Geology of Kota Kinabalu and Its Implications to Grpundwater Potential
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Annlla! Geo!(lgica! Con/ermct '94 Jllne 11-12, 1994, Kllahl Tertngganll, Malay.,ia Geology of Kota Kinabalu and its implications to grpundwater potential MAJEED F AISAL, SHARIFF A.K. OMANG AND SANUDIN HJ. TAHIR Jabatan Sains Bumi, FSSA, Universiti Kebangsaan Malaysia Kampus Sabah, 88996 Kota Kinabalu, Sabah Abstract: The increasing population in Kota Kinabalu is proportional to the demand for water resource. Groundwater is a primary concern because it is the most economical source of water supply. The main objectives of this paper are (1) to evaluate the groundwater resources in the study area, and (2) to study the effects of geology on groundwater. Kota Kinabalu is underlain by the Late Eocene-Lower Miocene Crocker Formation and Quaternary Alluvium. The Crocker Formation is composed of sandstone, shale and an interlayered sandstone siltstone-shale sequence. The study area is controlled by heavy structural lineaments representing a complex history of folding, thrust, normal and wrench faulting. Movements along these structures strongly influence the geomorphology and groundwater distribution in Kota Kinabalu. The rocks within the fault zones are highly deformed, sheared, jointed, and fractured. The geology of the study area indicates that only the sandstone units of the Crocker Formation and Quaternary alluvium can be considered significant groundwater reservoirs. The aquifers within the study area can be divided into three major groups based on host rock and structural parameters, as follows (1) aquifers of Quaternary Alluvium, (2) aquifers within the fault zones, and (3) aquifers of the sandstone units of Crocker Formation. The chemical and physical analysis of the Kota Kinabalu groundwater suggest a meteoric origin and an alkaline type of water. Both the stratigraphic and structural settings favor a high potential groundwater resource in Kota Kinabalu. These settings facilitate the movement and circulation of groundwater within Crocker Formation and Quaternary Alluvium, affect the continuity of aquifers, enhance secondary permeability, as well as increase the storage capacities of the formations. Such settings also create confined and unconfined aquifer systems. INTRODUCTION changes is insufficient to meet such deman~. Groundwater becomes a primary concern because The area of investigation covers portions ofKota it is the most economical source of water supply. Kinabalu along the western coast of Sabah (Fig. 1). The main objectives of this paper are (1) to evaluate Geology has a fundamental influence on the groundwater resources in Kota Kinabalu, and groundwater. The layered nature of the rocks in (2) to study the effects of geology on groundwater. the .study area makes stratigraphy an essential tool in the search for groundwater. It helps define STRATIGRAPHY the nature, location, and extent of aquifers. A knowledge ofthe depositional and erosional events The exposed rocks in Kota Kinabalu vary in may indicate the extent and regularity of water types and ages from Late Eocene-Lower Miocene bearing formations. Various combinations of sandstone and shale of Crocker Formation to very geologic structures and stratigraphy may result in young alluvial materials which are still being different groundwater systems (Faisal, 1989). deposited. The sedimentological and structural However, rock fractures can be very important in details are provided by Tongkul (1987). increasing secondary porosity, improving storage Table 1 shows the composite stratigraphic capacity as well as enhancing permeability in column of the rock units exposed in the study area otherwise impermeable rocks (Department of Water and their water-bearing properties. For the present Resources, 1978, 1981). study, several localities were visited and semi The increasing population in Kota Kinabalu detailed sectioning was conducted to evaluate the calls for an increase in the demand for water supply. stratigraphic and structural controls on Surface water which is affected directly by seasonal groundwater potential (Figs. 2 and 3). Ceol. Soc. MalaYJia, Bulletin 38, Decemher 1995,. pp. 11-20 12 MAJEED FAISAL, SHARIFF A.K. OMANG AND SANUDIN HJ. TAHIR 1SOE o 10 20 I batu ~ ,. ,-, , ~ .. ". \ I mel Meligan Fm. (Upper Miocene) , : Sandstone (shale) ,, ,,I [!!J Temburong Fm. (OIlg. - E. MIocene) , ,'uc : Shale (sandstone) I \ , G!J Crocker Fm. (Eoe. - E. Miocene) , .... __ ___ ~J' wer : west Crocker eer : East Crocker uer : Undiff. Crocker , : Sandstone and shale \ \ [!!] Trusmadl Fm. (Eoe. - OIlg.) \ : Shale, PhyUlte (siltstone. sandstone) ",---- ~ Sapulut Fm. (Upper Cret. - E. Miocene) : Mudstone (sandstone, eong!.) ct- ts" G!] Chert-Spilite Fm. (E. Cret. - Eoe.) ~ eer " : Chert, apllite, greywaeke, limestone 4;- " CJ I -- Alluvium - ~Tiga • :",of • Town ,':.: ::: q;- ta ~ j ---- Geological Boundary : ~~1 " , CJ 0 I -+ -+ State Boundary . +. +. International Boundary , ,''.\,A\ ,,~~ ,...~ , " I 'J \ .. \ ~, D Study Area f \ '\"~ " I ecr \J'~', , ., /" A: Q /' ,"I \, ~ ___ts ~ "" , " uer , 'b wer ~ :"~'" ~-." - ~,/ .... _- ... - Kenlngau., eer .. ~,,/ ap \- I --. I I I ,., ,.,) r, '",'1/ _"J.!' \ (j~ 1\ " t' , - - , ~ P. Labuan I: ' I '-""~ - ~: \ ,) :/' /;!- - ~-.. Weston ,",',1;1: / " r ,',': '1 wer /_ SookS I I enorlji /I~~:'Y h, ,'I.' ~_, r sp _/ I"~I/ II" : ,,'-," L -: ,: " ,~/,' I Ix to,' I ,If/ I ..."') ,e ,~/ '; " s· . " , I' 'p'tang -' ' Pangt R. ' (.......... ,, " 5°N - /+y'" I' I ' ... , +-+ \,' I , t , + ,, \+\__ ,"'v'''',,,me' wer + ~ 'I-""~ ·llJ " SARAWAK C!J " sp J' : ~ : l :tx: ~/ ct'/ J \ ,I + , I ,..:- Location Map ( ,..: , • Penslangan o 300 - wer -"""':l-.......... 1me ~: 5- I ' ,\ : . +,I .!',, ,: a P +~ + + I +++++ ' +++++++++ ,. ++ + • '+ C!J' + +++: +++ ++. + + • • "\ - \ + +' ++ ++ ••++ +.., '+ ++ ! 'w ++.+~ + ~.++ , + KALIMANTAN \ + + + + 11trE + Figure 1. Geological map of western Sabah (modified from Wilford, 1967). Geol. Soc. MalaYJia, Bulletin 38 GEOLOGY OF KOTA KINABALU AND ITS IMPUCATIONS TO GROUNDWATER POTENTIAL 13 Table 1. Local stratigraphic column. ROCK GENERAL WATER-BEARING AGE FORMATION UNIT CHARACTER PROPERTIES Quaternary Alluvium Unconsolidated gravel, sand and Gravelly and sandly, portions are silt with minor amounts of clay highly permeable and yield large deposited along the rivers or quantities of water. Important to streams and their tributaries. groundwater development. Includes natural levee and flood plain deposit. Late Eocene Crocker Shale This unit composed two types of It has no significant to ground to Formation shales red and grey. It is a water development due to its lower sequence of alteration of shale impermeable characteristic. Miocene with siltstone of very fine. Shale It is a sequence of interlayering of Little importance to ground water sandstone permeable sediment sandstone provide some water but not interbedded with impermeable sediment of enough for ground water shale. The permeability of this development. unit is quite variable. Ground water in this unit tend to be under semi-confine to confine system. Sandstone Light grey to cream colour, Importance to ground water. medium to coarse grained and sometime pebbly. It is highly folded, faulted, jointed, fractured occasionallycavemous, surficially oxidized and exhibit spheroidal weathering. .. normal beds ---------.......~ \ .....---- reverse beds -----4__ o 10 20 m iiiiiiiiiiiiiii~!5iiiiiiiii~~ LEGEND: Ii:.:.W~S andstone 1.::--.:: 1 Shale 1/'-/1 Fractures [SJ Fault Figure 2. ~ologic section - Donggongon. December 1995 ...... +:- 5: l: m m o en~" r~ (j) :r: ~ :n=n ." ?> ?' o s:: ~ Z Gl ~ Z o (j) z~ c o Figure 3. Steeply dipping outcrop repetitions sequence of sandstone and interbedded sandstone and shale. Location: Donggongon, Kota Kinabalu. Z I '- ----l ~ :r: :0 ~ <:> :- ~ " ~ ;:;- "- ""~. ~ ..,.~ S· ~ GEOLOGY OF KOTA KINABALU AND ITS IMPLICATIONS TO GROUNDWATER POTENTIAL 15 Crocker Formation Quaternary Alluvium The study area is generally underlain by the The Quaternary Alluvium is restricted to the Late Eocene-Lower Miocene Crocker Formation low lands of Kota Kinabalu. It is mainly represented (Fig. 2). It is a submarine fan to basin plain deposit by unconsolidated alluvial sediments on river composed ofthree units of sandstone, shale and the terraces and floodplains consisting of varying interlayered sandstone-siltstone-shale. proportions of unsorted to well sorted gravel, sand, and silt with minor amounts of clay which were Sandstone Unit derived from the upstream bedrock. The sandstone unit is the thickest unit in the Crocker Formation. Individual bed thickness exceed STRUCTURES 4 meters and occasionally reach a maximum of 25 meters. It is light grey to cream coloured, medium The present geologic structural investigations to coarse-grained, and sometimes pebbly. It is (Fig. 7) based on photogeologic interpretations and highly folded, faulted, jointed, fractured and field observations reveal that the study area is occasionally cavernous. It is surficially oxidized controlled by heavy structural lineaments mainly and exhibit spheroidal weathering. The sandstone represented by major folds, thrust, normal or wrench occasionally exhibits an incomplete Bouma's faults, and sheared zones. These observations sequence starting from graded bedding at the base, confirm Tongkul's (1987) earlier work that the followed by parallel lamination and topped by structures are closely associated with each other siltstone and shale. The other sedimentary and often difficult to separate and describe structures observed within the sandstone are mud individually. Movements