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THE CHARACTERISTIC OF RECENT SEDIMENT IN SEGARA ANAKAN LAGOON, CIAMIS REGENCY, WEST JAVA
Get PDFThe high intensity of erosions at the rivers upstream which are rivermouthed into the Segara Anakan Lagoon, as sources of the materials which are causing the sedimentation on the lagoon systematically. Based on smear slide analyses and major element contents, source of the sediment which is deposited in the lagoon floor, was predicted as the volcanic products. This condition is supported by the existence of non biogenic materials such as quartz, mica, ferro-oxides, manganese oxides and tuff in the lagoon. Beside that, the existence of major elements such as SiO2 (36,6 – 51,4%) Al2O3 (13,38 – 24,70%), and Fe2O3 (8,69 – 30,6%), is particular element indicators of volcanic products. The lithology in the survey area are volcanic products such as Jampang Formation and Panutuan Formation. Jampang Formation consist of volcano breccia, tuff intercalated with lava and sandstone, claystone, napal intercalated with conglomerate. Panutuan Formation consist of sandstone, napal and tuff, Formation Members of Tuff Napalan, Panutuan Formation, which are spread on the basinal area of Citanduy, Cibeureum, and Ciseel rivers which are rivermouthed into Segara Anakan Lagoon.
Key words : smear slide, major element, Segara Anakan.
Intensitas erosi yang tinggi di daerah hulu sungai-sungai yang bermuara di Segara Anakan sebagai sumber material yang mengakibatkan sedimetnasi laguna secara sistematis. Sumber pasokan sedimen yang diendapkan di dasar laguna berdasarkan analisis sayatan oles, dan unsur utama mineral diperkirakan merupakan produk vulkanik yang bersifat basa. Hal ini didukung oleh terdapatnya mineral non biogenik seperti mineral kuarsa, mika, oksida besi, oksida mangan yang dijumpai tersebar secara merata, adalah produk vulkanik, berupa tuff. Disamping itu keterdapatan unsur utama mineral seperti SiO2 dengan kisaran 36,6 – 51,4%, kemudian Al2O3 dengan kisaran 13,38 – 24,70% sedangkan Fe2O3 dengan kisaran 8,69 – 30,6%, merupakan mineral khas hasil produk vulkanik yang bersifat basa. Litologi daerah penelitian merupakan produk gunungapi, seperti Formasi Jampang yang tersusun oleh breksi gunungapi tuff dengan sisipan lava, berselingan dengan batupasir, batulempung napal dengan sisipan konglomerat. Formasi Panutuan yang tersusun batupasir, napal dan tuff, Anggota Tuff Napalan formasi Panutuan, dan berada di daerah rendahan sungai Citanduy, Cibeureum, Ciseel beserta anak anak sungainya yang bermuara di Segara Anakan.
Kata kunci : sayatan oles, unsur utama, Segara Anaka
RECONSTRUCTION OF SEAWATER d18O SIGNAL FROM CORAL d18O: A RECORD FROM BALI CORAL, INDONESIA
Get PDFSea surface salinity (SSS) and precipitation are important climate (paleoclimate) parameters. To obtain long time series data of SSS/precipitation one use coral proxy. In this study, seawater d18O is extracted from d18O content in Bali coral using centering method. The result shows more convincing that d18Obali is influenced by both seawater d18O and sea surface temperature (SST). In the interannual/decadal scale the variation d18Obali clearly shows the variation of seawater d18O, it is supposed that highly variation of precipitation contribute to the seawater d18O variation which mirrored by coral d18Obali.
Keywords: coral d18O, seawater d18O, precipitation, sea surface salinity, sea surface temperature
Salinitas permukaan laut (SSS) dan curah hujan merupakan parameter penting untuk studi iklim maupun paleoiklim (iklim masa lampau). Untuk mendapatkan data dalam urut-urutan waktu (timeseries) yang panjang dari SSS dan curah hujan diperlukan data proksi geokimia dalam koral. Dalam studi ini kandungan d18O dalam air laut dapat di rekonstruksi dari kandungan d18O dalam koral dengan menggunakan metode centering. Hasilnya menunjukkan bahwa d18O dalam koral dipengaruhi oleh kandungan d18O dalam air laut dan SST. Dalam resolusi tahunan dan puluhan tahunan variasi d18Obali dalam koral menunjukkan dengan jelas variasi d18O dalam air laut, hal ini diduga bahwa dalam resolusi tahunan dan puluhan tahunan variasi curah hujan sangat tinggi yang berkontribusi pada tingginya variasi d18Obali dalam air laut sehingga dapat terekam oleh koral.
Kata kunci: d18O koral, d18O air laut, curah hujan, salinitas permukaan laut, suhu permukaan laut
SEDIMENTOLOGICAL PROPERTIES OF THE 2010 MENTAWAI TSUNAMI DEPOSIT
Get PDFPost tsunami survey of the October 25, 2010, Mentawai tsunami, has been carried out by a collaboration team of Indonesian-German scientists from 20 to 28 November 2010. One activity of the researches were investigation on tsunami deposits along the coast following the event that devastated the islands of Sipora, North Pagai and South Pagai. Sedimentological properties of Mentawai tsunami deposit were explained by this study, from both megascopic and laboratory result. In general, beaches along the study area are underlying by a stretch of reef limestone, sediments mostly composed of white sand while grey sand was found only at Malakopa. Tsunami sediments were taken from 20 locations, start from Betumonga at Sipora Island until Sibaru-baru Island at the southern tip of the study area. The thickness of tsunami deposits are ranged between 1.5 and 22 cm, which are generally composed of fine to coarse sand in irregular boundaries with the underlying soil. Based on grain size analysis, variation of sedimentological properties of tsunami deposits range between phi=-0,5793 and phi=3,3180 or very coarse to very fine sand. Tsunami deposits mostly have multiple layers which described their transport processes, run up at the bottom and back wash at the top. Structural sediments such as graded bedding of fining upward, parallel lamination and soil clast were found. The grain size distribution curves show two types of mode peak, unimodal and multimodal which are indication of different sorting condition representing the source materials. While segment grain size accumulative plot generally shows domination of dilatation and traction transport mechanism rather than suspension. In general, very rare fossils were found from Mentawai tsunami deposit, but those findings gave information on how depth tsunami start to scour the seafloor and transport it landward, such as an abundance of Sponge spicule was found which indicate shallow water environments (20-100 m seafloor depth).
Keywords: 2010 Mentawai tsunami, tsunami deposit, grain size analysis, fossils identification.
Survei pasca-tsunami Mentawai 25 Oktober 2010, telah dilakukan oleh Tim gabungan Indonesia-Jerman pada tanggal 20 - 28 November 2010. Salah satunya adalah melakukan identifikasi endapan tsunami yang ditemukan di sepanjang pantai yang terlanda tsunami di Pulau Sipora, Pagai Utara dan Pagai Selatan. Berdasarkan hasil penelitian baik megaskopik maupun analisis laboratorium, dalam tulisan ini dapat dijelaskan mengenai sifat-sifat sedimentologi dari endapan tsunami Mentawai. Secara umum litologi penyusun pantai di daerah penelitian disusun oleh hamparan batugamping terumbu, sebagian disusun oleh pasir berwarna putih, sedangkan di Malakopa tersusun oleh endapan pasir pantai berwarna abu-abu. Berdasarkan hasil analisis laboratorium, diperoleh variasi sifat sedimentologi, seperti kisaran ukuran butir endapan tsunami antara -0,5793 phi dan 3,3180 phi, yaitu pasir sangat kasar hingga sangat halus. Endapan tsunami umumnya memiliki beberapa lapis yang menunjukkan adanya proses transportasi, seperti saat air naik (run up) di lapisan bagian bawah dan surut di bagian atas, yang ditunjukkan dengan adanya perbedaan ukuran butir. Struktur sedimen ditemukan seperti adanya perubahan besar butir secara berangsur menghalus ke bagian atas, perlapisan sejajar dan fragmen tanah yang terperangkap dalam sedimen. Kurva distribusi ukuran butir memperlihatkan dua jenis model puncak, yaitu unimodal dan multimodal yang memperlihatkan kondisi pemilahan yang berbeda yang menunjukkan kondisi sumber material endapan tsunami, sedangkan grafik akumulasi ukuran butir umumnya memperlihatkan dominasi mekanisme transportasi dilatasi dan traksi daripada suspensi. Secara umum fosil yang terkandung dalam endapan tsunami Mentawai sangat jarang, namun sedikit banyak telah memberikan informasi seberapa dalam gelombang tsunami mulai menggerus lantai samudera dan memindahkannya ke darat, misalnya dengan ditemukannya fosil bentonik Sponge spicule yang melimpah, menunjukkan asal lingkungan laut dangkal dengan kedalaman laut 20-100 m.
Kata kunci: Tsunami Mentawai 2010, endapan tsunami, analisis besar butir, identifikasi fosil
SEDIMENTATION RATE BASED ON OCEANOGAPHIC PARAMETERS REVIEWS IN THE ESTUARY OF KAPUAS, CENTRAL KALIMANTAN
Get PDFSecara geografis daerah penelitian terletak di muara Sungai Kapuas Kalimantan Tengah. Kawasan pantai ini sangat terbuka dipengaruhi oleh aksi gelombang dari arah tenggara, selatan, baratdaya dan barat. Di pesisir pantai muara Sungai Kapuas terdapat arus sejajar pantai yang bergerak masuk ke arah muara. Pergerakan arus sejajar pantai tersebut memasok sedimen dari arah tenggara dan barat ke muara. Sedimen tersebut cenderung diendapkan di sisi barat dari muara Kapuas. Hal ini menjadi kendala alur pelayaran di muara Sungai Kapuas.
Kata kunci : arus sejajar pantai, muara, Kapuas
Geographically, the study area is located on the coast of Kapuas River mouth, Central Kalimantan. This open beach area is affected by wave action from southeast, south, southwest and west direction. The longshore current drifts to the estuary on the coastal zone of the Kapuas River. It gives potential sediment supply from the southeast to the north. The sediment tends to be deposited in the western part estuary of Kapuas.This particular thing evokes the ship navigation in Kapuas estuary.
Keywords : longshore current, estuary, Kapua
SEAFLOOR SEDIMENT CHARACTERISTICS AND HEAVY MINERAL OCCURENCES AT BETUMPAK CAPE AND ADJACENT AREA, BANGKA STRAIT, BANGKA BELITUNG PROVINCE
Get PDFThirty seafloor of sediment samples have been taken by using gravity corer and grab sampler at Betumpak Cape, and adjacent area of Bangka Belitung. The result of grain size analyses show that there are four sediment units: gravelly sand, gravelly muddy sand, silt and silty sand. Identification of Scanning Electron Microscope (SEM) image on several samples shows the presence of clay mineral such as smectite, alunite, chlorite etc., may resulted from plagioclase weathering of granite. Based on heavy mineral analyses, its highest content is found at MTK-27 (northwest of Betumpak Cape). High content of apatite (0.94% wt and 1.07% wt) is found on coarse sand fractions (115-170 mesh) at MTK-29 (northeast Ular Cape) and MTK-30 (north of Ular Cape). Generally, the heavy mineral accumulation is occurred on medium sand fraction (60-80 mesh) as magnetite (7.86% wt), ilmenite (4.9% wt) and zircon (1.32% wt). Based on these data, it shows that heavy mineral is accumulated on medium to coarse sand.
Keywords: sea floor sediment, grain size analysis, heavy minerals, and Betumpak Cape, Bangka strait.
Sebanyak 30 sampel sedimen dasar laut telah diambil dengan menggunakan pemercontoh jatuh bebas dan comot di Perairan Tanjung Betumpak dan sekitarnya, Bangka Belitung. Hasil analisis besar butir menunjukkan adanya 4 satuan sedimen, yaitu pasir kerikilan, pasir lumpuran sedikit kerikilan, lanau dan pasir lanauan. Hasil identifikasi citra Scanning Electron Microscope (SEM) terhadap beberapa sampel, memperlihatkan kehadiran mineral lempung seperti smektit, alunit, klorit dll., kemungkinan sebagai hasil pelapukan plagioklas dari granit. Berdasarkan analisis mineral berat kandungan tertinggi terdapat di lokasi MTK-27 (baratlaut Tanjung Betumpak). Akumulasi mineral berat umumnya terdapat pada fraksi pasir ukuran sedang (60-80 mesh) berupa magnetit, ilmenit dan zirkon masing-masing dengan kandungan 7,86 % berat. 4,9% berat dan 1,32% berat. Pada fraksi pasir kasar (115-170 mesh) dijumpai kandungan apatit tertinggi di MTK-29 (timurlaut Tanjung Ular) dan MTK-30 (utara Tg. Ular) sebesar 0,94% berat dan 1,07% berat. Dari data tersebut terlihat, bahwa secara umum mineral berat terakumulasi pada pasir sedang hingga pasir kasar.
Kata kunci: Sedimen permukaan dasar laut, analisis besar butir, mineral berat, dan Tanjung Betumpak, Selat Bangka
DIAGENETIC FEATURES OF PALEO LAGOONAL REEF OF TACIPI AREA, SOUTH CELEBES
Get PDFLimestone outcrops of the Tacipi area is an ideal carbonate platform part of Neogene East and West Sengkang Basin that are located in the south part of Sulawesi, precisely in western of Bone city. The limestones of this area, outcropping mainly on the north-south oriented hills such as Temapole, Anadara, Tamping, Lappa, etc., are the best reef example in the Tacipi area, as the reef itself, its debris and detritus can be distinguished in the field. Throughout the ridges and pinnacle in Tacipi field the limestones are predominantly homogenous boundstones on the top and detrital bioclastic packstones with local grainstones, and wackestones at the bottom. There are four major reef zonation indentified pacth reef, barrier reef, fore reef and lagoon. The extensive freshwater leaching of fossil fragments and calcareous cement give the preservation of biomouldic and vug pore spaces. Abstract Limestone outcrops of the Tacipi area is an ideal carbonate platform part of Neogene East and West Sengkang Basin that are located in the south part of Sulawesi, precisely in western of Bone city. The limestones of this area, outcropping mainly on the north-south oriented hills such as Temapole, Anadara, Tamping, Lappa, etc., are the best reef example in the Tacipi area, as the reef itself, its debris and detritus can be distinguished in the field. Throughout the ridges and pinnacle in Tacipi field the limestones are predominantly homogenous boundstones on the top and detrital bioclastic packstones with local grainstones, and wackestones at the bottom. There are four major reef zonation indentified pacth reef, barrier reef, fore reef and lagoon. The extensive freshwater leaching of fossil fragments and calcareous cement give the preservation of biomouldic and vug pore spaces
A COMPARISON OF MAJOR ELEMENTS BETWEEN MARINE SEDIMENTS AND IGNEOUS ROCKS: AS A BASIC DETERMINATION OF THE SEDIMENT SOURCE AT UJUNG PENYUSUK WATERS, NORTH BANGKA,BANGKA BELITUNG PROVINCE
Get PDFThree igneous rock samples from the coast and five sediments from the marine of Ujung Penyusuk Waters have been used for chemistry analysis as the basic determination of sediment source. The result of chemistry analysis shows that the major element with relatively same pattern. In the igneous rock samples, the result of chemistry analysis shows the SiO2 ranges between 72.3 - 76.8%, Al2O3 (9.64 - 11.64%), and Fe2O3 ( 2.08 - 2.18%). In the marine sediment, the content of SiO2 is between 62.2 and 66.5%, Al2O3 (2.93 - 3.63%) and Fe2O3 (21.19 - 24.40%). Other elements such as CaO, MgO, K2O, Na2O and TiO2 are relatively similar values in all samples. The difference of element content in marine sediment and coastal igneous rock occurs in Al2O3 and Fe2O3. The Al2O3 is small in marine sediment while the Fe2O3 is higher compared to igneous rocks. Decreasing of the Al2O3 (kaolinite) in the marine sediment is caused by the character of the Al2O3 that was derived from quartz rich of igneous rocks forming kaolinite. It was than deposited in the sea floor. Increasing of the Fe2O3 in marine sediment is caused by addition reaction of the Fe from the sea. Generally, the content of the SiO2 (quartz) in igneous rock and marine sediment belongs to the same group source that is acid igneous rock. The SiO2 in the sediment belongs to a group of granitoid.
Keywords: major elements, marine sediment, igneous rock, Ujung Penyusuk waters
Tiga contoh batuan dari pantai dan lima contoh sedimen dari dasar laut di perairan Ujung Penyusuk, Bangka Utara telah digunakan untuk analisis kimia sebagai dasar dalam penentuan sumber sedimen. Hasil analisis kimia menunjukkan kandungan unsur utama dengan pola yang relatif sama. Pada contoh batuan beku, hasil analisis kimia memperlihatkan kandungan SiO2 antara 72,3 - 76,8%, Al2O3 (9,64 – 11,64%) dan Fe2O3 (2,08 - 2,18%). Pada sedimen dasar laut memperlihatkan kandungan SiO2 antara 62,2 – 66,5%, Al2O3 (2,93 – 3,63%) dan Fe2O3 (21,19 - 24,40%). Unsur lainnya seperti CaO, MgO, K2O, Na2O dan TiO2 yang relatif sama pada seluruh contoh. Perbedaan kandungan pada sedimen dasar laut dan batuan beku di pantai terjadi pada unsur Al2O3 dan Fe2O3. Kandungan Al2O3 pada sedimen dasar laut lebih kecil dan Fe2O3 lebih besar dibandingkan pada batuan beku. Berkurangnya Al2O3 (kaolin) pada sedimen dasar laut disebabkan oleh sifat Al2O3 yang berasal dari rombakan batuan beku yang kaya kuarsa (SiO2) membentuk kaolin. Unsur tersebut kemudian diendapkan di dasar laut. Peningkatan Fe2O3 pada sedimen dasar laut disebabkan oleh penambahan unsur Fe2O3 yang mengikat unsur Fe dari berbagai mineral di laut. Secara umum, kandungan SiO2 (kuarsa) dalam batuan beku dan sedimen dasar laut termasuk dalam kelompok yang relatif sama yaitu batuan beku asam. SiO2 dalam sedimen termasuk kelompok granitoid.
Kata kunci: senyawa utama, sedimen dasar laut, batuan beku, Perairan Ujung Penyusuk