Griffith in the Darling Basin

Latitude -34.286616, Longitude 146.035509

Located in the Riverina Region of NSW

Source: www.resources.nsw.gov.au/geological/overview/regional/sedimentary-basins/darlingbasin

Source: www.environment.nsw.gov.au/resources/parks/pomFinalCocoparraCocopara.pdf

Link to Detailed Map

Griffith is located in the Darling Sedimentary Basin, which contains over 8000m of Late Silurian to Early Carboniferous (but predominantly Devonian) sediments deposited in a number of distinct structural depressions. The majority of the basin sequences are covered with 100-200 metres of Cainozoic alluvium and minor thickness of Cretaceous Eromanga Basin sediments. Outcrop is limited, confined mainly to the east and west basin fringes or to sporadic occurrences coincident with regional basin structural highs.

Deep bores in the Griffith area have revealed two formations of unconsolidated sediments. The lower sequence has been deposited under lacustrine (lake) conditions and consists of sand, gravel, pipe clay and brown coal.

A small flow of basalt, located 13km W.N.W. of Griffith, is being actively quarried for road metal and aggregate for concrete. The basalt is fine grained, porphyritic in olivine and felspar and has regularly spaced columnar joints. Weathering has proceeded to a moderate depth, especially along joint planes and many of the olivine crystals have been partly or totally replaced by iddingsite.

The outcrop is not conspicuous, the surface expression being given by a very slight rise in elevation above the plain.

The Griffith Syncline is an assymetrical north plunging structure located between the beds on the western edge of the McPherson's Range and those north and south-east of Warbum Railway Siding. The beds of the western limb are gently dipping (up to 20° east) while those on the east dip at angles ranging from 10° to 60° west. Immediately north of Griffith, the axis of the syncline is exposed, the dips being approximately 10° northerly.

6.4km north-north-east of Griffith a deposit of gypsum (used in the manufacture of gyprock wall board) has been mined since 1934 for the production of 102,337 tons to the end of 1959. The deposit is located in the bed of Lake Wyangan and consists of crystals of selenite in clay and dunes of impure gypsite.

Outcrops of reddish-brown shale, 3km north-east of Griffith, have been mined for brick shale. The deposit is overlain by a bed of coarse conglomerate which has limited mining to a small area along the outcrop.

To the north East of Griffith lies the Cocoparra National Park protecting the Cocoparra Range which consists of Upper Devonian sandstones and conglomerates interbedded with finer shales. These sediments were later folded into a synclinal structure (the Cocoparra Syncline) with associated complex geological features such as folds and which have been eroded into the 'hogback' formation which now outcrops as the Cocoparra Range.

The crest of the range lies close to the eastern side of the national park and nature reserve and has a series of peaks of which the highest is Mount Bingar at 455m above sea level. Along the eastern edge of the national park the range falls steeply and has formed a broken rocky escarpment. Further north in the nature reserve the range opens out and is generally lower.

The more gentle western slope of the range has been eroded into a series of deep east-west valleys. These vary from Ladysmith Glen, a narrow gorge cut by Jacks Creek, to the relatively broad level valley formed by Woolshed Creek. The valleys are fringed by steep rocky and heavily eroded sides containing deep overhangs and waterfalls. The creeks and waterfalls run only for short periods after heavy rain or for longer periods after wet winters. There is permanent water in some springs and soaks.

Soils on the slopes are shallow clayey sands and are easily eroded. Erosion is a natural process in the area. Deep sediments have built up on the valley floors from erosion of the range, forming red and brown clayey sand and loam soils.

Getting There

Griffith is located in the Riverina Region of NSW east of Hay and northwest of Narrandera. Cocoparra National Park is located 35km from Griffith.