Bituminous Shale.

Bituminous shale is found near the head of the Waitati Stream behind Dunedin. The first distinct outcrop of the shale is in the bed of the stream about half a mile above the point where the Blueskin track crosses it. The shale here (b) is about six feet in thickness, and is underlaid by a thin bed of what appears to be a very good fire clay; below this is a clayey sandstone with peculiar white page 111markings about two feet thick, and below this comes a considerable thickness of the Caversham sandstone (c). The beds here dip 18° S.W. About 20 chains up the valley another outcrop of the shale is seen, forming a precipitous cliff on the side of the valley (b″). The shale in this place is about 18 feet in thickness, and is underlaid by the same beds as are below it lower down the valley, and is covered by basaltic rocks (a). I could not make out the dip with accuracy, but it seems to be slightly to the east. This portion of the strata appears to have been thrown up by a fault that crosses the valley in a N.W. and S.E. direction. (See Fig. 27.)

Fig. 27.—Bituminous shale, Waitati. a, basalt; b, b″, bituminous shale; c, Caversham sandstone.

The fact that the shale thickens from 6 to 18 feet in a distance of 20 chains, makes it appear likely that this great thickness may not be retained for any considerable distance, but the country is so thickly covered with bush that it will be difficult to trace the outcrop. But, however this may be, an abundant supply of material is evidently available, and it is most advantageously situated for extraction.

Professor Black informs me that this shale contains 42 gallons of crude oil per ton.

Another bituminous shale, equal in quality to that of Waitati, is found at Orepuki, and others have been reported from Mount Hamilton, Otapiri Creek, and Wyndham River. No doubt abundant supplies of these shales will be found in the Putataka formation.