A late Precambrian rift-related igneous suite in western Newfoundland

1985 ◽  
Vol 22 (11) ◽  
pp. 1727-1735 ◽  
Author(s):  
Harold Williams ◽  
R. T. Gillespie ◽  
Otto Van Breemen
Keyword(s):  
North Atlantic Ocean ◽  
Volcanic Rocks ◽  
The United States ◽  
Granitic Rocks ◽  
Late Precambrian ◽  
The North ◽  
Iapetus Ocean ◽  
Carbonate Sequence ◽  
Silicic Volcanic ◽  
High Level

A granite that yields a U–Pb zircon age of 602 ± 10 Ma is associated with mafic and silicic volcanic rocks and metamorphic equivalents near Deer Lake in western Newfoundland. The granitic rocks are named the Round Pond granite, and the combined granite–volcanic suite is assigned to the Hughes Lake complex. All of the rocks are contained in the Hughes Lake structural slice that occurs above other allochthonous rocks and the autochthonous Cambrian–Ordovician carbonate sequence of western Newfoundland.The Round Pond granite is cut by metadiabase dykes. Mafic volcanic rocks, interpreted as coeval with the dykes, occur along the southeast side of the granite. A thick sequence of arkosic metagreywackes and psammitic to pelitic schists of the Mount Musgrave Group occurs stratigraphically above the mafic volcanic rocks. Regional correlations imply that the Mount Musgrave Group is of late Precambrian – Early Cambrian age, thus setting an upper stratigraphic limit to the age of the Hughes Lake complex.Perthitic and granophyric textures and the chemistry of the Round Pond granite are typical of anorogenic high-level hypersolvus intrusions. Nearby pink silicic volcanic rocks are probably consanguineous with the granite and together with the mafic volcanics form a bimodal suite.Bimodal volcanic suites and related mafic dykes and granitic intrusions imply rift tectonic settings. Occurrences along the west flank of the Appalachian Orogen are equated with the initiation of an ancient continental margin and the opening of an Iapetus Ocean. The 602 ± 10 Ma age of the Round Pond granite dates the rifting in western Newfoundland. Older isotopic ages on similar rocks in the southern Appalachians of the United States suggest a diachronous Precambrian rifting and Iapetus opening that propagated northward, much like the Mesozoic opening of the North Atlantic Ocean.

Determination of the characteristics of crystalline rocks by field experiments: a review

1986 ◽  
Vol 319 (1545) ◽  
pp. 139-156 ◽  
Keyword(s):  
Radioactive Waste ◽  
Field Experiments ◽  
The United States ◽  
Crystalline Rocks ◽  
Granitic Rocks ◽  
Rock Types ◽  
Basement Rocks ◽  
Deep Boreholes ◽  
High Level ◽  
Underground Research Laboratory

Crystalline rocks, particularly granitic rocks and basalts, are one of the principal rock types under consideration as a potential host rock for a high-level radioactive waste repository. Permeability in such rocks is related to discontinuities of various scales, and the quantification and prediction of groundwater flow within both the fractures and the intact rock between the fractures is the major goal of field experiments. The Canadian Underground Research Laboratory is unique in that the hydrogeological conditions within a large volume of rock surrounding the experimental shaft are being monitored before, during and after excavation and the results compared with model predictions. In Switzerland twelve deep boreholes are being drilled to over 1000 m to investigate crystalline basement rocks beneath a cover of sediments. The Stripa Mine in Sweden has hosted a major experimental programme including heater tests to stimulate the thermal effect of radioactive waste and hydrogeological tests at various scales down to individual fractures. The United States of America, the United Kingdom, France and Finland have also embarked on major experimental programmes. Continuing research is needed, with an emphasis on field experiments and research in underground rooms, to provide the data on which detailed risk assessments can be based.

scholarly journals Introduction: from the British Tertiary into the future – modern perspectives on the British Palaeogene and North Atlantic Igneous provinces

2009 ◽  
Vol 146 (3) ◽  
pp. 305-308 ◽  
Author(s):  
DOUGAL A. JERRAM ◽  
KATHRYN M. GOODENOUGH ◽  
VALENTIN R. TROLL
Keyword(s):  
North Atlantic ◽  
18Th Century ◽  
North Atlantic Ocean ◽  
Volcanic Rocks ◽  
Large Igneous Province ◽  
The North ◽  
Igneous Provinces ◽  
Starting Point ◽  
Igneous Province ◽  
Dyke Swarms

The study of volcanic rocks and igneous centres has long been a classic part of geological research. Despite the lack of active volcanism, the British Isles have been a key centre for the study of igneous rocks ever since ancient lava flows and excavated igneous centres were recognized there in the 18th century (Hutton, 1788). This led to some of the earliest detailed studies of petrology. The starting point for many of these studies was the British Palaeogene Igneous Province (BPIP; formerly known as the ‘British Tertiary’ (Judd, 1889), and still recognized by this name by many geologists around the globe). This collection of lavas, volcanic centres and sill/dyke swarms covers much of the west of Scotland and the Antrim plateau of Northern Ireland, and together with similar rocks in the Faroe Islands, Iceland and Greenland forms a world-class Large Igneous Province. This North Atlantic Igneous Province (NAIP) began to form through continental rifting above a mantle plume at c. 60 Ma, and subsequently evolved as North America separated from Europe, creating the North Atlantic Ocean.

scholarly journals Hurricane Katrina (2005). Part II: Evolution and Hemispheric Impacts of a Diabatically Generated Warm Pool

2007 ◽  
Vol 135 (12) ◽  
pp. 3927-3949 ◽  
Author(s):  
Ron McTaggart-Cowan ◽  
Lance F. Bosart ◽  
John R. Gyakum ◽  
Eyad H. Atallah
Keyword(s):  
United States ◽  
Hurricane Katrina ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Flow Analysis ◽  
Warm Pool ◽  
The United States ◽  
The North ◽  
The North Atlantic ◽  
Upper Level

Abstract The landfall of Hurricane Katrina (2005) near New Orleans, Louisiana, on 29 August 2005 will be remembered as one of the worst natural disasters in the history of the United States. By comparison, the extratropical transition (ET) of the system as it accelerates poleward over the following days is innocuous and the system weakens until its eventual demise off the coast of Greenland. The extent of Katrina’s perturbation of the midlatitude flow would appear to be limited given the lack of reintensification or downstream development during ET. However, the slow progression of a strong upper-tropospheric warm pool across the North Atlantic Ocean in the week following Katrina’s landfall prompts the question of whether even a nonreintensifying ET event can lead to significant modification of the midlatitude flow. Analysis of Hurricane Katrina’s outflow layer after landfall suggests that it does not itself make up the long-lived midlatitude warm pool. However, the interaction between Katrina’s anticyclonic outflow and an approaching baroclinic trough is shown to establish an anomalous southwesterly conduit or “freeway” that injects a preexisting tropospheric warm pool over the southwestern United States into the midlatitudes. This warm pool reduces predictability in medium-range forecasts over the North Atlantic and Europe while simultaneously aiding in the development of Hurricanes Maria and Nate. The origin of the warm pool is shown to be the combination of anticyclonic upper-level features generated by eastern Pacific Hurricane Hilary and the south Asian anticyclone (SAA). The hemispheric nature of the connections involved with the development of the warm pool and its injection into the extratropics has an impact on forecasting, since the predictability issue associated with ET in this case involves far more than the potential reintensification of the transitioning system itself.

Rb–Sr geochronology and metamorphic history of Proterozoic to early Archean rocks north of the Cape Smith Fold Belt, Quebec

1987 ◽  
Vol 24 (4) ◽  
pp. 813-825 ◽  
Author(s):  
Ronald Doig
Keyword(s):  
Volcanic Rocks ◽  
Granitic Rocks ◽  
Iron Formation ◽  
Fold Belt ◽  
Metasedimentary Rocks ◽  
Metamorphic History ◽  
The North ◽  
Basement Rocks ◽  
History Of ◽  
Wide Zone

The Churchill Province north of the Proterozoic Cape Smith volcanic fold belt of Quebec may be divided into two parts. The first is a broad antiform of migmatitic gneisses (Deception gneisses) extending north from the fold belt ~50 km to Sugluk Inlet. The second is a 20 km wide zone of high-grade metasedimentary rocks northwest of Sugluk Inlet. The Deception gneisses yield Rb–Sr isochron ages of 2600–2900 Ma and initial ratios of 0.701–0.703, showing that they are Archean basement to the Cape Smith Belt. The evidence that the basement rocks have been isoclinally refolded in the Proterozoic is clear at the contact with the fold belt. However, the gneisses also contain ubiquitous synclinal keels of metasiltstone with minor metapelite and marble that give isochron ages less than 2150 Ma. These ages, combined with low initial ratios of 0.7036, show that they are not part of the basement, as the average 87Sr/86Sr ratio for the basement rocks was about 0.718 at that time.The rocks west of Sugluk Inlet consist mainly of quartzo-feldspathic sediments, quartzites, para-amphibolites, marbles, and some pelite and iron formation. In contrast to the Proterozoic sediments in the Deception gneisses, these rocks yield dates of 3000–3200 Ma, with high initial ratios of 0.707–0.714. These initial ratios point to an age (or a provenance) much greater than that of the Archean Deception gneisses. The rocks of the Sugluk terrain are intruded by highly deformed sills of granitic rocks with ages of about 1830 Ma, demonstrating again the extent and severity of the Proterozoic overprint. The eastern margin of this possibly early Archean Sugluk block is a discontinuity in age, lithology, and geophysical character that could be a suture between two Archean cratons. It is not known if such a suturing event is of Archean age, or if it is related to the deformation of the Cape Smith Fold Belt.Models of evolution incorporating both the Cape Smith Belt and the Archean rocks to the north need to account for the internal structure of the fold belt, the continental affinity of many of the volcanic rocks, the continuity of basement around the eastern end of the belt, and the increase in metamorphism through the northern part of the belt into a broad area to the north. The Cape Smith volcanic rocks may have been extruded along a continental rift, parallel to a continental margin at Sugluk. Continental collison at Sugluk would have thrust the older and higher grade Sugluk rocks over the Deception gneisses, produced the broad Deception antiform, and displaced the Cape Smith rocks to the south in a series of north-dipping thrust slices.

Handling a Vessel in Ice

1959 ◽  
Vol 12 (2) ◽  
pp. 141-152
Keyword(s):  
United States ◽  
United States Navy ◽  
North Atlantic Ocean ◽  
The United States ◽  
Kind Permission ◽  
American Experience ◽  
The North ◽  
False Sense ◽  
Polar Research Institute ◽  
Ice Field

This paper, prepared by the Hydrographic Office of the United States Navy Department, and based on recent American experience, was originally printed on the back of the April 1958 Pilot Chart of the North Atlantic Ocean. It is reproduced here by kind permission of the Hydrographer of the United States Navy. A less extensive treatment of the subject, to which readers may like to refer, was given by L. R. R. Foster in the Journal in 1952 (‘Some Recent Work on Polar Navigation’, 5, 12). Figs. 1–12 are reproduced from the Polar Record (8, 1956–7) by kind permission of the Scott Polar Research Institute, Cambridge.The first requisite of the embryonic ice pilot is to develop a healthy respect for the tremendous power of the ice. He must never permit the peaceful appearance of an ice-field to lull him into a false sense of security. On the other hand, he need not fear the ice, since a great deal of progress through ice can be made by a vessel in capable hands.

scholarly journals Lithostratigraphy, geology and geochemistry of the volcanic rocks of the Vaigat Formation on Disko and Nuussuaq, Paleocene of West Greenland

2017 ◽  
Vol 39 ◽  
pp. 1-244
Author(s):  
Asger Ken Pedersen ◽  
Lotte Melchior Larsen ◽  
Gunver Krarup Pedersen
Keyword(s):  
Volcanic Rocks ◽  
First Episode ◽  
The Third ◽  
The North ◽  
Rock Types ◽  
Magma Reservoirs ◽  
Native Iron ◽  
Volcanic Succession ◽  
High Level ◽  
Contamination Events

The Paleocene volcanic rocks in the Nuussuaq Basin on Disko and Nuussuaq comprise the Vaigat Formation (c. 62–61 Ma) and the Maligât Formation (c. 60 Ma). The Vaigat Formation in this area is 0–1600 m thick and is dominated by olivine-rich picrites. The formation was deposited during three volcanic episodes and is divided into 10 formally defined members and about 20 informal units. The first episode gave rise to the Anaanaa Member. The second episode gave rise to the Naujánguit Member, which is intercalated with the minor, crustally contaminated Nuusap Qaqqarsua, Nuuk Killeq, Asuk, Tunoqqu and Kûgánguaq members and the uncontaminated Qordlortorssuaq Member. The third episode gave rise to the Ordlingassoq Member and the minor alkaline Manîtdlat Member. Contemporaneous sediments deposited during the first two episodes are the marine Eqalulik Formation, and during the third episode the nonmarine Atanikerluk Formation. During the second episode, the polarity of the geomagnetic field changed from normal (Chron C27n) via a transition zone to reversed (C26r). The deposits of the first volcanic episode are situated on western Nuussuaq. During the second and third episodes, the volcanism gradually spread eastwards and southwards so that the Vaigat Formation now forms a domed structure, thickest in the north, thinning out on northern Disko and reaching eastwards to the high gneiss country on central Nuussuaq. The earliest eruptions took place on the sea floor and quickly built up a subaerial lava plateau. All three episodes gave rise to complicated facies changes between subaqueous and subaerial eruption products caused by the eastmoving volcanism, subsidence, volcanic aggradation and blockage of the sea connection against the elevated eastern gneiss country. Eruption sites are widespread for all three volcanic episodes. Within certain time periods, a number of contemporaneous high-level magma reservoirs developed within sediments of the Nuussuaq Group, and the crustally contaminated members formed in these reservoirs by reaction between Mg-rich magmas and sediments. The uncontaminated rocks in the Vaigat Formation are picrites with 12–31 wt% MgO and subordinate basalts with 7–12 wt% MgO. The crustally contaminated rocks range from silicic picrites with 12–16 wt% MgO (Nuusap Qaqqarsua Member) to native-iron-bearing magnesian andesites with 6–10 wt% MgO and up to 62 wt% SiO2 (Asuk Member). The Asuk Member includes unique, strongly reduced rock types with native iron, graphite and sulfide. The contaminated units have individually distinct compositions, indicating individually different contamination events. The alkaline Manîtdlat Member contains an enriched lithospheric component. Present-day seeps of migrated oil are widespread in the oldest part of the volcanic succession on western Nuussuaq. Some of the contaminated magmas in the Asuk and Kûgánguaq members have fractionated sulfides with Cu and Ni and have been explored for nickel and platinum-group elements. 

scholarly journals Filling and plugging of a marine basin by volcanic rocks: the Tunoqqu Member of the Lower Tertiary Vaigat Formation on Nuussuaq, central West Greenland

1996 ◽  
Vol 171 ◽  
pp. 5-28
Author(s):  
A.K Pedersen ◽  
L.M Larsen ◽  
G.K Pedersen ◽  
K.S Dueholm
Keyword(s):  
Volcanic Rocks ◽  
Water Levels ◽  
North Coast ◽  
Magma Chambers ◽  
Tectonic Control ◽  
Crustal Rocks ◽  
The North ◽  
High Level ◽  
Marine Embayment ◽  
Volcanic Cycles

The volcanic Tunoqqu Member formed at the end of the second of three volcanic cycles in the Paleocene Vaigat Formation. The Tunoqqu Member consists of brown aphyric and feldspar-phyric basalts and forms a marker horizon within the grey picritic rocks of the Vaigat Formation. Most of the basalts are siliceous and were produced by contamination with crustal rocks of magmas ranging in composition from picrite to evolved basalt. Some of the basalts were erupted from local volcanic centres of which four have been identified, whereas other basalts form more regional flows. The four identified eruption centres are located along fault lines and zones of uplift and subsidence, indicating tectonic control. Tectonic control is also inferred to be important in terminating the volcanic cycle and causing the development of high-level magma chambers where the magmas stagnated, fractionated, and became contaminated. The basalts of the Tunoqqu Member form subaerial lava flows in western Nuussuaq. Central Nuussuaq constituted a marine embayment in which the volcanics were deposited as eastward prograding foreset-bedded hyaloclastite breccia fans which indicate water depths of up to 160 m. Eastern Nuussuaq was a gneiss highland with a more than 700 m high NW-SE-elongated gneiss promontory stretching into the sea. During Tunoqqu Member time the volcanic rocks reached the gneiss promontory and blocked the outlet from the south to the sea in the north. This resulted in increased water levels in the enclosed embayment and transformation of the outlet into a torrential river. This river eroded the concomitantly forming Tunoqqu Member volcanics and the gneiss promontory and deposited the material in up to more than 250 m thick foreset-bedded boulder conglomerates in the sea where the north coast of Nuussuaq is now situated.

scholarly journals A Reanalysis of the 1931–43 Atlantic Hurricane Database*

2014 ◽  
Vol 27 (16) ◽  
pp. 6093-6118 ◽  
Author(s):  
Christopher W. Landsea ◽  
Andrew Hagen ◽  
William Bredemeyer ◽  
Cristina Carrasco ◽  
David A. Glenn ◽  
...  
Keyword(s):  
Tropical Cyclones ◽  
North Atlantic Ocean ◽  
Weather Prediction ◽  
The United States ◽  
Random Errors ◽  
Systems Methodology ◽  
Wind Field Model ◽  
Atlantic Hurricane ◽  
The North ◽  
Systematic Biases

Abstract A reanalysis of the Atlantic basin tropical storm and hurricane database (“best track”) for the period from 1931 to 1943 has been completed as part of the Atlantic Hurricane Database Reanalysis Project. This reassessment of the main archive for tropical cyclones of the North Atlantic Ocean, Caribbean Sea, and Gulf of Mexico was necessary to correct systematic biases and random errors in the data as well as to search for previously unrecognized systems. Methodology for the reanalysis process for revising the track and intensity of tropical cyclone data is largely unchanged from that of the preceding couple of decades and has been detailed in a previous paper on the reanalysis. Accurate Environmental Forecasting’s numerical weather prediction-based wind field model was utilized here to help determine which states were impacted by various hurricane force winds in several U.S. landfalling major hurricanes during this era. The 1931–43 dataset now includes 23 new tropical cyclones, excludes five systems previously considered tropical storms, makes generally large alterations in the intensity estimates of most tropical cyclones (at various times both toward stronger and weaker intensities), and typically adjusts existing tracks with minor corrections. Average errors in intensity and track values are estimated for both open ocean conditions as well as for landfalling systems. Finally, highlights are given for changes to the more significant hurricanes to impact the United States, Central America, and the Caribbean for this time period.

The Twillingate Granite and nearby Volcanic Groups: An Island Arc Complex In Northeast Newfoundland

1975 ◽  
Vol 12 (6) ◽  
pp. 982-995 ◽  
Author(s):  
Harold Williams ◽  
John G. Payne
Keyword(s):  
Volcanic Rocks ◽  
Metamorphic Grade ◽  
Island Arc ◽  
Granitic Rocks ◽  
Arc Volcanism ◽  
Pillow Lavas ◽  
The North ◽  
Structural Style ◽  
Lower Ordovician ◽  
Island Arc Volcanism

The Twillingate Granite cuts mafic pillow lavas and silicic fragmental volcanic rocks of the Sleepy Cove Group. The granitic rocks are soda-rich and they vary from intensely foliated and mylonitic in the south to mildly foliated and massive toward the north. The Sleepy Cove volcanic rocks show similar structural and metamorphic variations from lineated amphibolitic pillow lavas, to elongated pillows of greenschist metamorphic grade, to slightly metamorphosed and relatively undeformed pillow lavas.The collective terrane occupied by the Twillingate Granite and Sleepy Cove Group is virtually surrounded by intrusive mafic dikes that are integral and coeval parts of the Moretons Harbour and Herring Neck Groups. The dikes decrease in abundance away from the contacts of the collective Twillingate – Sleepy Cove terrane. The essentially intrusive contact is modified by faults and locally, the profuse dike swarms are absent.Regional relationships, thickness, lithofacies, and petrochemistry all indicate that the Moretons Harbour and Herring Neck Groups relate to an episode of Lower Ordovician island arc volcanism. Intrusive relationships and contrasts in structural style and metamorphic grade indicate that the Twillingate Granite and Sleepy Cove Group are older. These older rocks are also interpreted as island arc derivatives, so that in their present position, they may represent the remnant of a partly deformed and metamorphosed older arc that is now bordered by relatively undeformed Lower Ordovician volcanic rocks.Similar relationships within transported sequences of western Newfoundland suggest a central Newfoundland island arc provenance for the transported Little Port Complex.

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