Slump structure as an indicator of the sediment transport direction and paleomorfology modeling on the east side of Temas Hill, Bayat, Klaten, Central Java 1] H.D. KUSUMA WIJAYANTI, 1]JULIAN ITANYO. S, 1]JOHAN EDWART L. HUTABARAT 1] Geology Department, STTNAS Yogyakarta, Jln. Babarsari, Caturtunggal, Depok, Sleman, DIY Phone Number: + 62 274 485390 – 486986 Fax: +62 274 487249 Corresponding Author: julianswandi@gmail.com johan.edwart@geologist.com Abstract: Slump is a movement of unlithified mass sediment gravity flow from particular bathymetry into deeper zone of the sea which caused by slope instability or earthquake. The slope instability is caused by rapid mass sediment distribution. Later, it would create a steep body of sediment mass then trigger the landslide. The sliding mechanism is producing some internal deformation such as folding and thrust fault on its anatomy. Slump also might indicate the paleomorfology or paleobasin and the direction of sediment transport. Located on the eastern side of the East Jiwo Hill – Bayat, Central Java, Temas Hill is an ideal spot for observing the slump and its mechanism. The exact outcrop position is on the east side of Temas Hill and it has never been observed before. Clastic limestone with shallow marine fossil content is dominated the whole research zone. These rocks types are presenting Oyo Formation which builds the Southern Mountain of East Java startigraphy. Three methods are used for revealing the slump. Measuring section method is used to define the stratigraphic unit and its thickness. Structural data for interpreting the transport aim, then the Paleontological analysis to reveal the source of slump material. The output of this research reveals some new information. Stratigraphically, the slump consists of many units and contain lots of Foraminifera - Globigerinid, Paleonumulites, Cycloclypeus sp in mudstone - grainstone which indicate the source of the slump. Local NW – SE normal fault presumably triggering the huge mass of sediment to move and create the slump. Keywords: Slump, Bayat, Oyo Formation INTRODUCTION Temas hill is located far on the eastren part of eastren Jiwo hill. It is facing westren Jiwo hill direcly. Both hills lies on NE – SW with approximately ranging 4 - 5 km in lenght and seperate by Dengkeng river which flow away from NE to SW as seen in topogragphic map in figure 1a. The Jiwo hills elevation are less then 300 mdpl. Administratively the Jiwo hills are located on the eastren side of Bayat town, Klaten regency, Central Java. As the reserach spot the elevation of Temas hill is 156 mdpl and extend on NE – SW. Geographically located on – 7.7673365, 110.6813335 and 6.8 km on width as seen on air landsat photograph in figure Ib. vegetation in Temas hill are grass, Jati tree, bamboo,etc. Local people who live surrounded the lower hill are develop agriculturue, while the others mine the hill for it’s function as the raw material for cement construction. Therefore, the main point of this research is to determine slump direction as well as to interpretate the bathymetry shift cause by the inward slump movement and modeling the paleobasin or paleomorfology. Geological Setting According to Sumosusastro(1959) Temas hill are composed by many sedimentary and fine grain pyroclastic rocks, such as tuff sandstone, tuff marl, foraminifera fossilize limestone and clastic limestone. Sumosusatro was the first reserach who determine Temas hill as deep sea rework material or slump. Nowdays known as marine gravity flow(Boggs, 1988). Based on Southern mountain stratigraphy columm temas hill is a part of Oyo formation which have similiar deposition time with Wonosari formation lies above it(figure 2c). Oyo formation is adjoint laterally with G.pendul diorite Intrusion on the SW and pre tertiery metamorphic of eastren Jiwo hill on NW(figure 2a). Physiographically, Jiwo hil area is classified as Domes and ridges in central depression zone as seen in figure 2b. As a small part of Jiwo hill, Temas hill extend direcly above the pre tertiery metamorphic rock. This metamorphic rock was known as southern mountain basement rock thus derived from either high temperature and pressure. Those metamorphic rock are schist, phylite and marble which spread locally on bayat area. The metamorphic rock are found locally on the west Jiwo hill especially on G. Sari, G. Merak, G. Kebo and the rest of eastren Jiwo hill, include G. Jokotuo and G. Semangu. The metamorphic rock is intruded by Mafic - intermediate igneous rock which had formed G. Pendul on early miocene. This igneous rock are found both in Jiwo hills. Later, The marine volcanic facies build Oyo formation which deposit above the igneous rock intrusion on middle miocene and characterized by clastic limestone, tuff sandstone and tuff marl(Surono 1992). Slump Structure Slump is a movement of unlithified mass sediment gravity flow from particular bathymetry into deeper zone of the sea which caused by slope instability or earthquake (Salahuddin, H 2008). The slope instability is caused by rapid mass sediment distribution. Later, it would create a steep body of sediment mass then trigger the landslide. The movement of slump throught shear force plane. According to Mutti & Ricchi(1975) slump deposit divided into chaotic mixed-grade units and contorteddistrubed beds which have variety in width and could reach tens meter. Slump could reach hundreds of kilometer/m in length. The slump movement commonly produce some complex internal deformation(Lewis 1979). It’s deformation level depend on many factors, such as it’s composition and also the diversity of it’s mass. compressional structure embarcing the lower side of it’s anatomy, thus produce fold or thrust fault(figure 3a ). Lost of slump mobility occure when the shear force of it’s movement reach beyond the critical level. Therefore, The movement stop gradually and irregulary due to it’s composition heterogenity. Slump can be identified by its wavy lamination derived from the early normal layering strata. Thus, slump can be differ from folding by looking it’s undistrubed strata either below or above the layer. The opposite of it, folding tend to shown a complete folding strata or sequences. METHOD In this research there are two types of main methode for collecting the data. Fisrt type is field method. In this method, the authors collect the field data by visiting the observation spot directly, which located on Temas hill, Bayat, Klaten, Central Java. The authors use many geological field tool in order to collect the data’s, such as geological compass for measuring the rock angle(dip) and the slump direction. Chasel point hammer for petrography and paleontology rock sampling. Jacobstaff stick for measuring rocks section and lithology form. Sedimentary rock comparator to detemine the grainsize. Sampel bags for keeping the rock sampel. Stationaries tool and papers. Second types is literature method. In this method the authors search and gather all information related to the observation spot. Those information were gathered from various resources, such as bayat and Surakarta giritontro regional geology maps with 1:25000 scale as well as Jiwo hill topography map. Anohter literature data was compiled from the earlier researcher, such as Salahuddin Husein(2009) and Safrizal(2008). The authors also use academic textbook include: The Principle of The Sedimentology and Startigraphy(Boggs, 1988) also International Sedimentology proceeding (E. Mutti). Measuring Rock Section Measuring section are done in the field in order to determine rock strata thickness base on the outcrop. Measuring section form are needed to write down the infromation about rock charateristic such as megascopic structural features both sedimentary or tectonic structure and the physical description of rock. Jacob staff stick with 1.5 m lenght also have important role for measuring rock thickness on vertical view. Beside those two main method the authors use anohter way to approach the datas. There are three post main method in order to processing them. Petrography Analysis Petrography analysis is used for determining rock characteristic on microscopic view within polarization microscop. Before observed the rock pyhsical propertis, processing the rock sampel are needed and there’s a standart operation procedure for processing the rock sample as shown in figure 4b. Those processes are: 1.) Rock sampel are sliced apart with grinder machine until it’s proper size 2.) Subtilizing the other side of sample 3.) Put the sampel above plate with adhesive liquid 4.) Slice the sample until 1 mm with vacuum adhesive tool 5.) Sampel is subtilizing until 0.003 mm of it’s thickness 6.) Quality checking by Interference color test Thin section determination within polarization microscop are done by using point counting technique. Digital grid are made with 1x1 cm/cubic in order to determine rock composition on percentage scale. Paleontology Analysis Microfossil analysis are conduct for defining plantonic and benthonic formaninfera species. Processing the rock sampel is needed before observing the microfossil. Rock sampel are taken by using channel sampling instead of spot sampling. Standart Operation Procedure are applied in this stage similiar as in Petrography method(figure 5a), such as: 1). Take 100 – 300 gr of dry sediment 2).Subtilize the sample by using hammer 3). Pour H2O2 into the sample for Seperating the cement with the fossil 4). wait 2 – 5 hour 5). Pour the sampel in mesh 40 -60 -100 and wash them with rapid faucet water 6). Dry up the residu left in mesh 60 – 100 in the oven with 60’C 7). Pour the dry sampel in plastic bag and put any proper label on it 8). Sampel is ready to be observed The authors use Plantonic foraminifera analysis to define the age of the rock bulid upon Blow zonation table(1969) as shown in figure 5b. Benthonic formanifera is use as a guide to interpret the depositional envirotment. Every benthonic species indicate particular bathymetry zone. Thus, any benthic species that found needs to be tabilze for defining the bathymetry level. On this analysis require binocular microscop with 20x - 40x zoom in level in order to observed the microfossilas π Streonet Diagram Method In this method the author attempt to focusing on measuring slump anatomy including it’s folding strata. Geological compass is use for determining the slump movement by measuring it’s tilting angle(Dip).. Slump units are measured ten times in order to get more accurate data. Determining the slump movement direction is done by ploting all field data into π streonet diagram(figure 6a). RESULT AND DISSCUSTION According to the measuring rock section in the field there are two groups of lithologies. First group is tuff sandstone and second is carbonate sandstone group(figure 7a) . The author interprets that there are three major slump unit. These three of slump unit is characterized by an eye as the indicator of an slump unit(figure 7b). The first slump units is classified as the carbonate sandstone group with the thickness about twenty meters. The second unit of slump is characterized by the eye of slump opposite with the first slump unit. It thickness reaches twelve meters and classified as the tuff sandstone group. The third unit is less than eight meters in widtht and classified similiar with slump unit two. The author withdrawal age and depositional environment by taking a representative sample of each slump unit. Sample Ap L2 is presenting the second and third slump unit. Planktonic foraminifera as Globigerinoides immaratus(figures 8a) are present. Whereas benthonic foraminifera are found such as Bathysipon fluvia(figure 8a) and Cibicides sp. Am sample L2, L3 Am, Am L4 represents the first slump unit. Am L2 containt Orbulina bilobata and Orbulina universa(figure 8a) and Globigerinoides Immaratus which shows N18 - N19 age. Uvigerina and Nodogerina sp indicate outer neritic. The Am L3 sample containt Hastegerina aequelateris and Globigerinoides ruber which show N19 - N18. The present of Textularia berdumenzi(figure 8a), Amphestegina sp show lagoon – outer neritic environments. Am L4 encountered Sphaeroidinella dehiscen, Globigerinoides bulliodes(figure 8a) also Textularia and lagena sp which indicate neritic outside. Stereonet diagram analysis showed variable slope direction of every slump unit(figure 9a). The first slump unit is present by grey dots which embrace in quadrant II, thus show the avalanche coming from NW – W into SE. The second slump unit is present by red dots accumulated in quadrant IV, shows the avalanche coming from the SE into NW. The dots distribution in the third slump unit are dominantly in quadrant IV, indicates the direction avalanche similiar with the second slump unit. Rock composition is determine only for a few layer of rock that presented every slump unit. Ap – L2 sampel as shown in figure 10a, clearly dominated by vucanic glass groundmass with the micrite as the phenocrist. The composition precentage are Vulcanic glass(37.7%), micrite(28.4), pores or vug(17.78), sanidine(8.4%) based on point counting technique. Am – L2 sampel are dominate by pores(35.3 %) and others minor mineral such as chlorite(24.1%), clay mineral(24%), micrite(20%). Am – L3 sampel are composed by calcite mineral(30.6%), pores(33.3%) as well as lithic(17.3%), clay mineral(18.67%). Am – L4 sampel shows calcite mineral(28%), pores(33.7), clay mineral(26.6%) and quartz( 12.5%). CONCLUSION After several analytical and observation is done, the author trying to combine all method result in order to reveal or at least approach the accurate conclusion based on scientific rules. Therefore, the authors conclude the research in a few points as shown below 1. The phi diagram sterionet analysis reveal the direction of slump units which derived from different direction. 2. The paleomorfology modeling reveal the slumps derived from differen altitude as seen in figure 11a 3. Microfossil analysis reveal the outcrop age beetwen N19 – N20 or late miocene(figure 8a) 4. Both second and the third Slump unit were present in sampel Ap L2 contain cibicides indicate the middle neritic envirotment while the abundance of bathysipon fluvia indicate abyysal zone. This gap interpretate as the bathymetry shifitng from middle neritic into abyysal after slumping occure(figure 11a). 5. The first slump unit presented by sampel Am L2, Am L3, Am L4 derived from inner neritic indicate by Textularia berdumenzi before have rework into deeper bathymetry which indicate by cibicides rugosus(figure) ACKNOWNLEDEMENT The authors would like to say thanks to many people who intensively helped and support this research either material or spirit such as God, Parents. The authors also wants to give a big thanks and appeciation for those who cooperate in this research such H.D Kusuma Wijayanti S.T as the academic mentor, M. Ito Wibowo, Munif Nur Faizan, Laksono sopo Bowo as the field member who volunteering, Mr. Muji as well as Miss Margaret for the opportunity to access the research labs. REFRENCES Hussein, Salahuddin, Novida M (2008) Geometry And Mechanism of SubMarine Slump as an Indicator of Sediment Transport Direction : A Case Study on the Oyo Formation at Temas Hill, Bayat, Klaten, Central Java, Yogyakarta. UGM Boggs, Sam (1988) The Principle of Sedimentology and Stratigraphy. Oregon. Mac-Grow Hill Company. Mutti, E. and F. Ricci Lucchi (1975) Turbidite Facies and Facieds Asscociations. Field Trip Guidebook. The 9th International Sedimentology Congress, Nice, France, A-11, pp. 21-36 Van Bemmelen, R.W. (1949) The Geology of Indonesia , vol. I.A. General Geology. Martinus Nyhoff, The Hague. Verdiansyah, Okky(2016). Buku Panduan Praktikum Petrografi. Sekolah Tinggi Teknologi Nasional, Yogyakarta. Pandita, Hita(2009). Buku Panduan Praktikum Mikropaleontologi. Sekolah Tinggi Teknologi Nasional , Yogyakarta. LIST OF FIGURES I. INTRODUCTION Figure 1a. Bayat topographic map with 1:25000 scale. Small red square indicate the research zone Figure 1b. Temas hill as seen on landsat air photograph Figure 2b. Bayat regional Geological Map. Red square indicate the research zone adjoint with G.pendul diorite intrusion and Jiwo hill pre – tertiery metamorphic rock. Figure 2c. Java Physiography map (van Bemmelen, 1949). Red square indicate Jiwo hill location which classified as Domes and ridges in central depression zone. Figure 2a. Southren Mountain stratigraphy column. Both Oyo and Wonosari formation shown similiar deposition time in middle miocene. Figure 3a. Demonstrate the ideal exampel of the slump body with thier internal deformation structure. The movement of the body through shear plane producing sheath fold. The fold axis is paralell with the direction of slump. In fact, it is difficult to find such ideal slump outcrop in nature. II. METHOD Dips Orientation measurment: 10/ N 290 E 6/ N 360 E 4/ N 315 E 6/ N 305 E 5/ N 300 E 15/ N 360 E 4/ N 320 E 6/ N 311 E 1 N a W E S c b Figure 6a. Steps for ploting dip orientation into π Stereonet Diagram. a). measuring slump dip orientation using geological compass reapetly, b). Stereonet diagram for ploting the datas, c). π Stereonet Diagram with dots embracing S - E area. Figure 4b. Steps for processing petrography sampel before obeserved the rocks under polarize microscop 1 2 3 4 5 6 7 Figure 5a. Tools and materials for processing palentology data. 1). Dosing cup for pouring the sample into the bowl 2). H2O2 (10 – 15%) for seperating the fossil from it’s cement, 3). Mesh 40, 60, 100 for cleaning the sample by pouring faucet water, 4). Cups fill with sample is ready to be heat, 5). Microwave for drying up the sampel, 6). Sampel is keep into small plastic bag and sign with particular number, 7). Microfossil are ready to be observated by Binocular Microscop with 40x zoom in level. III. RESULT AND DISCUSSION Figure 7a. Measuring rock section divided the outcrop into two groups of rock. As seen above, the width of tuff sandstone is 20 m. Carbonate sandstone are lies above it with 13 m in width. Figure 7b. The outcrop view. As seen above, upper boundry is the outcrop picture taken directly on the field. Lower boundery is the manual reconstruction of a slump units which indicate by significant size of eyes . (Skecth by Johan Edwart) PALEONTOLOGY LABORATORIUM REGION / MAP SHEET TRACK GEOLOGICAL ENGINEERING TEMAS HILL TEMAS STREET Fossil species inspected COORDINATE LOCATION S all Fo a i ife a - . PREPARATION SIEVE SHAVINGS SMEAR , SAMPLE NUMBER . DATE / TIME JUNE OTHER , ABUNDANCE BLANK RARELY SEVERAL NO GOOD JULIAN ITANYO & JOHAN EDWART STORAGE JOHAN EDWART ZONE / AGE : GENERAL -N PALEOBATHIMETRY : [LATE MIOCENE - PLIOCENE] BATHYAL ABOVE - BATHYAL MIDDLE PRESERVATION MODERATE AM INSPECTOR CONCLUSION N BAD IDENTITY NUMBER AM - L ZONE OLIGOSEN VERY GOOD SPECIES N N N EARLY MIOCENE N N N N MIDDLE MIOCNE N N N N N N LATE MIOCENE N N N N N PLIOCENE N N N PLEISTOCENE N N O uli a U ive sa O uli a Sutu alis Glo ige i a i a atus Glo o otalia Pseu ode edii Nodosa ia sp. Lage a sp. Bath sipo sp. Uvige i a auspida LAND Figure 8b.The Slump unit 3 tabel. TRANSITION LAGUNA INNER MIDDLE OUTTER ABOVE MIDDLE BOTOM ABBYSAL NERITIC BATHYAL PALEOBATHIMETRY PALEONTOLOGY LABORATORIUM REGION / MAP SHEET TRACK GEOLOGICAL ENGINEERING TEMAS HILL TEMAS STREET Fossil species inspected COORDINATE LOCATION S all Fo a i ife a - . PREPARATION SIEVE SHAVINGS , SAMPLE NUMBER . DATE / TIME SMEAR JUNE OTHER , ABUNDANCE BLANK RARELY SEVERAL NO GOOD JULIAN ITANYO & JOHAN EDWART STORAGE JOHAN EDWART ZONE / AGE : GENERAL -N PALEOBATHIMETRY : [LATE MIOCENE - PLIOCENE] NERITIC INNER - NERITIC OUTER PRESERVATION MODERATE AM INSPECTOR CONCLUSION N BAD IDENTITY NUMBER AM - L ZONE OLIGOSEN VERY GOOD N SPECIES N EARLY MIOCENE N N N N N MIDDLE MIOCNE N N N N N LATE MIOCENE N N N N N N PLIOCENE N N N PLEISTOCENE N N O uli a U ive sa Hestage i a ae uilatela is O uli a ilo ata Glo ige i a Ru e Te tula ia e du ezi Nodosa ia sp. A pest gi a sp. LAND TRANSITION INNER MIDDLE OUTER NERITIC PALEOBATHIMETRY LAGUNA ABOVE MIDDLE BOTTOM ABBYSAL BATHYAL Figure 8b.The Slump unit 2 tabel. PALEONTOLOGY LABORATORIUM REGION / MAP SHEET TRACK GEOLOGICAL ENGINEERING TEMAS HILL TEMAS STREET Fossil species inspected COORDINATE LOCATION S all Fo a i ife a - . PREPARATION SIEVE SHAVINGS SMEAR , SAMPLE NUMBER . DATE / TIME JUNE OTHER , ABUNDANCE BLANK RARELY SEVERAL NO GOOD SPECIES JULIAN ITANYO & JOHAN EDWART STORAGE JOHAN EDWART ZONE / AGE : GENERAL -N PALEOBATHIMETRY : [LATE MIOCENE - PLIOCENE] NERITIC OUTER - BATHYAL ABOVE PRESERVATION MODERATE AM INSPECTOR CONCLUSION N BAD IDENTITY NUMBER AM - L ZONE OLIGOSEN VERY GOOD N N N EARLY MIOCENE N N N N MIDDLE MIOCNE N N N N N N LATE MIOCENE N N N N N PLIOCENE N N N PLEISTOCENE N N O uli a Bilo ata Spe odi ela do s e Glo ige i a ulloides Glo o otalia Bolivi a sp. Bath sipo Fluvia Ci i ides Nodoge i a sp. LAND TRANSITION LAGUNA INNER MIDDLE OUTER NERITIC PALEOBATHIMETRY ABOVE MIDDLE BOTTOM ABBYSAL BATHYAL Figure 8b.The tabel of slump unit 1. The upper red line zone indicate the lifetime interval of the majority plantonic Foraminifera species. While the lower zone indicate the benthic Foraminifera paleoenvirontment POINT COUNTING WORKSHEET MINERAL TOTAL % PORES/VUG 76 35.35% CLAY MINERAL 62 24,19% MICRITE 44 20.47% CHLORITE 25 11.63% VULCANIC GLASS 18 8.37% TOTAL 225 100% Pr/vg Vlc g Pr/vg Clr Figure 10a. Am – L2 composition under polarize microscop. Chlorite(Clr) as secondary mineral is appear which indicate chemical alteration from primary mineral, possibly derived from igneous rock. Thefore, the sampel shows poor sorted grains. POINT COUNTING WORKSHEET MINERAL TOTAL Clc % PORES/VUG 76 33.78% QUARTZ 26 11.56% MICRITE 60 26.67% CALCITE 63 28.00% TOTAL 225 100% Pr/vg Clc Mcr Figure 10b. Am – L4 composition under polarize microscop. There’re space beetwen grains fabric(Pr/vg) and the grains shape is classified as sub-rounded. POINT COUNTING WORKSHEET MINERAL TOTAL % 30.67% CALCITE 69 PORES/VUG 75 33.33% LITHIC 39 17.33% CLAY MINERAL 42 18.67% TOTAL 225 100% Pr/vg Pr/vg Clc Clc Figure 10c. Am – L3 composition under polarize microscop. Calcite mineral(Clc) shows many small hole in it. Pores space indicate by Pr/v which shown dark color and low relief then the others. POINT COUNTING WORKSHEET MINERAL TOTAL Mcr % MICRITE 64 28.44% VULCANIC GLASS 85 37.78% PORES/VUG 40 17.78% MAGNETITE 17 7.56% SANIDINE 19 8.44% TOTAL 225 100% Vlc g Mcr Sne Mcr Vlc g Vlc g Figure 10d. Ap – L2 composition under polarize microscop. Groundmass clearly dominated by vucanic glass(Vlcg). The phenocriyst are micrite(Mcr) which indicate very fine fossil residue. No. Sampel Am – L4 Foramninfera plantonic Globigerinoides bulliodes Foramninfera benthonic Lagena sp Am – L3 Globigerinoides ruber Textularia berdumenzi Am – L2 Obulina universa Uvigerina sp Ap – L2 Globigerinodes Immaratus Bathysipon Fluvia Figure 8a. Foraminifera Plantonic and Benthonic species found in sample. S.U 1 π Sterionet Diagram N W S N W S N W Dips Measurment Data Slump Unit 1 – Dips Orientation 21/ N 125 E 19/ N 119 E 10/ N 149 E 24/ N 135 E 18/ N 113 E 5/ N 115 E E6/ N 140 E 5/N 120 E 4/ N 135 E Slump unit 2 – Dips Orientation 10/ N 290 E 6/ N 360 E 4/ N 315 E 6/ N 305 E 5/ N 300 E 15/ N 360 E E4/ N 320 E 6/ N 311 E 15/ N 295 E Slump unit 3 – Dips Orientation 51/ N 5 E 19/ N 340 E 30/ N 350 E 46/ N 325 E 51/ N 15 E 21/ N 320 E E39/ N 325 E 26/ N 310 E 20/ N 335 E 40/ N 340 E S Figure 9a. π Stereonet Digram. As seen above, dots in diagrams represent dip orientation which collected by measuring slump body with geologcial compass. I.V. CONCLUSION Oyo Formation Pre Tertiery Metamorphic Rock Figure 11a. Paleomorfology reconstruction. As seen above, there’re three slump unit with different downward movement. The first slump unit is moved from NE to SE. This unit derived from middle neritic bathymetry which rework into middle bathytial, indicate by cibicides ruguso. The second and the third slump is derived from SE which moved downward into NW. The bathmetry is shift from inner neritic into abyysal which indicate by bathysipon fluvia.