GENES THAT MAKE ROCKS

The combination of geobiology and paleogenomic studies is a powerful approach which leads to a more fundamental understanding of how Earth and life have changed through time in building the sedimentary rock record. For example, paleogenomic investigations of biomineralization genes for echinoderms, molluscs and coralline sponges have been very informative. Linking paleogenomic studies of biomineralization genes for modern organisms and when they first evolved in the Cambrian with geobiological studies of the impact this had on the production of carbonate sedimentary facies and the development of the Neritan ocean provides a unique perspective on how genes have shaped formation of the sedimentary record. Another component of the Cambrian explosion, the evolution of vertical bioturbation at the start of the Cambrian, has had significant effects on biogeochemical cycling and sediment production, and provides an inviting target for future genomic studies. The remaining Phanerozoic includes a broad variety of evolutionary innovations which within a joint geobiological and paleogenomic context can also be profitably studied. Identification of the genes which lead to scleractinian corals turning formation of the mineralized skeleton on and off during periods of changing ocean chemistry will have great utility for understanding reef development. In pelagic settings determination of the genomic changes that led to evolution of the skeletons of coccolithophores is of great importance as they have strongly contributed to the widespread deposition of carbonate sediment in deep settings and development in the Mesozoic of the Cretan ocean. Likewise, paleogenomic study on the evolution of diatom silica biomineralization genes in the Mesozoic will allow greater understanding on the proliferation of siliceous sedimentation in the Cenozoic. On land, linking paleogenomic studies of the genes that led to the Paleozoic evolution of lignin and their associated geobioogical effects, such as deposition of coal, provide another example of the effects of genes upon development of the sedimentary record. Such work will ultimately provide a history of genomic change and the environmental factors that influenced it, as well as how genomic changes shaped the development of the sedimentary rock record.