|Geology according to the current published maps|
(after Brunker et al 1972)- scale approximate
Rock weathers to form soils but there is rarely a distinct boundary between soil and rock, a transition occurs. This transition zone is called the regolith which lies below the soil proper at the surface, it is the transition into saprolite (weathered rock) and then to unweathered rock. If the weathered rock was derived from shales, mudstones and other fine grained sediments then often these layers will become clay. It was this clay that was looked for.
|A better interpretation following the testpit investigation|
From my understanding of the area around Dunoon and on the basis of what was found during the hole digging exercise I put together a rough new map of the area (the second map above). As you can see there is actually a fair amount of difference. So, don't take it for granted that when you look at a geological map it is exactly right. It should be used as a guide and your knowledge should be applied to check it. The amount of coal we found was so abundant that a discussion about this is probably worth another post in the future.
Brunker R.L., Cameron R.G., Tweedale G. and Reiser R., 1972, Tweed Heads 1:250 000 Geological Sheet SH/56-03, 1st edition, Geological Survey of New South Wales, Sydney