l"'.\K(^i.'iiAi{SON.— 7V;f' Pldtiiiiiiu Graveh nf Orejmki. 4B7 



In this we sec that, resting on the eroded surfaces of the bed-rock, there 

 is first a layer of sandstone and silt about 5 ft. thick, followed by a stratum 

 of lignite of about the same thickness ; after this comes another stratum 

 of sandstone, then a layer of Ugnite, and so on. Three distinct scams of 

 lignite separated by beds of sandstone are to be seen. Above all is the 

 •clay, or in places the artificial tailings. The geology, therefore, of the claim 

 is very simple. The sandstone on the bottom is usually fine, interspersed 

 here and there with small pebbles. Sometimes fairly large pebbles of gabbro 

 are found. 



The lignite above is poorer in some places than in others, but generally 

 speaking its value does not amount to much. That this lignite has drifted 

 into its present position is shown unmistakably by the following : (a.) It 

 is usually muddy, the woody tissue being interspersed with pockets of fine 

 silt, or sometimes very similar in appearance to a brownish-black clay. 

 (6.) Rounded pebbles of varying size, and consisting of gabbro, are found 

 in it, more often than not in the bottom of the layer, (c.) Prone tree trunks 

 and branches, consisting of miro, pine, and rimu, have been seen in it. 

 {il.) An instance has been noticed where a tree-trunk has a vertical posi- 

 tion in it, and the lignite has its layers bent up and around the trunk. 

 Whether the trunk actually grew as it has been found is not known, but the 

 probability is that it was simply sticking out of an underlayer, and a fresh 

 deposit w^as formed round it. (e.) The bands are not continuous, but occur 

 in some places and not in others, and often dovetail into the silt and sand. 

 This would tend to show the existence of current bedding. The sandstone 

 above the bottom layer of lignite is much the same as that below it, but 

 does not contain, as far as can be seen, any pebbles. The thickness of 

 the sandstone layers varies between 5 ft. and 20 ft. The beds are of only 

 local extent, occurring only in the hollow between the two sides of sloping 

 ground. The lignite (to a very small extent) and the sandstone are auri- 

 •ferous, a fact which can be shown in the case of the sandstone by a simple 

 prospect with a shovel. No fossi's of any kind have been seen. 



What, then, is the origin of these formations ? To answer this ques- 

 tion, let us first suppose we have a coastal area like the Round Hill district 

 undergoing submergence, while, of course, the land further in remains more 

 or less stationary.* The first effect of this is to increase the corrosive 

 action of the streams. Since, however, the land is mostly bush-covered, 

 the corrosion ^vill not be very great, but the amount of vegetation brought 

 -down will be proportionately increased. Again, as submergence goes on, 

 the sea will invade the river-valleys, forming ultimately a bay or estuary, 

 and it may extend even to some distance up the sides of the mountain-range. 

 The water of the streams, charged with detritus and vegetation, on meet- 

 ing the comparatively calm water of the bay will be unable longer to retain 

 the material in suspension, and it will be precipitated. The result is that 

 at first a bar wall be formed, but later on the bar will be flattened out. The 

 strata in the bar will be composed partly of silt and partly of woody material, 

 according as the stream has brought more debris than vegetation, or vice 

 versa. There will, therefore, be a tendency towards the formation of a 

 flat plain, as the sea-action wall round off all irregularities, and the slope 

 will increase gradually inland. A succession of periods of flood will thus 

 cause the formation of bands of silt, or vegetable matter mixed with silt, 



* if depression all round took place, the corrosive action would, of course, be di- 

 minished. 



