Heavy Mineral Sands Potential of the Eucla Basin in South Australia — a World-Class Palaeo-Beach Placer Province

Feature

Heavy mineral sands potential of the Eucla Basin in South Australia — a world-class palaeo-beach placer province

Baohong Hou (Principal Geologist, CRC LEME, PIRSA Geological Survey Branch) Ian Warland (Senior Project Geologist, Iluka Resources Ltd)

Introduction e 130° id iv d N e T The eastern Eucla Basin is characterised g a in MUSGRAVE a by Tertiary coastal-barrier systems r M d S PROVINCE e o e r e r N a p m containing highly prospective beach a o l e o a a n t r n P P. na Wa i i g n n e y placers with great economic potential a e n L B ak P er a Lindsay P. P . Thro sel P k . . (e.g. Benbow et al., 1995; Hou et al., s e C P. s a r P e YILGARN . . y P 2003c). Of particular importance has P GAWLER . BLOCK a g n CRATON been the recognition of Eocene coastal- i r a l l a barrier systems; their distribution is now e T P lin Garford . Po on t s A reasonably well known from regional nt a A o P S o. P. c W Anth ny e investigations in the topographically n 30° e c BUNDA PLATEAU goonya P. elevated Ooldea, Barton and Paling Lefroy P. o Kin E EUCLA Ranges (e.g. Benbow, 1986, 1990; BASIN Benbow and Crooks, 1988). Exploration P. Eucla wa for heavy mineral sands (HMS) in the Co n Miocene coastline Continental shelf N region followed work on sedimentary Present ar m la -200 b coastline ent y res uranium and coal during the 1970s to P P GREAT AUSTRALIAN . early 1980s, that revealed numerous BIGHT HMS anomalies (Ferris, 1994). In Baker P. Continental slope some areas of the Ooldea Range, HMS Palaeovalley exploration was carried out from the mid-1980s until the early 1990s. 0 100 kilometres

HMS in this region have now become 0 200 kilometres an important exploration focus, as several generations of HMS-bearing shorelines NT have been recognised recently (Hou et al., QLD 2003b,c). The widespread development EUCLA WA of strandlines within the extensive sand BASIN SA dunes, and their possible role as major NSW Eucla ADELAIDE ACT heavy mineral carriers, make them an VIC important target for further exploration. EUCLA BASIN TAS Shuttle radar topographic map PIRSA 202683_009 Regional setting Fig. 1 Eucla Basin and major adjacent palaeovalleys (after Hou et al., 2003c). The Eucla Basin contains a sequence up to 300 m thick of Tertiary marine, coastal and palaeochannel sediments (Benbow et extending landward in the Gawler Craton Investigative methods al., 1995; Hou et al., 2003a). Its northern (Fig. 2). On the eastern basin margin, Examination of lithofacies, together margin extends ~2000 km from Western linear coastal landforms are preserved Australia to South Australia and contains a that include coastal dunes, dune ridges with creation of palaeontological, allo- large onshore province of Tertiary sediments and possible beach ridges, which have stratigraphic and sequence stratigraphic characterised by a number of palaeovalleys a morphology similar to the Quaternary frameworks from selected drillholes that drained the Precambrian Yilgarn Block, coastal dunes of southeastern Australia and minor outcrop across the eastern Gawler Craton and Musgrave Province (Benbow, 1990). The present landscape Eucla Basin, has shed new light on the (Alley et al., 1999; Fig. 1). is dominated by extensive tracts of sedimentary history of the sequence The ~1000 km long eastern margin of Quaternary deposits, largely superimposed of Tertiary marine transgressions and the Eucla Basin contains a large nearshore on preserved Tertiary landscape elements deposition in the region (Hou et al., 2001, and onshore region of Tertiary sediments including palaeovalleys, lagoons, estuaries 2003a,b,c, in prep.). Palaeogeographic characterised by a number of palaeovalleys and coastal barriers (Figs 1, 2). reconstruction was processed in a

4 MESA Journal 37 May 2005 Feature

Drainage divide

Barton Range

Palaeovalleys

Elevation Ceduna metres 798 S 683 BA IN 604 Ooldea EUCL A 627 Present day shoreline 450 Range Eucla 372 295 218 141 63 -14

S e Li rp 130° nd W e s a n N a n t o y n in o P a e r . in . SA L P WA a P . a e k P y e . g s n a P m . a P. r e M P. la a mrna Im Ta l ring ma . Koonuda rd P 3M rfo 39 7 Ga

Ma a P. H Ttknsie H i Wilkinson H H Lagoon Estuary P. H Anthony L H ong sho Paling Bay re d 30° rift H H

H Immarna H Lagoon nya P. Pidinga Bay H goo A H Kin H 41.5 Ma B EUCLA ?? BASIN Chundie Bay Narlaby P. 15 5– Ma ‘Colona’ Eucla H GREAT AUSTRALIAN BIGHT ‘Nundroo’ H

0 100 kilometres Continental slope

Late Eocene (Paling, Barton) barrier Inferred beach and dune ridges Major known anomalies of heavy mineral sands A Middle Eocene (Ooldea) barrier Cross-section (see Fig. 6) H

Maralinga embayment: marginal marine – estuarine clastics Inferred palaeoriver passing through barriers Wanna P. Marine carbonate platform Palaeovalley PIRSA 202683_010

Fig. 2 Regional relief interpreted from DEM and Tertiary geographical and lithofacies frameworks of the eastern Eucla Basin (after Hou et al., 2003c).

MESA Journal 37 May 2005 5 Feature

geographic information system based on a observations, has revealed a record Member of the Pidinga Formation), digital elevation model (DEM), remotely of stepwise evolution of marine and and estuarine clastics (Khasta sensed imagery, surface geological and non-marine environments for these Formation) drillhole data, and sedimentological potentially economic sediments (Hou et x Middle Miocene – Early Pliocene analysis in which key sedimentary al., in prep.). Four third-order eustatic marine limestone (Nullarbor surfaces (disconformities, tidal and/or cycles resulted in four generations of Limestone), lacustrine mudstone wave ravinement surfaces, transgressive marine and non-marine deposits across and dolomitic limestone (Garford VXUIDFHV DQG PD[LPXP ÀRRGLQJ this region (Fig. 4): Formation), and marginal marine surfaces) bounding the sedimentary x mid-Middle Eocene calcareous, – estuarine (carbonaceous) clastics packages were recognised. This new work glauconitic and gritty shallow marine (Kingoonya Member of the Garford SURYLGHVEHWWHUUHVROXWLRQRIVLJQL¿FDQW sandstone (Hampton Sandstone) Formation, and Narlaby Formation). features as shown in Figure 3. A number and limestone (lower Wilson Bluff of HMS-bearing transects were created, Limestone) Shoreline features based on detailed drillhole descriptions, x late Middle Eocene marine limestone A new model of the shoreline evolution, including microscopic study, to show the (lower Wilson Bluff), lagoonal distribution of mineralisation. based on major third-order sea-level carbonaceous limestone (Paling events, provides valuable geological Formation), and marginal marine information on the Tertiary landscape Stratigraphic units ± ÀXYLDO FDUERQDFHRXVFODVWLFV DQGGH¿QHVIRXUJHQHUDWLRQVRIVKRUHOLQHV The stratigraphy of the eastern Eucla (Maralinga Member of the Pidinga — mid-Middle Eocene (41.5 Ma), late basin margin has recently been revised Formation) Middle Eocene (39 Ma), Late Eocene (Clarke et al., 2003; Hou et al., 2003c). x a complex sequence of Late Eocene (37 Ma), and Neogene (15–5 Ma; Hou Detailed re-examination of the onshore marine limestone (upper Wilson et al., 2003c; Fig. 2). These shorelines lithostratigraphy of the eastern Eucla %OXII PDUJLQDO PDULQH ± ÀXYLDO are highly prospective for beach-sand- %DVLQ EDVHG RQ ¿HOG DQG ERUHKROH carbonaceous clastics (Anthony hosted heavy minerals related to wave-

WA Overlying night- SA time thermal imagery

Interpreted Tertiary Shuttle Radar palaeochannels Topographic Map and lagoons

Interpreted Eocene barriers

Immarna Trans Australia Railway Ambrosia Jacinth

Eucla

Great Australian Bight

0 100 kilometres

PIRSA 202683_011

Fig. 3 Comparison of the coastal barriers delineated from previous (brown solid lines, SA_GEODATA) and this (blue dash line) study in GIS. Note that there is up to 25 km difference. The light brown tone outlined by the blue dash lines is the distribution of barrier deposits interpreted subsurface. Superimposed light brown tone (50% transparency) is the distribution of Tertiary palaeochannel and lagoonal deposits interpreted previously (brown solid lines). The old (Immarna) and new (Jacinth and Ambrosia) HMS discoveries are also shown (after Hou et al., 2004).

6 MESA Journal 37 May 2005 Feature

Based on interpretation of the depositional environments, the HMS 1989) SA

Ooldea Barton Age lagoonal barrier estuarine accumulated in Tertiary shorelines basin barrier channel (Ma) estuary as bodies of coastal sand, probably events, representing multiple higher order RSL (McGowran, highstands (Hou et al., 2003b). Recog- unconformity

s nition of these coastal depositional y

Plio Narlaby Formation

environments within several generations 6–4? E. Jerem Point? of shorelines gives meaning to anomalous Nullarbor Garford intersections of beach placers and aids Limestone Formation Kingoonya targeting of future drilling. Member 16–6?

Miocene New discoveries Mid–Late Cadell– Balcombe unconformity 7ZR GLVFRYHULHVRI VLJQL¿FDQW 34.6–33.7 Tuit Barton Sand zircon-rich HMS were announced on 5 November and 17 December 2004 by Khasta Formation upper Iluka Resources Ltd at their Jacinth and

36–34.6 Wilson Bluff Eocene Limestone Ambrosia prospects. Assay results from the discoveries show the prospects to Late Anthony Member have an average heavy mineral content of

37–36 10% (up to 82%) containing an average OoldeaOoldea SandSand Pidinga Formation of 55% zircon, 7% rutile and 22% Paling Fm ilmenite — comparing ‘favourably’ to the lower Eneabba province in Western Australia

39–37 Wilson Bluff Limestone Maralinga Member in its ‘heyday’ (Fig. 7). Ambrosia Eocene

Tortachilla Tuketja unconformity prospect may have an even higher zircon endowment compared to the nearby Middle Hampton Jacinth deposit. Visual indications for the 43–40 Wilson Bluff Sandstone PRE-TERTIARY ROCKS other reconnaissance lines suggest that anomalous mineralisation extends across Pre-Tertiary PIRSA 202683_012 an extensive area; so far all that detected occurs in unconsolidated sand above Fig. 4 Stratigraphic framework for the eastern Eucla Basin and adjacent palaeovalleys (after the watertable. The highly prospective Hou et al., 2004, in prep.). nature of the region is highlighted by associated highstands of relative sea level by longshore drift (Fig. 2). Selected the fact that both Jacinth and Ambrosia )LJ 7KH7HUWLDU\VKRUHOLQHVGH¿QHG drillhole and cross-sectional distributions are located along the same geological as bodies of coastal sand, here comprise of HMS anomalies (1–27% heavy feature and that there is >40 km strike beach, shoreface, barrier, dune, tidal minerals) from the Ooldea Range (Fig. 6) length of this feature still untested. inlet, washover and lagoonal facies (Hou show that the placers occur either in the In 2001, Iluka applied for EL 2900, et al., 2001b), probably representing upper part of thick barrier–dune sand which includes the new Jacinth and multiple higher order highstands (Hou bodies, often 20 m or more below the Ambrosia discoveries. During 2003, et al., 2003a). Shorelines are associated surface, or close to an erosional bedrock the company applied for additional with numerous palaeodrainage systems contact. Analogous to the beach placer exploration rights over substantial that drained areas of cratonic basement deposits of the eastern Australian coast tracts of the Ooldea and Barton Ranges. and supplied vast quantities of sediment FODVVL¿HGE\5R\ VHYHUDOW\SHVRI Drilling of strandlines commenced in to the basin (Ferris, 1994). +06GHSRVLWVFDQEHLGHQWL¿HGE\VHGL 2004, and the Jacinth and Ambrosia mentological study (Hou et al., 2003c): prospects are early exploration successes Heavy mineral beach x lag deposits along erosional dis- that will drive an expanded program of placers conformities and/or unconformities exploration drilling and sample testing during 2005. Adelaide Resources Ltd transgressive deposits at the rear of Features and types x LV DOVR VHW WR EHQH¿W ZLWK LQFUHDVHG highstand (swash-aligned) barriers, Concentrations of detrital rutile, activity on their adjoining EL 2840, in including those trapped near the zircon, ilmenite, and minor leucoxene joint venture with Iluka. palaeovalley passes and monazite occur as beach placers 7R GDWH LGHQWL¿HG KLJKJUDGH in highstand strandlines along the x regressive deposits at the front of anomalies of rutile, zircon, ilmenite Tertiary shorelines (e.g. Hou et al., prograded barriers and leucoxene occur in shoreline 2003c). Highstand geomorphic features x aeolian deposits, as low-grade deposits. Mineralised zones are are excellent for the formation and disseminated concentrations in trans- thought to represent stacked shoreline localisation of beach placers, mainly gressive dunes. facies that accumulated during marine

MESA Journal 37 May 2005 7 Feature

Conclusions and future work The Eucla Basin has potential as a major new HMS province in Australia. Here, recent re-examination of the Tertiary lithostratigraphy and geography has revealed a record of stepwise evolution of marine and non-marine environments for these potentially economic sediments. The new model of shoreline evolution in the eastern Eucla Basin has provided valuable geological information for the Tertiary ODQGVFDSHV 6LJQL¿FDQW DQRPDOLHV LQ beach placers and related coastal deposits are associated with at least four third-order Tertiary shorelines, ranging in age from Middle Eocene to Early Pliocene. The region is highly prospective for beach- sand-hosted heavy mineral deposits related to wave-associated highstands and rises of relative sea level. Dark grey HMS (82%) in sample bag, Jacinth prospect. (Photo 401703)

transgressions in the Tertiary. The Jacinth and Ambrosia prospects contain up to 45% detrital HMS over a thickness of 25 m, with the richest up to 82% HMS and the thickest part being ~35 m. There is a tendency for the Jacinth and Ambrosia prospects overall to become a continuous and more mineral-rich zone towards both the southeast and northwest of their enclosing portion of the Ooldea barrier (Pidinga Bay; Figs 2, 3). HMS appear to have been concentrated where the oversteepened shoreface acted as a virtual headland that focused wave- reworking processes during marine transgressions (Roy and Whitehouse, 2003). The most prospective strata are the barrier and associated sands of Tertiary shorelines that were buried by voluminous sand dunes over a period of 40 million years. The geographic and stratigraphic distributions of HMS in Tertiary sediments suggest contemporaneous transport through palaeovalleys predominantly from Precambrian cratons.

Sample sequence of drillhole YE 0105 (for location see Fig. 7), Jacinth prospect. Note that the whole sequence similar to this is often mineralised at Jacinth. (Photo 401704)

8 MESA Journal 37 May 2005 Feature

Dune

Swamp and marsh Estuarine bars

Dune–barrier and Beach and marine forest overwash fans

Heavy mineral sands

Estuarine marsh

Ebb-tidal delta

0 50 kilometres 0 50 kilometres

(a) (b)

Abandoned Barrier inlet and dune Lagoonal marsh Salty lakes

Flood-tidal delta Barrier and dune

Lacustrine deposits Heavy mineral sands Heavy mineral sands

Ebb-tidal delta Local subsidence

0 50 kilometres 0 50 kilometres

Fig. 5 Palaeogeographic evolution model of the Eocene coastal barriers and related facies (after Hou et al., in prep.). The widespread development of (up to 100 m) at the axes of the sand ranges are detectable. The challenge for future strandlines beneath the extensive sand will obviously deter exploration, but the exploration lies in discovering not only dunes, and their possible role as major impressive width of the barriers (up to 25 dune–barrier sands beneath cover, but also HMS carriers, make them an important km) which blanket large areas of more beach, shoreface, dune, tidal inlet, and element and a challenge in further shallow cover (0–40 m) suggests that washover sediments beneath thin cover. exploration. The presence of thick cover the heavy-mineral-bearing strandlines The use of high-resolution DEM and

MESA Journal 37 May 2005 9 Feature

W E 398 33 0 500 metres 97 393 96 236 180 EB B B EB 92 E3 E2 EB B 394 235 232 37 E3 234 95 B 391 389 B EB E3 B 231 AHD) EB B B B EB E E E2 E E3 EB

(m ferricrete

Q EB 390 160 Q medium sand Tbo Elevation 140 Tbp-m fine Precambrian basement Tbp-m sand Cross-bedded coarse sand-granules Cross-section A: 1.0–25.4% HM (with ilmenite 32%; rutile 3%; zircon 28%; leucoxene 30%; limonite 5%)

Le Aeolian facies I

Zr Q Concentrated Le

I Zr I Zr Zr 0.3 mm 25% HM 0.5 mm

Q R Zr I

Lag facies Transgressive 62% HM R barrier facies Zr Le

I Zr

0.3 mm 17% HM 0.5 mm

133 116 SW 134 NE 220 32 15 B EB EB E117 EB 18 B B 35 123 E1 E1 19 124 B B 0 500 metres 122 EB E1 E1 114 30 B 200 EB B B EB 29 E1 Q E131 E B 121 Ferricrete EB 136 113 B E1 E1 B EB EB AHD) E 120 180 Ferricrete (m EB 112 111 160 Q EB Tbo-l Elevation 140 Tbo

beach facies basement coarse sand to granules Tbp-m 120 Cross-section B: 1.0–27.2% HM (with ilmenite 35%; rutile 3%; zircon 51%; leucoxene 8%; trash 28%) PIRSA 202683_014

Fig. 66HOHFWHGJHRORJLFDOVHFWLRQVDQGLQWHUVHFWHG+06 =U]LUFRQ,LOPHQLWH5UXWLOH/HOHXFR[HQH4TXDUW]UHÀHFWHGSRODULVHG light; cross-sections are located in Fig. 2).

10 MESA Journal 37 May 2005 Feature

(a) (b) Ambrosia prospect (line 5833)

237500 mE 235000 mE 232500 mE SW NE 6585000 mN Depth YE0208 YE0105YE0104 YE0102 (m) YE0207 YE0206 YE0205 YE0103YE0212 YE0209 0 YE0210 YE0211

Ambrosia 10 prospect

6582500 mN 30 27 m 30 m 31.5 m 33 m 33 m 34.5 m 30 m 37.5 m 36 m 33 m 33 m 34.5 m EL 2900 Heavy Mineral contours — Laboratory HM% ILUKA Resources 0 200 metres Ltd 1–3% HM 3–10% HM 10–45% HM

6580000 mN (c) Jacinth prospect (line 5776)

W E

YE0095 YE0094 YE0084 YE0097 YE0096 YE0093 YE0092 YE0085 Depth YE0091 YE0090 Jacinth (m) YE0086 YE0088 prospect 0 YE0087 YE0089 6577500 mN

21 m 0 1000 metres 27 m 30 33 m 24 m 30 m 6575000 mN 36 m 33 m 24 m 42 m 42 m 28 m 42 m 31.5 m 33 m Mineralised zone Line 5833 Heavy Mineral contours — Laboratory HM% 0 200 metres Drillhole Line 5776 >1% HM >3% HM >20% HM PIRSA 202683_015

Fig. 7 Drilling sections showing heavy mineral content of the Ambrosia and Jacinth HMS prospects. ground magnetics, remotely sensed (e.g. colleagues of the Geological Survey Benbow, M.C., 1986. TALLARINGA map NOAA, Landsat, ASTER) night-time Branch, PIRSA Division of Minerals and sheet. South Australia. Geological Survey. thermal imagery (Fabris, 2002), induced Energy. In particular we acknowledge the Geological Atlas 1:250 000 Series, sheet SH53-5. polarisation and ground penetrating work of Mark Benbow, Alistair Crooks, Benbow, M.C., 1990. Tertiary coastal dunes of radar in the areas of shallow cover may Paul Rogers and members of the former the Eucla Basin, Australia. Geomorphology, target strandlines developed in the high- Biostratigraphy Branch — Neville Alley, 3:9-29. energy beach facies. Future exploration Andrew Rowett, Marigold White, Lyn Benbow, M.C. and Crooks, A.F., 1988. should seek a greater understanding of Broadbridge and Liliana Stoian —whose Topographic contour maps and data, WKH DOORVWUDWLJUDSKLF VLJQL¿FDQFH RI WKH work has ultimately led to the successful western South Australia. South Australia. Tertiary succession and apply a greater HMS discoveries in the Eucla Basin. Department of Mines and Energy. Report Book, 88/44. emphasis to palaeogeomorphic and 7KH PDQXVFULSWZDV VLJQL¿FDQWO\ Benbow, M.C., Lindsay, J.M. and Alley, N.F., palaeogeographic factors. improved by the thorough and helpful 1995. Eucla Basin and palaeodrainage. In: review of Larry Frakes and John Drexel, J.F. and Preiss, W.V. (Eds), The Acknowledgements Keeling. geology of South Australia. Vol. 2, The Phanerozoic. South Australia. Geological The authors thank numerous people Survey. Bulletin, 54:178-186. involved in contributing to the high- References Clarke, J.D.A., Gammon, P.R., Hou, B. and TXDOLW\ JHRVFLHQWL¿F NQRZOHGJH EDVH Alley, N.F., Clarke, J.D.A., Macphail, M. Gallagher, S., 2003. Middle to Late Eocene relating to the Eucla Basin, which and Truswell, E.M., 1999. Sedimentary stratigraphic nomenclature and deposition in the Eucla Basin. Australian Journal of Earth this article and associated work draws LQ¿OOLQJVDQGGHYHORSPHQWRIPDMRU7HUWLDU\ palaeodrainage systems of south-central Sciences, 50:231-248. upon. This information is the result Australia. International Association of Fabris, A., 2002. Thermal satellite imagery of the meticulous and extensive work Sedimentology. Special Publication, 27:337- — an aid to heavy mineral sand discoveries. completed by current and former 366 MESA Journal, 24:24-26.

MESA Journal 37 May 2005 11 Feature

Above Iluka drill rig testing the Jacinth deposit. (Photo 401705) Right Lexie Bracher and Ian Warland of Iluka Resources holding a pan of heavy mineral sands at the Jacinth prospect. (Photo 400958)

Ferris, G.M., 1994. Review of heavy mineral Hou, B., Frakes, L.A., Alley, N.F. and Gammon, in the eastern Eucla Basin, South Australia. sand exploration in South Australia: Eucla P., 2003b. Facies and sequence stratigraphy of Sedimentary Geology. Basin. South Australia. Department of (RFHQHYDOOH\¿OOVLQ(RFHQHSDODHRYDOOH\V Li, Q., James, N.P. and McGowran, B., 2003. Primary Industry and Resources. Report the eastern Eucla Basin, South Australia. Middle and Late Eocene Great Australian Book, 94/22. Sedimentary Geology, 163:111-130. Bight lithobiostratigraphy and stepwise Hou, B. and Frakes, L.A., 2004. Tertiary sea Hou, B., Frakes, L.A., Alley, N.F. and Heithersay, evolution of the southern Australian levels and heavy mineral deposition in the P., 2003c. Evolution of beach placer shorelines continental margin. Australian Journal of eastern Eucla Basin, SA. In: Roach, I.C. and heavy mineral deposition in the eastern Earth Sciences, 50:133-128. (Ed.), Regolith 2004. CRC LEME, Perth, Eucla Basin, South Australia. Australian McGowran, B., Li, Q. and Moss, G., 1997. The Cenozoic neritic record in southern Australia: pp.140-143. Journal of Earth Sciences, 50:955-965. the biogeohistorical framework. In: James, Hou, B., Frakes, L.A. and Alley, N.F., 2001. Hou, B., Frakes, L.A., Alley, N.F. and Heithersay, N.P. and Clarke, J.D.A. (Eds), Cool water P., 2004. Tertiary beach placer potential of 'HYHORSPHQWRI JHRVFLHQWL¿F PRGHOV IRU carbonates. Society for Sedimentary Geology. the exploration in Tertiary palaeochannels the eastern Eucla Basin — old province — Special Publication, 56:185-203. draining the Gawler Craton, SA. South new ideas. In: McPhie, J. and McGoldrick, Roy, P.S., 1999. Heavy mineral beach placers Australia. Department of Primary Industries P. (Eds), Dynamic Earth 2004: past, present in southeastern Australia: their nature and and Resources. Report Book, 2001/21. and future. 17th Australian Geological genesis. Economic Geology, 94:567-588. Hou, B., Frakes, L.A., Alley, N.F. and Clarke, Convention, Hobart, 2004. Geological Roy, P.S. and Whitehouse, J., 2003. Changing D.A., 2003a. Characteristics and evolution Society of Australia. Abstracts, 73:234. Pliocene sea levels and the formation of of the Tertiary palaeochannels in the NW Hou, B., Alley, N.F., Frakes, L.A., Stoian, L. heavy minerals beach placers in the Murray Gawler Craton, South Australia. Australian DQG &RZOH\ :0 LQ SUHS 6LJQL¿FDQFH Basin, southeastern Australia. Economic Journal of Earth Sciences, 50:215-230. of stepwise evolution of Eocene sea level Geology, 98:975-983.

12 MESA Journal 37 May 2005