Carbohydrates from Precambrian and Cambrian Rocks and Fossils
Carbohydrate residues in eleven samples of early to late Precambrian rocks and fossils and one sample of Middle Cambrian Burgess Shale ranged from traces to more than 5 μg/g Free monosaccharides and a disaccharide, acid-extractable (polymeric) sugars, and recognizable polysaccharides were found in the samples. Geological conditions in the sampling areas suggest that the free sugars, being water-soluble, may not be indigenous to the rock but perhaps were introduced by ground-water circulation during the present or a preceding erosion cycle. Available evidence suggests that the acid-extractable monosaccharides and polysaccharides are at least partly native to the rocks or fossils in which they occur.

The acid-extractable sugars obtained in these samples are β-D-galactose, β-D-glucose, mannose, arabinose, xylose, ribose, and rhamnose; the first two were identified enzymatically and they and the other sugars were also identified chromatographically. The polysaccharides found in these samples are linear α —1 →4 glucopyranose units suggesting starch, β — 1 → 4 glucopyranose units suggesting cellulose, and β — 1 → 3 glucopyranose unitssug-gesting laminaran. No starch residues were found n i the two lower Precambrian samples (Soudan and Coutchiching), but a trace of celluloseand laminaran was obtained in the Coutchiching. This may be an indication that cellulose-type structural polysac-charides and laminaran-type reserve sugars, but not starch-type food-reserve polysaccharides, existed in the early Precambrian.