St-John%20Facies.JPG

Geology of Singapore

Jurong Formation

Jurong Formation is Late Triassic (possibly to Early Jurassic, about 230 to 209.5 Ma., maybe younger?) sedimentary rock, described as red beds. It was divided by Lee and Zhou (2009) into seven facies, spatial relationships between them are uncertain due to scarce exposures and borehole data:

  • Tengah Facies: muddy fine-grained sandstone with occasional conglomerate (rhythmically bedded, each with normal graded, i.e. grain size thinning upwards, possibly deposited by turbidity currents)
  • St. John Facies: mudstone and fine-grained muddy with occasional carbonaceous laminae (rhythmically bedded), shown in the upper photo to the right (St. John's Island)
  • Rimau Facies: quartz conglomerate and quartzite, shown in the lower photo to the right (Siloso Jetty, Sentosa)
  • Pandan Facies: fossiliferous limestone, carbonaceous limestone, micritic and sparitic limestone, occasional dolomite and marble
  • Ayer Chawan Facies: mudstone, often black with shallow marine fossils, tuffaceous sandstone, red conglomerate of volcanic rocks, tuffs
  • Jong Facies: conglomerates and sandstone with occasional mudstone beds and spilite pillows
  • Queenstown Facies (probably the oldest): mudstone, siltstone and sandstones with conglomerates with occasional tuffs

In addition, the Murai Schist was distinguished as an informal unit consisting of the Queenstown, Jong and Tengah Facies which were intensely sheared.

Recently Oliver and Prave (2013) stated non-marine origin of the Jurong Formation. Earlier terrestrial features were observed including coal seams reported on Mt Guthrie and leaf fossils found near Mount Faber (Lee Zhou 2009). Jurong Formation is considered molasse deposits (post-orogenic deposition) which filled half-graben formed by extensional tectonic movements which in the Late Triassic followed the Indosinian Orogeny (Oliver and Prave 2013).

Rimau%20Facies.JPG

Literature

Hutchison C.S. 1973. Tectonic Evolution of Sundaland: A Phanerozoic Synthesis, Geological Society of Malaysia, Bulletin
Lee K.W., Zhou Y., 2009. Geology of Singapore, Defence Science and Technology Agency, Singapore,
Oliver G., Prave A. 2013. Palaeogeography of Late Triassic red-beds in Singapore and the Indosinian orogeny. Journal of Asian Earth Science 76
Pitts J. 1984. A survey of engineering geology of Singapore, Geotechnical Engineering, Journal of Southeast Asian Geotechnical Society 15

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