Early Cretaceous evolution of the McMurray Formation: A review toward a better understanding of the paleo-depositional system

Abstract

The Lower Cretaceous McMurray Formation of the Western Canada Sedimentary Basin has been the subject of numerous studies, with emphasis on its stratigraphic framework and sedimentological models. However, due to the stratigraphic complexity of the paleo-depositional system, which comprises fluvial and marginal-marine strata, it remains a challenging area of research. There is ongoing debate surrounding the depositional model of the most volumetrically significant and economically relevant units in the formation, with some suggesting that channel-belt deposits are predominantly fluvial in origin, while others argue that they are estuarine in origin, with some tidal influence. To gain insight into these issues, we present a comprehensive review of the McMurray Formation paleo-depositional system, focusing on three key aspects. First, we provide a detailed analysis of facies characteristics, including regional mapping results and trace fossil analysis. Second, we summarize the chronology of stratigraphic and depositional models developed for the McMurray Formation over the last 100 years. Third, we discuss the McMurray conundrum and present supporting information for the two widely accepted depositional models for the McMurray Formation channel-belt deposits. Proposed analogues and some of the associated critiques are discussed for each depositional model, and some future research directions are recommended. The complex nature of the McMurray Formation and the ongoing debates surrounding its depositional models emphasize the need for continued research and a multidisciplinary approach to better understand the McMurray paleo-depositional system.