Orbital Forcing - Cenozoic and Mesozoic

Our understanding of the role orbital forcing plays in Plio-Pleistocene climate change focuses on the role of ice.

Changes in ice volume provide most of the signal in d¹⁸O curves, provide one clear positive feedback loop (ice-albedo feedback), and explain repetitive stratigraphic packages of onlap and offlap. However, for much of the Cenozoic and Mesozoic, ice was confined to either the Antarctic region, or not present in any large amounts anywhere on the globe.  What happened in the absence of ice feedbacks? The evidence strongly suggests that Milankovitch cycles can be found in the sedimentary record at all times.  Much of my work involves generating and analyzing sedimentary time series of Cenozoic and Mesozoic age to establish this point.

Stratigraphic applications of the orbital model include improving the Geomagnetic Polarity Timescale by tuning magnetozones and/or biozones with the orbital chronometer, and developing quantitative models of cyclic sedimentary fluxes that match geological observations.  Much of our research effort requires that we develop techniques to rapidly acquire time series data, and statistical approaches to interpreting time series.  Successful examples include the use of optical densitometry on color slides, of visible reflectance on core surfaces, and a new application of infrared spectroscopy to core surfaces (with Prof. John Mustard and former graduate student Christopher Cooper, PhD '04).

More broadly, we seek to understand how orbital forcing influences the land, ocean, and atmosphere in times of minimal ice volume.  We do so by studying biotic, sedimentological,  and geochemical variations at the scale of ancient orbital cycles, and by developing our understanding of which climate mechanisms could be responsible for producing cyclic sedimentation.

Brown faculty collaborators:

Other project collaborators: