Deciphering the Beat of a Timeless Rhythm - The Future of Astrochronology
Stephen Meyers University of Wisconsin EAR-1151438
The geologic record provides the only available documentation of long-term environmental change, but in order to accurately interpret this record and evaluate rates of change we require a means to tell time. The dating of sedimentary deposits via astrochronology has become one of the most important tools for construction of the state-of-the-art geologic time scale. This method utilizes the geologic record of climate oscillations - those ascribed to quasi-periodic changes in the Earth's orbit and rotation - to measure the passage of time directly from repetitive sedimentary layers. The impact of astrochronology on the quantification of 'deep-time' has been truly revolutionary, and the approach is now even employed to fine-tune (e.g., calibrate) radioisotopic data and to test their veracity. However, although the method has resulted in the development of extraordinary high-resolution time scales, the uncertainties in deep-time astrochronologies are almost uniformly poorly constrained. This CAREER project will address the three fundamental challenges to the field of deep-time astrochronology using a new computational approach, with the goal of enhancing the accuracy and precision of an astronomically tuned geologic time scale.
The first of the challenges to deep-time astrochronology arises from the near ubiquitous lack of adequate independent time control (e.g., radioisotopic data with sufficiently small errors) to unambiguously calibrate observed spatial rhythms to temporal periods, which prohibits direct confirmation of the proposed astronomical tempo. This shortcoming has resulted in much confusion, including multiple incompatible interpretations for a given stratigraphic record, and has also roused suspicion about the veracity of astrochronology. The second major challenge is the corruption of the orbital insolation signal as it propagates through the climate system and into various depositional systems (including sedimentation rate changes and hiatus), which may ultimately render the preserved astronomical signature unidentifiable, or worse yet, result in erroneous inferences about the preserved tempo. The third major challenge to deep-time astrochronology is the lack of accurate orbital insolation solutions beyond ~50 Ma, which necessitates the distinction between 'floating' and 'anchored' astrochronologies. These three challenges will be addressed by uniting and building upon important scientific advances within the fields of Quaternary paleoclimate, cyclostratigraphy, geochronology and geophysics. The new computational approach will provide fundamental methodological advances towards the achievement of an astronomically tuned Phanerozoic time scale, and will yield a more complete understanding of how orbital insolation changes influenced the surficial Earth System during both icehouse and greenhouse intervals of Earth history. As a test case for the new methodology, this project will evaluate the Eocene Green River Formation, a stratigraphic unit of great historical significance to the field of cyclostratigraphy.
A central feature of this CAREER project is the integration of research and education. Involvement in the UW-Madison PEOPLE program engages youth in scientific discovery, and increases underrepresented minority participation in Geoscience. Partnership with colleagues at the UW-Madison Geology Museum will culminate in the development of a new geologic time display that will be seen by ~45,000 visitors per year, and participation in their science outreach program will result in a new model railroad exhibit (the 'Deep-Time Express') to be deployed at large public events. Establishment of a national research hub for the intercalibration of astrochronologic and radioisotopic time scales will build community within the field of geochronology, and will facilitate the distribution of software and tutorials generated for the project. Finally, the development of courses in chronostratigraphy and cyclostratigraphy, coupled with student participation in research, will provide a unique interdisciplinary training for the integration of astrochronologic and radioisotopic time scales, thus cultivating future leaders in the field of geochronology.
