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The Ediacaran of eastern Newfoundland preserves the world's oldest known eumetazoan body fossils, as well as the earliest known record of fossilized muscular tissue. Re-examination of the holotype of the eight-armed Haootia quadriformis in terms of its morphology, the arrangement of its muscle filament bundles, and hitherto undescribed aspects of its anatomy support its interpretation as a crown staurozoan. We also document several new fossils preserving muscle tissue with a different muscular architecture to Haootia, but with only four arms. This new material allows us to describe a new crown group staurozoan, Mamsetia manunis gen. et sp. nov. This work confirms the presence of crown group medusozoan cnidarians of the Staurozoa in the Ediacaran of Newfoundland circa 565 Ma. [ABSTRACT FROM AUTHOR]

A resistive switching ZnO n–n homojunction diode fabricated with a stack of two dissimilar ZnO thin films shows promising characteristics necessary to address the crosstalk problem in a crossbar memory array. The device has a characteristic I–V-hysteresis loop in forward bias, in conjunction with its n–n junction characteristics. In the ac frequency range of 10 Hz–15 kHz, the area inside the hysteresis loop initially increased, reaching a maximum at 1 kHz, and then decreased with increasing frequency. The maximum in the area of the hysteresis loop corresponds to the accumulation of space charge at the interface. The resistivity of the device was found to vary from 5 to 100 kΩ in the bias range of 0–10 V and in the range of 106 Ω when reverse biased; the ratio of high resistive state to low resistive state has its maximum (∼2.4) at 1 kHz ac signal at 3 V. [ABSTRACT FROM AUTHOR]

By controlled experiments that simulate marine conditions, it is shown that accelerated weathering and mineral authigenesis occur during the combined process of digestion, ingestion and excretion of sediment by worms. Previously characterized synthetic mud, composed of finely ground, low-grade metamorphic slate dominated by highly crystalline chlorite and muscovite, was unchanged in control tanks over a 20 week time scale, but was significantly different in faecal samples from an experimental tank populated with the annelid Arenicola marina. Chlorite was preferentially destroyed during digestion and both chlorite and muscovite underwent peak broadening with a skew developing towards higher lattice spacings. Neoformed minerals with very high d-spacings and a mineral with 0.75 nm basal lattice spacing (possibly berthierine) were detected in the cast samples. It is postulated that the lowered pH microenvironment in the guts of organisms may accelerate mineral dissolution and precipitation processes during ingestion. These results show that macrobiotic activity significantly accelerates weathering and mineral degradation along with mineral authigenesis. Neoformed minerals produced in this way would be likely to form the precursors of diagenetic clay mineral cements and thus have an impact on sandstone reservoir quality. Keywords: worms, weathering, authigenesis, clay minerals, reservoir quality.

Research literature abounds on the depositional processes and products associated with macro-tidal regimes, whereas there is little available literature on sediments deposited in micro-tidal regimes. This paper presents new field-based sedimentological interpretations of the Marsdenian (Namurian, Carboniferous) interval of the Pennine Basin, a basin-fill that is classically regarded as the archetypal fluvial-dominated delta system. This paper reinterprets discrete lithostratigraphic units, and suggests they were deposited under the influence of weak tidal currents. We highlight three lithofacies that contain tidally influenced deposits within the Marsdenian interval of the Pennine Basin; a cross-bedded sandstone with mud drapes and reactivation surfaces, a heterolithic ripple-laminated sandstone with muddy drapes and silty mudstone interlaminations, and a rhythmic--parallel-bedded sandstone with mudstone--siltstone interlaminations. Evidence for cryptic tidal signatures in tractionally transported and reworked sediments is qualitative, and largely dependent on the sedimentologist's view of what constitutes a diagnostic number of tidal indicators (i.e. mud-drape couplets, reactivation surfaces). In areas away from either tractional deposition or reworking, sediments deposited from suspension are more likely to preserve indicators of tidal processes. This paper focuses on a lithofacies interpreted as a tidally influenced sand-rich delta-front mouthbar deposited from a buoyant effluent plume. Time-series analysis of laminae thickness variations in this facies implies that these variations are rhythmic. We review how the interaction of tidal currents and buoyant plume processes modifies depositional products. This model implies that the rhythmic variation observed in the Marsdenian interval is attributed to the modulation of plume deposition by tidal currents with a semi-diurnal and diurnal tidal periodicity. Keywords: Marsdenian, Pennine Basin, deltaic sedimentation, tidal currents.

A survey of undergraduate science students showed varied levels of computing attitudes and anxieties. Gender differences are more likely to persist at the factor level, and students with a positive first experience tended to alleviate anxiety but did not ensure a positive attitude.

Three elements of the 'Ediacara fauna' are described from lower Cambrian strata on the Digermul Peninsula, Norway. Nimbia occlusa Fedonkin, 1980 and Tirasiana sp. occur approximately 80 m above the base of the Lower Breivik Member, which approximately coincides with the Neoproterozoic-Cambrian boundary. A specimen of Cyclomedusa sp. has also been found in the Lower Duolbasgaissa Member about 600 m above the boundary, in rocks of trilobite-bearing age. These discoveries add to a growing body of evidence that some elements of the dominantly Neoproterozoic Ediacara fauna continue into the Phanerozoic, thereby diminishing the scope of a possible late Neoproterozoic mass-extinction event. The taxa described here, particularly Nimbia and Cyclomedusa, also occur at many other localities within Neoproterozoic strata and, in common with other elements of the Ediacara fauna, display remarkable morphological variation. Some of this diversity in form is probably caused by environmental and preservational factors. The possibility that it may, at least in part, reflect an inability of these early life forms to replicate faithfully their genes during reproduction should, however, not be overlooked.

Lower Cambrian sediments from the Withycombe Farm borehole (Oxfordshire) yield isolated halkieriid sclerites. All bear prominent ridges, and most appear to be either cultrates or palmates, although distinction between the two in the available material is generally difficult. Two other sclerites are more elongate: one may represent a spinose sclerite, while the other is possibly derived from the siculate zone of the original scleritome. Adjacent horizons of the Withycombe Formation yield disc-like fossils, superficially similar to hyolith opercula or monoplacophorans. These are tentatively identified as deriving from the same halkieriid scleritome. Two main types are identified, and these may correspond to the anterior and posterior shells of Halkieria evangelista from the lower Cambrian Sirius Passet fauna of North Greenland. The age of the Withycombe Formation within the Cambrian is not entirely resolved, but faunal evidence suggests an equivalence to the Cuslett Formation of southeast Newfoundland, which corresponds to either the upper Tommotian or lower Atdabanian of the standard Siberian section.

A revised interpretation for the 'Charnian Supergroup' is suggested from ichnological and lithological comparisons with the Cambrian of Nuneaton and other parts of the Avalonian superterrane. Late Neoproterozoic volcaniclastic sediments contain an Ediacara fauna in the Maplewell Group. These are succeeded by one or more inferred erosional breaks and overlain by passive margin sediments (quartz-arenites, glauconitic greywackes, pelites) of the Brand Group which yield Cambrian trace fossils, including abundant large Teichichnus. This transformation is compared with that between the Neoproterozoic Caldecote Volcanic Formation and the Cambrian Hartshill Formation at Nuneaton. The Hanging Rocks Formation of the Brand Group lies above a major erosional break but shares a volcanogenic island arc petrology with the underlying Maplewell Group. Conglomeratic sandstones at the base of the Brand Hills Formation contain purple pelite clasts comparable with underlying lithologies, plus clasts of weathered diorite showing granophyric textures identical to those seen in the enigmatic South Charnwood Diorites. Nd-Sm isotope studies confirm the geochemical similarity between these diorites and those that intruded the Caldecote Volcanics at Nuneaton, previously U-Pb zircon dated at 603 [+ or -] 2 Ma. These strong similarities with the Nuneaton succession suggest that deposition of the Brand Hills Formation in the Cambrian was preceded by the local unroofing of diorite and erosion of underlying mudrocks, much as seen in other parts of Avalonia. A date of 603 [+ or -] 2 Ma for the South Charnwood Diorites provides a minimum age for the local Ediacara fauna but this is in need of substantiation. Keywords: Proterozoic, Precambrian, Cambrian, Ediacara, ichnofossils.

A chain of pellets (Neonereites uniserialis), usually attributed to a coelomate or pseudocoelomate metazoan, is described from the middle Dalradian Bonahaven Formation of western Scotland, in sandstones not far above the Port Askaig Tillite. This trail lies more than 8 km below U-Pb zircon-dated Tayvallich lavas (595 [+ or -] 4 Ma) and predates early deformation plus intrusion by granites at Ben Vuirich dated at 597 [+ or -] 11 and 590 [+ or -] 2 Ma. U-Pb zircon chronology for early metazoan evolution suggests that this is the earliest putative evidence for coelomates or pseudocoelomate discovered so far, with a minimum 'interglacial' age of c. 600 Ma BP. It is from about this time that a fall takes place in the maximum [[Delta].sup.13]C of carbonates, suggestive of a decline in the long term rate of carbon burial. One explanation for this decline is the increasing impact of metazoan bioturbation through the late Neoproterozoic to Cambrian interval. Keywords: Proterozoic, Dalradian, Cambrian, ichnofossils, U-Pb.