mass extinction (ca. 251.4 Ma) within the basal Triassic Hindeodus parvus conodont zone. ETMs are distinguished from rarer, and more regional, subsequent Triassic microbialites. Large differences in ETMs between northern and southern areas of the South China block suggest geographic provinces, and ETMs are most abundant throughout the equatorial Tethys Ocean with further geographic variation. ETMs occur in shallow-marine shelves in a superanoxic stratified ocean and form the only widespread Phanerozoic microbialites with structures similar to those of the Cambro-Ordovician, and briefly after the latest Ordovician, Late Silurian and Late Devonian extinctions. ETMs disappeared long before the mid-Triassic biotic recovery, but it is not clear why, if they are interpreted as disaster taxa. In general, ETM occurrence suggests that microbially mediated calcification occurred where upwelled carbonate-rich anoxic waters mixed with warm aerated surface waters, forming regional dysoxia, so that extreme carbonate supersaturation and dysoxic conditions were both required for their growth. Long-term oceanic and atmospheric changes may have contributed to a trigger for ETM formation. In equatorial western Pangea, the earliest microbialites are late Early Triassic, but it is possible that ETMs could exist in western Pangea, if well-preserved earliest Triassic facies are discovered in future work