Sequence Stratigraphy

Sequence stratigraphy is a methodology that employs stratal stacking patterns and key bounding surfaces to erect a framework allowing depositional facies to mapped and interpreted paleogeographically. Historically, sequence stratigraphy has been focused on allogenically induced changes such as eustasy, tectonics, and climate. Like sedimentology, ichnology assists in the identification and interpretation of bounding surfaces separating stratal units. These are recognized through the use of trace-fossil omission suites and the juxtaposition of ichnological suites recording shifts in depositional settings that contravene Walther's Law. Two siliciclastic case studies from the Lower Cretaceous Viking Formation of Canada and one carbonate case study from the Middle Permian–Lower Triassic Khuff Formation, offshore Iran, are employed to showcase the utility of ichnology in sequence-stratigraphic evaluations. Case study 1 deals with incised shorefaces and the identification of forced regressive, lowstand, and transgressively incised shallow-marine sand bodies. Case study 2 addresses wave-dominated estuarine valleys that are incised into highstand marine parasequences and incrementally infilled during early transgression. Case study 3 focuses on sequences from a carbonate platform built of transgressive systems tracts and highstand systems tracts separated from one another by maximum accommodation zones and capped by maximum regressive surfaces that are locally transgressively modified.