12th GEOSEA 2012, Bangkok, Thailand
Geology and Stratigraphy of the Gerik Formation Mat Niza bin Abdul Rahman1, Doungrutai Saesaengseerung1 and Suvapak Imsamut3 Technical Services Division, Minerals and Geoscience Department Malaysia, Sultan Azlan Shah Road 31400 Ipoh, Perak, Malaysia 2 Bureau of Fossil Protection, Department of Mineral Resources, Rama VI Road, Bangkok 3 Bureau of Geological Survey, Department of Mineral Resources, Rama VI Road, Bangkok 10400, Thailand 1
E-mail: 1mniza@jmg.gov.my
ABSTRACT
The objective of this paper is to revise the Grik tuff in term of name and its stratigraphic position based on field evidences gathered during the Malaysia-Thailand Border Joint Geological Survey Project jointly undertaken by the Minerals and Geoscience Department Malaysia and the Department of Mineral Resources Thailand. The term Gerik Formation is proposed to replace the term Grik tuff introduced by Jones in 1970 that was believed of Middle Ordovician to Early Silurian in age but without any fossil evidence. Current investigation showed that the Gerik Formation is represented by sequence of pyroclastic and sedimentary rocks that is well exposed in the Gerik area, Upper Perak, Malaysia. The rocks comprise predominantly tuffs of rhyolitic to rhyodacitic composition with subordinate tuffaceous sandstone, limestone, calcareous shale, schist, phyllite and pelagic chert. Anisopyge sp. and Phillipsia sp. (trilobite) were discovered in the calcareous shale and Chonetid (brachiopod) was recorded in the shale. Radiolarian of Follicucullus scholasticus, Albaillella levis, Hegleria mammilla, Latentifistula sp., Triplanospongos sp. Gustefana sp. and others had been discovered in the chert. The fossil assemblages indicated that the age of Gerik Formation is Permian.
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