Two new species of Pseudostomella (Gastrotricha: Macrodasyida) with scaled triancres from the east coast of Australia

Two new species of Pseudostomella from North Stradbroke Island, Australia, P. klauserae n. sp. and P. megapalpator n. sp., are characterised by scaled triancres, cuticular structures that until now were known only from one other member of the genus. The structure of the scaled triancres in both species is new: the triancre base is diamond‐ or triangular‐shaped with three shafts that arise to form feather‐like scales. P. klauserae n. sp. is characterised by scales arising from a diamond‐shaped triancre base, the distribution of cephalic papillae, and the abundance and distribution of anterior and lateral adhesive tubes. P. megapalpator n. sp. is distinguished by scales arising from a rounded‐triangular triancre base, large dorsal, digitiform papillae, and ventral adhesive tubes. The presence of two new species with scaled triancres allows for the formation of a novel species complex within the genus. An amended key to the species is included.     

Primary productivity in the German Bight (1994–1996)

Within the KUSTOS program (Coastal Mass and Energy Fluxes-the Land-Sea Transition in the Southeastern North Sea) 28 to 36 German Bight stations were seasonally surveyed (summer 1994, spring 1995, winter 1995–1996) for light conditions, dissolved inorganic nutrient concentrations, chlorophylla (chla), and photosynthesis versus light intensity (P:E) parameters. Combining P:E curve characteristics with irradiance, attenuation, and chlorophyll data resulted in seasonal estimates of the spatial distribution of total primary production. These data were used for an annual estimate of the total primary production in the Bight. In winter 1996 the water throughout the German Bight was well mixed. Dissolved inorganic nutrient concentrations were relatively high (nitrogen [DIN], soluble reactive phosphorus [SRP], and silicate [Si]: 23, 1, and 10 μM, respectively). Chla levels generally were low (< 2 μg l⁻¹) with higher concentrations (4–16 μg l⁻¹) in North Frisian coastal waters. Phytoplankton was limited by light. Total primary production averaged 0.2 g C m⁻² d⁻¹. Two surveys in April and May 1995 captured the buildup of a strong seasonal thermo-cline accompained by the development of a typical spring diatom bloom. High nutrient levels in the mixed layer during the first survey (DIN, SRP, and Si: 46, 0.45, and 11 μM, respectively) decreased towards the second survey (DIN, SRP, and Si: 30.5, 0.12, and 1.5 μM, respectively) and average nutrient ratios shifted further towards highly imbalanced values (DIN:SRP: 136 in survey 1, 580 in survey 2; DIN:Si: 13.5 in survey 1, 96 in survey 2). Chla ranged from 2 to 16 μg l⁻¹ for the first survey and rose to 12–50 μg l⁻¹ in the second survey. Phytoplankton in nearshore areas continued to be light limited during the second survey, while data from the stratified regions in the open German Bight indicates SRP and Si limitation. Total primary production ranged from 4.0 to 6.3 g C m⁻² d⁻¹. During summer 1994 a strong thermal stratification was present in the German Bight proper and shallow coastal areas showed unusually warm (up to 22°C), mixed waters. Chla concentrations ranged from 2 to 18 μg l⁻¹. P:E characteristics were relatively high despite the low nutrient regime (DIN, SRP, and Si: 2, 0.2, and 1.5 μM, respectively), resulting in overall high total primary production values with an average of 7.7 g C m⁻² d⁻¹. Based on the seasonal primary production estimates of the described surveys a budget calculation yielded a total annual production of 430 g C m⁻² yr⁻¹ for the German Bight.     

The Cognitive Load of Geographic Information

Multimedia presentations that combine verbal and visual information are increasingly becoming important methods for communicating geographic information. This article discusses literature related to cognitive load theory (CLT) and offers ideas on how this theory might be used for geography education and research. By considering the limitations of the human mind, CLT offers geographers a way to assess critical components of the spatial learning processes. Methods for measuring cognitive load and reducing overloads are discussed within a map context. It is argued that managing the cognitive load experienced by learners is the key to representing geographic information.     

Glauconite

The term glauconite has been employed in two senses. It has been used most commonly as a morphological term for sand-sized greenish grains found in sedimentary rocks, but also as a name for a specific mineral species, a hydrated iron-rich micaceous clay mineral. The two uses are not synonymous, since not all morphological glauconite consists exclusively of mineral glauconite, nor is the latter restricted in its occurrence to such pellets. Mineral glauconite in sensu lato is a random interstratification of nonexpanding 10A?layers and expanding montmorillonitic layers. The amount of expandable layers may be over 50 % but it is customary to restrict the name mineral glauconite in sensu stricto to varieties with less than 10 % expandable layers. The variation in amount of expandable layers explains many of the observed variations in the properties of glauconite including chemical composition (especially potassium content), thermal characteristics, cation exchange capacity, colour, refractive index and specific gravity. Mineral glauconite is believed to form by the progressive absorption of potassium and iron by a degraded layer silicate lattice of low lattice charge and elimination of other silicate-lattice types under suitable environmental conditions, of which the most critical seems to be the redox potential. The catalytic activity of marine organisms is no longer thought to be essential, although decaying organic matter and empty foraminiferal tests supply the ideal environment for glauconite genesis. The process of glauconitization is arrested by rapid sedimentation, so that there is a relationship between the variety of mineral glauconite formed and the nature of the host rock. Glauconite is found associated particularly with marine transgressions. Morphological glauconite grains are believed to form as casts, faecal pellets or by accretionary growth, but may have their morphology modified by subsequent re-working. A number of characteristic internal and external morphologies have been recognised. The wide range of environmental conditions suitable for its formation and its common detrital occurrence debars the use of glauconite in palaeo-environmental studies. Its major use in geology is for the absolute age dating of sedimentary rocks by the K-Ar method. Glauconitic deposits have no present day commercial value, but soils formed on glauconitic parent materials are notable for their fertility. Glauconite weathers by loss of potassium to produce a montmorillonitic or vermiculitic product with the release of, or oxidation of, structural iron, so that the grain has the appearance of having weathered to limonite.     

A Reservoir–Geomechanical Model to Study the Likelihood of Tensile and Shear Failure in the Caprock of Weyburn CCS Project with Regard to Interpretation of Microseismic Data

According to poroelastic theory and also field observations, an increase in reservoir pore pressures can result in a decrease in horizontal stresses in the seal layers. This reduction is in favor of hydrofracture initiation and reactivation of weak planes and has to be studied in caprock integrity analyses. In this paper, a field scale reservoir–geomechanical (GEM-FLAC3D) model is developed for the Phase IB area of the Weyburn (Canada) CCS project that is located in Williston sedimentary basin. A one-way coupling has been conducted between the two codes for the period of CO₂ injection in Phase IB area from 2000 to 2010. Therefore, the reservoir pore pressures at selected timesteps are unidirectionally fed to the FLAC3D. In order to study the likelihood of tensile and shear failure in the seal layer on top as a result of stress transfer due to poroelastic effects, two margin ratios are defined for tensile and shear failure and their variations are studied above the reservoir upon changes in pore pressures within the reservoir. The results show that overall; the likelihood of shear failure has been about 25% greater than that of tensile failure in Weyburn. However, between 2008 and 2009, the pressures were high enough to trigger both tensile and shear mechanisms above the reservoir. A discussion is also presented on relevance of this study for interpretation of microseismic data with regard to failure margin ratios, magnitudes and distribution of events recorded in each year.     

Atom Probe Tomography: Development and Application to the Geosciences

Atom probe tomography (APT) is an analytical technique that provides quantitative three‐dimensional elemental and isotopic analyses at sub‐nanometre resolution across the whole periodic table. Although developed and mostly used in the materials science and semiconductor fields, recent years have seen increasing development and application in the geoscience and planetary science disciplines. Atom probe studies demonstrate compositional complexity at the nanoscale and provide fundamental new insights into the atom‐scale mechanisms taking place in minerals over geological time. Here, we provide an overview of APT, including the historical development and technical aspects of the instrumentation, and the fundamentals of data acquisition, data processing and data reconstruction. We also review previous studies and highlight the potential future applications of nanoscale geochemical studies of natural materials.     

Strontium isotopic geochemistry of the volcanic rocks and associated megacrysts and inclusions from Ross Island and vicinity,Antarctica

Twelve whole-rock samples of volcanic rocks and a composite of 11 basanitoid samples from Ross Island and vicinity, Antarctica show a narrow range of ⁸⁷Sr/⁸⁶Sr ratios from 0.7030₅ to 0.7033₉. This range is consistent with a model of differentiation from a single parent magma, but the data allow a 30% variation in the ⁸⁷Rb/⁸⁶Sr ratio in the source region if the average ratio is less than 0.057 and if the source region has existed as a closed system for 1.5 b.y. Megacrysts of titaniferous augite, kaersutite, and anorthoclase are isotopically indistinguishable from the host volcanic rocks and therefore are probably cogenetic with the volcanic sequence. A single trachyte sample is isotopically distinct from the rest of the volcanic rocks and probably was contaminated with crustal strontium.Ultramafic and mafic nodules found in association with basanitoids and trachybasalts have ⁸⁷Sr/⁸⁶Sr ratios ranging from 0.7027₅ to 0.7057₅. Several of these nodules exhibit evidence of reaction with the melt and are isotopically indistinguishable from their hosts, but data for seven granulite-facies nodules show an apparent isochronal relationship. Although this isochron may be fortuitous, the resulting age of 158±22 m.y. is similar to ages reported for the voluminous Ferrar Dolerites, and suggests isotopic re-equilibration within the lower crust and upper mantle. These nodules are not genetically related to the Ferrar Dolerites, as evidenced by their lower initial ⁸⁷Sr/⁸⁶Sr ratios.Three ultramafic nodules are texturally and isotopically distinct from the rest of the analyzed nodules. These are friable, have larger ⁸⁷Sr/⁸⁶Sr ratios, and may represent a deeper sampling of mantle rock than the granulite-facies nodules. They were, however, derived at a shallower depth than the alkalic magma. Thus they are not genetically related to either the magma or the granulite-facies nodules.     

Marine radiocarbon reservoir corrections (∆R) for Chesapeake Bay and the Middle Atlantic Coast of North America

Radiocarbon dates from known age, pre-bomb eastern oyster (Crassostrea virginica) shells provide local marine reservoir corrections (?R) for Chesapeake Bay and the Middle Atlantic coastal area of eastern North America. These data suggest subregional variability in ?R, ranging from 148 ± 46 ¹⁴C yr on the Potomac River to ? 109 ± 38 ¹⁴C yr at Swan Point, Maryland. The ?R weighted mean for the Chesapeake's Western Shore (129 ± 22 ¹⁴C yr) is substantially higher than the Eastern Shore (? 88 ± 23 ¹⁴C yr), with outer Atlantic Coast samples falling between these values (106 ± 46 and 2 ± 46 ¹⁴C yr). These differences may result from a combination of factors, including ¹⁴C-depleted freshwater that enters the bay from some if its drainages, ¹⁴C-depleted seawater that enters the bay at its mouth, and/or biological carbon recycling. We advocate using different subregional ?R corrections when calibrating ¹⁴C dates on aquatic specimens from the Chesapeake Bay and coastal Middle Atlantic region of North America.