Turner, Derek G.

A priority of the Northwest Territories Geological Survey’s Slave Province Surficial Materials and Permafrost Study is to support and stimulate mineral exploration by providing an improved understanding of ice‐flow history; the distribution, thickness and stratigraphy of surficial materials; and their implications for the interpretation of geochemical and mineralogical data. To facilitate this, a robust exploration data set consisting of kimberlite indicator mineral and geochemical data was compiled, standardized and evaluated for the Lac de Gras (NTS 076D) and Aylmer Lake (NTS 076C) map areas, in the Northwest Territories, in an effort to better inform and focus exploration efforts in the region. The standardization was designed to identify and mitigate differences in analytical results related to sampling and analytical protocols, regional variation and surficial material genesis. These differences were quantified using exploratory data analysis, and then mitigated using a combination of data levelling, filtering and separation into subpopulations consisting of comparable data. The standardized data were evaluated using anomaly thresholds unique to each data set, resulting in a general increase in the discernibility of dispersal patterns when compared to the original data. This report also identifies sampling and analytical protocols that yielded the best analytical results, and several regions within the study area where the present publicly available data do not adequately represent the potential for economic mineralization.

Quaternary glacial and non-glacial sediment exposed at White River and Silver Creek provide a record of environmental change in southwest Yukon for much of the late- Middle to Late Pleistocene. Eighteen sites at White River, located beyond the marine oxygen isotope stage (MIS) 2 glacial limit, contain thick accumulations of till, loess, peat, gravel and glaciolacustrine silt and clay, with tephras, paleosols, plant and insect macrofossils and large mammal fossils. Radiocarbon ages and eleven tephra beds constrain two tills to MIS 4 and 6. These tills correlate to the Gladstone and Reid glaciations and represent the penultimate and maximum all-time limits of the St. Elias lobe of the northern Cordilleran Ice Sheet. Two peat beds located between these tills indicate that interglacial conditions existed in the area during MIS 5e and 5a. Pond sediment deposited during mid-MIS 5 suggests that the sites were covered by an open birch tundra at this time. The MIS 3/2 transition was marked by a treeless, dry steppe- tundra populated by mammoth, horse and bison. The eleven Silver Creek sites, located ~200 km up-ice, contain a similar record of glacial and non-glacial sediment. Infrared-stimulated luminescence (IRSL) and radiocarbon dating constrain the glacial deposits at these sites to MIS 2, 4, either MIS 7 or 6, and to two Early to Middle Pleistocene, Pre-Reid glaciations. Tilting of glaciolacustrine beds of up to 1.9 mm/yr may be from uplift along the Denali fault since MIS 7. Pollen and macrofossils analyses from overlying MIS 3-aged sediment suggest that the environment was dominated by herbs and forbs, with few shrubs and almost no tree pollen at this time. Combined, the White River and Silver Creek sites contain a record of glacial and non-glacial conditions in southwest Yukon since the Middle Pleistocene. The glacial limits in southwest Yukon are markedly different from those in central Yukon. In southwest Yukon, the glacial limits are closely-spaced and were more extensive in the Middle to Late Pleistocene than in the Late Pliocene and Early Pleistocene. In central Yukon, glacial limits are separated by up to 300 km and were most extensive in the latest Pliocene and Early Pleistocene. This suggests that different forcing mechanisms controlled the extents of the St. Elias and Selwyn lobes during successive glaciations. Boundary conditions such as varying substrates, topography, moisture pathways and atmospheric circulation likely had a greater affect than tectonics and sea level on these glacial limits throughout the Plio-Pleistocene.

The Quaternary geology of Howard’s Pass was studied by creating a 1:50 000- scale terrain inventory map of the area and examining the ice-flow history of the region. Four stages of ice flow occurred in Howard’s Pass during the late Wisconsinan McConnell glaciation. The first stage is marked by ice growth from local cirques. During the second stage, an ice divide developed east of the Nahanni River, with ice flowing southwest across Howard’s Pass. During continued ice sheet growth in stage 3, the ice divide either migrated or a second divide grew to the southwest in the Logan Mountains and ice flowed northward across the study area. Stage 4 is marked by deglaciation and topographically controlled ice-flow. This last phase of ice-flow is the most important for drift prospecting in the valley bottoms. Conversely, drift transport directions at higher elevation are likely remnant from earlier stages of ice-flow. To investigate the potential of till and mobile-metal-ion geochemistry for drift prospecting in Howard’s Pass, a survey was conducted over a known deposit. The promising results from this survey suggest that these are possible tools for future exploration in other drift-covered areas of Howard’s Pass.

Four stages of ice-flow occurred in Howard’s Pass during the late Wisconsinan McConnell glaciation. The first stage is marked by ice growth from local cirques. During the second stage, an ice divide developed east of the Nahanni River, with ice flowing southwest across Howard’s Pass. Ice sheet growth continued during stage 3 and the ice divide migrated southwest into the Logan Mountains. At this time ice flowed northward across the study area. Stage 4 is marked by deglaciation and more topographically influenced ice-flow. This last phase of ice-flow is the most important for drift prospecting in the valley bottoms. Conversely, drift transport directions at higher elevation are likely remnant from earlier stages of ice-flow. A mobile-metal-ion survey over a known deposit returned promising results, supporting the potential of this geochemical technique in other drift-covered areas of Howard’s Pass.

This report outlines the landscape hazards mapping project the Northern Climate ExChange and its partners conducted for Ross River, Yukon. The report and accompanying maps can be used to support climate change adaptation planning. <p> Climate change is a significant challenge for northern communities, where the impacts of a warming climate are already having considerable effects (Huntington and Weller, 2005). Many people living in small, isolated communities in northern Yukon are concerned about climate-related risks in their regions. Because adverse impacts are a reality, it is important to implement measures to reduce or moderate the negative effects of climate change – in other words, to implement climate change adaptation strategies.

Recent mineral discoveries made by soil geochemical sampling along ridges and spurs prompted an increase in exploration in the unglaciated Klondike Plateau of west-central Yukon. Extensive and detailed soil sampling campaigns were extended across hillsides and into valleys, where eolian deposits, periglacial processes, and mass movements complicate the collection and interpretation of geochemical data. In support of exploration efforts, property-scale (1:20 000) surficial geology mapping was completed for several exploration projects to provide more detailed insight than is available in regional-scale (1:50 000) mapping. The culmination of this mapping work is the identification of 12 ‘landform-soil types’ (LSTs) that exhibit recognizable and repetitive patterns in the field and in aerial photographs. The suitability of each LST for different soil geochemical sampling methods and interpretation strategies depends on its soil depth, permafrost depth, surface organic thickness, loess thickness, transport distance, and type of geochemical anomaly. Conventional hand auger sampling is well suited to LSTs with residual or colluvial soils with deep or no permafrost (i.e., LSTs 1, 2, 10, 11, and 12). Power auger sampling is best suited to loess-rich colluvial soils with shallow permafrost (i.e., LSTs 3, 4, and 5), although resulting geochemical signatures may be affected by unmineralized rock fragments pulverized during augering. Reverse circulation or rotary air blast drilling, or deep- penetrating geochemical methods, may be necessary in areas of thick organics or transported cover (i.e., LSTs 6, 7, 8 and 9). The LST classification is applied retrospectively to the Coffee Gold Project to explain soil anomalies that represent geochemical dilution by loess, colluvial dispersion, and halos overlying bedrock mineralization. Application of the LST classification to the Snowcap Project reveals similarities and differences in geochemical data derived from samples collected with a mattock, hand auger, and power auger, in relationship to different LSTs.

Chapter: The natural landscape of the North Shore of Vancouver is a mountainous one extending from sea level to ~1400 m. Land below ~400 m has been undergoing increasing urbanization since the 1950s. Development has encroached on areas subject to natural hazards such as floods, debris flows, slope failures, and coastal inundation. We will visit examples of these urban hazards, discuss problems of hazard identification in a forested landscape, and review urban planning and engineering responses to hazard management. Book: This volume, prepared for the 126th GSA Annual Meeting in Vancouver, Canada, offers guides to trips in the Cascadia subduction zone. The active tectonism of the region has had a profound effect on the bedrock and surficial geology of the area, and on human interactions with the geologic environment. These themes are reflected in the trips associated with the meeting. Trip topics relate to bedrock geology, volcanism and Cordilleran glaciation and deglaciation, as well as human interaction with the natural environment. The trips that discuss human interaction cover archaeology, natural hazards and the urban environment, as well as the role that local geology and tectonism have played in shaping colonization of the region since the last glaciation. The field guide volume has something for everyone!

This report outlines the landscape hazards mapping project the Northern Climate ExChange and its partners conducted for Faro, Yukon. The report and accompanying maps can be used to support climate change adaptation planning. <p> Climate change is a significant challenge for northern communities, where the impacts of a warming climate are already having considerable effects (Huntington and Weller, 2005). Many people living in small, isolated communities in northern Yukon are concerned about climate-related risks in their regions. Because adverse impacts are a reality, it is important to implement measures to reduce or moderate the negative effects of climate change – in other words, to implement climate change adaptation strategies.

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.

Sedimentary deposits from two Middle to Late Pleistocene glaciations and intervening non-glacial intervals exposed along the White River in southwest Yukon, Canada, provide a record of environmental change for much of the past 200 000 years. The study sites are beyond the Marine Isotope stage (MIS) 2 glacial limit, near the maximum regional extent of Pleistocene glaciation. Non-glacial deposits include up to 25 m of loess, peat and gravel with paleosols, pollen, plant and insect macrofossils, large mammal fossils and tephra beds. Finite and non-finite radiocarbon dates, and twelve different tephra beds constrain the chronology of these deposits. Tills correlated to MIS 4 and 6 represent the penultimate and maximum Pleistocene glacial limits, respectively. The proximity of these glacial limits to each other, compared to limits in central Yukon, suggests precipitation conditions were more consistent in southwest Yukon than in central Yukon during the Pleistocene. Conditions in MIS 5e and 5a are recorded by two boreal forest beds, separated by a shrub birch tundra, that indicate environments as warm or warmer than present. A dry, treeless steppe-tundra, dominated by Artemisia frigida, upland grasses and forbs existed during the transition from late MIS 3 to early MIS 2. These glacial and non-glacial deposits constrain the glacial limits and paleoenvironments during the Middle to Late Pleistocene in southwest Yukon. Abstract Copyright (2013) Elsevier, B.V.