Italowie Geology walk
This walk allows us to explore the phenomenon popularly known as ‘snowball earth’ although this
is perhaps a misleading description. It occurred at a time known as the Cryogenian Period dating
from 850 to 635 million years ago when there were protracted periods of glaciation with some warm
interludes, which were sufficient for substantial reefs to develop.
The Sturtian glaciations, whaich began about 700 million years ago, gave rise to some depth of a
glacial deposit known as Bolla Bollana Tillite which was overlain by shale, dolomites, siltstones and
limestone after the cold period ended. Evidence of a younger glaciation, Elatina at 630 mya, is also
here (as it is in the Trezona Circuit of Haywards Huts Walk in Flinders Ranges National Park).
All these rocks belong to the Umberatana Group (see stratigraphic column), which is overlain by
the younger Wilpena Group, of which the Rawnsley Quartzite forms the prominent ranges here – the
rim of Illinawortina Pound, Mount John Roberts in the Blue Range and the main Gammon Plateau.
All of these are visible from the road above the starting point, at Checkpoint B6. (Rawnsley Quartzite
has given rise to the striking landscapes of the central ranges further south around Wilpena.)
The earth has also been restless here. In some places on the walk, faulting has brought together
rocks totally out of sequence. The major fault is the very long and forceful Paralana Fault crossed at
the end of the walk but the effect of minor associated faults is pointed out along the way.
Later, as sediments in the great Adelaide Geosyncline were being compressed into folds, earth
movements promoted a melting pot of mineralising fluids in the basal sediment. Fragments of
adjacent rock layers (breccia) were picked up by the upward and lateral flow of this material. The
dome like formations so formed are called diapirs, and while miners found interest here mineral
prospects were poor (Red Hill and Loch Ness).
The walk starts on the upper layers of the Umberatana Group – the dark green siltstones of the
Amberoona Formation and finally descends into the lower layers of tillite.
Distance and time: 15.8 km linear walk; allow 8 hours one way.
Altitude range: 290 m (Italowie Gap) to 400 m (saddle near Mt McKinlay Spring).
Access: The walk can be started from either trailhead:

Grindell Trailhead at Grindell hut; turn off the Arkaroola Road at 8.2 km from the finger post at Balcanoona.
The trailhead below the hut is a further 18.3 km along this 4WD track.

Italowie Gap Trailhead; there is a park information bay on the Copley road 15 km from the finger post at
Balcanoona. The Italowie Gap Trailhead is by the park signboard.
Track: Easy grade on formed walking track; some service track walking and creek bed. You will need two cars, one parked
at each Trailhead. The road distance between the two is 41 km. Driving can be reduced if the group splits into two parties,
one starting at each end, and swapping cars for the return journey.
Distances marked in km decrease as you approach Italowie Gap Trailhead.
Notes read as for a start from Grindell Trailhead.
15.8 Grindell Trailhead – Checkpoint B6
Follow the foot pad up hill and around the house. There are three buildings in this vicinity. Two
are solid modern structures built by the previous lessees of Balcanoona Station
(B.H. MacLachlan). The third, a rough hut behind the main house, was the residence of John
Grindell, who was suspected by his son-in-law and neighbour at Yankaninna, George Snell, of
rustling Yankaninna cattle. When George Snell disappeared in August 1918, his brother
became suspicious and Beltana police assisted by Aboriginal trackers eventually found a remote
spot where Snell’s body appeared to have been cremated. The story (in Cloud over the
Gammon Range) related how Grindell denied all knowledge but admitted to the crime when
drunk and was given a death sentence.
Return to the main track just below the house and continue west above the creek. Balcanoona Creek
rises on the eastern slopes of Benbonyathe Hill picking up water from steep gorges such as
Bunyip Chasm in the Blue Range.
15.0 {GEO 1 Black Oak on scree} The track has left the brecciated substrate near the house and is
now is over dark green siltstones of the Amberoona Formation and passes a scree slope of
loose stone which is a preferred habitat for the Black Oak which is here.
14.2 Mt John Roberts, part of the Blue Range rim of Rawnsley Quartzite, is visible ahead.
13.6 Checkpoint K1 – junction of track to Mt McKinlay Spring (no vehicle access).
12.6 The pale coloured soils are characteristic of the Balcanoona Formation limestones which form
a range of hills to the east running parallel to the track as far as Mt McKinlay Spring. A steep
section of track brings you to the Gibber Plain.
12.2 {GEO 2 Gibber Plain}; an area of sandy clay with depressions and a stony surface This is a
Pleistocene (1.6 million – 10 000 years ago) river terrace derived from material eroded from the
surrounding hills. The very stony surface of ‘gibbers’ is a lag accumulation over the sands and
clay which once filled all the valleys to the same level. Wind and water erosion have removed
most of the finer sediment, leaving the rocks to armour the surface. Some stones on the
surface appear to have been sand-blasted during arid periods, probably about 16 000 years
ago.
12.00-11.8 {GEO 3 Red Hill} Red Hill in the middle distance is located on a diapir; Loch Ness copper
mine lies at its northern edge, where movement of the diapir allowed deep-seated mineralising
fluids to rise. These later developed into ores of copper and other minerals.
From here, there are some high points to recognise in the Gammon Range (all bearings
magnetic).
Mt McKinlay Bluff
6 km
232°
… and rock slide
5.5km
242°
Cleft Peak
6.5 km
270°
Prow Point
10 km
288°
Mt John Roberts
4 km
306°
Benbonyathe Hill
8 km
341°
Warden Hill
5.5 km
31°
These features are all comprised of Rawnsley Quartzite
Red Hill
1.0 km
253°
11.2 to 11.2 Once off the Gibber Plain, the track crosses Ulupa siltstones which have been contorted
by the diapir activity. Breccia continues all along the track as far as Mt McKinlay Spring, which
is the extent of the diapir.
10.2 Checkpoint K2 – mid-Italowie creek
This wide creek crossing carries shady red gums and pines; like Balcanoona Creek, Italowie
Creek rises deep in the Gammon escarpment, below Prow Point and Mt Changeweather.
8.2 on the foothills to the east is a lens of red Elatina Formation siltstone marking the position of
the Elatina-Nuccaleena Formation horizon, which indicates the end of a glacial period.
7.6 to 7.4 In the middle distance between these two points there are further glimpses of the brick
red Elatina Formation as small red outcrops.
7.4 From this point thinly laminated green Ulupa Siltstones are characteristic of the track.
6.4 Green basaltic fragments have been brought to the surface by diapir activity and cemented in a
fine grained carbonate to form a breccia.
6.0 Checkpoint K3 – Mt McKinlay Spring
The spring has encouraged large Red Gums and very often the place is a haunt of goats. Walk
downstream following the markers, noting on both right and left banks fragments of shale
aligned in a carbonate matrix suggesting that the breccia flowed. Fragments of contorted dark
shale, dolomite and dark green basalt were probably squeezed into a fault zone here. (This
probably one of the minor fault zones associated with the Paralana Fault (see at 15.8 km).
5.8 At the blue-top post on the right, walk up the small gully.
5.4 to 5.2 {GEO 4 Ironstone} This small creekline forms the boundary between an outcrop of
Rawnsley Quartzite to the south-west and Balcanoona Formation to the north-east. Between
them is a blue-black structure of hydromorphic ironstone, which was deposited from shallow
ground waters which circulated through Balcanoona Formation in the fault zone, dissolving iron
and manganese from the dolomite to form a thick, dark crust at the ground surface.
{GEO 5 Three Formations} The saddle gives a good view into Italowie Creek and gorge; the three
main rock types can be seen – dolomite to the left, dark tillite ahead and quartzite to the right.
5.0 A scree of quartzite cobbles provides ideal growing conditions for Black Oak (as at 15.0 km).
The scree covers a broad fault zone; fault breccias of quartzite are visible along the way.
4.6 to 4.8 Descend a steep pine-clad slope of brick red laminated siltstones and dolomite (Angepena
Formation) to join Italowie Creek. Follow the creek bank to . . .
4.4 Checkpoint K4 – near a copse of River Red Gums
Nearby a sheer rock face is a massive bed of tillite. Walk downstream to your right.
3.0 {GEO 6 Bolla Bollana Tillite} Italowie Gorge is carved into massive Bolla Bollana Tillite of the
Sturtian glacial period about 700 million years ago. Here is a good example showing large rocks
embedded in a fine-grained sandstone matrix. Weathering of the matrix (green when
deposited) has resulted in a red-brown iron oxide stain which gives the rock an overall dark
appearance.
Erosion notches to the west along the creek give views through to the pale Rawnsley Quartzite,
which is adjacent. Normally there would be 3 km of sediment between the tillite and the
quartzite, but a fault parallel to the gorge has forced the tillite up against the quartzite.
0.8 Another good example of tillite, just before the track leaves the gorge and turns to cross a wider
creek where Italowie has been joined by Doctor Chewings Creek. Dr Charles Chewings was a
geologist and anthropologist who worked mostly in the Northern Territory ,but also in the
northern Flinders Ranges in the early years of the twentieth century.
The track now follows an old pebbly bed of Doctor Chewings Creek which now floods rarely.
{GEO 7 Paralana Fault} At this point look back to the hills through which you have just walked. A
spectacular bluff of Rawnsley Quartzite can be seen to the west, and the dark Balcanoona Range
of Bolla Bollana Tillite extends to the north-east. The distinct notch between these two bold
outcrops is the result of a major fault or ‘crush zone’, consisting of rock broken and ground up by
movement along the fault. The long fault the Paralana Fault which dips to the west, is here the
eastern limit of the tillite – and the Flinders Ranges. The tillite has been pushed up by 5 km from
the west to override younger rocks to the east.
0.0 Checkpoint K5 Italowie Gap Trailhead – park information shelter.
Text prepared from field notes supplied by Nick Langsford
GLOSSARY OF GEOLOGICAL TERMS
For composition of different rock Formations and Groups, see Stratigraphic Column.
basalt Dark green igneous or volcanic rock, made up mainly of feldspar and ferromagnesian mineralsalumino-silicate minerals with notable amounts of iron and magnesium.
Bolla Bollana Tillite Product of the Sturtian glaciation; occurs west of Paralana fault (see Merinjina Tillite)
breccia Broken-up rock; can form by a wide range of processes, with angular fragments becoming cemented.
carbonate General term for the rock forming carbonate minerals; mainly calcite which forms limestone,
dolomite and magnesite – rocks of the same name.
copper Bright pink metal, Cu. Important industrial commodity
crush zone Band of broken and smeared out rock within a fault zone
Cryogenian Period The base of this Period is defined at 850 million years ago (Ma), and its top is the base of
the Ediacaran Period, which as yet is not defined by a precise time, but is about 630 Ma.
diapir Common in the northern Flinders Ranges. A body of broken rock which originally contained enough salt
to allow it to flow or be forced upwards and outwards to intrude and disrupt younger rocks.
dolerite Altered basalt.
dolomite Rock that is largely composed of the dolomite mineral, CaMg(CO3)2
escarpment, scarp Cliff or steep slope, often the result of fault movements.
fault, faultline, fault plane A fault is a physical break in a body of rock. Faults may be of huge displacement,
many kilometres (e.g. Paralana Fault), or only a few centimetres.
Formation A sedimentary or volcanic rock unit which can be physically mapped and defined by features
observed in the field.
gibber Rock fragments which have accumulated as pavement due to the removal of all fine sediment by wind.
Individual fragments are darkened by a thin layer of iron oxide ‘desert varnish.’
Group A unit which includes two or more Formations of usually sedimentary rocks
hydromorphic Formed from aqueous solution.
ironstone A rock with high iron oxide content.
iron A metallic element, Fe. Important industrial commodity.
lag A thin layer of coarse material which remains on a surface after the winnowing of all fine material by wind
or water.
laminated, laminations Thin, regularly banded layers of sediment; almost always reflects bedding.
limestone Sedimentary rock mainly made of calcium carbonate.
manganese A hard grey metal, Mn. Used as alloy in steel manufacture.
Merinjina Tillite Product of the Sturtian glaciation; occurs east of the Paralana Fault (see Bolla Bollana Tillite).
Pleistocene Period 1.6 million to 10 thousand years ago.
quartzite A rock which was originally quartz sandstone which has been heated or compressed sufficiently to
fuse the grains together producing a tough resistant rock.
scarp, escarpment Cliff or steep slope, often the result of fault movements.
shale A sedimentary rock largely made up of very fine grained material which includes a large proportion of
clay minerals, micas, and quartz.
siltstone A rock composed of silt-sized (less than 0.1 mm) mineral grains – usually mainly quartz.
tillite Rock formed as a result of glacial activity, containing a very wide range of grain sizes, usually including
some large fragments obviously not locally-derived, known as erratics.