An estuary is a partially enclosed coastal body of water that communicates with the open sea, but is protected from the action of open ocean waves by its topography or some form of barrier that absorbs and refracts wave energy (e. g., sand bars or barrier islands). Usually the term is applied to inlets into which rivers or streams flow, causing fresh and marine waters to intermingle (Fig. 5.5). These transitional zones between river and ocean environments experience both marine processes (tides, waves, saline water influx) and fluvial processes (freshwater influx, sedimentation), contributing diverse nutrients that make estuaries among the world's most productive natural habitats.
5.4 View of tombolo, Paximadi Cape, Euboea. Courtesy of Tim Bekaert.
5.5 View of an estuary in South Carolina, USA. Courtesy of the National Oceanic and Atmospheric Administration.
Estuaries trap fine-grained sediments, leading to the formation of a variety of landforms such as tidal mudflats, tidal marshes and swamps, and tidal inlets. In the Aegean, where tidal currents are weak, mud and clay are deposited on shallow mudflats in the lower intertidal zone. In the upper (landward) intertidal zone, continued deposition of mud can cause vertical accretion and eventually the formation of a brackish marsh above the normal high tide level. These different landforms exhibit characteristic sedimentary structures and contents (Wells 2001: 158—59, 162). Mudflat sediments typically consist of a mix of silt and clay with a high iron content and in situ molluscan fauna. Tidal marshes are rich in peat, comprising very fine-grained clay and silt with a high organic content. In tectonically stable contexts, marshes build up and out, gradually infilling the estuarial basin.
Estuaries and their associated landforms are highly significant to the study of ancient coastlines. Because of their micro - and macrofossil content, as well as datable organic material, they provide key evidence for coastal evolution. Equally important is the fact that estuaries were a far more prominent feature of coastal landscapes in the Bronze Age than they are today, offering quiet environments ideal for anchorage; these would have been desirable harbor locations throughout the Mediterranean (Raban 1991). Great estuaries at major river mouths are obvious targets for Bronze Age harbors, but because of the tendency of estuaries to fill in over time, smaller estuarial harbors might only be revealed by systematic geomorphological prospection.
Maritime Networks in the Mycenaean World Barrier Islands and Lagoons
Lagoons are tidal inlets of shallow marine or brackish water that are separated from the sea by a barrier. Mediterranean lagoons are typically sheltered by barrier islands, which are elongated offshore sand ridges extending parallel to the shoreline and separated from it by the lagoon (Summerfield 1991: 330). Barrier islands range from a few meters in width and a few hundred meters in length to long islands a few kilometers in width and hundreds of kilometers in length. Lagoon waters are replenished by tidal inlets that perforate the barrier at irregular and migrating intervals. In response to changes in sediment supply, relative sea level, and climate, barriers may form, retreat landward, or disappear.
Lagoons fill with coarser sediment predominantly supplied by longshore drift. Because lagoons are shallow, they are susceptible to infilling and are strongly influenced by precipitation and evaporation. When evaporation rates are high, salinity in a lagoon can exceed that of the sea, and stranded lagoons can form salt pans or salt lakes. The Akrotiri Salt Lake on the southern tip of Cyprus was probably part of a lagoonal system in the Bronze Age that was later isolated from the sea (Blue 1997: 35—38). Salt deposits were surely exploited in the Bronze Age for subsistence and trade.
The western coast of the Peloponnese is a prominent example of lagoon and barrier formation. On the coast of Elis, coastal landform change has been dominated for the last 8,000 years by longshore redistribution of sediments from the Alpheios and Peneus rivers into an extensive Holocene barrier accretion and lagoonal system (Kraft et al. 2005: 4; Fig. 5.6). In these settings, both sedimentation from fluvial inputs and erosion and littoral transport from high wave energy have shaped Elean and Messenian shorelines into long, sandy beach strands (hence, Homer's “sandy Pylos"). Hans-Jeorg Streif (1964, cited in Kraft et al. 2005: 5) identifies three major alluvial terraces in the Alpheios River system and correlates them with three episodes of coastal barrier accretion at the delta. These are roughly dated to EBA, LBA, and Classical to modern (in several subphases).
World History
