On the parameterization of biological influences on offshore sand wave dynamics

The bed of the North Sea is covered by sand waves and houses a great number of macrobenthic animals. These bio-engineers are known to have a significant influence on the stability of the bed and thereby on the geomorphology of the seabed. This paper proposes a parameterization of these bio-geomorphological interactions. Given the abundance of three dominant bio-engineers on the Dutch Continental Shelf, the predicted occurrence of sand waves, in which the parameterization is included, shows significantly better results, compared to the prediction for the default case without biology. Therefore, the inclusion of biological activity could be important to predict the occurrence of sand waves.     

Predicting the occurrence of sand banks in the North Sea

Sand banks have a wavelength between 1 and 10 km, and they are up to several tens of meters high. Also, sand banks may have an impact on large-scale human activities that take place in the North Sea like sand mining, shipping, offshore wind farms, etc. Therefore, it is important to know where sand banks occur and what their natural behavior is. Here, we use an idealized model to predict the occurrence of sand banks in the North Sea. The aim of the paper is to research to what extent the model is able to predict the occurrence of sand banks in the North Sea. We apply a sensitivity analysis to optimize the model results for a North Sea environment. The results show that the model correctly predicts whether or not sand banks occur for two thirds of the North Sea area.     

The paleoecology and archaeology of long‐term water storage in a Hohokam reservoir,southwestern Arizona,U.S.A.

Water storage reservoirs were an important feature of economic organization among ancient societies in the North American Southwest. Analyses of reservoir sediments from a Hohokam archaeological site in the Sonoran Desert yielded taxonomic species of ostracodes (microscopic crustaceans) and pollen grains that are indicative of a past water‐rich environment. The discovery that this reservoir was capable of storing water on a long‐term basis indicates that archaeological models for the region, which have relied on direct historic analogy, must be reexamined. In contrast to the local ethnographic record, paleoecological data generated by this study imply that the Hohokam could establish permanent desert settlements with water storage reservoirs away from perennial rivers and streams. Moreover, residents of these areas were geographically positioned to facilitate the circulation of marine resources (i.e., salt and shell) from the Gulf of California to territories within and beyond the Hohokam region. © 2004 Wiley Periodicals, Inc.     

Evaluation of Zerovalent Zinc for Treatment of 1,2,3‐Trichloropropane‐Contaminated Groundwater: Laboratory and Field Assessment

The efficacy and feasibility of using zerovalent zinc (ZVZ) to treat 1,2,3‐trichloropropane (TCP)‐contaminated groundwater was assessed in laboratory and field experiments. In the first portion of the study, the reactivity of commercially available granular ZVZ toward TCP was measured in bench‐scale batch‐reactor and column experiments. These results were used to design columns for on‐site pilot‐scale treatment of contaminated groundwater at a site in Southern California. Two of the ZVZ materials tested were found to produce relatively high rates of TCP degradation as well as predictable behavior when scaling from bench‐scale to field testing. In addition, there was little decrease in the rates of TCP degradation over the duration of field testing. Finally, no secondary impacts to water quality were identified. The results suggest that ZVZ may be an effective and feasible material for use in engineered treatment systems, perhaps including permeable reactive barriers.     

Large-scale pesticide monitoring across Great Barrier Reef catchments--Paddock to Reef Integrated Monitoring, Modelling and Reporting Program

The transport and potential toxicity of pesticides in Queensland (QLD) catchments from agricultural areas is a key concern for the Great Barrier Reef (GBR). In 2009, a pesticide monitoring program was established as part of the Australian and QLD Governments' Reef Plan (2009). Samples were collected at eight End of System sites (above the tidal zone) and three sub-catchment sites. At least two pesticides were detected at every site including insecticides, fungicides, herbicides, and the Reef Plan's (2009) five priority photosystem II (PSII) herbicides (diuron, atrazine, hexazinone, tebuthiuron and ametryn). Diuron, atrazine and metolachlor exceeded Australian and New Zealand water quality guideline trigger values (TVs) at eight sites. Accounting for PSII herbicide mixtures increased the estimated toxicity and led to larger exceedances of the TVs at more sites. This study demonstrates the widespread contamination of pesticides, particularly PSII herbicides, across the GBR catchment area which discharges to the GBR.     

Modelling of shallow landslides with machine learning algorithms

This paper introduces three machine learning(ML)algorithms,the‘ensemble'Random Forest(RF),the‘ensemble'Gradient Boosted Regression Tree(GBRT)and the Multi Layer Perceptron neural network(MLP)and applies them to the spatial modelling of shallow landslides near Kvam in Norway.In the development of the ML models,a total of 11 significant landslide controlling factors were selected.The controlling factors relate to the geomorphology,geology,geo-environment and anthropogenic effects:slope angle,aspect,plan curvature,profile curvature,flow accumulation,flow direction,distance to rivers,water content,saturation,rainfall and distance to roads.It is observed that slope angle was the most significant controlling factor in the ML analyses.The performance of the three ML models was evaluated quantitatively based on the Receiver Operating Characteristic(ROC)analysis.The results show that the‘ensemble'GBRT machine learning model yielded the most promising results for the spatial prediction of shallow landslides,with a 95%probability of landslide detection and 87%prediction efficiency.     

Modelling the morphodynamic impact of offshore sandpit geometries

We investigate the hydrodynamic effects and morphodynamic impact of large-scale offshore sand extraction, for a variety of pit designs. We use a process-based idealized model for flow, sediment transport and bed evolution in a tide-dominated environment. Legislation and other practical considerations motivate our assumption that sandpits are both wide (horizontal dimensions of the order of kilometres) and shallow (the ratio of pit depth to water depth being small). This results in a semi-analytical tool that, unlike previous studies, enables a quick and extensive study into the effects of varying the physical characteristics as well as the pit design parameters. These parameters include pit length, width, and orientation with respect to the tide.     

Carboniferous and Permian granites of the northern Tasman orogenic belt, Queensland, Australia: insights into petrogenesis and crustal evolution from an in situ zircon study

In situ U–Pb dating and Lu–Hf systematics of zircon in granites of the Hodgkinson Province in the northern Tasman orogenic belt, Queensland, Australia, reveal input of isotopically more evolved crustal magmas and larger ranges in ¹⁷⁶Hf/¹⁷⁷Hf in the Carboniferous I-type granites (0.28219–0.28269; weighted average ~0.28245) than in the Permian S-type granites (0.28249–0.28280; weighted average ~0.28262) and Permian I-type granites (0.28253–0.28274; weighted average ~0.28260). The wide range in the Hf-isotope compositions of zircons in the Carboniferous and Permian granites can be explained by remelting of a heterogeneous Mesoproterozoic crustal source, whereas a narrow range reflects the subsequent dissolution of inherited grains/cores and magma homogenisation before zircon crystallisation. Alternatively, mixing between the most radiogenic and unradiogenic magmas can produce the isotopic variation seen in other Carboniferous granites. Remelting of Neoproterozoic average crust or mafic younger crust can produce the more radiogenic Hf-isotope compositions of zircons in the Permian S-type granites. An overlap between the Hf-isotope signatures of the Carboniferous I-type granites in the southwestern Hodgkinson Province and the northeastern Australian craton (0.28211–0.28254) and evidence for major magmatic events at 1,585–1,545 and 345–300 Ma imply that the southwestern province is underlain by cratonic crust, which wedges out towards the northeast. The more radiogenic Hf-isotope signature of the Permian granites and a lack of evidence for these major magmatic events in the southeastern and central Hodgkinson Province imply that these parts are characterised by different crustal sources and crustal evolution histories.     

Corundum from basaltic terrains: a mineral inclusion approach to the enigma

 This paper investigates the origin of corundum megacrysts that occur in many basaltic terrains, and which are considered to be eroded from basaltic rocks. Geochemical data for over 80 primary mineral inclusions within corundum megacrysts are used to gain a new insight into the petrogenetic history of the corundum megacrysts. A wide spectrum of minerals is present as inclusions in the corundum; the most common are Nb−Ta oxides (such as titaniferous columbite and uranpyrochlore), alkali feldspar, low-Ca plagioclase (albite-oligoclase) and zircon. Rare inclusions include Fe,Cu-sulphide (low in Ni), cobalt-rich spinel, Th,Ce-rich phosphate and uraninite. The similar chemistry of some inclusion minerals from corundum occurring in widely separated areas suggests that the corundum megacrysts in basalts have a similar petrogenesis. Geochemical characteristics of the inclusions indicate a bimodal grouping, which is best explained by a mixing-hybridisation process. This study indicates that the corundum megacrysts are not cogenetic with their basaltic hosts but are crustal fragments accidentally incorporated into the erupting magma. It is suggested that interactions between a silicic component and an intruding carbonatitic or similar Si-poor magma is responsible for Al-oversaturation, resulting in locally distributed lenses of corundum-bearing rock of mixed paragenesis (“hybrid rock hypothesis”). Feldspar exsolution textures provide strong evidence that this hybridisation occurred at mid-crustal levels. Subsequent volcanic eruptions brought the corundum-bearing rocks (later disintegrated in the magma) up to the Earth's surface. This petrogenetic model for corundum megacrysts is experimentally testable. Received: 15 March 1995 / Accepted: 30 June 1995