Mount Freeland or the Ngala Range
This high range forms a conspicuous object in the profile of this part of the island. It derives its Fijian name from the old war-town of Ngala that was situated at an elevation of 1,500 or 1,600 feet overlooking Ngara-vutu on the west. The main mass of the range takes a crescentic sweep, 3 or 4 miles in extent and facing Natewa Bay. It incloses the coast district of Tunuloa. The steep mountain-slopes here rise to 2,000 feet and over, the greatest elevation being 2,740 feet. The densely wooded spurs of the range occupy most of the area between the town of Natewa, Kumbulau Point, and Mbutha Bay.
The summit is a long narrow ridge covered with a dense entangled mass of Freycinetia stems which render progress very difficult. The rocks exposed all the way up from the stream-courses in the vicinity of Ngara-vutu to the top, are almost all of the same type, namely altered augite-andesites. They are dark grey in colour and effervesce slightly with an acid, whilst occasionally they show a little pyrites.[[90]] Agglomerates were not observed and tuffs only in one locality, 1,200 feet above the sea, where a highly altered tuff composed of debris of the prevailing rocks was exposed. At an elevation of 500 feet there occurred a grey doleritic porphyritic rock, displaying large opaque crystals of plagioclase, and looking like a porphyrite. It exhibits a semi-ophitic groundmass, and is probably an intrusive mass. A description of it will be found under genus 10 of the augite-andesites (page [274]).
The general petrological characters of the principal summit of Mount Ngala point to its high antiquity as a volcanic mountain. It probably ranks among the oldest extinct volcanic vents in the island.
Proceeding along the coast from Ngara-vutu to Navetau, the Buli’s town of the Tunuloa district, one observes blocks of basic rocks. Farther to the eastward for a distance of two or three miles basic agglomerates and basic tuff-agglomerates prevail along the sea-border, being often extensively exposed in the cliff-faces of the hills. The rock composing the blocks is a hemi-crystalline pyroxene-andesite remarkable for the prismatic pyroxene in the groundmass, and referred to genus 17 of the hypersthene-augite sub-class.
I crossed the range to Ndevo on the other side of the peninsula from a place three or four miles west of Kumbulau Point, rising on the way to a height of 930 feet. For the lower 300 feet on the north slope basic agglomerates and basic tuff-agglomerates are exposed. They are made up of the same materials as those above described on the coast. Near and at the summit occur compacted brecciated tuffs made up of palagonitised basic materials but containing no lime, and these are associated with light greenish fine-textured hard tuffs of an acid character, but without lime or organic remains. In this last case the deposit is formed of mineral fragments (oligoclase, rhombic and monoclinic pyroxene, &c.), the debris of a hemi-crystalline volcanic rock, and a quantity of greenish alteration products.
On the south side in the vicinity of Ndevo the sea-border is composed of calcareous palagonitic clays and tuffs containing pteropod shells and large tests of foraminifera in abundance. These deposits, which are horizontally bedded, extend a mile inland and reach to between 250 and 300 feet up the slopes. A hot spring is stated to occur between the tide-marks near Ndevo.
At intervals all along the coast between Ndevo and Nuku-ndamu, passing on the way the villages of Koro-i-vonu, Tuvumila and Kanakana, fine and coarse basic tuffs, often calcareous, are to be seen exposed in the sea-cliffs and in the low hills behind. They are bedded and dip 5° to 10° W.S.W. near Ndevo and 15° to 20° S. b W. south of Kanakana. The lower slopes of the Ngala mountains here approach the coast, and it is highly probable that the submarine tuffs which form the sea-border extend a considerable distance inland and to some height above the sea. Between Nuku-ndamu and Tukavesi, where the mountains rise close to the beach, occur basic agglomerates and agglomerate-tuffs, derived from basaltic andesites. A specimen of the last named represents an uncommon type of basaltic rock (sp. gr. 2·85), which on account of the character of the felspars and of the pyroxene of the groundmass is referred to the prismatic sub-order of the orthophyric order of the hypersthene-augite andesites (page [290]).
It may be inferred from the foregoing remarks that whilst the main elevated mass of the Ngala Range is composed of altered basic andesites, the product of ancient eruptions, the basic agglomerates, tuffs, and clays, which occur on the lower slopes and in the outlying spurs, are of later date. These tuffs and clays are evidently of submarine origin, at least in the lower levels; but although fossiliferous deposits were not observed at greater elevations than 300 feet above the sea, it is probable that future investigators will find them at much higher levels. Their discovery, as before noticed, at an elevation of 1,100 feet in the adjacent Waikawa mountains, renders it likely that as in the case of the mountainous districts of the main portion of the island the whole of the Natewa peninsula was at one time submerged, or at least all the region excepting the summit of Mount Ngala.