Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published January 2003 | public
Journal Article

A methane fuse for the Cambrian explosion: carbon cycles and true polar wander


The dramatic diversification of animal groups known as the Cambrian Explosion (evolution's 'Big Bang') remains an unsolved puzzle in Earth Science. The Vendian–Cambrian interval is characterized by anomalously high rates of apparent plate motion, interpreted as True Polar Wander (TPW), and by more than a dozen large, high-frequency perturbations in carbon isotopes that dwarf all others observed through the past 65 million years. We suggest that these biological, tectonic, and geochemical events are intimately related in the following fashion. First, tropical continental margins and shelf-slopes which formed during fragmentation of the supercontinent Rodinia accumulated massive quantities of isotopically-light organic carbon during Late Neoproterozoic time, as indicated by strikingly heavy isotope ratios in inorganic carbon during interglacial intervals. Second, an initial phase of Vendian TPW moved these organic-rich deposits to high latitude, where conditions favored trapping biogenic methane in layers of gas hydrate and perhaps permafrost. Continued sedimentation during Late Vendian time added additional hydrate/gas storage volume and stabilized underlying units until the geothermal gradient moved them out of the clathrate stability field, building up deep reservoirs of highly pressurized methane. Finally, a burst of TPW brought these deposits back to the Tropics, where they gradually warmed and were subjected to regional-scale thermohaline eddy variation and related sedimentation regime changes. Responding to the stochastic character of such changes, each reservoir reached a critical failure point independently at times throughout the Cambrian. By analogy with the Late Paleocene Thermal Maximum event, these methane deposits yield transient, greenhouse-induced pulses of global warming when they erupt. Temperature correlates powerfully with biodiversity; the biochemical kinetics of metabolism at higher temperature decrease generation time and maintain relatively rich and dense invertebrate populations. Repeated thermal pulses along with progressive disruption and alteration of global ocean circulation patterns by TPW could cause the increase in diversity that accompanied the radiation of metazoans. We suggest that a methane 'fuse' ignited the Cambrian Evolutionary Explosion.

Additional Information

© 2003 Académie des sciences/Éditions scientifiques et médicales Elsevier SAS. Received 6 July 2002; accepted 21 October 2002. The authors acknowledge Paul Hoffman and an anonymous reviewer; Eiichi Tajika, Ryuji Tata, Keiko Matsuoka, and Tatsuo Oji; Rob Ripperdan, Jess Adkins, David Evans, Adam Maloof, Bob Berner, Mark Pagani, Jim Kasting, Ellis Yochelson, and Osvaldo Ulloa gave helpful and probing comments. This work was supported by the NASA Astrobiology Institute, by NSF-EAR 98-14608 to JLK and by an NSF Graduate Fellowship to TDR.

Additional details

August 22, 2023
October 20, 2023