The Triassic/Jurassic boundary in continental rocks of eastern North America; A progress report
P. E. Olsen, S. J. Fowell, B. Cornet, 1990. "The Triassic/Jurassic boundary in continental rocks of eastern North America; A progress report", Global Catastrophes in Earth History; An Interdisciplinary Conference on Impacts, Volcanism, and Mass Mortality, Virgil L. Sharpton, Peter D. Ward
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Newark Supergroup rocks of eastern North America provide a fine-scale record of continental faunal and floral change spanning all of the Late Triassic and most of the Early Jurassic (Carnian/Pliensbachian). Lake-level cycles controlled by orbitally induced climate changes permit calibration of biotic change at a 20,000-year level of resolution. The patterns of both the faunal and floral changes suggest that the Triassic/Jurassic biotic changes consisted of a large number of extinctions without replacement: the succeeding assemblages consist of survivors. The Triassic/Jurassic Newark faunal and floral transition appears synchronous with the massive marine extinctions noted elsewhere in the world. Preliminary data suggest the Newark pollen and spore transition took place in less than 20,000 years (within one lake-level cycle), whereas available bone and footprint data suggest the extinction of ecologically dominant Late Triassic terrestrial vertebrates could have taken as long as 700,000 years. Although we are still in the early stages of investigation, what we know about the Newark Triassic/Jurassic episode is consistent with a very large and abrupt mass extinction event. The penecon-temporaneous Manicouagan impact still seems a plausible cause. A search has only now begun for evidence of an impact-derived fallout layer in the Newark Supergroup, but it is far too early to confirm or deny a causal role for a bolide impact for the Triassic/Jurassic extinctions, in the Newark Supergroup or elsewhere.