Stratigraphy, depositional environment, and tectonic setting of the Upper Triassic to Middle Jurassic rocks of the Chilcotin Ranges, southwestern British Columbia

P. J. Umhoefer, H. W. Tipper

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A unique sequence of locally fossiliferous sedimentary rocks is exposed along the northeastern flank of the southern Coast Mountains in the Chilcotin Ranges. The Upper Triassic to middle Jurassic strata are part of the Cadwallader terrane and have been defined as the Upper Triasic Tyaughton Formation (?Middle and Late Norian age) and Lower to Middle Jurasic last Creek and Nemaia formations (Late Hettangian to Early Bajocian age). These formations have been further divided into members. Fossils have provided good age constraints. The Tyaughton Formation comprises about 600m shallow marine limestones and fluvial to shallow marine clastic rocks. The Last Creek Formation disconformably overlies the Tyaughton Formation and comprises at least 400m of nearshore clastic rocks that grade upward to offshore or slope facies. The newly defined Nemaia Formations is correlative to the Last Creek Formation and comprises about 1.5km of clastic rocks that grade from locally variable, but dominantly fine grained, Lower Jurassic offshore and slope facies up into Middle Jurassic delta facies.

Original languageEnglish (US)
JournalBulletin of the Geological Survey of Canada
Issue number519
StatePublished - Jan 1 1998


ASJC Scopus subject areas

  • Geology

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