Wave Dominated

Summary

Wave dominated environments are part of the marine shore, with regular large waves and their associated currents. As waves move through the deeper ocean waters, the water moves in an orbital or oscillatory motion. As waves approach the shallow areas near the shore, that flow begins interacting with the seafloor, causing waves to peak and crest (Boggs, 2014).  When discussing wave formation, two primary types of wave base are covered. The fair-weather wave base at ~5-15m in depth, and the larger storm wave base at ~30-125m in depth (Yang et al., 2005). Wave dominated coasts are generally divided into 4  main subenvironments based on these wave energy regimes. Starting near the shore we have the beach, and moving out toward the ocean we have the shoreface, the offshore-transition, and offshore environments.  As in all environments, grain size is a function of energy levels and proximity to the source (Isla et al., 2018). In the offshore environments, calmer waters support the creation of fine-grained rocks like mudstone and siltstone.  During storm surge, thin beds of sand, called tempestites, are sometimes deposited here.  As we move closer to the shore and above the storm wave base, we begin to see higher energy features. In the offshore-transition, storm events bring high energy levels and long-wavelength storm waves, which create a distinct sedimentary structure called hummocky cross-stratification. Here we also see interbedded sand and mudstone. Moving forward into the shoreface environment, there is relatively continuous wave energy. This constant energy keeps finer-grained particles in suspension, so there's a loss of the mudstone interbedding. We also see a transition from hummocky cross-stratification to more swaley cross-stratification in storm-influenced shoreface zones (Macnaughton et al., 2019). If the shoreface is not storm-dominated, fair-weather waves will create symmetrical wave ripples. If one wave direction is higher strength than the other, ripples will form cross-lamination. Finally on within the beach environment, we see planar lamination of fine-grained sands with parting lineations. Sediments on beaches are deposited at a low angle (<5°), seaward dipping plane (Vakarelov et al., 2012).