PROGRAMM ".. I ABSTRACTS

for t he

ELEVENTH SYMPO~:UM

'ADVANCES IN THE STUDY OF THE SYDNE'! B',SlN"

DEPARTMENT OF GEOLOGY THE U"IVERSITY OF NEWCASTI E­ N.S.W 2308 THE UNIVERSITY OF NEWCASTLE

IEPARlMENT OF GEQl(XjY

• PROGRAMME AND ABSTRACTS FOR 1HE ELEVENTH SYMPOSIUM ON

"ADVANCES IN THE STUDY OF THE SYDNEY BASIN"

6 TO 9 MAY 1977

Convener: Dr K.H.R. Moelle Department of Geology The University of Newcastle 559.4405 Advances in the study of the Sydney Basin; abstracts of the symposia: (annual) 1st symposium 1966 to

4th symposium 1969. Newcastle, University of

Newcastle, Department of Geology. Published as one volume with individual title pages. From 5th symposium 1970 title changed to Advances in

the study of the Sydney Basin; programme and

abstracts, which see also.

Geology - N.S.W. - Congresses University of Newcastle - Department of Geology Symposium on Advances in the study of the Sydney Basin, University of Newcastle (s) 559.4405 Advances in the study of the Sydney Basin; programme and abstracts of the symposia: (annual) 5th symposium 1970 to date. Newcastle, University of Newcastle, Department of Geology. Previously known as Advances in the study of the Sydney Basin; abstracts of the symposia, which see also.

Geology - N.S.W. - Congresses University of Newcastle - Department of Geology Symposium on Advances in the study of the Sydney Basin. University of Newcastle (s)

1 FOREWORD

! Welcome to the Eleventh Newcastle Symposium!

Because of the International Geological Congress

in 1976 it was decided not to hold a Symposium that year

hence two years have elapsed since the Tenth Symposium.

In spite of this, the interest in the Sydney Basin has

not waned and a number of people have offered to present

papers which form the major part of the programme .

The diversity of the topics of the papers is note-

worthy, and indicates the value of the Symposium as an

important medium of communication.

The staff and I hope that you will enjoy the

Symposium sufficiently to want to return for the Twelfth

in 1978.

BERYL NASHAR

Head of Department •

2 PREFACE

The programme and abstract volume of the TENTH

NEWCASTLE SYMPOSIUM contains an author and locality index for the first ten Symposia. The next index will appear in the volume of the Thirteenth Symposium.

Seventeen papers will be presented this year; this high number necessitates the holding of two concurrent sessions on Sunday morning. The papers have been divided into three groups.

1. Papers of regional and economic significance.

2. Papers dealing with mining and geophysical aspects. and 3. Papers of stratigraphic and environmental importance.

I would be most grateful for any comments and suggestions from registrants.

KONRAD H.R. MOELLE

Convener

3 PROGRAMME HOURS • FRIDAY, 6 MAY 1977

• REGISTRATION in the foyer of 0900-1700 The Geology Department The University of Newcastle EXCURSION: Visits to outcrops of the 1330-1700 Merewether Conglomerate in the Newcastle area and an underground inspection of B.H.P. Burwood Colliery

Co-ordinators: Dr K.H.R. Moelle Mr P. Warbrooke Mr R. Williams INFORMAL GATHERING in the after 2000 Newcastle Rugby Club 45 Newcomen Street Newcastle

SATURDAY, 7 MAY 1977

REGISTRATION in the foyer of 0800-0900 The Geology Department

totJRNlf"ll TEotiICAL SESSIONS Geology/Physics Lecture Theatre EOl (beside the Geology Department) The University of Newcastle

Chairman: Dr N. L. MARKHAM Director Geological Survey of N.S.W. OPENING OF 11th NEWCASTLE SYMPOSIUM 0900-0905 Professor A.D. TWEEDIE Deputy Vice Chancellor The University of Newcastle

4 HOURS 1. ENVIRONMENTAL ASPECTS OF TRACE ELEMENTS 0905-0940 IN SYONEY BASIN COALS D.J. SWAINE . C.S.I.R.O. Division of Mineralogy

2. THE MINING AND COMMERCIAL GEOLOGY OF 0490-1015 THE J.A.B.A.S. WARKWORTH AREA

B.~. VITNELL and P.P. WOOTTON Coal &Allied Industries Limited

3. LESSER KNOWN COAL OCCURRENCES IN 1015-1050 NEW SOUTH WALES

J. Sl1P.\iZ

Geological Survey of New South Wales, ~.S.~. Department of Mines

Ucpr;:;'Y-2 Tea in GeoZogy Department 1050-1125

4. STRUCTURAL AND TECTONIC FRAMEWORK OF THE 1125-1200 N.S.W. PORTION OF THE SYDNEY-BOWEN BASIN

J.~. BROWNLOW Geological Survey of New South Wales, ~ . 5 . Ii. Department of Mines

KEYNOTE ADDRESS 1200-1245 W.M.R. EWAN Executive Director COSTAIN AUSTRALIA LIMITED

SUI+1ARY AND VOTE OF THANKS BY CHAIRMAN 1245-1250

i.unch ::~ University Union 1300-1430

5 AF1ER~ lEOflICAL SESSIOOS Geology/Physics Lecture Theatre EOI The University of Newcastle , Chairman: MrG.HARMAN Superintending Coal Geologist The Broken Hill Pty Co. Ltd , HOURS 5. A GEOPHYSICAL STUDY OF THE NORTH-EASTERN 1430-1505 PART OF THE SYDNEY BASIN A.M. NALAYE and I.E. QURESHI University of New South Wales

6. THE STORY OF PERMIAN AND TRIASSIC 1505-1540 VEGETATION IN THE SYDNEY REGION G. RETALLACK University of New England 1540-1615 Afternoon Tea in the Geo~ogy Department

7. MAJOR IGNEOUS INTRUSIONS IN THE 1615-1650 DENDROBIUM AREA OF THE SOUTHERN COALFIELD OF NEW SOUTH WALES S. GYE, J. DOYLE and H. READ Australian Iron &Steel Pty Ltd

a. SEISMIC RISK ANALYSIS OF THE LUCAS HEIGHTS 1650-1725 AREA LA. MUMME , Australian Atomic Energy Commission

SUMMARY AND VOTE OF THANKS BY CHAIRMAN 1725-1730 In END OF SESSION

Sherry followed by Symposium Dinner in 1900 for UNIVERSITY UNION 1930

6 HOURS SUNDAY, 8 MAY 1977

Two concurrent technical sessions will be held.

TEOiNlCAL SESSlOO I Chairman: Professor B. NASHAR The University of Newcastle

9. SEDIMENTS OF CAONOZOIC AGE IN THE 1000-1035 PENRITH-WINDSOR AREA

V. GOBERT Geological Survey of New South Wales, N.S.W. Department of Mines

10. USE OF A VALLEY IN HAWKESBURY SANDSTONE 1035-1105 FOR DISPOSAL OF HOUSEHOLD WASTE K.Y. CHAN, B.G. DAVEY and H.R. GEERING University of Sydney

Morning Tea in the Geology Department 1105-1135

11. MODEL OF SAND DEPOSITION IN NEWCASTLE BIGHT 1135-1210 C.K. LY Public Works Department, N.S.W.

12. STRATIGRAPHIC SUBDIVISION OF THE EARLY 1210-1245 PERMIAN COAL MEASURES IN THE BOGGABRI AREA AND REGIONAL IMPLICATIONS

J . W. BROWNLOW Geological Survey of New South Wales, N.S.W. Department of Mines

SUMMARY AND VOTE OF THANKS BY CHAIRMAN 1245-1255 END OF SESSION 7 lEOtHCAL SESSION II Chairmen: Mr E. DAVIES, Peko-Wallsend Ltd Mr B.W. VITNELL, Coal &Allied Industries Ltd

13. FAULTS IN THE HAWKESBURY SANDSTONE 1000-1035

D. F. BRANAGAN University of Sydney

14. GEOPHYSICAL STUDIES IN THE 1035-1105 DUNGOG-GLOUCESTER REGION AND THEIR GEOLOGICAL SIGNIFICANCE A. KUMAR and I.R. QURESHI University of New South Wales

Morning Tea 1105-1135

15. INVESTIGATIONS INTO THE POINT LOADING 1135-1200 TECHNIQUE FOR DETERMINING WEAKNESS DIRECTIONS IN COAL SEAM ROOF STRATA W.A. WILLIAMS Australian Iron &Steel Pty Ltd

16. STRUCTURAL ANALYSES AT STOCKTON BOREHOLE 1200-1235 COLLIERY AND THE APPLICATIONS TO MINING OPERATIONS R.J. WILLIAMS The Broken Hill Proprietary Co. Ltd

17. ON THE SEDIMENTARY DYKES IN THE ABERDARE 1235-1310 EAST COLLIERY HOLDING C.D. RAWLINGS and K.H.R. MOELLE University of Newcastle SUMMARY AND VOTE OF THANKS BY CHAIRMAN 1310-1315 END OF SESS ION FAREWELL LUNCHEON - UNIVERUTr UNION 1315-1430

8 ENVIRONMENTAL ASPECTS OF TRACE ELEMENTS IN SYDNEY BASIN COALS D.J. Swaine CSIRO Division of Mineralogy There are several aspects of coal-winning and coal-usage in which a movement of trace elements may occur. Examples include open-cut mining, coke-making and combustion, especial 1: using pulverised coal. This paper will concentrate on the fate of several elements during the large-scale combustion of coal for electricity generation. Comparisons of mean values for trace elements in N.S.W. bituminous coals with those for shales and the continental crust show that (a) contents in N.S.W. coal are almost always less than those in shales, and (b) contents in the coals are less than, about the same, or more than those in the crust. During the combustion of pulverised coal, elements associated with the coaly matter are set free and those associated with the mineral matter may be set free or change their mineral form. The reactions are complex, but there is a distribution of most elements between bottom ash, fly ash and the gas phase. Several elements are at about the same levels in coal ash and in fly ash, and some volatile elements, such as selenium are adsorbed on fly ash particles. In any consideration of trace elements reaching the atmosphere in stack gases and ultimately being returned to the earth in rain, the effects must be seen in relation to natural background levels in rocks and soils. In view of the dual role of many elements, namely essentiality and possible toxicity, it must be noted that some elements dispersed in stack gases may have beneficial biological effects.

THE COMMERCIAL AND MINING GEOLOGY OF THE J.A.B.A.S. WARKWORTH EXPLORATION AREA B.W. Vitnell and P.P. Wootton Coal &Allied Industries Limited Following the grant of an Authorisation to the Company in 1974 exploration by drilling commenced in May of that year, over an area of 4680 hectares. To date about 300 NM and NM/LC size cored boreholes have been sunk from the surface within this area and a subsequent 2S per cent extension northwards beyond the floodplain of the Hunter River, 9 (a) to the Bayswater Seam on 1.6km gridsj (b) to the last commercial coal above the Bayswater on 0.8km gridsj and

(c) to selected horizons in the northern, central and • south-western sub-areas on 300m grids.

Fully comprehensive laboratory testing of (a) and (b) • was carried out with strip sample restricted testing of (c) . This work is now almost complete and the exploration will allow the upgrading of any part of the area to an operat­ ional stage with open-hole drilling to delineate limits of weathering near outcrops and/or geophysical methods to further define faulting and igneous intrusion. A complete suite of fifteen locally named outcropping seams from the Whybrow (below the Denman Formation of the Wittingham Group of the Upper Permian) to the Vaux contain commercially workable subsections from 1m thickness upwards. Based upon working sections delineated in these seams a Total Indicated Reserve of 850 million tonnes of coal is available. All these coals are medium to high volatile, low sulphur, soft coking coals. It is not anticipated that the Company will be granted title to work the Bayswater Seam, a steaming coal. Computerisation of data generated by this extensive drilling programme has enabled studies of coal seams and inter­ seam sediments to be undertaken. Gomputer plotted plans and sections demonstrate sedimentary variations and coal seam development and their relationship with structural features. A very strong directional control of seam splitting and development of sedimentary wedges is exhibited. A similar directional effect exists in changes in coal type.

A depositional model of the interval from the Mt Arthur to the Vaux Seam indicating a possible localised basin config­ uration is presented. These studies tend to indicate that better stratigraphic and mining correlations in the Warkworth Area are achieved by using working sections of coal units rather than "coal member" units.

Such an approach provides better definition of sediment­ ary variations, a most important factor in appraising mining feasibility both for open-cut and underground operations.

10 T~E LESSER KNOWN COAL DEPOSITS IN NEW SOlITH WALES

J. Stunt~ Geological Survey of N.S.W. Department of Mines

Black coals ranging from Carboniferous to Cretaceous age and brown·coals of Tertiary age occur at various local­ ities throughout the State. Knowledge of·these coal deposits is at different levels; the readily marketable "Upper" and "Lower" Permian coal measures of the Sydney Basin being the most thoroughly explored. This paper summarises information accumulated over recent years on the other, less well known, deposits. It briefly describes certain Carboniferous, Permian and Triassic coals of the Sydney Basin and environs, the· · Permian coals of the Oaklands Basin, the Tertiary coals of the Murray Basin, the Permian coals of the Gunnedah Basin, the Jurassic and Cretaceous coals of the Great AUstralian Basin, and the Jurrasic and Triassic coals of the Clarence­ Moreton Basin. It is concluded from this State-wide examination that the Sydney Basin will continue as the main coal producing area for many years. However, other such areas are likely to develop in the course of time, particularly in the Oaklands and Gunnedah Basins.

(PubZished UJith the permission of the Under Secretary, N.S.W. Department of Mines.)

11 STRUCTURAL AND TECTONIC FRAMEWORK OF THE N.S.W. PORTION OF THE SYDNEY-BOWEN BASIN J.W. Brownlow Geological Survey of N.S.W. Department of Mines The N.S.W. portion of the Sydney-Bowen Basin is a Permo-Triassic structural basin overlying a pre-Permian base· ment which is characterised by complex morphology and litho­ logical distribution. Preliminary regional fracture fabric analysis suggests that fracture zones (lineaments) are partl~ responsible for this complexity and have also influenced basin development. A model of the structural framework is presented. Using this interpretation and a theoretical tectonic model (currently in preparation), the tectonic development of the basin is briefly discussed. STRUC1URAL FRAMEWORK A WNW trend is shared by the Lachlan River Lineament, and the Denman-Raymond Terrace Lineament (parallel to the Hunter River). The· first separates areas (north and south of Sydney) of fundamentally different tectonics in the Permian and Late Carboniferous. The second marks the southern boundary of the New England Fold Belt and may have acted (in part) as a sinistral strike slip fault during thrust movement on the Hunter-Mooki Fault System. NE trending fractures, roughly parallel to the Darling River Lineament* (north of the Liverpool Range) and the Pyramul Creek Lineament* (south of the Liverpool Range) appear to greatly influence basement morphology and sediment thickness, but not tectonics. One such feature near Narrabri appears to cause a stepwise discontinuity in the basic axis. TECTONIC FRAMEWORK A composite stratigraphic column from the Gunnedah area plotted against the palynological time scale is analyse( in order to identify major stratigraphic, provenance; deform­ ational, palaeogeographic and volcanic events. These event! (with minor qualifications) appear typical of the basin from Sydney to Narribri. Using a theoretical tectonic model to interpret these data and similar information from the fold belts, three sequences of tectonic events are recognised, each .initiated by high heat flow and high pore water pressurl These intervals are Late Carboniferous to the end of Stage 3 (Early Permian), Stages 4 and 5, and latest Permian to earliest Triassic. ( * after E. Scheibner) (Published with the permission of the Un.d.el' Sea1'etal'y~ N.S.W. Depal'tment of Mines.)

12 A GEOPHYSICAL STUDY OF THE NORTH~EASTERN PART OF THE SYDNEY BASIN A.M. Nalaye and I.R. Qureshi School of Applied Geology University of New South Wales A gravity and magnetic survey was carried out in the north-eastern part of the Sydney Basin and the adjoining area of the New England Fold Belt. The area covers completely the Lochinvar Anticline and the neighbouring structures. Measurements were made along several traverses at an average spacing of 1.5km; a total of 265 stations wer established giving an average density of about 1 station/ l4km2 • Elevations were determined from bench mark and barometers. Terrain corrected Bouguer anomalies were obtained with an overall accuracy of about 0.2 mgal. The density determinations were made by measuring some 80 rock specimens and an analysis of Bouguer anomalies. " The mQst prominent feature of the Bouguer anomaly map is the pr~sence of a wide belt of gradient which trends NNE and overlies the Loc:hinvar Anticline. On approach to the PerIllO-Carboniferous bounda-ry, the belt turns eastwards. The two sections of the belt flank a gravity high that forms its axis in the Kurri Kurri-Maitland district. Among the less defined features of the map are the gravity lows over the Macquarie Syncline and at Singleton. The eastward and the southward increases in gravity along the two sections of the belt of gradient appear to be partly related with the Lochinvar anticline along the axis 0 : which the Carboniferous rocks locally crop out. This is in accord with the inference that the Carboniferous rocks are denser than the Permian rocks and also with the seismic results. The increases also have a regional significan~e a: the belt of gradient joins up with the Wollondilly-Blue Mountains gradient zone to the south and the coastal gradien' zone to the north-east.

13 THE STORY OF PERMIAN AND TRIASSIC VEGETATION IN THE SYDNEY REGION Greg Retallack The University of New England l The well-preserved succession of megafossil floras in the Sydney Basin illustrates slow colonisation of vast peri­ glacial wastes during the Permian followed by a Triassic diversification of plant communities into different micro­ climates and soils.

The first vascular plant life to straggl~ into the latest Carboniferous glacial outwash was a low-growing tundra vegetation, dominated by Botychiopsis. This impoverished pteridosperm flora was a remnant of diverse pre-glacial pteridosperm forests. As climate improved and the sea rose to cover most of the Sydney Basin, the polar tree line, largely of GangamopteriB plants, penetrated southward along less-frigid seashores. As permafrost conditions abated later in the Early Permian, aquatically adapted roots (Vertebraria) could grow in waterlogged soils without their large aerenchyma chambers being disrupted by frost heave. By Late Permian times, plants with such roots formed widespread swamp forests and their leaves (GZossopteris) accumulated in autumnal banks. Conifers (WaZkomieZZaJ forested drier inland areas. ~ese swams were drained by uplift, following which, conifers (VoZtziopsis) came to forest extensive flood­ plains. A distinctive pteridosperm, "ThinnfeZdia" canip­ teroides grew along these latest Permian streamsides. Few remains, largely of conifers, have been found in Early Triassic volcanogenic sandstones and claystones. By the middle Early Triassic, broadleaf heath and forests, largely of Dicroidium zuberi. became widely established on quartzose alluvium from the north and west. The lycopod, PZeta'Omeia ZongicauUs formed thickets around lagoonal margins at this time. By the Middle Triassic, the near-coastal eastern Sydney Basin was overgrown with the cycadophyte, Taeniopteris ZentriauZiformis. Soon after, the water table had stabilised to such an extent that braided streams had resorted their alluvium to very pure quartz sand. This nutrient and water deficient floodplain encouraged the development of xerophytic pteridosperms (XyZopteris). Later in the Middle Triassic, clayey floodplains were again colonised by cool temperate broadleaf floras, this time dominated by Dicroidium odontopteroides.

14 IGNEOUS INTRUSIONS IN THE DENDROBIUM AREA OF THE SOUTHERN COALFIELD OF NEW SOUTH WALES S.J. Gye, J.F. Doyle and H.W. Read Australian Iron &Steel Pty Ltd Australian Iron &Steel Pty Ltd's Dendrobium explor­ ation area is some 15km west of Wollongong and immediately west of its operating Nebo, Kemira and Corrimal collieries. It covers an area of approximately 125km2 Recent drilling indicates that sills have destroyed the economic potential of the Wongawilli seam over the western quarter of the area and also in the southeast over a 5km2 area overlapping into Nebo Colliery. The Bulli seam has been affected along the western boundary and over appro~ imately I Okm2 in the middle of the area. The sills vary up to 41m thick (up to 120m thick abou 3km west of the area). The thin intrusions are generally highly altered and white in colour while the thicker intrusions tend to be less altered and light to dark green i colour. Sill-coal seam contacts are generally irregular an the contact zone is the most altered. Grain size varies generally from fine to medium, with some coar,e bands. Coal seams are generally favoured horizons for the intrusions, although intrusions are present within other formations of the Illawarra Coal Measures and the overlying Narrabeen Group. The effects of intrusions on the coal seams are highl variable. There are examples where an intrusion has merely displaced the seam and other examples where part or all of the seam has been consumed. Sills within or adjacent to coal seams generally cause cindering of the seam. However, there are examples where a thick sill has intruded immediately above the usual Wongawilli seam working section, resulting in the upper half of the section being cindered and the lower half becoming a semi-anthracite. The intrusions, in common with sills and dykes in the coalfield (apart from the Permian flows in southern parts) are thought to be Tertiary, post dating major faulting. The)' all appear to be differentiates of an alkali olivine basalt and examples of nephaline syenite, olivine dolerite, crinite and picrite have been identified, Edwards (1952), Moore (1975).

15 SEISMIC RISK ANALYSIS OF THE LUCAS HEIGHTS AREA I.A. Mumme Australian Atomic Energy Commission The purpose of this paper is to describe a quantitative analysis of the seismic threat (on Hawkesbury Sandstone) at Lucas Heights. This seismic risk analysis, based on a method derived by Cornell, was prepared as part of a much larger study to develop procedures to aid in setting up earthquake design provisions for buildings at the Research Establishment.

The outcome of this study is a plot of ground motion parameters (MM intensity, peak acceleration, velocity and displacement) versus average return period.

CAINOZOIC SEDIMENTS IN THE PENRITH-WINDSOR AREA * Val Gobert Geological Survey of N.S.W. Department of Mines Alluvial sediments ranging in age from Oligocene to Holocene were deposited in the Cumberland Basin between Penrith and Windsor. Westerly flowing rivers were inter­ mittently diverted into the developing Cumberland Basin, which was probably formed in response to the general collapse of the continental margin of New South Wales.

The oldest sediments are colluvial-alluvial deposits comprising angular fragements of shale, ~andstone, large silcrete boulders, and transported ironstone pebbles (St ~rys Fo~ation). These sediments appear to have been deposited by low gradient dendritic streams of a palaeo-South Creek system probably before significant collapse of the Cumberland Basin. In response to structural or other events during the Miocene, the Wollondilly and/or Cox's River system was temporarily diverted into the Cumberland Basin. As a result an extensive sheet of gravel and clay (Rickabys Creek Gravel and Londonderry Clay) was deposited. This gravel sheet subsequently subsided as the Cumberland Basin developed leaving erosional remnants on top of the Blue Mountains Plateau and down the face of the Lapstone Monocline.

16 During the early development of the Lapstone Monoclin (Pliocene) the Grose River, via several outlets through Lynchs and Mahons Creeks, eroded the Miocene allUVial terra and deposited the Clarendon Formation, a sandy formation which has undergone wind sorting to produce dunes. The Agn Banks and Pitt Town Sands are relict dunes which were probably deposited initially as fluvial deposits and subsequently resorted by westerly winds. Although the Nepean-Warragamba and the Wollondilly­ Cox's River systems are the present m~jor rivers flowing in this area, they were not present at the time the Clarendon Formation was dep9sited. but instead flowed west into the I. palaeo-Macquarie River. During the Pleistocene the Warragamba-Nepean River entrenched into the Blue MOuntains Plateau and deposited alluvial gravels and silts in a terrace eroded into and below the level of the '.rtiary terraces (Cranebrook and . Lowlands Formations). (.. Published lJJ'ith the permis.n.on of the Under' Seczoetary, N. s. w. DepaI'tment of Mines. )

USE OF A VALLEY IN tlAWKESSURY SANDSTONE FOR DISPOSAL OF MOUSEHOLD WASTES .

K.Y. Chan, B.G. Davey and H.R. Geering Department Of Soil Science University of Sydney The valley of Bare Creek at Belrose, a suburb of Sydney, now contains ab~t 20 million cubi c metreS of hous hold waste and produces a strongly polluting leachate. The leachate is collected an4 treated with Ca(Oh)2 and aerated prior to disposal by spray irrigation onto the landfill. Studies of the treated sOil in the field, as well as a laboratory column, show" that the pH increased from 4.2 to 9.1. Due to this pH iaAease the cation exchange capacity of Mg, Ca and Zn 'Was fouad to occur in the soil covering th, sanitary landfill. lb. laboratory studies showed that le~ than half of the Mg and C. stored was due to the increased cation exchange capacitlof the soil. The additional cations stored in the f~ld and in the laboratory column appear to be stored in specifically adsorbed forms. MODEL OF SAND DEPOSITION IN THE NEWCASTLE BIGHT Cheng K. Ly • Hydraulic Laboratory Public Works Department. N.S.W. Stratigraphic studies of the sand barriers in Newcastle Bight reveal that they are composed of transgress­ ive and regressive units and their modes of deposition appear to be similar. These sand barriers are termed Inner Barrier and Outer Barrier. The Inner Barrier is associated with the last interglacial transgression. Its transgressive unit is composed of a medium-grained, moderately sorted sand older than 140,000 years B.P. This sand overlies conformably the presumably pre-last interglacial deposits of estuarine clays, and fluvial sand and gravel. This transgressive unit is in turn overlain by the regressive unit of beach ridges, which is composed of a fine to medium sand. The sand is moderately to poorly sorted at the base and becomes better sorted at the top. The regressive unit is terminated by aeolian cap composed of a medium-grained, very well sorted sand. During the post glacial marine transgression (result­ ing from a world eustatic rise in sea level accompanying continental deglaciation), the shoreline progressively moved landward across the continental inner shelf, causing rework­ ing of pre-existing barrier sand. When the eustatic rise ceased at approximately the present sea level position about 6,000 years ago the transgression was balanced by sand deposition in the form of beach ridges along the coastline at times between 6,000 and 4,000 years ago and the prograd­ ation of coastline (i.e., regression) took place while the sea level was virtually stable. The transgressive unit of the Outer Barrier which is composed mainly of reworked material from the Inner Barrier is made up of fine to medium­ grained and moderately sorted sand. It overlies disconform­ ably either the Pleistocene sandy deposits of the Inner Barrier or thin layers of undifferentiated estuarine deposits. This transgressive unit is in turn overlain by the regressive unit of beach ridges, which is composed of a fine to medium­ grained and moderately (at the base) to well sorted (at the top) reworked sand. Due to full exposure of the Newcastle Bight embayment to the southerly and southeasterly wind actions, large transgressive dunes which are ininitiated from the beach supply have migrated downwind over swamps or forested surfaces. The dune sand is medium to fine-grained and very well sorted. 18 STRATIGRAPHIC SUBDIVISION OF THE EARLY PERMIAN COAL MEASURES IN THE BOGGABRI AREA AND REGIONAL IMPLICATIONS J.W. Brownlow Geological Survey of N.S.W. Department of Mines Loughnan (1973, 1975) recognised detrital flint clay (pelletal kaolinite clayrock) in the Early Permian coal measures over a large area from the Muswellbrook Anticline t the Boggabri area. Recent Departmental and company drillin has extended the area of known occurrence of this lithology, particularly north of Boggabri. The present study is based on original mapping of Gunnedah and Maules Creek, and core logging from the Maules Creek area (north east of Boggabri), as well as reinterpret­ ation of recent Departmental and company drilling from the Boggabri-Gunnedah region. Two petrologically distinct, Early Permian (Lower Stage 4) sequences are recognised in outcrop and core eas~ f Boggabri, between the Boggabri Ridge (Brownlow. 1977) and t~ Nooki Fault System. These are the "Leard Formation" (the lower unit) and the "Naudewan Formation" (the upper unit) (formerly Naudewan Group of Hanlon, 1950). The "Leard FOTlnation" consists of pelletal clayrock conglomerates and sandstones, carbonaceous in p~t and commonly with one or more coal seams at or near the top of the formation. The clasts are well rounded to highly angular clay pellets commonly with well preserved relict volcanic (particularly acid volcanic) textures. The unit varies in thickness up to 8.5m.

The "Nandewan Formation" consists of interbedded lith: conglomerates, sandstones, siltstone, claystone and coal. Conglomerate and coarse sandstone form about 50 per cent of the formation, and coal about 10 per cent of the formation. The clasts are predominantly fresh to slightly altered fragments of acid volcanics. These formations are distinguished by the distinctive petrology of their clasts. The work of Loughnan (1973, 1975) is revised and .~,ended, in order to distinguish correlations of ~hese two ~'ts along the eastern margin of the Gunnedah Basin. (PubZished with the permission of the Under Secretary: N.S.W. Department of Mines.)

19 FAULTS IN THE HAWKESBURY SANDSTONE D.F. Branagan Department of Geology &Geophysics University of-Sydney Shear zones in the Hawkesbury Sandstone have been recognised at a number of localities in the Sydney region, particularly on the Woronora Plateau. Rock in these zones, up to 10m wide, has been consider­ ably fractured and'is heavily iron-stained. Orientation of the shears is essentially vertical. Linear extent of the shears and consistency of trend is presently being investigated. There appears to be little or no displacement (vertical or horizontal) associated with the shearing. The shear zones are problem areas for engineers. The rock has much lower bearing capacity than "normal" sandstone, it is more easily eroded and requires support in all but the smallest cuttings. The relation (if any) between these shears and other faulting previously recognised in the Hawkesbury Sandstone (Branagan, 1969) has yet to be established. Both types appear to be concentrated in the region of major flexures and are possibly more common parallel to a north-south joint direction. I suspect also that they will prove to be concentrated close to the present coastline. The shears may be the result of a shear component of the tensional forces active on the east Australian coast during early Tertiary. Shears in the Newcastle Coal Measures (Blayden, 1969) may have a similar origin. References Blayden, 1.0., 1969, Jointing in the Newcastle Coal Measures of the MacQuarie Advances in the Study of the Sydney Basin, 3rd SympOSium (Sympos Abstracts 1-4, pp.43-44) Branagan, D.F., 1969, Engineering Geology of the Sydney Region Contracting and Construction Engineering (May, June and June 1969).

20 GEOPHYSICAL STUDIES IN THE DUNGOG-GLOUCESTER REGION AND THEIR GEOLOGICAL SIGNIFICANCE Aksheya Kumar and I.R. Qureshi School of Applied Geology University of New South Wales A gravity and magnetic survey was conducted covering the Permian rocks of the Gloucester Syncline and the surrOUI ing Carboniferous rocks in the southern part of the New England Fold Belt, north-east of the Sydney Basin. Over 51 stations were established giving an average density of 1 station/lOkm2 . Elevations were determined using micro­ barometers, a base barograph and available bench marks. Appropriate reductions including terrain corrections were applied to the observed data in order to obtain Bouguer anomalies with an accuracy of about 0.3 mgal. Rock dens it were estimated from some 200 specimens and an analysis of Bouguer anomalies.

The Bouguer· anomaly map shows three major features. prominent gravity low of about 15 mgal lies over the Gloucester syncline and a high, named the Wangat Gravity Hi of about 11 mgal in the area to the west. The two feature run north-south and are separated in the north but joined i the south. The third feature is a regional gradient which assumes prominence in the eastern part of the area. The regional gradient can be explained by a model showing crustal thinning under the coastal region and a tra ition to oceanic type crust further east. A quantitative interpretation of residual anomalies i carried out using several new computer-aided techniques tha provide the position, shape and density contrast of a causative source. The anomalies over the Gloucester syncline account fo thickness of about 2km of Permian rocks and a deeper and broader source possibly formed by the down folding or down­ throing of the underlying Carboniferous rocks. The Wangat Gravity High is probably caused by a large igneous intrusion about 3km in thickness. This interpreta is supported by the magnetic anomalies and by the general c cordance of the prehnite-pumpellyite zone of low grade metamorphism with the gravity high. The metamorphism is believed to be due to a subsurface heat source (Offler and Diessel, 1976).

21 The north-sound trend of the major anomalies is identical to the trends of several prominent gravity features within the Sydney Basin, in particular the gravity high which runs along its axis (Qureshi, 1975) .

• References

Offler, R. and Diessel, C.F.K., 1976. The Application of Reflectance Determinations on Coalified and Graphitized Plant Fragments to Metamorphic Studies. J. geo!. Soc. Aust., 23, pp.293-297.

Qureshi, I.R., 1975. The Crust Beneath the Sydney Basin. Abstr. 10th Newcastle Symposium, pp.lO-ll.

INVESTIGATIONS INTO THE POINT LOADING TECHNIQUE FOR DETERMINING WEAKNESS DIRECTIONS IN COAL SEAM ROOF STRATA W. A. Wi 11 i ams Australian Iron &Steel Pty Ltd The technique of axial point loading of core discs is well established and the procedure is very simple. Induced tensile fracturing will be random in a sandstone with an isotropic homogeneous fabric but will show a preferred trend if a weakness direction exists in the fabric.

In order to investigate causal relationships, preferred directions of point load fractures have been compared with macro-scale discontinuities, clastic grain elongation and/or inferred directions of lateral stress, at several localities in the Southern Coalfield. Oriented sandstone has been obtained from exploration bore holes and coal seam roof strata in mine entries. Preliminary results are encouraging and it is hoped that relationships will become established that will aid structural analysis and strata control techniques during mine planning and development. Of particular significance would be a reliable correlation between point load fracture directions and lateral tectonic stress directions (as generally suggested in published literature), in view of the costly and frequently unreliable methods of measuring in situ stress which are employed at present.

22 STRUCTURAL ANALYSES AT STOCKTON BOREHOLE COLLIERY AND THEIR APPLICATION TO MINING OPERATIONS

R.J. Williams The Broken Hill Proprietary Co. ltd Geometric, kinematic and kinetic analyses of diastrophic structures have been undertaken at Stockton Borehole Colliery and applied to mining operations. Coal is mined from the Young Wallsend seam where the basal 2.4m is extracted leaving 0.6m of coal as a roof. Overlying the seam is the Nobby's Tuff which maintains a very uniform thickness of l.·Sm over the colliery holding.

Mining conditions are generally poor. This is funda­ mentally due to the incompetent nature of the "roof coal" and of the Nobby's Tuff. However, quite significant diff~rences in mining conditions occur and these can be related, for the most part, to structural phenomena.

A study of the interrelationships between the diastrophic structures has revealed three pha$es of deform­ ation. Deformation Phase I involved the formation of an east west striking cleat set and the intrusion of a simila~ly oriented dyke under a stress.field !n which Sigma I was vertical and Sigma 2 horizontal and orieRted in an east·west direction. The formation of the dominant structural aniso­ tropies took place during Deformation Phase II. This resulted in the formation of north west-south east striking cleats, joints, dykes and normal faults under a stress field in which Sigma 1 was vertical and Sigma 2 horizontal and oriented at 140°. Deformation Phase III involved a re­ orientation of the stress ellipsoid with Sigma I horizontal and oriented approximately east-west, and Sigma 3 vertical. Low angle reverse faulting and low angle shear joints (confined to the Nobby's Tuff) were developed during this phase of deformation. Detailed mapping of mining conditions was undertaken. A distinct failure pattern emerged and this was analysed with regard to both geological and mining parameters. Zones of varying -ining conditions were delineated and good correlatioT exists between these mining conditions and various geological phenomena. The basic phenomenon responsible for the variations in mining conditions was found to. be the presence of a high lateral stress field residual to Deformation Phase III. In other words, stresses which owe their origin tc Deformation Phase III are still active at the time of mining. Variations in mining conditions are attributable to changes if the magnitude and direction of this lateral stress field and 23 its interaction with previously formed anisotropies, particularly those of Deformation Phase II.

These analyses have enabled the prediction of mining conditions ahead of the face and help form opinions as to the , most efficient means of extracting the coal in this environment.

ON SEDIMENTARY DYKES IN THE ABERDARE EAST COLLIERY HOLDING C.D. Rawlings and K.H.R. Moelle The University of Newcastle, N.S.W. The Aberdare East Colliery Holding is situated on the southeastern flank of the Lochinvar Anticline, within a graben structure defined by the Cessnock and Kitchener faults.

A number of sedimentary "dykes" with varying thickness (O.lSm to 3.00m) have been encountered by mining operations in the Greta Seam. The statistically determined major strike direction of the "dykes" is N4SoE with a considerable range (NOS Ow to N700E). A few NW-striking "dykes" have also been mapped, ranging from N3SoW to NS4°W. The NE and NW striking "dykes" thus have a rectangular relationship. The dip of the "dykes" is generally near vertical, but some occurrences have significantly lower lip values; namely as low as 25°. The length of a few sedimentary dykes has been measured from O.Skm to over 1. Okm ...

The composition of the dykes varies; commonly they consist of very coarse to coarse arenaceous material with many rock fragments, although finer varieties have been found. The components are cemented by argillaceous and siliceous material, with iron carbonate cement strongly developed as a secondary crystallation. The pore volume is very small to negligible.

Microfractures exist in the "dykes" and they can be geometrically correlated with macrofractures. Fracture cleavage is the predominant fracture type.

In outcrop the "dykes" display a great variety of forms ranging from straight vertical sheet-like "intrusions" to considerably distorted bodies. Intense folding has been observed in several "dykes", while others occur as sheared masses. Horizontal shearing movement is exemplified by displaced sedimentary "dykes".

24 Structural analyses in the colliery holding have bee facilitat~d by the movement pictures displayed directly by the "dykes", sometimes changing the analytical concepts markedly.

Mining operations are often impeded by the occurrenc, of sedimentary "dykes". On two occasions it has been fo' that the "dykes" influence the distribution of stresses in the Greta Seam and its surrounding strata.

It seems that the "dykes" are primary non-diastrophi, structures, probably intruding during the late peat stage from the floor. The emplacement mechanism of those sedim' ary bodies is still difficult to determine. Liquefaction' clastic material and emplacement by ice-cracks has been considered. At present, the authors favour seismically produced fracture systems and upward emplacement of clasti, material into those fractures.

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