ISSN / EISSN : 0126-5539 / 2682-7549
Published by: Geological Society of Malaysia (10.7186)
Total articles ≅ 46
Latest articles in this journal
Warta Geologi, Volume 47, pp 126-127; https://doi.org/10.7186/wg472202104
Metamorphic rocks of Sarawak have been dated and are not Upper Carboniferous or older rocks nor are they correlatives of the Pinoh Metamorphics of Kalimantan. Two newly-dated rocks are Triassic and are named the West Sarawak Metamorphics and a third sample is Cretaceous.
Warta Geologi, Volume 47, pp 103-112; https://doi.org/10.7186/wg472202101
Karlahi is largely underlain by granites and migmatites gneiss of the Adamawa Massif. The area lies west of Benue Trough and east of Cameroon volcanic line. The aim of this paper is to determine hydraulic properties of water bearing layer using parameters derived from Dar-Zarrouk equation and characterized them into groundwater potential zones. The resistivity values of the weathered and slightly weathered layers which make up the water bearing layers were added and an average was taken and used as the resistivity of the water bearing formation in computation of Dar-Zarrouk parameters in Karlahi area. The values of resistivity of water bearing formation ranged from 18 to 4963 Ωm with an average resistivity value of 549 Ωm and the thickness of the water bearing formation ranges from 21 to 32 m with an average thickness of 24.5 m. Conductivity values range from 0.000201 to 0.05509 (σ) while the longitudinal conductance range from 0.00483 to 1.2363 Ω-1, the transverse resistance ranges from 407 to 123504.3 Ωm2. The hydraulic conductivity and transmissivity values range from 0.14 to 25.87 m/day and 3.28 to 580.4 m2/day respectively. The longitudinal conductance values in Karlahi area revealed poor to good with an average longitudinal conductance value that is moderate. High transverse resistance values are located in the central and southern part of Karlahi area while low values are located in the eastern part. The spatial distribution map of transmissivity in the area revealed moderate to high transmissivity values in the north central part and a negligible to low transmissivity in southern part, extreme northeastern part. The groundwater potential map of Karlahi area shows negligible to weak potential groundwater zones in SW and SE, moderate potential in the central to northern part of Karlahi area.
Warta Geologi, Volume 47, pp 122-125; https://doi.org/10.7186/wg472202103
The sketching of geological features and objects played an important role in the development of the geosciences. Geological sketches may not be as commonly used for documentation purposes any longer, but may facilitate learning and understanding. By sketching geological features, the eye is trained to observe; this furthers understanding, and so improves study results.
Warta Geologi, Volume 47, pp 113-121; https://doi.org/10.7186/wg472202102
Three broad morphological zones can be differentiated at the weathering profile; the top, 3.80 m thick, pedological soil (zone I with sub-zones IA, IB and IC) comprising soft to stiff, brown clays and the bottom bedrock (zone III) being an outcrop of vesicular olivine basalt. The intermediate zone II (saprock) is 1.12 m thick and consists of brown, very stiff, sandy clayey silt with many lateritic concretions. Laboratory constant head permeability tests show the saturated hydraulic conductivity (Ks) to vary with depth; sub-zone IB having a conductivity of 0.007 cm/hr, and sub-zone IC (saprolite), and zone II (saprock), having conductivities of 0.147, and 0.447, cm/hr, respectively. The conductivity values show no correlation with physical properties of the earth materials, but increase with increasing sand, gravel, and silt, contents. The conductivity values also decrease with increasing clay and colloid contents. The low hydraulic conductivity of sub-zone IB will lead to surface runoff and ponding over natural ground surfaces during rainfall events, though over disturbed ground surfaces, infiltration is anticipated in view of exposed saprolite and saprock earth materials with relatively high conductivity
Warta Geologi, Volume 47, pp 19-28; https://doi.org/10.7186/wg471202103
The entitlement of a coastal State over the seabed and subsoil in front of its landmass is provided for in the United Nations Convention on the Law of the Sea 1982 (UNCLOS), in particular Article 76 for the continental shelf. This short note in Malay gives a brief introduction to the concept of the “continental shelf” in the context of Article 76. This concept is important as a means by which coastal States may establish the outer limit of their continental shelves beyond 200 nautical miles (M) measured from the territorial sea baselines. Once the outer limits have been established, coastal States are then able to exercise with certainty their sovereign rights over the extended continental shelf for the purposes of exploring and exploiting the natural resources of the seabed and subsoil, as provided for by UNCLOS. The establishment of the outer limits of the continental shelf beyond 200 M is based on the principle of natural prolongation of land territory in Article 76. Geology also plays an important role in the process of determining the extent of the prolongation in accordance with the provisions of Article 76. For authors and students of this topic in Malay, it is proposed that the synonymous Malay terms for continental shelf – “pelantar benua” and “pentas benua” – be given specific meanings for use in their legal and geological contexts, respectively.
Warta Geologi, Volume 47, pp 1-8; https://doi.org/10.7186/wg471202101
The main Beris Dam is founded on a sequence of thick bedded conglomerates and pebbly to fine grained sandstones with minor mudstone mapped as the Semanggol Formation of Triassic age. Ultrasonic pulse measurements show velocities of compressional and shear waves through the sandstones to increase with decreasing grain size; the pebbly sandstone with velocities of 2.210, and 5.171, km/s, and the coarse grained sandstone with velocities of 2.477, and 5.612, km/s, respectively. The medium grained sandstones have compressional and shear wave velocities of 2.457, and 5.793, km/s and the fine grained sandstones, velocities of 2.572, and 5.867 km/s, respectively. Dynamic elastic constants computed from the ultrasonic velocities also increase in values with decreasing grain size; Poisson’s ratio varying from 0.36 to 0.39, the modulus of elasticity from 35.076 to 48.210 GPa, the bulk modulus from 52.260 to 67.362 GPa and the modulus of rigidity from 12.637 to 17.468 GPa. Increasing velocities and elastic constants with decreasing grain size are considered to result from a denser arrangement of constituent grains as shown by increasing dry unit weights. Comparison with the results of an unconfined compression test on a fine grained sandstone indicate that the ultrasonic elastic constants are good approximations of static elastic constants.
Warta Geologi, Volume 47, pp 9-18; https://doi.org/10.7186/wg471202102
Candi Kampung Baru is situated in the Kampung Baru Archaeological Site, and it is one of the temple sites that used bricks as the main construction material. Based on the Global Positioning System, Candi Kampung Baru is located at N 05.58215°, E 100. 38004°. Apart from bricks, granite stones were also used as the pillar base of the construction’s structure. This study is an analytical approach on the pottery properties of clays discovered at the Kampung Baru Archaeological Site. X-ray diffraction (XRD), X-ray fluorescence (XRF) and physical analysis have been performed on these potsherds. 15 pottery shard samples were analysed to determine the chemical and mineralogical characteristics of the pottery shards. The results indicate a local provenance of these samples. The mineral content in the pottery samples also indicate the presence of minerals, such as quartz, illite, datolite and microcline. Furthermore, the physical analysis conducted uncovered a variety of motifs that adorned the earthenware, such as lines, nets, square and floral motifs. The mineral content and physical observation of the pottery shards indicate that the open burning technique was used to produce these pottery shards due to the presence of illite mineral in the pottery shards. The mineral content (namely illite) also shows that the samples were baked at a temperature between 650°C and 750°C. The content of the major and trace elements also proves that these potteries were produced from the same source and it is proposed that local raw materials were used in the production of the potteries, from which the nearest source that could be detected is at the Muda River basin. Moreover, the involvement of the local community in producing the potteries should not be refuted, as this proves that the knowledge of producing pottery by the local community had already started since the evolution of the Neolithic culture at the Muda River basin since 4000 to 5000 years ago.
Warta Geologi, Volume 47, pp 29-48; https://doi.org/10.7186/wg471202104
New outcrops of Paleozoic meta-sediments northwest of Kuala Lumpur expose the deformational effects of the Late Paleozoic-Mesozoic collisions between various Gondwana-derived continental fragments as they amalgamated to form the core of SE Asia. Over a duration of 6 months, beginning in August 2020, we conducted field trips within northern Selangor to new laterally extensive outcrops for field observations, structural mapping and to measure and log the stratigraphic section. This paper focuses on Upper Paleozoic Kenny Hill Formation outcrops in northern Selangor. The most studied is the heavily weathered Jalan Rawang-Bestari Jaya (JRBJ) outcrop, which is characterised by a steeply dipping (southwest), upward-coarsening succession of sandstones and shales interpreted as a system of ephemeral fluvial channels possibly related to Gondwana glaciation. Concretions within bedding planes and fractures were possibly formed around organic material. Less than 4 km to the east, the Scientex development has excavated fresher outcrops of the same rocks dipping to the NE. Metamorphic lineation is not present in either outcrop location. In addition, a monocline is exposed at outcrop location number 3 nearby. Finally, at Bukit Botak, 14 km to the southwest, a system of westward verging thrust faults, back thrusts and normal faults can be viewed and an angular unconformity or decollement marks the contact between the Upper and Lower Paleozoic. These laterally extensive outcrops are rare and are quickly subject to intense tropical weathering, the encroachment of jungle vegetation and urban development. Historic mapping and prior stratigraphic, structural, and petrographic studies have been conducted in the area, but these relied on poor exposures. As suburban development escalates in the area, we hope that new outcrops, featuring multi-dimensional views of these formations, such as the four described in this paper, will complement the earlier work.
Warta Geologi, Volume 46, pp 191-195; https://doi.org/10.7186/wg463202003
An exposure of agate geode and nodules in Mount Conner, Sabah, provides an essential aspect to the geological formation in Semporna. This paper briefly report results from petrography analyses on the agate geode and nodules and its significance to the volcanic rocks and sedimentary rocks formation in Mount Conner. The geode and nodules can be divided into agate, and nodules and most of them are sub-rounded. Nodules are usually small in size and display brownish colour. It commonly occurs in volcanic rocks (dacite and rhyolite) and contained amygdale filled by secondary mineral such as microcrystalline and macrocystalline quartz. In contrast, sedimentary rocks in Mount Conner contain both nodules and geodes, which nodules shows similar characteristic with nodules in volcanic rocks and geodes contained empty vesicles or spaces surrounded by colourless to milky white quartz crystals. Both geode and nodules exhibit conchoidal fracture, while geode shows vesicle features and nodules in volcanic rocks show amygdale texture. The formation of geodes and nodules in Mount Conner might as result of precipitation under low temperature from hydrothermal solution.
Warta Geologi, Volume 46, pp 199-203; https://doi.org/10.7186/wg463202005
Water is a unique property of the Earth and very important to every living organism. The existence of groundwater is only 0.61% of the total water on earth (oceans, rivers, lakes, polar ice, rain). The purpose of this research is to determine the location and depth of the aquifer by using 2D and 3D modeling. The method of research is resistivity method using Schlumberger configuration, where data is collected according to the survey design with coordinate ranging from X:436100, Y:9226880 to X:436680, Y:9227640, and covered by 7 lines. The modeling results indicate that the present groundwater aquifer potential has low resistivity distribution in this area. The spreading of unconfined aquifer is estimated on the north side to the east of Simpang 5 area. This can be seen from syncing the data of line one to six. But the data on line seven is of different patterns with other lines. The existence of groundwater basin is not easily identified on this line. This may be due to the location of Line Seven being located in the area of Ciputra Mall, Horison Hotel and Tlogorejo Hospital with higher consumption of water, thus the decrease in groundwater condition. This may cause conditions such as land subsidence. The results of interpretation based on the modeling show the possibility of an unconfined aquifer with groundwater level at 10-15 m depth with varied end of border groundwater depth.