Integrated Ichnological-Sedimentological Facies Models for Mixed-Influence Delta Deposits

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The 5-year project explores the complexities of trace fossil suites that are preserved in the ancient deposits of deltas. The study of trace fossils is referred to as "Ichnology". The deltaic deposits selected for analysis range from outcrop to subsurface core datasets, and show either a mixture of river and wave influences, or a mixture of river and tide influences preserved in the structures of the sedimentary rocks. It is hypothesized that these intermediate delta types (as opposed to river-, wave-, or tide-dominated end member expressions) possess unique trace fossil characteristics. The study will focus on trace fossil diversity, burrowing intensity, interpreted animal behaviours (ethology), burrow distribution, and size ranges of the biogenic structures. These biogenic characteristics will be integrated with physical and chemical processes of sedimentation, as reflected in the sedimentary rocks. Genetic stratigraphic frameworks (e.g., sequence stratigraphy) will be developed for the successions in order to assess delta lobe architectures and differentiate delta lobe switching from changes imposed by relative sea level. The case studies chosen for this project will be compared to previously assessed successions that reflect end-member states as well as mixed influence conditions. The integration of physical sedimentary features with the trace fossil characteristics will enhance our ability to identify similar deposits elsewhere, and will provide a continuum of delta types to facilitate development of more broadly applicable depositional models. Case studies also will explore the concept of delta asymmetry, a situation common to mixed river-wave influenced deltas wherein preferential river discharge occurs on the downdrift side of the delta lobe. Asymmetric deltas yield unique, spatially discrete successions and have, historically, been difficult to identify in the rock record. Differentiation of such deltaic successions from persistently brackish-water (salinity stressed) settings is challenging. The case studies evaluated in this project will attempt to erect criteria that enhances our ability to recognize these complex asymmetric successions.