463 research outputs found

    Discrimination of rock classes and alteration products in southwestern Saudi Arabia with computer-enhanced LANDSAT data

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    Digital LANDSAT MSS data for an area in the southwestern Arabian Shield were computer-enhanced to improve discrimination of rock classes, and recognition of gossans associated with massive sulphide deposits. The test area is underlain by metamorphic rocks that are locally intruded by granites; these are partly overlain by sandstones. The test area further includes the Wadi Wassat and Wadi Qatan massive sulphide deposits, which are commonly capped by gossans of ferric oxides, silica, and carbonates. Color patterns and boundaries on contrast-stretched ratio color composite imagery, and on complementary images constructed using principal component and canonical analyses transformations, correspond exceptionally well to 1:100,000 scale field maps. A qualitative visual comparison of information content showed that the ratio enhancement provided the best overall image for identification of rock type and alteration products

    Beaufort Formation (Late Tertiary) as Seen from Prince Patrick Island, Arctic Canada

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    The Beaufort Formation, in its type area on Prince Patrick Island, is a single lithostratigraphic unit, a few tens of metres thick, consisting of unlithified sandy deposits of braided rivers. Organic beds in the sand have yielded more than 200 species of plants and insects and probably originated during the Pliocene, when the area supported coniferous forest. This Beaufort unit forms the thin eastern edge of a northwest-thickening wedge of sand and gravel beneath the western part of the island. These largely unexposed beds, up to several hundred metres thick, include the Beaufort unit and perhaps other older or younger deposits. On the islands northeast and southwest of Prince Patrick Island (Meighen Island to Banks Island), the name Beaufort Formation has been applied to similar deposits of late Tertiary age. Most recorded Beaufort beds on these islands are stratigraphically and paleontologically equivalent to the "type" Beaufort, but a few sites that have been called Beaufort (such as Duck Hawk Bluffs and the lower unit at Ballast Brook, on Banks Island) differ stratigraphically and paleontologically from the "type" Beaufort. This paper recommends that these deposits (probably middle Miocene) and others like them be assigned new stratigraphic names and not be included in the Beaufort Formation as now defined. Informal names Mary Sachs gravel (Duck Hawk Bluffs) and Ballast Brook beds are proposed as an initial step. Formal use of the name Beaufort Formation should be restricted to the western Arctic Islands.

    Some Canadians in the Antarctic

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    The note shows that individual Canadians have been involved in every phase of Antarctic exploration and research from 1898 to the present time.Key words: Antarctic, expeditionsMots clés: antarctique, expéditio

    Constraining Ice Advance and Linkages to Paleoclimate of Two Glacial Systems in the Olympic Mountains, Washington and the Southern Alps, New Zealand

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    This thesis investigated marine isotope stage {MIS) 3-2 glacial sequences in the South Fork Hoh River Valley, Washington and the Lake Hawea Valley, New Zealand. Research objectives were to reconstruct the style and timing of ice advance in both areas and to assess the viability of luminescence dating of glacial sediments in various depositional facies and distances from the ice front. This thesis focused on the sedimentology and stratigraphy of surficial and older glacial sequences in the South Fork Hoh and Lake Hawea areas and used OSL and radiocarbon dating techniques to establish age control for the deposits. Specifically, this research identified, described, and dated the stratigraphy of glacial sequences in order to reconstruct ice dynamics. This work also presents updated geomorphic maps for both study areas as an additional way to show ice advance and retreat events recorded in deposited sediment and geomorphic surfaces. The glacial sequence expressed in the Lake Hawea moraine exposure shows four distinct depositional events that represent retreat from an ice position down -valley, re-advance to the Hawea moraine position, and subsequent retreat and deglaciation broadly spanning -32-18 ka. These results document the terminal glacial advance and subsequent retreat in the Lake Hawea Valley and contribute to the wider swath of research studying the last phase of glacial retreat and its connections to climate on the South Island of New Zealand. The Hawea chronology corresponds to other glacial records and paleoclimate reconstructions from the South Island that collectively suggest the commencement of deglaciation at -13 ka. Three late Pleistocene ice positions are preserved in the South Fork Hoh River Valley, here referred to as South Fork 1-3 (SF 1-3). One of these positions has not previously been recognized in this valley or in the mainstem Hoh River Valley. Optically stimulated luminescence (OSL) and radiocarbon (14C) ages are generally consistent throughout the valley. These finding s advocate for a detailed sedimentologic and stratigraphic approach to glacial depos its and questions whether a similar advance or still -stand occurred in other valleys in the region. If so, this may reveal information regarding climate influences on MIS 2 glaciers in the Olympic Mountains. This research also assesses the applicability of OSL dating to glacial deposits in both field areas. Quartz OSL dating was used in the South Fork Hoh study area; however, quartz produced unreliable results in the Hawea study area, so samples were therefore assessed using feldspar methods. The results advocate for a facies-based sampling approach in glacial settings, where better sorted sandy facies and more distal deposits produce better bleached and more reliable age results than other deposits

    Field Museum news.

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    v. 2 (1931

    The Chemicals Between Us: A Geoarchaeological Analysis of a Shell Midden and Patterns of Deposition at the Woodstock Farm Site, Chuckanut Bay, Washington

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    Human settlement of the Gulf of Georgia region by hunter-forager peoples began nearly 5000 years ago, culminating in the familiar Developed Northwest Coast Pattern exhibited in many Marpole Phase archaeological sites beginning 2400 years BP throughout the Gulf of Georgia region. The physical remnants of the intensive shellfish collection and processing that took place on the Northwest Coast are in shell midden deposits: archaeological sites that contain an abundance of discarded shell, bones, lithic tools, and charcoal. The preceding Locarno Beach Phase (3500-2400 BP), particularly in the southern Gulf of Georgia region, is less well understood by archaeologists because of the past academic focus on northern Marpole Phase sites. The Woodstock Farm site (45WH55) is a Locarno Beach Phase shell midden located in the southern Gulf of Georgia, adjacent to Chuckanut Bay in Whatcom County, Washington. Recorded in 1974, the site has been the subject of three Western Washington University archaeological field schools in 2005, 2007, and 2010, and the shell midden identified on the bluff has been the focus of study for past Anthropology graduate theses at WWU. This thesis applies a program of geoarchaeological analysis, including radiocarbon dating, grain size analysis, magnetic susceptibility, and phosphorous values, to twenty five matrix samples from the approximately 4-square meter exposed beach profile shell midden below the bluff of 45WH55. To date, there has been no geochemical or geophysical lab analysis to help interpret the depositional processes that created the complex stratigraphy that characterizes the exposed shell midden in the beach profile at 45WH55. The numerous ash lenses, layers of burnt shell, and charcoal in the shell midden indicates repeating task-specific activities that are more typical of post-Locarno Beach phases. The purpose of these tests was to describe the human activities that created the distinct and repeating layers by combining macro-level observations of the stratigraphy with micromorphological analysis of the collected midden samples. The goals were to distinguish between depositional processes present in the midden and identify archaeological features related to anthropogenic subsistence activities. The results of the laboratory tests supported the hypothesis that the shell midden is the result of in-situ anthropogenic deposition, and not contemporaneous with the Locarno Beach phase portion of 45WH55 on the upper bluff. The midden yielded later Phase dates between 508 BP and 933 BP, indicating over a thousand years of continued use of 45WH55 for intensive shellfish collection and processing. I detected evidence of hearth reuse, which aligns with the intensive, specialized subsistence activities that are expressed in later Phase archaeological sites throughout the Gulf of Georgia. This research will add to our knowledge about the history of occupation of the Woodstock Farm site

    Cryptic Disc Structures Resembling Ediacaran Discoidal Fossils from the Lower Silurian Hellefjord Schist, Arctic Norway

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    The Hellefjord Schist, a volcaniclastic psammite-pelite formation in the Caledonides of Arctic Norway contains discoidal impressions and apparent tube casts that share morphological and taphonomic similarities to Neoproterozoic stem-holdfast forms. U-Pb zircon geochronology on the host metasediment indicates it was deposited between 437 ± 2 and 439 ± 3 Ma, but also indicates that an inferred basal conglomerate to this formation must be part of an older stratigraphic element, as it is cross-cut by a 546 ± 4 Ma pegmatite. These results confirm that the Hellefjord Schist is separated from underlying older Proterozoic rocks by a thrust. It has previously been argued that the Cambrian Substrate Revolution destroyed the ecological niches that the Neoproterozoic frond-holdfasts organisms occupied. However, the discovery of these fossils in Silurian rocks demonstrates that the environment and substrate must have been similar enough to Neoproterozoic settings that frond-holdfast bodyplans were still ecologically viable some hundred million years later

    Groundwater redox conditions at a petroleum contaminated site, Kuils River, South Africa : pathways for BTEX biodegradation

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    Includes bibliographical references (leaves 84-88).A shallow sandy aquifer, contaminated by petrol from an underground storage tank, was studied to determine if intrinsic bioremediation of the hydrocarbons is taking place. Groundwater samples taken from 32 monitoring wells were analysed for NO₃-,NH₄+, Mn²+, Fe²+, SO₄²-, and ΣH₂S. Portable electrodes were used to make field measurements of electrical conductivity, redox potential, and pH. The variation and distribution of these redox-sensitive groundwater constituents show that bioremediation via NO₃- reduction, Fe³+ reduction, and SO₄²- reduction (and possibly methanogenesis in the most reduced part of the plume) is occurring. In some cases redox processes are taking place simultaneously resulting in redox zones that overlap. Iron and sulphate reduction are the dominant processes taking place

    Field Museum news.

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    v. 5 (1934
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