ISOTOPIC COMPOSITIONS OF INDIVIDUAL CARBOHYDRATES AS INDICATORS OF EARLY DIAGENESIS OF ORGANIC-MATTER IN PEAT

Data are reported on the chemical variations in amino acids and carbohydrates and isotopic compositions of the individual carbohydrates which have been isolated from living matter, Sphagnum, and from the underlying peat. These results are supported by a C-13 NMR assessment of the same samples. Carbohydrates isolated from plants and animals have carbon isotopic compositions which are recognized to be associated with isotopic fractionations during the incorporation and metabolism of carbon. The isotopic label can be used to trace sources of carbohydrates in materials undergoing diagenesis. Production of non-indigenous carbohydrates, which may be associated with bacterial action, can be identified through more depleted isotopic compositions in the carbohydrates from a "soft" hydrolysis. Xylose, glucose and galactose, for example, isolated from the fresh plant, became more depleted C-13 during peat formation, possibly indicating a microbial source. Mannose, rhamnose and arabinose, isolated from the same peat samples, remained fairly constant in their isotopic compositions, reflective of the indigenous plant input. The cellulose portion of the samples also remained isotopically constant during diagenesis, whereas a more refractory isolate, the residue following exhaustive chemical degradation, became depleted in C-13 with depth in the peats, indicating a post-depositional formation.