Earth History Research
Above: Cretaceous-Paleogene boundary exposed in the Denver Basin, USA. Finger is placed on a Chicxulub impact ejecta layer containing minerals with evidence of shock metamorphism.
The history of life in our planet has been influenced by dramatic events that deeply transformed ocean and atmospheric chemistry. Relatively short-lived events such as mass extinctions, bolide impacts and large igneous provinces are known from the geologic/stratigraphic record, but their exact timing is in many cases only poorly known, thus difficulting interpretations of causality and obscuring potential underlying mechanisms. Taking advantage of our expertise in radiogenic isotope geochemistry, our lab has actively participated in addressing some of these important questions. Some examples of previous and ongoing efforts on this are highlighted below.
Highlights
Constraining the age of inner core nucleation
Convection of the outer liquid core of our planet, which is fueled by crystallization and growth of the solid inner core, is responsible for driving Earth’s geomagnetic field and protecting life from harmful solar radiation. Nevertheless, the age of nucleation of the solid inner core remains poorly constrained. Along with collaborators John Tarduno and Rory Cottrell (Paleomagnetism group, U. Rochester), we are developing a high-resolution paleointensity record of the late Proterozoic through early Paleozoic time period, in an effort to better constrain the onset of inner core nucleation.
This project is supported by NSF-EAR grant 1828817 (to Tarduno, Cottrell and Ibanez-Mejia). Stay tuned for future publications from this research.
Chronostratigraphy of the San Jorge Basin
In collaboration with Will Clyde (U. New Hampshire), Peter Wilf (Penn State), Marcelo Krause (MEF, Arg.) and Mark Schmitz (Boise State U.), we have completed two studies aiming to establish a high-precision time calibration for the Paleocene-Eocene stratigraphic successions of the San Jorge Basin in Patagonia. The units in this basin preserve some of South America’s most significant Paleogene records of biotic and climatic change, and include various important zones for SALMA (South American Land Mammal Ages) whose precise timing was previously unknown. Importantly, the basal Cenozoic unit of the San Jorge basin, the Salamanca Fm., preserves an outstanding paleontological and paleobotanical record of the recovery of intermediate-latitude austral biotas to the Chicxulub impact and the aftermath of the Cretaceous-Paleogene (K-Pg) mass extinction.
See papers by Clyde et al. (2016) and Krause et al. (2017) for more information.
Petrochronology of Deccan Traps magmatism
In collaboration with Asish Basu (UT Arlington) and Blair Schoene (Princeton U) we are working on better understanding the timing, sources and origin of felsic/alkalic complexes associated with Deccan Trap basaltic magmatism. Along with the K-Pg-boundary Chicxulub bolide impact, basaltic volcanism of the Deccan Traps large igneous province is another suspect that may have played a role in the end-Cretaceous mass extinction. Understanding the age and chemical/isotopic composition of felsic shallow intrusives that are spatially and temporally associated with the Deccan will be crucial for: a) establishing a potential source for the zircon found in ‘redbole’ horizons between Deccan basaltic flows (dated by Schoene et al., 2015, 2019), and b) establish the importance of Proterozoic crustal melting during the emplacement of the Deccan plume.
The first results of this study are in revision in the journal Geology.
