Sedimentology of tidal meanders has received comparably much less attention than that of river meanders, and facies models for tidal point bars were developed in the shade of their fluvial counterparts, driven by the simplistic assumption that tidal and fluvial meanders are characterized by similar planform morphologies and dynamics, together with accretional and erosional processes along the inner and outer bank, respectively. This general lack of attention for tidal meanders runs parallel with their scarce documentation in the ancient record, a knowledge gap that contrasts with their widespread incidence in modern coastal plains, where they play a fundamental control on landscape evolution. Knowledge about tidal meanders and their deposits is even weaker when considering those developed in coastal regions characterized by a microtidal regime (e.g Mediterranean Basin, Gulf of Mexico and the Baltic Sea). The Venice Lagoon (Northeastern coast of Italy) includes a wide spectrum of meandering channels developed in a microtidal regime, and provides a unique laboratory to investigate their morphodynamic evolution and the related sedimentary products. The Venice Lagoon has a total surface of about 550 km2 and represents the largest brackish water body of the Mediterranean Basin. The Lagoon has an elongated shape trending NE-SW and has mean water depth of tidal flat and subtidal platform of about 1.5 m. It is connected to the sea through three inlets, where the maximum water excursion is ±0.75 m around Mean Sea Level. Nowadays, the Lagoon does not receive any relevant fluvial sediment supply, and is surrounded by densely-vegetated saltmarshes. Tidal channels are up to 15 m deep and form a complex network that drains saltmarshes, tidal flats and adjacent subtidal platforms. This talk will provide an overview on morphological and sedimentological processes concurring to shape these channels and build up related pointbar bodies. Specifically, it will illustrate planform geometries and migration rates of channel bends developed at different scales, and will depict depositional geometries developed under the interaction between lateral migration and vertical aggradation. The signature of tidal processes will be shown and compared with that recorded in deposits accumulated where tidal range is higher. Finally, stratal architecture and sedimentary facies distribution in subtidal pointbars will be also described.
