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Titolo:
Kinematic analysis of melange fabrics: examples and applications from the McHugh Complex, Kenai Peninsula, Alaska
Autore:
Kusky, TM; Bradley, DC;
Indirizzi:
Boston Univ, Ctr Remote Sensing, Boston, MA 02215 USA Boston Univ Boston MA USA 02215 Ctr Remote Sensing, Boston, MA 02215 USA US Geol Survey, Anchorage, AK 99508 USA US Geol Survey Anchorage AK USA 99508 eol Survey, Anchorage, AK 99508 USA
Titolo Testata:
JOURNAL OF STRUCTURAL GEOLOGY
fascicolo: 12, volume: 21, anno: 1999,
pagine: 1773 - 1796
SICI:
0191-8141(199912)21:12<1773:KAOMFE>2.0.ZU;2-R
Fonte:
ISI
Lingua:
ENG
Soggetto:
CHUGACH ACCRETIONARY COMPLEX; SOUTH-CENTRAL ALASKA; SHIMANTO BELT; KODIAK-ISLANDS; SLIP VECTORS; STRUCTURAL EVOLUTION; 3-DIMENSIONAL STRAIN; PLATE CONVERGENCE; CRUSTAL TRANSECT; EPISODIC GROWTH;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
94
Recensione:
Indirizzi per estratti:
Indirizzo: Kusky, TM Boston Univ, Ctr Remote Sensing, 725 Commonwealth Ave, Boston, MA 02215 USA Boston Univ 725 Commonwealth Ave Boston MA USA 02215 A 02215 USA
Citazione:
T.M. Kusky e D.C. Bradley, "Kinematic analysis of melange fabrics: examples and applications from the McHugh Complex, Kenai Peninsula, Alaska", J STRUC GEO, 21(12), 1999, pp. 1773-1796

Abstract

Permian to Cretaceous mi lange of the McHugh Complex on the Kenai Peninsula, south-central Alaska includes blocks and belts of graywacke, argillite, limestone, chert, basalt, gabbro, and ultramafic rocks, intruded by a variety of igneous rocks. An oceanic plate stratigraphy is repeated hundreds of times across the map area, but most structures at the outcrop scale extend lithological layering. Strong rheological units occur as blocks within a matrix that flowed around the competent blocks during deformation, forming broken formation and melange. Deformation was noncoaxial, and disruption of primary layering was a consequence of general strain driven by plate convergence in a relatively narrow zone between the overriding accretionary wedge and the downgoing, generally thinly sedimented oceanic plate. Soft-sedimentdeformation processes do not appear to have played a major role in the formation of the melange. A model for deformation at the toe of the wedge is proposed in which layers oriented at low angles to al are contracted in boththe brittle and ductile regimes, layers at 30-45 degrees to sigma(1) are extended in the brittle regime and contracted in the ductile regime, and layers at angles greater than 45 degrees to sigma(1) are extended in both the brittle and ductile regimes. Imbrication in thrust duplexes occurs at deeper levels within the wedge. Many structures within mi lange of the McHugh Complex are asymmetric and record kinematic information consistent with the inferred structural setting in an accretionary wedge. A displacement field for the McHugh Complex on the lower Kenai Peninsula includes three belts: aninboard belt of Late Triassic rocks records west-to-east-directed slip of hanging walls, a central belt of predominantly Early Jurassic rocks recordsnorth-south directed displacements, and Early Cretaceous rocks in an outboard belt preserve southwest-northeast directed slip vectors. Although precise ages of accretion are unknown, slip directions are compatible with inferred plate motions during the general time frame of accretion of the McHugh Complex. The slip vectors are interpreted to preserve the convergence directions between the overriding and underriding plates, which became more oblique with time. They are not considered indicative of strain partitioning into belts of orogen-parallel and orogen-perpendicular displacements, becausethe kinematic data are derived from the earliest preserved structures, whereas fabrics related to strain partitioning would be expected to be superimposed on earlier accretion-related fabrics. (C) 1999 Elsevier Science Ltd. All rights reserved.

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Documento generato il 02/07/20 alle ore 19:01:37