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Geological Society of Malaysia, Bulletin 49, April 2006, p. 157-167

Sedimentary facies development of breccia deposit in TanjungSekakap-Tanjung Murau area, near Mersing, Johor,

Peninsular Malaysia

SUGENG S SURJONO 1,2, MOHD. SHAFEEA LEMAN1, KAMAL ROSLAN MOHAMED1 & CHE AZIZ ALI1

1School of Environmental Science and Natural Resources,Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, MALAYSIA

2Geological Engineering Department, Faculty of Engineering,Gadjah Mada University, Yogyakarta, INDONESIA

Abstract: Breccia dominated rocks outcropping in the Tanjung Murau – Tanjung Sekakap area have been deposited in a compositesystem of alluvial fans and Gilbert-type deltas. The sedimentary facies ranges from boulder-dominated facies at the bottom togravelstone-sandstone-dominated facies at the top of the succession. Other recognized facies are disorganized boulder-cobble-supported breccia (Bd), crudely stratified cobble-boulder-rich breccia (Bs), crudely stratified cobble-rich gravelstone (Gs-1),disorganized clast-supported gravelstone (Gd), crudely stratified pebble-rich gravelstone (Gs-2), normally-inversely-graded gravelstone(Gn-i), crossbedded gravelstone (Gc), stratified sandstone (Ss), massive sandstone (Sm) and homogenous mudstone (Mh) facies.Alluvial fan association feature discontinuous breccias and gravelstones (facies Bd and Bs), where sheet-floods and debris flows aredominant. The gravelstone dominated facies Gd, Gs-1 and Gs-2 intercalated with facies Gc are associated with the topset–foreset ofa Gilbert-type fan-delta. The Gilbert-type topset are represented by facies Gc, Gn-i and Gs-2 as well as facies Ss. The dominance ofbreccia and gravelstone facies of alluvial fan and Gilbert-type topset – foreset delta facies associations suggest that these sedimentswere deposited on a steeply sloping continental margin with a rate of deposition similar to the rate of subsidence.

INTRODUCTIONRudaceous rocks or rudrock (Laznicka, 1988) are

prominent along the east coast of Johor from TanjungSekakap to Tanjung Tenggaroh (Figure 1) with isolatedoccurrence at Pulau Batu Chawang (Ibrahim Abdullah etal., 1991) and at Tanjung Leman (Suntharalingam, 1991).This rock unit was described by Koopmans (1968) asTriassic Murau Conglomerate Member of the TembelingFormation. He regarded this rudaceous unit as the basalmember of the formation based on the presence of anunconformable boundary between the rudrock and theunderlying metamorphic rocks. However, because of itsgeographic isolation, Burton (1973) suggested that theMurau Conglomerate be removed from the TembelingFormation. Khoo (1977) upgraded the TembelingFormation to Tembeling Group status with MurauConglomerate being excluded from it. Later, Ahmad Jantanet al. (1988) suggested the Murau rudaceous unit to beupgraded to the Murau Formation and suggested a Jurassic-Cretaceous age for the Formation. Meanwhile, Che AzizAli and Kamal Roslan Mohamed (1997) suggested thatthe Murau Formation has a close genetic affinity withseveral other conglomerate units exposed along the coastand offshore Terengganu, and indicating a possible Triassicor Permian age for the rock unit under discussion.

The present study tentatively divides the MurauFormation into three separate units, which are the Murau,Tenggaroh, and Tanjung Leman units. These units differfrom one another in terms of facies assemblages,sedimentary environments and depositional mechanisms.The Tanjung Leman unit consists of alternating mudrockand rudrock in the bottom part, with thick fine sandstone

and shale in the upper part. The clasts of rudrock at TanjungLeman are mostly rounded to very well rounded, moderateto well sorted, grain supported, with average clasts ofpebble to cobble size. The sedimentary textures andstructures suggest that the depositional process wasdominated by traction flow. On the other hand, the Murauand Tenggaroh units are dominated by thick beds of brecciain the lower part, followed by gravelstone facies andsandstone and mudstone in the upper part. The clasttextures in Murau and Tenggaroh units are mainly angularto very angular, poorly sorted with dominant clast of cobblesize, occasionally up to boulder size. These sedimentarytextures suggest that the depositional process wasdominated by debris flow. Mineralization is common inboth matrix and clasts of the Tenggaroh rudaceous rock,but apparently absent in other units. This mineralizationmust be carefully studied in order to understand therelationship between the mineralization and depositionalhistory.

BRECCIA OR CONGLOMERATE?In widely used geological glossaries, such as that of

Bates and Jackson (1987), breccias are often described ascoarse-grained clastic rock, composed of angular brokenrock fragments held together by mineral cement or in afine-grained matrix. This differs from conglomerates inthat the fragments have sharp edges and unworn corners.Laznicka (1988) states that there is no established boundarybetween conglomerate and breccia, but Reimold (1998)proposed that the term conglomerate be restricted to clasticrock, whereas breccia is more universal in usage. However,in day-to-day geological work this distinction is often

SEDIMENTARY FACIES DEVELOPMENT OF BRECCIA DEPOSIT IN TANJUNG SEKAKAP-TANJUNG MURAU AREA, JOHOR, PENINSULAR MALAYSIA

Geological Society of Malaysia, Bulletin 49158

neglected. In general, sedimentologists are inclined toemploy the term conglomerate regardless of the highpercentage of angular clasts in the rock. Thus, rocks withover 50% and up to 90% of angular fragments are stillcommonly termed conglomerate (Laznicka, 1988).

As for the Murau rudrock unit, previous authorsincluding Koopmans (1968), Ahmad Jantan et al. (1988),Che Aziz Ali and Kamal Roslan Mohamed (1997), amongothers described this rock unit as conglomerate, althoughthey recognized that the clasts are predominantly angularto very angular. The present study refers to this rudrock asbreccia rather than conglomerate, implying a differentperspective in terms of its facies development and hencethe depositional environment and processes. Laznicka(1988), for example regards most breccia is formed rapidlyat or near the point of transition between one system,environment or depth level to another. In his study atDwarkeswar River, India, Sengupta (1994) has shown thatthe roundness of pebbles changed from subangular torounded over a distance downstream of 100 km.

FAN DELTA SETTINGGravels are normally transported in a wide spectrum

of physical conditions leading to a range of textural andstructural variations in the ensuing deposits (Miall, 1996).Sediments dominated by breccias or conglomerates havecommonly been interpreted as a product of fan-delta or

alluvial fan sedimentation (Chough et al., 1990; Hwang etal., 1995; Dickie & Hein, 1995; Kim et al., 1995; Kimand Chough, 2000; Benvenuti, 2003). A fan-delta, isdefined by Holmes (1965) as an alluvial fan that progradesinto a standing body of water and is a common depositionalsystem in various tectonic and geological settings.

Based on basinal setting, both Wescott and Ethridge(1980) and Postma and Roep (1985) suggested three end-type models for fan-deltas, which are the shelf-, slope-and Gilbert-types. These models contain numerous variantsdepending on the complex interplay of uplift-subsidenceof the adjacent highlands, fluvial and marine processes,sediment supplies, sea level changes and several otherfactors (Chough et al., 1990). Postma and Roep (1985)divided the Gilbert-type delta into a tripartite faciesassociation, i.e., the topset, foreset and bottomset basedon its morphology. In some cases, a fan-delta is notdeveloped as a single-type, but rather formed as acomposite type. Chough et al. (1990), for example,determined the Doumsan Fan-Delta in Southeast Korea asa composite fan-delta system and classified their rockassemblages into seven facies associations includingalluvial fan, Gilbert-type topset, Gilbert-type foreset,Gilbert-type toeset, prodelta, slope apron and basin plain.

This paper addresses the sedimentary faciesdevelopment of breccia-dominated deposits exposed inTanjung Sekakap – Tanjung Murau area, taking intoconsideration both vertical and lateral facies developmentbased on lithological logs from measured sections. This isfollowed by discussion leading towards interpretation onthe possible sedimentary environments and processes.

GEOLOGICAL SETTINGThe breccia deposit in Murau area are composed of

polymict clasts comprising schist, phyllite, slate, shale,quartzite, sandstone and mudstone, and apparently devoidof volcanics. The clasts are generally angular to veryangular in shape, with sizes ranging from granule toboulder, poorly sorted and randomly oriented, in placespoorly imbricated. The deposit unconformably overlies theolder metamorphic rock of Mersing Formation. Theunconformity can be seen at Tanjung Murau (Figure 2a)and at a small hill near Pasir Landa beach, 1.5 km south ofTanjung Sekakap (Figure 2b). In the lowermost part of thesuccession, the clast composition seems to be entirely ofmetamorphic rocks. At Tanjung Murau, for example, theclasts of the breccia are mainly made up of schist, phylliteand quartzite.

The Murau breccia formed a thick sedimentary rocksequence with bedding orientation only visible in thesandstone or mudstone facies. The strata have a roughlynortheast – southwest (230o-240oE) strike, dipping 30o -50o to the northwest (Figure 1). The facies succession isrepeated both laterally and vertically. The total thicknessof the sequence varies from 50 meters to more than 100meters.

Figure 1. Distribution of Murau rudaceous rocks betweenTanjung Sekakap and Tanjung Murau, Johor.

SUGENG S SURJONO , MOHD. SHAFEEA LEMAN, KAMAL ROSLAN MOHAMED & CHE AZIZ ALI

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Apart from the Murau Conglomerate and MersingFormations, the Jasin Volcanics are also well developedaround the Mersing coast in the north of the Mersing Riverand on several offshore islands east of Tanjung Sekakap –Tanjung Murau. The volcanic rocks were described byCook and Suntharalingam (1970) as the part of the LatePermian – Early Triassic Jasin Volcanic unit. Another seriesof volcanic sequence, the Middle Permian Sedili Volcanic(Suntharalingam, 1991) is best developed in Ulu Sediliarea, southwest of Tanjung Murau. The absence of clastsof volcanic origin suggest that the Murau Formation isolder than the late Permian Jasin Volcanic unit and perhapsalso older than the Middle Permian Sedili volcanic unit.The granite that intrudes the Jasin Volcanic unit at PulauBabi Besar is the youngest rock unit in the area aroundTanjung Sekakap – Tanjung Murau.

SEDIMENTARY FACIES ANALYSISNine lithological logs were constructed based on

studied sections outcropping along the coastline betweenTanjung Sekakap and Tanjung Murau and several man-made slope cuts within Sungai Sekakap area. Tensedimentary facies (Table 1) have been recognized fromthese logs based on physical characteristics such as grainsize distributions, textures and sedimentary structures.

The sedimentary facies of Murau rudaceous rocks canbe described as follows:

Facies Bd: Disorganized, boulder-cobble supported breccia (Figure 3a,b)

The Facies Bd is generally thick to very thicklybedded. Tanjung Murau lithological log 07 (Figure 6)shows the total thickness is up to 20 meters, whereas inthe Tanjung Sekakap lithological logs 02 and 05 (Figure6) the thickness is significantly less. The bed is dominatedby tightly packed, poorly sorted and randomly orientedgranule- to boulder-sized clasts. The clasts are angular tovery angular in shape. The occurrence of schist rock chips

in the lower part of Tanjung Murau sequence suggest thesource rocks came directly from the underlyingmetamorphic rock. The largest clast found is a 60 cm longquartzite (Figure 3a,b) indicating short distance and fastsedimentation. Inverse grading is seen at the base of thefacies in both lithological logs 05 and 07 (Figure 6). Asharp contact with the underlying beds is observed inlithological logs 02 and 05 (Figure 6), and a weak wavybase is exhibited in lithological log 07 (Figure 6). Thematrix is made up of poorly sorted sand. Shultz (1984)interpreted a similar facies formed from turbulent sub-aerial debris flow, while Kim and Chough (2000) onlysuggested a debris flow origin.

Facies Bs: Crudely stratified cobble-boulder-rich breccia (Figure 3c,d)

The Facies Bs refers to moderate to thickly bedded(20-150 cm), crudely stratified cobble-rich breccia withvery coarse sandy matrix (Figure 3c,d). Poor to moderateimbrications sometimes developed within the pebblyhorizons. Gradual diffusion is common within the cobble-boulder layers, showing repetition of graded bedding withobscure facies boundaries. This structure is well developedin the lower part of lithological log 05 (Figure 6), in closeassociation with Facies Bd. In the Tanjung Muraulithological log 07 (Figure 6), the cobble-boulder layersare developed without a distinct pattern of fabric and thusdifficult to trace laterally due to the amalgamation, thinningand wedging-out of layers. The Facies Bs is usually foundimmediately above the Facies Bd as seen in the TanjungMurau lithological log 07 (Figure 6) and in the TanjungSekakap lithological log 05 (Figure 6). For the LatePalaeozoic Cutler Formation in western Colorado, USA,Shultz (1984) suggested that Facies Bs is also resulted fromturbulent sub-aerial debris flow.

Facies Gs-1: Crudely stratified cobble-rich gravelstone (Figure 3e,f)

The Gs-1 facies appears to be similar to the facies Bsbut with predominantly smaller clasts (Figure 3e, f). Thethickness of the bed is moderate to thick (20-100 cm).The facies is characterized by mixtures of pebble andcobble clasts with coarse to very coarse-grained sandymatrix. The clasts are either floated within matrix or formedimbrication with indistinct boundaries between layers.Toward the top of the facies, the smaller clasts graduallydiffuse to the overlying facies. Facies Gs-1 is usually foundin association with facies Bs, Bd and Gd as in the TanjungMurau lithological log 07 and Tanjung Sekakap lithologicallog 05 sections (Figure 6). Shultz (1984) interpreted faciessimilar to Facies Gs-1 as well as Facies Bd and Bs as partof a turbulent sub-aerial debris flow deposit, but accordingto Hwang et al. (1995) in the Miocene Pohang Basin ofSE Korea the facies is deposited by density-modified grainflow or by cohesion-less debris flow.

Figure 2. a – Angular unconformity between schist-phyllite andbreccia at Tanjung Murau. b – Disconformity contact betweenblack shale-slate and breccia (basal conglomerate) at Pasir Landa,near Tanjung Sekakap.



Facies Gd: Disorganized, clast-supported gravelstone (Figure 3g,h)

The beds in Facies Gd are generally thick to very thick(100 cm – 3 m). Apart from having relatively smaller clasts,this facies is texturally and structurally similar to the FaciesBs. The bed is dominated by tightly packed, moderate topoorly sorted, randomly oriented or partially imbricatedclasts of angular to sub-angular granule to cobble (Figure3g,h). Th e fabric is crudely imbricated or stratified clastsin the lower to middle part of the succession in TanjungSekakap lithological log 05, and Tanjung Muraulithological log 09, (Figure 6). Hwang et al. (1995) andKim and Chough (2000) interpreted similar facies as debrisflow or channelized debris flow deposits.

Facies Gs-2: Crudely stratified pebble-rich gravelstone (Figure 4a,b)

The crudely stratified pebble-rich gravelstone faciesis characterized by alternation of pebbly gravelstone andcoarse to very coarse sandstone layers (Figure 4a,b). Thegravelstones contain tightly packed to gradually diffusedpebbles, whereas the sandstone layers contain someunsupported clasts. Each facies unit ranges in thickness

from 10 cm to 100 cm, usually thinning or wedging-out toform lateral transition to other facies. In Tanjung Muraulithological log 09 (Figure 6) the Facies Gs-2 is associatedwith facies Gd, while in Tanjung Sekakap lithological log02 and 03 (Figure 6) it is associated with facies Ss andGn-i. Based on their study on the bouldery deposits of theKorean Kyokpori Formation, Kim et al. (1995) interpretedthat the Facies Gs-2 is developed in an unstable regionwithin a cohesion-less debris flow. However, Benvenuti(2003) inferred the facies as a sub-aerial deposit formedby unconfined hyper-concentrated flow, related to gravitytransformation in the lower fan delta depositionalenvironment.

Facies Gn-i: Normally-inversely gradedgravelstone (Figure 4c,d)

Generally the Facies Gn-i comprises medium to thickgravelstone beds (30-150 cm) with poor to moderatelysorted clasts of granule to cobble sizes (Figure 4c,d). Theclasts sometime are poorly imbricated in a sandy matrix.The gravelstone facies is inversely graded and commonlyoverlain by the Facies Bd in association with basalconglomerates as in the Tanjung Murau lithological log07 and Tanjung Sekakap lithological log 02 (Figure 6).

Table 1: Diagnostic features arising from the studied sedimentary facies.

Facies Type (Code) CharacteristicsDisorganized, boulder-cobble Thick to very thick beds of randomly oriented, tightly packed, poorly sorted,supported breccia (Bd) very angular to angular granule- to boulder-sized clasts. Beds usually with basal

inverse grading and sharp planar base.Crudely stratified cobble- Moderate to thick beds of alternating cobble-bouldery layer, pebbly layer andboulder-rich breccia (Bs) very coarse sandstone with moderate to poor imbrication. Beds usually with

gradual diffusion, thinning and wedging-out of layers.Crudely stratified cobble-rich Moderate to thick beds of alternating pebble-cobbly layers and coarse to verygravelstone (Gs-1) coarse sandstone with moderate imbrication, floating clasts, gradual diffusion

and diffused boundaries.Disorganized, clast-supported Thick to very thick beds of randomly oriented, partly imbricated, tightly packedgravelstone (Gd) clasts, moderate to poorly sorted, angular to sub-angular, granule-to cobble-sized

clasts, sharp and flat base, several as channel infills.Crudely stratified pebble-rich Moderate to thin beds of alternating pebbly layers and coarse to very coarsegravelstone (Gs-2) sandstones with moderate imbrication. Beds with gradually diffused boundary,

several thinning and wedging-out layers.Normally-inversely graded Moderate to thick beds of imbricated granule- to small cobble-sized clasts ingravelstone (Gn-i) poorly to moderately sorted sand matrix. Beds with inverse to normal grading.

(Inverse grading is common in basal conglomerates).Cross bedded gravelstone (Gc) Moderate to thick beds of granule- to small cobble-sized clasts. Beds with normal

or inverse grading and thinly bedded foresets, usually mound shaped, commonlyamalgamated with facies Gs-2 or Gn-i.

Stratified sandstone (Ss) Moderate to thin beds of reddish, very fine- to coarse-grained sandstone. Bedswith obscure normal grading, sharp amalgamated contacts, commonly cut bypocket breccias or channel infills.

Massive sandstone (Sm) Moderately bedded reddish, fine- to coarse-grained sandstone. Beds with obscurenormal grading and some bioturbation, associated with facies Ss.

Homogenous mudstone (Mh) Thickly bedded reddish mudstone with gravel pockets and lenses, structurelessor with weak bedding orientation.


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The normally-inversely graded gravelstone faciesassociated with sandy facies Ss and Gc is best developedin the upper half of the facies succession in TanjungSekakap lithological logs 03 and 04 (Figure 6). Hwang etal. (1995) interpreted that such facies is deposited bycohesive or highly turbulent debris flow. These gravel-sandbeds were considered as a density-layered flow depositsby Benvenuti (2003), though Kim and Chough (2000) havepreviously interpreted overall features of inverse grading,high clast content and clast imbrication as originated by acohesionless debris flow.

Facies Gc: Cross-bedded gravelstone(Figure 4e,f)

The Facies Gc has a thickness of 40-100 cm and iscomposed of granule- to cobble-size clasts aligned incrossbeds at angles between 15o-25o. The beds usuallyshow normally graded foresets with planar geometry(Figure 4e,f). In Tanjung Sekakap area, the facies passesvertically to Facies Gs-2 or Gn-i with rather amalgamatedcontacts (lithological logs 03 and 05, Figure 6). Accordingto Miall (1977) the Facies Gc can be formed due tomigrating gravel bars such as transverse or linguoid barsor channel-fills. Dickie and Hein (1995) inferred the gradedto cross-bedded gravelstone as bed load deposit on theslip face of a linear-crested gravel dune or small bar foresetduring high velocity flow in coastal fan delta depositionalenvironment. Meanwhile, Hwang et al. (1995) suggestedthat the Facies Gc might be resulted from progradation ofa Gilbert-type microdelta towards shallow marineenvironment.

Facies Ss: Stratified sandstone (Figure4g,h)

The Facies Ss is characterized by thin to moderatebeds (30 – 100 cm) of fine- to coarse-grained sandstone,typically reddish in color. The beds show poor normalgrading from coarse sandstone to the very fine sandstone.They have sharp to amalgamating contacts with adjacentbeds and are commonly incised by pocket or channel filledbreccias (Figure 4g,h). Facies Ss is predominant in theupper part of Tanjung Sekakap lithological log 03 and 05and in the upper part of Tanjung Murau lithological log 09associated with facies Gs-2, Gc and Gn-I (Figure 6). Forthe Korean Doumsan Fan Delta, Chough et al. (1990)interpreted Facies Ss as product of low-density turbiditycurrents, whereas for the Canadian Jurassic Laberge GroupFan Delta, Dickie and Hein (1995) suggested that FaciesSs were deposited as a product of upper flow regimetractive transport of sand grains. In the Miocene PohangBasin of Korea, pocket or channel filled breccias in theFacies Ss were inferred by Hwang et al. (1995) as a small-scale down-slope running chutes on a steeply inclinedslope.

Facies Sm: Massive sandstone (Figure5a,b)

The massive sandstone facies is moderate to thicklybedded (commonly 60-120 cm) with typical reddish colorand consisting of moderate to well sorted, fine- to coarse-grained sandstone. The grains are angular to sub-rounded.Some layers exhibit normal grading with sharp basalcontacts. Some horizons contained numerous trace fossils(Figure 5a,b) such as those found at Tanjung Sekakaplithological logs 03 (Figure 6). The Facies Sm is commonlyassociated with the Facies Ss. For the Doumsan Fan Delta,Chough et al. (1990) interpreted the Facies Sm as possiblyresulting form high- or low-density turbidity currents, whileKim and Chough (2000) interpreted its deposition aspossibly resulted from amalgamation of recurrent flows.

Facies Mh: Homogenous mudstone(Figure 5c,d)

The Facies Mh is found only in Tanjung Sekakaplithological log 04 (Figure 6) and is typically composedof structureless reddish mudstone to sandstone. The bedshave a thickness range between 50 cm to 2.5 m. Scatteredpebble clasts sometimes occur within the mudstoneintervals. In the Korean Doumsan Fan Delta, Chough etal. (1990) suggested that this facies was deposited by thesettling of suspended sediments on floodplain or inter-channel areas. However, according to Kim and Chough(2000) scattered pebble clasts are also found within a mixeddeposit of the same fan delta, which they interpreted asdeposits representing thick muddy debris flows.

FACIES DEVELOPMENTAnalyses on facies development were conducted from

nine lithological logs representing various coastal exposurein the Tanjung Murau and Tanjung Sekakap area (Figure6) supported by data from several shorter lithological logsand observation on smaller outcrops in the inland. A modelfor lateral facies development (Figures 7,8) was constructedin order to understand the development of sedimentaryfacies along the Tanjung Sekakap - Tanjung Murau section.

In general, the lower part of the lithological logs inTanjung Sekakap and Tanjung Murau are dominated bybreccia-rich facies (Facies Bd and Bs), attaining amaximum thickness of about 20 m and may also re-appearin the upper part of the lithological log 05 in Sekakap area(Figure 6) in association with the Facies Gc. In the middleof the succession, normally gravelstone-rich facies (FaciesGs-1 – Gd, or Gs-2 – Gd) are more dominant, reaching atotal thickness of up to 60 m in the Tanjung Sekakap areaand up to 40 m in the Tanjung Murau area. The sandstone-rich facies generally dominate the upper part of thesuccession mainly in the Tanjung Sekakap area. In theTanjung Murau area, succession of the Facies Gs-1 – Gd,or Gs-2 – Gd are noted mostly along the coastline. The



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sandstone-rich facies form more than half of thelithological sequences in the Tanjung Sekakap lithologicallogs 03 and 04 (Figure 6), associated with Facies Ss – Gs-2 and sometimes Ss – Gn-i. The Facies Sm and Mh onlyoccur locally in the sandstone succession found in TanjungSekakap lithological log 04 (Figure 6).

The lithological logs (Figure 6) clearly indicate thatthe successions commenced with breccia dominated facies,followed gradually by gravelstone, sandstone andmudstone dominated facies, before the return to coarse-grained breccia at the top of the succession. The mostcomplete sedimentary facies development can be observedin the Tanjung Sekakap lithological logs 02-05. However,details in lithological log 03 (Figure 6) show several finingand coarsening upward sequences, though the faciessuccession shows a general coarsening upward fromsandstone-dominated facies to the gravelstone-dominatedfacies especially towards the top of the succession.

In the Tanjung Murau area, only the breccia- andgravelstone-rich facies are well developed, thus thegradation to the sandstone-rich succession is poorlyestablished. The uppermost part of the facies successionin Tanjung Murau is perhaps only equivalent to that of themiddle part of Tanjung Sekakap succession. The totalthickness from coarser facies (Facies Bd-Bs) to finer facies(Facies Gs-2-Ss-Sm) in Tanjung Murau is fairly similar tothat of Tanjung Sekakap, but is significantly lesser inSekakap lithological log 02 (inland Sekakap).

The modern Yallahs Fan Delta described by Wescottand Ethridge (1980), the Pliocene Esperituro Santo FanDelta described by Postma and Roep (1985) and theMiocene Doumsan Fan Delta described by Chough et al.(1990) and Hwang et al. (1995) are chosen as provisionalmodels for comparing the facies development of the Muraurudrock unit. These rudrocks exhibit close resemblance interms of their facies and facies association, and thus shouldshare a common depositional setting and processes, asdiscussed in the next section.

FACIES ASSOCIATION ANDDEPOSITIONAL ENVIRONMENT

Facies association is generally used to determine thedepositional environment as single facies often occurs inseveral depositional environments. For example, the thickrudrock dominated by cobble-pebble clasts withoutapparent internal structure such as in facies Bd or Bs ofthis paper, have been commonly interpreted as debris flowdeposits (Wescott & Ethridge, 1980; Lowe, 1982; Postma& Roep, 1985; Coussot & Meunier, 1996; Chough et al.,1990; Kim & Chough, 2000; Benvenuti, 2003). Debrisflow, on the other hand, could be developed in variousenvironmental conditions from sub-aerial (Wescott &Ethridge, 1983) to transitional (Benvenuti, 2003) as wellas deep-water environments (Walker, 1975, 1978; Visser,1983). The facies, could formed on any fan topographysuch as on alluvial fan, fan-delta or even submarine fan.

In this case, facies associations are vitally important forinterpreting the fan type and hence the whole depositionalenvironment.

Three major facies associations were identified in theMurau rudaceous rocks. They are alluvial fan (AF),Gilbert-type topset – foreset fan delta (GTF) and Gilberttype-topset fan delta (GT). The determination of each faciesassociation is based on the co-occurrence of inter-relatedfacies in terms of their sedimentary textures, depositionalprocesses and possible depositional sub-environments. TheMurau rudrock facies associations were designated basedexcellent works on similar rudrock by Chough et al. (1990)for the Miocene Doumsan Fan-Delta in SE Korea, Hwanget al. (1995) for the Miocene Pohang Fan-Delta system,also in SE Korea and Benvenuti (2003) for the Pliocene-Pleistocene lacustrine fan-delta in Central Italy, amongothers. The composition of Murau rudrock faciesassociation and its interpretation are summarized in Figure6.

Alluvial Fan Facies AssociationChough et al. (1990) interpreted the disorganized

breccia of the Doumsan Fan Delta in Korea as beingdeposited by alluvial fan systems where debris flows aredominant. In this study, such facies association isrepresented by the disorganized boulder-cobble supportedbreccia facies (Facies Bd) and the crudely stratified cobble-boulder-rich breccia facies (Facies Bs). Angular clasts andclast composition that are similar to the underlying rockssuggest a close source, shortly transported down a steepslope to form the basal conglomerate (Figure 8) as seen inTanjung Murau and westernmost Tanjung Sekakap. Thisinterpretation supports the earlier depositional modelreconstructed by Ibrahim Abdullah et al. (1991) whosuggested that the sedimentation process is controlled bya normal fault tentatively named as the Bukit Keluang-Murau Fault. The thick breccia and gravelstone depositsassociated with alluvial fan and Gilbert-type foreset totopset facies at Tanjung Sekakap and Tanjung Murau werepossibly formed due to the basin infill with sedimentationrates almost similar to the subsidence.

For the Murau rudrock, the alluvial fan depositionalenvironment is represented by the whole of Tanjung Muraulithological log 07 and the bottom parts of Tanjung Sekakaplithological logs 02 and 05 (Figure 06). Based on theirthickness, the alluvial fan in Tanjung Murau lithologicallog 07 and in Tanjung Sekakap lithological log 05 seem tobe relatively larger than that of the Tanjung Sekakaplithological log 02.

Gilbert-Type Topset-Foreset FaciesAssociation

A possible Gilbert-type topset-foreset faciesassociation is seen in the lower part of lithological log 09at Tanjung Murau and middle part of lithological 05 atTanjung Sekakap (Figure 6). These sections are dominated



by disorganized gravelstone (Facies Gd), crudely stratifiedgravelstone (Facies Gs-1 and Gs-2) and cross-beddedgravelstone (Facies Gc) that were possibly formed on boththe Gilbert-type topset or foreset fan delta (Chough et al.,1990, Hwang et al., 1995). The Gilbert-type foreset fan-delta is best characterized by the presence of steeplyinclined beds (initial slope between 20o-25o) ofdisorganized and crudely stratified gravelstone (Facies Gd,Gs-1 and Gs-2). In the Murau rudaceous rock, the initialslope is difficult to be determined due to the presence ofextensive faulting and folding throughout the studiedsections of the formation. The present interpretation is onlybased on the above facies association, which is bestexhibited in the middle part of lithological log 05 andbottom part of lithological log 09 (Figure 6). Within thisfacies succession, Facies Gd, Gs-1 and Gs-2 are closely

Figure 6. Lithological logs from representative outcrops between Tanjung Sekakap and Tanjung Murau and their faciesassociations. A – Distribution of lithological log and observation localities. B-G – Lithological logs at localities 02, 03,04, 05,07 and 09. [AF – Alluvial fan. GTF – Gilbert-type topset – forseset fan delta. GT – Gilbert-type topset fan delta].

related to the Gilbert-type foreset delta and are intercalatedwith Facies Gc, which is usually interpreted as Gilbert-type topset deposits. Therefore, as a whole, the bestpossible facies association of the mention facies successionis the Gilbert type foreset – topset (GTF). The possibledepositional environment of such facies association is inthe transitional or shallow marine environment, withinwhich Hwang et al. (1995) interpreted the progradationof river mouth bar or lobe to shallow marine environmentand progradation of Gilbert-type microdelta to shallow-marine environment has occurred.

Gilbert-Type Topset Facies AssociationThe Gilbert-type topset facies association is developed

in the upper part of lithological log 09 (Tanjung Murau)

Figure 5. Some typical facies developed in Tanjung Sekakap - Tanjung Murau rudaceous rocks: photographs (left column) andschematic sketches (right column). a,b – Facies Sm: Massive sandstone; c,d – Facies Mh: Homogenous mudstone.


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and the upper part of most lithological logs in TanjungSekakap (Figure 6). This association is represented by theFacies Gc, Gn-i and Gs-2 (cross bedded-, normally-inversely- and crudely stratified pebble-rich- gravelstone)as well as the stratified sandstone facies (Facies Ss).According to Chough et al. (1990), the alternation of FaciesSs and layered or channelized breccia indicates lateralgrading of breccia dominated small alluvial fans into alarge-scaled stream dominated alluvial fan. Thissedimentary process resulted in migrating gravel bars andsecondary channel fills, eventually forming disorganizedand cross-bedded gravelstones (Miall, 1977). Chough etal. (1990) interpreted that these processes possibly occurin a shallow marine environment within a Gilbert-typetopset environment. The interpretation of shallow marinedepositional environment is supported by the presence ofbioturbated sandstone (Facies Sm) as observed in TanjungSekakap. This particular bioturbated sandstone representsbrackish or shallow marine sediments (Chough et al.,1990).

Wescott and Ethridge (1980) mentioned that a Gilbert-type topset sediments are mainly deposited by channelshifting and possibly also as a part of alluvial fan, braidedstream systems. The occurrences of homogeneousmudstones (Facies Mh) are indicative of flood plaindeposits. The presence of clustered clasts in the mudstone(Facies Mh) as seen at Tanjung Sekakap probably resultedfrom traction movement, associated with the waning ofturbulent debris flow (Kim et al., 1995). The debris falldeposits were probably supplied from the upper slope,intermittently exceeding the reposed angle.

A possible lateral repetition of the sequence startedfrom the southeast (Tanjung Murau) where proximal faciesassemblages are prominent, to the northwest (TanjungSekakap), which represents distal facies of the fan complexforming several lobes of fan-delta system (Figure 7). Mostof the delta and alluvial fan lobes show that the source ofsediments came from the south-southwest and the basin isrelatively deeper to the north-northeast (Figure 8). Thecomplete basin-ward lateral facies development, however,cannot be observed as only part of the sequence is exposedat the present erosion level.

Murau Basin developmentSub-aerial alluvial, transitional delta and deep-water

sub-marine fans are all special depositional environmentsdeveloped on foot slopes commonly found along scarpsof normal fault. Normal faults are common feature ofextensional tectonics, often associated with the formationof horst and graben topography. The latter provides bestpost-tectonic depositional environment especially forcoarse-grained sediments. As for this study case, the Muraubasin was interpreted by Ibrahim Abdullah et al. (1991)as a half graben resulted from the development of a localnormal fault referred as the Murau fault. This fault wasthought to be part of the more regional North-South

trending Murau-Bukit Keluang fault, extending from BukitKeluang area in North Terengganu to Tenggaroh area inEast Johor. The exact timing for the faulting and the fillingof the basin is still uncertain, but it is most likely olderthan the neighbouring Middle Permian Sedili Volcanicsince there is apparently lack of volcanic clast in theresulting breccia of Murau Conglomerate.

In east Johor, the oldest rock unit i.e. the MersingFormation was deposited in a relatively shallow marineenvironment. Subsequent tectonic event has turned thesesedimentary rocks into a low to medium grademetamorphic rocks prior to the formation of the Murauhalf graben basin. The initial basin filling by alluvial fanand part of the following delta fan was thought to havetaken place concurrent with the subsiding of the basin,hence while the fault is still relatively active. As a result,thick succession of rudaceous rock with clasts mainlyoriginated from the bedrocks was formed withinreasonably short time span. Stratigraphically, thedevelopment of Gilbert-type topset-foreset delta fan

Figure 7. Murau rudrock facies associations and lateral faciesdevelopment. AF – Alluvial Fan. GTF – Gilbert-type topset –foreset fan-delta. GT – Gilbert-type topset fan-delta.

Figure 8. Depostional Model for fan-delta sequences asinterpreted for the Murau rudrock outcrops.



deposit over the alluvial fan deposit marked prominentchanges of palaeoenvironment from sub-aerial to shallowmarine, while the succeeding Gilbert-type topset delta fanindicated that the basin is eventually shallowing and filledup completely.

CONCLUSIONSDue to dominance of rock chips and angular clasts

within it, the rudaceous rock sequence in Tanjung Sekakap– Tanjung Murau area should be classified as a sedimentarybreccia rather than conglomerate. The Murau breccias area sequence of rudrocks deposited within a complex seriesof alluvial fan, topset-foreset and topset Gilbert-type deltasystems. The Murau rudaceous rocks were depositedwithin a half graben basin controlled by subsidence ofMurau faulted block. The sediment source is mostlyderived from the underlying pre-Permian bedrock ofMersing Formation consisting of schist, phyllite andquartzite. The rudrock deposition is dominated by a fluvialsystem controlled by slope gradient and debris-turbiditesand fluvial developments on the fan-delta system within acontinental margin environment. The absence of basinplain, slope apron as well as pro-delta associated faciesand the dominance of shallow water – sub-aerialtransitional facies association is probably due to unstablecondition resulting from active subsidence duringsedimentation. The repetition of facies succession in theMurau rudrocks probably represents multiple lobes of afan-delta system with sediment sources derived from thesouth-southwest. The Murau Conglomerate is probablycorrelatable with some other genetically similar latePalaeozoic conglomerate units dominating the coast andoffshore of Terengganu such as the Bukit Keluang, Redangand Pulau Kapas Conglomerates.

ACKNOWLEDGEMENTWe wish to thank the Malaysian Ministry of Science,

Technology and Environment for granting the IRPA 02-02-02-0012-EA186 under which the field and laboratoryworks were carried out. Many thanks are also due to staffof Geology Programme UKM for their help at variousstages of this research.

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