Major hydrocarbon and groundwater reservoirs are commonly hosted within coarse-grained alluvial deposits that contain a high degree of sedimentary heterogeneity. This paper presents a detailed characterization of the sedimentary heterogeneity of fluvial–deltaic deposits using architectural element analysis (AEA). Sedimentological data collected from outcrop faces exposing Late Quaternary glaciofluvial deposits in southern Ontario, Canada, is recorded in 31 sedimentary logs. These logs are used to identify nine different facies types, including gravel facies (Gm, Gp, Gt), sand facies (Sr, Sp, St, Ss), and fine-grained facies (Fl and Fd). Variations in facies associations and geometries are defined by five architectural elements (AEs): sand complex (SC), gravel sheet (GS), fine-grained sheet (FS), gravel foreset body (GFB), and concave fill (CF) elements. The spatial arrangement of bounding surfaces (first- to fifth-order) and AEs allows the classification of six EAs, which, in this study, are defined as the largest-scale architectural subunits that allow for architectural-based mapping over a large area. EAs delineated in this study are sandy braided-river (EA1), delta-front (EA2), gravelly braided-river to delta-top (EA3), delta-front to lacustrine (EA4), braided-river to deltaic (EA5), and sand-dominated fluvial (EA6). AEA is utilized here to capture three levels of heterogeneity, which allow detailed reservoir characterization based on geometric objects and can be readily used for computer-based modelling. Outcrop analogue studies such as this one provide insight to the geometries of more deeply buried coarse-grained deposits that form potential reservoirs and enhance paleoenvironmental reconstruction of subsurface alluvial deposits in Canada and elsewhere.

Ice sheets that advance upvalley, against the regional gradient, commonly block drainage and result in ice-dammed proglacial lakes along their margins during advance and retreat phases. Ice-dammed glacial lakes described in regional depositional models, in which ice blocks a major lake outlet, are often confined to basins in which the glacial lake palaeogeographical position generally remains semi-stable (e.g. Great Lakes basins). However, in places where ice retreats downvalley, blocking regional drainage, the palaeogeographical position and lake level of glacial lakes evolve temporally in response to the position of the ice margin (referred to here as 'multi-stage' lakes). In order to understand the sedimentary record of multi-stage lakes, sediments were examined in 14 cored boreholes in the Peace and Wabasca valleys in north-central Alberta, Canada. Three facies associations (FAI-III) were identified from core, and record Middle Wisconsinan ice-distal to ice-proximal glaciolacustrine (FAI) sediments deposited during ice advance, Late Wisconsinan subglacial and ice-marginal sediments (FAII) deposited during ice-occupation, and glaciolacustrine sediments (FAIII) that record ice retreat from the study area. Modelling of the lateral extent of FAs using water wells and gamma-ray logs, combined with interpreted outlets and mapped moraines based on LiDAR imagery, facilitated palaeogeographical reconstruction of lakes and the identification of four major retreat-phase lake stages. These lake reconstructions, together with the vertical succession of FAs, are used to develop a depositional model for ice-dammed lakes during a cycle of glacial advance and retreat. This depositional model may be applied in other areas where meltwater was impounded by glacial ice advancing up the regional gradient, in order to understand the complex interaction between depositional processes, ice-marginal position, and supply of meltwater and sediment in the lake basin. In particular, this model could be applied to decipher the genetic origin of diamicts previously interpreted to record strictly subglacial deposition or multiple re-advances.

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Thick till sheets deposited during the Quaternary form significant aquitards in many areas of North America. However, the detailed sedimentary heterogeneity and architecture and depositional history of till units are not well understood. This study utilizes architectural element analysis to delineate the internal sedimentary architecture of the Tiskilwa Formation exposed at two outcrop sections in north-central Illinois, USA. Architectural element analysis facilitates systematic delineation of sedimentary architecture based on the nature of facies contacts and change in facies associations, delineation of unit geometries and understanding of depositional processes at different scales of resolution; making architectural element analysis suitable for the sedimentological analysis and palaeoenvironmental reconstruction of subglacial deposits. Eleven facies types are identified in this study, including sand, gravel and diamict facies that record a suite of subglacial depositional processes. Detailed analysis of facies contacts (bounding surface hierarchy) and change in facies associations allows the delineation of five architectural elements, including coarse-grained lens, coarse-grained sheet, mixed zone, diamict lens and diamict sheet elements. The spatial arrangement and genetic interpretation of elements, and their spatial relationship with fifth-order bounding surfaces, allows the delineation of five larger scale architectural units ('element associations'), which can be mapped in the local study area and record at least three stacked successions of meltwater accumulation and till deposition. The results of this study can be utilized for architectural analysis of till sheets and provide insight to groundwater flow pathways through till in the study area and elsewhere.