POST‐GLACIAL SEDIMENTS AS A RECORD OF REGIONAL SOIL DRIFTS

Abstract

SummaryAnalytical data are given for deep‐water sediments from Esthwaite Water in the English Lake District representing different depths below the mud surface and sediments of ages back to and including the late‐glacial, of which the pollen status is known. Nitrogen content and loss on ignition increase steadily in muds laid down during the time of post‐glacial forest development, showing also a small previous rise which represents the temporary late‐glacial climatic amelioration (Allerad). Nitrogen remains approximately constant in muds representing the stage of post‐glacial alder‐oak‐birch forest. Deforestation, as shown by increases in grass pollen in the muds, is associated with falls in the values for nitrogen and loss‐on‐ignition. These decreases occur in two stages, believed to represent two stages of human settlement and land use.Analyses for elements such as sodium, potassium, magnesium, calcium, and iron, show signs of increasing solubility in the muds representing the time of forest development. Thereafter the amount of calcium diminishes progressively in later muds, while the Ca/Fe ratio falls, changes which could be correlated with the leaching effects of a rainfall of 170‐zoo cm. per annum on the soils in the lake basin. Similar data are recorded for a core from Rydal Water.The results are interpreted as records of the regional changes in soils from the lake drainage systems during the post‐glacial period.