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We present a detailed cryostratigraphic reconstruction of the degradation and recovery of near-surface permafrost in the southern Klondike goldfields, central Yukon Territory. Two ice-rich layers are recognized in near-surface permafrost and attributed to thermal impacts following vegetation disturbance. At an undisturbed forest site, the base of the modern active layer is stable. At an adjacent site, where a late twentieth century disturbance of surface vegetation and permafrost degradation occurred, there is evidence of recovery in the form of aggradation (upward shift) of the permafrost table following limited vegetation succession. Underlying both the undisturbed forest and the late twentieth century disturbance is an older thaw unconformity corresponding to a thaw depth of ∼2 m, likely associated with early twentieth century (gold rush era) impacts. Field and air photo surveys allow identification of the nature of the disturbances, while a chronology of the surface disturbance has been established using age estimates from tree rings, and the presence of tritium and post-bomb 14C from organic samples within aggradational ice. Collectively, these data underscore the importance of vegetation cover in maintaining ground temperatures in the discontinuous permafrost zone and suggest that, at least at the study site in recent decades, permafrost shows the potential to recover from disturbance in the modern climatic regime of the region.

The ∼470 Ma Ammonoosuc Volcanics of the Bronson Hill terrane of New Hampshire have back-arc basin basalt compositions. Major and trace element compositions compare favorably to coeval volcanic rocks in the Miramichi Highlands of New Brunswick and the Munsangan and Casco Bay volcanics of Maine, back-arc basin basalts of known peri-Gond- wanan origins. Additionally, the Ammonoosuc Volcanics have Nd and Pb isotopic compositions indicative of peri-Gond- wanan provenance. Thus, the Ammonoosuc Volcanics correlate with Middle Ordovician, peri-Gondwanan, Tetagouche- Exploits back-arc rocks of eastern New England and Maritime Canada. This correlation indicates that the Red Indian Line, the principle Iapetus suture, lies along the western margin of the Bronson Hill terrane. However, the younger (∼450 Ma) Oliverian Plutonic Suite rocks that intruded the Ammonoosuc Volcanics, forming domes along the core of the Bronson Hill anticlinorium, have Laurentian isotopic signatures. This suggests that the Ammonoosuc Volcanics were thrust westwardly over the Laurentian margin, and that Laurentian basement rocks are present under the Bronson Hill terrane. A plausible ex- planation for these relationships is that an easterly dipping subduction zone formed the Ammonoosuc Volcanics in the Tetagoughe-Exploits oceanic tract, just east of the coeval Popelogan arc. With the closure of the Iapetus Ocean, this terrane was thrust over the Laurentian margin. Subsequent to obduction of the Ammonoosuc Volcanics, subduction polarity flipped to the west, with the Oliverian arc resulting from a westerly dipping subduction zone that formed under the Taconic Orog- eny-modified Laurentian margin. Resume : Les roches volcaniques Ammonoosuc, ∼470 Ma, du terrane de Bronson Hill au New Hampshire ont des compo- sitions de bassins basaltiques d'arriere-arc. Les compositions en elements majeurs et traces se comparent favorablement aux roches volcaniques contemporaines des terres hautes de Miramichi au Nouveau-Brunswick et les roches volcaniques de Munsangan et de Casco Bay au Maine, des bassins basaltiques d'arriere-arc d'origine peri-gondwanienne connue. De plus, les roches volcaniques Ammonoosuc ont des compositions d'isotopes de Nd et de Pb qui indiquent leur provenance peri- gondwanienne. Ainsi, les roches volcaniques Ammonoosuc sont correlees avec les roches d'arriere-arc Tetagouche-Exploits, Ordovicien moyen peri-Gondwana, de l'est de la Nouvelle-Angleterre et des provinces maritimes canadiennes. Cette correla- tion signifie que la ligne Red Indian, la principale suture Iapetus, se situe le long de la bordure ouest du terrane de Bronson Hill. Toutefois, les roches de la suite plutonique Olivierian, plus jeune (∼450 Ma), formant des domes le long du cœur de l'anticlinorium Bronson Hill, ont des signatures isotopiques laurentiennes. Cela suggere que les roches volcaniques Ammo- noosuc aient ete chevauchees vers l'ouest par-dessus la bordure laurentienne et que les roches du socle laurentien se retrou- vent sous le terrane de Bronson Hill. Une explication plausible pour ces relations est qu'une zone de subduction a pendage vers l'est a forme les roches volcaniques Ammonoosuc dans l'etendue oceanique Tetagouche-Exploits, tout juste a l'est de l'arc Popelogan contemporain. Avec la fermeture de l'Ocean Iapetus, ce terrane a ete chevauche par-dessus la bordure lau- rentienne. Apres l'obduction des roches volcaniques Ammonoosuc, la polarite de la subduction a bascule vers l'ouest; l'arc Oliverian proviendrait d'une zone de subduction a faible pendage vers l'ouest qui s'est formee sous la bordure laurentienne modifiee par l'orogenese taconienne. (Traduit par la Redaction)

This study is centred on the Bonaparte Lake map area located in the southern Interior Plateau of south-central British Columbia. The reconstruction of the Late Wisconsinan glacial history of this part of the southern sector of the Cordilleran Ice Sheet incorporates (i) the analysis and interpretation of landforms of various scales, (ii) the sedimentology and stratigraphy of glacial sediments, and (iii) the geochemical and mineralogical composition of till and analysis of regional glacial dispersal of these components. The onset of the last glacial event was initiated by ice advancing westerly and southwesterly into the study area from an alpine source region located in the Cariboo Mountains. As glaciation intensified, ice from the Coast Mountains coalesced with the Cariboo Mountain ice over the Interior Plateau and developed into an ice divide around 52° north latitude, which resulted in ice flow to be diverted to a southerly direction over the study area. The two dominant ice-flow directions produced palimpsest dispersal that was measured by three tracers in till including thorianite grains and terbium concentrations in the heavy mineral fraction, and granitoid pebble percentage. The two main phases of ice flow identified within our study area have significant implications for mineral exploration that uses mineral tracing in glacial sediments, especially in the area underlain by the highly prospective Quesnel Terrane.

Combined mapping, U–Pb isotope dilution – thermal ionization mass spectrometry (ID–TIMS) geochronology and geochemical studies in Harvey-Cardiff domain in the western Composite Arc Belt reveal the presence of a long-lived magmatic–metamorphic history between 1290 and 1030 Ma. Following intrusion of gneissic tonalite of the Anstruther and Burleigh gneiss complexes at ca. 1290 Ma, diorite of the Salmon Burn intrusive complex was emplaced at 1242.1 ± 1.1 Ma. A potassium-feldspar megacrystic monzogranite in the Salerno Creek deformation zone that forms the boundary between Harvey-Cardiff domain and Bancroft terrane was emplaced at 1211.3 ± 1.5 Ma, similar to the 1220 ± 1.6 Ma old Junction pluton and a previously reported age of ca. 1229 Ma from another Methuen suite granite in the domain. All three ages are 20 to 30 million years younger than Methuen suite ages elsewhere in the Composite Arc Belt (1250–1240 Ma). Deformation along the Salerno Creek deformation zone is constrained between 1211 Ma, the age of the megacrystic monzogranite, and 1050 Ma, the age of titanite grains from the Salmon Burn intrusive complex and a late alkalic dike. A monzogranite of the newly recognized Catchacoma granite suite yielded an age of 1067 ± 3.7 Ma, similar to the 1059.2 ± 1.6 Ma age obtained from the Cavendish pegmatite vein. These ages suggest a temporal link between late granite and pegmatite emplacement in Harvey-Cardiff domain. Metamorphic zircon, monazite, and titanite ages fall into three clusters (1082–1070, 1063–1045, and 1037–1030 Ma) and may represent a protracted metamorphic event or reflect distinct pulses during the Ottawan orogeny.

U–Pb baddeleyite ages and paleomagnetic poles obtained for dykes on Devon Island and Ellesmere Island in the Canadian Arctic and the Thule region of Greenland show that they are associated with the Franklin magmatic event. This study is the only one devoted to Franklin igneous rocks where a primary paleomagnetic remanence and U–Pb age have been obtained from the same rocks. Ages from this study range from 721 to 712 Ma, but paleomagnetic directional data show no clear age progression. The paleomagnetic poles from each of the two regional subsets are significantly different at the 95% confidence level from paleomagnetic results previously published for the Franklin event in the Canadian Shield. The difference in the pole locations can be accounted for, to first approximation, by a simple model of early Cenozoic block rotations among the North American plate, Greenland, and a hypothesized ancient microplate comprising Ellesmere, Devon, Cornwallis, and perhaps Somerset islands. A new grand-mean paleopole for the Franklin event, including restoration of Greenland and the proposed “Ellesmere microplate” to North America, is located at (8.4°N, 163.8°E, A95 = 2.8°, N = 78 sites) and is a key pole for Neoproterozoic supercontinent reconstructions.

The relatively subdued topography of British Columbia’s northern interior plains does not reflect the irregular, buried bedrock surface. Many areas have been deeply incised by preglacial rivers that have subsequently filled with a succession of Quaternary sediments. In this study, oil and gas petrophysical logs, drill chip samples, water well logs, and surficial and bedrock outcrop maps were used to model the bedrock topography of the Fontas map sheet (NTS 94I). The modelled data produced several depressions that are interpreted to be paleovalleys incised into the soft Cretaceous shale of the Fort St. John Group. Understanding the geometry, thickness, and stratigraphy of the drift has considerable safety and resource management implications as artesian aquifers and natural gas were encountered in the drift during oil and gas well drilling. Four major paleovalleys are suggested. The most dominant paleovalley (Kotcho–Hoffard Paleovalley) is located south of the Etsho Plateau and trends west-southwest across the map area. A second depression occurs within the loop of the Hay River and may be a tributary of the Kotcho–Hoffard Paleovalley that links with the Rainbow Paleovalley in Alberta. A third paleovalley is mapped south of the Sahtaneh River (Kyklo Creek Paleovalley) and is either a tributary to, or crosscuts the Kotcho–Hoffard Paleovalley. The Niteal Creek Paleovalley is located between the Fontas and Sikanni Chief rivers. Its geometry is speculative as there are sparse data, but it may be a tributary of the Kotcho–Hoffard Paleovalley.

Exposures in the Prophet River valley in northeast British Columbia provide a unique glimpse into the Quaternary history of the northwest Canadian Boreal Plains. The region shows evidence of Late Wisconsinan Laurentide glaciation in the form of widespread till, containing abundant erratic clasts derived from the Canadian Shield. Vertical sections along the Prophet River expose non-glacial and advance glacial sediments below this till. Pre-Late Wisconsinan non-glacial or interglacial floodplain sediments are interbedded with fluvial gravels at many sites. Macrofossils within horizontally laminated organic-rich black clay and silt indicate deposition on the floodplain of the paleo-Prophet River within an oxbow lake. The climate during deposition is interpreted to be similar to present, supporting a dominantly spruce forest. Wood obtained from eight sites provided non-finite radiocarbon ages, and one sample provided an age of 49 300 ± 2000 BP, which is also considered non-finite. Glaciolacustrine clays and silts, deposited during impoundment of eastward-flowing drainage by the advance of the Laurentide Ice Sheet (LIS) in the Late Wisconsinan, overlie the non-glacial sediments throughout the valley. A blanket of clast-poor, clay-rich till up to 20 m thick, and deposited by the LIS, drapes the glaciolacustrine sediments. Since deglaciation, the Prophet River has incised the valley and formed fluvial terraces at different levels above the modern river.

This is the third and final compendium of papers on the Abitibi-Grenville Lithoprobe transect. Much of the focus is on the Grenville Province, complementing the previous compendia which focussed on the Abitibi subprovince. There are, however, papers on the Abitibi subprovince concerning detailed gravity studies, granitoid geochemistry, and fluid evolution. The evolution of the Grenvillian orogen is examined in a series of papers combining observations from seismic studies, isotopic characteristics, geochronology, petrology, and structural geology. There are papers discussing the heat flux, teleseismic attributes, and electromagnetic characteristics across the entire region of the Lithoprobe transect, and an overview of Lithoprobe studies of the Sudbury region. A synthesis paper contrasts the Archean tectonic evolution of the Abitibi subprovince with the Mesoproterozoic evolution of the Grenville Province.

The municipality of Metropolitan Toronto (area 480 km2, population 2.15 million) is centrally located on the Late Pleistocene sedimentary infill of the Laurentian Channel, a broad bedrock low up to 115 km wide connecting the Huron and Ontario basins. This channel forms part of a relict (late Tertiary?) drainage network (the Laurentian River) modified by Pleistocene glacial erosion and infilled by over 100 m of glacial and interglacial sediments. The subsurface stratigraphy of the channel fill below Metropolitan Toronto has been established from many different data sources and is depicted, in this paper, as a series of cross sections with a total length of nearly 105 km.The subsurface stratigraphy has been divided, provisionally, into five depositional complexes, which have been mapped in the subsurface along several transects. These are (1) a glacial complex of Illinoian (?) age, (2) a lacustrine complex of Sangamon Interglacial and earliest Wisconsinan sediments (120 000 – 75 000 BP?), (3) a glaciolacustrine – lacustrine complex spanning the Early and Mid-Wisconsinan (75 000 – 30 000 BP?), (4) a Late Wisconsinan (> 30 000 BP) glacial complex, and (5) a postglacial lacustrine complex (ca. 12 000 BP).The data presented in this paper are significant for applied geological investigations in the heavily urbanized Toronto area and provide new insights into the glacial history of the Ontario Basin, in particular the regional extent of the Laurentide Ice Sheet margin prior to the Late Wisconsinan.

A long, narrow belt of rocks of very high electrical conductivity has been discovered and mapped by means of large arrays of recording magnetometers, over a distance of 1400 km from southeastern Wyoming to the edge of the Canadian Shield in Saskatchewan. Evidence that the conductive belt might be associated with conductive minerals in metamorphosed and fractured rocks in the basement has been discussed in earlier papers. Recent results on the Precambrian geology at both ends of the conductor, in the Churchill Province of the Shield and in southeastern Wyoming, support the hypothesis that the anomaly in electrical conductivity traces a major fracture zone in the lithosphere of Precambrian North America. This paper presents and relates various lines of evidence which together tend to substantiate such a fracture zone or mobile belt. From the age and composition of rocks near the southern end of the structure, Hills and others suggest that a Proterozoic subduction zone is located there. It is possible that the entire fracture zone from the Southern Rockies to the vicinity of Hudson Bay is a Proterozoic continental collision zone or geosuture.

Uzuakpunwa and Brownlow (1978) have presented an interpretation of a pre-Taconic angular unconformity in western Massachusetts that disagrees significantly with our published conclusions that we derived from abundant detailed mapping in the same area. Their statements and interpretations appear to disregard the data that we published, and we cannot agree with their arguments for a preTaconic unconformit y. Uzuakpunwa and Brownlow include in their paper a regional map of western Massachusetts at a scale of 1:500 000 (their Fig. 1) and a more detailed map of parts of the Blandford and Woronoco quadrangles at a scale of 1:48 000 (their Fig. 2). Nowhere do they indicate how much mapping they have done, in which areas, nor at what scale. Our mapping was done at a scale of 1:24 000 for all the area of their Fig. 1 that pertains to their discussion and was available as quadrangle maps (Hatch and Hartshorn 1968; Chidester et al. 1967; Osberg et al. 1971; Hatch 1969; Hatch et al. 1970; Hatch and Stanley 1976) or as maps in other papers (Stanley 1967,1975; Hatch and Stanley 1973). Uzuakpunwa and Brownlow's maps differ in some important details from ours. They indicate (their Fig. 1) that the "Chester Amphibolite" occurs at a unique stratigraphic horizon and is nearly continuous across Massachusetts from Connecticut to Vermont. Our mapping shows that the Chester is a lens which can be traced for only 10 km along strike, and that no amphibolitelgreenstone extends continuously across the breadth of the state. The amphibolites/greenstones that Uzuakpunwa and Brownlow included in their Chester Amphibolite vary in composition and bedding characteristics, and have very different stratigraphic positions with respect to the other mapped lithologic members of the Rowe Schist. Uzuakpunwa and Brownlow stated (pp. 1941, 1945) that the Chester Amphibolite forms a basal unit to the Moretown Formation. Our mapping shows that rocks above and below the type Chester body are lithically identical and that the distinctively thin bedded, more granulose rocks characteristic of the Moretown Formation are not present below a horizon 200-300 m stratigraphically above the Chester. Where the Chester thins to a feather edge, the schists that are no longer separated by it are indistinguishable. Uzuakpunwa and Brownlow asserted (p. 1943) that "the Rowe Schist is generally exposed west of the western Massachusetts ultramafic belt" and infer that this relationship has stratigraphic importance. Our published maps show that the ultramafic bodies are found at all stratigraphic positions between the base of the Rowe Schist and the lower part of the Moretown Formation (see maps and reports listed above). The stratigraphically lowest body of ultramafic rock within the lower Paleozoic section is 200 m above the Hoosac-Rowe contact in the Rowe quadrangle (Chidester et al. 1967). Uzuakpunwa and Brownlow have ignored the stratigraphic redefinitions proposed by Hatch et al. (1966), and have instead adopted a stratigraphy similar to that of Emerson (1898) without any discussion or documentation of their reasons for so doing. Although Emerson (1898) originally mapped the Chester Amphibolite as a single horizon across Massachusetts, on his final (Emerson 1917) presentation of this geology, he showed the Chester as being discontinuous, but showed separate formations above and below the Chester (horizon). We

Accurate interpretation of geophysical data, design of safe casing strings for drilling and production operations, and determination of the potential for existence of gas hydrates in and immediately below the permafrost zone are only possible if the thickness of the permafrost zone can be accurately determined.Freezing of interstitial water in soils has little effect on many of the physical properties of the soil, however, large changes in elastic properties and electrical resistivity do result. This makes it feasible to determine the thickness of the permafrost zone using techniques which measure changes in acoustic and electrical properties of the soils adjacent to the wellbore. This paper discusses the characteristic response which occurs as the borehole logging tool passes upwards from unfrozen sediments into the permafrost zone. It is this response which indicates the base of the permafrost zone and allows determination of permafrost thickness.Conclusive evidence of permafrost thickness and confirmation of permafrost thickness inferred from acoustic and electrical data is obtained from temperature data obtained subsequent to well suspension. Techniques utilized to obtain these temperature data are outlined in this paper.

The erosional impacts of former ice sheets on the low-relief bedrock surfaces of Northern Hemisphere shields are not well understood. This paper assesses the variable impacts of glacial erosion on a portion of Baffin Island, eastern Canadian Arctic, between 68° and 72°N and 66° and 80°W. This tilted shield block was covered repeatedly by the Laurentide Ice Sheet during the late Cenozoic. The impact of ice-sheet erosion is examined with GIS analyses using two geomorphic parameters: lake density and terrain ruggedness. The resulting patterns generally conform to published data from other remote sensing studies, geological observations, cosmogenic exposure ages, and the distribution of the chemical index of alteration for tills. Lake density and terrain ruggedness are thereby demonstrated to be useful quantitative indicators of variable ice-sheet erosional impacts across Baffin Island. Ice-sheet erosion was most effective in the lower western parts of the lowlands, in a west–east-oriented band at around 350–400 m a.s.l., and in fjord-onset zones in the uplifted eastern region. Above the 350–400 m a.s.l. band and between the fjord-onset zones, ice-sheet erosion was not sufficient to create extensive ice-roughened or streamlined bedrock surfaces. The exception — where lake density and terrain ruggedness indicate that ice-sheet erosion had a scouring effect all across the study area — was in an area from Foxe Basin to Home Bay with elevations

The Kamouraska Formation is a quartz-arenitic unit of latest Cambrian – earliest Ordovician age in the Quebec Appalachians that was deposited by hyperconcentrated to concentrated density flows in a meandering submarine canyon on the continental slope bordering the Iapetus Ocean, as outlined in a companion paper. Detailed petrographic study of the quartz arenites of the Kamouraska Formation combined with scanning electron microscopy of grain surface textures suggests that the quartz sands are of eolian origin having been derived from an inland desert or, less likely, a barrier beach dune system. Transport of the mature quartz-arenitic sand onto the shelf and deposition into the deep sea was not accompanied by substantial mixing with material from other sources thus preserving the inherited eolian characteristics. A modern analogue for the eolian interpretation of the deep-sea quartz-arenite beds is as follows: thick, Late Pleistocene eolian sand beds on a modern abyssal plain in the East Atlantic referred to as eolian-sand turbidites that were deposited in the deep sea during glacial sea level lowstands when eolian sand transport to canyon heads was enabled by an exposed and shortened shelf. Similarly, an established sea level lowstand at the Cambro–Ordovician boundary would have facilitated the introduction of eolian sand of the Kamouraska Foundation into canyon heads on the upper slope from where turbidity currents and related density flows were triggered. Correlation of the Kamouraska Formation with the quartz arenites of the Cairnside Formation of Quebec (Keeseville Formation in northern New York State, Nepean Formation in southern Ontario) links the deep-sea deposits with remnants of an inland dune system.

Government geological survey maps and research publications have portrayed the distribution of glacial landforms associated with the advance and retreat of the Laurentide and Cordilleran ice sheets across Alberta at a local, regional, and continental scale. To date, this information has not been systematically synthesized into a single compilation at a consistent scale. Although this original work provided valuable information to constrain reconstructions of former ice sheet extent, configuration, and flow geometry, its derivation primarily from the interpretation of aerial photographs and the Shuttle Radar Topography Mission 90 m digital elevation model (DEM) may result in methodological inconsistencies and spatial biases. These biases, together with challenges associated with geomorphic mapping in densely forested areas of western and northern Alberta limit the usefulness of previous mapping when applied to inversion-based ice sheet reconstructions, which have specific input data demands. Recently, light detection and ranging (LiDAR) DEMs have become increasingly available throughout Alberta. Hill-shaded imagery of these data provides unprecedented geomorphic detail beneath the forest cover and reveals that that the glacial geomorphology of northern and western Alberta is more complex than previously recognized. In this paper, we describe the methodology and geomorphic criteria used to produce a glacial landform map of Alberta using previously published data, supplemented by comprehensive new analysis of high-resolution (2–25 m) DEMs. These include 306 624 km2 of LiDAR imagery, with which it is now possible to verify and where necessary augment previous mapping, particularly across areas with a dense forest cover.

The exposures at the St. Marys Cement Inc. quarry at St. Marys, Ontario, have been studied by geologists since the mid-1950s. This paper summarizes previous and new information collected in 2009, 2010, and 2012 and discusses the record of sediments resting on the bedrock surface that have been exposed during quarry operations. The exposed sediments illustrate the dynamic behavior of the Laurentide Ice Sheet in this area during the Late Wisconsin. Evidence for subglacial meltwater activity, shifting ice-flow directions during till deposition, a local or regional erosion event, possible subaerial exposure, and ice-marginal sedimentation is observed in the sequence of tills and stratified sediments exposed in the quarries. It also highlights how rapid lateral facies changes, complex contact relationships, and steep erosional contacts can prove to be challenging for correlation and extrapolation of subsurface units into three-dimensional stratigraphic models. Fourteen units were identified of which the lower six were deposited during the Nissouri age (Catfish Creek Drift). This included five layers of till deposited by a glacier that alternated from flowing out of the Lake Huron basin to that of a regional flow to the south-southwest. An angular unconformity cuts into these sediments and separates them from a finer-grained sediment sequence (primarily of Port Bruce age) consisting of glaciofluvial gravel, two fine-textured till layers, and rhythmically bedded glaciolacustrine sediments, all overlain by the uppermost till, the Rannoch Till, and Mitchell Moraine ice-marginal fan sediments.

Terraces in the lower Matane River Valley (eastern Quebec, Canada) were studied to describe the stratigraphic architecture of a glacially eroded valley fill. The Matane River Valley hosted a glacial tongue connected with a regional ice cap during the early opening of a calving bay in the modern St. Lawrence Estuary and was subsequently flooded by the Goldthwait Sea as the Laurentide Ice Sheet margin retreated. Stratigraphic, sedimentological, light detection and ranging (LIDAR), and geochemical analyses as well as radiocarbon measurements allowed the identification of four stratigraphic units deposited during and following deglaciation: glacial outwash (unit I), delta bottomsets (unit II), delta foresets (unit III), and fluvial deposits (unit IV). Stable isotope (13C) and C/N ratio values reveal the relative influence of the two end-members (algae and terrestrial plants) on organic matter sources between the stratigraphic units. Climate, major relative sea level fluctuations, and sediment yield are recognized as the main controls on depositional environments in glacially eroded valleys of the northern shore of the Gaspé Peninsula during the Holocene. This paper presents a model of the evolution of the Matane River Valley, which in many points is similar to existing conceptual fjord-valley fill models.

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 heter- ogeneity 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. Resume : Les grands reservoirs d'hydrocarbures et d'eau souterraine sont frequemment situes dans des depots alluviaux agrains grossiers afort degre d'heterogeneite sedimentaire. Cet article presente une caracterisation detaillee de l'heterogeneite sedi- mentaire des depots fluvio-deltaiques effectuee par analyse des elements architecturaux (AEA). Des donnees sedimentologiques recueillies d'affleurements exposant des depots fluvio-glaciaires du Quaternaire tardif dans le sud de l'Ontario, Canada, sont contenues dans 31 diagraphies sedimentaires. Ces diagraphies servent aidentifier neuf differents types de facies, incluant un facies de gravier (Gm, Gp, Gt), un facies de sable (Sr, Sp, St, Ss) et un facies agrain fin (Fi et Fd). Les variations dans les associations de facies et les geometries sont definies selon cinq types d'elements architecturaux (AE) : un complexe de sable (SC), une couche de gravier (GS), une couche agrain fin (FS), un amas frontal de gravier (GFB) et un remplissage concave (CF). L'arrangement spatial des surfaces limitrophes (1er au 5e ordre) et les elements architecturaux permettent une classification de six associations d'elements (EA), lesquels, dans cette etude, sont definis comme etant les sous-unites ala plus grande echelle architecturale permettant de cartographier selon l'architecture sur une grande superficie. Les associations d'elements (EA) definis dans la presente etude sont : riviere sablonneuse anastomosee (EA1), front deltaique (EA2), riviere graveleuse anastomosee asommet d'un delta (EA3), front deltaique alacustre (EA4), riviere anastomosee adeltaique (EA5) et environnement fluvial domine par le sable (EA6). L'analyse des elements architecturaux est utilisee ici pour saisir trois niveaux d'heterogeneite qui permettent une caracterisa- tion detaillee des reservoirs basee sur des objets geometriques et qui peuvent facilement servir pour une modelisation informa- tique. Des etudes analogues d'affleurements telles que celle-ci fournissent des apercus de la geometrie des depots agrains grossiers enfouis aplus grande profondeur, formant des reservoirs potentiels; elles aident ala reconstruction paleoenvironne- mentale des depots alluviaux sous la surface, au Canada et ailleurs. (Traduit par la Redaction)

The paper presents a case study of sediment, termed soft lodgement till (a product of subglacial deposition by active ice), described previously on the basis of macro-evidence from Poland and Canada but not yet studied in detail in one particular site. The till at Anielinek (about 7 m thick) was examined by macroscopic observation, thin section description, and qualitative and quantitative scanning electron microscopy (SEM) analyses. It shows a macroscopic massive structure and overlies a flat top of glaciolacustrine sediments. These sediments form upward intrusions within the till—owing to the existence of reversed density gradients among the deposits—and the upper parts of the intrusions are tilted in consistent directions within the successive parts of the till. Moreover, SEM images also record uniformly oriented microintrusions within this diamictic material. The occurrence of these macro- and microstructures within the successive parts of the till point to an almost continuous process of intrusion during ongoing deposition of the till and to water saturation of the subglacial environment. Such conditions reduced friction of the glacier bed against its substratum, and glacial debris must have been mainly melt-released from the moving glacier base. This process was responsible for deposition of sediment (soft lodgement till) that was immediately and continuously deformed by glacial stress during the ongoing accretion of debris from the glacier base.

This paper presents the results of structural mapping in the Peace River Arch region, obtained by applying a refined trend surface analysis to existing well-log data. Maps generated with the new approach allow for accurate location of formation-top offsets and recognition of faults associated with small, metre-scale offsets. Consequently, new faults were identified in the Mesozoic strata, and faults previously recognized as only offsetting Paleozoic strata were found to extend into the Cretaceous strata but with much smaller formation-top offsets. This provided direct evidence for re-activation of the Dawson Creek Graben Complex (DCGC) during the Cretaceous. An additional structural feature named Clear River Graben was recognized to have affected Permian to Jurassic strata. Relationships among previously interpreted faults were clarified and the structural controls on the DCGC were more accurately evaluated.

Holocene lateral moraines in the Coast Mountains of British Columbia are commonly composed of multiple drift units related to several glacier advances. In this paper, we document lateral moraine stratigraphy at Lillooet Glacier in the southern Coast Mountains. Five tills, separated by laterally extensive paleosols and layers of large woody debris, were found in three cross-sectional exposures through the northeast lateral moraine and two shallow gullies incised into its steep proximal face. Eighteen new radiocarbon ages constrain the timing of five separate advances of Lillooet Glacier: (1) prior to 3000 14C years BP; (2) ~3000 14C years BP; (3) ~2500 14C years BP; (4) ~1700 to 1400 14C years BP; and (5) during the Little Ice Age (LIA), after 470 14C years BP. The Lillooet Glacier chronology is broadly synchronous with other glacier records from the Coast Mountains. These records collectively demonstrate climate variability at higher frequencies during the late Holocene than is apparent from many paleoecological reconstructions. Reconstructions of glacier fluctuations are often hampered by poor preservation of landforms that predate the extensive LIA advances of the latest Holocene. Our results highlight the potential of lateral moraine stratigraphy for reconstructing these earlier events.