Axius serratus, a crustacean thought to be extremely rare, was discovered in large numbers in polluted regions of the Strait of Canso. The shrimp may live deeper than 3 meters in the sediment; burrows are kept open to at least 2.5 meters. Sediment contained in old filled burrows is anomalous in its distribution of particle size and its content of water, organic carbon, and trace elements. These anomalous qualitites affect the geotechnical properties of sediments on the sea floor.

Current depositional models largely promote the perception that all open-coastal distal (sea)-proximal (land) gradients are reflected by upward-coarsening grain-size trends, and that shoreline deposits are represented by prominent sand bodies. Although commonly the case, significant departures from this model may occur when the availability of coarser sediment calibers (sand-sized and larger) is limited. This is especially true where alongshore sediment-transport-influenced depositional systems are associated with rivers that supply abundant suspended sediments. Underestimating the role of grain-size segregation may lead to misinterpretations of energy levels and water depths, especially in some shale-dominated sedimentary units.The Upper Cretaceous Alderson Member (Lea Park Fm) is an up to 180-m-thick, gas-charged shale unit that we interpret as an ancient analogue for modern offshore and mud-dominated deltaic coasts. Sedimentological and ichnological data collected from 27 cores indicate that much of the sediment volume of the Alderson Member was deposited in relatively shallow water under the influence of tidal and wave processes in a deltaic coastal setting. Characteristic features reflecting these depositional affinities include: (1) increased proportions of terrestrially derived organic matter; (2) indications of thixotropic to soupy substrates (e.g., fluid mud) coupled with rapid depositional rates; (3) an impoverished ichnological signal (Planolites-dominated suites); (4) micro-laminated shale; (5) shale-on-shale erosional contacts; (6) scour-and-fill structures; and (7) intervals of lowangle cross-stratification. The interpretation of relatively shallow-water settings is also supported by recurring root-bearing horizons, Glossifungites Ichnofacies-demarcated transgressive surfaces of erosion, and conglomeratic surfaces at particular stratigraphic levels. The deposits are interpreted to include offshore, ''subaqueous deltas,'' muddy shoreface and/or tidal flat, and aggradational muddy coastal plain (chenier plain) sub-environments.The results of this study improve our knowledge of ichnological and sedimentological characteristics of shallow-marine shale units, and are potentially useful for recognition of similar nearshore mud-prone deposits elsewhere. J S R J S R FIG. 7.-Core 12, Southern Saskatchewan, upper Alderson. 812J. HOVIKOSKI ET AL. J S R

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