Some chemical observations on post-glacial lake sediments

摘要: This paper reports the results of a somewhat exploratory investigation chemical composition cores taken from sediments number lakes English Lake District. All studied are glacial, and therefore presumably synchronous, origin. The depth post-glacial sediment varies lake to but is normally between 4 6 m. material, with which mainly concerned, was laid down during biologically active phase following end glaciation approximately 10 000 years ago. Below organic muds period, consists glacial clays, usually varved, pass downward into silty clays sands total at present unknown. variation in time presents pattern change observed recur most studied. strikingly seen carbon content depth, related sequences may be distribution major inorganic components, for example sodium, potassium magnesium. changes can easily explained if regarded as sequence soils derived drainage areas lakes. residues eventually reaching bed then accounted terms rate erosion basin rather than changing rates productivity either on or waters. does not appear greatly influenced by events within themselves except case elements migrate more readily under reducing conditions arise muds. Examples these iron manganese, used deduce redox past times, hypolimnetic waters themselves. Biological activity also influence significantly distinctly biophile elements, phosphorus sulphur examples. Even phosphorus, however, it seems likely that co-precipitation reactions have deposition efficiency incorporation biological tissues. cause apparently synchronous intensity recorded various remains doubt. Some evidence halogen boron presented suggest least synchronism climatic variations erosional activity. Since halogens perhaps largely oceanic air-streams, expected 'oceanicity' climate sediment. A direct relationship deduced meaning this rendered ambiguous however consideration possible soil ionic balance attributable progressive loss leaching soil-derived anions passage time. Although gross dependent system waters, some deductions made indicate availability nutrients dissolved times. If material rapidly removed erosion, nutrient lost locked lattice unleached mineral particles. erosive removal land surface reduced, particles held column position allows efficient soluble become available living populations lake.