scholarly journals Evidence for the generation of juvenile granitic crust during continental extension, Mineral Mountains Batholith, Utah

1992 ◽  
Vol 97 (B7) ◽  
pp. 11011 ◽  
Author(s):  
Drew S. Coleman ◽  
J. Douglas Walker
Keyword(s):  
Continental Extension

Attachments European-Style: A Continental Extension and Critique

1989 ◽  
Vol 34 (3) ◽  
pp. 260-261
Author(s):  
Mark T. Greenberg
Keyword(s):  
Continental Extension

Neoproterozoic extension in the Greater Dharwar Craton: a reevaluation of the “Betsimisaraka suture” in MadagascarThis article is one of a series of papers published in this Special Issue on the theme of Geochronology in honour of Tom Krogh.

2011 ◽  
Vol 48 (2) ◽  
pp. 389-417 ◽  
Author(s):  
R. D. Tucker ◽  
J.-Y. Roig ◽  
C. Delor ◽  
Y. Amelin ◽  
P. Goncalves ◽  
...  
Keyword(s):  
Dharwar Craton ◽  
High Grade ◽  
Grade Metamorphism ◽  
Continental Extension ◽  
Shrimp Geochronology ◽  
Igneous Activity ◽  
High Grade Metamorphism ◽  
Local Inversion ◽  
Metaigneous Rocks ◽  
Eastern Domain

The Precambrian shield of Madagascar is reevaluated with recently compiled geological data and new U–Pb sensitive high-resolution ion microprobe (SHRIMP) geochronology. Two Archean domains are recognized: the eastern Antongil–Masora domain and the central Antananarivo domain, the latter with distinctive belts of metamafic gneiss and schist (Tsaratanana Complex). In the eastern domain, the period of early crust formation is extended to the Paleo–Mesoarchean (3.32–3.15 Ga) and a supracrustal sequence (Fenerivo Group), deposited at 3.18 Ga and metamorphosed at 2.55 Ga, is identified. In the central domain, a Neoarchean period of high-grade metamorphism and anatexis that affected both felsic (Betsiboka Suite) and mafic gneisses (Tsaratanana Complex) is documented. We propose, therefore, that the Antananarivo domain was amalgamated within the Greater Dharwar Craton (India + Madagascar) by a Neoarchean accretion event (2.55–2.48 Ga), involving emplacement of juvenile igneous rocks, high-grade metamorphism, and the juxtaposition of disparate belts of mafic gneiss and schist (metagreenstones). The concept of the “Betsimisaraka suture” is dispelled and the zone is redefined as a domain of Neoproterozoic metasedimentary (Manampotsy Group) and metaigneous rocks (Itsindro–Imorona Suite) formed during a period of continental extension and intrusive igneous activity between 840 and 760 Ma. Younger orogenic convergence (560–520 Ma) resulted in east-directed overthrusting throughout south Madagascar and steepening with local inversion of the domain in central Madagascar. Along part of its length, the Manampotsy Group covers the boundary between the eastern and central Archean domains and is overprinted by the Angavo–Ifanadiana high-strain zone that served as a zone of crustal weakness throughout Cretaceous to Recent times.

scholarly journals Potential geographic distribution of the tiger mosquito Aedes albopictus (Skuse, 1894) (Diptera: Culicidae) in current and future conditions for Colombia

2021 ◽  
Vol 15 (5) ◽  
pp. e0008212
Author(s):  
Emmanuel Echeverry-Cárdenas ◽  
Carolina López-Castañeda ◽  
Juan D. Carvajal-Castro ◽  
Oscar Alexander Aguirre-Obando
Keyword(s):  
At Risk ◽  
Aedes Albopictus ◽  
Geographic Distribution ◽  
Ecological Niche ◽  
Ecological Niche Models ◽  
Niche Modelling ◽  
Continental Extension ◽  
Bioclimatic Variables ◽  
Valle Del Cauca ◽  
Potential Geographic Distribution

In Colombia, little is known on the distribution of the Asian mosquito Aedes albopictus, main vector of dengue, chikungunya, and Zika in Asia and Oceania. Therefore, this work sought to estimate its current and future potential geographic distribution under the Representative Concentration Paths (RCP) 2.6 and 8.5 emission scenarios by 2050 and 2070, using ecological niche models. For this, predictions were made in MaxEnt, employing occurrences of A. albopictus from their native area and South America and bioclimatic variables of these places. We found that, from their invasion of Colombia to the most recent years, A. albopictus is present in 47% of the country, in peri-urban (20%), rural (23%), and urban (57%) areas between 0 and 1800 m, with Antioquia and Valle del Cauca being the departments with most of the records. Our ecological niche modelling for the currently suggests that A. albopictus is distributed in 96% of the Colombian continental surface up to 3000 m (p < 0.001) putting at risk at least 48 million of people that could be infected by the arboviruses that this species transmits. Additionally, by 2050 and 2070, under RCP 2.6 scenario, its distribution could cover to nearly 90% of continental extension up to 3100 m (≈55 million of people at risk), while under RCP 8.5 scenario, it could decrease below 60% of continental extension, but expand upward to 3200 m (< 38 million of people at risk). These results suggest that, currently in Colombia, A. albopictus is found throughout the country and climate change could diminish eventually its area of distribution, but increase its altitudinal range. In Colombia, surveillance and vector control programs must focus their attention on this vector to avoid complications in the national public health setting.

scholarly journals Paleomagnetic Rotation Study of Woodlark-Australia plate motions in the Woodlark Rift, SE Papua New Guinea

2021 ◽  
Author(s):  
◽  
Elizabeth Ann Cairns
Keyword(s):  
Papua New Guinea ◽  
Vertical Axis ◽  
The South ◽  
Clockwise Rotation ◽  
Plate Motions ◽  
Continental Extension ◽  
Woodlark Basin ◽  
Australian Plate ◽  
Anticlockwise Rotation ◽  
Oceanic Spreading

<p>The Woodlark Rift in SE Papua New Guinea is a continental rift to the west of active oceanic spreading in the Woodlark Basin, which separates the Australian Plate to the south from the relatively anticlockwise rotating Woodlark Plate to the north. During Pliocene to Recent times the Woodlark Rift has been the setting for rapid exhumation of the world’s youngest UHP rocks (Baldwin et al., 2004, 2008; Gordon et al, 2012; Little et al., 2011), and is currently one of few places on the globe where active continental breakup is occurring ahead of a propagating oceanic spreading centre. While the Woodlark Basin contains a record of oceanic spreading since ˜6 Ma (Taylor et al., 1999), and GPS data describe present-day crustal motions (Wallace et al., manuscript in review), the Neogene temporal and kinematic evolution of continental extension in the Woodlark Rift is less well constrained. We compare Characteristic magnetization directions for six formations, Early Miocene (˜20 Ma) to Late Pliocene (3 ± 0.5), with contemporaneous expected field directions corresponding to Australian Plate paleomagnetic pole locations. We interpret declination anomalies (at 95% confidence) to estimate finite vertical-axis rotations of crustal blocks with respect to a fixed Australian Plate. Temporal and spatial relationships between declination anomalies for six formation mean directions, across four paleomagnetic localities, provide new evidence to constrain aspects of the Miocene to Recent history of the Woodlark Rift.  We obtained 250 oriented core samples from Miocene to Pliocene aged rocks at four localities in the Woodlark Rift. Components of Characteristic Remanent Magnetization (ChRM) have been determined from step-wise thermal and alternating field demagnetization profiles of >300 individual specimens. A total of 157 ChRM components contribute to the calculation of representative paleomagnetic directions for six formations, which have undergone vertical-axis rotations with respect to the Australian Plate associated with development of the Woodlark Rift.  Pliocene volcanic rocks at two key localities near the northern extent of the rift record that: 1) The Amphlett Islands has experienced 10.1 ± 7.6° of anticlockwise rotation since 3 ± 0.5 Ma; 2) NW Normanby Island has undergone a 16.3 ± 9.5° clockwise rotation during the same time interval. Sedimentary rocks at Cape Vogel Peninsula on the northern coast of the mainland Papuan Peninsula, record variable anticlockwise finite rotations of 28.4 ± 10.9° and 12.4 ± 5.5° for Early and Middle Miocene rocks respectively, in contrast to a younger clockwise rotation of 6.5 ± 11.2° for Late Miocene rocks. At the Suau Coast locality, on the south eastern coast of the Papuan Peninsula, Late Miocene dikes record 22.7 ± 13.3° of anticlockwise rotation.  At the Amphlett Islands and NW Normanby localities paleomagnetic data are consistent with current GPS plate motions, suggesting the current kinematics in the rift were established by at least ˜3 Ma. The Amphlett Islands result is consistent with the rate of Pliocene sea floor spreading in the Woodlark Basin, suggesting that locality can be considered as fully on the Woodlark Plate. The clockwise rotation indicated at NW Normanby Island may record development of an incipient dextral transfer fault within an active part of the Woodlark Rift.  Time-varying declination anomalies from the Cape Vogel Peninsula suggest that rifting began there by ˜15 Ma, 7 Ma earlier than previously inferred based on stratigraphic evidence. Furthermore, paleomagnetic data from the south coast of the Papuan Peninsula suggests that early rifting extended further south, and has since contracted to where continental extension is currently accommodated north of the Papuan Peninsula.</p>

scholarly journals The Skytrain plate and tectonic evolution of southwest Gondwana since Jurassic times

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Graeme Eagles ◽  
Hannes Eisermann
Keyword(s):  
Tectonic Evolution ◽  
Drake Passage ◽  
Weddell Sea ◽  
Falkland Islands ◽  
South American ◽  
Long Distance ◽  
Oblique Collision ◽  
Scotia Sea ◽  
Continental Extension ◽  
Pacific Margin

AbstractUncertainty about the structure of the Falkland Plateau Basin has long hindered understanding of tectonic evolution in southwest Gondwana. New aeromagnetic data from the basin reveal Jurassic-onset seafloor spreading by motion of a single newly-recognized plate, Skytrain, which also governed continental extension in the Weddell Sea Embayment and possibly further afield in Antarctica. The Skytrain plate resolves a nearly century-old controversy by requiring a South American setting for the Falkland Islands in Gondwana. The Skytrain plate’s later motion provides a unifying context for post-Cambrian wide-angle paleomagnetic rotation, Cretaceous uplift, and post-Permian oblique collision in the Ellsworth Mountains of Antarctica. Further north, the Skytrain plate’s margins built a continuous conjugate ocean to the Weddell Sea in the Falkland Plateau Basin and central Scotia Sea. This ocean rules out venerable correlation-based interpretations for a Pacific margin location and subsequent long-distance translation of the South Georgia microcontinent as the Drake Passage gateway opened.

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