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John Kuna Raj
Published: 30 August 2021
Warta Geologi, Volume 47, pp 113-121; https://doi.org/10.7186/wg472202102

Abstract:
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
, Robert Hall
Published: 30 August 2021
Warta Geologi, Volume 47, pp 126-127; https://doi.org/10.7186/wg472202104

Abstract:
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.
S.N. Yusuf, J.M. Ishaku, W.M. Wakili
Published: 30 August 2021
Warta Geologi, Volume 47, pp 103-112; https://doi.org/10.7186/wg472202101

Abstract:
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.
Published: 30 August 2021
Warta Geologi, Volume 47, pp 122-125; https://doi.org/10.7186/wg472202103

Abstract:
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.
Hussein Ahmed Hasan Zaid, T.A. Jamaluddin, Mohd Hariri Arifin
Bulletin of the Geological Society of Malaysia, Volume 71, pp 71-78; https://doi.org/10.7186/bgsm71202106

Abstract:
Yemen has harsh natural conditions that increase certain geological processes more than other regions, leading to a variety of geological hazards. Yemen’s typical topography is distinguished by coastal plains of the Red Sea and cliff foothillls, followed by mountains of the Arabian Shield. These types of geological hazards can be classified into slope stability, earthquakes, flash floods and expansive soils. The current literature review presents a description backed with examples of the certain geological hazards in Yemen. The obtained results indicate that further consideration and thought are highly required for semi-arid regions. National and foreign organizations have to collaborate together with other individuals to maintain the adjusted environmental system and reduce the potential geological hazards. Therefore, mitigation measures should be implemented to avoid and minimize these geological hazards.
, Aras 2 Blok D03 Pusat Geokejuruteraan Tropika (Geotropik), Ibrahim Komoo, Edy Tonnizam Mohamad, Ali Ali, Norhayati Ahmad, Mohd. Effendy Abd. Wahid, Mohd Fauzi Rajimin, Universiti Kebangsaan Malaysia Pusat Penyelidikan Langkawi (Ppl), Universiti Malaysia Terengganu Fakulti Perikanan Dan Sains Makanan, et al.
Bulletin of the Geological Society of Malaysia, Volume 71, pp 89-98; https://doi.org/10.7186/bgsm71202108

Abstract:
The district of Mersing is bestowed with many national and international geological heritage sites dated since 350 million years ago. The high biodiversity and uniqueness of the local culture complements the geoheritage of the area. Thus, the National Geopark Committee has chosen Mersing as a territory to be developed as a geopark. Mersing Geopark development efforts were initiated in 2017 through the Mersing Geopark Scientific and Development Committee. The entire Mersing district of 6,371 square kilometers, including the marine areas right up to the Aur Archipelago is identified as the geopark area. The geoheritage here has been identified as 22 geosites, which cover land and island areas. Important flora and fauna have also been identified as being within the protected areas. The unique and preserved traditions of life, art and culture add to the value of this geopark. Several key elements were introduced to prepare Mersing Geopark before being evaluated as a national geopark candidate in December 2018, namely governance of the geopark - management based on ‘co-management’ mechanism, nature conservation – community, community economy through geotourism activities, and public education. Many programmes and activities have been carried out to face future plans for Mersing to become a UNESCO Global Geopark. Geopark enhances natural and cultural heritage resources through integrated development, geotourism development to increase income, preservation of heritage sites and empowerment of local communities to foster a strong sense of pride and belonging to a place.
, National Security Council Malaysian Continental Shelf Project
Bulletin of the Geological Society of Malaysia, Volume 71, pp 23-46; https://doi.org/10.7186/bgsm71202103

Abstract:
In the “flysch” series of the West Crocker Formation (Eocene–Oligocene), Kota Kinabalu, Sabah, trace fossils are fairly common although not ubiquitous. The trace fossils commonly occur as hypichnial semi- or full-reliefs on the sole of thin turbiditic sandstone beds (mainly Bouma Tc division) in the thinly bedded heterolithic sandstone-mudstone facies interpreted as submarine fan lobe deposits. Their presence in mainly the thinly bedded facies of the fan system suggests preferential production and preservation in the fine-grained “distal” parts of the Crocker submarine fan system. Trace fossil assemblages characteristic of the Nereites ichnofacies indicate sedimentary environments mainly in bathyal to abyssal water depths (>2000 m). This ichnofacies is dominated by horizontal grazing, farming and feeding traces, ranging from solitary to branching tubular burrows (Ophiomorpha, Palaeophycus and Planolites) to meandering trails and tunnels (Nereites, Cosmorhaphe, Helminthopsis), as well as the spiriform burrows Spirophycus. Graphoglyptids are the most diagnostic of the Nereites ichnofacies, produced by sediment grazers and farmers (agrichnia) and often displaying intricate networks of mainly horizontal tunnels preserved as hypichnial semi-reliefs. They include the delicate spiral traces of Spirorhaphe, as well as the enigmatic hexagonal network burrow Paleodictyon. Other ichnogenera include Planolites, Thalassinoides and Ophiomorpha which are facies-crossing and not environment specific. Detailed observations of the trace fossil assemblages and the degree of bioturbation enabled different sub-ichnofacies of the Nereites ichnofacies to be distinguished. Ophiomorpha is more common in sandy “proximal” facies and tend to penetrate deeply into pre-existing turbidite beds, its presence suggests a well-oxygenated newly deposited turbidite substrate, probably in the axial region of the fan lobes. Hence, channel axis and proximal fan deposits tend to be dominated by the Ophiomorpha rudis sub-ichnofacies. The Paleodictyon sub-ichnofacies is more typical of the lower energy lobe/fan fringe subenvironments. Proximal but off-axis areas are characterized by a mixture of the Ophiomorpha rudis and Paleodictyon sub-ichnofacies.
, Abdul Halim Abdul Latiff
Bulletin of the Geological Society of Malaysia, Volume 71, pp 79-87; https://doi.org/10.7186/bgsm71202107

Abstract:
Peninsular Malaysia is susceptible to large magnitude earthquakes induced by the regional sources as it is surrounded by countries that are known for their active seismicity. Tremors were felt in Penang Island of Pulau Pinang due to earthquake events in Sumatra, Indonesia in 2005 and 2009. Presence of cracks on buildings in the island was reported caused by the earthquake on 2nd November 2002. The tsunami that hit the island on 26 December 2004 was the aftermath of the Great Sumatra-Andaman earthquake with magnitude 9.1. The investigation of earthquake risks ensures that the effect of earthquake disasters in the inclined region can be reduced effectively. This paper aims to provide a comprehensive seismic hazard assessment in Penang Island by analysing the predominant natural frequency distribution in Balik Pulau through a passive seismic survey method known as horizontal-to-vertical spectral ratio (HVSR) and evaluating the ground motion throughout the island using probabilistic seismic hazard assessment (PSHA) approach. The natural frequencies of Balik Pulau mostly falls in the range of 3 to 4 Hz which is associated with loose deposits and stiff soil layer. The amplification factor extracted from the HVSR curves ranges approximately 4 to 5. The minimum ground motions estimated for a fixed intensity in 50 years for Penang Island is 0.006 g1 and can reach up to 0.025 g. While the minimum ground motions for a fixed return period of 98 years in 50 years is 0.016 g with maximum of 0.035 g.
Yasin Abdi, Bijan Yusefi-Yegane, Amin Jamshidi
Bulletin of the Geological Society of Malaysia, Volume 71, pp 13-22; https://doi.org/10.7186/bgsm71202102

Abstract:
The accurate determination of strength parameters of rocks such as uniaxial compressive strength (UCS) and elastic modulus (E) using direct and laboratory methods require substantial time and cost. Therefore, the production of predictive relationships and models to forecast the UCS and E is of critical necessity in rock engineering. This study deals with the estimation of UCS and E of sandstones from petrographic characteristics by an artificial neural network (ANN) and multiple regression. For this purpose, 130 core specimens were prepared from sandstones in different locations in Iran. The specimens were tested to determine UCS, E, dry density, and porosity. Also, the petrographic studies including the determination of 11 textural and mineralogy parameters were performed on selected samples. The performance of the ANN model and regression analysis was evaluated using the criteria such as correlation coefficient (R), root mean squared error (RMSE), and variance account for (VAF). According to the ANN results, values of R, RMSE, and VAF were obtained to be 0.925, 0.089, and 97% for UCS and 0.876, 0.094, and 96% for E, respectively. In comparison, for the MLR model, the obtained R, RMSE, and VAF were 0.845, 0.101, and 95% for UCS and 0.797, 0.116, and 93% for E, respectively. A comparison between the findings illustrated that the ANN model was more suitable for forecasting the UCS and E compared with the MLR method.
, Sardar M. Balaky
Bulletin of the Geological Society of Malaysia, Volume 71, pp 99-112; https://doi.org/10.7186/bgsm71202109

Abstract:
Geotourism potential of Akre district in Duhok Governorate, Kurdistan region, northern Iraq is studied in detail. Sixteen geotourism sites were investigated, which are divided into three sub-areas according to their geographical positions. All the tourism sites are located in the northern mountainous part of the High Folded Zone due to their variations from the southern part (Low Folded Zone) in geology, geomorphology, hydrology and tectonic settings. Based on comparison with the Potential Touristic Use (P.T.U) characters, most of the studied geosites have medium correspondence with the P.T.U characters, except three sites i.e. Sipa Akre waterfall, Kani Zark spring and Sipa Bjeel waterfall that have good correspondence. This is because they are reachable by pavement roads and can be easily managed and developed by the local people, in addition to their magical landscapes. The Gali Zenta and Guske resorts have very clear geological elements, particularly the famous massive bitumen seeps within the Zenta valley, and this make their correspondence to the P.T.U characters acceptable despite having bad roads and not progressing very well. The Dinarta sub-area geosite, in spite of its specular view and adaptation for tourism vacancy, has low to medium correspondence to the P.T.U characters due to having the worst roads, and are not developed by any local investors and governments in addition to property problems and remoteness from environmental and cultural sites. H2S rich springs are neglected in the whole Kurdistan region although they have a high economic value by way of balneotherapy. Therefore, the Bekhma and Heshtka hot springs has obtained a very low ratio. The mountainous and caves sites also obtained a low ratio, as the mountain landscapes are neglected particularly for winter tourism, and lack of investment for cave tourism, respectively.
Nur Farhana Salleh, Universiti Teknologi Petronas Center Of Excellence In Subsurface Seismic Imaging & Hydrocarbon Prediction (Csi), Maman Hermana, Deva Prasad Ghosh
Bulletin of the Geological Society of Malaysia, Volume 71, pp 149-157; https://doi.org/10.7186/bgsm71202113

Abstract:
A subsurface resistivity model is important in hydrocarbon exploration primarily in the controlled-source electromagnetic (CSEM) method. CSEM forward modelling workflow uses resistivity model as the main input in feasibility studies and inversion process. The task of building a shaly sand resistivity model becomes more complex than clean sand due to the presence of a shale matrix. In this paper, a new approach is introduced to model a robust resistivity property of shaly sand reservoirs. A volume of seismic data and three wells located in the K-field of offshore Sarawak is provided for this study. Two new seismic attributes derived from seismic attenuation property called SQp and SQs are used as main inputs to predict the volume of shale, effective porosity, and water saturation before resistivity estimation. SQp attribute has a similar response to gamma-ray indicating the lithological variation and SQs attribute is identical to resistivity as an indicator to reservoir fluids. The petrophysical predictions are performed by solving the mathematical step-wise regression between the seismic multi-attributes and predicted petrophysical properties at the well locations. Subsequently, resistivity values are estimated using the Poupon-Leveaux (Indonesia) equation, an improvised model from Archie’s to derive the mathematical relationship of shaly sand’s resistivity to the volume and resistivity of clay matrix in shaly sand reservoirs. The resistivity modeled from the predicted petrophysical properties distributed consistently with sand distribution delineated from SQp attribute mainly in southeast, northeast, and west regions. The gas distribution of the net sand modeled by 5% and 90% of gas saturation scenarios also changed correspondingly to SQs attribute anomaly indicating the consistent fluid distribution between the modeled resistivity and SQs attribute.
Patcharaporn Ngernkerd, , Nutcha Choowong, Peerasit Surakiatchai
Bulletin of the Geological Society of Malaysia, Volume 71, pp 185-202; https://doi.org/10.7186/bgsm71202115

Abstract:
The preservation of terrestrial dune field in a tropical region is rare and relies significantly on the degree of weathering process, humidity and anthropogenic condition. In this paper, we report the remnants of sand dunes that is uncovered from Thungkula Ronghai (TKR) dune field in the southern part of the Khorat Plateau, northeastern Thailand. We reveal, for the first time, the results of systematic geomorphological, sedimentological and chronological analyzes of barchanoid ridges and parabolic dunes found on terraces of the Mun and the Chi Rivers. Interpretation in a series of 1952 aerial photographs, satellite images coupled with Ground Penetrating Radar (GPR) survey, and optically stimulated luminescence (OSL) dating were applied. As a result, we found remnants of mega-barchanoid ridges and isolated parabolic dunes varying in height from 1-2 m with maximum length of 4 km, locally distributed in between terraces of the Mun and Chi Rivers, the middle to eastern part of TKR. Dune shapes include lobate, en-echelon and elongate partially overlying on crevasse sand splay, meandered scar, paleo-channel, mid-channel bar of the fluvial depositional sequences. Orientation of all dunes is in NW-SE direction reflecting the formation was due to the prevailing NW monsoon wind. Transition from barchanoid ridge to parabolic dune was observed. Preliminary OSL dating reveals the deposition of sand dunes occurred between 45 to 28 ka. This age range can be inferred to a warmer and drier period occurred in Marine Isotope Stage 3 (MIS3) before the Last Glacial Maximum.
, National Security Council Malaysian Continental Shelf Project, John Jong, Malaysia Jx Nippon Oil And Gas Exploration (Malaysia) Limited
Bulletin of the Geological Society of Malaysia, Volume 71, pp 159-183; https://doi.org/10.7186/bgsm71202114

Abstract:
An update of the geothermal gradient and heat flow maps for offshore Malaysia based on oil and gas industry data is long overdue. In this article we present an update based on available data and information compiled from PETRONAS and operator archives. More than 600 new datapoints calculated from bottom-hole temperature (BHT) data from oil and gas wells were added to the compilation, along with 165 datapoints from heat flow probe measurements at the seabed in the deep-water areas off Sarawak and Sabah. The heat flow probe surveys also provided direct measurements of seabed sediment thermal conductivity. For the calculation of heat flows from the BHT-based temperature gradients, empirical relationships between sediment thermal conductivity and burial depth were derived from thermal conductivity measurements of core samples in oil/gas wells (in the Malay Basin) and from ODP and IODP drillholes (as analogues for Sarawak and Sabah basins). The results of this study further enhanced our insights into the similarities and differences between the various basins and their relationships to tectonic settings. The Malay Basin has relatively high geothermal gradients (average ~47 °C/km). Higher gradients in the basin centre are attributed to crustal thinning due to extension. The Sarawak Basin has similar above-average geothermal gradients (~45 °C/km), whereas the Baram Delta area and the Sabah Shelf have considerably lower gradients (~29 to ~34 °C/km). These differences are attributed to the underlying tectonic settings; the Sarawak Shelf, like the Malay Basin, is underlain by an extensional terrane, whereas the Sabah Basin and Baram Delta east of the West Baram Line are underlain by a former collisional margin (between Dangerous Grounds rifted terrane and Sabah). The deep-water areas off Sarawak and Sabah (North Luconia and Sabah Platform) show relatively high geothermal gradients overall, averaging 80 °C/km in North Luconia and 87 °C/km in the Sabah Platform. The higher heat flows in the deep-water areas are consistent with the region being underlain by extended continental terrane of the South China Sea margin. From the thermal conductivity models established in this study, the average heat flows are: Malay Basin (92 mW/m2), Sarawak Shelf (95 mW/m2) and Sabah Shelf (79 mW/m2). In addition, the average heat flows for the deep-water areas are as follows: Sabah deep-water fold-thrust belt (66 mW/m2), Sabah Trough (42 mW/m2), Sabah Platform (63 mW/m2) and North Luconia (60 mW/m2).
John Kuna Raj
Bulletin of the Geological Society of Malaysia, Volume 71, pp 1-11; https://doi.org/10.7186/bgsm71202101

Abstract:
Three broad zones can be differentiated within the weathering profile over porphyritic biotite granite at Km 31 of the Kuala Lumpur - Karak Highway. The top Zone I (pedological soil) is 12 m thick and comprises A, B and C soil horizons; the C horizon (saprolite) being a clayey sand with indistinct relict bedrock textures. The intermediate Zone II (saprock) is some 30 m thick and consists of silty sands that indistinctly to distinctly preserve the minerals, textures and structures of the original granite. Zone II can be differentiated into four sub-zones; the upper II A and II B sub-zones marked by an absence of core boulders, whilst the lower II C and II D sub-zones have some to many core-boulders. The bottom Zone III (bedrock), whose upper surface is marked by an unconfined groundwater table, is a continuous granite outcrop with effects of weathering along and between discontinuity planes. Constant head permeability tests show saturated hydraulic conductivity (Ks) to vary with depth and texture; clayey sand from saprolite having a conductivity of 0.2420 cm/hr and silty sand from sub-zone II B, a conductivity of 0.7464 cm/hr. Silty sands from sub-zone II D have saturated hydraulic conductivity values of 1.5313, and 1.9585, cm/hr, whilst a silty sand from sub-zone II C has a conductivity of 4.1131 cm/hr due to it being collected at a relict pegmatite pod. Regression analyses show variable trends with low to moderate correlation coefficients (R2 0.820) for hydraulic conductivity versus physical properties as dry unit weight and void ratio.
Fawzi M.O. Albeyati, , Rushdy S. Othman
Bulletin of the Geological Society of Malaysia, Volume 71, pp 125-138; https://doi.org/10.7186/bgsm71202111

Abstract:
Thirty four cuttings samples from the Jurassic rock succession in well Balad-1 in the Balad Oil Field, Central Iraq have been collected. Using various organic geochemical techniques, the organic matter’s quantity, quality, maturity, and their source rock’s depositional setting were determined. The samples were evaluated to determine the amount of their organic matter content, type of organic matter, δ13C carbon isotopes abundance for both saturated and aromatic, and molecular properties. The results of organic geochemistry analysis show that Sargelu, Gotnia, and Chia Gara formations contain fair to decent amounts of organic matter. Naokelekan Formation encompasses fair to excellent organic matter, while Najmah Formation comprises very high to exceptional organic matter. The analyzed samples revealed the existence of kerogen types III and II/III mainly within oil window. Thermal maturity related biomarkers are in a good agreement with Rock-Eval parameters, but did not reach equilibrium phase. Source related biomarkers show that these rock units rich in organic matter were mainly deposited in an anoxic marine depositional setting which consists of carbonate influenced by terrestrial input.
, Nana Sulaksana, Boy Yoseph C.S.S.S.A., Adjat Sudradjat
Bulletin of the Geological Society of Malaysia, Volume 71, pp 227-241; https://doi.org/10.7186/bgsm71202118

Abstract:
Groundwater studies were carried out in the center of the West Progo Dome, at Kaligesing, Purworejo District, Central Java, and its surrounding area, with an emphasis on hydrochemical problems. As a water-scarce area, groundwater studies are urgently needed in this area. This research is intended as a hydrogeological study with the aim of knowing the conceptual groundwater flow model in the study area. The method used is a field hydrogeological survey as well as hydrochemical and natural isotope analysis supported by chemical and groundwater isotope data. Less clear hydrochemical evolution indicates that the process of groundwater flow is dominant in the local flow system. Groundwater facies is dominated by bicarbonate type, neutral pH, relatively low total dissolved solid (TDS), and electric conductivity (EC), and influenced by season or rainfall. The dominant hydrochemical processes in the groundwater system are leaching, ion exchange, sulfate reduction, and dilution. Groundwater facies is determined by the rock minerals marked by differences in hardness and TDS. Whereas, stable isotope contents of groundwater vary from light to heavy. Springs with light isotopes show the circulation of deep groundwater flow or from a relatively high recharge zone, either locally or from other places around it. Isotopic enrichment in all seasons can occur due to evaporation or mixing with surface water that has undergone previous evapotranspiration, indicated by increasing of heavy isotopes or δD-excess (d) of groundwater. There are two types of groundwater flow patterns, namely shallow and deep groundwater flow patterns. Shallow groundwater is characterized by heavy isotopes, shifted with relatively small d. Deep groundwater circulation pattern is characterized by a consistent, light δD value and appreciable d.
, Kian Min Kwa, Muhammad Zulhilmi Ishak, Lalitha Nagappan, Jaw Chuen Yong
Bulletin of the Geological Society of Malaysia, Volume 71, pp 203-213; https://doi.org/10.7186/bgsm71202116

Abstract:
A Holocene beach ridge and present day shore ridge system located in a rural area north east of Kuala Terengganu was studied. The relation between fecal coliform (FC) MPN Index (Most Probable Number) distribution with rainfalls and saline intrusions into the unconfined aquifer of the beach ridge–shore ridge system was examined. The probable primary source of the pollutants was also investigated in order to highlight the susceptibility of such aquifers to pollution. Six sampling sessions were made from September 2009 to January 2010. Three represent drier conditions and the other 3, heavier rainfalls corresponding to the northeast monsoon season. This sampling period represent a condition when this area was still not subjected to major coastal erosions and subsequent rock revetment work. Altogether, water samples were taken from 13 wells and 3 river stations. Physical-chemical measurements were made in-situ, while FC was tested at UMT laboratory. Essentially, the results indicated that the groundwater in the unconfined aquifer layer of the beach ridge was moderately to highly polluted with FC (up to 1600 MPN). In contrast, the shore ridge was only slightly polluted, whereas river stations had mixed conditions but generally worse than the beach ridge and shore ridge. These phenomena could be associated with salinity spatial-temporal variations. Samples from heavy rainfall conditions indicated lower pollution levels compared to drier conditions. This phenomenon could be associated with the availability of more infiltrated atmospheric water to dilute pollutants in a high hydraulic conductivity environment as the ridges are made of fine to coarse sands. The results underscore the sensitivity of such environment to pollution transport and distribution and hence implied special attention with regards to water resource management.
Zaid A. Malak, , Ezzat I. Al-Fandi
Bulletin of the Geological Society of Malaysia, Volume 71, pp 47-55; https://doi.org/10.7186/bgsm71202104

Abstract:
The Upper Cretaceous Shiranish Formation outcropped close to Bade village and Bekhere anticline, Kurdistan region at northern Iraq and consists of alternating mixed tough grey limestone, marly limestone, marl beds interpreted as a middle - outer shelf – upper bathyal environments (basinal) depositional environment. Fifteen thin sections were studied under a polarized microscope to find out the petrographic component, fauna content, and for microfacies analysis. The major petrographic constituents are fossils, bioclastic grains, micrite matrix, and extraclast (quartz grains). Planktic foraminifera and nannofossils are the major particles within wackestone and packstone microfacies types. The planktonic foraminifera biozones from previous study (such as Globotruncana aegyptiaca, Gansserina gansseri, Racemiguembelina fructicosa, Plummerita hantkeninoides) and the recorded calcareous nannofossils biozones of Broinsonia parca, Reinhardtites levis, Arkhangelskiella cymbiformis, suggest a late Campanian to late Maastrichtian age.
Bulletin of the Geological Society of Malaysia, Volume 71, pp 57-69; https://doi.org/10.7186/bgsm71202105

Abstract:
The Sanai Hill B outcrop, exposed at Kampung Guar Jentik, Beseri district, Perlis, exposes one of the best-preserved Devonian-Carboniferous boundary successions in Malaysia. A new geologic map for the locality is presented, which is based on better exposure of the outcrop due to active quarrying, and was constructed using a combination of aerial drone imagery, three-dimensional photogrammetry, Google Earth satellite imagery and traditional field methods. The sedimentary strata include the Silurian Mempelam Limestone, the Lower Devonian Timah Tasoh Formation, the Upper Devonian Sanai Limestone, the Lower Carboniferous Telaga Jatoh Formation and the Lower Carboniferous Chepor Member of the Kubang Pasu Formation. The Devonian-Carboniferous boundary is marked by the contact between the Sanai Limestone and the Telaga Jatoh Formation. It shows an abrupt change from carbonate to siliceous (chert) deposition, with the contact represented by a paraconformity. This unconformity can be correlated to the Devonian-Carboniferous unconformity in the Kanthan Limestone of Perak. It can also be identified in many sections throughout the Western Belt, including in southern Thailand, Langkawi, Kedah, Perak and the Selangor-Kuala Lumpur area. The unconformity can be linked to a eustatic sea level fall at the end of the Devonian. N-S trending imbricate reverse faults and repeated sections have been interpreted as evidence for collisional tectonics associated with the Late Triassic Indosinian Orogeny. E-W trending normal faults mark a Tertiary extensional phase.
Yulinar Firdaus, Ali Albab, , Dida Kusnida, Riza Rahardiawan, Imam Setiadi, Shaska R. Zulivandama, Tumpal B. Nainggolan, Nazar Nurdin
Bulletin of the Geological Society of Malaysia, Volume 71, pp 113-123; https://doi.org/10.7186/bgsm71202110

Abstract:
Sub-Bottom Profiling (SBP) records and results of geochemical analysis of 12 surficial sediment cores from various water depths collected from the offshore Waropen Basin-Papua are presented. Presence of gas is clearly observed on sub-bottom profiler records. Shallow gas was identified through acoustic response due to gas accumulation and gas escape on sub-bottom profiles. Acoustic evidences of gas accumulations within near surface geology consist of high amplitude reflections and associated acoustic blanking, gas plumes and morphological features like pockmarks. Total organic carbon analysis of 12 surface sediment cores varies between 0.5% to 1.3% which indicate that the sediments have an abundance of organic matters. Gas chromatographic analysis of hydrocarbon composition detected only methane, a biogenic origin of shallow gas. Acoustic and geochemical evidence in the Waropen Basin indicates extensive shallow gas accumulations in the Late Quaternary sediments, some trapped within these deposits and some escape from seabed into the water column which then created a high distribution of pockmarks.
, Universiti Teknologi Petronas Center Of Excellence In Subsurface Seismic Imaging & Hydrocarbon Prediction (Csi), Nur Shafiqah Shahman, Jasmi Ab Talib, Deva Prasad Ghosh
Bulletin of the Geological Society of Malaysia, Volume 71, pp 139-147; https://doi.org/10.7186/bgsm71202112

Abstract:
Sedimentary rock deposition occur in very fast rates in offshore basin and might cause shallow subsurface geohazards that will incur high risk and increase cost of drilling operations. In general, offshore geohazards consist of a variety of geological features that contribute potential risks to the labour force, offshore amenities including the environment and surrounding areas due to the consequences of long or short period of geological processes. Therefore, further study need to be done properly in terms of geohazards classification that is significant to the offshore oil and gas developments in the Malay Basin (Bujang Field, refer Figure 1); such as shallow gas, gas hydrate, shallow water flow, slumping, landslides, faulting, pockmarks and liquefaction. To mitigate the point of costly drilling and safety risks, several techniques are needed during data gathering to visualize, interpret and identify the potential shallow drilling hazards. Besides, to a geoscientist, data integration and modelling techniques can be used to analyse the structural and physical circumstances of shallow subsurface. At the same time, gas models and geohazards map can be established based on seabed hazard analysis from seismic data to plan secure wells. Several seismic attributes such as instantaneous phase, instantaneous frequency, remove bias and envelope (reflection strength) had been used for channel detection. For gas cloud identification, seismic attributes such as remove bias, instantaneous phase, Chaos and RMS (Root Mean Square) amplitude are used. Besides that, spectral decomposition technique are used to display channel systems and other stratigraphic features in the field. Generally, this paper will explain about the meaning of geohazards in the oil and gas industry, the types of geohazards, general geohazards analysis, and will focuss on the identification of gas cloud through channel structure by applying several seismic attributes on specific parameters. All of this will be related to geohazards perspective and consequently, precautions can be undertaken systematically.
, Jakarta Center For Isotopes And Radiation Application, Rasi Prasetio, B. Yoseph C.S.S. Syah Alam, M. Sapari D. Hadian, Hendarmawan Hendarmawan
Bulletin of the Geological Society of Malaysia, Volume 71, pp 215-226; https://doi.org/10.7186/bgsm71202117

Abstract:
The current 2019 isotope and hydrochemical study of hot and cold springs in Sembalun - Rinjani area is a re-assessment of previous similar study in 2012. The aim of this study is to assess the isotope and hydrochemical characteristics of springs due to the earthquake events in 2018. After the earthquake events in 2018, the stable isotopes δ18O and δ2H composition of Sebau hot spring and most of cold springs is shifted into more depleted values which may indicate water-rock interaction or interaction with cold waters which has more depleted δ18O and δ2H values. Also, Sebau hot spring is still plotted at mixing line of meteoric and andesitic water, but still dominant meteoric water. The hydrochemical data of all cold springs and Orok river show the enrichment of Na, probably from silicates weathering or the cation exhchange. While hydrochemical composition of Sebau hot spring is significantly decreased, except SO4, probably due to dilution with cold waters before the thermal water reach the surface. The Piper diagram showed that cold springs and Orok river are Ca-Mg-HCO3 type before and after the earthquake events. While Sebau hot spring is shifted from Ca-Cl type into mixed Ca-Mg-Cl type after the earthquake events. The temperature of Sebau hot spring slightly decreased from 35.5 °C to 34.8 °C after the earthquake events, while Na/K geothermometer calculation also indicate decreasing of sub-surface temperature, i.e. from 146–165 °C to 130–150 °C.
, Kuala Lumpur Gfsi Llc, John Jong, Mazlan Madon, Kl Jx Nippon And Gas Exploration (Malaysia) Limited
Published: 30 April 2021
Warta Geologi, Volume 47, pp 29-48; https://doi.org/10.7186/wg471202104

Abstract:
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.
, Majlis Keselamatan Negara Projek Pelantar Benua Malaysia
Published: 30 April 2021
Warta Geologi, Volume 47, pp 19-28; https://doi.org/10.7186/wg471202103

Abstract:
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.
John K. Raj
Published: 30 April 2021
Warta Geologi, Volume 47, pp 1-8; https://doi.org/10.7186/wg471202101

Abstract:
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.
Zuliskandar Ramli, Muhammad Nu’Man Mohd Nasir, Muhamad Shafiq Mohd Ali
Published: 30 April 2021
Warta Geologi, Volume 47, pp 9-18; https://doi.org/10.7186/wg471202102

Abstract:
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.
J.K. Raj
Published: 31 December 2020
Warta Geologi, Volume 46, pp 179-185; https://doi.org/10.7186/wg463202001

Abstract:
Fresh, dark grey to black, shales with minor sandstones of the Triassic Gemas Formation outcrop at the slope cut between Km 81.30 and 81.05 (southbound) of the North-South Expressway near Ayer Hitam in Johore State. The beds strike 165o with eastward dips of 35o to 43o and have thickness of between 0.2 and 1.5 m. Over-lying the fresh bedrock along an irregular boundary is a bleached zone, some 14 to 18 m thick, comprising light grey to white, in situ oxidized shales and sandstones. Three samples were collected from a thick shale bed; fresh samples A and B at 18 m and 15 m depth, respectively, and a bleached shale sample C at 11 m depth. All samples were air dried, finely ground, and then passed through a wire mesh sieve with 180 μm aperture sieve. The remoulded samples were tested with the Bromhead ring shear apparatus, employing the pre-shearing test procedure with multi-stage loading. Plots of shear stress versus cumulative horizontal shear displacement under low normal stresses (
, Mokhtar Saidin
Published: 31 December 2020
Warta Geologi, Volume 46, pp 204-209; https://doi.org/10.7186/wg463202006

Abstract:
Archaeological excavations at the Sungai Batu Archeological Complex have unearthed potsherds with monument structures. The discovery of the potsherds enables scientific studies of X-ray diffraction (XRD), X-ray fluorescence (XRF) and Scanning Electron Microscopy (SEM) analysis to be conducted and resolve related issues such as where the raw materials were obtained by the manufacturers. To solve the issue, potsherds were taken from around the ancient river, and scientific analyses was conducted for comparison purposes. Before the clay sample was subjected to the scientific analyses, the samples were cleaned and measured (for weight, thickness and width). Color sampling was also performed. Based on results of the analyses, it clearly shows that the potsherds was produced using raw materials from the ancient river in the Sungai Batu Complex itself and baked at a temperature between 550°C and 650°C.
, S. Somsak, A. Numprasanthai
Published: 31 December 2020
Warta Geologi, Volume 46, pp 210-213; https://doi.org/10.7186/wg463202007

Abstract:
White silica sand samples were collected from Steuong Hav district area. The samples were mixed and quartered to obtain a representative sample for physical and chemical characterization. Silica (SiO2) and iron oxide (Fe2O3) content were measured by X-ray fluorescence (XRF) analysis. The results showed silica and iron oxide content at 94.83 wt.% and 0.189 wt.% representatively. In this study, a shaking table, Wet High-Intensity Magnetic Separators (WHIMS), and reverse flotation technique was undertaken to remove mainly iron oxide. The collectors amine (named AOA) and petroleum supinate (named NANZA), pine oil as frother, and H2SO4 as depressant were used to optimize the froth performance. The iron oxide content was removed from 0.189wt.% to 0.062 wt.% and the silica content was upgraded from 94.83 wt.% to 98.6 wt.% after the process.
, Edy Tonnizam Mohamad, Rosli Saad, Universiti Teknologi Malaysia Centre Of Tropical Geoengineering (Geotropik)
Published: 31 December 2020
Warta Geologi, Volume 46, pp 220-224; https://doi.org/10.7186/wg463202009

Abstract:
Sources of clean water are decreasing due to rapid usage, contaminated surface waters, pollution and dry season. The dependence on the existing water source is not enough to fulfil the increasing demand of population in Malaysia. In order to overcome the problem, groundwater source is the most suitable alternative. 2-D resistivity method was carried out in a granitic area of Kluang, Johor to delineate and locate groundwater resource. 5 survey lines were conducted by using ABEM SAS4000 terrameter and electrode selector which were connected to 41 electrodes through lund cables. Pole-dipole array was chosen in this study for deeper penetration. Collected data were processed by using RES2DINV software to produce inversion model which was then exported to Surfer8 software for visualisation and interpretation. The result shows that most of the study area consist of granite with different level of fracturing. Unconfined aquifer was found at depths of 0 to 50 m. Confined aquifers can be seen at two different zones. They exhibit same properties at three parallel lines, R1-R3 and show continuity between them. It is predicted that the aquifers flow in the southwest to northeast direction. The hard rock aquifers are highly recommended to be drilled as they contain a large amount of fresh water for further usage.
Abubaker Alansari, Ahmed Salim, Abdul Hadi Abd Rahman, Nuri Fello, Hammad Janjujah
Published: 31 December 2020
Warta Geologi, Volume 46, pp 230-234; https://doi.org/10.7186/wg463202011

Abstract:
High and low resistivity values is an alarming phenomenon that is usually associated with a very complicated reservoir history and worth looking into. Ordovician sandstone reservoirs are the primary oil producers in the Murzuq basin oil fields that is characterized with an average porosity of 14%, permeability range 410-10,760 md and clean quartz aranite composition. More than fifty wells were drilled in Sahara oil field, but only four of them were announced to have high resistivity values more than 100k ohm-m and ten others to be considered as low resistivity wells (below 50 ohm-m). Therefore, average deep resistivity was mapped in both water and oil legs using all available data set, and the top reservoir was employed as a trend map. They showed distinctive trends for low resistivity readings in oil-leg and confirmed the extreme deep resistivity nature for the wells (W7, W8, W9, and W10). Height above oil water contact and capillary pressure was also calculated for all the wells and revealed a high pressure (400 psi) at the location of the high resistivity wells. As a result, of higher capillary pressure in thicker reservoir area oil might have been able to displace water through geological time by benefitting of more considerable height above oil-water contact, higher connate pressure, and buoyancy forces support, which resulted in occupying all the larger pores and pushed the water into minor scattered pores leading to gradual alteration of reservoir wettability from water to oil-wet. Hence, the brine fluids will no longer be connected to each other inside the pore system. Therefore, they will lose their contribution to resistivity readings, and the resistivity tool will encounter a more resistant medium, which in turn will lead to underestimation of water saturation.
, Tze Tshen Lim, Norliza Ibrahim, Mohd Azmi Abdul Razak, Fakhrulradzi Mohd Razif, Zarris Kem, Boon Tat Ching, Paleontological Society Of Malaysia
Published: 31 December 2020
Warta Geologi, Volume 46, pp 196-198; https://doi.org/10.7186/wg463202004

Abstract:
A cheek tooth of Stegodon, an extinct genus of Proboscidea, had been discovered in a cave in Gopeng, Perak. The discovery represents the first fossil of Stegodon ever found in Malaysia. Embedded in lithified cave infillings are the associated dental remains from at least three or four other different taxa of fossil mammals commonly found among Southeast Asian Pleistocene-Holocene faunas. The finding provides a unique chance for investigations into the evolution dynamics of Stegodon in this part of Southeast Asia and the species diversity of Proboscidea in prehistoric Peninsular Malaysia. Fossil mammal assemblages from different phases of Pleistocene-Holocene period collected from karstic caves in Peninsular Malaysia, when considered with similar assemblages from other parts of Southeast Asia, have the potential to contribute to our understanding of prehistoric faunal migrations and species compositional changes among the biogeographic (sub)divisions in Southeast Asia. This may ultimately lead to a better knowledge of the possible paleoenvironmental and paleoclimatic fluctuations that influenced patterns of migration and adaptive responses of mammalian faunas in Quaternary Southeast Asia.
Ling Han Khong, , Kamar Shah Ariffin
Published: 31 December 2020
Warta Geologi, Volume 46, pp 214-219; https://doi.org/10.7186/wg463202008

Abstract:
Textural properties are among one of the fundamental characteristics especially important to be understood before suitable application(s) of a kaolin can be determined as they have direct influence on the other properties such as plasticity, brightness, firing and rheological behavior. This paper presents an investigation on the textural properties of aplitic kaolin from Kinta Valley. Two degritted kaolin samples from different location of Kinta Valley were measured for their particle size distribution by laser diffraction method. The samples were then classified into different size fractions followed by examination of their morphological property by various techniques which X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscope (FESEM). Generally, the kaolin can be classified into two different types based on the fine fraction content which may be consists of; i) delaminated platy kaolinite, or ii) tubular shaped halloysite. These fine fractions however constitute only to minor amount or not more than 12 % of the clays, as both clay consist predominantly of coarse book like kaolinite stacks. The degree of crystallinity of kaolinite samples shows a positive correlation to its particle size during examination by XRD, but FTIR spectrum shows a high degree of crystallinity for all kaolinite samples regardless of their particle size. Slight presence of halloysite is sufficient to give an adverse effect on the clay crystallinity index measured from XRD pattern. Sorting of the clay into different size and morphological fraction creates a product with less variation in properties between individual particles, and with more potential for tailoring or engineering of their properties.
Najmiah Rosli, Rosli Saad, Nazrin Rahman,
Published: 31 December 2020
Warta Geologi, Volume 46, pp 186-190; https://doi.org/10.7186/wg463202002

Abstract:
Soft soils pose abundant engineering issues due to its low bearing capacity and shear strength. Comprehensive study on soft soil’s physical properties such as shear strength and ability to store water (porosity) could help in devising the optimum ground improvements and foundations techniques. Therefore, physical properties of soft marine clay in Nibong Tebal were thoroughly studied using 2-Dimensional Resistivity Imaging (2-DRI) method in conjunction with porosity measurements, standard penetration test values (SPT-n) and particle size distribution (PSD) analysis. The 2-DRI profile depicts three lithologies, which are unsaturated topsoil, saturated soft clayey soil and saturated sandy soil in the area. The soft soil extends up to 32 m in thickness where it overlies the sandy layer and could be correlated back to lithology profile from borehole record. Additionally, soil samples were collected at three locations along the survey line for porosity measurements via saturation porosimetry method. The samples demonstrate that the clay layer has a very large porosity range and signifies that the soil will compress tremendously under load. On the other hand, SPT-N values of the soft clay is also very low; thus, could be classed as very soft to soft cohesive soil with very low shear strength as compared to a higher range SPT-n values of the sandy layer. The PSD result also compliments the 2-DRI, porosity and SPT results to show distinct differences between topsoil and the soft clay layer in terms of the presence of fine grains. These results further indicate that the thick upper layer is not capable of bearing immense loads such as high-rise infrastructures due to the soil’s high porosity and low shear strength. Hence, the area must undergo ground remediations prior to any infrastructure developments on the land.
Alan Thompson, United Kingdom Cuesta Consulting Limited, Brian Marker, Jane Poole, , Choun-Sian Lim, Yunus Abdul Razak, Julian Hunt, Malaysia Geological Society Of Malaysia
Published: 31 December 2020
Warta Geologi, Volume 46, pp 235-243; https://doi.org/10.7186/wg463202012

Abstract:
Communication is an essential aspect of preparing for, avoiding or responding to the occurrence of natural geohazards. As such, it forms an integral part of any strategy to enhance resilience to geohazard events. Conversely, inadequate or lack of communication is a common factor in failing to minimise the risks involved. Communication about geohazards occurs at several different levels: between geoscientists and other professionals such as the engineers and planners; between professionals and other groups such as emergency services and insurance companies; and between all of these parties and the general public who are affected by events. Geoscientists need to be involved in all of these lines of communication. This paper examines the essential role of geoscientists in helping to reduce the risks associated with a wide range of geohazards. A series of key principles that links to a generic model of geohazard communication applicable to a wide range of scenarios is presented
Nik Nur Anis Amalina Nik Mohd Hassan, Kim Kiat Liaw, Yazid Mansor
Published: 31 December 2020
Warta Geologi, Volume 46, pp 225-229; https://doi.org/10.7186/wg463202010

Abstract:
Penyu Basin is a complex, intracratonic basin, situated on the northern Sunda Shelf. This basin formed during Oligocene, and geological setting of this area is a typical Southeast Asian Tertiary rift system. An oil discovery has been made in X-Block of Penyu Basin. However, it was relinquished in 2006 due to the non-commercial oil discovery. X-Block consists of mostly monoclinal structures that do not seem to provide an efficient trapping mechanism because of the very low reliefs. Three wells have been drilled in X-Block and tested primarily on the structural traps, mainly the basement drape structures. This research aims to analyze the stratigraphic traps, focusing on channel features. This is done with the aid from seismic geomorphology. This method helps examine buried landforms by using seismic data as a tool. By seismic geomorphology study, several channel features can be recognized. Most of the channels can be found in upper and middle part of the seismic section. As going deeper to the bottom section, only lineaments of faults are visible. In the upper part of the seismic section, straight and long channel features can be observed and as moving downwards, the channel sinuosity increases resulting in meandering channel. From this seismic geomorphology study, it confirms that there are channel systems in X-Block of Penyu Basin.
, Hennie Fitria W. Soehady Erfen, Azman A. Ghani, Angela Vidda Chuwat, Gerald Eko Ejiga, Terfa Elijah Garba
Published: 31 December 2020
Warta Geologi, Volume 46, pp 191-195; https://doi.org/10.7186/wg463202003

Abstract:
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.
, Fianti Fianti, Dwi Rizki R, Agus Setyawan, Ronaldo Talapessy
Published: 31 December 2020
Warta Geologi, Volume 46, pp 199-203; https://doi.org/10.7186/wg463202005

Abstract:
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.
Bulletin of the Geological Society of Malaysia, Volume 70, pp 87-102; https://doi.org/10.7186/bgsm70202007

Abstract:
A collection of 165 crude oils, 12 oil seeps, and 24 extracts and recovered samples from 25 oil exploratory wells and 6 oil seeps in the Southern Mesopotamian Basin were studied. Biomarker configurations and other organic geochemistry parameters were used to discover the depositional environments and to classify the oil samples as provenance groups. Petroleum liquids were geochemically classified into four groups. The first group of oils, Middle Jurassic Zagros Fold Belt, is located in the Maysan, Basra, and Thi qar provinces of the basin that has pristane/phytane (Pr/Ph) proportions ≤0.97 and contains sufficient gammacerane. Methylphenanthrene index 1 (MPI 1) values show that the first group of oils is mature. Oils from Group 2, Upper Jurassic–Lower Cretaceous Sulaiy/Yamama, by disparity have Pr/Ph proportions between 0.72 and 1.12 and relatively moderate C28/C29 steranes, 0.52-0.88. Ts/Tm ratios indicate thermal maturity for Group 2 oils. Unlike oils from other groups, the oils from Group 3, Cretaceous to Tertiary oils, in Subba Field hold the highest canonical variable (CV) values that range between 0.43 and –2.30. The fourth group, Late Triassic-Middle Jurassic oil seeps, is the oldest among all groups. This group holds an average carbon isotope ratio –28.25‰ and –28.10‰ for saturates and aromatics respectively, which are the lowest values among all oils in the studied region. The Tithonian-Berriasian Sulaiy/Yamama oils further divided into three subgroups. The first subgroup, A, has carbon preference index (CPI) values of ≤1.08 (average 0.86) and C28/C29 sterane of 0.56-1.13 with an average of 0.65. Second subgroup, B, holds CPI ≤1.18 (average 0.99) and C28/C29 sterane 0.55-0.82 with an average of 0.63. The last subgroup, C, has CPI values ≤0.93 (average 0.85) and high C27 and C29 steranes (average 46.5% and 39.61%, respectively). In the same way, the Group 3 can be further subdivided into two subgroups based on values of carbon isotopes for saturates and aromatics. The oils from this group are heterogeneous and can be further divided into Tertiary Subgroup and Cretaceous Subgroup.
, National Security Council Malaysian Continental Shelf Project
Bulletin of the Geological Society of Malaysia, Volume 70, pp 17-28; https://doi.org/10.7186/bgsm70202002

Abstract:
Activities by coastal States in relation to the exploration and exploitation of non-living natural resources (namely hydrocarbons and deep-sea minerals) on the continental shelf beyond 200 nautical miles (M) from their territorial sea baselines are reviewed. Geological conditions dictate such that hydrocarbons are likely to occur where there are thick accumulations of sediments (at least 2-3 km is needed for organic matter to generate significant amounts of hydrocarbons), whereas deep-sea minerals are found on or beneath the seabed of the deep oceans, which are generally “starved” of sediment. Thus, in general, sites for hydrocarbon exploration and for deep-sea mineral exploration are unlikely to overlap. On a ‘normal’ geological shelf with an average width of say ~60-100 km, hydrocarbon exploration is carried out generally within the 200 M limit of the Exclusive Economic Zone (EEZ) of the coastal State. Within the last decade, however, necessitated by depleting resources in the shallow waters of the shelf and slope, exploration has gradually moved from the geological shelf (water depth typically < 200 m) further out into deeper waters, and in some cases, beyond the 200 M limit. Thus far, only in a few places is oil and gas exploration being carried out on the continental shelf beyond 200 M. Examples include Australia, New Zealand, Norway, Argentina and Canada. Such activities mainly involve geological and geophysical investigations and assessment of the hydrocarbon potential, while some have resulted in commercial production. Besides the conventional hydrocarbons (oil and gas), continental margin sediments may also host significant accumulations of gas hydrates, which are regarded as a potentially important energy resource of the future. Along non-polar continental margins, gas hydrates are generally found beneath the continental slope and the continental rise, i.e. beyond the continental shelf proper, in water depths typically greater than 500 m but still mainly within 200 M of the territorial sea baselines. Where the continental margin is exceptionally wide, however, gas hydrates may occur in areas beyond the 200 M limit, on the extended continental shelf.
, Rodeano Roslee, Ahmad Khairut Termizi Mohd Daud
Bulletin of the Geological Society of Malaysia, Volume 70, pp 1-15; https://doi.org/10.7186/bgsm70202001

Abstract:
The coastal areas of Sabah are exposed to far-field earthquake-induced tsunamis that could be generated along the trenches of Manila, Negros, Sulu, Cotabato, Sangihe and North Sulawesi. Tsunami simulation models from these trenches indicated that tsunami waves can reach the coast of Sabah between 40 and 120 minutes with tsunami wave heights reaching up to 3 m near the coast. The level of tsunami threat is high in southeast Sabah due to its narrow continental shelf and proximity to tsunami source in the North Sulawesi Trench. The level of tsunami threat is moderate in north and east Sabah due to their proximity to tsunami source in the Sulu Trench. The level of tsunami threat is low in west Sabah due to its distant location to tsunami source from the Manila Trench. While tsunamis cannot be prevented, its impact on human life and property can be reduced through proper assessment of its threat using tsunami simulation models. Unfortunately, constraints remain in producing a reliable tsunami inundation models due to the lack of high-resolution topography and bathymetry data in Sabah and surrounding seas. It would be helpful if such data can be acquired by the relevant government agencies, at least first, in high threat-level areas, such as Tawau and Semporna districts. In order to properly plan mitigation measures tsunami risk mapping should be intensified in high threat-level areas. The locations of settlements (including water villages), population concentrations, types of buildings and houses, road system, drainage system, harbours, jetties and vegetations (including mangroves) need to be mapped in great detail. Based on the detailed tsunami risk map, targeted vulnerable communities could be given continuous and intensive education and awareness on basic tsunami science and tsunami hazard preparedness.
, Antonino Briguglio, Sulia Goeting, Amajida Roslim, László Kocsis, Dell’Ambiente E Della Vita Di.S.T.A.V. - Dipartimento Di Scienze Della Terra
Bulletin of the Geological Society of Malaysia, Volume 70, pp 139-151; https://doi.org/10.7186/bgsm70202012

Abstract:
The study aims to get some additional knowledge on the modern seafloor composition offshore Brunei Darussalam by looking at the recent stratigraphic succession of the deposited sediments and their distribution patterns. For this reason, 10 shallow cores (22 to 46 cm thick) have been collected by scuba diving along two depth transects spanning from water depth of 20 to 60 m. One of the transects has been sampled north-northwest of the Muara village, just in front of the Brunei Bay and the other one off the coast near Tutong town, away from major sedimentary inputs. The results obtained portray two different sea bottom compositions and two different depth-related sediment distributions. The Muara transect is highly rich in mud and yielded abundant biogenic component at all investigated depths. The Tutong transect has a higher sand content but display constant changes along with depth. The sediment is mostly composed by biogenic grains such as rests of sponges, foraminifera, molluscs and echinoderms; the not biogenic grains are for the vast majority made of quartz. The sandy fractions of both transects have been tested for cyclicity and all cores can be described by functions with comparable periods, thus indicating that an oscillatory environmental event such as the alternation of the monsoon seasons, has similar influence on the seafloor of both transects.
, Malaysia Jx Nippon Oil And Gas Exploration (Malaysia) Limited, Hui Sin Goh, Steve McGiveron, Jim Fitton, Taman Hoover Park No. 25, Wales Marine Geoscience, Malacca Consultant Operations Geologist
Bulletin of the Geological Society of Malaysia, Volume 70, pp 57-75; https://doi.org/10.7186/bgsm70202005

Abstract:
Natural gas hydrates (NGHs), sometimes referred to as “flammable ice”, are crystalline solids, consisting of hydrocarbon gases with low molecular weight, such as methane, ethane and propane, bound with water molecules within cage-like lattices. The water molecules and low molecular weight NGH lattices are stable within a specific range of temperatures and pressures, and the source of the gases can be biogenic or thermogenic in origin. NGHs are common in the upper hundreds of metres of sub-seafloor sediments on the continental margins at water depths greater than about 500 m. Seismic reflection profiles and wireline well logs are common indicators used to identify the presence of NGHs, which are often encountered during offshore deepwater exploration drilling. They may cause geohazards such as slope instability, expulsion of the seafloor, shallow water flows and shallow gas if the stability of penetrated NGHs is disturbed and starts to dissociate. Methane gas hydrates represent a significant potential energy resource, as illustrated in this case study from offshore NW Sabah and may represent one of the world’s largest reservoirs of carbon-based fuel, with some estimates suggest that the hydrocarbons bound in the form of NGHs may rival the total energy resources contained in other conventional hydrocarbon sources. Methane can be extracted from NGHs through three methods: depressurization, inhibitor injection and thermal stimulation. However, risk associated with NGHs extraction can contribute to environmental concerns such as global warming and a decrease in microbial communities associated with methane hydrate ecosystem. Presently, in many countries, national programs exist for the research and production of natural gas from NGH deposits. As a result, hundreds of deposits have been discovered, with a few hundred wells drilled and kilometres of NGH cores studied. Hence, in the future (pending improved gas price and extraction technology), methane gas hydrates could be a vast source of natural gas supply.
, Mohd Suhaili Ismail, Jasmi Ab Talib, Nur Marina Samsudin
Bulletin of the Geological Society of Malaysia, Volume 70, pp 153-162; https://doi.org/10.7186/bgsm70202013

Abstract:
Spatial lithofacies and lithofacies association serves as one of the reliable methods in assessing the depositional process of sediments and interpreting its depositional environment. The method of facies analysis is adapted in this study where four newly exposed stratigraphic sections along the Jerantut-Maran road in Jerantut, Central Pahang of Peninsular Malaysia were studied. Previous studies showed that the environment of deposition of these continental deposits is broadly of braided-meandering river. Sedimentological data from the newly exposed stratigraphic sections had given a better understanding on the sedimentation processes involved in these deposits where interpretation on the environment of deposition is construed up to its sub-environment. The main lithofacies recognized include conglomerate, sandstone, and fine-grained facies. The facies associations identified include (i) massive to laminated silt/mudstone, (ii) massive sandstone, (iii) thin to thick ripple to parallel laminated sandstone, (iv) conglomeratic sandstone, (v) graded channelized sandstone, (vi) coarsening upwards medium bedded sandstone and (vii) heterolithic sandstone. The different facies associations are grouped to four (4) facies assemblages showing characteristics of certain environment: (1) floodplain, (2) channel bar complex, (3) point bar and (4) crevasse splay. Floodplain facies assemblage is marked by fine-grained facies, mainly siltstone/mudstone and fine-grained sands with lower flow regime structures. Channel bar complex is identified by high energy deposits of coarse-to-medium grained sandstones often with scoured bottom and lenticular geometry. Point bar is recognized by the lateral accretion surfaces often consisting of normal graded sandstone with sharp top and bottom contact, sometimes capped with thin mudstones. Crevasse splay facies assemblage is characterized by heterolithic sandstone, dominated by flaser-wavy bedding and coarsening upwards medium bedded sandstone that is overlain by fine-grained facies of the floodplain assemblage. The overall facies based on an outcrop scale suggests general features of fluvial facies with fluctuations in flow energy. The environment of deposition is thus interpreted to be of braided river with floodplains and isolated point bar.
, Numair Ahmad Siddiqui, Abdul Halim Abdul Latif, Yasir Bashir, Almasgari Abdalsalam Abduh Saeed Ali,
Bulletin of the Geological Society of Malaysia, Volume 70, pp 209-220; https://doi.org/10.7186/bgsm70202016

Abstract:
Offshore petroleum systems are often very complex and subtle because of a variety of depositional environments. Characterizing a reservoir based on conventional seismic and well-log stratigraphic analysis in intricate settings often leads to uncertainties. Drilling risks, as well as associated subsurface uncertainties can be minimized by accurate reservoir delineation. Moreover, a forecast can also be made about production and performance of a reservoir. This study is aimed to design a workflow in reservoir characterization by integrating seismic inversion, petrophysics and rock physics tools. Firstly, to define litho facies, rock physics modeling was carried out through well log analysis separately for each facies. Next, the available subsurface information is incorporated in a Bayesian engine which outputs several simulations of elastic reservoir properties, as well as their probabilities that were used for post-inversion analysis. Vast areal coverage of seismic and sparse vertical well log data was integrated by geostatistical inversion to produce acoustic impedance realizations of high-resolution. Porosity models were built later using the 3D impedance model. Lastly, reservoir bodies were identified and cross plot analysis discriminated the lithology and fluid within the bodies successfully.
A. A. Shah, Batmanathan Navakanesh
Bulletin of the Geological Society of Malaysia, Volume 70, pp 125-132; https://doi.org/10.7186/bgsm70202010

Abstract:
The terms: Active tectonics and active faults have emerged as some of the most frequently used terms in geological literature, and traditionally, the main purpose of these definitions has historically remained devoted to either geological or engineering uses. However, most of the existing literature on the definitions has been gathered since >230 years that were spent on the understanding of the science of earthquakes, but a clear-cut consensus lacks on how to define active tectonics and active faults, for various reasons that are discussed at length here. Therefore, this paper presents a brief overview of the terms with a motivation to rekindle the discussion on what is considered active in tectonics. It also explores whether the traditional definitions are valid or not, and should we look for other alternatives. We present a brief historical background knowledge and understanding on the active faults, and particularly in some of the tectonically stable and presumably inactive portions of the Earth’s crust. The two major strike-slip faulting events (Mw 8.6 and Mw = 8.2) that have occurred in the Wharton Basin, Indian Ocean in 2012 are discussed in detail. The events are specially quoted to make a case for reactivation of old fracture systems as these earthquakes ruptured the ~30-90 Ma old Indian oceanic crust. This clearly demonstrates that much older geological structures could also be re-activated, thereby questioning the traditional definition of the typical time span that is used to define active tectonics and active faults.
Azrin Azmi, Jabatan Sains Bumi Dan Alam Sekitar Program Geologi, , Muhammad Ashahadi Dzulkafli, Zaiton Harun
Bulletin of the Geological Society of Malaysia, Volume 70, pp 77-86; https://doi.org/10.7186/bgsm70202006

Abstract:
The upper part of the Setul Formation and the lower part of the Kubang Pasu Formation are well exposed in Guar Sanai, Perlis due to the earth quarry activities. However, compared to the Hill A and Hill B, the outcrops in Hill C clearly illustrates the influence of structure on the lithostratigraphy of the area. The boundary between the Setul Formation and the Kubang Pasu Formation is marked by the thrust fault generally trending north-south to northeast-southwest and mylonite. The thrust belt associated with folding and uplift clearly developed in the zone between parallel lateral faults (trending north-south and southeast-northwest) and is interpreted to accommodate slip along the transpression zone. The sinistral faults are then deformed by transpression movement of dextral faults (trending east-southwest and east-west) which amplified the earlier structures. The combination of lateral and thrust movements formed flower structure that associated with folding and uplift, commonly found in transpressional zone of the strike-slip region. Deformation has caused the older Setul Formation being uplifted to almost equivalent position to the younger Kubang Pasu Formation and led to the displacement of original bed position and repetition of similar sequences. The formation of folding and reverse faulting associated with left lateral strike-slip fault are interpreted to cause by movement of major fault in the northwest Peninsular Malaysia, known as the Bok Bak Fault.
Achmad Fahruddin, , Muhammad Firdaus, Hanif Mersil Saleh
Bulletin of the Geological Society of Malaysia, Volume 70, pp 103-118; https://doi.org/10.7186/bgsm70202008

Abstract:
The offshore area in the northeast of Kendari city, the southeast arm of Sulawesi, is an area with favourable hydrocarbon prospectivity shown by numerous oil and gas seeps in the surrounding coastal area. It is a frontier basin in eastern Indonesia, known as the Manui Basin. An exploration well named Abuki-1 was drilled in 1990 suggested a Miocene transgressive sequence as a potential reservoir and source rock at this basin. However, this unit has no analogous exposure in the onshore area resulting in the lack of study and knowledge of this potential Miocene unit. Therefore, we revisit the sedimentary rocks exposure nearby Abuki-1 well in the Toronipa peninsula to study about its sedimentary facies and palynological contents. These outcrops by previous researchers were included in Toronipa Member of Meluhu Formation, and a Triassic age was suggested for this unit. By contrast, our result shows that these exposures are Middle to Late Miocene in age as indicated by the occurrence of the Florschuetzia group pollens (Florschuetzia trilobata, F. levipoli, and F. meridionalis). The absence of Plio-Pleistocene pollen and spores index fossils (Stenochlaena milnei group, Dacrycarpus imbricatus, and Phyllocladus) supports the Middle to Late Miocene age interpretation. A wave-dominated estuary depositional model is proposed based on the presence of river-dominated, mixed-energy, and wave-dominated facies associations. We suggest that the studied sediments are the outcrop analogues for the Middle to Late Miocene transgressive sequence found in Abuki-1 well. Furthermore, we recommend that these Miocene estuary-fill complexes should have excellent hydrocarbon potential. The reservoir potential is the sand deposits of the fluvial, tidal, washover, and shoreface facies with moderately to well-sorted characteristics. The source rocks candidate is the mud of lagoon, tidal flat, floodplain, and marine offshore facies. Moreover, the Manui Basin, with its Miocene estuarine deposits, requires further study to reveal its hydrocarbon accumulation potential.
, Zaidi Embong, Muzamir Hasan, Habib Musa, Qamar Uz Zaman, Hidyat Ullah
Bulletin of the Geological Society of Malaysia, Volume 70, pp 133-138; https://doi.org/10.7186/bgsm70202011

Abstract:
This study focused on the stabilization of peat soil and its engineering and mechanical properties improvement such as shear strength, moisture content, liquid limit and shear wave velocity. Peat is considered as weak foundation soil as they have low shear strength, high compressibility and high moisture content. One of the major problems for the construction industries in Malaysia is slope instability, bearing capacity failure and excessive settlement foundation for the development of highways and buildings when its undertaken-on peatland. Malaysia contains about 3 million hectares peatland which cover 8% of its total land. Therefore, it is essential to find an appropriate way to enhance its properties and to ensure the reduction and solution of these problems can finally solve by applying the electrokinetic stabilization (EKS) method. The peat soil samples were collected from Parit Kuari, Batu Pahat, Johor, Malaysia. In the proposed technique, the voltage gradient of 110 and 150 V was applied for the period of 3 and 6 hours. Some laboratory parameters such as shear strength, moisture content (MC), liquid limit, and shear wave velocity were observed for pre as well as for post-EK. It was observed that strength was found significantly improved from 11.66 to 70 kPa, MC was reduced from 613.989 to 270.294%, liquid limit was increased from 159.261 to 217.603%, and shear wave velocity was improved from 68.5 to 110.5 m/s. A significant improvement has been observed in the physical properties of the peat soil by applying the progressive approach showing the robustness of the methodology.
, National Security Council Malaysian Continental Shelf Project, John Jong, Franz L. Kessler, M. Hafiz Damanhuri, Mohd Khairil Azrafy Amin, Kuala Lumpur Jx Nippon And Gas Exploration (Malaysia) Limited, Germany Goldbach Geoconsultants O&g And Lithium Exploration, Malaysia Petronas Carigali Sdn. Bhd.
Bulletin of the Geological Society of Malaysia, Volume 70, pp 163-193; https://doi.org/10.7186/bgsm70202014

Abstract:
Following the successful production from fractured basement in similar Tertiary basins, the basement play was pursued in the Malay Basin, particularly during the 2000-2010 period but, unfortunately, that effort fell short of expectations. The only oil discovery in fractured basement reservoir was Anding in the southwestern part of the basin. Despite its development being delayed due to economic reasons, the Anding discovery had been the basis for the basement play concept: namely, a fractured reservoir formed of pre-Tertiary metamorphic rock, charged from overlying Tertiary lacustrine source rocks in an adjacent half-graben and sealed by a transgressive shale unit. This paper examines seismic, gravity and well evidences on the pre-Tertiary basement geology, with the aim of assessing further the hydrocarbon potential of pre-Tertiary basement. The pre-Tertiary basement subcrops beneath the Malay and Penyu basins represent a continuation of the onshore geology of Sundaland Mesozoic terrane. Wells that penetrate the Base-Tertiary Unconformity (BTU) indicate a variety of rock types including igneous, metamorphic and sedimentary. Seismic data show the widespread presence of layered rocks beneath the BTU which could include potential new plays. Gravity modelling was carried out to help distinguish between pre-Tertiary layered rocks and Tertiary synrift sediments. Fractured reservoirs, like those discovered at Anding, seem to be associated with major strike-slip fault zones which are identifiable on high-quality seismic. Carbonate structures such as paleokarsts and buried hills are also recognisable and could potentially be mapped with seismic. These pre-Tertiary plays also rely on hydrocarbon charge mainly from the overlying Tertiary source rocks. Although Palaeozoic-Mesozoic source rocks may have passed their hydrocarbon generation stage, their gas potential cannot be ruled out.
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