We appreciate the Comment by Mazumder (2008) on our recent paper (Yang et al., 2008), and hope that he will be a part of continuing discussion and study on the subject. Mazumder's main point is that the ratio between wave components and tidal currents plays an important role in the formation of rhythmic succession in nearshore settings: classic tidal bundle (tide-dominated; e.g., Nio and Yang, 1991; Dalrymple, 1992) and wave-generated tidal bundle (wave-dominated; Yang et al., 2008). On this basis, he disagrees with the term “wave-generated,” and recommends the alternative term “wave-dominated” to recognize that tide and wave processes interact in the generation of our rhythmic deposits. We acknowledge this point and feel it is addressed in our paper. However, careful consideration of Mazumder's comments suggests that our difference of opinion is small (wave-generated versus wave-dominated). Nevertheless, we maintain that the term wave-generated is better employed to describe these previously undefined rhythmic successions.
Although coastal environments and associated deposits are extremely diverse, sedimentological models promote the notion that coastal deposits can be identified as wave- or tide-dominated based upon their sedimentary character (e.g., Boyd et al., 1992). In fact, wave- and tide-dominated settings are distinctive in terms of physical processes and geomorphology, which cause these two settings to contain distinctive sedimentary deposits. Bioturbated strata (Gingras et al., 1999) through to heterolithic stratification (e.g., Reineck and Wünderlich, 1968; Dalrymple, 1992)—including tidally generated bedding—is currently regarded as being characteristic of tide-dominated tidal flats, whereas wave- and storm-generated deposits including hummocky cross-stratification (HCS) are indicative of wave-dominated shorefaces and shelves (e.g., Walker and Plint, 1992; Cheel and Leckie, 1993). Surveys of modern coasts have, however, revealed that mixed-energy conditions commonly occur in marginal-marine locales (e.g., Yang et al., 2005). As a result, the generally accepted facies models do not account for truly mixed-energy coastal zones (namely, open-coast tidal flats) (e.g., Fig. 1). In other words, open-coast tidal flats may be greatly underestimated in the geologic literature (e.g., Yang et al., 2005).
Recently, Yang et al. (2005, 2006) have emphasized open-coast tidal flats, where both tides and waves play an important role in nearshore sedimentation. They have further suggested that open-coast tidal flats occupy a medial position in the process-sedimentological spectrum, and thereby differ greatly from the two end-member settings (Fig. 1). However, these deposits strongly resemble shoreface successions because of the abundance of HCS and storm-event beds (Yang et al., 2005), and because of the tendency for upward (shoreward) coarsening (Yang et al., 2006). On this basis, the identification of open-coast tidal flats denotes that the deposit is wave-dominated. In an early draft of our paper, we had, in fact, applied the term wave-dominated to describe our rhythmic deposits, but the iteration of terms led to confusion within the manuscript (i.e., wave-dominated tidal bundle in wave-dominated tidal flats). Instead, we have taken the term wave-generated to emphasize depositional processes for these previously undefined rhythmic successions, because the entire succession (composed of three differing wave-rippled layers), fundamentally, is wave-generated.
We would like to thank Duncan Mackay (Queen's University) for his helpful comments and draughting.