FIELD GEOLOGY OF THE SHOALHAVEN DISTRICT (PART 9)

CHAPTER 4 (CONTINUED)

Excursion 4b
Nowra – Berry via Cambewarra Lookout (17 miles)
The rocks seen are similar to those seen on the previous excursion. In addition, a number of interesting small igneous intrusions are encountered.
Route: Nowra-Cambewarra Range-Bellawongarah-Berry.
Proceed to the Cambewarra Range via the Moss Vale road. Through Bomaderry, Permian marine sediments are seen and the road continues over undulating country to the foot of the range. See Excursion 3b. 
Stop 1. In the first road cutting after the sign ‘Cambewarra Mountain’, two very weathered dykes may be seen intruding weathered Berry siltstone. Weathered mica is their main characteristic and this identifies them as related to the Good Dog intrusion. At least 14 similar dykes occur along this road and the next ½ mile should be walked to see them properly.
Stop 2. Cars can be parked on the left 400 yards past the previous stop. Several lamprophyre dykes occur in cuttings across the road (watch for traffic!).The less weathered ones contain fine crystals of hornblende. Boulders of similar rocks occur in adjacent paddocks. Marine fossils abound in some of the siltstones.
The view to the south is rewarding. One of the most remarkable features is the extent to which the lower boundary of the Berry Formation marks the edge of the cleared country. Soil derived from the Nowra Sandstone is much less fertile.
Stop 3. Just beyond a group of farm buildings on the left, comparatively unweathered tuff outcrops on the right. From here upwards, the soil is mainly derived from volcanic rocks and supports luxuriant rain forest.
Stop 4. The road reaches the crest of the range at an altitude of 1,600 feet, where outcrops of the Cambewarra Flow occur and may be examined. The views of Kangaroo Valley and the coastal plain are very fine. In the valley, the upper cliff is of Hawkesbury Sandstone and the lower of Budgong Sandstone.
Diversion. Take the rough road which ascends to the left of the lookout. This climbs steadily for 1 ½ miles until the top of Cambewarra Mountain is reached at an altitude of 2,000 feet. Near the top the change of soil as the Hawkesbury Sandstone is reached is very clear.
The highest point (1 mile further on, altitude 2,050 feet) is ablaze with wildflowers in spring. The valley on the left is upper Budgong Creek. Good specimens of agate may be found by walking down the valley for 1 mile, where the limit of Excursion 4c is reached.
If the road is followed further, outcrops of the Coal Measures will be seen after 3 miles and the road deteriorates after 5 miles when a damaged bridge makes a return to the Moss Vale road necessary.
Stop 5. Cambewarra Lookout is well known for its coastal panorama. Good Dog Mountain, on which the lookout is situated, is a small outlier of Hawkesbury Sandstone, outcrops of which are seen on the ascent. The lush vegetation around the mountain includes stinging trees and numerous ferns. See Excursion 5a for more information.
Take the road to Berry where the lookout road begins to ascend. At the junction, two very weathered dykes and weathered Coal Measures sediments are seen.
Stop 6. A disused quarry on the left 400 yards further on supplied road material. Outcrops of coal and weathered lithic sandstone are found in it. Perfect clay pseudomorphs after augite may be found on the surface to the left of the track leading into the quarry. Some of these form star shaped twin groups and they have evidently weathered out of a lamprophyre dyke.
About 100 yards after the quarry, two weathered dykes intersect the Coal Measures on the right.
Stop 7. As Kangaroo Mountain is approached 1 ½ miles further on, a track is seen leading off on the left. By way of this track, the mountain may be ascended. It is a narrow residual of sandstone, whose flat swampy top abounds in Christmas Bells in summer.
Beneath the mountain is the Kangaroo Mountain Sill. This is about 100 feet thick and is composed of basanite, a rock resembling basalt in hand specimens. Where the track leaves the Berry road, weathered basanite has formed red soil exposures, from which agate may be collected.
From this point on, the road skirts the edge of Kangaroo Mountain, with views of the coast below. Creeks draining from this area have yielded fine specimens of moss agate weighing up to 50 pounds. Associated with the agate are veins of pyrolusite and it is thought that both formed at the time when the Kangaroo Mountain Sill invaded the Coal Measures.
The descent to Berry repeats the stratigraphy observed previously. Good outcrops of the Cambewarra Flow are seen on the right and the view of Broughton Head is excellent. 

Excursion 4c
Nowra – Brown’s Mountain (14 miles return)
Good outcrops of the Budgong Sandstone are seen and jasper from the base of the Cambewarra Flow is common.
Route: Proceed along Illaroo Road after turning left on the northern side of the Shoalhaven River bridge. After 4 miles, take the branch leading to Brown’s Mountain.
Stop 1. Tapitallee Creek carries down large quantities of jasper and some agate from the range above. The gravel is deficient in volcanic rocks, since the Cambewarra Flow barely reached this far south. 
Proceed towards Brown’s Mountain. The entire climb may not be possible by vehicle due to landslides carrying away the road. Good marine fossils may be collected from freshly fallen blocks by the roadside. At higher levels, the Budgong Sandstone (equivalent to the Broughton Sandstone further north) is seen. 
Stop 2. At a height of 1,250 feet, the road branches. The right branch, if followed for 2 ½ miles, leads to the Moss Vale road.
Excellent golden jasper occurs along this track, apparently at the base of the Cambewarra Flow. 
Proceed along the left branch. After 500 yards, an interesting waterfall on the left plunges into the valley over cliffs of Budgong Sandstone. About 500 yards further on, cleared country is entered. Jasper of all colours may be found along the track, which runs below the summit of Brown’s Mountain on the right. The track to the left leads to the Budgong road.
The ruined farm house is one of many in the hills around Nowra. 
Upper Budgong Creek Waterfall
 June 1964
Proceed through the bush behind the ruin, heading towards the valley visible through the trees. A tributary of Budgong Creek drops over a fine waterfall at a point where the Budgong Sandstone may be studied to advantage. Jasper and agate are found in the gravel of this and all other branches of Budgong Creek in this vicinity. 
The track may be followed for at least another mile and a climb of 700 feet from the next valley leads to the summit of the Cambewarra Range (Excursion 4b).
Return to Nowra by the same route.

Excursion 4d
Nowra – Budgong – Kangaroo Valley (20 miles)
Budgong Creek drains the south-west part of the Cambewarra Range, of which Mt Scanzi is the westernmost peak. The sediments seen on this excursion range from the Conjola Formation to the Hawkesbury Sandstone. Typical quartz minerals are common in Budgong Creek.
Route: Nowra-Illaroo Road-Tapitallee-Budgong-Mt Scanzi-Kangaroo Valley
Some parts of the road are in poor condition. In addition to the direct route, there are several diversions to places of interest.
Proceed as in Excursion 4c. After 4 miles, take the left branch towards Budgong. The road crosses Bengalee Creek, descending through the base of the Berry Formation at a level of 250 feet. Between this point and Kangaroo Valley, the road frequently runs close to this boundary, with uncleared Nowra Sandstone country on the left and cleared Berry Formation on the right.
At the first major fork (2 ½ miles from Illaroo Road), keep straight 
Nowra from Illaroo Road April 1969
ahead. The left branch leads down to farms on the Shoalhaven River near Burrier. At the top of the hill immediately after the fork, a road to the right leads, after a very steep climb, to Brown’s Mountain. About 1 ½ miles further on, a road to the left gives access to lower Budgong Creek.
Nowra from Brown's Mountain June 1964
Diversion 1. (7 miles return) At the road junction, the Nowra Sandstone is at a level of 650 feet and outcrops well in a creek. Some 300 yards downstream a fine view of the Shoalhaven River opens out. Turn left along this road just past the creek crossing. After 1 mile, the road descends sharply 
Valley of Budgong Creek Kangaroo Valley June 1964
through the Nowra Sandstone, Wandrawandian Siltstone and Conjola Formation, which may be examined at convenient points. At Budgong Creek, good agate may be found. The track to the left near the creek leads down to the Shoalhaven River. A fine alluvial terrace skirts the river just above its junction with Budgong Creek. The river gravel consists principally of quartzite, rhyolite and granite. Devonian rocks outcrop on the opposite bank; the river (elevation 30 feet) is at the base of the Permian and therefore of the Sydney Basin sedimentary pile, but no clear unconformity is seen here.
Return to the Budgong road. About ¾ mile further on, a similar road on the left also leads down to Budgong Creek. Keep straight ahead for Mt Scanzi and Kangaroo Valley.
Stop 1. Budgong Creek is crossed after a rough descent through the Nowra Sandstone. The gravel should be examined for red and green jasper, agate, and petrified wood.
Continue for 1 mile. Fine views of the cliffs high above are seen. At a point near several old buildings on the left, the road to Kangaroo Valley turns to the right.
Diversion 2. The road ahead leads out through the Morton National Park to a point high above the junction of the Shoalhaven and Kangaroo Rivers (14 miles return). With care, the descent to the junction can be made on foot from the end of the road. The last 400 feet is very steep and shows fine exposures of Upper Devonian quartzite. The river is 100 feet above sea level at this point. The peculiar angle at which the Kangaroo River meets the main stream suggests that this is an example of river capture (see Chapter 1).
Return to the Budgong road and proceed towards Kangaroo Valley. After a steep climb of 600 feet, a gap in the range is reached. 
Budgong Creek valley from Mt Scanzi August 1966
Stop 2. Mt Scanzi is quite isolated from the rest of the Cambewarra Range. At the gap, fossiliferous Berry Formation siltstone outcrops, while, just above, the Budgong Sandstone outcrops prominently. 
Diversion 3. Take the road to the left leading up the mountain. Mt Scanzi has an elevation of 2050 feet and is 2 miles west of the gap. If the road is impassable, the walk is very worthwhile.
The author at Budgong Trig, 
Mt Scanzi October 1966
Examine the sandstone in the cliffs alongside the road. It is a greenish tuffaceous sandstone, with occasional marine fossils. The volcanic fraction within this rock decreases westerly from the Gerringong Volcanic centre. The Cambewarra Flow is not found here; apparently it never reached this far.
Veer to the right at any forks in the road as the vegetation is much denser on the southern slopes, and the ascent more difficult. From here take the best route to the summit.
Stop 1. Scarcely an acre of Hawkesbury Sandstone survives as a tiny outlier. The name of the mountain commemorates a Polish immigrant whose epitaph is carved into the sandstone. From Budgong Trig. Station, the unsurpassed view takes in Kangaroo Valley, Mt Gibraltar, Fitzroy Falls, Currockbilly, Pigeon House, and Cambewarra Mountain. 
Beneath the sandstone, fragments of carbonaceous shale indicate the presence of a small outlier of the Coal Measures. 
Return to the Kangaroo Valley road. From the gap, the road improves and the descent reveals outcrops of the Berry Formation and Nowra Sandstone as expected. 
Questions
1. In what way has the distribution of the Hawkesbury Sandstone affected access into Kangaroo Valley? 2. Show how the volcanic nature of the upper Berry Formation increases from Mt Scanzi to Woodhill. 3. Present evidence for at least two periods of igneous activity in the Cambewarra district. 4. Explain how the summit level of the Cambewarra Range is consistently around 2,000 feet while the Coal Measures increase in thickness in a northerly direction. 5. What is the probable source of the quartz minerals found in this area? 6. Which fossils are characteristic of (a) the Coal Measures, and (b) the Berry Formation? 7. Comment on the cliff forming ability of the various members of the Berry Formation. 8. Did the close of Permian volcanic activity correspond with the last deposition of marine sediments? Present evidence for and against.

Song Studies. Bible studies based on hymns and songs
Shoalhaven District Geology.

Comments

Post a Comment

Popular posts from this blog

Image
FIELD GEOLOGY OF THE SHOALHAVEN DISTRICT (PART 6) Chapter 3: The Nowra District   Nowra  is strategically built on the first flood-free site upstream on the south bank of the Shoalhaven River. It was not an important settlement until about 1880, when Terara was extensively flooded. Soon after, the coming of the railway and the construction of the present road bridge assured its development as a rural centre. Today, it is a rapidly growing town, with developing industry, tourism, and defence establishments.  Several factors dominate the geology of the area. The Nowra Sandstone has provided a resistant surface, broken only by the Shoalhaven River and a few of its tributaries. Where this sandstone has dipped below sea level at Nowra, an extensive flood plain has developed, the origin of which is of considerable interest and will be explained later.  Coolangatta Mountain  is the only unusual feature in the area. It is really an outlying part of the Cambewarra Range,...
Read more
Image
FIELD GEOLOGY OF THE SHOALHAVEN DISTRICT  NSW AUSTRALIA (Part 1)   John G Paix 1970 (Reviewed 2013) ©  Australian Field Geology Club visit to the Cambewarra Range February 1965   A Word or Two of Explanation This book was written in the years 1968-1970. At the close of my time as a Science teacher at Nowra High School in 1967, I undertook to write a report titled " The Geology of the Shoalhaven Shire " for the then Shoalhaven Shire Council, which was published by them early in 1968.  It soon became apparent that there was much additional information, especially relevant to the Geology excursions I had conducted during my 5 years in Nowra, which was not included in that book.  What you see in front of you today was prepared for publication over the next three years and I fully expected to see it published in 1970. For reasons that do not matter at this distance in time, this never happened. I was left with a typed, proof-read copy, all the maps, drawings, p...
Read more
Image
FIELD GEOLOGY OF THE SHOALHAVEN DISTRICT (PART 23) CHAPTER 15: THE CLYDE RIVER VALLEY T aking its rise at an elevation of 2,500 feet near Sassafras, this small river flow south and descends by way of a great canyon to a level of 200 feet at Yadboro. It does this in less than 20 miles, yet it is a further 40 miles to the sea downstream. This is a peculiar result of the dip of the Shoalhaven group sediments. At one time, these must have extended further south than at present. When the area was uplifted, it was tilted to the north, so that the ancestral Clyde River had to erode its bed against this trend.  This undoubtedly led to the formation of many waterfalls and the evolution of the canyon upstream from Yadboro.  The southern edge of the sandstone scarp presents a bold face and is broken into numerous outliers. Some such as The Castle and the Pigeon House are well known to bushwalkers, but there are many others. They all have a similar structure, being capped by cliffs of the...
Read more