We appreciate the comments by G. Shanmugam on the paper “ 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), 104,030] ”. Most of the comments from G. Shanmugam refer to the sedimentary facies scale, with special emphasis on the distinct types of deposits and their definitions. It was quite a surprise that G. Shanmugam's comments did not include any remarks about the descriptions or discussions elaborated in Rodrigues et al. (2022a), such as the large-scale morphological features recognized in mixed (turbidite-contourite) depositional systems through bathymetric or seismic data or the newly proposed classification scheme. Rodrigues et al. (2022a) has a very brief sub-section on the sedimentary facies recognized in mixed systems (e.g., Section 5.4 Sedimentary facies and deposits of mixed systems , page 22), which is based on a few key contributions from past literature (such as Mutti and Carminatti, 2012; Fonnesu et al., 2020; Rodrigues et al., 2022b). His comments appear to be a compilation of his own assertions and do not provide a clear link to the contribution of Rodrigues et al. (2022a) or to the study of mixed depositional systems. Initially, G. Shanmugam focuses his comments on the multitude of turbidite and bottom current processes that occur in contourite and turbidite settings, as well as their definitions and models. He states that Rodrigues et al. (2022a) proposed a new classification for mixed depositional systems “ based on their notion that there is only one type of turbidite and that there is only one type of contourite in deep-marine systems” , but the authors have never made such a statement in their manuscript. He also reports that Rodrigues et al. (2022a) “ failed to provide a clear and precise definition of the terms turbidite, contourite, and bottom current” , but nevertheless the authors have provided definitions and references for those terms. Accordingly, G. Shanmugam outlined four distinct problems in Rodrigues et al. (2022a) review paper, namely (1) the turbidite problem, (2) the contourite problem, (3) the bottom-current problem, and (4) the seismic geometry vs. sedimentology problem. As indicated above, G. Shanmugam's criticism is focused on turbidite and bottom current processes in non-mixed settings, while very few points are made about these processes in mixed depositional systems. As clearly stated in the Introduction of Rodrigues et al. (2022a), the aim of this review paper was to “ compile all currently known cases” , “ present new undocumented examples” and “ compare their lateral migration, stratigraphic stacking patterns and seismic facies” . In addition, “ a new classification system is proposed, along with clear diagnostic criteria, to address some of the previous inconsistencies and to characterize the spatial and temporal variability of mixed systems” . Therefore, we believe G. Shanmugam has misinterpreted the aims of this review paper and raised issues unrelated to or not covered in this study. He uses this comment to highlight points that are controversial in literature or that follow opinions different from his own publications, in order to open a discussion that is not fully relevant to the identification or recognition of mixed systems. In fact, the problems raised in Shanmugam's comments have been a recurrent point of debate for several years now. Deep-water processes, their definitions and models have been profusely discussed by him and other authors since the 50s (Kuenen and Migliorini, 1950; Bouma, 1962; Middleton and Hampton, 1973; Lowe, 1982; Cullis et al., 2018). We do agree that there is a high degree of variability in deep-water turbidite and bottom current processes, both in contourite and turbidite settings, as well as in mixed depositional settings. However, the paper by Rodrigues et al. (2022a) focuses solely on reviewing the interactions between turbidite and bottom currents in mixed depositional systems to improve their recognition and classification and, therefore, does not approach these processes separately in other depositional environments (e.g., in pure contourite or turbidite settings). The authors will therefore not partake in the debate surrounding the definitions and models of these processes in non-mixed depositional environments. However, the authors will reply to the points raised about these processes in mixed depositional systems, specifically points 1–4 in problem 1, points 1–2 in problem 2 , points 7–9 in problem 3 and point 12 in problem 4 .
Read full abstract