Predicting suitability of cockle Austrovenus stutchburyi restoration sites using hydrodynamic models of larval dispersal

An important aspect of shellfish restoration projects is to evaluate whether potential sites are likely to be recolonised naturally once disturbances are removed and habitats are restored. Similarly, if active translocation or reseeding of juveniles or adults is undertaken, it is important to understand whether these introduced populations will be self‐maintaining in future, and whether any seed they produce are likely to be retained within the restored area. We used a combined hydrodynamic and particle tracking model to predict larval dispersion patterns for the common cockle Austrovenus stutchburyi under different hydrodynamic scenarios for seven release locations in Whangarei Harbour, New Zealand. Our results implied that sites varied substantially in their potential for self‐seeding and for exporting seed to other locations. For sites with more restricted dispersal, the model predicted that most larvae originating at these sites would settle inside the release region (68–94% for passive particle simulations), whereas relatively few larvae originating from the other release sites settled at these sites. In contrast, model larvae released from sites exhibiting high connectivity dispersed to all sub‐regions in the harbour, and export outside of the model region was high. Forthcoming field validation of these model predictions will result in better integration of hydrodynamic connectivity in whole estuary restoration programs.     

Volcanic hazard communication using maps: an evaluation of their effectiveness

Hazard maps are considered essential tools in the communication of volcanic risk between scientists, the local authorities and the public. This study investigates the efficacy of such maps for the volcanic island of Montserrat in the West Indies using both quantitative and qualitative research techniques. Normal plan view maps, which have been used on the island over the last 10 years of the crisis, are evaluated against specially produced three-dimensional (3D) maps and perspective photographs. Thirty-two demographically representative respondents of mixed backgrounds, sex, education and location were interviewed and asked to complete a range of tasks and identification on the maps and photographs. The overall results show that ordinary people have problems interpreting their environment as a mapped representation. We found respondents’ ability to locate and orientate themselves as well as convey information relating to volcanic hazards was improved when using aerial photographs rather than traditional plan view contour maps. There was a slight improvement in the use of the 3D maps, especially in terms of topographic recognition. However, the most striking increase in effectiveness was found with the perspective photographs, which enabled people to identify features and their orientation much more readily. For Montserrat it appears that well labelled aerial and perspective photographs are the most effective geo-spatial method of communicating volcanic risks.

Migrating magmatism in the northern US Cordillera: in situ U–Pb geochronology of the Idaho batholith

New in situ laser ablation-inductively coupled plasma-mass spectrometry and sensitive high-resolution ion microprobe U–Pb geochronology of zircons from the Idaho batholith and spatially overlapping Challis intrusions reveals a series of discrete magmatic belts of different ages and compositions. Following the accretion of the Blue Mountains province to North America along the Salmon River suture zone, two compositionally diverse belts of metaluminous plutons formed both adjacent to the suture and well inboard of it. These were constructed from ~100 to 85 Ma and were followed by a voluminous pulse of peraluminous magmatism, forming the bulk of the Atlanta lobe and largest fraction of the batholith between ~80 and 67 Ma. Around 70 Ma, a later and more spatially restricted suite of metaluminous plutons formed around the Bitterroot lobe of the batholith. This was followed by another pulse of voluminous peraluminous magmatism in the Bitterroot lobe, lasting from ~66 to 54 Ma. The changes from low volume metaluminous to high volume peraluminous magmatism may reflect a combination of changes in the angle and segmentation of the subducting Farallon plate and over thickening of the continental lithosphere. All of these features were then cut by plutons and dikes associated with the Challis volcanic field, lasting from ~51 to 43 Ma. Inherited components are pervasive in zircons from most phases of the batholith. While Precambrian components are very common, zircons also often contain cores or mantles that are 5–20 million years older than their rims. This suggests that the early phases of the batholith were repeatedly cannibalized by subsequent magmas. This also implies that the older suites may have been originally more aerially extensive than their currently exposed forms.     

Temporal and geochemical evolution of the Cenozoic intraplate volcanism of Zealandia

In order to constrain better the distribution, age, geochemistry and origin of widespread Cenozoic intraplate volcanism on Zealandia, the New Zealand micro-continent, we report new ⁴⁰Ar/³⁹Ar and geochemical (major and trace element and Sr–Nd–Hf–Pb isotope) data from offshore (Chatham Rise, Campbell and Challenger Plateaus) and onland (North, South, Auckland, Campbell, Chatham and Antipodes Islands of New Zealand) volcanism on Zealandia. The samples include nephelinite, basanite through phonolite, alkali basalt through trachyte/rhyolite, and minor tholeiite and basaltic andesite, all of which have ocean island basalt (OIB)-type trace element signatures and which range in age from 64.8 to 0.17 Ma. Isotope ratios show a wide range in composition (⁸⁷Sr/⁸⁶Sr = 0.7027–0.7050, ¹⁴³Nd/¹⁴⁴Nd = 0.5128–0.5131, ¹⁷⁷Hf/¹⁷⁶Hf = 0.2829–0.2831, ²⁰⁶Pb/²⁰⁴Pb = 18.62–20.67, ²⁰⁷Pb/²⁰⁴Pb = 15.54–15.72 and ²⁰⁸Pb/²⁰⁴Pb = 38.27–40.34) with samples plotting between mid-ocean-ridge basalts (MORB) and Cretaceous New Zealand intraplate volcanic rocks.Major characteristics of Zealandia's Cenozoic volcanism include longevity, irregular distribution and lack of age progressions in the direction of plate motion, or indeed any systematic temporal or spatial geochemical variations. We believe that these characteristics can be best explained in the context of lithospheric detachment, which causes upwelling and melting of the upper asthenospheric mantle and portions of the removed lithosphere. We propose that a large-scale seismic low-velocity anomaly, that stretches from beneath West Antarctica to Zealandia at a depth of > 600 km may represent a geochemical reservoir that has been in existence since the Cretaceous, and has been supplying the upper mantle beneath Zealandia with HIMU-type plume material throughout the Cenozoic. In addition, the sources of the Cenozoic intraplate volcanism may be at least partially derived through melting of locally detached Zealandia lower lithosphere.     

The geochemistry of primary and weathered oil shale and coquina across the Julia Creek vanadium deposit (Queensland, Australia)

A significant resource of vanadium and molybdenum exists near Julia Creek, Australia, where the middle Cretaceous organic-rich Toolebuc Formation lies between 0 and 25 m of the surface. We present and discuss a comprehensive geochemical study of the Toolebuc Formation and its enclosing stratigraphy near Julia Creek to understand this ore deposit. V and Mo contents in fresh facies are strongly associated with total organic carbon (TOC) contents, but not with Al or CaCO₃; this suggests that V and Mo were originally concentrated in the organic fraction. However, chemical extractions using H₂O₂ indicate that Mo was originally concentrated in pyrite. The data also suggest that V was mobilised from organic matter during early diagenesis and became associated with clays as little V was extracted by H₂O₂ in the fresh samples. TOC contents in the Toolebuc Formation were removed during weathering, residually enriching trace metals including V and Mo, and as a result, the TOC relationship with V and Mo disintegrates. With weathering, both V and Mo predominantly became associated with iron oxide/hydroxide phases (and possibly other unidentified phases) as these elements in the weathered facies were highly soluble in the sodium citrate–sodium dithionite digestion. Large shale-hosted V and Mo deposits such as Julia Creek offer a potentially viable alternative to the currently mined magnetite-hosted deposits. A thorough understanding of the formation and host mineral phases for V and Mo of these shale deposits, however, is critical to ensure that these valuable metals can be feasibly extracted.     

Estimation of aseismic crustal-strain using radon precursors of the 2003 <Emphasis Type="Italic">M</Emphasis> 6.8, 2006 <Emphasis Type="Italic">M</Emphasis> 6.1, and 2008 <Emphasis Type="Italic">M</Emphasis> 5.0 earthquakes in eastern Taiwan

Aseismic crustal-strain signals prior to the 2003 Mw 6.8 Chengkung, 2006 Mw 6.1 Taitung, and 2008 Mw 5.0 Antung earthquakes with epicenters located 20, 55 and 11 km, respectively, from the Antung radon-monitoring station have been calculated using the radon anomalies recorded. Specifically, radon decreased from background levels of 791 ± 46, 762 ± 57, and 735 ± 48 pCi/L to minima of 326 ± 9, 371 ± 9, and 480 ± 43 pCi/L prior to the 2003, 2006, and 2008 earthquakes, respectively. The estimated aseismic crustal-strain maxima at the Antung hot spring during the rock dilation stage were 3.6, 2.7, and 1.3 ppm, respectively. The v-shaped radon pattern recognized in all three anomalies is valuable for detecting the aseismic strain precursory to disastrous earthquakes in the Antung hot spring which is situated in a brittle fractured aquifer of limited recharge surrounded by ductile mudstone.     

Géomorphologie de Tromelin,océan Indien

Tromelin is a small coral reef island (1 km²) located in the Indian Ocean, approximately 440 km east of Madagascar and 580 km north of La Réunion. Despite the presence of a permanent Météo France weather station on Tromelin since the 1950 s, a detailed geomorhological study of the island has never been undertaken. In this paper, we describe results from the 2008 field season, which enabled us to map and describe seven geomorphological zones on the atoll. (1) Tromelin's bathymetry is characterised by a pronounced submarine slope, which attains depths of 1000 m at only 2.5 km from the island's coastline. This geomorphology is typical of volcanic hotspots. (2) A coral platform borders the emerged crown of the island. This platform is exposed at low tide and has been fashioned in an ancient Pleistocene substratum. The substratum has been eroded by abrasive marine action to its present shape since the stabilisation of relative sea level around 6000 years ago. Erosion of the reef yields most of the biogenic sediment supply to the island. (3) The upper foreshore is characterised by outcrops of beachrock. These formations show a stratfication in slabs and dip gently towards the sea in the same manner as the contemporary clastic sediments. (4) Tromelin's beaches are divided into three sub-units, which reflect the different energy dynamics around the island, in addition to the transfer of sediment from the windward to the leeward side: (i) the southern storm beaches are characterised by coral blocks reworked during episodic high-energy events; they form boulder ramparts. Four perched rampart ridges have been recorded at ∼1 m, ∼3 m, ∼4.5 m and ∼7 m above mean sea level; (ii) transitional beaches are observed between the south and the north, constituting storm blocks and coarse sands and gravels; and (iii) sandy beaches are noted on the northern leeward side, comprising rounded gravels and coarse sands. The northern tip of the island is characterised by a sand spit (∼125 × ∼225 m), whose geometry varies based on the seasonal and meteo-marine contexts. (5) On Tromelin, a number of dune formations are observed. These are best developed in the north of the island due to the south-north translation of clastic sediments by aeolian wind action, and the trapping of sands by the well-developed vegetation. The height of the dunes varies between 10 cm (the southern micro-dunes) to 250 cm in the Northeast of Tromelin. (6) Exceptional waves have deposited storm tracts up to 250 m from the foreshore zone, comprising coarse gravels and coral blocks. The storm tract deposits are most prevalent on the windward side of the island, due not only to the high-energy dynamics, but also to the absence of vegetation cover in this area. (7) The southern depression covers an area of ∼40,000 m². At its lowest point it is only 1.2 m above sea level.     

Complex adaptive blended learning for higher GIS education: A theory-driven pedagogy moving forward after the pandemic

None of the prior studies implementing blended learning (BL) for GIS education has explored pedagogical theories to support BL design, and none coupled blended GIS learning practice with theories. Based on the theoretical framework of complex adaptive blended learning system (CABLS), this article presents a holistic and systematic view of BL for higher GIS education (termed as CABLS-GIS), where its key components are tightly integrated as an integral whole. The framework was implemented for an introductory-level GIS course to empirically evaluate the effectiveness of a BL design from students' perspectives. Most students involved in the implementation agreed that the BL enhanced their learning outcomes. They were mostly positive about the BL and motivated to use the BL materials. Incorporating more BL materials, especially practical ones, and active learning activities were suggested by them. A few negative comments about the BL suggested a thorough consideration of individual learners' characteristics.     

An assessment of geologic sequestration potential in the panhandle of Florida USA

One alternative to reduce global greenhouse gas emissions is to store the emissions in underground geologic sequestration repositories. The efficacy of this approach has been favorably evaluated by numerous authors over the last 15 years. This paper discusses an assessment of the overall feasibility of storing emissions in three different repositories in the Florida panhandle located in the Southeastern United States. The feasibility assessment evaluates both saline aquifers and oil reservoirs located in the panhandle region. The overall feasibility is driven by the available geologic sequestration capacity, the transportation cost to deliver emissions to a respective repository, and other engineering and regulatory issues. The geologic sequestration capacity is generally controlled by the so-called storage efficiency, a variable dependent on the site-specific geology, reservoir conditions, and the injected fluid characteristics. For this paper, storage efficiency for saline repositories was assessed in more detail using numerical modeling. Based on the work completed, the 3 repositories studied have at least 4.55 gigatonnes of capacity to sequester CO₂.