The end-Triassic mass extinction is one of the five most catastrophic in Phanerozoic Earth history. Here we report carbon isotope evidence of a pronounced productivity collapse at the boundary, coincident with a sudden extinction among marine plankton, from stratigraphic sections on the Queen Charlotte Islands, British Columbia, Canada. This signal is similar to (though smaller than) the carbon isotope excursions associated with the Permian-Triassic and Cretaceous-Tertiary events.
During the Pleistocene epoch all of central British Columbia was covered by glacier ice that molded and sculptured a multitude of features from which the glacial events can be interpreted, The Fraser ice sheet was formed by the accumulation of snow and ice in the
Coast and the Cariboo Mountains whence it flowed into the Interior Plateau as coalescent ice sheets, The ice from the two sources met near Fraser River resulting in a southeasterly confluent mass and a northerly flowing sheet . The latter, together with ice from the northern interior, flowed north
easterly to the Rocky Mountains which blocked further advance, Deglaciation was a combination of frontal retreat, down wasting, and stagnation of large masses of ice. Later re-advance from the Coast. Mountains and Cariboo Mountains produced tongues and lobes of ice that extended into the Interior
Plateau but did not coalesce as an ice sheet. Earlier glacial advances are believed to have been more extensive. At some time in early Pleistocene time , ice accumulated to form a thick central dome from which ice flowed radially over and through the Coast, Cariboo and Rocky
Mountains.
The end-Triassic marks one of the five biggest mass extinctions, but current geologic time scales are inadequate for understanding its dynamics. A tuff layer in marine sedimentary rocks encompassing the Triassic-Jurassic transition yielded a U-Pb zircon age of 199.6 ± 0.3 Ma. The dated level is immediately below a prominent change in radiolarian faunas and the last occurrence of conodonts. Additional recently obtained U-Pb ages integrated with ammonoid biochronology confirm that the Triassic Period ended ca. 200 Ma, several million years later than suggested by previous time scales. Published dating of continental sections suggests that the extinction peak of terrestrial plants and vertebrates occurred before 200.6 Ma. The end-Triassic biotic crisis on land therefore appears to have preceded that in the sea by at least several hundred thousand years.
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