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The Sheahan Diamond Literature Reference Compilation - Scientific and Media Articles based on Major Keyword - Glaciology
The Sheahan Diamond Literature Reference Compilation is compiled by Patricia Sheahan who publishes on a monthly basis a list of new scientific articles related to diamonds as well as media coverage and corporate announcements called the Sheahan Diamond Literature Service that is distributed as a free pdf to a list of followers. Pat has kindly agreed to allow her work to be made available as an online digital resource at Kaiser Research Online so that a broader community interested in diamonds and related geology can benefit. The references are for personal use information purposes only; when available a link is provided to an online location where the full article can be accessed or purchased directly. Reproduction of this compilation in part or in whole without permission from the Sheahan Diamond Literature Service is strictly prohibited. Return to Diamond Keyword Index
Sheahan Diamond Literature Reference Compilation - Scientific Articles by Author for all years
Each article reference in the SDLRC is tagged with one or more key words assigned by Pat Sheahan to highlight the main topics of the article. In an effort to make it easier for users to track down articles related to a specific topic, KRO has extracted these key words and developed a list of major key words presented in this Key Word Index to which individual key words used in the article reference have been assigned. In most of the individual Key Word Reports the references are in crhonological order, though in some such as Deposits the order is first by key word and then chronological. Only articles classified as "technical" (mainly scientific journal articles) and "media" (independent media articles) are included in the Key Word Index. References that were added in the most recent monthly update are highlighted in yellow.
Glaciology is a broad inter-disciplinary term that takes the emergence and disappearance of glaciers, namely ice on the surface of the earth, as its focus. Articles dealing with the rise and fall if ice sheets as well as climatology issues are tagged by this keyword. The history of the earth's climate, such as the "snowball earth" phenomenon, is not relevant to diamonds, but the effect of glaciers, better described as "ice sheets", on kimberlite pipes or dykes exposed at the surface, is veyr relevant to diamond exploration. When a glacier (ice sheet) flows over the earth's surface, it picks up loose material such as boulders, which become the equivalent of garnets stuck on a piece of paper, namely sandpaper. As the ice sheet flow, its "sandpaper" base scrapes the country rock. When it encounters relatively softer material, such as what kimberlites typically are when erupted into an Archean terrain, the ice sheet preferentially gouges out the kimberlite pipe. The gouged up kimberlite material becomes part of the ice sheet's "sandpaper" base, and gets dragged along by the ice sheet. When climate change stalls the buildup of ice, the ice sheet stops flowing. As it melts, it drops the components of its "sandpaper" base. The result is a "train" of "kimberlite indicator minerals" emanating from the exposed kimberlitic source. An exploration strategy of grid based regional till sampling whereby the heavy minerals are isolated and analyzed as to mineral type and composition can reveal a train of indicator minerals that terminates at or near the source. While some of the glaciology articles deal only with the earth's climate history, others deal with the behavior of glaciers. This is relevant to diamond exploration because glacial flow direction can be complex over time and undermine the exploration model of a linear train of indicator minerals from the source.
A quantified method for the study of non-fossiliferous clastic formations, pre-Pan African sandstone from Central Africa and the northern Democratic Republic Congo.
Journal of African Earth Sciences, Vol. 31, 2, pp. 263-84.
Central Africa, Democratic Republic of Congo, Zaire
Ventura Santos, R., Souza de Alvarenga, C.J., Babinski, M., Ramos, M.L.S., Cukrov, N., Fonsec, M.A., Da Norbrega
Carbon isotopes of Mesoproterozoic Neoproterozoic sequences from southern Sao Francisco craton and Aracuai Belt, Brazil: paleogeorgraphic implications.
Journal of South American Earth Sciences, Vol. 18, 1, Dec. 30, pp. 27-39.
Science Advance AEON and Earth Stewardship Science Research Institute, Nelson Mandela Metropolitan Univerisity, 13p.
Technology
Glacial remnants, exosphere, silica pipes
Abstract: Estimates of ocean temperatures on Earth 3.5 billion years ago (Ga) range between 26° and 85°C. We present new data from 3.47- to 3.43-Ga volcanic rocks and cherts in South Africa suggesting that these temperatures reflect mixing of hot hydrothermal fluids with cold marine and terrestrial waters. We describe fossil hydrothermal pipes that formed at ~200°C on the sea floor >2 km below sea level. This ocean floor was uplifted tectonically to sea level where a subaerial hydrothermal system was active at 30° to 270°C. We also describe shallow-water glacial diamictites and diagenetic sulfate mineral growth in abyssal muds. These new observations reveal that both hydrothermal systems operated in relatively cold environments and that Earth’s surface temperatures in the early Archean were similar to those in more recent times.
Abstract: Deciphering erosion rates over geologic time is fundamental for understanding the interplay between climate, tectonic, and erosional processes. Existing techniques integrate erosion over different time scales, and direct comparison of such rates is routinely done in earth science. On the basis of a global compilation, we show that erosion rate estimates in glaciated landscapes may be affected by a systematic averaging bias that produces higher estimated erosion rates toward the present, which do not reflect straightforward changes in erosion rates through time. This trend can result from a heavy-tailed distribution of erosional hiatuses (that is, time periods where no or relatively slow erosion occurs). We argue that such a distribution can result from the intermittency of erosional processes in glaciated landscapes that are tightly coupled to climate variability from decadal to millennial time scales. In contrast, we find no evidence for a time scale bias in spatially averaged erosion rates of landscapes dominated by river incision. We discuss the implications of our findings in the context of the proposed coupling between climate and tectonics, and interpreting erosion rate estimates with different averaging time scales through geologic time.
Abstract: This article provides concise documentation of the ongoing retreat of glaciers, along with the implications that the ice loss presents, as well as suggestions for geoscience educators to better convey this story to both students and citizens. We present the retreat of glaciers—the loss of ice—as emblematic of the recent, rapid contraction of the cryosphere. Satellites are useful for assessing the loss of ice across regions with the passage of time. Ground-based glaciology, particularly through the study of ice cores, can record the history of environmental conditions present during the existence of a glacier. Repeat photography vividly displays the rapid retreat of glaciers that is characteristic across the planet. This loss of ice has implications to rising sea level, greater susceptibility to dryness in places where people rely upon rivers delivering melt water resources, and to the destruction of natural environmental archives that were held within the ice. Warming of the atmosphere due to rising concentrations of greenhouse gases released by the combustion of fossil fuels is causing this retreat. We highlight multimedia productions that are useful for teaching this story effectively. As geoscience educators, we attempt to present the best scholarship as accurately and eloquently as we can, to address the core challenge of conveying the magnitude of anthropogenic impacts, while also encouraging optimistic determination on the part of students, coupled to an increasingly informed citizenry. We assert that understanding human perturbation of nature, then choosing to engage in thoughtful science-based decision-making, is a wise choice. This topic comprised “Savor the Cryosphere,” a Pardee Keynote Symposium at the 2015 Annual Meeting in Baltimore, Maryland, USA, for which the GSA recorded supporting interviews and a webinar.
Abstract: The Archean-Proterozoic transition was among the most important in geological history for it includes evidence of establishment of ‘modern-style’ plate tectonics, unprecedented paleoclimatic upheavals, and oxygenation of the atmosphere. The early Paleoproterozoic sedimentary record includes evidence of the world's first widespread glacial episodes, which have come to be known as the ‘Huronian Glacial Event’. None of these important changes coincides precisely with the accepted date of 2.5?Ga for the ‘boundary’ between the two great Precambrian eons. Rather, the geological record contains evidence of gradual transitions over many millions of years. For example the Archean sedimentary record in areas such as South Africa includes evidence of stable conditions (e.g. the Pongola Supergroup) that were not achieved in the Laurentian craton until much later during the Paleoproterozoic Era. The Pongola Supergroup in South Africa contains some of the world's oldest (c. 2.9?Ga) but locally developed glacial deposits. Many of these important changes are now considered to have been gradual and oscillatory in nature, including evidence of ‘whiffs of oxygen’ in Archean rocks, long before the Paleoproterozoic Great Oxidation Event. Oxidation of the oceans was also a long and extremely complex process, the details of which are still poorly understood. Glaciations near the beginning of the Paleoproterozoic Era have been considered by some to have been world-spanning ‘snowball Earth’ events. Repeated Huronian glaciations were probably brought about by weathering of Lauroscandia, the world's first ‘supercraton’, controlled by episodic rift-related uplifts during its disintegration. Among these glaciations only the third, represented by the Gowganda Formation and equivalents, was widespread throughout Lauroscandia. Because the two older glaciogenic units are known from only two locations in North America, their formation and preservation were probably controlled by local tectonic events. In like fashion, Paleoproterozoic glaciogenic units in South Africa and Western Australia appear to be local deposits from mountain glaciers formed during periods of tectonically generated (compressional?) uplift. The restricted distribution and diachronous nature of such tectonic events, and associated glaciogenic deposits, cast doubt on the viability of attempts at global correlations of individual Paleoproterozoic glaciogenic formations and on the existence of a Paleoproterozoic (or Neoproterozoic?) snowball Earth.
Yellowknife Forum NWTgeoscience.ca, abstract volume p. 9-10.
Canada, Northwest Territories
eskers
Abstract: Eskers are long ridges of glaciofluvial sand and gravel frequently sampled during mineral exploration campaigns. Sampling of the 700 km long Exeter Lake esker by Chuck Fipke and Stu Blusson in the 1980s led directly to the discovery of the Lac De Gras kimberlite field and establishment of the diamond industry in the Northwest Territories. Despite their significant role in mineral exploration, the details surrounding eskers formation remain controversial (e.g. long-conduit vs. short-conduit models). In my coming research I will use a combination of geomorphological and provenance data to gain insight into the nature of the Exeter Lake esker and the origin of its sediment to help further define the parameters surrounding esker formation and their application in the mining industry. The geomorphology of the esker will be characterized in ArcMap using (1) the new Arctic DEM (2 m resolution), supplemented by (2) aerial imagery (3) GoPro footage of the entire esker collected during a low-level fly-over, (4) ground observations and short foot traverses made at regularly spaced intervals, and (5) locally collected drone footage. Morpho-sedimentary building block elements of the esker system will be identified and interpreted. Esker provenance will be studied using two sample suites. The first suite (112 samples) was collected at coarsely spaced intervals (15-20 km) along the entire length of the esker and contains pared till and esker-ridge samples from both the pebble and finer fractions. These samples will be used to ascertain whether dispersal trains—such as those emanating from the Dubawnt Supergroup—extend the entire length of the esker, considerably overshooting the till dispersal trains from which they were sourced, or whether they are more local in scale. Mud fractions (<63 microns) will be analyzed geochemically; this fraction has never been analyzed previously in similar studies, but could be more indicative of subglacial stream length. Zircon grains from the sand fraction will be analyzed using uranium-lead dating and correlated to diversely aged rock units along the esker system. Finally, the lithology of the pebbles will be analyzed and compared against previously mapped bedrock lithologies along the esker transect. The second suite (62 samples) was collected at closely spaced intervals (300-600 m) from various geomorphological expressions of the greater esker system near the edge of the Lac de Gras kimberlite indicator mineral (KIM) plume, as defined in the KIDD database. KIM concentrations from the samples will be compared with one another, and if the KIM train in the esker considerably overshoots that in the till, a long-conduit model may be more likely. Additionally, by comparing multiple expressions of the esker system any bias in the concentration of KIMs should be detected. Due to the novel approach and large dataset this study has the potential to provide considerable insight into the nature of esker systems and how they are deposited. With this knowledge, mining and exploration companies will be able reassess their esker datasets backed by a scientifically robust exploration model.
Journal of Maps ( Taylor & Francis) on linkedin, Vol. 14, 2, pp. 476-485. pdf
United States, Canada
Glaciation, geomorphology, map
Abstract: 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.
