Holocene environmental and pedogenic history of the Hiraethog Moors, Clwyd
This project describes the Holocene environmental and pedogenic history of the Hiraethog Moors, particularly in relation to archaeological evidence. Ironpan stagnopodzol, brown podzolic and stagnohumic gley profiles have been studied from Aled Isaf together with cores from Cefn Mawr and Llyn y Foel-frech. Physical, chemical, clay mineralogical, micromorphological and palynological analyses have been undertaken and a time framework has been achieved by radiocarbon dating, including AMS 14C dating of ironpan and charcoal samples. A search for tephra has been undertaken and, although none was located, the presence of a biolith bloom in a core from Llyn Cororion on the Arfon Platform raises the possibility of a geochemical reconstitution of a low volume, fine-grained tephra fall. Parent material was reworked by periglacial processes during the Late-glacial resulting in an oriented fabric, cracked stones and a redistribution of clay and fine siltsized material. Until 6-7,000 years BP soils remained shallow and stony, with a clay mineralogy dominated by hydrous mica and chlorite. Between 6,000 and 4,000 years BP erosion led to deeper soil profiles on the lower slopes, burying flints and charcoal, and the woodland was periodically disturbed by humans. However, man was relatively inactive between 4,500 and 3,500 years BP. At 3,500 years BP woodland cover declined rapidly due to human activity with a subsequent change to a Gramineae- and then a Calluna-dominated vegetation community. In low lying sites the result was increased waterlogging, gleying, structural collapse and the build up of organic matter at the surface i. e. stagnohumic gley. In better drained sites podzolisation occurred to produce the Bs horizon, i.e. brown podzolic soil. In profiles most intensively leached, mor humus and then peat accumulated. This induced surface waterlogging resulting in a mobilisation of iron, structural collapse and the formation of an Eag horizon, within which chlorite was destroyed and hydrous mica weathered to vermiculite, and an ironpan i.e. ironpan stagnopodzol. Through the integration of soil and pollen analysis, 14C dating and archaeological information our understanding of soil development and human activity on Hiraethog has been increased.