Introduction
We were invited by the environment agency to examine sediments exposed during the digging of a well, to take samples and make a geoarchaeological assessment of what was found.
Background
We knew the bedrock of the area was Triassic Mudstone, overlain by Holocene marine and estuarine alluvium known as the Wentlooge Formation, and we found the soils to be deep, stoneless and calcareous and of a type commonly found on estuarine alluviumand typically used for pasture. The area has a high water table which is controlled by pumping through ditches and sea defences.
During the construction of the well we able to gain access to examine the sides of the excavation and take samples.
Findings
When we examined our samples we found a sequence of natural estuarine deposits, some of which showed stages of soil development and various post-depositional changes. When we allowed the samples to dry further, finer details could be seen, including fine, regular, silty laminations and clay filled root channels and fissures. In a deeper sample we found a peaty clay with evidence of changing sea levels.
Conclusions
From our investigations, we were able to tell the client that the deposits we examined were estuarine alluvial sediments, and contained evidence of brief periods of time in the past when it was drier, although not dry enough for terrestrial surfaces to become established. Also that the deposits may well contain evidence that could help shed further light on past environments in the area.