At least theoretically, the freshwater reservoir effect (FRE) has been known for a longer time than the marine reservoir effect.
The most common cause of high apparent ages in freshwater systems is the presence of dissolved ancient carbonates, leading to the so-called hardwater effect.
Mesolithic pottery, maybe the earliest in that region, was found at the sites Kayhude at the Alster and Schlamersdorf at the Trave. Today, after the construction of a dam, Kilen is a brackish embayment.
Material for AMS Both modern shells, collected from the Northern German rivers, and shells from the sediment core in the Limfjord were pretreated with the following method: Shells were cleaned with ultrasound in demineralised water.Water rich in dissolved ancient calcium carbonates, commonly known as hard water, is the most common reason for the freshwater reservoir effect. Although it has been known for more than 60 years, it is still less well-recognized by archaeologists than the marine reservoir effect.The aim of this study is to examine the order of magnitude and degree of variability of the freshwater reservoir effect over short and long timescales.Of particular interest and complexity are the so-called reservoir effects, which result in apparent ages that are too old. This is of particular concern to archaeologists, as aquatic resources were an important contribution to human nutrition in Northern Europe, from Mesolithic hunter-gatherer-fishers to medieval Christians.
One of the basic assumptions in radiocarbon dating is that a sample incorporates carbon in equilibrium with the atmosphere. The marine reservoir effect is well-acknowledged among archaeologists, although the knee-jerk subtraction of 400 years from radiocarbon dates of marine samples might be too simplistic in some cases.
This will provide an overview of use to archaeologists who consider dating materials which may be affected by a FRE. Here, the short-term variability of the freshwater reservoir effect in the rivers Alster and Trave is measured.