talk
Energy in Canada's North

Applying Chemostratigraphic Data to Establish a Sequence Stratigraphic Framework: An Example from the Devonian Canol Formation

Thursday, November 22, 2018 - 09:00 to 09:19 Theatre 2

Author(s)

M.T. LaGrange (Presenting)
University of Alberta

B. Harris
University of Alberta

K.M. Fiess
NWT Geological Survery

V. Terlaky
NWT Geological Survey

M.K. Gingras
University of Alberta

Sequence stratigraphy is a useful method for understanding lateral and vertical heterogeneity in sedimentary successions. Predicting this variability is essential to understanding organic-rich mudstone resource plays, which have become increasingly important in recent years. However, making sequence stratigraphic interpretations in mudstone successions is challenging, because sedimentological variations are typically subtle, wireline logs can be ambiguous, and seismic or biostratigraphic datasets are commonly of limited use. As a result, researchers have started incorporating chemostratigraphic datasets to establish sequence stratigraphic frameworks in these intervals. The chemostratigraphic proxies most commonly used are elements that reflect abundance of continental input including Al, Fe, K, Ti, and Zr, and proxies that can be used to infer the proportion of biogenic silica relative to detrital silica such as Si/Al, Si/Zr and Si-Al cross plots. Paleoredox proxies (e.g. Mo, Ni, Th/U, V) that give information about basin isolation and water column stratification can also be useful. However, the use of elemental proxies can be limited by the possibility of element migration during diagenesis or from surface weathering. Furthermore, chemostratigraphic datasets are most suited to the interpretation of trends which typically limits sequence stratigraphic inferences to longer term transgressive-regressive cycles unless supported by sedimentological data.

This presentation reviews existing work on the use of chemostratigraphy to establish a sequence stratigraphic framework, and provides local context by using data from the resource-rich Middle to Late Devonian Canol Formation as a case study. High-resolution elemental data have been collected from the Canol Formation in the Mackenzie Mountains and the Central Mackenzie Valley, Northwest Territories, using a portable x-ray fluorescence analyzer. Preliminary results suggest that it is possible to identify transgressive-regressive sequences and important sequence stratigraphic surfaces from these elemental proxies. Upon completion, this project will serve as a guide to the usefulness of geochemical proxies for sequence stratigraphy, which will facilitate the development of sequence stratigraphic frameworks to map variations in shale reservoir quality.