Kerrie L. Bann1, Christopher R. Fielding2, Stuart C. Tye3, James A. MacEachern4, and Brian G. Jones5
1Ichnofacies Analysis Inc., Calgary, AB, Canada
2Geosciences, University Of Nebraska, Lincoln, NE
3Sedimentology, Husky Energy, Calgary, AB, Canada
4Earth Sciences, Simon Fraser University, Burnaby, BC, Canada
5Earth and Environmental Sciences, University of Wollongong, Wollongong, NSW, Australia
Prograding shallow marine successions traditionally have been interpreted either as deposits of shoreface/strandlines or deltaic systems. Whilst the sedimentological characteristics of strongly river-dominated deltaic deposits are relatively conspicuous, wave-dominated deltas commonly yield only subtle physical indicators of deltaic influence; as such, they are easily overlooked or challenging to recognize in core. Detailed examination of both the sedimentological and ichnological characteristics of outcrop analogues such as those of the Early Permian of the Sydney Basin and the Denison Trough, eastern Australia, significantly enhance the understanding of wave- and/or storm-dominated reservoir successions and highlight recurring facies characteristics that can be employed for their differentiation. Indeed, within the context of a wave-dominated deltaic succession, it is possible to recognize a continuum from archetypal strandplain shorefaces to classical wave-dominated deltas. Within this construct, predictions can be made regarding a locality’s relative proximity to fluvial discharge.
Ichnological analysis is essential to this discrimination. The interplay of fluvial influx, river discharge types, tidal energy, wave energy and storm influence affects infaunal diversities, their abundances, feeding strategies and overall behaviors. Additionally, deltaic signatures in successions with a strong storm overprint are exceedingly subtle in core and can be easily overlooked. Integrated studies of well-exposed outcrop analogues facilitate the recognition of the architecture of large-scale sedimentary structures and the detailed recognition of sporadically distributed trace fossil suites, leading to the reliable identification of subtle but significant indicators of deltaic processes and their associated physico-chemical environmental stresses.
AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas