Comment on “A new classification system for mixed (turbidite-contourite) depositional systems: Examples, conceptual models and diagnostic criteria for modern and ancient records” by S. Rodrigues, F.J. Hernández-Molina, M. Fonnesu, E. Miramontes, M. Rebesco, D. C. Campbell [Earth-Science Reviews (2022), https://doi.org/10.1016/j.earscirev.2022.104030

Abstract

Rodrigues et al. (2022) have proposed a new classification for mixed turbidite-contourite depositional systems based on their notion that there is only one type of tubidite and that there is only one type of contourite in deep-marine systems. However, there are at least 36 turbidite types and 4 contourite types in the published literature. Furthermore, they have used the term “bottom current” to represent a single unique current, which flows along-slope. Nevertheless, there are 4 major types of bottom currents (thermohaline contour currents, tidal currents, baroclinic currents, and wind-driven currents). With the exception of contour currents, the other three currents do not and cannot flow along-slope. The problem here is that the authors have failed to provide a clear and precise definition of the terms “turbidite”, “contourite”, and “bottom current” Consequently, their classification has added a new layer of confusion to an already muddled domain of turbidite-contourite research. Importantly, their review article suffers from failing to cite pioneering and seminal works on turbidites (e.g., Kuenen, 1957; Bouma, 1962; Bagnold, 1962,; Middleton, 1967; Sanders, 1965; among others) and on contourites (e.g., Hollister, 1967). In seeking clarity, the purpose of this discussion is to identify specific issues with 14 questions under the following topics: (1) the turbidite problem, (2) the contourite problem, (3) the bottom-current problem, and (4) the seismic geometry vs. process sedimentology problem. Hopefully, the authors would respond with necessary definitions, empirical data, and references.