One of the best places to study Late Triassic terrestrial ecosystems is the Chinle Formation in Petrified Forest National Park (PEFO), Arizona. Here, sedimentary rocks ~220-210 million years old preserve a rich record of paleoenvironmental and biotic change. These strata are renowned for their preservation of fossil wood, leaves, and vertebrate animals, including early dinosaurs. They also created a record of the climate change, from more humid conditions recorded in older strata to arid conditions recorded in younger rocks. These Late Triassic environmental changes preserved in rocks at PEFO, and their relationship to observed changes in the species of fossil plants and animals found there, are a key to understanding how Late Triassic climate shaped the evolution of ecosystems on land. NAU student Ryan Gahris spent a day with PEFO paleontologist Bill Parker who explains how recent studies of Late Triassic geology and paleontology at PEFO document a sudden change in plant and vertebrate species in the middle of the Sonsela Member of the Chinle Formation, the major petrified wood bearing layer in the park. This change is the largest biotic turnover event recorded in the rock record at PEFO, and is associated with a distinctive red silcrete layer and may have been related to the impact of a large asteroid or comet in what is now Quebec, Canada. This is a 2011 SCPN-NAU School of Communication collaboration student project.

• published: 29 Aug 2013
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