Precambrian-Cambrian boundary global stratotype ratified and a new perspective of Cambrian time: comment and reply

Article Abstract:

E. Landing's hypothesis about the relationship between the Siberian Lower Cambrian sections with Newfoundland ignores the usefulness of small shelly fossils in studying Lower Cambrian rocks. Also, there should be a gap between the Manykay and Tommotian stages because animals were shown to be present from the Nemakit-Daldyniant to Tommotian stages. Landing, however, states that these arguments merely boasts of a continuous Manykian-Tommotian transition accompanied by pretribolite animal evolution. He points out that there is evidence that the Cambrian basin shifted at the base of the Manykiaian and Tommotian stages.

Paleontology, Newfoundland and Labrador, Newfoundland

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Comment and reply

Article Abstract:

A study of C isotope trends in Siberia's sub-Tommotian unconformity is criticized for lack of biostratigraphic or geochronologic control and comparative analyses. In short, the study is tagged as unenlightening to Early Cambrian history. It is argued that such study is not new and is in fact reported in an earlier study. A possible correlation between the initial observation of taxa in the stratotypic basal Tommotian rocks and the unconformity is also accepted. However, the theory must be compared with a biostratigraphic pattern widely used among Russian paleontologists.

Siberia

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Chuar Group of the Grand Canyon: record of breakup of Rodinia, associated change in the global carbon cycle, and ecosystem expansion by 740 Ma

Article Abstract:

The Chuar Group, approximately 5,250 feet thick, offers a readily-dated, accurate record of tectonic, environmental, and biological changes that began the Phanerozoic Eon. This group was deposited during the extension of the north-tending Butte fault system and contains many cyanobacteria, algae, and heterotrophic protists.

Colorado, Research, Grand Canyon, Radioisotopes

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