scholarly journals Routine K/Ar age determination on post-Silurian dolerite dykes, North Greenland fold belt

1983 ◽  
Vol 115 ◽  
pp. 9-14
Author(s):  
P.R Dawes ◽  
D.C Rex ◽  
N.J Soper
Keyword(s):  
Age Determination ◽  
Field Studies ◽  
Fold Belt ◽  
The North ◽  
Isotopic Analyses ◽  
History Of ◽  
Magmatic History ◽  
The University ◽  
North Greenland

This note documents results of routine K/Ar isotopic age determination of dolerite dykes from the North Greenland fold belt. All the material was collected in 1969 by two of us (P.R.D. and N.J.S.) during the Joint Services Expedition to Peary Land; the isotopic analyses have been undertaken by D.C.R. in the geologicallaboratories of the University of Leeds. In view of the renewed interest in the tectonic and magmatic history of the Peary Land region stemming from the systematic field studies carried out by GGU in 1978-1980 (see GGU Rapport 88, 99 and 106), the results of this early dating programme are listed here as a contribution to this discussion. Recently, some reference has been made in the literature to these hitherto unpublished results (Dawes & Soper, 1979; Higgins et al., 1981; Håkansson & Pedersen, 1982).

scholarly journals Permafrost as a climatic indicator in northern Victoria Land, Antarctica

1999 ◽  
Vol 29 ◽  
pp. 131-135 ◽  
Author(s):  
M. Guglielmin ◽  
F. Dramis
Keyword(s):  
Ground Ice ◽  
Patterned Ground ◽  
Thermal Inversion ◽  
Ground Temperatures ◽  
The North ◽  
Victoria Land ◽  
Investigation Methods ◽  
Isotopic Analyses ◽  
History Of ◽  
Rock Glaciers

AbstractKnowledge of permafrost characteristics and distribution in Antarctica and their relationships with present and past climates is still poor. This paper reports investigations on permafrost in an area located between Nansen Ice Sheet to the south and Mount Melbourne (2732 m a.s.l.) to the north. Investigation methods included geomorphological surveys and geoelectrical soundings as well as crystallography, chemical and isotopic analyses of the ground ice. Geomorphological surveys helped to explain the relationships between periglacial landforms (e.g. rock glaciers and patterned ground) and the glacial history of the area. Geoelectrical soundings allowed us to define different ground-ice units in the ice-free areas. Each unit was characterised by a different type of permafrost (dry or ice-poor permafrost, marine or continental massive buried ice and sub-sea permafrost). To identify the nature of ground ice, trenches were dug and some shallow boreholes were drilled to a maximum depth of-3.6 m in massive buried ice. Samples of both ice-poor permafrost and massive ice were collected and analyzed. Chemical, isotopic δ18O and crystal analyses were also carried out. The relationships between climate and thermal regimes of the active layer and the upper part of permafrost were determined using a monitoring station for ground temperatures at Boulder Clay Glacier, near the Italian Antarctic station. During winter, there were several significant thermal-inversion events in the ground, which cannot be explained only by air-temperature changes, suggesting a possible influence of winter snowfall, even if these events are usually considered very rare.

scholarly journals Volcanic centres between Frigg Fjord and Midtkap, eastern North Greenland

1981 ◽  
Vol 106 ◽  
pp. 69-75
Author(s):  
I Parsons
Keyword(s):  
Fault Zone ◽  
Fold Belt ◽  
The South ◽  
The North ◽  
Rock Types ◽  
South West ◽  
North Greenland

A series of smal! volcanic centres cut Ordovician turbidites of Formation A in the southem part of Johannes V. Jensen Land between Midtkap and Frigg Fjord (Map 2). Their general location and main rock types were described by Soper et al. (1980) and their nomenclature is adopted here for fig. 22 with the addition of the small pipe B2. A further small intrusion, south-west of Frigg Fjord, was described by Pedersen (1980). The centres lie 5-10 km south of, and parallel to, the important Harder Fjord fault zone (fig. 22) which traverses the southern part of the North Greenland fold belt and shows substantial downthrow to the south (Higgins et al., this report).

scholarly journals Silicic volcanism in the Scottish Lower Carboniferous; lavas, intrusions and ignimbrites of the Garleton Hills Volcanic Formation, SE Scotland

2020 ◽  
Vol 56 (1) ◽  
pp. 63-79
Author(s):  
Brian G. J. Upton ◽  
Linda A. Kirstein ◽  
Nicholas Odling ◽  
John R. Underhill ◽  
Robert M. Ellam ◽  
...  
Keyword(s):  
Extensional Tectonics ◽  
Isotopic Data ◽  
Central Type ◽  
Lower Carboniferous ◽  
The North ◽  
Basaltic Magmatism ◽  
North Side ◽  
Volcanic Formation ◽  
History Of ◽  
Magmatic History

Extensional tectonics and incipient rifting on the north side of the Iapetus suture were associated with eruption of (mainly) mildly alkaline olivine basalts. Initially in the Tournaisian (Southern Uplands Terrane), magmatic activity migrated northwards producing the Garleton Hills Volcanic Formation (GHVF) across an anomalous sector of the Southern Uplands. The latter was followed by resumption of volcanism in the Midland Valley Terrane, yielding the Arthur's Seat Volcanic Formation. Later larger-scale activity generated the Clyde Plateau Volcanic Formation (CPVF) and the Kintyre lavas on the Grampian Highlands Terrane. Comparable volcanic successions occur in Limerick, Ireland. This short-lived (c. 30 myr) phase was unique in the magmatic history of the Phanerozoic of the British Isles in which mildly alkaline basaltic magmatism locally led to trachytic differentiates. The Bangly Member of the GHVF represents the largest area occupied by such silicic rocks. The most widespread lavas and intrusions are silica-saturated/oversaturated trachytes for which new whole-rock and isotopic data are presented. Previously unrecognized ignimbrites are described. Sparse data from the fiamme suggest that the magma responsible for the repetitive ignimbrite eruptions was a highly fluid rhyolite. The Bangly Member probably represents the remains of a central-type volcano, the details of which are enigmatic.

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.

New age determination of the Cenozoic Lunpola basin, central Tibet

2011 ◽  
Vol 149 (1) ◽  
pp. 141-145 ◽  
Author(s):  
HUAIYU HE ◽  
JIMIN SUN ◽  
QIULI LI ◽  
RIXIANG ZHU
Keyword(s):  
Isotope Composition ◽  
Age Determination ◽  
The Tibetan Plateau ◽  
Late Oligocene ◽  
Geological Past ◽  
History Of ◽  
Uplift History ◽  
Central Tibet ◽  
Important Basis

AbstractKnowing when the Tibetan Plateau reached its present elevation is important for understanding the uplift history of Tibet. Recently, Rowley & Currie (2006) suggested that central Tibet exceeded 4000 m from 35 Ma to the Pliocene using the oxygen-isotope composition of calcareous minerals in Lunpola basin sediments. However, they adopted a poor age assignment for the Dingqing Formation in the Lunpola basin based on previous microfossil studies. In this study, we present SIMS U–Pb zircon dates from a bentonite layer intercalated within the middle to lower Dingqing Formation. Twenty-six measurements yield a highly reliable U–Pb age of 23.5 ± 0.2 Ma (2σ, MSWD = 1.1), suggesting that the deposition age of the Dingqing Formation is late Oligocene to early Miocene, much older than the Miocene–Pliocene age used by Rowley & Currie (2006). This age robustly constrains the age of Cenozoic sedimentary strata in central Tibet, and hence provides an important basis for estimating the palaeoelevation in the high Tibet during the geological past.

scholarly journals "Insufferably Stupid or Miserably Out of Place": F. A. P. Barnard and His Scientific Instrument Collection in the Antebellum South

2009 ◽  
Vol 39 (4) ◽  
pp. 418-443 ◽  
Author(s):  
Stephen Case
Keyword(s):  
Civil War ◽  
The United States ◽  
Scientific Instrument ◽  
Antebellum South ◽  
University Of Mississippi ◽  
The South ◽  
The North ◽  
History Of ◽  
The University ◽  
Practice Of Science

In the 1850s, the American scientist and educator Frederick A. P. Barnard created a collection of scientific apparatus at the University of Mississippi in Oxford, Mississippi, of a size and expense that surpassed any collection in the United States at that time. The collection, which would come to include over three hundred instruments of both American and European manufacture, was the attempt by Barnard, born and educated in the North, to bring Big Science to the South and challenge the dominance of Northern schools in science education. In this respect it failed, and the collection became a forgotten footnote in the history of Southern science. This article examines the importance of the collection in understanding science at U.S. universities before the Civil War and what Barnard referred to as the "scientific atmosphere" of the South. The first section compares the collection to others of the period, highlighting its historical uniqueness and significance. The second section uses Barnard's correspondence to construct a narrative of the collection's assembly, providing insight into the international scientific instrument market of the period as well as the difficulties he faced working in the antebellum South. Finally, an examination of Barnard's perceptions regarding intellectual isolation and the failure of his endeavor highlights differences perceived by scientists of the day concerning the practice of science in the North versus in the South prior to the Civil War.

scholarly journals Structural and stratigraphic framework of the North Greenland fold belt in Johannes V. Jensen Land, Peary Land

1979 ◽  
Vol 93 ◽  
pp. 1-40
Author(s):  
P.R Dawes ◽  
N.J Soper
Keyword(s):  
Northern Coast ◽  
Structural Detail ◽  
Fold Belt ◽  
The North ◽  
Stratigraphic Framework ◽  
Mineral Assemblages ◽  
Lower Palaeozoic ◽  
Main Deformation ◽  
Basin Margin ◽  
North Greenland

Structural and stratigraphic detaiIs collected during reconnaissance fjeld work in northern Peary Land in 1969 are presented to substantiate the rather general accounts of the North Greenland fold belt hitherto published. The structural detail, largely in the form of graphic profiles sketched in the fieid, is referred to a structural frarnework in which three main deformation phases are recognised. The fold belt displays a roughly E-W zonation based on the progressive northerly increasing intensity of deformation and metamorphic effects that culminate along the northern coast in amphibolite-facies mineral assemblages in complexly folded schist lithologies. It is stressed that, while the conspicuous structural character of the fold belt is its northerly vergence seen particularly in the northernmost part, the detailed structural make-up of the fold belt is complex. Fold style and vergence vary considerably and the southern margin of the fold belt, autochthonous with respect to the platform, is characterised by south-verging folds. Some stratigraphical data is presented particularly from the Lower Palaeozoic sequence at the southern part of the fold belt that iIIustrates the basinal clastic facies at the sheIf-basin margin.

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