Eric R. Timmer

SPATIAL AND TEMPORAL SIGNIFICANCE OF PROCESS ICHNOLOGY DATA FROM SILTY-MUDSTONE BEDS OF INCLINED HETEROLITHIC STRATIFICATION, LOWER CRETACEOUS MCMURRAY FORMATION, NE ALBERTA, CANADA

Abstract: In this paper we examine quantitative ichnological data of silty-mudstone beds from inclined heterolithic stratification (IHS) in order to understand the spatial and temporal controls affecting bioturbation in IHS. Data collected for this study include bed-scale averaged bioturbation intensity, size-diversity index, and ichnogenera abundances. These data were used to assign each bed into one of 10 clusters using K-Means clustering. The clusters were ranked according to interpreted intensity of cumulative depositional ecologic stress. Time-series, where each silty-mudstone bed represents a time-step with a corresponding ecologic stress value, were constructed from the interpreted ecologic stress cluster analysis results. To identify and interpret spatial and temporal variation in the ichnological time-series, two time-series analysis methods were employed: dynamic time-warping and continuous wavelet transforms. Dynamic time-warping is used as a descriptor of the spatial similarity between ecologic stresses, and continuous wavelet transforms are used to interpret cyclical patterns in the ichnological time-series. Spatially, the variability and cyclicity observed in the ecologic stress time-series can be linked to estuary scale stresses and more localized stresses (i.e., bar-form scale depositional stress). This is reflected by the relatively similar periodicities observed in the ecologic stress time-series. Temporally, cyclical ecologic stress patterns occur somewhat predictably in periods of approximately four, or multiples of four, which are consistent with El Nino cyclicity.

PYCHNO: A CORE-IMAGE QUANTITATIVE ICHNOLOGY LOGGING SOFTWARE

Abstract: Collecting and analyzing semi-quantitative ichnological parameters such as size-diversity index and bioturbation intensity, can increase the resolution of paleoenvironmental analyses. Specialized software, PyCHNO, was designed to ease, improve, and standardize current ichnological data collection techniques. With PyCHNO, ichnological data derived from burrow diameter measurements, trace fossil identification (ichnogenus level), and bioturbation index are collected at a user-defined scale, and size-diversity index is calculated from these measurements. Data collected in PyCHNO, including size-diversity index, maximum burrow diameter, trace fossil diversity, trace fossil taxon abundance, and bioturbation index is easily exported as text files or plotted as PDF logs.