Science has achieved tremendous success over the centuries, partly because the complexities of the Earth, the physical processes that sustain the planet, and the enormity of life were separated into disparate fields of study—mathematics, physics, chemistry, biology, and geology, to name only a few. Scientific compartmentalization was initially necessary to impart enough focus to make progress on complicated issues. However, as the knowledge base grew, it became more and more difficult to separate life and the history of the Earth, and vice versa. We now understand that to investigate the Earth's surface as an abiologic system is folly: Life and Earth processes are intimately linked. Hence, a new field was born at the interface between biology and geology: geobiology. As a field, geobiology seeks to understand the intersection of life and the rock record across Earth's history: how organisms influence the physical Earth and vice versa, and how the marriage of physical and biological processes have transformed our planet over its long history. The assessment of life's macromolecules of DNA, RNA, polysaccharides, proteins, and lipids, and their potential recalcitrance in an ecosystem, has opened up the field of geobiology to lead us toward a solid explanation of where life came from, how life has altered the planet, what may be possible for life elsewhere, and what represents one of the reasons for the explosion of geobiologic studies today. Here we outline how molecular biology has transformed our understanding of geobiology, describing a few of the essentials needed to understand geobiology and exploring an example of a modern geobiologically relevant system: a living stromatolite from the shore of a geothermal hot spring in Yellowstone National Park, Wyoming, USA.

Abstract Copious δ 13 C data have been collected from Neoproterozoic successions around the world for the purpose of chemostratigraphic correlation, but few successions provide radiometric dates with which to calibrate the δ 13 C profiles. The Neoproterozoic succession near Pocatello, Idaho, is not particularly rich in carbonates, but it does contain important radiometric constraints not available in other sections. Four carbonate intervals are found in the succession. A thin, pink dolostone unit, located above the diamictites of the Scout Mountain Member, Pocatello Formation, records negative δ 13 C values and is younger than 709 Ma and older than 667 Ma. A thicker limestone unit found at the top of the Scout Mountain Member records negative δ 13 C values and is slightly younger than 667 Ma. The Blackrock Canyon Limestone is located above the Pocatello Formation but stratigraphically below units dated at ~ 580 Ma and contains five siliciclastic to carbonate meter-scale cycles containing oncolites and thrombolites. We interpret these as shallowing-upward parasequences. They progressively record a transition from mildly negative to mildly positive δ 13 C values. Finally, a thin dolostone layer located within the Caddy Canyon Quartzite records highly positive δ 13 C values (> 8‰) and is constrained to be older than ~ 580 Ma. The siliciclastic nature of the succession precludes continuous δ 13 C profiles. However, our data would suggest that the transition from negative to highly positive δ 13 C values occurred after 667 Ma, a conclusion that differs from other less well constrained δ 13 C compilations that would place the transition closer to ~ 700 Ma. In addition, the δ 13 C profile is similar to that from postglacial units in Death Valley to the south, and can tentatively be used to provide age constraints to this poorly dated succession.

Abstract This one-day field trip examines two Neoproterozoic sections in the Portneuf Narrows area, SE of Pocatello, Idaho. Rocks to be examined on the first traverse belong to the Scout Mountain Member, Pocatello Formation, and include <710 Ma glacial diamictites, dolomite cap, 667 Ma tuff, and upper caplike carbonate. The second traverse, in Blackrock Canyon, exposes the cyclic Blackrock Canyon Limestone, with upward-shallowing siliciclastic to carbonate cycles and microbial mounds.