The Cambrian witnessed the rapid development of almost all modern groups of animals, including the rise of skeletal faunas, a major evolutionary event known as the Cambrian explosion. Trilobites were among the most important elements of the so-called Cambrian Evolutionary Fauna. Until now, it has been considered that trilobites have been essentially restricted to fully marine subtidal settings. New research by an international team led by scientists from the University of Saskatchewan, Canada, is now challenging this view. Their study is based on the discovery of trace fossils produced by trilobites in alternating sands and silts formed under intertidal conditions in a Cambrian tidal flat preserved in what is now the Appalachians. The biogenic structures are present in layers that show clear evidence of subaerial exposure. This study provides convincing evidence that trilobites were able to foray into the upper intertidal zone during the rising tides. Intertidal ecosystems may have provided food resources and acted as refuges for trilobites and other migrant arthropods. This study adds a new step in our understanding of the ecologic implications of Cambrian explosion and the early colonization of the land.
Decoupled Hf-Nd isotopes in Neoarchean seawater reveal weathering of emerged continents
Sebastian Viehmann et al., Steinmann Institut, Rheinische Friedrich-Wilhelms-Universitt Bonn, 53115 Bonn, Germany; Current address: Earth and Space Science Program, Jacobs University Bremen, 28759 Bremen, Germany, email@example.com. Posted online ahead of print on 13 Dec. 2013; http://dx.doi.org/10.1130/G35014.1.
When in Earth's history did vast landmasses first emerge above sea level? This fundamental geological question is still subject to controversy. Numerical simulations, for example, suggested
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Geological Society of America