2 Study area and geological setting
The exact boundaries of the civitas Cananefatium are unknown but this paper focuses on known approximate boundaries. The northern boundary is formed by the current Old Rhine, which flows into the North Sea in present day Katwijk (fig. 2). In Roman times this river was however significantly wider. In the south the estuary of the Meuse, Waal and Scheldt form the boundary of the study area. In Roman times this river mouth was known as Helinio. The area between the two estuaries consisted of peat bogs, which in the west were separated from the sea by a series of parallel beach ridges. On top of these sandy barriers small dunes formed over the centuries, making this an ideal landscape for habitation from prehistoric times onwards. The area east of these barriers was less suited for habitation.
From the Late Iron Age onwards, the sea entered the inland bog area through the large river mouths as a result of storm surges, resulting in the erosion of large sections of peat by tidal channels (Van der Valk 2006, 24-25). Clays were deposited simultaneously over the surrounding and partially eroded moors. The most influential of these tidal channels is the so-called Oer-Gantel, which entered the area from the Meuse estuary. While clay sediments covered the peat, they also silted up the tidal channels in the course of time, decreasing the catchment area. The clay area became suited for habitation from early Roman times onwards as most of the tidal channels became inactive by this process.
During Roman times, the landscape slowly sank as a result of a rising sea level, making the area less suited for habitation. From the beginning of the second millennium AD, the sea again enters the inland area through the Meuse estuary, depositing new clay sediments on top of the Roman habitation traces. At the same time the coastline also drastically changes. As a result of coastal erosion sands get picked up by the wind, transporting the sediments further inland, covering the former ‘Older Dunes’ and resulting in the present day ‘Younger Dunes’ on top of them. As a result, much of the archaeology in this area has been preserved, but is also difficult to find and excavate.