Indonesian Journal of Geography.
Vol 54.
No.
ISSN 2354-9114 .
ISSN 0024-9521 .
Indonesian Journal of Geography Vol 57.
No.
: 617-627
DOI: 10.
22146/ijg.
113432 website: htps://jurnal.
id/ijg A2025 Faculty of Geography UGM and The Indonesian Geographers Association ARTICLEARTICLE
REVIEW
RESEARCH
Flood Risk Mapping UsingofGIS Multi-Criteria at Nanga Pinoh West The origin and evolution Menui Basin, partAnalysis of the Matarombeo Terrain.
Kalimantan Area Southeastern Arm of Sulawesi.
Based on Geological and Geophysical Data Eviliyanto3.
Dony Andrasmoro *Ajun Purwanto Rustam Saptono Budi Samodra Sugeng Sapto Surjono*1.
Donatus Hendra Amijaya1.
Wiwit Suryanto2
1,3,4
Departmen of Geography Education IKIP PGRI Pontianak Faculty of Engineering.
Universitas Gadjah Mada.
Indonesia 2Departmen of Counseling Guidance Education IKIP PGRI Pontianak Faculty of Mathematics and Natural Sciences.
Universitas Gadjah Mada.
Indonesia Abstract.
is one of the disasters often hit various in Indonesia, in Sulawesi West Kalimantan.
Abstract.
Flood Menui Sub-basin is part that of Matarombeo in south-east arm of Island Ae The floods in Nanga Pinohterrain District,geologically Melawi Regency, 18 villages thousandsFault, of houses.
Therefore.
Indonesia.
Matarombeo is bounded by Matano Fault.
Lawanopo and Tolo Trust.
to mappart areas in Nanga Pinoh Secondary data on Different of risk Matarombeo Terrain Mountain.
Menui Sub-basin is located rainfall, flowTerrain, density,covered soil type, land of of Matarombeo by sea Toloanalyzed Bay.
The aim thismulti-criteria research is toGIS The results showed that the location had low, and high risks.
found that areas with basin used.
and evolution of Menui Sub-basin, on geomorphological Flood Risk.
GIS.
Multi-Criteria and low class areanalysis.
1,515.
95Research ha, 30,194.
ha, 21,953.
ha, andimage 14 ha, included IFSAR Analysis.
Nanga Pinoh These that the GISlaboratory approach analysis and multi-criteria analysis are paleontology, effective tools for flood risk such as petrography, in anticipating greater losses and mitigating Key words:
and helpful sub surface Geologic and tructural were collected from surface mapping in land of Matarombeo, but sub-surface interpretation beneath Tolo bay were taken from gravity and seismic data.
Menui Sub-basin.
A2022 by the authors.
Licensee Indonesian Journal of Geography.
Indonesia.
*Correspondeny email:
Stratigraphically.
Ae Oligocene ophiolite series which thrusted above Mesozoic This article is an open access article the termsof andCretaceous conditions of the Creative Commons Tectonostratigraphic ajunpurwanto@ikippgriptk.
Attribution(CC BY NC) licensehttps://creativecommons.
org/licenses/by-nc/4.
sedimentary rocks from the continental crust origin.
Unconformably above those two rock groups deposited RiftingAe molasse group on Miocene.
The study area has been affected by three different tectonic stress phases.
Formation driftingAeorogenic and evolution of Menui Sub-Basin is characterized by several distinct events.
The events begin from its history as part of Australia .
re-rifting sequenc.
, the detachment Australia .
yn-rifting in the from of Westsequenc.
Kalimantan.
This Introductin to its present location .
yn-drifting sequenc.
Sulawesi .
yn-orogen occurred within the Nanga Pinoh Police jurisdiction, including Floods occur when a river exceeds its storage capacity, and post-orogen sequence.
Tanjung Lay Village.
Tembawang Panjang.
Pal Village.
Tanjung Received:
Received:2021-12-22 2025-11-24 Accepted: 2022-10-13 Revised: 2025-12-13 Accepted: 2025-12-31 Keywords:
Published: 2025-12-31 forcing the excess water to overflow the banks and fill the Correspondent Niaga.
Kenual.
Baru and Sidomulyo Village in Nanga Pinoh low-lying ThisA2025 theJournal of by the authors and Indonesian Geography sugengssurjono@ugm.
Spectacle.
Melawi Regencyof(Supriyadi.
This article is an open access article distributed under the terms and conditions the Creative Commons Attribution(CC BY&NC) licensehttps://creativecommons.
org/licenses/by-nc/4.
The flood disaster in Melawi Regency should be mitigated worldwide (Rincyn et al.
, 2018.
Zwenzner Voigt, to minimize future consequences by mapping the risk.
specifically Indonesia.
Flooding is one of the most devastating Various technologies such as Remote Sensing and Geographic disasters that yearly damage natural and man-made features Informationstrategy Systemsthat been developed for monitoring (Du Falguni Singh.
Tehrany analysis,flood Introduction This Youssef geology, and geophysical interpretation to improve the to regionAos Eastern Indonesia represents one of the most structurally monitoring and damage assessment helpful for the disaster Thereregions are flood risks the in many system,inshaped Mardiana.
Haq (Alfieri Mahmoud Gan, by the long-term interaction of the Australian.
Eurasian, and The Menui Sub-basin(Biswajeet is located&on the southeast Pradhan Furthermore.
PacificAePhilippine Sea plates (Hamilton, 1979.
Hutchison, of the Matarombeo Terrain, which is characterized by the have been developed map flood (FalguniHall, & Singh.
Komolafe et al.
TheGeographic, regionAos geological of intricatetostructural.
These Rincyn Skilodimou The reflects a protracted history of subduction initiation, arcAe aspects that define the larger Southeast Arm of Sulawesi of Remote2.
SensingThe (RS)Tampakura and Geographic Systems include losscollision, of humanmicrocontinental life, adverse impacts on the population, and strike(Surono, and Information Eemoiko carbonate (GIS) slip fragmentation, producing a highly heterogeneous formations are found across the basin and have reservoirflood disasters , 2.
animals,framework the spreadthat of diseases, water contamination continues and to evolve through active features(Haq porosity and internal layering, (Rincyn deformation (Ali & Hall, 1.
Within this broader tectonic according to geologicaltechnology, and seismic Geographical Information System (GIS) and Food mosaic.
Sulawesi occupies a particularly complex position: its (Samodra et al.
, 2.
These units seem to have formed Remote Sensing intoMatarombeo other datasets in quantity and losses,is respectively et al.
, 2019.
Petitpresent a composite (Lyu of ophiolitic to the (RS) blockAos and assessing Boix et al.
, 2.
the occurrence arcs, and active for According to complementary (Biswajeet Mardiana.
Haq (Komolafe assembled during successive Neogene convergence and the Southeast ArmAos structural segmentation andal.
,tectonic Pradhan et al.
Understanding causes of flooding Rozalis et al.
(Hall.
The 2012.
floods include Surono, are 2.
in the regionAosthe (Ozkan Tarhan.
Zhou which is made up of varying thick crustal chunks delimited The Matarombeo area is located in the southeast of Different flood(Triani land structure (Jha etThe ,southeast Zwenzner & Voigt,geologically 2.
, and large faults , 2021.
Mirnanda , 2.
Sulawesi.
Indonesia.
arm of Sulawesi areasAo (Curebal Despite significant regional reconstructions (Hall, 2.
, the is a part of the Continental Terrain geologic province, which floodingSub-basin These important for the Other causes are land-use change, as deforestation Menui lacks anprocesses in Australia-New Guineasuch the Cenozoic and (Huong Pathirana.
Rincyn model that combines stratigraphy, structuralpreventing geology, and It is bordered to the northeast by the Eastern Sulawesi Ophiolit Zhang Zhou geophysical interpretation.
Therefore, the purpose of this Belt, to the southeast by the Buton Terrain, to the east by the Tolo ,lithostratigraphic Falguni & Singh.
Mandal The high in thebylast caused much is to(Bubeck Trench, and to the north Banggai Sula Chakrabarty.
Shafapour Tehrany sub-districts West Kalimantan the structural architecture, and recreate the tectonic evolution (Surono et al.
, 2013.
Serhalawan & Chen, 2.
Matano Fault.
GISbasin.
and remote map the Thousands Fault, of houses 18 villages in Melawi of the A crucialsensing for comprehending basinAos Lawanopo and inTolo Trust encircle theRegency Matarombeo development is provided by the regionAos larger configuration, region (Figure .
This intricacy highlights the necessity of an THE ORIGIN AND EVOLUTION OF THE MENUI BASIN.
Saptono Budi Samodra, et al.
which consists of uplifted mountains in the northwest and a subsiding marine depocenter in the southeast under the control of significant structures like the Matano and Lawanopo mapping, and orientation data .
uch as bedding, fault planes, and shear indicator.
gathered from specific exposures in the Southeast Arm of Sulawesi.
These outcrops, mainly located in the Matarombeo Mountains and coastal areas of Menui Island, offer direct insights into lithostratigraphy, deformation styles, and tectonic history.
The classification of lithostratigraphy adheres to established methods for sedimentary basin analysis, integrating macroscopic lithology, sedimentary structures, bed contacts, and facies associations.
Facies analysis is performed Materials and Methods This research combines various geological and geophysical datasets to reconstruct the formation and development of the Menui Sub-basin.
Geological field data includes measurements of stratigraphic sections, descriptions of lithofacies, structural Figure 1.
Location of the study (Matarombeo Terrai.
in geological province of Sulawesi and adjacent Islands Map (Moss and Wilson, 1.
The Menui Sub-basin is located on the southeast edge of the Matarombeo Terrain where geologically bounded by Matano Fault.
Lawanopo Fault, and Tolo Trust.
Indonesian Journal of Geography.
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through a process-based interpretation, categorizing facies into depositional environments like deep-marine turbidites, shallow-marine carbonates, or syn-tectonic siliciclastics.
Structural analysis encompasses field structural measurements, geological maps (Surono, 2.
, and interpretations derived from remote sensing.
Kinematic indicators, including slickenlines, drag folds, fault gouge fabrics, and fractured zones, are utilized to deduce stress regimes and the history of fault movements.
Balanced and restored crosections are created along representative geological transects to assess structural styles and the chronology of deformation.
Fault kinematics are examined through stereonet-based stress inversion, which includes principal stress orientation and fault-slip indicators, facilitating the identification of extensional, compressional, or strike-slip phases pertinent to basin formation.
The geophysical dataset comprises gravity data, 2D seismic reflection profiles, and SRTM DEM that traverse the Menui Sub-basin.
A remote sensing method was employed to obtain preliminary geological information about the The analysis of IFSAR imagery data, supplemented by secondary data and ground verification, culminated in the geological map of the study area (Figure .
Subsurface interpretations beneath the Menui Sub-basin were derived from gravity and seismic data.
This information, combined with literature reviews from previous researchers, contributed to the development of a model for the formation and evolution of the Menui Sub-basin.
Seismic interpretation adheres to a systematic workflow utilizing industry-standard software.
Initially, seismic profiles undergo preconditioning through the application of basic filters and checks for velocity consistency.
Horizon picking is executed by analyzing reflection terminations, amplitude patterns, and seismic facies boundaries.
Fault mapping employs vertical and lateral discontinuities, reflector offsets, and coherence attributes to identify normal, reverse, and strike-slip faults.
Structural measurements, geological maps (Surono, 2.
, and remote-sensing interpretations.
Kinematic indicators such as slickenlines, drag folds, fault gouge fabrics, and fractured zones are used to infer stress regimes and fault movement Balanced and restored cross-sections are constructed along representative geological transects to evaluate structural style and deformation chronology.
Figure 2.
Geological map of the Matarombeo Basin.
Southeastern Arm of Sulawesi.
The map highlights contrasting lithostratigraphic domains, including ophiolitic complexes, sedimentary formations (Pandua.
Tampakura.
Tokala.
Masiku, and Wasupond.
, mylange zones, and alluvial deposits.
THE ORIGIN AND EVOLUTION OF THE MENUI BASIN,
Saptono Budi Samodra, et al.
Fault kinematics are analyzed using stereonet-based stress inversion .
rincipal stress orientation, fault-slip indicator.
, enabling the identification of extensional, compressional, or strike-slip phases relevant to basin formation.
The geophysical dataset includes gravity, 2D seismic reflection profiles, and SRTM DEM crossing the Menui Subbasin.
Remote sensing method was used to get the preliminary information about the geology of the area.
Analysis of the IFSAR imagery data followed by the study from secondary data and ground checking resulting in the geological map of the study area (Figure .
Subsurface interpretation beneath Menui Sub-basin were taken from gravity and seismic data.
The result combined with literature study from previous researcher to make a model of Menui Sub-basin formation and evolution.
Seismic interpretation follows a structured workflow using industry-standard software.
First, seismic profiles are preconditioned by applying basic filters and velocity consistency checks.
Horizon picking is performed using reflection terminations, amplitude patterns, and seismic facies boundaries.
Fault mapping uses vertical and lateral discontinuities, reflector offsets, and coherence attributes to delineate normal, reverse, and strike-slip faults.
Seismic facies analysis employs reflection geometry, amplitude, continuity, and frequency content to infer depositional processes, following the classical framework of Mitchum et.
Key stratigraphic sequences are correlated to regional formations such as the Basement.
Tampakura, and Eemoiko, based on reflector character and well-seismic tie processed.
Gravity datasets are processed using upward continuation and 2D forward modelling.
These geophysical models help constrain basement depth, crustal heterogeneity, and major fault boundaries not fully resolved in seismic lines.
Reconstruction of the tectonostratigraphic evolution of the Menui Sub-basin employs qualitative and semiquantitative basin modelling techniques.
Stratigraphic sequences are arranged chronologically based on field data, seismic interpretation, and regional geological frameworks (Hall, 2012.
Wilson & Moss, 1.
Basin-forming mechanisms are identified using diagnostic criteria including subsidence patterns, sedimentary facies shifts, and syn-tectonic thickening.
Key stratigraphic sequences are correlated to regional formations such as the Basement.
Tampakura, and Eemoiko, based on reflector character and well-seismic tie processed.
Gravity datasets are processed using upward continuation and 2D forward modelling.
These geophysical models help constrain basement depth, crustal heterogeneity, and major fault boundaries not fully resolved in seismic lines.
Reconstruction of the tectonostratigraphic evolution of the Menui Sub-basin employs qualitative and semiquantitative basin modelling techniques.
Stratigraphic sequences are arranged chronologically based on field data, seismic interpretation, and regional geological frameworks (Hall, 2012.
Wilson & Moss, 1.
Basin-forming mechanisms are identified using diagnostic criteria including subsidence patterns, sedimentary facies shifts, and syn-tectonic thickening.
Result and Discussion Geological and Lithofacies Characteristics The Matarombeo Terrain exhibits a significant contrast between its northwestern and southeastern areas (Figure .
The northwestern part is defined by the rugged Matarombeo Figure 3.
The Matarombeo Terrain is divided into two primary domains: the northwestern onshore sector, noted for its rugged mountainous landscape, and the southeastern offshore sector, which encompasses the Menui Sub-basin.
This sub-basin features depositional regions and a series of islands that are integral to the basin-margin system.
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MountainsAian elevated, structurally intricate region primarily composed of metamorphic, ophiolitic, and sedimentary formations (Surono, 2.
Conversely, the southeastern area is marked by transitions towards the sea and encompasses the Menui Sub-basin, which serves as a marine depocenter that is structurally located next to the plifted terrain.
Significant physiographic characteristics encompass the Matarombeo Mountains, which constitute a notable structural elevation made up of metamorphic and ophiolitic blocks, as well as the Menui IslandAeBone Bay margin system, which delineates the seaward transition from an uplifted terrane to a marine depocenter.
The Matarombeo high serves as the terrestrial manifestation of the terrainAos intricate assembly and plays a crucial role in influencing sediment provenance and basin geometry.
in contrast, the Menui Sub-basin captures the marine deposition of sediments originating from these elevations and from upstream catchments during periods of active deformation (Surono, 2013.
Samodra et.
, 2.
Stratigraphically (Figure .
, study area consist of Cretaceous Ae Oligocene ophiolite series which thrusted above Mesozoic sedimentary rocks from the continental crust origin.
nconformably above those two rock groups deposited molasse group on Miocene (Figure 4.
) (Darman & Sidi, 2000.
Rusmana , 1993.
Rusmana & Sukarna, 1985.
Simandjuntak et.
Simandjuntak et.
, 1993: Surono, 2.
The TriassicAeJurassic Meluhu Formation crops out along a northAesouth belt on the eastern coast of Southeast Sulawesi and consists of shale, sandstone, and calcareous sandstone (Simandjuntak & Surono, 1994.
Surono, 2.
The lithological sequence exhibits a distinct coarsening-upward The lower section is primarily composed of wellsorted quartz sandstone, succeeded by layers of carbonaceous shale interspersed with quartz sandstone.
In the upper section, calcareous sandstone is present.
Outcrop structures include scour marks, cross-bedding, ripple marks, graded bedding, and cross-lamination, while wavy bedding at the base indicates deposition in a tidal-flat setting (Bishop, 2.
The TriassicAeJurassic Tokala Formation, distributed in the northern and southern parts of the study area, interfingers with the Meluhu Formation (Simandjuntak & Surono, 1.
It comprises calcareous oil shale, wackestone, and mudstone.
The lower calcareous shale contains oil-rich beds interpreted as potential source rocks.
Up-section, it coarsens upward into interbedded calcareous shale and mudstone, with graded bedding and cross-bedding commonly observed.
The Matano Formation is widely exposed in the northern area (Surono, 2013.
Sukido et al.
, 1.
It consists of limestone, shale, and polymict conglomerate.
Two facies occur: .
a conglomeratic limestone unit that fines upward.
interbedded mudstoneAewackestone with claystone Figure 4.
Stratigraphic column of Matarombeo Terrain
THE ORIGIN AND EVOLUTION OF THE MENUI BASIN,
Saptono Budi Samodra, et al.
and carbonaceous layers.
Graded bedding and basal scours are common, and the limestone is compact and highly cemented.
The Ophiolite Complex, forming part of the East Sulawesi Ophiolite Belt, is exposed in the central and northern regions and includes gabbro, dunite, peridotite, and serpentinite (Monnier et al.
, 2003.
Surono, 2.
Peridotite is medium weathered and holocrystalline, whereas serpentinite is greenish-black and moderately weathered.
Many outcrops are highly fractured and filled with secondary magnesite and malachite minerals.
The Tampakura Formation, exposed along the Laronai Coast and Sambalangi, comprises interbedded limestone and calcareous sandstone (Samodra et al.
, 2018.
Surono, 2.
The limestone is fine-grained and well cemented, while the calcareous sandstone is matrix-supported and poorly sorted.
Both units show graded bedding and parallel lamination.
The Langkowala Formation, exposed in Atarilama and Landipa, unconformably overlies the Tampakura Formation (Sukamto, 1.
It contains conglomerate, sandstone, claystone, and local calcarenite.
The formation shows a coarsening- and thickening-upward trend.
Conglomerates are poorly sorted, quartz-rich, and compact.
sandstone is wellsorted quartzose.
and calcarenite contains mollusk fragments and is petrographically classified as micritic sandstone.
The Eemoiko Formation, found in Wasana and Wolasi, interfingers with the Boepinang Formation and is dominated by rudstone (Samodra et al.
, 2.
The Wasana section is dominated by coral fragments, whereas the Wolasi section includes pelecypod, gastropod, echinoderm, and algal Petrography confirms a rudstone classification with large foraminifera.
The Boepinang Formation, covering the Moramo and Wolasi areas.
It consists of marl, conglomerate, calcareous sandstone, and local breccia (Simandjuntak & Surono, 1.
Its succession fines upward, beginning with marlAecalcareous sandstone interbeds, followed by calcareous sandstone with marl and conglomerate, and capped by conglomeratic marlrich intervals.
Structures include scours and graded bedding.
The Pandua Formation, overlying the Boepinang Formation conformably, is dominated by interbedded sandstoneAeconglomerate (Surono, 2.
Sandstone is wellsorted quartzose, while conglomerates are matrix-supported with quartz and lithic clasts and show normal grading and The Alangga Formation, distributed in the southern area, overlies the Boepinang Formation and comprises sandstone, siltstone, and conglomerate (Sukido et al.
, 1.
It shows a coarsening-upward succession from conglomerate at the base to interbedded sandstoneAesiltstone, then to thick conglomerate and sandstoneAeshale interbeds.
Common structures include scours and planar cross-beds.
The Buara Formation, exposed in the southeastern study area, interfingers with the Alangga formation (Surono, 2.
It consists of reefal limestone, floatstone with molluscan fragments, interbedded rudstone, and shale.
The youngest sediments cover all lowland area are alluvial deposits, consist of clay, sand, and gravel.
Several outcrops of lithological variations found in the research area are shown in Figure 5.
Structural Framework Major geological structures on the study area are the sinistral Matano and Lawanopo faults that formed after the collision event (Surono, 2010.
Hamilton, 1.
, and Tolo thrust (Figure 1 & Figure .
These three geological structures are part of the main structures on the island of Sulawesi.
The Matano Fault is a sinistral fault with a northwestsoutheast trend through Lake Matano (Surono, 2010.
Lukman, et al.
, 2.
The length of the fault reaches 200 km, from the intersection with the Palu-Koro Fault in the west, to the east to Figure 5.
The Outcrop distribution of lithological unit in Matarombeo Terrain.
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the Tolo Thrust.
The apparent offset of this fault is estimated at 20 kilometers (Hamilton, 1.
, based on the distribution of ultramafic rock.
Mesozoic sedimentary rock, and metamorphic rock that shifted 19 Ae 20 km to the left on the opposite side of the lake.
This fault is characterized by a rifting zone that affects river flow patterns and forms Matano Lake with a depth of up to 600 m, and is associated with the Palu Koro Fault System in the west and is thought to be associated with the Sorong Fault in the east (Surono, 2.
The fault is still active today based on its seismic activity (Hamilton, 1974 in Hamilton, 1979 and Surono, 2.
The Lawanopo Fault is part of the main northwestsoutheast trending fault that passes through the Lawanopo Plain (Hamilton, 1979.
Triani et al.
, 2.
This fault system extends for about 260 km from the north of Malili to Tanjung Toronipa, connecting with the Matano Fault in the west and the Hamilton Fault in the east.
The magnitude of the apparent displacement is estimated at 25 km based on the shift of the Meluhu Formation which is cut off by the fault (Surono.
Hamilton .
argues that this fault was active in the Neogene period and is no longer active today.
Based on a georadar survey in the area cut by the Lawanopo fault.
Natawijaya and Daryono .
stated that the Lawanopo Fault is no longer active based on evidence that this fault does not cut Pleistocene Ae Holocene deposits.
The Tolo Thrust is the boundary between the microcontinent in the Southeast arm of Sulawesi and the northern Banda Sea.
This fault is a long fault, curved like an arc that cuts through Tolo Bay.
The location and structure of the Tolo Thrust can be well observed as a result of the expeditions of the Mariana 9 and Indopac 10 survey vessels in 1977 and In the north, the Tolo Thrust merges with the Matano Fault on the mainland, while in the south it splits into several faults that cut the central and eastern parts of Buton Island.
The deformation zone associated with this fault is greatest in the middle, and narrows at the ends (Silver et al.
, 1.
Hamilton .
suspected that the Matano Fault intersects the Tolo Thrust, but Silver et al.
, .
stated that the Matano Fault is a continuation of the Tolo Thrust.
With this view, there is a continuity of the tectonic zone from Buton to the north to the Matano Fault, then to the northwest along the Palu Fault to the North Sulawesi Trench.
The Matano Fault represents the transform system between the Tolo Thrust and the North Sulawesi Trench.
The study area have been affected by three different tectonic stress phases.
The oldest phase had N 353A E direction and occurred at least until Cretaceous, the second phase had N 283A E principal stress direction and occurred in Paleocene Ae Oligocene, and the youngest phase have N 45A E principal stress direction and occurred in Miocene Ae Holocene (Figure Subsurface Architecture The residual gravity field across southeastern Sulawesi provides an independent constraint on crustal architecture (Nugraha et.
Al.
, 2.
and strengthens the geological and seismic interpretations (Figure .
A prominent NEAeSWtrending gravity gradient delineates a first-order boundary Figure 6.
Main tectonic stress in study area based on structural lineament analysis.
THE ORIGIN AND EVOLUTION OF THE MENUI BASIN,
Saptono Budi Samodra, et al.
between contrasting crustal domains.
Low gravity values dominate the northwestern sector, corresponding to the uplifted Matarombeo Terrain and the adjacent Menui Subbasin.
These subdued anomalies reflect mixed metamorphic, ophiolitic, and sedimentary assemblages overlying a relatively felsic continental-type basement, consistent with long- standing models of SulawesiAos composite crust (Hamilton.
Hall, 2012.
Surono, 2.
The strong gravity gradient delineates a major structural boundary separating the uplifted Matarombeo Terrain including Menui Sub-basin from the subsiding North Banda Sea.
Coordinates are shown in geographic format, and shading Figure 7.
The residual gravity anomaly map for the southeastern region of Sulawesi depicts the spatial differences in residual gravity values.
These values range from low anomalies, indicated by lighter shades, which are linked to dense crystalline and ophiolitic sedimentary deposits situated above granitic basement rocks in the northwestern area, to high anomalies, represented by darker shades, that signify the presence of relatively high-density oceanic crust in the southeastern offshore region.
Figure 8.
Two-dimensional .
D) cross-section derived from residual gravity anomaly data illustrating the subsurface configuration of the Menui Subbasin.
The residual gravity response highlights lateral variations in crustal density, delineating the transition from continental crust to oceanic crust beneath the study area.
The Menui Subbasin is characterized by a relative gravity low, interpreted as a sediment-filled depocenter developed above attenuated continental crust and adjacent to the oceanic The modeled section also depicts the geometry of the upper mantle and the crustAemantle boundary, providing insights into the tectonic framework and basin evolution of the Matarombeo Basin.
Indonesian Journal of Geography.
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indicates anomaly magnitude .
n mGa.
, highlighting the fault-controlled nature and asymmetric geometry of the basin.
In contrast, the southeastern offshore region displays significantly higher gravity amplitudes, which are indicative of a dense oceanic lithosphere located within the North Banda Sea.
This observation is consistent with geophysical studies that document the properties of oceanic crust and the presence of high-density mantle material in the Banda arc system (Spakman & Hall, 2010.
Wessel & Smith, 1.
The 2-dimensional model of the residual gravity map can be seen in Figure 8.
The abrupt transition between these domains signifies a major lithospheric discontinuity that has likely experienced repeated reactivation during the Neogene period.
Its alignment with regional fault systems implies a structural influence on subsidence patterns and the formation of the Menui Sub-basin (Panggabean & Surono, 2013.
Mirnanda et al.
, 2.
Within the central part of this boundary zone, the Menui Sub-basin is distinguished by lower gravity values and a smoother anomaly texture, features indicative of thick accumulations of low-density sedimentary fill within a faultbounded depocenter (Wessel & Smith, 1998.
Mirnanda et al.
To the east, a sharply defined, convex-eastward gradient marks the transition to oceanic crust and mirrors regional models of lateral extrusion and escape tectonics associated with the oblique collision of the BanggaiAeSula microcontinent with northern and eastern Sulawesi (Hamilton, 1979.
Hall.
Spencer et al.
, 2.
This geometry implies crustal draping and outward displacement along strike-slip or oblique-convergent structures.
Collectively, the gravity patterns support an interpretation in which the Menui Subbasin formed as an asymmetric, fault-controlled depression along an evolving terrane boundary, shaped by transtensional deformation, differential uplift, and regional plate interactions (Doust & Sumner, 2007.
Panggabean & Surono, 2.
There are nine significant seismic reflections were identified within the 2D seismic data (Figure .
, representing four tectonostratigraphic units.
The seismic reflectors defining these units are: top basement (TB Ae basement Horizo.
synrift Sequence (SRS Ae Meluhu Horizo.
syn-drift sequence (SDS Ae Tampakura Horizo.
and syn-collosion sequence (SCS Ae Langkowala.
Eemoeko.
Boepinang.
Pandua and Alangga Horizon.
Formation and evolution of Menui Sub-Basin Formation and evolution of Menui Sub-basin is characterized by several distinct events, correlated with tectonic development in East Indonesia Regime.
According to Davidson .
, the events begin from its history as part of Australia .
re-rifting sequenc.
, the detachment from Australia .
yn-rifting sequenc.
, movement to its present location .
yn-drifting sequenc.
and during and after the collision with SE Sulawesi .
yn-orogen and post-orogen sequence.
(Figure 10.
Pre-rift and Syn-rift Sequence Pre-rift sediments were deposited before the Middle Triassic when the continent was part of the AustraliaNew Guinea continent.
The pre-rift Triassic stratigraphy comprises continental-derived clastic sediments deposited unconformably on Permian meta-sedimentary rocks.
Final separation from Australia happened in the Late Triassic or Early Jurassic, preceded by a transition from pre-rift to syn-rift sedimentation in the Middle Ae Late Triassic.
Meluhu Formation.
Meluhu Formation itself is slightly younger and interfingering with Early Jurassic Tokala Formation predominantly consists of limestone.
Clastic sediments, mostly shales, are common in the Meluhu Formation.
Syn-drifting Sequence A fully open marine environment with passive margin sedimentation commenced in the Late Cretaceous to Early Tertiary with pelagic carbonates as dominant lithology.
The sequence begins with the deep-marine siliceous and calcareous mudstones of the Tampakura Formation.
Tampakura Formation consists of pelagic limestone with nodule sand stringers of red chert.
As a whole, carbonates interval from Tampakura was deposited very slow, and their lithology is consistent with deposition during the drift of an isolated continental fragment.
This event is also marked by the decrease in clastic sedimentation derived from the continental Figure 9.
SW-NE orientated 2D seismic line across the center part of study area showing the cross-sectional view of the Menui Sub-Basin.
Seismic amplitude character is shown down until 4.
6s TWT.
A seismic section showing the nine reflectors interpreted in this study that represent four main tectonostratigraphic units Saptono Budi Samodra, et al.
THE ORIGIN AND EVOLUTION OF THE MENUI BASIN,
Figure 10.
Schematic Origin and Evolution of Menui Sub Basin.
Syn-orogeny Sequences In the Late Miocene, the collision of microcontinents and SE Sulawesi took place.
In this event.
Langkowala.
Eomoeko, and Boipinang Formation were deposited.
A hiatus at the top of the carbonate sequences can be attributed to this collision.
After the collision, syn-orogenic sediments were deposited as molasses (Pandua and Alangga Formatio.
with interfingering siliciclastic units, indicate episodic shifts in base level and sediment supply governed by syn-rift and postrift tectonics.
The Menui Sub-basin did not develop as a straightforward sag or a standalone depocenter.
instead, it emerged as an asymmetric, structurally compartmentalized basin influenced by terrane uplift, transtensional escape mechanisms, and varying rates of subsidence.
Its tectonostratigraphic framework illustrates the close relationship between deformation and sedimentation that defines the southeastern margin of Sulawesi.
Conclusions The evolution of the Menui Sub-basin is best explained as the product of a dynamically partitioned tectonostratigraphic system situated along the southeastern margin of the Matarombeo Terrain.
Its genesis began with fault-controlled subsidence during Neogene transtensional deformation, driven by the progressive uplift of the Matarombeo block to the northwest and coeval crustal thinning toward the North Banda Sea.
Residual gravity data support this configuration, suggesting a distinct transition from the low-density continental crust located beneath the basin to the high-density oceanic lithosphere to the east.
This transition signifies a significant lithospheric boundary that is linked to lateral extrusion during the oblique BanggaiAeSula collision.
Stratigraphically, the basin illustrates the interaction between structural segmentation and sedimentation.
The occurrence of carbonate units from the Tampakura and Eemoiko formationsAirecognized for their reservoir potentialAiindicates deposition along fault-bounded highs and localized accommodation zones.
These successions, together References