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Dive into the research topics where Rory R. McFadden is active.

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Featured researches published by Rory R. McFadden.


Geological Society of America Bulletin | 2012

Evidence for middle Eocene and younger land emergence in central Panama: Implications for Isthmus closure

Camilo Montes; Augusto V. Cardona; Rory R. McFadden; Sara Morón; C.A. Silva; Sergio A. Restrepo-Moreno; Diego A. Ramírez; N. Hoyos; J. Wilson; David W. Farris; Germán Bayona; Carlos Jaramillo; Victor A. Valencia; J. Bryan; José-Abel Flores

The rise of the Isthmus of Panama, linked to a number of climatic, paleoceanographic, and biological events, has been studied mostly from indirect, often distal, geochemical and biotic evidence. We have upgraded existing geologic mapping in central Panama with more than 2000 field stations, over 40 petrographic analyses, and more than 30 new geochronological and thermochronological analyses. This data set suggests that the isthmus was an uninterrupted chain above sea level from late Eocene until at least late Miocene times. The basement complex of central Panama is a folded-faulted, ∼3-km-thick arc sequence, intruded by granitoid bodies and onlapped by mildly deformed upper Eocene and Oligocene strata. Six U/Pb zircon ages in the granitoids–along with published geochronological data—reveal intense late Paleocene to middle Eocene magmatism (58–39 Ma), a temporary cessation of magmatic activity between 38 and 27 Ma, and renewed magmatism between 25 and 15 Ma in a position ∼75 km south of the former magmatic axis. Thermochronological analyses in zircon (eight U-Th/He ages), and in apatite crystals (four U-Th/He ages and nine fission-track ages) obtained from a subset of 58–54 Ma granitoid bodies record a concordant Lutetian-age (47–42 Ma) cooling from ∼200 °C to ∼70 °C in ∼5 m.y., and cooling below ∼40 °C between 12 and 9 Ma. Cooling is linked to exhumation by an angular unconformity that separates the deformed basement complex below from mildly deformed, upper Eocene to Oligocene terrestrial to shallow-marine strata above. Exhumation and erosion of the basement complex are independently confirmed by lower Miocene strata that have a detrital zircon signature that closely follows the central Panama basement complex age distribution. These results greatly restrict the width and depth of the strait separating southern Central America from South America, and challenge the widely accepted notion that the Central American Seaway closed in late Pliocene time, when the ice age began.


Geology | 2010

Oblique dilation, melt transfer, and gneiss dome emplacement

Rory R. McFadden; Christian Teyssier; Christine S. Siddoway; Donna L. Whitney; Christopher Fanning

The upward transfer of partially molten crust and the formation of gneiss domes and metamorphic core complexes commonly take place by localization of normal or oblique extension in the middle and upper crust. In Marie Byrd Land, Antarctica, a transition from wrench to oblique extension occurred during oblique plate divergence along the East Gondwana margin and intracontinental crustal extension associated with the West Antarctic Rift System in mid-Cretaceous time. Migmatites in the Fosdick dome record steep fabrics formed during wrenching, and associated granite networks display crystallization ages of 117–115 Ma. These steep fabrics are overprinted by subhorizontal foliation and leucogranite sheets with crystallization ages in the 109–102 Ma range. Syntectonic emplacement of granite sheets in the South Fosdick detachment zone indicates that detachment tectonics led to rapid exhumation of the terrain by 100 Ma. This study has implications for understanding melt transport, magma accumulation, and the formation of detachments in an oblique tectonic setting.


Geological Society, London, Special Publications | 2013

Anatectic reworking and differentiation of continental crust along the active margin of Gondwana: A zircon Hf-O perspective from West Antarctica

Chris Yakymchuk; Christine S. Siddoway; C. Mark Fanning; Rory R. McFadden; Fawna J. Korhonen; Michael Brown

Abstract The Fosdick migmatite–granite complex of West Antarctica preserves evidence of two crustal differentiation events along a segment of the former active margin of Gondwana, one in the Devonian–Carboniferous and another in the Cretaceous. The Hf–O isotope composition of zircons from Devonian–Carboniferous granites is explained by mixing of material from two crustal sources represented by the high-grade metamorphosed equivalents of a Lower Palaeozoic turbidite sequence and a Devonian calc-alkaline plutonic suite, consistent with an interpretation that the Devonian–Carboniferous granites record crustal reworking without input from a more juvenile source. The Hf–O isotope composition of zircons from Cretaceous granites reflects those same two sources, together with a contribution from a more juvenile source that is most evident in the detachment-hosted, youngest granites. The relatively non-radiogenic ϵHf isotope characteristics of zircons from the Fosdick complex granites are similar those from the Permo-Triassic granites from the Antarctic Peninsula. However, the Fosdick complex granites contrast with coeval granites in other localities along and across the former active margin of Gondwana, including the Tasmanides of Australia and the Western Province of New Zealand, where the wider range of more radiogenic ϵHf values of zircon suggests that crustal growth through the addition of juvenile material plays a larger role in granite genesis. These new results highlight prominent arc-parallel and arc-normal variations in the mechanisms and timing of crustal reworking v. crustal growth along the former active margin of Gondwana. Supplementary material: Figs S1 and S2 are available at www.geolsoc.org.uk/SUP18625


Lithosphere | 2015

Eocene extension and meteoric fluid flow in the Wildhorse detachment, Pioneer metamorphic core complex, Idaho

Rory R. McFadden; Andreas Mulch; Christian Teyssier; Matthew T. Heizler

The relationship between microstructure and fluid flow traced by hydrogen isotope ratios (δD) is examined within the Wildhorse detachment system of the Pioneer metamorphic core complex in south-central Idaho. Within the detachment footwall, 100-m-thick mylonitic quartzite containing minor white mica and K-feldspar displays a NW-trending stretching lineation and consistent top-to-the-NW sense of shear criteria. Microstructures within the detachment footwall comprise two groups: quartz ribbons and relict quartz grains flattened within the foliation, with porphyroclastic white mica fish; and intensely deformed and recrystallized quartz with high-aspect-ratio white mica arranged within C′ shear bands. White mica δD values are highly negative and cluster around −145‰ in high-aspect-ratio white mica and around −120‰ in porphyroclastic white mica fish. The most negative values are interpreted to reflect interaction with meteoric fluids from a high-elevation catchment (3000−4000 m), and the less negative values are interpreted to represent incomplete hydrogen isotope exchange between the meteoric fluid and the pre-extensional metamorphic fluid δD values in the white mica porphyroclasts. A suite of tightly clustered 40 Ar/ 39 Ar ages from synkinematic white mica in the detachment footwall dates deformation, recrystallization, fluid-rock interaction, and therefore the presence of high topography at 38−37 Ma; these ages are consistent with the cooling/exhumation history of the high-grade core of the Pioneer metamorphic core complex in the late Eocene. The 38−37 Ma 40 Ar/ 39 Ar ages are substantially younger than previously published ages of high topography in British Columbia to the north (49−47 Ma), in line with the hypothesis that high topography propagated from north to south in the northern segment of the North American Cordillera through Eocene time.


Tectonics | 2010

Cretaceous oblique extensional deformation and magma accumulation in the Fosdick Mountains migmatite‐cored gneiss dome, West Antarctica

Rory R. McFadden; Christine S. Siddoway; Christian Teyssier; Christopher Fanning


Lithos | 2012

Age and origin of earliest adakitic-like magmatism in Panama: Implications for the tectonic evolution of the Panamanian magmatic arc system

Scott A. Whattam; Camilo Montes; Rory R. McFadden; Agustín Cardona; Diego A. Ramírez; Victor A. Valencia


Gondwana Research | 2013

Petrogenesis of Cretaceous mafic intrusive rocks, Fosdick Mountains, West Antarctica: Melting of the sub-continental arc mantle along the Gondwana margin

S. Saito; Michael Brown; F.J. Korhonen; Rory R. McFadden; Christine S. Siddoway


Open-File Report | 2007

Cretaceous oblique detachment tectonics in the Fosdick Mountains, Marie Byrd Land, Antarctica

Rory R. McFadden; Christine S. Siddoway; Christian Teyssier; Christopher Fanning; S. C. Kruckenberg


Geological Society of America Special Papers | 2006

Arc plutonism following regional thrusting: Petrology and geochemistry of syn- and post-Nevadan plutons in the Siskiyou Mountains, Klamath Mountains province, California

Calvin G. Barnes; Arthur W. Snoke; Gregory D. Harper; Carol D. Frost; Rory R. McFadden; Jonathan C. Bushey; Melanie A. Barnes


Lithos | 2015

Mid-Cretaceous oblique rifting of West Antarctica: Emplacement and rapid cooling of the Fosdick Mountains migmatite-cored gneiss dome

Rory R. McFadden; Christian Teyssier; Christine S. Siddoway; Michael A. Cosca; Christopher Fanning

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Christopher Fanning

Australian National University

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Diego A. Ramírez

Smithsonian Tropical Research Institute

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Victor A. Valencia

Washington State University

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Agustín Cardona

Smithsonian Tropical Research Institute

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C.A. Silva

Smithsonian Tropical Research Institute

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Carlos Jaramillo

Smithsonian Tropical Research Institute

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