Notes on Singapore Geology_Hand Out_PDF

Notes On Singapore Geology

Notes On Singapore Geology Naing Maw Than ([email protected] ([email protected]))

Content I) The Geological Formations in Singapore II) A Brief Description of Formation III) Stratigraphy 3.1.Stratigraphy of the Paleozoic Geology in Singapore (542 – 251 m.y) 3.2.Stratigraphy of the Mesozoic Geology in Singapore (251 – 65 m.y) 3.3.Stratigraphy of the Cenozoic Geology in Singapore (65 m.y- Present) IV) Tectonic History and Structures References I) The Geological Formations in Singapore Ten separate formations are recognized in Singapore. 1) Sajahat Formation (S) Lower Paleozoic (Upper Paleozoic/Triassic ?) 2) Gombak Norite (GN) Lower Paleozoic 3) The Paleozoic Volcanics (PV) as Same age of (S) 4) Bukit Timah Granite (BT) Lower to Middle Triassic 5) The Jurong Formation (Upper Triassic to Lr-Mid Jurassic) 6) Fort Canning Boulder Bed FCBB (Late Cretaceous Age) 7) The Older Alluvium (late Tertiary to early Mid-Pleistocene) 8) The Huat Choe Formation (HC) Early to Mid Plieistocene 9) The Tekong Formation (T) Mid Holocenc 10) The Kallang formation (K) Late Pleistocene (1.5 m.a) to Present Marine Member (Km) Alluvial Member (Ka) Littoral Member (Kl) Transitional Member (Kt) Reef Member (Kr)

1


Cross section of the Central to East of Singapore

Jurong Fm. Fort Canning Boulder Bed

195 m

Kallang Fm. Old Alluvium

Bukit Timah Granite & Gombak Norite

0

10 Km

Data from Geology of Singapore (2009)

2


II) A Brief Description of Formation Paleozoic 1. Sajahat Formation (S) Lower Paleozoic (Upper Paleozoic/Triassic ?) Variable metamorphosed sedimentary rock, quartz, sandstone, and argillite found on Pulau Sajahat and Sajahat Kachil, north of Pulau Tekong.

2. Gombak Norite (GN) Lower Paleozoic Noritic and gabbroic rock in central Singapore and as part of the Ophiolite suite of the Lr Pz geosyncline. But, it could be younger if GN is interpreted as basic differentiate of Triassic magma.

3. The Paleozoic Volcanics (PV) as Same age of (S) Partially metamorphosed volcanic agglomerates unit of andesitic fragments, ash and tuff in eastern Singapore, Pulau Tekong.

Mesozoic 4. Bukit Timah Granite (BT) Lower to Middle Triassic Granite, Granodiorite, Norite, adamalite The BT was emplaced by two phases that can be grouped Older acid group assumed to be a cooling phase and slightly younger basic group seem cutting the older Acid dykes. Both groups cut older formations. 5. The Jurong Formation (Upper Triassic to Lr-Mid Jurassic) Sandstone, Silts, Mudstones, conglomerate and Limestone with various metamorphism (Shale, Slate, Marble) It overlies the granite though contact is never seen that can be divided seven facies deposited in terrestrial, transitional and shallow marine. Seven Facies : (Queens Town, Jong, Ayer Chawan,Pandan, Rimau, St.John, Tengah) Volcanics of tuff, spilitic lava, dykes are contemporaneous with the formations. The Murai schist is a product of dynamic metamorphism within the formation found as a zone of well developed cleavage in rocks at Pasir Laba ridge and within Jong facies.

6. Fort Canning Boulder Bed FCBB (Late Cretaceous Age) (known as S 3, Boulder Clay or Boulder bed) Small Colluvial deposits of boulders in soil matrix (hard, Silty Clay & weathered rocks derived from the Jurong Fm.) lied on the Juorng Fm. at central districts and downtown of Singapore. It could have probably deposited when the Jurong formation was deposited and deformed during late Triassic to late Tertiary.

3


Cenozoic 7. The Older Alluvium (late Tertiary to early Mid-Pleistocene) The OA is composed of Fluvio-Deltaic sediments. The upper section is completely weathered CLAY and Lower section is Silty to Clayey Sand, coarse, angular, poorly lithified, quartzo feldspathic with some layers of pebbles. Block faulting and renewed movement along the pre-existing faults resulted downwarp occurred and trough was back filled with fluvial sediments with some embayment sediments. It lies unconformably on older rock units or in fault contact with them. 8. The Huat Choe Formation (HC) Early to Mid Plieistocene The kaolin rich clay in fault controlled depression formed as small lacustrine deposits unconformably on the Jurong Fm. 9. The Tekong Formation (T) Mid Holocenc Coastal terrace deposits with marine and littoral area, unconsolidated sand with some cobbles. Its upper surface is lying at elevations ranged (3.6 to 6.5m) above present sea level. 10. The Kallang formation (K) Late Pleistocene (1.5 m.a) to Present It consists of both marine and terrestrial deposits that is found in onshore incised river valleys, offshore and coastal areas. The Kallang Formation Marine Member (Km) Alluvial Member (Ka) Littoral Member (Kl) Transitional Member (Kt) Reef Member (Kr) 10.1. Marine Member (Km)* Dominantly blue grey, clayey Mud, Sandstone, peat, Unconsolidated but slightly consolidated beds occur 10.2. Alluvial Member (Ka) * A variable terrestrial sediments ranged from pebbles beds

through Sand, muddy Sand and Clayey

to Peat. It is usually unconsolidated to consolidated. F 1 granular, F2 non-granular 10.3. Littoral Member (Kl) * Well sorted unconsolidated beach Sand and near-shore quartz Sand with minor lateritic, shell and lithic fragments, iron-cemented beach rock 10.4. Transitional Member (Kt) Unconsolidated black to bluish grey estuarine mud, muddy Sand or Sand withsome high organic content and peat layers 10.5. Reef Member (Kr) Coral, unconsolidated calcareous Sand and lesser quartz, ferruginous and lithic sand (*possibly part of other members and Tekong Fm.)

4


III) Stratigraphy In this context, presents with distributions, age, geological setting and occurrences, collected samples on site and core samples, some available cross-sections and developments.

3.1) Stratigraphy of the Paleozoic Geology in Singapore (542 – 251 m.y)

Distribution of Singapore’s Paleozoic Rocks (K.W. Lee, 2010)

Paleozoic Volcanics : Upper Paleozoic Gombak Norite, Sajahat Fm. : Lower Paleozoic The Sajahat Fm. is a metamorphosed sedimentary deposits of quartzite, quartz sandstone, and argillite intruded by acid and basic dykes. It is given a Lower Paleozoic age, b ut it could be upper Paleozoic age of the pink porphyritic granite from Pulau Sakudu were Cretaceous granite. The Gombak Nprite is geographically separated from The Sajahat Fm and the Paeozoic Volcanics. It is given a Lower Paleozoic age as it probably represents a part of the ophiolite suite of the Lower Paleozoic geosyncline, but it would however be younger if the Gombak Norite is interpreted as a ‘basic differentiate’ of the Triassic granite magma. The Paeozoic Volcanics comprises metamorphosed volcanics agglomerate with andesite fragments, andesitic ash and tuff. It is mapped as overlying the SJh Fm. and thought to be Upper Paleozoic or correlation with similar rocks in Malay. It is however possible that the SJh Fm. and PZ Volcanics are of the same age.

3.1.1 ) The Sajahat Formation and Paleozoic Volcanics Geological setting of the Sajahat and Paleozoic Volcanic rocks in Singapore

(K.W. Lee,2010)

5


3.1.2) The Gombak Norite Geological setting of the Gombak Norite in Singapore (K.W. Lee,2010) Microgranite Dykes

Dolerit e

Noritic Gabbr

Ophiolitic

Roots of Basic

A

Bukit Gombak Norite in closed view A as later intrusion (courtesy of Dr.Kyi Khin)

3.2) Stratigraphy of the Mesozoic Geology in Singapore (251-65 m.y.)

(K.W. Lee, 2010)

6


3.2.1) Bukit Timah Granite Bukit Timah Granite and Sakudu Granite rocks in Singapore (K.W. Lee, 2010).

Bukit Timah Hill natural reserve and old Quarry The Bukit Timah Graite shows considerable hybridization and much evidence of assimilation within the formation. Inclusion of Gombak Norite in various stages of assimilation, large rafted inclusions of basic rocks, and similar inclusions of rocks of sedimentary origin can be found within the granite. The BKt Granite is assigned to an early to mid-Triassic age by isotope dating. Two phases of dyke intrusions are recognized within granite : a first phase of acid dyke emplacement took place during the final stage of granite emplacement, and a second phase took place shortly after the first phase but before the deposition of the overlying Triassic sedimentary rocks.

3.2.2) The Jurong Formation Facies Distribution of the Jurong Formation in Singapore (k.W. Lee, 2010).

7

Notesical OnCross Singapore Geolo SectionGeology alon East Juron Fairwa

After Chiam et al.

2003 .

The late Triassic to possibly early Jurassic Jurong Fm. overlies the granite although the contact is never seen. Seven sedimentary facies, including one that is charaterised by limestone, are recognised within the formation Volcanics such as tuff, spilitic lava, and dyke rocks are recognised within the formation and are contemporaneous with the formation. The Murai Schist, previously thought to represent the oldest rock in the formation and to have a different origin from the rest of the Jurong Fm. is a product of dynamic metamorphism within the formation. Basin development of the Jurong Formation (After Redding & et al, 1999).

8


3.2.3) Fort Canning Boulder Bed Fort Canning Boulder Bed underlying the Jurong Fm.At along the Fort Canning Rise Depth marked from BGL(RL 121.07m).(Shirlaw & et. al. 2003)

A

Collected Fort Canning Boulders A , the upper half was embedded in Silystone of Jurong Fm. (Shirlaw & et. al. 2003) A cross section of Fort Canning Boulder bed and associated rocks from Raffles City to Raffles Quay showing upper and lower boundaries of FCBB (Shirlaw & et. al. 2003)

The Fort Canning Boulder Bed is a colluvial deposit of slipped material of the Jurong Fm. found in the central business district of downtown Singapore. It was probably laid down in late Cretaceous, but it could also have been deposited anytime between late Triassic (when the Jurong Fm. was deposited and deformed) and late Tertiary (when block faulting occurred and the Old Alluvium first deposited). There was further geological activity in early Tertiary, late Tertiary and early Pleistocene. Block faulting and renewed movement along pre-existing faults resulted. In late Tertiary, a downwarp occurred and the resulting trough was back filled with a coarse sandgravel unit referred to as Old Alluvium. (The base of the OA is below any reasonable base level for erosion associated with Pleistocene low sea levels, and its top may be associated with a minimum high sea level stand of 70m.)

9


3.3) Stratigraphy of the Cenozoic Geology in Singapore (65 m.y – Present)

3.3.3 The Old Alluvium C

A

B

Gullies as ridges and furrows in upper OA Clays A and Cross bedded fine Sand B stacked by another Channel with Coarse Sand C at Bartley Rd.

10


Depositional Variations From Bartley Rd. To Marina South

Bartley Rd RL 120m

Estuarine

OA Clay

12 Km NE

Marina South,

KL Fm.

Bay Line Mcpherson & Up Payaleber Rd

OA

Shelf Area

Naing Maw Than (2010) A bay line (Place where ceased fluvial dominance ) is probably passed at the junction of Upper Payaleber road way and Mac Pherson road. Shore Line : Contact between Coastal Plain and Sea Shelf : Part of the Continental margin between the Shoreline and Continental slope Key points of the OA development The OA was probably dominant by fluvial condition with subordinate marine sediments during Pliocene to Mid-Pleistocene (correlated with Lower Pleistocene Low eustatic sea level). The Kallang river was main channel characterized by low–sinuous braided channels at earlier and hisinuous at later stage caused aggradation, multi-stacked channel deposits. Deposited in faulted trough with repeated vertical movement and small block faulting.

11


3.3.2) The Huat Choe Formation During the period of early Pleistocene faulting, the kaolin–rich clay in fault controlled depression formed as small isolated ponds and lacustrine deposits unconformably on the Jurong Fm.

3.3.3) The Kallang Formation Stratigraphic relationship of Quarternary sediments in Singapore (Bird & et. al. 2003)

Marine Clay

Peaty Clay

F2 : Silty CLAy

F1: SAND

12


Development of The Kallang formation (Upper Quaternary) It consists of both marine and terrestrial deposits that is found in onshore incised river valleys, offshore and coastal areas. The Kallang Formation Marine Member (Km) Alluvial Member (Ka) Littoral Member (Kl) Transitional Member (Kt) Reef Member (Kr) These deposits covers much of the coastal plane The most important unit is Marine Member that covers one quarter of Singapore with variable thickness with a maximum record of 35m. It comprises upper and lower part. The Marine Clay is pale grey to dark blue i n colour, soft, silty, kaolinite-rich and shell fragments. The low sea levels associated with the penultimate glacial (Riss) stage. Rivers downcut their valleys to at least –55m. As sea level rose following glacial Riss stage about 14,000 BP, the lower member was deposited (Bird et al. 2003). The transitional member (Kt) and the Littoral memebr (kl) were deposited near the shore line and the Alluvial member was deposited in river valleys on shore. When the sea level stood at – 120m during the last Glacial Max at about 20,000 BP stiff, reddish brown clay F2 was developed at the top of the lower member. vegetation grown on F2 layer and became Peat layer E that was in turn capped with sandy, shallow water deposits F1 Sand. At the end of the last Glacial Max (during the closing phase of the last glacial Wurn stage), sea level rose rapidly and Singapore was flooded when it was about –25m at about 10,000 BP. The Transitional (Kt) and Littoral (Kl) members were deposited repeatedly near advancing shoreline with similar facies of Tekong formation. Further offshore, the Upper Marine Member was deposited over the Transitional and Littoral Member, and onshore,the Alluvial Member was deposited. The sea level stand at about 2 to 2.5m above present sea level at 6,000 BP allowed the deposition of Tekong Formation. Since 6000, sea level declined steadily to the present and Upper Marine Member was overlain by the Alluvial Member and transitional Member.

IV) Tectonic History and Structures The Paleozoic sedimentary structures indicate a longer and more complex tectonic history. The intrusion and uplift of the granite presumably started in the Upper Paleozoic and become strongly evident in the Triassic time.

13

Notes On Singapore Geology The Triassic sediments were laid down in a mobile N_W trending trough bounded on either side by rising granitic hills (coarse clasts in sedimentary rocks suggests the bulk of the granite was buried at the same time). The rate of uplift of the main range granite in the SW of trough appears to have been more rapid. This lopsided uplift caused the trough and tilt NE and gave way sediments against the uplift of Bukit Timah granite. The dynamic metamorphism that gave rise to Murai schist accompanied with this sliding and assumed that Malay penisular was raised above sea level from that time. Alternatively, the Triassic sediments of Jurong Formation could have been uplifted, tilted, dislocated, piled on top of one another in late Cretaceous when the Wyola continental fragment collided with the east Malaysia block that may caused the Fort Canni ng Boulder Bed. That was also widespread shallow thrust faulting, shallow folded and metamorphism such as slates, phyllites, and schistose sandstone at many locations away from Murai Schist. Tectonic activity recommended the late Tertiary with block faulting and warping. The Old Alluvium and Huat Choe Formation were deposited in the depression that had formed. After the cessation of warping, river valleys were cut in the Old Alluvium and older rocks. The valleys and coastal areas are subsequently backfilled with sediments of the Kallang Formation during late Pleistocene and Holocene. During mid-Holocene, coastal area were covered with Tekong Formation and The Kallang Formation continue to be deposited except the Lower Marine member in present day. SE Asia Basins and Tectonic Frameworks

14


References: 1. Bird M.J., J.N.Shirlaw & et.al. The Age and Origin of quaternary Sediments of Singapore with emphasis on the Marine Clay , Proceeding of Underground Singapore 2003, Engineering Geology Workshop 2. Chiam.S.L., K.S. Wong & et.at., The Old Alluvium , Proceeding of Underground Singapore 2003, Engineering Geology Workshop 3. DSTA, Geology of Singapore (2nd Ed, 2009) 4. Lee K.W. & et.at Limestones of the Jurong Formation , Proceeding of Underground Singapore 2003, Engineering Geology Workshop, 5. J.J. Lambiase. Lecture Notes on Reservoir Sedimentology (Universiti Brunei, 2005) 6. K.S.Wong & et al. Old Alluvium Engineering Properties and Braced Excavation Performance, Proceedings of Underground Singapore 2001 7. Lee kim Woon, SRMEG_GEOSS Workshop on Geology of Singapore 5th April 2010 8. Moe Sein, J.C.W. Ong & et al. Buried Granite Ridges in Old Alluvium Proceeding of Underground Singapore 2003, Engineering Geology Workshop 9. Naing Maw Than,The Occurrences of Old Alluvium , Singapore (presented at MGSS 1st technical Seminar, June 2010) 10.Shirlaw J.N. & et.at., Fort Canning Boulder Bed , Proceeding of Underground Singapore 2003, Engineering Geology Workshop

15

Notes on Singapore Geology_Hand Out_PDF

Recommend Documents