Outcrops of pebbly mud (diamict) at Scarborough in Southern Ontario, Canada (the so-called Sunnybrook ‘Till’) are associated with the earliest incursion of the Laurentide Ice Sheet (LIS) into mid-continent North America some 45,000 years ago. The Sunnybrook is a blanket-like deposit containing deepwater ostracodes and occurs conformably within a thick (100 m) succession of deltaic and glaciolacustrine facies that record water depth changes in a large proglacial lake. Contextual evidence (associated facies, sedimentary structures, deposit geometry and landforms) indicates a low energy depositional setting in an ice-dammed ancestral Lake Ontario in which scouring by floating ice masses was an important process. U-shaped, iceberg-cut scours (with lateral berms) up to 7 m deep, occur on the upper surface of the Sunnybrook and are underlain by ‘sub-scour’ structures that extend several meters below the scour base. Ice-rafted concentrations of clasts (‘clast layers’), grooved surfaces formed by floating ice glissading over a muddy lake floor (‘soft sediment striations’) and melanges of sand and mud mixed by grounding ice keels (‘ice keel turbates’) are present and are all well known from modern cold environments. The wider significance of this depositional model is that the LIS margin lay east of Scarborough and did not overrun Southern Ontario. This finding is in agreement with recent data from the Erie Basin of Canada, Ohio, and Indiana where deposits formerly correlated with the Sunnybrook (and thus implying an extensive early Wisconsin ice sheet) are now regarded as Illinoian. A speculative hypothesis is proposed that relates deposition of the Sunnybrook and two younger deposits of similar sedimentology, to surge-like instabilities of the southern LIS margin.
The feeding habits of the winter flounder (Pleuronectes americanus) were examined in a habitat subjected to chronic anthropogenic disturbance by organic and inorganic nutrient disposal and shipping activity. The macrobenthic community was numerically dominated by the types of polychaetes and amphipods found in a disturbed community. Little variability was found in the diets of 151 winter flounder (100-300 mm total length) in 4 size-classes. Combining all size-classes, winter flounder were found to feed on 18 different genera of macrobenthos. Amphipods and polychaetes dominated the diet. These groups provided from 12-25% of the diet by weight, 16-48% by number, and had index of relative importance values between 552 and 2 510. Major prey items were the amphipod, Ampelisca abdita and the polychaete, Streblospio benedicti. These diets were compared to those winter flounder captured in habitats where benthic assemblages were not exposed to human perturbation. Regardless of habitat, winter flounder fed on primarily the most abundant and active benthic species. This study supports the contention that winter flounder are in general, opportunistic feeders and usually feed on the most abundant and available prey source.
A prototype decision support tool is described which provides options for the management of existing green spaces and for the establishment of new green space in suburban neighbourhoods. Suggested neighbourhood greening techniques include the naturalization of existing parks and increased foliage along streets and rights of way. The naturalization approach involves less frequent cutting in grassy fields, the introduction of native species, and the cessation of pesticide and herbicide applications. Increased plantings along streets and boulevards would improve the aesthetics of neighbourhoods, and may provide some relief from climatic extremes and urban heat island effects. The creation of new green space in already-built suburban neighbourhoods provides a longer term challenge to neighbourhood planners. Potential strategies include the introduction of small pocket parks and community gardens in vacant lots and school yards. Modelled outcomes from such neighbourhood greening strategies could be used in public meetings both to incorporate attitudes of the impacted community and to demonstrate benefits to a wider community. In particular, strategies should take into account issues of safety and perceived safety that commonly arise with the greater use of naturalization in green space management. The developed prototype decision support tool has been coded as an ArcView GIS extension and provides the opportunity to model and evaluate future scenarios better aligned to principles of sustainable community development. Three applications of this tool are discussed to illustrate some of the benefits of undertaking a range of neighbourhood greening strategies.
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