Upper limit of docking time for Stikinia and Terrane I: paleomagnetic evidence from the Eocene Ootsa Lake Group, British Columbia

Abstract

The Middle Eocene Ootsa Lake Group is exposed in the central portion of the Stikine Terrane, where it was sampled along the shoreline of Tahtsa Reach and Whitesail Reach. The group consists of dominantly subaerial flows, which range in composition from basalt to rhyolite, that unconformably overly the Jurassic Hazelton Group. Detailed alternating-field and thermal stepwise demagnetizations were done on all specimens from the 21 sites collected. The presence of a normal- and reversed-polarity remanence, a positive fold test, and high coercivities and unblocking temperatures indicate that a prefolding primary remanence has been isolated. The mean tilt-corrected direction of D = 002.2°, I = 69.2 °(α95 = 7.4°) from 13 sites for which paleohorizontal is well known yields a pole position at 354.6°E, 88.0°N (A95 = 11.5°), which is statistically indistinguishable from published 50 Ma reference poles for cratonic North America. This evidence demonstrates that the proposed large-scale northward displacement of Stikinia since mid-Cretaceous was completed by at least Middle Eocene time. This result is consistent with other paleomagnetic results from Stikinia, Quesnellia, and the Coast Plutonic Complex indicating that much of the allochthonous Cordillera had assembled and docked with cratonic North America by the Middle Eocene.

Rethinking “Yellowstone in Yukon” and Baja British Columbia: Paleomagnetism of the Late Cretaceous Swede Dome stock, northern Canadian Cordillera

“… b Numbered references: 1, Symons et al [2000]; 2, Vandall and Palmer [1990]; 3, Johnston et al [1996]; 4, Wynne et al [1998]; 5, Enkin et al [2003]; 6, Harris et al [1999]; 7, Vandall [1992]; 8, Wynne et al [1995]; 9, Wynne et al [1995]; 10, Haskin et al [2003]; 11, McCausland et al [2005]; 12, Harris et al [1996]; 13. Harris et al [1997]; 14, Fox and Beck [1985]; 15, McCausland [2002]; 16, Symons and Wellings [1989]; 17, McCausland et al [2001]; 18, Symons [1977]; 19, Symons et al [2004]; 20, Bardoux and Irving [1989]. …”

Tertiary extension and tilting in the Queen Charlotte Islands, evidence from dyke swarms and their paleomagnetism

“…Paleomagnetic data from bedded Eocene rocks that are concordant with data from cratonic North America have now been obtained from across the Cordillera in Canada and adjacent U.S.A., implying that the major elements of the Canadian Cordillera were all in their present relative latitudinal position by Mid-Eocene time (Fox and Beck 1985;Bardoux and Irving 1989;Symons and Welling 1989;Bardoux and Irving 1989;Irving and Brandon 1990;Vandall and Palmer 1990). Because of this, aberrant magnetizations in Eocene and younger rocks can be interpreted as being caused by tilting or by rotations.…”

Paleomagnetism and Microplate Tectonics

“…Northward displacements (though smaller) and vertical‐axis rotations are also implied by data acquired from the Lower Jurassic Bonanza Group of Vancouver Island [ Irving and Yole , 1987] and the Sylvester Allochthon of north‐central British Columbia [ Butler et al , 1988]. Paleomagnetic data for the Eocene Kamloops Group [ Symons and Wellings , 1989], Marron volcanics [ Bardoux and Irving , 1989], Flores volcanics [ Irving and Brandon , 1990], and Ootsa Lake Group [ Vandall and Palmer , 1990] of British Columbia all indicate that displacements in the region were completed by early to middle Eocene time.…”