Sizergh Castle Kettle Hole, Cumbria - Stratigraphic Survey Report

Oxford Archaeology North (OA North) was commissioned in July 2013 by Levens Local History Group and the National Trust to deliver a programme of community archaeological work at Sizergh Castle (SD 500 875). The project provided supervision and training for participants in a broad range of archaeological skills, which included archaeological excavation, topographical survey, geophysical survey, building survey and palaeoenvironmental work; the project was funded by the Heritage Lottery Fund (HLF). The work was undertaken in accordance with a project brief by the National Trust and a project design by OA North. The results of the two areas excavated, the deer park boundary and a burnt mound, and those of the topographical survey, geophysical survey and barn survey, were presented within a report in February 2014 and a popular publication in March 2014. A stratigraphic survey of a kettle hole associated with the burnt mound proved of potential considerable interest, but analysis was not within the remit of the HLF project. An application was therefore made to the Cumberland and Westmorland Antiquarian and Archaeological Society for a grant to undertake the palaeoenvironmental analysis of the Sizergh kettle hole, including obtaining radiocarbon dates. This work has been undertaken during the summer and autumn of 2014.
A hand-auger survey carried out within an area of boggy ground adjacent to the burnt mound at Sizergh revealed a small basin infilled with deposits typical of a kettle hole. These deposits included a succession of blue/grey silts and clays, overlain by shell marl (‘gytta’), over which woody and humified peat deposits accumulated. A kettle hole is a small steep-sided depression in glacial boulder clays, formed as ice retreated following deglaciation. Kettle holes often became filled with water, forming small lakes or ponds, and were subsequently filled by peat deposits, leading to the development of small basin mires. The Sizergh kettle hole contains a typical Late glacial and early Holocene sequence of shell marls, clays and peat, which contains a pollen record that may date back to the Loch Lomond stadial (c 10,000-11,000 cal BC). An amelioration in climate during the early Holocene led to the eventual development of vegetation and mixed woodland. Successional changes in the lake basin culminated in the development of mire vegetation, and peat development from around 8200 cal BC.