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News Article | April 18, 2017
Site: www.chromatographytechniques.com

The massive Kaskawulsh Glacier in northern Canada has retreated about a mile up its valley over the past century. Last spring, its retreat triggered a geologic event at relatively breakneck speed. The toe of ice that was sending meltwater toward the Slims River and then north to the Bering Sea retreated so far that the water changed course, joining the Kaskawulsh River and flowing south toward the Gulf of Alaska. This capture of one river’s flow by another, documented in a study led by the University of Washington Tacoma and published April 17 in Nature Geoscience, is the first known case of “river piracy” in modern times. “Geologists have seen river piracy, but nobody to our knowledge has documented it happening in our lifetimes,” said lead author Dan Shugar, a geoscientist at the University of Washington Tacoma. “People had looked at the geological record — thousands or millions of years ago — not the 21st century, where it’s happening under our noses.” River piracy, also known as stream capture, can happen due to tectonic motion of Earth’s crust, landslides, erosion or, in this case, a change in a glacial dam. The new study documents one of the less-anticipated shifts that can occur in a changing climate. Shugar and co-authors Jim Best at the University of Illinois and John Clague at Canada’s Simon Fraser University had planned fieldwork last summer on the Slims River, a geologically active system that feeds Kluane Lake in the Yukon. When they arrived in August, the river was not flowing. River gauges show an abrupt drop over four days from May 26 to 29, 2016. By late summer, “there was barely any flow whatsoever. It was essentially a long, skinny lake,” Shugar said. “The water was somewhat treacherous to approach, because you’re walking on these old river sediments that were really goopy and would suck you in. And day by day we could see the water level dropping.” The research team puzzled about what to do next. They got permission to use their mapping drone to create a detailed elevation model of the glacier tongue and headwater region. The resulting paper is a geological postmortem of the river’s disappearance. “For the last 300 years, Slims River flowed out to the Bering Sea, and the smaller Kaskawulsh River flowed to the Gulf of Alaska. What we found was the glacial lake that fed Slims River had actually changed its outlet,” Shugar said. “A 30-meter (100-foot) canyon had been carved through the terminus of the glacier. Meltwater was flowing through that canyon from one lake into another glacial lake, almost like when you see champagne poured into glasses that are stacked in a pyramid.” That second lake drains via the Kaskawulsh River in a different direction than the first. The situation is fairly unique, Shugar said, since the glacier’s toe was sitting on a geologic divide. Clague began studying this glacier years ago for the Geological Survey of Canada. He observed that Kluane Lake, which is Yukon’s largest lake, had changed its water level by about 40 feet (12 meters) a few centuries ago. He concluded that the Slims River that feeds it had appeared as the glacier advanced, and a decade ago predicted the river would disappear again as the glacier retreated. “The event is a bit idiosyncratic, given the peculiar geographic situation in which it happened, but in a broader sense it highlights the huge changes that glaciers are undergoing around the world due to climate change,” Clague said. Less input from the Slims River has lowered the water level of Kluane Lake, the largest lake in the Yukon, exposing sediments and creating dust storms.Jim Best/University of Illinois The geologic event has redrawn the local landscape. Slims River crosses the Alaska Highway, and its banks were a popular hiking route. Now that the riverbed is exposed, Dall sheep from Kluane National Park are making their way down to eat the fresh vegetation, venturing into territory where they can legally be hunted. With less water flowing in, Kluane Lake did not refill last spring, and by summer 2016 was about 3 feet (1 meter) lower than ever recorded for that time of year. Waterfront land, which includes the small communities of Burwash Landing and Destruction Bay, is now farther from shore. As the lake level continues to drop researchers expect this will become an isolated lake cut off from any outflow. On the other hand, the Alsek River, a popular whitewater rafting river that is a UNESCO world heritage site, was running higher last summer due to the addition of the Slims River’s water. Shifts in sediment transport, lake chemistry, fish populations, wildlife behavior and other factors will continue to occur as the ecosystem adjusts to the new reality, Shugar said. “So far, a lot of the scientific work surrounding glaciers and climate change has been focused on sea-level rise,” Shugar said. “Our study shows there may be other underappreciated, unanticipated effects of glacial retreat.” The Kaskawulsh Glacier is retreating up the valley because of both readjustment after a cold period centuries ago, known as the Little Ice Age, and warming due to greenhouse gases. A technique published in 2016 by UW co-author Gerard Roe shows a 99.5 percent probability that this glacier’s retreat is showing the effects of modern climate change. “I always point out to climate-change skeptics that Earth’s glaciers are becoming markedly smaller, and that can only happen in a warming climate,” Clague said.


News Article | April 21, 2017
Site: www.futurity.org

A warming climate has melted northern Canada’s Kaskawulsh Glacier so much that the glacier’s “retreat” has changed the course of a nearby river, new research shows. Last spring, the glacier’s retreat triggered the geologic event at relatively breakneck speed. The toe of ice that was sending meltwater toward the Slims River and then north to the Bering Sea retreated so far that the water changed course, joining the Kaskawulsh River and flowing south toward the Gulf of Alaska. This capture of one river’s flow by another, documented in a study published in Nature Geoscience, is the first known case of “river piracy” in modern times. “Geologists have seen river piracy, but nobody to our knowledge has documented it happening in our lifetimes,” says lead author Dan Shugar, a geoscientist at the University of Washington. “People had looked at the geological record—thousands or millions of years ago—not the 21st century, where it’s happening under our noses.” River piracy, also known as stream capture, can happen due to tectonic motion of Earth’s crust, landslides, erosion or, in this case, a change in a glacial dam. The new study documents one of the less-anticipated shifts that can occur in a changing climate. Shugar and coauthors Jim Best at the University of Illinois and John Clague at Canada’s Simon Fraser University had planned fieldwork last summer on the Slims River, a geologically active system that feeds Kluane Lake in the Yukon. When they arrived in August, the river was not flowing. River gauges show an abrupt drop over four days from May 26 to 29, 2016. By late summer, “there was barely any flow whatsoever. It was essentially a long, skinny lake,” Shugar says. “The water was somewhat treacherous to approach, because you’re walking on these old river sediments that were really goopy and would suck you in. And day by day we could see the water level dropping.” The research team puzzled about what to do next. They got permission to use their mapping drone to create a detailed elevation model of the glacier tongue and headwater region. The resulting paper is a geological postmortem of the river’s disappearance. “For the last 300 years, Slims River flowed out to the Bering Sea, and the smaller Kaskawulsh River flowed to the Gulf of Alaska. What we found was the glacial lake that fed Slims River had actually changed its outlet,” Shugar says. “A 30-meter (100-foot) canyon had been carved through the terminus of the glacier,” he continues. “Meltwater was flowing through that canyon from one lake into another glacial lake, almost like when you see champagne poured into glasses that are stacked in a pyramid.” That second lake drains via the Kaskawulsh River in a different direction than the first. The situation is fairly unique, Shugar says, since the glacier’s toe was sitting on a geologic divide. Clague began studying this glacier years ago for the Geological Survey of Canada. He observed that Kluane Lake, which is Yukon’s largest lake, had changed its water level by about 40 feet (12 meters) a few centuries ago. He concluded that the Slims River that feeds it had appeared as the glacier advanced, and a decade ago predicted the river would disappear again as the glacier retreated. “The event is a bit idiosyncratic, given the peculiar geographic situation in which it happened, but in a broader sense it highlights the huge changes that glaciers are undergoing around the world due to climate change,” Clague says. The geologic event has redrawn the local landscape. Slims River crosses the Alaska Highway, and its banks were a popular hiking route. Now that the riverbed is exposed, Dall sheep from Kluane National Park are making their way down to eat the fresh vegetation, venturing into territory where they can legally be hunted. With less water flowing in, Kluane Lake did not refill last spring, and by summer 2016 was about 3 feet (1 meter) lower than ever recorded for that time of year. Waterfront land, which includes the small communities of Burwash Landing and Destruction Bay, is now farther from shore. As the lake level continues to drop researchers expect this will become an isolated lake cut off from any outflow. On the other hand, the Alsek River, a popular whitewater rafting river that is a UNESCO world heritage site, was running higher last summer due to the addition of the Slims River’s water. Shifts in sediment transport, lake chemistry, fish populations, wildlife behavior, and other factors will continue to occur as the ecosystem adjusts to the new reality, Shugar says. “So far, a lot of the scientific work surrounding glaciers and climate change has been focused on sea-level rise,” Shugar says. “Our study shows there may be other underappreciated, unanticipated effects of glacial retreat.” The Kaskawulsh Glacier is retreating up the valley because of both readjustment after a cold period centuries ago, known as the Little Ice Age, and warming due to greenhouse gases. A technique published in 2016 by coauthor Gerard Roe shows a 99.5 percent probability that this glacier’s retreat is showing the effects of modern climate change. “I always point out to climate-change skeptics that Earth’s glaciers are becoming markedly smaller, and that can only happen in a warming climate,” Clague says. Other coauthors are from the University of British Columbia, the University of Colorado, and the University of Ottawa. The University of Washington Royalty Research Fund, Parks Canada, Yukon Geological Survey, the Natural Sciences and Engineering Research Council of Canada, the University of Ottawa, and the University of Illinois funded the research.


News Article | April 17, 2017
Site: www.eurekalert.org

IMAGE:  A close-up view of the ice-walled canyon at the terminus of the Kaskawulsh Glacier, with recently collapsed ice blocks. This canyon now carries almost all meltwater from the toe of... view more The massive Kaskawulsh Glacier in northern Canada has retreated about a mile up its valley over the past century. Last spring, its retreat triggered a geologic event at relatively breakneck speed. The toe of ice that was sending meltwater toward the Slims River and then north to the Bering Sea retreated so far that the water changed course, joining the Kaskawulsh River and flowing south toward the Gulf of Alaska. This capture of one river's flow by another, documented in a study led by the University of Washington Tacoma and published April 17 in Nature Geoscience, is the first known case of "river piracy" in modern times. "Geologists have seen river piracy, but nobody to our knowledge has documented it happening in our lifetimes," said lead author Dan Shugar, a geoscientist at the University of Washington Tacoma. "People had looked at the geological record -- thousands or millions of years ago -- not the 21st century, where it's happening under our noses." River piracy, also known as stream capture, can happen due to tectonic motion of Earth's crust, landslides, erosion or, in this case, changes in a glacial dam. The new study documents one of the less-anticipated shifts that can occur in a changing climate. Shugar and co-authors Jim Best at the University of Illinois and John Clague at Canada's Simon Fraser University had planned fieldwork last summer on the Slims River, a geologically active system that feeds Kluane Lake in the Yukon. When they arrived in August, the river was not flowing. River gauges show an abrupt drop over four days from May 26 to 29, 2016. By late summer, "there was barely any flow whatsoever. It was essentially a long, skinny lake," Shugar said. "The water was somewhat treacherous to approach, because you're walking on these old river sediments that were really goopy and would suck you in. And day by day we could see the water level dropping." The research team puzzled about what to do next. They got permission to use their mapping drone to create a detailed elevation model of the glacier tongue and headwater region. The resulting paper is a geological postmortem of the river's disappearance. "For the last 300 years, Slims River flowed out to the Bering Sea, and the smaller Kaskawulsh River flowed to the Gulf of Alaska. What we found was the glacial lake that fed Slims River had actually changed its outlet," Shugar said. "A 30-meter (100-foot) canyon had been carved through the terminus of the glacier. Meltwater was flowing through that canyon from one lake into another glacial lake, almost like when you see champagne poured into glasses that are stacked in a pyramid." That second lake drains via the Kaskawulsh River in a different direction than the first. The situation is fairly unique, Shugar said, since the glacier's toe was sitting on a geologic divide. Clague began studying this glacier years ago for the Geological Survey of Canada. He observed that Kluane Lake, which is Yukon's largest lake, had changed its water level by about 40 feet (12 meters) a few centuries ago. He concluded that the Slims River that feeds it had appeared as the glacier advanced, and a decade ago predicted the river would disappear again as the glacier retreated. "The event is a bit idiosyncratic, given the peculiar geographic situation in which it happened, but in a broader sense it highlights the huge changes that glaciers are undergoing around the world due to climate change," Clague said. The geologic event has redrawn the local landscape. Slims River crosses the Alaska Highway, and its banks were a popular hiking route. Now that the riverbed is exposed, Dall sheep from Kluane National Park are making their way down to eat the fresh vegetation, venturing into territory where they can legally be hunted. With less water flowing in, Kluane Lake did not refill last spring, and by summer 2016 was about 3 feet (1 meter) lower than ever recorded for that time of year. Waterfront land, which includes the small communities of Burwash Landing and Destruction Bay, is now farther from shore. As the lake level continues to drop researchers expect this will become an isolated lake cut off from any outflow. On the other hand, the Alsek River, a popular whitewater rafting river that is a UNESCO world heritage site, was running higher last summer due to the addition of the Slims River's water. Shifts in sediment transport, lake chemistry, fish populations, wildlife behavior and other factors will continue to occur as the ecosystem adjusts to the new reality, Shugar said. "So far, a lot of the scientific work surrounding glaciers and climate change has been focused on sea-level rise," Shugar said. "Our study shows there may be other underappreciated, unanticipated effects of glacial retreat." The Kaskawulsh Glacier is retreating up the valley because of both readjustment after a cold period centuries ago, known as the Little Ice Age, and warming due to greenhouse gases. A technique published in 2016 by UW co-author Gerard Roe shows a 99.5 percent probability that this glacier's retreat is showing the effects of modern climate change. "I always point out to climate-change skeptics that Earth's glaciers are becoming markedly smaller, and that can only happen in a warming climate," Clague said. Other co-authors are Christian Schoof at the University of British Columbia, Michael Willis at the University of Colorado and Luke Copland at the University of Ottawa. The study was funded by the University of Washington Royalty Research Fund, Parks Canada, Yukon Geological Survey, the Natural Sciences and Engineering Research Council of Canada, the University of Ottawa and the University of Illinois. For more information, contact Shugar at dshugar@uw.edu or 253-692-4926 or Clague at jclague@sfu.ca or 778-782-4924.


News Article | May 8, 2017
Site: www.marketwired.com

VANCOUVER, BC--(Marketwired - May 08, 2017) - Kivalliq Energy Corporation (TSX VENTURE: KIV) ("Kivalliq") today announced the acquisition of a dominant land position in one of the largest undeveloped greenstone-iron formation gold belts in Nunavut, Canada. This land package, totalling 408,981.6 hectares and covering 160 kilometres of the Foxe Fold Belt on central Baffin Island, comprises a Mineral Exploration Agreement (MEA) with Nunavut Tunngavik Inc. (NTI); the acquisition of 15 prospecting permits; and a transaction with Commander Resources Ltd. (Commander). "With the acquisition of the Baffin Gold project in Nunavut Territory, we have strengthened our relationship with NTI and we now hold an entire district with proven gold potential," stated Kivalliq Energy CEO Jim Paterson. "Our team will benefit greatly from the significant exploration expenditures from previous operators, which generated extremely high-grade gold numbers at exploration targets that also exhibited potential for significant size and scale. We feel the combination of the Baffin Gold project's key attributes, including: low entry cost; high potential for discovery and expansion of known gold zones; in a mining friendly jurisdiction, make this a highly valuable acquisition for the shareholders of Kivalliq. Our group has multi-decades of experience running successful northern projects and the Baffin Gold Property is a great addition to the Kivalliq portfolio." The Baffin Gold Property is a district-scale land package covering an entire Proterozoic gold belt having geological and structural similarities to multi-million ounce gold mines in the north (i.e. Meadowbank, Lupin) as well as the prolific Homestake Mine in South Dakota. Previous exploration has identified numerous prospects along 140 kilometres of strike length, with high-grade gold occurring in multiple settings: silicate and sulphide iron formation; shear zones and quartz veins hosted in granodiorite, metavolcanics and metasediments. The Baffin Gold Property is comprised of consolidated mineral tenure located approximately 230 kilometres southwest of the community of Clyde River on Baffin Island, in the Qikiqtani region of Nunavut. This property comprises fifteen prospecting permits, six crown mineral claims and three Inuit Owned Land parcels subject to MEA's with NTI. Prior to 2001, exploration and mapping in central Baffin Island focused on base metals. Between 2000 and 2003, the Geological Survey of Canada mapped the western half of the Piling Group and, while no new mineral occurrences were documented, they recognized the area was prospective for several types of mineralization including: zinc-lead in platform carbonates; nickel, copper, cobalt and platinum in layered mafic-ultramafic sills; tin in pegmatitic rocks; and gold in close association with the Bravo Lake ("BLF") and Longstaff Bluff ("LBF") Formations. Gold was first discovered by BHP Billiton and Falconbridge in 2001 during base metal exploration programs, and by 2003 Commander had optioned or staked a large land package similar to Kivalliq's current Baffin Gold Property boundaries. Between 2003 and 2009 Commander operated seasonal field exploration programs costing about $18 million that included: 158 diamond drill holes (19,083 m); two airborne geophysical surveys (GEOTEM and DIGHEM V); four ground geophysical surveys; 2,700 till and soil samples; 4,623 rock (channel and grab) samples. Between 2009 and 2011, AngloGold Ashanti optioned the property and conducted one season of drilling and ground IP surveying. To date, prospecting, mapping and geophysics, followed by drilling, have been very successful in discovering new, high-grade gold zones hosted in a variety of geological settings within the BLF. Most of the drilling completed to date was within 150 metres of surface and focused on following-up surface gold prospects at Malrok (7,221m in 59 holes), and Ridge Lake (7,124m in 67 holes) with limited exploratory drilling at Kanosak (1,960m in 13 holes), Durette (1,784m in 11 holes), and Brent (995m in 8 holes). For tables listing highlights of historic drill hole intercepts and surface sample results, please see: http://www.kivalliqenergy.com/ The Foxe Fold Belt (FFB) is a Proterozoic supra-crustal sequence characterized by upper greenschist to amphibolite facies metamorphism and complex poly-phase deformation. The Baffin Gold Property is centered on the Bravo Lake Formation (BLF), an east-west trending, metavolcanic-sedimentary belt located along the southern edge of Piling Group rocks within the FFB. Prospective gold-bearing zones within the Bravo Lake formation are generally shallow dipping and extend 140 kilometres inland from tidewater into central Baffin Island. High-grade gold occurrences have been identified in three separate iron formation units, within quartz veins in volcanic and sedimentary units of the BLF; and in shear zones within younger intrusions. At least three structural settings controlling gold mineralization have been identified to date: Gold occurs primarily as free gold, associated with arsenopyrite and disseminated within quartz veins. Petrographic work indicates a strong, mineralizing system having either two mineralizing events or a protracted period of gold mineralization. The Kanosak, Ridge, Malrok, and Durette zones are the most advanced prospects within the BLF and represent the range of mineralization and structural analogues within the BLF. These will help guide future exploration programs covering the rest of the property. Kivalliq exploration efforts will target near surface gold in BLF iron formation, greenstone-metasediment hosted quartz veins, similar to other gold deposits in the Nunavut and Northwest Territories, and particularly the prolific Proterozoic aged Homestake Mine in South Dakota. Exploration priorities include an immediate review, compilation and reinterpretation of all geological and exploration data, to develop integrated structural, geophysical and geochemical models targeting the untapped potential of this extremely prospective gold belt. Final plans and budgets for the Baffin Gold Property will be disclosed after a review of existing data has been completed. Initial field work being planned for the summer of 2017 will systematically explore the BLF gold belt and ground truth newly developed models. The program will infill earlier datasets and prioritize un-sourced gold anomalies in till, soil and boulders. Future drilling will further assess known prospects, new structural targets, untested areas of outcropping mineralization and blind targets in covered areas based on till geochemistry and geophysics. As part of Kivalliq's consolidation of mineral tenure in the Qikiqtani Region, Kivalliq has, subject to receipt of all necessary approvals, acquired an option to earn 100% of Commander's Baffin Gold Property which includes 6 mineral claims (5,948 hectares) and a recently signed MEA with NTI on two blocks within Inuit Owned Lands (8,105 hectares). Upon execution of, and pursuant to the terms of the Baffin Gold Property Option Agreement: Terms of MEA's on Inuit Owned Land with Nunavut Tunngavik Inc. Three parcels within Kivalliq's Baffin Gold Property are subject to Mineral Exploration Agreements (MEA's) with NTI, granting exclusive rights to explore for, develop and mine minerals on approximately 72,638 hectares of IOL parcel BI-35 on Baffin Island in the Qikiqtani Region of Nunavut. Under terms of the MEA's on IOL RI-35, NTI will receive: For Baffin Gold Property maps and tables please visit our website: http://www.kivalliqenergy.com/ Kivalliq has not performed any exploration on the Baffin Gold Property to date. Exploration results by Commander and previous explorers reported herein are historic in nature and although not verified by Kivalliq, this work was carried out by knowledgeable explorers using acceptable industry practices at the time. Jeff Ward, P.Geo., President of Kivalliq and a Qualified Person for Kivalliq, has reviewed and approved the scientific and technical information contained in this release. Kivalliq Energy Corporation (TSX VENTURE: KIV) is a Vancouver-based company with a portfolio of high-quality uranium and precious metal exploration projects in Canada. In addition to the new Baffin Gold Property, Kivalliq holds Canada's highest-grade uranium resource outside of Saskatchewan. The Company's flagship project, the 89,852 hectare Angilak Property in Nunavut Territory, hosts the Lac 50 Trend with a NI 43-101 Inferred Resource of 2,831,000 tonnes grading 0.69% U3O8, totaling 43.3 million pounds U3O8. Kivalliq's comprehensive exploration programs continue to demonstrate the "District Scale" potential of the Angilak Property. For disclosure related to the inferred resource for the Lac 50 Trend uranium deposits, please refer to Kivalliq's news release of March 1, 2013. In Saskatchewan, Kivalliq holds a 100% interest in the 13,711 hectare Hatchet Lake Property adjacent to the north-eastern margin of the highly prolific uranium-producing Athabasca Basin. Compilation of results from previous exploration by Hathor Exploration Limited and Rio Tinto have identified multiple, priority unconformity-related basement targets at Hatchet Lake that were followed up in 2015. Kivalliq also holds a 100% interest in the 131,412 hectare Genesis Property located northeast of Saskatchewan's Athabasca Basin, with Roughrider Exploration Limited funding the current exploration program pursuant to an option to acquire up to an 85% interest in the property. This highly prospective project is located along the Wollaston-Mudjatik trend and extends 90 kilometres northeast from Wollaston Lake to the Manitoba border. Kivalliq's team of northern exploration specialists has forged strong relationships with sophisticated resource sector investors and partner Nunavut Tunngavik Inc. (NTI) on both the Angilak and Baffin Gold Properties. Kivalliq was the first company to sign a comprehensive agreement to explore for uranium on Inuit Owned Lands in Nunavut Territory, Canada and is committed to building shareholder value while adhering to high levels of environmental and safety standards and proactive local community engagement. On behalf of the Board of Directors For further information about, Kivalliq Energy Corporation or this news release, please visit our website at www.kivalliqenergy.com or contact Investor Relations toll free at 1.888.331.2269, at 604.646.4527, or by email at info@kivalliqenergy.com. Kivalliq Energy Corporation is a member of the Discovery Group of Companies, for more information please visit: www.discoverygroup.ca. Neither the TSX Venture Exchange nor its Regulation Services Provider (as that term is defined in the policies of the TSX Venture Exchange) accepts responsibility for the adequacy or accuracy of this release. Certain disclosures in this release constitute forward-looking statements that are subject to numerous risks, uncertainties and other factors relating to Kivalliq's operations as a mineral exploration company that may cause future results to differ materially from those expressed or implied in such forward-looking statements, including risks as to the completion of the plans and projects. Readers are cautioned not to place undue reliance on forward-looking statements. Other than as required by applicable securities legislation, Kivalliq expressly disclaims any intention or obligation to update or revise any forward-looking statements whether as a result of new information, future events, or otherwise.


Savard M.M.,Geological Survey of Canada
Environmental Pollution | Year: 2010

Hydrogen (δ2H), carbon (δ13C), oxygen (δ18O) and nitrogen (δ15N) isotopes of tree rings growing in field conditions can be indicative of past pollution effects. The characteristic δ13C trend is a positive shift generally explained by invoking closure of stomata, but experimental studies suggest that increased rates of carboxylation could also generate such trends. In many cases the δ18O and δ2H values decrease in trees exposed to pollution and exhibit inverse coinciding long-term trends with δ13C values. However, some trees exposed to diffuse pollution and experimental conditions can show an increase or no δ18O change even if δ13C values increase. These diverse responses depend on how stress conditions modify physiological functions such as stomatal conductance, carboxylation, respiration, and perhaps water assimilation by the root system. Recent studies suggest that δ15N changes in trees can be caused by soil acidification and accumulation of anthropogenic emissions with isotopic signals deviating from natural N. Crown Copyright © 2009.


Buchan K.L.,Geological Survey of Canada
Precambrian Research | Year: 2013

Key paleomagnetic poles are poles that are well defined and precisely dated. The rock unit from which the pole is derived must have a precise (usually U-Pb) age and the pole itself must be demonstrated primary with a rigorous field test. The use of key poles is essential in defining reliable apparent polar wander paths (APWPs) and establishing continental reconstructions. Many hundreds of Proterozoic paleopoles have been published from around the globe, but only ~45 are from large craton interiors and pass the key pole criteria. Most key poles are from mafic dykes and sills in the Superior craton (pre-1.83. Ga) or Laurentia (post-1.80. Ga) or Baltica. As a result, with occasional exceptions, it is difficult to define or compare reliable APWP segments in order to test Proterozoic continental reconstructions. However, there are now sufficient age matches or approximate age matches for pairs of key poles from a number of cratons to help constrain their relative locations. In this analysis, Proterozoic key poles are identified and their use in constructing APWPs and testing continent and supercontinent reconstructions is discussed. This key pole database establishes a well constrained Superior craton-Laurentia APWP for much of the Proterozoic that can be used as a reference track against which a growing number of individual key poles from other cratons can be compared. There is now a robust Baltica-Laurentia reconstruction for ~330. m.y. between 1.59 and 1.26. Ga using this approach and potentially for ~570. m.y. between 1.83 and 1.26. Ga if additional key and non-key poles from well-dated units are considered. Key pole comparisons for several other cratons yield preliminary constraints on the relative movement of cratons (e.g., Slave and Superior cratons in the Paleoproterozoic) or on specific elements of continental reconstructions (e.g., Amazonia and Baltica in the Mesoproterozoic, South China craton and Australia in the Neoproterozoic, or Baltica and Laurentia also in the Neoproterozoic). © 2013.


Hyndman R.D.,Geological Survey of Canada
Bulletin of the Seismological Society of America | Year: 2015

This article provides a summary of the structure and tectonic history of the Queen Charlotte transform fault zone off western Canada, as background to understanding the 2012 Mw 7.8 thrust earthquake off Haida Gwaii. There was margin subduction prior to the Eocene. The fault zone then became the mainly transcurrent Pacific–North America boundary. There was mid-Tertiary oblique extension, then 15°–20° oblique convergence from ∼6 Ma to the present that resulted in underthrusting and subduction initiation. The total underthrusting has been too small for Benioff–Wadati seismicity or arc volcanics but is indicated by (1) a trench, the Queen Charlotte Trough, into which the oceanic plate bows downward and an offshore flexural bulge, the Oshawa rise; (2) the Queen Charlotte terrace, an accretionary sedimentary prism; (3) seismic receiver function delineation of the underthrusting Pacific plate; (4) heat flow decreasing landward as predicted for underthrusting; (5) low gravity offshore and high onshore, consistent with underthrusting; and (6) late Tertiary uplift and erosion of the west coast of the islands. Oblique convergence is partitioned into nearly marginnormal underthrusting (i.e., Mw 7.8 event) relative to the terrace, which is moving along the margin, and margin parallel on the Queen Charlotte strike-slip fault just off the coast that produced the 1949 Ms 8.1 earthquake. Landward on the mainland, Global Positioning System data suggest slow coast-parallel shear with no historical seismicity. The convergence rate decreases to the north of Haida Gwaii off Dixon Entrance, but large thrust earthquakes are possible. To the south, underthrusting of the Winona basin margin also could generate large earthquakes. © 2015 Seismological Society of America. All rights reserved.


Key paleomagnetic poles are poles that are well defined and precisely dated. The rock unit from which the pole is derived must have a precise (usually U-Pb) age and the pole itself must be demonstrated primary with a rigorous field test. The use of key poles is essential in defining reliable apparent polar wander paths (APWPs) and establishing continental reconstructions. Many hundreds of Proterozoic paleopoles have been published from around the globe, but only ~45 are from large craton interiors and pass the key pole criteria. Most key poles are from mafic dykes and sills in the Superior craton (pre-1.83. Ga) or Laurentia (post-1.80. Ga) or Baltica. As a result, with occasional exceptions, it is difficult to define or compare reliable APWP segments in order to test Proterozoic continental reconstructions. However, there are now sufficient age matches or approximate age matches for pairs of key poles from a number of cratons to help constrain their relative locations. In this analysis, Proterozoic key poles are identified and their use in constructing APWPs and testing continent and supercontinent reconstructions is discussed. This key pole database establishes a well constrained Superior craton-Laurentia APWP for much of the Proterozoic that can be used as a reference track against which a growing number of individual key poles from other cratons can be compared. There is now a robust Baltica-Laurentia reconstruction for ~330. m.y. between 1.59 and 1.26. Ga using this approach and potentially for ~570. m.y. between 1.83 and 1.26. Ga if additional key and non-key poles from well-dated units are considered. Key pole comparisons for several other cratons yield preliminary constraints on the relative movement of cratons (e.g., Slave and Superior cratons in the Paleoproterozoic) or on specific elements of continental reconstructions (e.g., Amazonia and Baltica in the Mesoproterozoic, South China craton and Australia in the Neoproterozoic, or Baltica and Laurentia also in the Neoproterozoic). © 2014.


Some researchers have suggested that Phanerozoic land-based ice sheets extended occasionally into the tropical realm. If true, the tropical ocean at those times must have been distinctly colder than at the Last Glacial Maximum (LGM) when northern hemisphere ice sheets did not extend below 38° latitude. Low-latitude ocean temperatures derived from oxygen isotopes of brachiopod shells test this hypothesis by comparing the temperature regime for Paleozoic and early Mesozoic low-latitude settings to the tropical temperature regime of the modern interstadial ocean, and to mean temperatures estimated for the tropical ocean at LGM. A running mean of pH-adjusted brachiopod habitat temperatures (BHTs) shows that Paleozoic low-latitude oceans were, on average, cool to cold relative to the modern interstadial tropical ocean. At times during Pennsylvanian, Serpukhovian, Tournaisian and Ordovician-Silurian glaciations, these tropical seas were indeed significantly colder on average than at the LGM. Ice-sheets within tropical latitudes can be reasonably predicted at those times. Abundant and diverse Paleozoic brachiopod communities reflect these cool tropical oceans, consistent with modern brachiopod ecological preference for colder waters. Amplified Paleozoic temperature oscillations suggest recurring global warming events which episodically drove these cold tropical oceans to temperatures significantly higher than the warmest modern tropical ocean. © 2012.


Bédard (2006) proposed that Archaean cratons formed above large, long-lived mantle plumes, where the thick basaltic crust cannibalized itself to generate TTGs (tonalite-trondhjemite-granodiorite) and complementary eclogitic restites. In this model the dense eclogitic restites foundered into the depleted upper mantle and refertilized it, triggering generation of new basaltic melt pulses, and so eclogite represents a catalyst for coupled crust-mantle differentiation. Since most of the eclogite is destroyed in the upper mantle, voluminous hidden eclogitic reservoirs are not predicted. The model was not intended to explain the generation of overprinting fabrics and terrane assembly, but to account for chemical evolution of the coupled crust-mantle system in the initial stages of craton development. Wyman (2013) argues that the models and hypotheses presented in Bédard (2006) are unrealistic and irrelevant, and reaffirms his opinion that the Archaean world was dominated by plate tectonics. The criticisms and arguments of Wyman (2013) are invalid. © 2012 Published by Elsevier B.V.

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