Abstract

Important topics in Early Cambrian geology are the paleogeography of the Earth's cratons, the chronology of their separation, and evaluating the effects of tectonic events on evolutionary patterns during the Cambrian radiation. The results of an analysis of Early Cambrian biogeography are presented here to provide an independent, biological constraint on geologic and geophysical models of the breakup of some of the major elements of the supercontinent Rodinia. Biogeographic analysis is also utilized to help elucidate the relative influences of continental breakup and sea-level change on evolutionary and distributional patterns during the Cambrian radiation. This analysis suggests that rifting and continental fragmentation were the dominant processes affecting biotic evolution and distribution in the Early Cambrian; repeated episodes of sea-level rise and fall played a more limited role. Moreover, the analysis indicates that Laurentia is a well-supported biogeographic region that shares a more recent history with Siberia than with Baltica, implying that rifting between Baltica and Laurentia occurred prior to rifting between Siberia and Laurentia.

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