Chuar Group of the Grand Canyon: Record of breakup of Rodinia, associated change in the global carbon cycle, and ecosystem expansion by 740 Ma
Karlstrom KE, Bowring SA, Dehler CM, Knoll AH, Porter SM, Des Marais DJ, Weil AB, Sharp ZD, Geissman JW, Elrick MB, Timmons J, Crossey LJ, Davidek KL. 2000. Chuar Group of the Grand Canyon: Record of breakup of Rodinia, associated change in the global carbon cycle, and ecosystem expansion by 740 Ma. Geology. 28(7):619-622
The Chuar Group (-1600 rn thick) preserves a record of extensional tectonism, ocean-chemistry fluctuations, and biological diversification during the late Neoproterozoic Era. An ash layer from the top of the section has a U-Pb zircon age of 742 ± 6Ma. The Chuar Group was deposited at low latitudes during extension on the north-trending Butte fault system and is inferred to record rifting during the breakup of Rodinia. Shallow-marine deposition is documented by tide- and wave-generated sedimentary structures, facies associations, and fossils. C isotopes in organic carbon show large stratigraphic variations, apparently recording incipient stages of the marked C isotopic fluctuations that characterize later Neoproterozoic time. Upper Chuar rocks preserve a rich biota that includes not only cyanobacteria and algae, but also heterotrophic protists that docrnnent increased food web complexity in Neoproterozoic ecosystems. The Chuar Group thus provides a well-dated, high-resolution record of early events in the sequence of linked tectonic, biogeochemical, environmental, and biological changes that collectively ushered in the Phanerozoic Eon.
- Type
- Journal Article
- Authors
- Karlstrom, Karl; Bowring, Samuel; Dehler, Carol; Knoll, Andrew; Porter, Susannah; Des Marais, David; Weil, Arlo; Sharp, Zachary; Geissman, John; Elrick, Maya; Timmons, J Michael; Crossey, Laura; Davidek, Kathleen
- Units
- GRCA
- Keywords
- Chuar Group, Deposition (Geologic), Geochronology, Geology, Structural Geology, Tectonics