scholarly journals Very low-grade metamorphism of the Dezadeash Formation (Jura-Cretaceous): Constraints on the tectonometamorphic history of the Dezadeash flysch basin and implications regarding the tectonic evolution of the Northern Cordillera of Alaska and Yukon

2021 ◽  
Vol 7 (3) ◽  
pp. 355-389
Author(s):  
Grant W Lowey ◽  
Keyword(s):  
Organic Matter ◽  
North America ◽  
Maximum Pressure ◽  
Low Grade ◽  
Oblique Collision ◽  
Western Margin ◽  
Facies Metamorphism ◽  
History Of ◽  
Thermal Indicators ◽  
Gravina Belt

<abstract> <p>Mesozoic convergence of the Wrangellia composite terrane with the western margin of North America resulted in the collapse of intervening flysch basins. One of these basins, the Jurassic-Cretaceous Gravina-Nuzotin belt, comprises from south to north, the Gravina sequence and Gravina belt in southeastern Alaska, the Dezadeash Formation in Yukon, and the Nutzotin Mountains sequence in eastern Alaska. Previous work shows that the Gravina sequence and Gravina belt were underthrust &gt; 20 km beneath the margin of North America in mid-Cretaceous time, culminating in amphibolite facies metamorphism. This tectonometamorphic scenario was subsequently applied to the entire Gravina-Nutzotin belt, despite any detailed studies pertaining to the tectonometamorphic evolution of the Dezadeash Formation. The present analysis of the Dezadeash Formation reveals that metamorphic mineral assemblages in sandstone and tuff document subgreenschist, high temperature zeolite facies metamorphism; Kübler indices of illite and Árkai indices of chlorite in mudstone record diagenetic to high anchizone metapelitic conditions; and the color of organic matter (i.e., the Thermal Alteration Index of palynomorphs and the Conodont Alteration Index) and pyrolysis of organic matter in mudstone and hemipelagite beds document thermal maturation at catagenesis to mesogenesis stages. Collectively, the mineralogic and organic thermal indicators in the Dezadeash Formation suggest that strata experienced maximum pressure-temperature conditions of 2.5 ± 0.5 kbar and 250 ± 25 ℃ in the Early Cretaceous. The inferred tectonometamorphic evolution of the Dezadeash Formation does not support the northern part of the Gravina-Nutzotin belt being underthrust &gt; 20 km beneath the western margin of North America in mid-Cretaceous time, thus contrasting sharply with the Gravina sequence and Gravina belt in the southern part of the Gravina-Nutzotin belt. The diverse tectonometamorphic histories recorded by the southern and northern parts of the Gravina-Nutzotin belt may be a manifestation of oblique collision and diachronous south-to-north accretion of the Wrangellia composite terrane to North America.</p> </abstract>

Terranes and terrane boundaries in the Sudetes, northeast Bohemian Massif

1997 ◽  
Vol 134 (5) ◽  
pp. 717-725 ◽  
Author(s):  
Z. CYMERMAN ◽  
M. A. J. PIASECKI ◽  
R. SESTON
Keyword(s):  
High Pressure ◽  
Central Region ◽  
Bohemian Massif ◽  
Low Grade ◽  
High Grade ◽  
High Pressure Granulite ◽  
Facies Metamorphism ◽  
History Of ◽  
Ophiolitic Rocks ◽  
Southwestern Margin

In the Sudetes, seven distinct lithostratigraphic terranes exhibit a symmetric distribution. A central region of basinal/oceanic and ophiolitic rocks, the Central Sudetic terrane is bordered, respectively to the northwest and southeast, by the sialic Saxothuringian and Moldanubian terranes. These exhibit contrasting metasedimentary/metavolcanic successions and tectonic-metamorphic sequences, but both are characterized by Palaeozoic plutonism. These are in turn bordered (again respectively to the northwest and southeast) by the Lusatian and Moravian terranes, which are also sialic, but contain Cadomian granitoids and represent rifted and now widely separated fragments of Gondwana. Along the southwestern flank of the Sudetes, the Barrandian terrane, largely covered by younger sediments, extends to the southwestern margin of the Bohemian Massif. The Sowie Góry terrane forms a klippe of high grade gneisses tectonically emplaced on top of low-grade, sheared ophiolites of the Central Sudetic terrane. The Sowie Góry terrane exhibits a history of three distinct, probably multi-orogenic, regional metamorphic events: an early high-pressure granulite/eclogite metamorphism followed by medium- to low-pressure granulite, and in turn by amphibolite facies metamorphism. All the terrane boundaries are complex zones of ductile to brittle shearing, modified by later brittle movements. Some, such as the Leszczyniec shear zone, mark lines of old, pre-Variscan rift and suture zones, reactivated and overprinted during a series of Variscan ductile to brittle events of extensional shearing with related metamorphism and plutonism.

Elements for a General Organology

Derrida Today ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 72-94
Author(s):  
Bernard Stiegler
Keyword(s):  
Organic Matter ◽  
Planetary Scale ◽  
General Account ◽  
Inorganic Matter ◽  
History Of

These lectures outline the project of a general organology, which is to say an account of life when it is no longer just biological but technical, or when it involves not just organic matter but organized inorganic matter. This organology is also shown to require a modified Simondonian account of the shift from vital individuation to a three-stranded process of psychic, collective and technical individuation. Furthermore, such an approach involves extending the Derridean reading of Socrates's discussion of writing as a pharmakon, so that it becomes a more general account of the pharmacological character of retention and protention. By going back to Leroi-Gourhan, we can recognize that this also means pursuing the history of retentional modifications unfolding in the course of the history of what, with Lotka, can also be called exosomatization. It is thus a question of how exteriorization can, today, in an epoch when it becomes digital, and in an epoch that produces vast amounts of entropy at the thermodynamic, biological and noetic levels, still possibly produce new forms of interiorization, that is, new forms of thought, care and desire, amounting to so many chances to struggle against the planetary-scale pharmacological crisis with which we are currently afflicted.

Evolution of the Paran drainage basin and its relation to the Plio-Pleistocene history of the Arava Rift western margin, Israel

2000 ◽  
Vol 49 (4) ◽  
pp. 215-238 ◽  
Author(s):  
Hanan Ginat ◽  
Yoav Avni ◽  
Zvi Garfunkel ◽  
Hanan Ginata ◽  
Yosef Bartov
Keyword(s):  
Drainage Basin ◽  
Western Margin ◽  
History Of

Primary acquired melanosis (PAM) without atypia/WHO low-grade conjunctival melanocytic intraepithelial lesion over areas of oculodermal melanocytosis

2020 ◽  
Vol 13 (10) ◽  
pp. e236741
Author(s):  
Bashar M Bata ◽  
Sachin M Salvi ◽  
Hardeep Singh Mudhar
Keyword(s):  
Bulbar Conjunctiva ◽  
Low Grade ◽  
Primary Acquired Melanosis ◽  
Conjunctival Biopsy ◽  
History Of ◽  
Intraepithelial Lesion ◽  
The Relationship ◽  
Oculodermal Melanocytosis ◽  
Substantia Propria ◽  
New Onset

An elderly white man with a history of left oculodermal melanocytosis presented with new onset brown pigmentation of the left bulbar and inferior tarsal conjunctiva. The bulbar conjunctival pigmentation was at the level of the conjunctival epithelium and was overlying areas of typical slate-grey scleral pigmentation characteristic of oculodermal melanocytosis. Both areas of new pigmentation were biopsied. The bulbar conjunctiva revealed primary acquired melanosis (PAM) without atypia with increased melanin production and the tarsal conjunctival biopsy showed PAM without atypia sine pigmentio overlying areas of substantia propria spindle-shaped heavily pigmented melanocytes of oculodermal melanocytosis. The case report examines the relationship between the epithelial and substantia propria melanocytes and correlates the findings with what is known about this association from the dermatopathology literature.

Identity of the oribatid mite Oribata curva and transfer to Trichogalumna (Acari, Oribatida, Galumnidae), with discussion of nomenclatural and biogeographical issues in the ‘curva’ species-group

Zootaxa ◽  
2017 ◽  
Vol 4272 (4) ◽  
pp. 551
Author(s):  
ROY A. NORTON ◽  
SERGEY G. ERMILOV
Keyword(s):  
North America ◽  
Oribatid Mite ◽  
Species Group ◽  
Type Material ◽  
Similar Species ◽  
History Of ◽  
Molecular Assessment

Based on the study of type material, other historical specimens, and new collections, the adult of the thelytokous oribatid mite Oribata curva Ewing, 1907 (Galumnidae) is redescribed and the name is recombined to Trichogalumna curva (Ewing, 1907) comb. nov. A confusing history of synonymies and misidentifications is traced in detail, and their effect on published statements about biogeography is assessed. Reliable records of T. curva are only those from North America. The tropical mite Pergalumna ventralis (Willmann, 1932) is not a subspecies of T. curva. The widely-reported Trichogalumna nipponica (Aoki, 1966) and other similar species form a complex with T. curva that needs further morphological and molecular assessment. 

scholarly journals I.—History of the Names Cambrian and Silurian in Geology

1873 ◽  
Vol 10 (111) ◽  
pp. 385-395 ◽  
Author(s):  
T. Sterry Hunt
Keyword(s):  
Great Britain ◽  
North America ◽  
Upper Cambrian ◽  
History Of ◽  
Lower Palaeozoic ◽  
The Subject

It is proposed in the following pages to give a concise account of the progress of investigation of the lower Palæozoic rocks during the last forty years. The subject may naturally be divided into three parts: 1. The history of Silurian and Upper Cambrian in Great Britain from 1831 to 1854; 2. That of the still more ancient Palæozoic rocks in Scandinavia, Bohemia, and Great Britain up to the present time, including the recognition by Barrande of the so-called primordial Palæozoic; fauna; 3. The history of the lower Palæozoic rocks of North America.

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