High-Frequency Paleoclimate Variation: Analysis, Interpretation, and Significance

Algeo, Thomas¹ (1) University of Cincinnati, Cincinnati, OH

High-frequency paleoclimate records can contribute to refinement of the geologic timescale, improved understanding of paleoenvironmental dynamics, data-model comparisons in paleoclimate research, and source-rock characterization. Paleoclimate variation at timescales of 10³-10⁵ years is observed at sub-meter length scales in many ancient sedimentary successions, but capturing and interpreting such information can be challenging. The most efficient approach to extracting both the time content and environmental/climate information recorded in such successions is to generate high-resolution datasets (1) over the full stratigraphic interval of interest for one or a few key proxies, and (2) over several short stratigraphic intervals for as many proxies as time and resources allow. The first dataset provides the basis for time series analysis, by which the rate and duration of sedimentation can be constrained. Proxies commonly used for this purpose include CaCO₃, TOC, magnetic susceptibility, and petrophysical and core logs. The second dataset is used to identify relationships that comment upon environmental processes. Interpretation of process from multiproxy datasets is facilitated when data are collected at a high level of stratigraphic resolution; low-resolution datasets are difficult to interpret due to the simultaneous operation of multiple environmental influences at longer timescales. Owing to loss of high-frequency paleoclimate information through time averaging associated with bioturbation in oxygenated marine environments, the approach discussed here works best in anoxic marine facies, such as Devono-Carboniferous deepwater black shales, or in facies in which bioturbation has been artificially suppressed, such as post-extinction Permo-Triassic shallow-marine carbonates.