AbstractsEarth & Environmental Science

Petrographic methods as generally understood comprise the methods by which material collected in the field is investigated in the laboratory. Although for strictly petrological purposes it may be sufficient simply to effect the qualitative and quantitative examination of sediments, geologically speaking the investigation is incomplete without carrying the inquiry still further, viz. to a consideration of the source or sources of origin of the sediments and its bearing on the palaeogeography of the area at the time of deposition. Commenting on the value and nature of such investigation Milner (1940 p. 490) says “The perusal of this more philosophical aspect of the science is not merely academic; indeed, one might almost say that without such inquiry all petrographic work must lose both in precision and value: it will certainly lack vitality. “Tracing the source of constituent particles of a deposit is often by no means a straightforward matter, especially where the locale of a distributive province capable of furnishing the material is obscure or where, owing to widespread erosion, no direct evidence of such a province exists. The problems to be faced are, from their very nature, some of the most complex and absorbing that a geologist has to solve and each case must perforce be dealt with on its own merits.”