|Title||The Jurassic succession at Lisadele Lake (Tulsequah map area, British Columbia, Canada) and its bearing on the tectonic evolution of the Stikine terrane|
|Author||Shirmohammad, F; Smith, P L; Anderson, R G; McNicoll, V J|
|Source||Volumina Jurassica vol. 9, no. 1, 2011 p. 43-59 Open
|Alt Series||Earth Sciences Sector, Contribution Series 20080497|
|Publisher||NRC Research Press|
|Media||paper; on-line; digital|
|Subjects||geochronology; general geology; conglomerates; clasts; clastic facies; cherts; mudstones; zircon dates; radiometric dating; Bowser Lake Group; Jurassic|
|Program||Targeted Geoscience Initiative (TGI-3), 2005-2010 |
|Released||2011 01 01|
|Abstract||Jurassic rocks in the central Tulsequah map area include conglomerates and interbedded fossiliferous finer clastics of the Takwahoni Formation (Laberge Group) which unconformably overlie Triassic rocks.
Ammonite collections document the Pliensbachian, Toarcian and Bajocian stages. We refine the age and provenance of episodes of coarse clastic input and confirm the progressive change of dominant clast lithology from reworked sedimentary rocks above
the Triassic-Jurassic unconformity to volcanic, plutonic and then metamorphic clasts in the Upper Toarcian. The uppermost coarse clastic unit is a Bajocian chert-pebble conglomerate which, along with the immediately underlying black mudstone, we
include in the Bowser Lake Group. Together with regional correlations, this confirms that the age of the basal part of the Bowser Lake Group is diachronous, younging southwards into Stikinia.|
Sandstone petrofacies trends and changes in
conglomerate clast composition indicate arc uplift and dissection followed by Middle Jurassic orogen recycling. The isotopic ages of detrital zircons and granite clasts compared with the biochronologically constrained ages of the enclosing strata
suggests that processes of intrusion, arc uplift, unroofing, and clastic deposition during the Early Jurassic occurred over intervals of significantly less than five million years.