It may be necessary to observe that the height of the Cataract of the Macquarie River above the sea, was ascertained by barometrical admeasurement to be 650 feet. The country subsequently traversed is considerably lower. The specimens refer only to the geological formation of the distant interior.
Schorl Rock. — Colour blueish grey, fine grained, extremely hard. Composed of Tourmaline and Quartz. Forms the bed of the Macquarie at the Cataract, 75 miles to the N.W. of Wellington Valley.
Decomposed Mica Slate. — Colour white; yields to the knife; adheres strongly to the tongue.
Decomposed Feldspar. — Colour pale rose-pink; very fine grained; easily scratched with the knife; adheres strongly to the tongue.
Both specimens immediately succeed the Schorl rock at the Cataract, in large smooth-sided masses.
This formation may be said to terminate the rocks connected with the dividing ranges, since it is the last that occurs at their western base.
A little below the Cataract, the county undergoes a remarkable change, and becomes extremely depressed.
Porphyry with Feldspar. — Colour dull red, with white spots, or grey with red spots; very hard, compact, sonorous, magnetic. [See pp. 27 and 115.] Composition of Mount Harris, a hill called by Mr. Oxley, elevated about 170 feet above the level of the plains. It lies 65 miles to the N.N.W. of the Cataract, and is about 16 miles distant from the first of the marshes of the Macquarie.
Porphyry with Feldspar. — Colour grey with red spots, similar to the last. Was not observed to affect the needle. Formation of Mount Foster. Mount Foster is more than 200 feet in height, and lies about 5 miles to the N.N.W. of Mount Harris. From the summit of both, Arbuthnot’s range is visible, bearing nearly due east, distant 70 miles. [See page 28.]
Quartz Rook varieties — Slaty Quartz varieties. — Composition of the first elevations to the Westward of the marshes of the Macquarie, called New Year’s Range, a group of five hills. The loftiest about 200 feet in elevation; distant about 80 miles to the N.W. of Mount Harris.
Granite. — Colour red, coarse-grained. Composed of Quartz, Feldspar, and Mica.
Granite, Porphyritic. — Colour light red. Both occurring in the bed of New Year’s Creek, traversing it obliquely, and are visible for a few hundred yards only. This granite occurs about 16 miles from the Range in a N. by E. direction.
Old Red Sandstone. — Composition of Oxley’s Table Land, 500 feet above the level of the plains. It is broken into two hills, that appear to have been separated by some convulsion. [See page 81.] It bears N.W. by W. from New Year’s Range, distant 50 miles.
Old Red Sandstone. — Composition of D’Urban’s group. The highest elevation ascended during the expedition, being nearly 600 feet above the level of the plain in which it rises. It lies to the S.S.W. of Oxley’s Table Land, distant 40 miles, and the rock of which it is composed is much harder and closer.
Breccia. — Colour pale yellow, silicious cement. Composition of some trifling elevations to the North of New-Year’s range, with which it is doubtful whether they are connected.
A Selenite Chrystallized Sulphate of Lime
Crystallized Sulphate of Lime. — Found imbedded in the alluvial soil forming the banks of the Darling river. Occurring in a regular vein. Soft, yielding to the nail; not acted on by acids. — See Plate.
Breccia. — Pale ochre colour, silicious cement, extremely hard. Cellular, and sharp edges to the fractured pebbles. Has apparently undergone fusion. Occurs in the bed of the Darling in one place only.
Sandstone Varieties. — Colour dull red and muddy white; appears like burnt bricks; light, easily frangible; adheres to the tongue; occurs in large masses in the bed of the Darling; probably in connection with the rock-salt of the neighbourhood, which, from the number of brine springs discovered feeding the river, must necessarily exist.
Variety of the same description of rock.
Jasper and Quartz. — Showing itself above the surface of a plain, from which D’Urban’s group bore S. 40 E. distant 33 miles.
It is a remarkable fact, that not a pebble or a stone was picked up during the progress of the expedition, on any one of the plains; and that after it again left Mount Harris for the Castlereagh, the only rock-formation discovered was a small Freestone tract near the Darling river. There was not a pebble of any kind either in the bed of the Castlereagh, or in the creeks falling into it.
Last updated Sunday, March 27, 2016 at 12:00