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A map depicting glacial dispersal trains in North America has been compiled from published sources. It covers the Canadian Shield, the Arctic Islands, the Cordillera and Appalachian mountains, and Phanerozoic sedimentary basins south of the Shield. In total, 140 trains are portrayed, including those emanating from major mineral-deposit types (e.g. gold, base metal, diamondiferous kimberlite, etc.). The map took 10 years of on-and-off work to generate, and it culls data from over 150 years of work by government, industry, and academia. It provides a new tool to help companies find ore deposits in Canada: the trains are generally a better predictor of dispersal distance and direction than striations and streamlined landforms, the data typically depicted on surficial-geology maps, including the Glacial Map of Canada. It also gives new insight into sedimentation patterns and processes beneath ice sheets, a sedimentary environment that, because of its inaccessibility, remains poorly understood and controversial. [ABSTRACT FROM AUTHOR]

In regions formerly covered by continental ice, till sheets may contain distinctive clastic particles derived from local bedrock sources such as ore bodies. Such particles, especially in thicker tills, may be distributed in three-dimensional dispersal trains or plumes. Developments in our understanding of glacial erosion, entrainment, and deposition over the past two or three decades help clarify formation of these plumes. Much of the debris in the basal ice of ice sheets is likely incorporated at places where water is freezing onto the base of the ice sheet. This water, largely a product of melting of basal ice further upglacier, has migrated downglacier under the influence of a gradient in the hydraulic potential controlled primarily by the ice surface slope and secondarily by basal topography and thermal regime. Refreezing occurs over a substantial distance along flow, so as the ice moves away from an ore body, material eroded from the body is later elevated above the bed by refreezing of more meltwater, incorporating additional material derived from the country rock. Broadening and mixing of the plume, both vertically and horizontally, can occur by shear in the ice, by shifting ice flow directions, by collisions between particles, and by folding of basal ice layers. Further downflow, where net basal melting resumes, the debris is deposited by meltout or lodgement. Many idiosyncrasies of dispersal plumes are likely caused by non-steady-state changes in basal thermal regime. [ABSTRACT FROM AUTHOR]

We review over 100 years of literature on Prairie buried valleys to provide a platform for future research and policy development. Prairie buried-valley fills commonly function as aquifers that yield abundant groundwater. They have distinct geologies and a distinct stratigraphic setting, which imparts them with distinct hydrogeological properties and gives clues as to how they formed and filled. Prairie buried-valley aquifers are commonly encased in low-permeability strata: Cretaceous shale commonly underlies them, and thick (10-300 m) low-permeability Quaternary till tends to overlie them. This reduces recharge, in rare cases nearly completely, while protecting groundwater resources from contamination and drought. It also tends to lead to highly mineralized groundwater chemistries. The stratigraphic position of Prairie buried valleys also speaks to their origin: those that subtend ('hang') from the bedrock unconformity were likely eroded by preglacial fluvial systems during late Tertiary uplift of the Rocky Mountains, whereas those that subtend from surfaces within the till package are likely glaciofluvial valleys eroded in proglacial spillway or tunnel-valley settings. Another key trait of Prairie buried valleys is that their fills tend to be heterogeneous and architecturally complex. Sand, gravel, mud, and diamicton are common; any one can dominate the fill at a given location. This heterogeneity, in conjunction with irregularity common to buried-valley bedrock floors, commonly causes aquifer compartmentalization and makes prediction of aquifer potential difficult prior to drilling. It also suggests that most Prairie buried valleys filled over time, and likely over multiple glaciations, in multiple depositional environments. [ABSTRACT FROM AUTHOR]

Abstract: Eskers are commonly sampled for indicator minerals during drift prospecting campaigns on the Precambrian Shield. However, a literature review reveals that indicator mineral dispersal in esker sedimentary systems is poorly understood. As a result, exploration companies lacking their own proprietary knowledge are left with little basis for understanding how to collect esker samples or how to interpret esker data. Based on the literature review, and drawing insights from a broader body of literature on modern glaciers, laboratory experiments, and gravel-bed streams, a preliminary conceptual framework for esker sedimentary systems is established to address these issues. A research strategy is then outlined, one whose objective is to fill knowledge gaps and, in doing so, improve the effectiveness of mineral exploration in glaciated terrain. [Copyright &y& Elsevier]

The article discusses a study on the sequence stratigraphy of a glaciated basin fill using an integrated data set of cores, out-crop data, seismic transects from the Vars-Winchester esker in the Champlain Sea basin in Ottawa, Ontario. The researchers explained that the esker has been obtained from the underlying till by water that flowed through a subglacial conduit. They conclude that the geology of the esker shows gradual and catastrophic processes.

Based on its anomalous thickness (∼150 m) and stratigraphic position above continental-slope mudstone, an upward-coarsening succession consisting in part of tidal rhythmites in the Gleneig Field, offshore Nova Scotia, Canada, is interpreted to be a strongly tide-influenced shelf-margin-delta deposit. A large, funnel-shaped erosional shelf-edge invagination is observed where the paleoshelf edge is resolved in three-dimensional seismic data adjacent to Glenelg. We propose that the delta at Gleneig prograded into a similar shelf-edge invagination within which tidal currents were amplified and wave energy was attenuated. Given that funnel-shaped invaginations (e.g., slope canyon heads, slump scars, fluvially incised knickmarks) are relatively common along modern shelf edges, and that fluvio-deltaic systems should be focused into these topographic lows during regression across the shelf, it seems likely that shelf-edge invaginations play an important but underappreciated role in mediating terrigenous elastic sedimentation during sea-level lowstands. [ABSTRACT FROM AUTHOR]

Abstract: Airborne electromagnetic and high resolution seismic geophysical data provide insight into complex buried valley geometry and internal sedimentary architecture of buried valleys in the Canadian Prairies. Buried valleys with an extent in excess of 20,000 km beneath the Canadian prairie landscape have been previously interpolated using borehole data; however, they provide only limited insight into the geometry and spatial relationships of these valleys. The collected high-quality geophysical datasets, a three-dimensional airborne electromagnetic survey and high resolution seismic profile data provide much greater resolution of buried valley geometry and internal sedimentary architecture of buried valleys. Several generations of valleys at different scales are identified. We interpret multiple erosion surfaces bounding thick diamicton sequences that fill the largest valleys; the youngest valleys are filled with variable sediment types. Three valley morphologies are identified and process origins inferred: 1) regional-scale, extensive, subaerial and pre/interglacial named α-type valley, 2) regional-scale, narrow and mainly proglacial, β-type valley and 3) local-scale, apparently discontinuous, subglacial, γ-type valley. Within the glacial sediment stratigraphy filling α-type valleys are thick diamicton sequences bounded by erosional surfaces. The β-type and γ-type valleys are filled with variable sediment types. The proglacial β valleys erode bedrock and also occur within the α-type valley fill. Conversely, the γ subglacial valleys are observed to crosscut other valleys and may be shallow and wide, or deep and narrow. The reported geophysical datasets supported by borehole data are able to map buried valleys in three-dimensions and hence identify the morphologic and stratigraphic relationships that permit improved constraints on process and erosional origin and fill of buried valleys. Results provide insight into the relationship between valleys formed as part of Tertiary fluvial erosion, multiple glaciations, and glaciofluvial events. These data provide significant insights on the distribution and character of potential groundwater reservoirs in Prairie regions. [Copyright &y& Elsevier]