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The Pamphlet Collection of Sir Robert Stout: Volume 71

VI.—Lower Greensand Group

VI.—Lower Greensand Group.

Where fully developed, as at the Amuri Bluff, this group [unclear: of] strata comprises: 1. Black grit; a very hard stratum of [unclear: gravel] stone, the pebbles being of minute size. 2. Dark marly clays [unclear: and] sands, 3. Sulphur-sands, being fairly laminated sands of [unclear: bright] colours, often hardly consolidated, but containing large [unclear: concretion] of glance sandstone. 4. Greensands of intensely dark colour, [unclear: being] composed of glauconite, or iron silicate, and containing irregular [unclear: cm] cretions of ironstone that formed round masses of fossil wood, [unclear: on] portions of the skeletons of huge Saurian reptiles. In some parts [unclear: of]. New Zealand this greensand is underlaid or replaced by sharp [unclear: gric] sands that form the cover of valuable coal-seams, but, as a rule, [unclear: when] the reptilian remains are found, the coal is either absent, or [unclear: very] poorly developed, as if the whole deposit had been formed [unclear: contemp]

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Photograph of houses on the Cheviout Estate

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raneously in an estuary in the Upper and fresh-water lagoons, in which dead vegetable matter accumulates to form coal-beds, while, at the same period, in the deeper seaward part, the murine reptiles disported themselves, and became entombed in the muddy bottom.

There are four localities where this group of strata (VI.) is exposed in the Cheviot Hills, and where coal might be found. At the Port, in the new road-cutting north of the landing-slip, the sulphur-sands and concretionary greensands containing silicified wood are present; but there is hardly any solid ground to be found, as the hill-side is a succession of gigantic steps from top to bottom. In consequence of this, the base of the formation, where it is possible coal might occur, cannot be examined.

At "the Brothers," two isolated sandstone rocks in the lower part of the Valley of the Jed, the section from the sulphur-sands to the base of the formation is clearly exposed in the banks of the river, and the dark greensands are seen to rest on a denuded surface of the older rocks, without the interposition of sandstone, or fire-clays, or any other indication of the presence of coal-seams.

The greensands at this place contain irregular-shaped concretions, and it was here that the very fine specimen of Cimoliosaurius (Mauiosaurus) haastii was found, which was a marine reptile, having the dimensions of a small whale.

On the north slope of the Valley of the Jed, at Marchlaw, a short way below the homestead, the section, though obscure, shows the presence of the concretionary greensands and conglomerates; and at this place they appear to overlie clay-beds that give rise to an extensive landslip, which has affected the surface just above where a quarry has been opened in the green sandstone, which is here associated with coarse conglomerates.

In the creek from this slip large masses of highly-indurated carbonaceous shale have been found, with streaks and films of bright coal adhering to them. Also, Mr. Sinclair, a very old resident in the [unclear: district], gave me a fragment from a large block of mica sandstone, of [unclear: exactly] the same mineral appearance as the cover of the Greymouth [unclear: coal]. This is the first time I have heard of a sandstone of this kind [unclear: occurring] on the eastern side of the mountains; and it was [unclear: unfortunate] that, owing to the débris from the slip, I had not a chance of [unclear: verifying] this important discovery. However, it may be noted that in [unclear: the] greensands mica is of far more frequent occurrence than in the [unclear: same] beds at Waipara, or in the Malvern Hill coalfield. I strongly [unclear: advise] that a search should be made in the hill-face above Marehlaw [unclear: by] driving or trenching, or, still better, by boring on the flat ground [unclear: immediately] eastward of the outcrop of the Amuri limestone.

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On the leading spur that runs north from Mount Caverhill I [unclear: found] a very full development of the concretionary greensands and [unclear: sulph] sands, the former containing fossil reptilian remains. These [unclear: stra] dip from an altitude of 800ft. under the upper greeusands to the [unclear: we] ward, the outcrop of the latter being marked by several copious [unclear: sprin] of pure cold water at 400ft. above the flats,

The Amuri limestone then follows, and can be traced four [unclear: mid] towards the Waiau River. Towards the east from the saddle [unclear: when] the large concretionary boulders of greensand cover the surface, [unclear: i] ground drops rapidly into the bush gully, from which timber [unclear: used] be sledged to the station. Mr. Smith informed me that from a [unclear: dis] tance, when on the sea coast, he observed very much slipped [unclear: ground] exposing what he took to be variegated clays; but I did not [unclear: success] in finding the locality. If there are any such beds, they must [unclear: be] expansion of the lower part of the formation, in which case [unclear: the] should be a fair prospect of finding coal.