DEPARTMENT OF MINES, VICTORIA GEOLOGICAL SURVEY UNDERGROUND WATER INVESTIGATION REPORT No. 4 THE GEOLOGY AND UNDERGROUND WATER RESOURCES OF THE TOORADIN AREA by J. J. Jenldn, M.Sc. D. E. Thomas, D.Sc., Director of Geological Survey Issued by E. Condon, LL.B., Secretary for Mines, under the direction of the Hon. W. J. Mibus, M.L.A., Minister of Mines 1962
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DEPARTMENT OF MINES, VICTORIA GEOLOGICAL SURVEY
UNDERGROUND WATER INVESTIGATION
REPORT No. 4
THE GEOLOGY AND UNDERGROUND WATER RESOURCES OF THE TOORADIN AREA
by
J. J. Jenldn, M.Sc.
D. E. Thomas, D.Sc., Director of Geological Survey Issued by E. Condon, LL.B., Secretary for Mines, under the direction of the
Hon. W. J. Mibus, M.L.A., Minister of Mines
1962
COttlenti
1.
2.
3.
introduction ..
Physiography
Geology and Underground Water—
PAGE
3
3
A. Quaternary .. 3 (a) Mangrove Swamps 3
(b) Salt Marsh 3
(c) Swamp Deposits .. 4
(d) Wind-blown Sands • . 4
(e) Deltaic Sands .. 4
B. Sands and Clays of ?Pliocene Age 5
C. Upper Tertiary Marine Sands 5
D. Miocene Ferruginous Sandstones 5
E. Miocene Marine Sands and Limestones 5
F. Lower Tertiary Volcanics 5
G. Silurian Rocks 6
4. Conclusions .. • • 6
5. References • • 6
6. Appendices : Appendix 1—Summary of Bores 7
Appendix 2—Water Analyses 16
Appendix 3—Bore Logs 24
7. Geological Map of the Parish of Sherwood At Back
315 /62.
THE GEOLOGY AND UNDERGROUND WATER RESOURCES
OF THE TOORADIN AREA
1. Introduction. The results of a survey of the underground
water resources of the Tooradin area are set out in the following report. The area covered comprises the whole of the parish of Sherwood and adjoining parts of the parishes of Koo-Wee-Rup and Cranbourne.
The geological formations are briefly described and an account of underground water occurrences in each parish is given.
It is difficult, in the case of many of the bores and wells, to say with certainty from which formation the water is coming. Logs or other Ethological data are lacking for the majority of bores, although occasionally complete logs (of varying reliability), and sometimes data on the aquifer only, are available. The bore logs are set-out in Appendix 3. Other lithological data are given in the Summary of Bores (Appendix 1).
2. Physiography. The physiography of the area has been described
in some detail by Hills (1942) so that a brief outline only will be necessary here.
The area under consideration is situated in the south-western portion of the Koo-Wee-Rup Basin. This basin comprises the northern part of the Western Port Sunkland and is bounded on the east by the Health Hill Scarp, on the north by the foothills of the Eastern Highlands, on the west by the undulating to hilly country of the Cranbourne—Tyabb area, and on the south by the tidal mud-flats at the head of Western Port Bay.
The western part of the area, in the parish of Sherwood, is undulating and consists of Silurian and Tertiary rocks overlain in part by Pleistocene dune sands.
East of Clyde and Five Ways the country is quite flat except for occasional sand ridges. The flat country is swampy, the soils gradually becoming less sandy towards the east and merging into the black friable clays of the Dalmore area.
The general direction of drainage is from north-west to south-east, i.e., in the same direction as the main sand-ridge trends. However, drainage has been retarded by the sands at many places and, as a result, swampy areas occur between the dunes. The more extensive of these have now been drained artificially.
In the Koo-Wee-Rup swamp itself no well-defined natural drainage courses of any extent exist and it is probable that, before it was artificially drained, the area was a more or less continuous body of water.
Several inlets occur along the coast (" The Inlets ", Sawtell Creek and Rutherford Creek) and these are probably drainage features of several different origins, owing their present well-defined condition to tidal scour.
3. Geology and Underground Water.
A. Quaternary : (a) Mangrove Swamps (Qa).
Just below high-tide mark in the northern part of Western Port Bay is a well-defined zone of mangroves (Avicenna officinalis). The zone is almost continuous and averages about 100 yards in width. Its inner margin generally marks the limit of high tide, only unusually high seas coming further inland and inundating the salt marsh behind the mangroves.
The mangroves are growing in grey foetid sand and clayey sand. Occasionally there is a very narrow beach between the mangroves and the salt marsh, and this generally consists of a thin veneer of yellow sand over the grey sand of the mangrove swamps.
(b) Salt Marsh (Qb).
Landward of the mangroves is another well-defined zone—the salt marsh. It is as continuous as the mangrove zone but of more variable width (0-1 mile).
The salt marsh may be divided into two sub-zones-
1. A strip consisting of an association of salt-tolerant shrubs immediately adjacent to the mangroves.
2. An association of salt-tolerant herbaceous plants behind this strip. Some bare areas also occur here.
The inner margin of the salt marsh is marked by a narrow belt of Swamp tea-tree (Melaleuca ericifolia) except in the far east of the area where the marsh gives way to grassland.
Behind the belt of Melaleuca, on deposits of wind-blown sand, is an association of Eucalyptus, Banksia, &c.
The deposits of the Salt Marsh zone consist at the top of 5-12 ins. of brown peat and peaty clays with a high water-holding capacity (92-421 per cent. of the dry weight : Patton, 1942). The salt content of the soil moisture is high, generally ranging from 40,000 to 90,000 ppm. of sodium chloride.
The peats overlie grey sandy clays and sand which are wet, most of the water lying just on top of the sandy clays.
Near and parallel to the seaward margin of the salt marsh low sandy beach ridges sometimes occur ; they are less than a foot above the general level of marsh but support an association of Melaleuca and composites.
(c) Swamp Deposits (Qc). In the eastern part of the area there were once
extensive swamps but these have now been drained. Originally the swamps carried reeds and rushes with Swamp tea-tree in the slightly elevated and marginal areas. Little of the original type of vegetation remains now being confined to drains and isolated patches here and there.
The swamp deposits consist of peat, peaty clays, grey clays and sandy clays, the latter often with yellow and red mottling. The peaty deposits are dark grey to black and contain about 15 per cent. organic matter. Some of the more sandy swamp fringe deposits contain about 7 per cent. organic matter (Goudie, 1942).
As far as can be judged from the available bore logs, the swamp deposits have a maximum thickness of about 40 feet. It is not known if any underground water is being drawn from these deposits but it is thought that this is unlikely since, in recent boring near Dalmore, no water was encountered in them. It is probable that shallow producing wells in this area reach the older, more sandy beds, underneath (e.g., Quaternary aeolian or deltaic sands).
Various agricultural pursuits are now followed on the reclaimed area, including dairying, beef cattle and sheep. Market gardening has also been carried on for some time and is expanding.
(d) Wind-blown Sands (Qd). Deposits of wind-blown sands are extensively
developed in the area, often in the form of north-west—south-east trending dunes. The dune ridges become less distinct near the coast, for example, on the Warneet peninsula, where their jumbled appearance may be due to re-working.
At Blind Bight there is a series of dune ridges parallel to the shore. The dunes behind them, which they intersect, are younger and show no soil profile as do the dunes further inland (see below).
Towards the east, the dunes become partly buried by the younger swamp deposits, some of their crests remaining as ridges above the general level of the swamp.
West of the swamp, and adjacent to the main dune deposits, are sandy areas in which no distinct dune features are discernible. These are probably in part low dunes modified by erosion, and in part redistributed sands derived from the dunes.
Several shallow wells have been sunk in the dune sands, particularly near Tooradin, where the water found is at the base of the dune overlying clayey beds beneath. Supplies from this source are small and liable to seasonal fluctuation but the quality is good—usually less than 1,000 ppm. total solids.
A distinct soil profile has developed on the older dunes. The A—horizon is light grey in colour with an accumulation of organic matter on the top few inches. The B—horizon consists of a brown layer with iron oxides and organic matter under which is found a reddish-yellow clayey sand. The parent material is yellow sand.
There is no distinct profile on the younger coastal dunes, only a slight accumulation of organic matter in the surface layer. The sand is light grey with a pinkish tinge, and is finer than the sand of the older dunes.
The dune sands carry a tree cover of Eucalyptus and Banksia, with a tall-shrub layer mainly composed of Leptospermum, and a low-shrub and herb layer with a great variety of plants.
Some pastures have been developed on the sands to carry dairy cattle and sheep. They also support a developing market garden industry.
(e) Deltaic Sands (Qe). In the north-east of the area, in the vicinity of
Cardinia, are several smoothly-curving ridges of coarse sand projecting southwards from a more continuous sheet of similar sand to the north. The sand is thought to have been deposited by streams flowing from the highlands in the north, in a northwards extension of Western Port Bay. The sand is coarse, consisting mainly of rounded quartz grains, but with some felspar and occasional small fragments of granitic rock.
The sand ridges project from a few feet to about 20 feet above the surrounding carbonaceous swamp deposits and appear to rest on grey mottled sandy clays.
It is not known whether water is being drawn from these sands but it is possible that they contain limited supplies near the base of the ridges or beneath the swamp deposits, where they are buried.
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These ridges, because of their elevation, have been selected as sites for settlement, e.g., at Cardinia, as well as individual farm houses.
Pastures, mainly carrying dairy cattle and sheep, have been established on the sandy soils.
The sand at Cardinia is washed and used for cement tiles and general building purposes.
B. Sands and Clays of ?Pliocene Age (?P).
Deposits of mottled yellow and orange clayey sands and sandy clays with occasional lenses of grey clay are exposed in cliffs along Rutherford Inlet, in several small outcrops to the north and south, and in the main contour drain near Blind Bight.
These beds have been penetrated by bores (Nos. 17-18, parish of Sherwood), some of the lower beds being carbonaceous and resting on dark fossiliferous marine sandy silts. The upper surface of the beds is undulating and unconformably overlain by Quaternary sand dunes.
It is possible that several bores are drawing water from this formation (e.g., P113, P115, P119), but it is not certain. Water struck at 31 feet in bore 18 at Warneet contained 13,480 ppm. total solids, this high figure probably being due to infiltration of sea water.
C. Upper Tertiary Marine Sands (UT).
Fossiliferous sands and silty sands of Upper Tertiary age have been encountered in a number of bores in the area. The fauna has not been examined in detail but preliminary examination suggests an Upper Miocene or Lower Pliocene age.
These sands are overlain by the ?Pliocene beds described in the preceding section, but drilling has shown no distinct break between the two series, the division being made on the presence or absence of fossils.
The fossiliferous sands which have been encountered in Mines Department bores 17, 18 and 19, and fossiliferous sands in P93, parish of Sherwood, may belong to the same formation. The sands overlie foraminiferal limestone of Miocene age in bore P93.
The only bore known to be drawing water from these sands exclusively is Mines Department bore 19 at Warneet. Two analyses of water from different depth ranges gave 6,110 ppm. and 5,520 ppm. total solids (see appendix 2).
D. Miocene Ferruginous Sandstone (M). Miocene ferruginous sediments occur in a belt
extending from Clyde in the north of the area, through Devon Meadows to the south-west corner
of the parish of Sherwood. The outcrops flank the Silurian rocks in the western part of the area, although very thin remnants occur within the area of the main Silurian outcrop.
The best exposure of these rocks is found in the railway cutting at Clyde. There they may be seen to consist of ferruginous red, brown and yellow fine-grained gravels and conglomerates, sandstones, clayey sandstones and sandy clays. The more clayey rocks are generally mottled. At Five Ways, about a mile north of Devon Meadows, mottled sandy clays and clayey sands are exposed in a pit, while similar beds are to be seen in road cuttings on the Five Ways—Clyde-road.
This formation is continuous with the Baxter Sandstone to the west and is probably equivalent to the Brighton Sandstone of the Melbourne area.
The water obtained from these beds is of good quality, being suitable for irrigation, particularly on the well-drained sandy soils derived from this formation or the younger sandy deposits overlying it. Analyses range from about 300 ppm. to 1,340 ppm. total solids.
The water is used for irrigation of market gardens, for household purposes and stock.
The soils formed on these rocks are sandy podzols with a eucalypt and tea-tree cover. Most of this country has now been cleared and i_astures or market gardens have been established.
E. Miocene Marine Sands and Limestones (Mm).
Miocene shelly sands and limestones containing abundant foraminifera, bryozoa and mollusca underlie the whole area east of Five Ways.
In general, the quality of the water in these beds improves towards the south-east and varies from just over 3,000 ppm. in the north and west to about 1,100 ppm. in the south-east.
Yields up to 7,000 g.p.h. have been reported but they are exceptional—the usual is about 1,000-2,000 g.p.h.
The better quality water is used for irrigation of vegetables and lucerne and in every case the water is used for stock.
F. Lower Tertiary Volcanics (LT).
At the surface Lower Tertiary Volcanics extend from Cranbourne to just over the northern boundary of the parish of Sherwood, about 1+ miles west of Clyde. No rock outcrops occur, but in railway cuttings near Cranbourne black soils derived from basalt, and some weathering cotes of basalt, may be seen.
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Grey and white basaltic clay is exposed beneath ferruginous sandstones in the Clyde railway cutting. At Clyde a well (P148, 42 feet deep) finished in decomposed basalt, and a bore (P146, 80 feet deep) probably reached basalt. Mines Department bore 4, Sherwood, encountered hard basalt at 74 feet.
Basalt has also been recorded from bore P23 in Koo-Wee-Rup and P2 and P3 in Sherwood. It therefore appears that the volcanics underlie the whole of the eastern two-thirds of the area.
The analyses of water from P146 and P148 show 2,700 ppm. and 3,770 ppm. total solids respectively. In both cases it is possible that the water is a mixture of that from the basalt with that from the overlying ferruginous sandstones. The water from P146 is used for poultry and that from P148 for dairy cattle.
G. Silurian Rocks (S).
The Silurian rocks consist of shales, micaceous siltstones and fine-grained micaceous sandstones. They occur in the western part of the parish of Sherwood, and outcrop to about two miles east of the western boundary of the parish. These rocks have been encountered in bores in a fringe which extends up to two miles in width around the outcrop.
The soils developed on the Silurian rocks are podzols, usually grey silty loams with yellow to red mottled B horizons. Most of the Silurian area " has been cleared and on it pastures have been established, the main agricultural pursuits there being dairying, beef cattle and sheep.
Only small supplies of water have been obtained from these rocks. The depths of bores vary from 60 to 160 feet and it is probable that most of the water occurs near the base of the weathered zone just above the fresh rock.
Water analyses vary from 4,300 ppm. to 7,580 ppm. total solids. In all cases the water is used for cattle and/or sheep. In several cases the water (e.g., one with 7,580 ppm.) was found to have a deleterious effect on fowls.
4. Conclusions.
(a) Water suitable for stock can be readily obtained at shallow depths over the whole area. In a few cases, water from the Silurian rocks was found to be unsuitable for fowls.
(b) Water suitable for irrigation has been obtained from Tertiary sandstones in the Five Ways—Clyde—Cranbourne area. Here however, numerous bores are being put down close together and there is therefore a danger of over-pumping.
Irrigation water has also been obtained from Tertiary marine beds between Tooradin and Dalmore. The quality and quantity of this water improves towards the east and south-east.
(c) There are other minor occurrences of good quality water such as soaks at the base of sand dunes and sand lenses in beds overlying the marine formations.
(d) More use could be made of underground water for irrigation in the eastern part of the area but the possibilities west of Tooradin are very limited.
(e) There is a serious lack of information about the majority of bores and one only has been drilled deep enough to determine the complete sequence in the Tooradin—Dalmore—Cardinia area.
(f) The determination of the underground water potentialities of the area with certainty depends upon information from further drilling. Bores drilled to bedrock at Dalmore and Cardinia would therefore be of considerable assistance in this regard and should provide a reliable guide to the stratigraphy and structure of the area. The average depth of the bores would probably be about 250 feet. Further bore sites could then be selected to fill in the detail where required.
5. References.
GOUDIE, A. G., 1942, Soil and Land Utilization Survey of the Parishes of Koo-Wee-Rup and Koo-Wee-Rup East. Proc. Roy. Soc. Vic. n.s. 54 (1), pp. 93-130.
HILLS, E. S., 1942, The Physiography of the Koo-Wee-Rup Swamp. Proc. Roy. Soc. Vic. n.s. 54 (1), pp. 79-91.
PATTON, R. T., 1942, Ecological Studies in Victoria—Part VI.—Salt Marsh. Proc. Roy. Soc. Vic. n.s. 54 (1), pp. 131-144.
Position : Cranbourne M.S.438895, Great Swamp P.R.
Depth Struck. Strata. Thickness.
Qc {Black clay Grey clay
'Yellow clay .. ?P Yellow sandy clay
Coarse sand ..
ft. in. ft. in.
0 0 15 0
15 0 10 0
25 0 20 0
45 0 2 0
47 0 3 0
Depth drilled . . 50 0
Water struck at 47 feet. Standing at 3 feet.
APPENDIX 3—BORE LOGS. PARISH OF KOO-WEE-RUP—continued.
BORE P22
Position : Cranbourne M.S.451934, Allotment 25
Surface Level : 10
PARISH OF KOO-WEE-RUP
PRELIMINARY REPORT ON BORE NO. 4.
Situation : In the public purposes reserve, Tooradin ; from the westernmost corner of allotment 5, parish of Koo-wee-rup, 87 feet on a bearing of 121' then 74 feet on a bearing of 211°.
Surface Level : 2 feet
Summary of Log : Feet
Sands and clays
0- 70 Black sand
70-128 Fine grey sand .. 128-177 Grey sand with shells