Structure Pattern of Volcanic Degradation Landform of Citarik Sub-Catchment Based on Lineaments And Drainage Basin Morphometric.

Structure Pattern of Volcanic Degradation Landform

of Citarik Sub-Catchment Based on Lineaments

And Drainage Basin Morphometric

By:

Edi Tri Haryanto, Adi Hardiyono, Iyan Haryanto, Undang Mardiana

Faculty of Engineering Geology, Padjadjaran University. Jln. Raya Bandung-Sumedang Km 21, Jatinangor Telp./Fax. (022) 7796545 Kode Pos 45363, e-mail : ftg@unpad.ac.id

Website :http://ftgeologi.unpad.ac.id

ABSTRACT

Citarik Catchment Area, one of the main sub-catchments of Upper Citarum River Basin, found not any line structural symbol on geological maps, although some indications i.e, drainage pattern from topographical maps and linements of mountain ridges and valley based on DEM depicted clearly. Therefore the initial study to uderstand the tectonic venomena through the analysis of structure pattern, based on chatchments morphometric data and lineaments generated from Topographic Map and DEM of Global Mapper Open sources data and fieldwork has been conducted . The results could be inferred that the first order stream has three different dominant which is trending NW-SE, NNE-SSWand NE-SW, WE. The second order lineaments which still in line with the first orde catchments seems that the existence has been controlled beside by joint structure, has also been influenced directly by fault structures. Based on third order lineament, the main stress direction can generate patterns of E-W trending structure with a type of thrust fault and a normal fault, whereas the NW-SE direction and a NE-SW forming ahorizontal fault. Fault structure with a N-S direction are generally normal fault type.

Keywords : catchment- order, volcanic-degradation-landform, structure-pattern.

I. Introduction

Based on Regional Geological Map of Bandung and other adjacent sheets, there are many tectonic activities indicated by line faults symbols spread out the area of Upper Citarum River Basin or popularly mentioned as “Bandung Basin” or “Cekungan Bandung”( figure 1). The most popular fault among the local geologists in this area is Lembang Fault located in the north of Bandung City, and many others fault based on map scattered from the west to the southeastern part of the southern slope of Bandung Basin. Curiously, there was not found any fault line symbols in the map in Citarik Catchment Area one of the main sub-catchments of Upper Citarum River Basin, , although some indications i.e, drainage pattern from topographical maps and linements of mountains ridges and valley based on DEM from Global Mapper data depicted clear enough.

Joints have a close connection with the tectonic structure (Harding, T. P. 1974). Joint is defined as fractures with little or no a shift ; shifting of joint structure generaly can only be observed under a microscope (Ramsay, 1987), meaning that megaskopis difficult to observe a

shift (Billing, 1972). Rock cracks or joints can be influenced by either fault structures or master joints. Stream can be ascertained controlled by joints system. Therefore the initial study based on analyzing drainage basin lineaments of Citarik Sub-catchments from maps and field work was conducted.

Figure 1. Tectonic Setting of Citarik Catchment Area in the Upper Citarum Catchment Area or River Basin

II. Objectives

The objectives of study were to understand general structure pattern and tectonic fenomena on Volcanic Fluvial Degradation Landform of Citarik Sub-Catchment using characteristic of river catchments morphometric and lineaments analysis approach.

III. Methodology

Methodology used to analyse structure pattern of Volcanic Degradation Landform of Citarik Sub-Catchment were mainly Geographical Information System (GIS) techniques. For obtaining basin morphometric data and lineaments measured from digital topographic maps and Digital Elevation Model (DEM) from open sources Global Mapper programs. Constructing Rossette and Pole Diagram for analyzing joints direction, and fieldwork for obtaining joints data in the field.

IV. Location

Citarik Catchment Area are located in the most eastern part of Upper Citarum Catchment. It has an area of about 265 sq km, geographicaly spreaded between longitude 107o_{42’7”E and}

area is about 25 km to the east direction. The study area is included in the district of Sumedang and Bandung, West-Java Province and the analysis was concentrated in slope zone of volcanic fluvial degradation landform of Upper Citarum Catchment Area. Topographic situation of the area is pressented in figure 2.

Figure 2. Topographic situation of study area

Based on Regional Geological Map, scale of 1 to 100,000 Bandung sheet (Silitonga, 1975), Garut and Pameumpeuk sheets (Alzwar et. al, 1992) belonged to geologic formation of : plain of lacustrine deposit and sloping area insisted by several valleys/basins of volcanic fluvial degradation land form consisting of the Young and the Old Undifferentiated Volcanic Product (figure 3).

Study area concentrated was analysis in some catchments area in relation with geological setting. Based on Strahler’s river ordering system, there were 6 (six) catchments consisting of 1 (one) of five order catchment and 5 (five) of fore order catchments(figure 4).

Figure 4. Distribution of Catchments as Concentrated Study Area in relation with Geological Setting

V. Result of Study

5.1. Catchment Areal Morphometry and lineaments

The first step of study was identifying and delineating catchments area, from the smallest or the first order river to the largest based on Strahler’s river order system (Chorley R.J, 1969). Delineation generate as much as 391 first order, 69 second order, and 24 third order catchments. Figure 5,6 and 7 shows from the left to the right: delineated first, second, and third order catchments spreaded five in order fore catchments and one in order five catchment, lineaments based on direction tendency of catchments order one, and the dominant lineaments direction. Circularity is the index value of roundness. 1 is the maximum index value which means catchments have a round shape, the smaller the value means that the catchments have more elongated shape. Circularity are usually written two digits after the decimal. Circularity index might be clasifyed as very elongated (0.2-0.3); elongngated (0.40-0.50); somewhat elongated (0.50-0.60); slightly rounded (0.60-0.70; rounded (>0.70). Relatively elongated shape (<0.60) provide ease of making lineament directions. In the case of rounded catchment, lineament direction was made depend on its location of river flow.

Figure 5. Delineated first order Catchments on the left, lineaments of first orde catchments in the middle, and dominance of lineaments directions on the right.

Figure 6. Delineated second order Catchments on the left, lineaments of second order in the middle, and dominance of lineaments directions of second order on the right .

Figure 7. Delineated third orde Catchments on the left, lineaments of thirdorder in the middle, and dominance of lineaments directions of third orde on the right.

5.2. Regional Tectonic Analysis

Bandung Basin is inter-mountane basin because of its location lies between the volcanoes, a structural formations such as depression, surrounded by a height of Quaternary volcanoes. Tectonic background that controls the formation of the basin, initiated by compressional tectonic structures that produce fold thrust belt at the Tertiary sedimentary rocks are now the position covered by quarternary volcanic materials(Haryanto, 2014). This tectonic activity peaked in the Late Tertiary (Martodjojo, 1984). As a result of these events, Bandung and surrounding areas become the top of the Java geantiklin zone. After the compression forces on the island of Java gradually diminish, as the equilibrium compensation formation of a number of normal faults or depression occurred. In the geometry of the structural formations named as antiklinal collapse basin, under the influence of extensional tectonics. In line with the on going extensional tectonic, volcanic activities also takes place that happens on a large scale, so that by the time it generated a lot of volcanic material and most of Tertiary sedimentary rocks covered by these volvanic materials.

In Bandung and the surrounding area, some of the existence of an ancient volcanic eruption centers form one lane lineaments with the northeast-southwest direction, so that the inferred its presence controlled by fault structures (Figure 8). Straightness of the structure in this region, also occurs in the vocanic material. This shows tectonic activity continued until the End of Pleistocene, even supposedly still active until now.

In general, based on regional geological structure, the Bandung area is surrounded by a regional fault, which is in the northern part traversed by Cimandiri and Lembang Fault, in the east by Citanduy Fault and in the south by Jampang Fault (figure 8). Throughout the regional fault, indirectly affect the geological conditions in Bandung and the surrounding area. From the analysis of DEM and field trips, the structural lineaments is not only known caused by a fault structure. Some lineament structures in the study area cut young volcanic rocks (field data figure 9), thus affecting the shape of the topography and drainage patterns. Theoretically joints structure can reach hundreds of meters, and can affect the landform.

Drainage pattern and catchments direction can be used as guidance existence of fault structures and joints structures, because both the geological structure is weak zone / destroyed that easily weathered and eroded by flowing water. In a relatively long time, the crack area as a forerunner to the formation of river channel. On the basis of this concept, the determination of local structural lineaments can be done based on interpretation of river catchments pattern or catchments direction, as depicted in above figure 5,6,and 7 .

Drainage pattern in the area of young volcanic are generaly radier, this indicates the drainage pattern is not only controlled by the structure of the cracks, but is also influenced by the geometry of a volvano that is conical shaped.

Figure 8. Lane lineaments that form ancient volcanic eruption centers in Bandung and the surrounding area (Katili and Sudradjat, 1984, modified).

5.3. Discussion First Order catchments

The first order catctments in the figure 5 above has the largest frequency compare with other river or catchments order and has a range direction. Associated with the pattern of structural lineaments in Figure 2 (second order), lineaments of first order seems to be part of the structural lineament direction of north-south, northwest-southeast and northeast-southwest. In rosette diagram of first order catchments, the dominant direction of the lineaments trending northwest-southeast. Through the polar diagram known that maxima point were spread, but the maxima biggest point still distinguishable, which is trending northwest-southeast (NW-SE), north northeast-south southwest (NNE-SSW), northeast-southwest (NE-SW) and west-east (WE). By compiling rosette and polar diagrams, it could be inferred that the first order stream has three different dominant directions as above.

Rock cracks or joints influenced either by the fault structures and the master joint, may be followed by secondary cracks (smaller size) that its formation can occur simultaneously. On the basis of dimension (length) first order stream can be ascertained the river was controlled by joint system.

Second order catchments

Lineaments according to the second order catchment has a smaller frequency, but still has a direction as diverse as the first order. However, based on the diagram Rosset and the size of its length which shows the consistency of the direction and the magnitude, then the existence of second order seems to had been controlled beside by joint structure, had also been influenced directly by fault structures. In Figure 6, the alignment of the structure have the same direction relative to the lineaments of the catchments as depicted in the diagram rosette and polar diagrams.

Third order catchments

Based on rosette and polar diagram, known that the frequency and direction of lineaments more influenced by the fault structure trending northwest-southeast. Structural lineaments with these direction were possibly a reactivation of an old fault that developed in Tertiary sedimentary rocks. Regionally, the pattern of faults that developed in West Java, influenced by the stress system trending north-south compression. By using the concept of triaxial stress, the main stress direction can generate patterns of east-west trending structure with a type of thrust fault and a normal fault, whereas the northwest-southeast direction and a northeast-southwest forming a horizontal fault. Fault structure with a north-south direction are generally normal fault type.

At the young volcanic rocks (Quaternary), structural lineaments growing in it, can also occur due to the loading of volvanic material itself, so generally normal faults. In relation with Figure 6 (second order catchments) and the dimension (length) where the order of the river is relatively long, it is concluded that the structural lineaments associated with third-order stream is a combination of fault structures, joint master and as a result of loading. Structural lineaments

associated with the faulting proccess, the fault is to be oblique(normal horizontal) or as a pure normal fault.

VI. Conclusion

The dominant direction of the lineaments of first orde river or catchments trending northwest-southeast. Through the polar diagram shows that maxima point were spread, but the maxima biggest point still distinguishable, which is trending northwest-southeast (NW-SE), north northeast-south southwest (NNE-SSW), northeast-southwest (NE-SW) and west-east (WE). Then it could be inferred that the first order stream has three different dominant directions as shown above.

Based on the directions of lineaments which still in line with the first orde catchments directions and with magnitude or the length increase, so it seems that the existence of second order catchments has been controlled beside by joint structure, has also been influenced directly by fault structures.

Using the concept of triaxial stress, the main stress direction can generate patterns of east-west trending structure with a type of thrust fault and a normal fault, whereas the northeast-west- northwest-southeast direction and a northeast-southwest forming a horizontal fault. Fault structure with a north-south direction are generally normal fault type.

Acknowledgements : deeply addressed to Prof. Dr. Ir Hendarmawan, MSc, the Dean of the

Faculty of Engineering Geology who has prompted this research, and to colleagues who have provided invaluable assistance for completion this paper and so could be presented in this symposium.

References :

Alzwar, M., Akbar, N., and Bachri, S., 1992. Geologi Lembar Garut dan Pameungpeuk, Jawa Barat (1208-6), Skala 1 : 250.000. Pusat Penelitian dan Pengembangan Geologi, Bandung.

Billing, M.P., 1990. Structure Geology. Prentice Hall of India, Private Ltd, New Delhi.

Chorley, R.J., 1969. Introduction to Physical Hydrology. Printed in Great Britain by Richard Clay (The Chaucer Press), Ltd Bungay Sulffolk SBN 416 68810 I.

Chorley, R.J., 1969. Introduction to Fluvial Processes. Printed in Great Britain by Richard Clay (The Chaucer Press), Ltd Bungay Sulffolk SBN 416 68820 I.

Harding, T. P. 1974. Petroleum traps associated with wrench faults, American Association of Petroleum Geologists (AAPG) Bulletin, vol. 58, no. 7, p. 1290-1304.

Haryanto, I., 2014. Evolusi Tektonik Pulau Jawa Bagian Barat Selama Kurun Waktu Kenozoikum. Disertasi UNPAD tidak dipublikasi.

Katili, J. A. & Sudradjat, A. 1984. Galunggung. The 1982-1983 eruption. Volcanology Survey of Indonesia, Bandung, 102 h.

Martodjojo, S. 1984. Evolusi Cekungan Bogor, Jawa Barat. Fakultas Teknik Geologi Institut Teknologi Bandung.

Ramsay, J.G., 1987. The Techniques of Modern Structural Geology. Vol.2. Fold and Fracture. Academic Press Limited. London.

Silitonga, P.H., dan Kastowo, 1975. Peta Geologi Bersistem Lembar Slok, Skala 1 :250.000. Pusat Penelitian dan Pengembangan Geologi, Bandung.

Figure 5. Delineated first order Catchments on the left, lineaments of first orde catchments in the

middle, and dominance of lineaments directions on the right.

Figure 6. Delineated second order Catchments on the left, lineaments of second order in the

middle, and dominance of lineaments directions of second order on the right .

Figure 7. Delineated third orde Catchments on the left, lineaments of thirdorder in the

middle, and dominance of lineaments directions of third orde on the right.

5.2.

Regional Tectonic Analysis

Bandung Basin is inter-mountane basin because of its location lies between the

volcanoes, a structural formations such as depression, surrounded by a height of Quaternary

volcanoes. Tectonic background that controls the formation of the basin, initiated by

compressional tectonic structures that produce fold thrust belt at the Tertiary sedimentary rocks

are now the position covered by quarternary volcanic materials(Haryanto, 2014). This tectonic

activity peaked in the Late Tertiary (Martodjojo, 1984). As a result of these events, Bandung and

surrounding areas become the top of the Java geantiklin zone. After the compression forces on

the island of Java gradually diminish, as the equilibrium compensation formation of a number of

normal faults or depression occurred. In the geometry of the structural formations named as

antiklinal collapse basin, under the influence of extensional tectonics. In line with the on going

extensional tectonic, volcanic activities also takes place that happens on a large scale, so that by

the time it generated a lot of volcanic material and most of Tertiary sedimentary rocks covered

by these volvanic materials.

In Bandung and the surrounding area, some of the existence of an ancient volcanic

eruption centers form one lane lineaments with the northeast-southwest direction, so that the

inferred its presence controlled by fault structures (Figure 8). Straightness of the structure in

this region, also occurs in the vocanic material. This shows tectonic activity continued until the

End of Pleistocene, even supposedly still active until now.

In general, based on regional geological structure, the Bandung area is surrounded by a

regional fault, which is in the northern part traversed by Cimandiri and Lembang Fault, in the

east by Citanduy Fault and in the south by Jampang Fault (figure 8). Throughout the regional

fault, indirectly affect the geological conditions in Bandung and the surrounding area. From the

analysis of DEM and field trips, the structural lineaments is not only known caused by a fault

structure. Some lineament structures in the study area cut young volcanic rocks (field data figure

9), thus affecting the shape of the topography and drainage patterns. Theoretically joints structure

can reach hundreds of meters, and can affect the landform.

Drainage pattern and catchments direction can be used as guidance existence of fault

structures and joints structures, because both the geological structure is weak zone / destroyed

that easily weathered and eroded by flowing water. In a relatively long time, the crack area as a

forerunner to the formation of river channel. On the basis of this concept, the determination of

local structural lineaments can be done based on interpretation of river catchments pattern or

catchments direction, as depicted in above figure 5,6,and 7 .

Drainage pattern in the area of young volcanic are generaly radier, this indicates the

drainage pattern is not only controlled by the structure of the cracks, but is also influenced by the

geometry of a volvano that is conical shaped.

Figure 8. Lane lineaments that form ancient volcanic eruption centers in Bandung

and the surrounding area (Katili and Sudradjat, 1984, modified).

5.3.

Discussion

First Order catchments

The first order catctments in the figure 5 above has the largest frequency compare with

other river or catchments order and has a range direction. Associated with the pattern of

structural lineaments in Figure 2 (second order), lineaments of first order seems to be part of the

structural lineament direction of north-south, northwest-southeast and northeast-southwest. In

rosette diagram of first order catchments, the dominant direction of the lineaments trending

northwest-southeast. Through the polar diagram known that maxima point were spread, but the

maxima biggest point still distinguishable, which is trending northwest-southeast (NW-SE),

north northeast-south southwest (NNE-SSW), northeast-southwest (NE-SW) and west-east

(WE). By compiling rosette and polar diagrams, it could be inferred that the first order stream

has three different dominant directions as above.

Rock cracks or joints influenced either by the fault structures and the master joint, may be

followed by secondary cracks (smaller size) that its formation can occur simultaneously. On the

basis of dimension (length) first order stream can be ascertained the river was controlled by joint

system.

Second order catchments

Lineaments according to the second order catchment has a smaller frequency, but still

has a direction as diverse as the first order. However, based on the diagram Rosset and the size

of its length which shows the consistency of the direction and the magnitude, then the existence

of second order seems to had been controlled beside by joint structure, had also been influenced

directly by fault structures. In Figure 6, the alignment of the structure have the same direction

relative to the lineaments of the catchments as depicted in the diagram rosette and polar

diagrams.

Third order catchments

Based on rosette and polar diagram, known that the frequency and direction of lineaments

more influenced by the fault structure trending northwest-southeast. Structural lineaments with

these direction were possibly a reactivation of an old fault that developed in Tertiary sedimentary

rocks. Regionally, the pattern of faults that developed in West Java, influenced by the stress

system trending north-south compression. By using the concept of triaxial stress, the main stress

direction can generate patterns of east-west trending structure with a type of thrust fault and a

normal fault, whereas the northwest-southeast direction and a northeast-southwest forming a

horizontal fault. Fault structure with a north-south direction are generally normal fault type.

At the young volcanic rocks (Quaternary), structural lineaments growing in it, can also

occur due to the loading of volvanic material itself, so generally normal faults. In relation with

Figure 6 (second order catchments) and the dimension (length) where the order of the river is

relatively long, it is concluded that the structural lineaments

associated

with third-order stream

is a combination of fault structures, joint master and as a result of loading. Structural lineaments

normal fault.

VI.

Conclusion

The dominant direction of the lineaments of first orde river or catchments trending

northwest-southeast. Through the polar diagram shows that maxima point were spread, but the

maxima biggest point still distinguishable, which is trending northwest-southeast (NW-SE),

north northeast-south southwest (NNE-SSW), northeast-southwest (NE-SW) and west-east

(WE). Then it could be inferred that the first order stream has three different dominant directions

as shown above.

Based on the directions of lineaments which still in line with the first orde catchments

directions and with magnitude or the length increase, so it seems that the existence of second

order catchments has been controlled beside by joint structure, has also been influenced directly

by fault structures.

Using the concept of triaxial stress, the main stress direction can generate patterns of

east-west trending structure with a type of thrust fault and a normal fault, whereas the northeast-west-

northwest-southeast direction and a northeast-southwest forming a horizontal fault. Fault structure with a

north-south direction are generally normal fault type.

Acknowledgements : deeply addressed to Prof. Dr. Ir Hendarmawan, MSc, the Dean of the

Faculty of Engineering Geology who has prompted this research, and to colleagues who have

provided invaluable assistance for completion this paper and so could be presented in this

symposium.

References :

Alzwar, M., Akbar, N., and Bachri, S., 1992. Geologi Lembar Garut dan Pameungpeuk, Jawa

Barat (1208-6), Skala 1 : 250.000. Pusat Penelitian dan Pengembangan Geologi,

Bandung.

Billing, M.P., 1990. Structure Geology. Prentice Hall of India, Private Ltd, New Delhi.

Chorley, R.J., 1969. Introduction to Physical Hydrology. Printed in Great Britain by Richard

Clay (The Chaucer Press), Ltd Bungay Sulffolk SBN 416 68810 I.

Chorley, R.J., 1969. Introduction to Fluvial Processes. Printed in Great Britain by Richard

Clay (The Chaucer Press), Ltd Bungay Sulffolk SBN 416 68820 I.

Harding, T. P. 1974. Petroleum traps associated with wrench faults, American Association of

Petroleum Geologists (AAPG) Bulletin, vol. 58, no. 7, p. 1290-1304.

Haryanto, I., 2014. Evolusi Tektonik Pulau Jawa Bagian Barat Selama Kurun Waktu

Kenozoikum. Disertasi UNPAD tidak dipublikasi.

Katili, J. A. & Sudradjat, A. 1984. Galunggung. The 1982-1983 eruption. Volcanology Survey

of Indonesia, Bandung, 102 h.

Martodjojo, S. 1984. Evolusi Cekungan Bogor, Jawa Barat. Fakultas Teknik Geologi Institut

Teknologi Bandung.

Ramsay, J.G., 1987. The Techniques of Modern Structural Geology. Vol.2. Fold and Fracture.

Academic Press Limited. London.

Silitonga, P.H., dan Kastowo, 1975. Peta Geologi Bersistem Lembar Slok, Skala 1 :250.000.

Pusat Penelitian dan Pengembangan Geologi, Bandung.