Reports: G8
43888-G8 A Section-Based Approach to Quantifying the Geologic Record
Overview: The thin veneer of sedimentary and volcanic rocks that comprise the earth's stratigraphic record not only contain our entire fossil fuel resource reserve, but they also chronicle a 3.8 billion year history that is vital to understanding the history and evolution of tectonics, climate, and life on earth. Despite the centrality of the rock record to a wide range of sub-disciplines in the earth and life sciences, rather little is known about the large-scale temporal and spatial structure of the rock record. This research project aims to overcome this limitation by quantifying the spatial and temporal architecture of the rock record with an unprecedented level of temporal and spatial resolution. Methodology: Heterogeneity in the spatial and temporal distribution of rocks reflects the combined product of three primary phenomena: tectonics, climate change, and sea level change. All three of these factors interact with one another and leave quantitative signals in the rock record. However, the rock record does not merely passively record this history. Instead, the formation of the rock record itself exerts a strong influence on earth history by 1) serving as important sources and sinks for climate changing elements, such as carbon, 2) controlling changes in the physical characteristics of marine and terrestrial environments, and 3) imposing physical structural heterogeneity in the upper crust. The data-collection phase of this research project involved the compilation of gap-bound rock packages from a variety of literature and field sources for all of the United States and Canada. This task has been completed, with the active help and participation of undergraduate students, graduate students, and a postdoc for the entire known rock record at 821 geographic locations in North America, 132 deep sea sites in the world's ocean basins, and 329 sites in New Zealand. Survivorship-based rate parameters that summarize the temporal and spatial turnover of sedimentary environments have been derived from these data, quantifying for the first time the spatiotemporal dynamics of physical environmental change. These results have already been shown to have important implications for our understanding of evolution (see Peters, 2008, Nature). Career Impact: This PRF grant has provided invaluable flexibility in developing an entirely new branch of quantitative stratigraphy, which the PI has termed macrostratigraphy. This new analytical approach is being tested through the work described here and through collaboration with colleagues using analytical basin-fill models. Without the support of this ACS-PRF starter grant, it would be impossible to adequately explore the potential of macrostratigraphy as a viable analytical tool. Impact for Students: Understanding how the rock record is put together should be a critical component of every students' geological education. Students who have participated in this project have enjoyed hands-on experience in assimilating the rock records of particular regions. They now know what time intervals are represented and by what rock types. The students have responded positively to the task and have accomplished a great deal. Specifically, over the course of the last 24 months, my students and I have entered the age of first and last occurrence, rock type, thickness, and other information for 30,544 rock units. We have also developed and published an online resource for interacting with this database, now known as Macrostrat. Visit the P.I.'s homepage for a link for use in teaching and research.
