Catalogo Articoli (Spogli Riviste)

OPAC HELP

Titolo:
MIDCRETACEOUS TRANSTENSION IN THE CANADIAN CORDILLERA - EVIDENCE FROMTHE ROCKY RIDGE VOLCANICS OF THE SKEENA GROUP
Autore:
BASSETT KN; KLEINSPEHN KL;
Indirizzi:
UNIV CALIF SANTA BARBARA,DEPT GEOL SCI SANTA BARBARA CA 93106 UNIV MINNESOTA,DEPT GEOL & GEOPHYS MINNEAPOLIS MN 55455
Titolo Testata:
Tectonics
fascicolo: 4, volume: 15, anno: 1996,
pagine: 727 - 746
SICI:
0278-7407(1996)15:4<727:MTITCC>2.0.ZU;2-H
Fonte:
ISI
Lingua:
ENG
Soggetto:
CENTRAL BRITISH-COLUMBIA; COAST PLUTONIC COMPLEX; BACK-ARC BASIN; CENTRAL SOUTHEASTERN ALASKA; YUKON-TANANA TERRANE; SPENCES-BRIDGE-GROUP; ISLAND-ARC; CHEMICAL CLASSIFICATION; PALEOMAGNETIC EVIDENCE; TECTONIC IMPLICATIONS;
Tipo documento:
Review
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
120
Recensione:
Indirizzi per estratti:
Citazione:
K.N. Bassett e K.L. Kleinspehn, "MIDCRETACEOUS TRANSTENSION IN THE CANADIAN CORDILLERA - EVIDENCE FROMTHE ROCKY RIDGE VOLCANICS OF THE SKEENA GROUP", Tectonics, 15(4), 1996, pp. 727-746

Abstract

The age relations, geochemistry, and sedimentology of the Rocky RidgeFormation of the Skeena Group are used to rest competing tectonic reconstructions for the mid-Cretaceous Canadian Cordillera as well as thetiming and location of the accretion of the Insular Superterrane. Pollen and macrofossil assemblages indicate that these intrabasinal basalts were erupted along the southern margin of the Bowser basin in the Early Albian to Early Cenomanian. Single-crystal fusion and step-heating Ar-40/Ar-39 dating of hornblendes in one basalt flow from the uppermost part of the formation yielded Middle Cenomanian ages of 94.3 +/- 0.4, 95.6 +/- 1.6, and 95.0 +/- 1.6 Ma. Vesicular basalt flows interbedded with crystal-rich tuff breccias contain evidence for hot emplacement as pyroclastic flows. Individual eruptive centers are identified bytheir proximal facies, paleoflow indicators within the lava flows, paleoflow indicators within interbedded volcaniclastic fluvial deposits,geochemical differences, and geographic isolation of volcanic deposits. Major and trace-element geochemistry from 20 sampled lava flows indicates an alkali basalt composition for the volcanics. The basalts of the northern Rocky Ridge volcanic center show enrichment of light rareearth and large ion lithophile elements with strong negative Nb-Ta anomalies whereas the basalts of the southern Tahtsa Lake volcanic center show depletion to slight enrichment of light rare earth elements, slight enrichment of large ion lithophile elements with minimal negativeNb-Ta anomalies. The geochemistry combined with paleogeographic and regional tectonic reconstruction suggests a continental are setting with intraarc extension. The presence of deeper marine facies to the westand the lack of a western sediment source in the Skeena Group indicate that the tectonically active Insular Superterrane was not west of the study area during mid-Cretaceous time. Thus we reconsider the Omineca Belt as the main axis of a mid-Cretaceous continental are, placing the Intermontane Superterrane in the intraarc to forearc position with the Rocky Ridge volcanics erupted along the forearc side of the Omineca are. Coeval regional strike-slip faulting and reconstructed oblique plate convergence suggest a transtensional setting for Rocky Ridge intraarc extension.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 13/08/20 alle ore 14:33:02