Morphodynamic evolution of meandering channels in tidal landscapes: sedimentology and stratal architecture

Meandering channels constitute one of the fundamental components of tidal systems, as related tidal point bars are ubiquitous features in lagoonal or estuarine sedimentary successions. Nevertheless, a limited number of studies analyzed their morphodynamic evolution, together with their planimetric shape and morphometric characteristics. Their internal architecture and sedimentary facies distribution are relatively unexplored, and commonly investigated using facies models developed for fluvial meander bends. Focusing on differences, more than on similarities, between tidal and fluvial meanders, the present work aims at investigating the stratal architecture and sedimentary facies distribution of selected tidal point bars in the Venice Lagoon (Adriatic Sea, Italy). Three main issue were investigate by the present work: i) the role of low order tributaries in controlling the evolution of tidal meander bend; ii) the influence of salt marsh aggradation in shaping geometries of tidal point bars, iii) sedimentary process and morphodynamics changes acting on subtidal point bars. The morphodynamic evolution of tidal channels, and related sedimentary products, were analyzed using a multidisciplinary approach, which comprises the comparison of historical photos, the interpretation of high-resolution sub-bottom profiles, core logging analysis and 3D modelling. The main results stemmed out form the study sites highlight that: I) lateral tributaries can strongly influence the evolution of bends modifying local mechanisms of sediment and flow distribution; II); the migration of tidal point bars occurs under aggradational conditions both in intertidal and subtidal setting; III) subtidal bars evolve under the strong interaction between wave and tidal currents