Integrated cyclostratigraphy and biogeochemistry of the Cenomanian/Turonian boundary interval, Western Interior Basin, North America

Geochemical, paleobiologic and sedimentologic records of Milankovitch orbital forcing provide a valuable tool for deconvolution of the climate-sedimentation linkage and construction of high-resolution time scales in ancient stratigraphic records. However, accurate characterization of the cyclicity preserved in rhythmic strata is commonly challenged by distortion of the orbital insolation signal during its propagation through the climate and depositional systems. The complete pathway of the Milankovitch signal from orbital-insolation changes to the final proxy data series employed for time-series analysis is characterized by transfer functions for the climate system, depositional system, diagenesis, sampling protocol, and analytical error associated with proxy measurement. The first major objective of this dissertation is to critically evaluate the sources of distortion, noise and error present in cyclostratigraphic analysis, and to demonstrate that some characteristic types of noise may be employed to reconstruct a detailed sedimentation history (e.g., sedimentation rate change, quantification of hiatus). Such high-resolution timescales may then be employed to calculate geochemical proxy flux estimates, resolving the ambiguity of relative proxy concentration data for paleoclimate analysis. These objectives are achieved by (1) development of a method for assessment of the climate-sedimentation linkage, which employs Evolutive Harmonic Analysis in tandem with stratigraphic modeling, (2) development of a misfit parameter for accurate characterization of the preserved orbital cyclicity. Application of these techniques to Cenomanian/Turonian records from the Western Interior Basin and the proto-North Atlantic permit the development of a globally consistent chronology for Oceanic Anoxic Event II (OAE II).; The second major objective of this work is to integrate geochemical proxy flux estimates, paleobiologic data, and sedimentologic data with biogeochemical models of organic matter (OM) degradation. This integrated cyclostratigraphic and biogeochemical methodology is employed to investigate the controls on OM burial and molybdenum accumulation during OAE II. The analysis indicates that OM and molybdenum burial fluxes are primarily controlled by the balance between metabolic demands within pore waters, production rates of H₂ S, and rates of H₂S depletion via pyrite formation. These results provide a new model for the development of transgressive source rocks in the geologic record that dominantly reflects a confluence of biogeochemical processes within sediments.