Early history of the Midcontinent Rift inferred from geochemistry and sedimentology of the Mesoproterozoic Osler Group, northwestern Ontario

2007 ◽  
Vol 44 (3) ◽  
pp. 389-412 ◽  
Author(s):  
Pete Hollings ◽  
Philip Fralick ◽  
Brian Cousens
Keyword(s):  
Alluvial Fan ◽  
Midcontinent Rift ◽  
Fluvial Systems ◽  
The North ◽  
Northwestern Ontario ◽  
History Of ◽  
Group A ◽  
South Axis ◽  
Island Basalt ◽  
East West

The Mesoproterozoic 1108–1105 Ma Osler Group, a 3 km thick succession of basaltic flows and sedimentary units on the north shore of Lake Superior, is among the oldest expressions of the Midcontinent Rift. Basal sediments of the Simpson Island Formation (new name) deposited by braided fluvial systems record westward transport of debris eroded from local Archean and Proterozoic rock units. Strata deposited by this fluvial system are intercalated with, and overlain by, ocean-island basalt (OIB)-like basalts, which become increasingly contaminated up section (εNd(1100Ma) = +0.3 to –5.3). The light rare-earth element (LREE) enriched (La/Smn = 1.5–3.9) and heavy REE (HREE) fractionated (Gd/Ybn = 1.5–3.7) subaerial flows are divisible into two units that correlate with other sections of the Osler Group to the east, but simple correlations with more distant sequences are difficult. The volcanic rock dominated portion of the succession is overlain by a thin (25 m thick) conglomerate–sandstone assemblage representing southeast progradation of an alluvial fan in a semi-arid climatic setting. Clast lithologies and geochemistry indicate no extra-rift detritus was delivered from the hinterland of the fan. Various lines of evidence in both volcanic and sedimentary rocks support a scenario where early, pre-1108 Ma, subsidence along a north–south axis from the western arm of the rift to the Nipigon Embayment was replaced by subsidence along the east–west rift axis between 1108 and 1105 Ma.

scholarly journals EVOLUTION OF KARAKORAM SEQUENCE, HUNZA VALLEY NE PAKISTAN: EVIDENCES FROM FIELD MAPPING AND MICRO-ANALYTICAL WORK

2020 ◽  
Vol 5 ◽  
pp. 19
Author(s):  
S. S. Baig ◽  
C. Xue ◽  
Masroor Alam ◽  
Naeem Ullah ◽  
M. Alam ◽  
...  
Keyword(s):  
Geological Mapping ◽  
Central Portion ◽  
High Grade ◽  
Metamorphic Complex ◽  
Field Mapping ◽  
The North ◽  
Analytical Work ◽  
History Of ◽  
Micro Analysis ◽  
East West

The Karakoram metamorphic Complex (KMC) in the southern Karakoram block is one of the best examples of Barrovian type metamorphism that comprises numerous exhumed metapelite units where a series of low to high grade (green schist to sillimanite facie) rocks are exposed. This sequence shows a complex polyphase history of metamorphism and deformation which offer deeper understanding of collision orogeny. Karakoram metamorphic Complex contains metapelites, meta-carbonates, meta-igneous and amphibolite layers, cross-cut by granite sheets in the northern part. This complex is bounded to the north by the Hunza plutonic unit which is the central portion of the massive east-west trending Karakoram axial batholith and to the southwest by the Main Karakoram thrust (MKT). In this contribution, we provide detail geological mapping, petrography, geochemistry and micro-analytical work using Electron Prob-micro analysis in the central Hunza Valley.

Debating the South in Unified Italy

2020 ◽  
pp. 186-214
Author(s):  
Stefan Nygård
Keyword(s):  
Nation State ◽  
The South ◽  
National Politics ◽  
The North ◽  
Political Debates ◽  
Catching Up ◽  
History Of ◽  
South Axis ◽  
Nation State Formation ◽  
North And South

The history of modern Italy is an illustrative example of the different social and spatial layers of the North–South divide. Since unification in 1861, Italy has struggled to overcome regional imbalances, mainly although not exclusively along a North–South axis. With an emphasis on the period following unification, when North-South was placed at the centre of national politics, this chapter surveys the lingering debates on Italy’s so-called Southern question and the dynamics of nation-state formation in which it is embedded. The contested history of this process includes debates over economic and moral debts caused by the uneven distribution of gains and sacrifices between North and South as a result of unification. Socio-economically, two North–South divides developed in parallel after unification; the more significant one between Italy and transalpine Europe, and the initially minor but eventually growing divergence between the northern and southern regions within Italy. The ideas of development, catching-up and “Europeanization” were recurring themes in the intellectual and political debates discussed in the chapter. The contested issue was whether the North was developing the South, or vice versa.

Notes on the mineral deposits of the Teign valley, Devon

1945 ◽  
Vol 27 (189) ◽  
pp. 75-78
Author(s):  
J. V. Ramsden
Keyword(s):  
Mineral Deposits ◽  
List Type ◽  
Type Number ◽  
Granite Massif ◽  
Eastern Flank ◽  
The North ◽  
Ore Bodies ◽  
History Of ◽  
East West

Research into the history of the old mines suggests that two mineralized fissuring systems intersect in central Devon, often carrying commercial ore-bodies. The older of these is the east-west system usually carrying copper, iron, or tin, which has been extensively worked in west Devon, but is less developed on the eastern flank of the Dartmoor granite massif.The younger north-south series, characterized by its lead and silver ores and baryte is particularly well developed in the Teign valley. This band of mineralization can be traced from the north of Scotland through Brittany and Spain to Algeria. In Devon it appears to be divided into three main fissure bands:1.Combe Martin to Plymouth.2.North Molton to Spreyton, with a possible extension south of the Dartmoor granite.3.Molland to Newton St. Cyres and the Teign valley.

The Spi Group: a post-Archean, pre-2.1 Ga rift succession, Trans-Hudson hinterland

1991 ◽  
Vol 28 (11) ◽  
pp. 1863-1872 ◽  
Author(s):  
Judith G. Patterson
Keyword(s):  
Alluvial Fan ◽  
History Of ◽  
Group A ◽  
Hurwitz Group ◽  
Archean Basement

A succession of mafic flows intercalated with sandstone and overlain by conglomerate, herein named the Spi Group, lies unconformably on Archean basement and is preserved in a syncline near Spi Lake, N.W.T. An alluvial fan setting near active rift fault escarpments is the interpreted environment of deposition. The nearby Montgomery Lake Group, Mackenzie Lake metasediments, and Padlei Formation at the base of the Hurwitz Group are possible correlatives of the Spi Group; diabase dykes of the Kaminak swarm, common in the Archean basement, are possibly related to the mafic flows. Correlation with the upper, coarse clastic part of the Hurwitz Group (Tavani Formation) is discounted because the Spi conglomerate does not contain clasts of Hurwitz lithology. The Montgomery Lake, Padlei and Spi successions are interpreted as being rift-related, and are older than the 2.1 Ga gabbro that intrudes the Hurwitz Group. Recognition of widespread rifting in this part of the Hearne Province constrains tectonic modelling of the preorogenic history of the Trans-Hudson hinterland.

scholarly journals Structural outline and development

1982 ◽  
Vol 8 ◽  
pp. 9-26
Author(s):  
Claus Andersen ◽  
Jens Christian Olsen ◽  
Olaf Michelsen ◽  
Erik Nygaard
Keyword(s):  
North Sea ◽  
Early Cretaceous ◽  
Southern North Sea ◽  
The North ◽  
Moray Firth ◽  
History Of ◽  
The North Sea ◽  
Broad Complex ◽  
East West ◽  
German Basin

The Central Graben is a broad, complex trough with a long history of differential subsidence. It was probably initiated in the Permian and was controlled by major rifting during the Mesozoic. To the south in the Dutch sector the trough is divided into two parts. From here it passes northwards and divides the southern North Sea Basin into the Anglo-Dutch Basin and the Northwest German Basin. It also separates the Mid North Sea High from the Ringkøbing-Fyn High. These highs form broad, east-west trending, relative stable ridges. The further continuation of the Central Graben is to the northwest, towards the centre of the North Sea, where it passes into the Viking Graben and the Moray Firth Basin at about 58° N. Where the Central Graben divides the two major highs, there is an elongate central narrow horst, the Dogger High, which is the southernmost of a row of mid-Graben highs. Both sides of the Graben are clearly defined by normal rotational faults that were intermittently active from Triassic to Early Cretaceous times.

An assessment of leaf-litter and epigaeic ants (Hymenoptera: Formicidae) living in different landscapes of the Atlantic Forest Biome in the State of Bahia, Brazil

2017 ◽  
Vol 5 (19) ◽  
pp. 1 ◽  
Author(s):  
Roberta De Jesus Santos ◽  
Elmo Borges Azevedo Koch ◽  
Clarissa Machado Pinto Leite ◽  
Tiago Jordão Porto ◽  
Jacques Hubert Charles Delabie
Keyword(s):  
Leaf Litter ◽  
Atlantic Forest ◽  
The State ◽  
Brazilian Atlantic Forest ◽  
The North ◽  
Forest Remnants ◽  
Axis Parallel ◽  
Leaf Litter Ants ◽  
South Axis ◽  
East West

The Brazilian Atlantic Forest has a rich biodiversity increasingly threatened by human activities. Since the colonial period, the coast of the state of Bahia is among the most affected regions of Brazil by anthropic pressure. Bahia encloses Atlantic Forest remnants distributed in an area reaching 100-200 km along the east-west axis, by 1,000 km along the north-south axis, parallel to the coast of the Atlantic Ocean. We report hereafter the results of an intensive field survey of leaf litter and epigaeic ants realized in forest remnants of the Atlantic Forest landscapes within the original extension of the biome in 11 localities distributed along four degrees of latitude in the state of Bahia. In each site, 16 plots were collected using pitfall and eight using Winkler traps. We identified 391 ant species belonging to 71 genera and nine subfamilies. Among all species recorded, 21 were common to the whole 11 localities, while 98 species were recorded in a single locality. This study highlights the richness and diversity of epigaeic and leaf-litter ants living in the northern part of the Brazilian Atlantic Forest, and is one of the most representative soil ants’ inventories ever done in this biome for a single state of Brazil.

ARCHAEAN SEDIMENTARY ROCKS OF NORTH SPIRIT LAKE AREA, NORTHWESTERN ONTARIO

1965 ◽  
Vol 2 (6) ◽  
pp. 622-647 ◽  
Author(s):  
J. A. Donaldson ◽  
G. D. Jackson
Keyword(s):  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Sole Source ◽  
Lake Area ◽  
Red Lake ◽  
Sedimentary Sequences ◽  
The North ◽  
Northwestern Ontario ◽  
History Of ◽  
Granitoid Rocks

Archaean sedimentary rocks of the North Spirit Lake area show little evidence of having been derived predominantly from associated Archaean volcanic rocks. Instead, compositions of the sediments reflect significant sedimentary and (or) granitoid provenance. A remarkably high content of clastic quartz in thick units of sandstone and conglomerate suggests either reworking of older quartzose sediments, or reduction of the labile constituents in quartz-rich granitoid rocks through prolonged weathering and rigorous transport. Observations for other sedimentary sequences in the region between Red Lake and Lansdowne House suggest that the North Spirit sediments are not unique in the Superior Province. Quartzose sandstones commonly are regarded as atypical of the Archaean, but such rocks arc abundant in northwestern Ontario. Frameworks of many Archaean greywackes actually are richer in quartz than typical greywackes from numerous Proterozoic and Phanerozoic sequences.The concept of rapidly rising volcanic arcs as the sole source of Archaean sedimentary detritus is rejected for the North Spirit area. The volcanies, rather than representing relicts of protocontinents, probably record events removed from initial volcanism in the history of the earth by one or more orogenic cycles. Major unconformities may therefore exist not only between sedimentary and volcanic units, but also between these units and older granitoid rocks.

scholarly journals Urban network in Poland during last millennium

2020 ◽  
Vol 33 (5) ◽  
pp. 7-20
Author(s):  
Iwona Jażdżewska
Keyword(s):  
Central And Eastern Europe ◽  
Last Millennium ◽  
The Baltic Sea ◽  
Urban Settlement ◽  
Urban Network ◽  
The North ◽  
History Of ◽  
Grand Duchy Of Lithuania ◽  
The Baltic ◽  
East West

The article attempts to find in the history of Poland facts and processes that influenced the contemporary shape of the Polish urban network. In comparison with other parts of Europe, the process of urbanisation in Central and Eastern Europe was significantly delayed. During the last millennium, the Polish state changed its borders many times, mainly in the east-west direction, because the Baltic Sea from the north and the Sudeten and Carpathian ranges from the south effectively inhibited territorial changes in the north-south direction. The process of shaping and strengthening the urban settlement network in Poland to the present day has been divided into five periods. The first, lasting from the 8th century until the union of Kreva in 1385, encompasses the beginnings of the establishment and spreading of urban settlement network; the second – the merger of the urban network with the Grand Duchy of Lithuania and its strengthening in the joint state; the third – the disappearance of Poland from the map of Europe and the breakup of the settlement network into three parts: tsarist Russia, the Habsburg monarchy, Prussia, and the start of industrialisation of the partitioned land; the fourth refers to the period when Poland, after 123 years, reappeared on the administrative map of Europe (1918-1939); and the fifth one covers the period from 1945 to the present day. When undertaking scientific research on the contemporary urban network of Poland, many political, social and economic factors should be taken into account. These should be taken into account when making hypotheses, drawing conclusions and developing economic and geographical theories.

PATRONS OF SHAMANIC POWER

1999 ◽  
Vol 10 (2) ◽  
pp. 169-188 ◽  
Author(s):  
Carolyn E. Tate
Keyword(s):  
Gulf Coast ◽  
High Mountain ◽  
Ritual Practice ◽  
The North ◽  
The Earth ◽  
Maize Plants ◽  
Isthmus Of Tehuantepec ◽  
The Many ◽  
South Axis ◽  
East West

This article takes two new approaches to the “enigmas” of La Venta. First, it examines the form of the site in relation to the region from which the La Ventans procured their stone: primarily, the Isthmus of Tehuantepec. La Venta's north–south axis pointed to the nearest high mountain south of the site. The bar-and-four-dots design on the Mosaic Pavements corresponded to the duality of the female earth and its four-directional maize plants crossed by the east–west path of the male sun. The Massive Offerings, previously interpreted as effigies of seas, are noted to be on the north of the ceremonial court and to correspond to the ocean a few kilometers north of the site. Second, this paper augments the current understanding of the ideological or spiritual motivations for the design and construction of La Venta's Massive Offerings and Mosaic Pavements by looking through the lens of contemporary Mixe ritual practice and shamanic cosmology. The Mixe are probably the linguistic descendants of the Gulf Coast Olmecs. Using these two lines of analysis, the paper advances several related proposals. It argues that the La Ventans planned Complexes A and C (the designations for the ceremonial court containing the Massive Offerings and other deposits and for the big mound) to replicate the topography of the region important to La Venta as a source of materials and food and, by extension, of knowledge. It specifically correlates the Massive Offerings, Mosaic Pavements, and almond-eyed supernaturals on stelae at the foot of Mound C to the principal “supernatural reality configurations” of the contemporary Mixe. Furthermore, it contextualizes the problem of shamanism by arguing that these supernaturals were not “gods” but sources of shamanic power and that the many buried offerings at La Venta are best seen as similar to aspects of Mixe ritual, which they call “work of the earth.” Finally, the paper reconsiders the existence of “gods” among the Olmecs, concluding that a more appropriate way to express their notions of the sacred is that they conceived supernaturals as meta-cosmological or meta-meteorological forces.

Sign in / Sign up

Export Citation Format

Share Document