Emergent Basalt and Submergent Carbonate–Clastic Sequences Including the Upper Triassic Dilleri and Welleri Zones on Vancouver Island

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Abstract
Rates, depths, and some conditions of accumulation of epipelagic siliceous lime-shale, coarse bioclastic limestone, oceanic basalt flows, pillow lava, and pillow breccia are inferred from new biostratigraphic data, geometry of occurrence, and analogies between major and minor cyclical sequences. Sporadic thin assemblages of intravolcanic beds, pillowed basalt, and flows within the Karmutsen Subgroup reproduce on a minor scale the major sequence of pre-Karmutsen sediments followed by pillow lava, pillow breccia, and flows of the whole Karmutsen. The Dilleri Zone, documented in several new occurrences, includes not only the uppermost Karmutsen, but also almost the entire Quatsino Limestone, an aggregate thickness of 610-920 m, whereas eight ammonoid zones, from Welleri to Lower Suessi, are encompassed by 300-365 m of epipelagic lower Parson Bay Formation. Although recurrent extinction of benthos and increase in proportions of volcanic components, manifest both in microfacies of intravolcanic beds and in the major post-Karmutsen succession (Quatsino Limestone, Parson Bay, and Harbledown Formations), correlate with increasing depth of sedimentation, maximum depths even during deposition of epipelagic lime-shale were probably never more than 60 m. 'Porosity' of pillowed volcanics and aquagene tuff is discussed. The pillow–pillow breccia–flow sequence represents emergent, the sediments, submergent deposition.

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