The biotic and sedimentologic evolution of the Cambrian

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The `Cambrian Explosion' half a billion years ago was a turning point for life on Earth: the evolutionary appearance of animals in the sea, which gave rise to fossils of shells, spicules, skeletons, even sometimes soft tissues, plus new kinds of microbes and algae. This new and complex biota caused profound ecological revolution in the marine realm. Sediment changed fundamentally due to processes of burrowing, digestion, excretion, organic binding and bacterial decay. The first metazoan reefs appeared. My group will continue to investigate these phenomena in an interdisciplinary way, by combining sedimentological and paleontological approaches in order to explore more fully this exciting yet still mysterious episode of Earth History. The natural laboratory for us will be the spectacular southern Rocky Mountains. The indoor laboratory includes a wide range of analytical techniques from optical microscopy to elemental mapping using synchrotron X-ray fluorescence. The origin and evolution of ancient sediments and organo-sedimentary processes in various tropical carbonate reef, sand shoal, tidal flat, shelf and lagoonal environments will be studied from the preceding latest Precambrian through early Paleozoic time via sedimentary features, paleoecological attributes and geochemical data. In a short span of time-just some 50 million years-these successive carbonate platforms show dramatic contrasts yet also remarkable similarities. We will reconsider long-held facies interpretations and assumptions, and develop criteria to differentiate tsunami- versus storm-generated beds, and earthquake cracking from desiccation. The stratigraphic occurrence of fossils will permit high-resolution temporal correlation of lithological units and will help reveal patterns of diversification, extinction, phylogeny and times of regional and global change captured in these rocks. This wide-ranging and interdisciplinary dataset will allow us to interpret Cambrian paleoclimate, paleoceanography, sea level and sedimentation, as well as elucidate the tectonic history of the vast continental shelves and inland seas in which these rocks accumulated.