Ketebalan dan jenis sedimen dasar laut di suatu lokasi penelitian dapat diketahui dari pengambilan data geologi permukaan dan bawah permukaan dasar laut. Metoda yang digunakan untuk mendapatkan data tersebut di atas antara lain geofisika laut (batimetri, seismik refleksi), geologi (pengambilan contoh sedimen dasar laut). Kegiatan penelitian ini berada di perairan Selat Makassar, di muara sungai sekitar pantai Takalar sebagai sumber sedimen pasir ke arah lepas pantai. Sumber sedimen pasir tersebut diketahui dari hasil pengamatan di lapangan ternyata dipengaruhi oleh energi gelombang, arus sejajar pantai (longshore current) dan arus pasang surut (tidal current). Data geologi bawah permukaan (sub bottom profiling) didapat dengan menganalisa rekaman seismik pantul dangkal untuk mengetahui ketebalan dan luasan sebaran sedimen pasir. Dari analisis data tersebut dilakukan pendekatan perhitungan secara kualitatif sehingga diketahui deposit endapan pasir dengan luas area kurang lebih 9,764 km², dengan asumsi ketebalan rata-rata 3,84 meter maka deposit kurang lebih 224 juta meter³.

Delta Topang, located in Topang Island, Riau Province is known to have the potential of biogenic gas. This research was conducted to identify the Quaternary sediment and the existence of biogenic gas reservoar. In this research has been conducted 75 points of surface geoelectrical measurements (38 points in Parit Jawa and 37 points in Parit Bintang) and 2 points of core drilling (BH-1 in Parit Jawa and BH-2 in Parit Bintang). Total Organic Carbon was also carried out on 10 samples (5 samples from each drilling core). Based on resistivity value of geoelectrical measurements from all points, in general are determined 2 sediment types, very fine sediment (silt and clay) and fine sand. We discussed in detail only point 11 representing Parit Jawa region and point 39 representing Parit Bintang Village. Both in point 11 and point 39, very fine sediment was identified from the surface down to 59 m and 58.5 m respectively, mostly dominated by hydrous clay. Below these, very fine sediment is identified as fine sand. Core drilling BH-1 and BH-2 (40 m length each) composed of thick layer of hydrous clay from the core surface down to bottom part, intercalated with thin layers of silt and fine sand. We considered fine sand found at depths between 24 to > 90 m (from all geoelectrical measurement points) as the closure of biogenic gas. At Parit Jawa biogenic gas closures are found at 2 locations, which are in south west and north east measurement area. At Parit Bintang biogenic gas closures are found at 3 location which are one in south and two in north measurement area. Total organic carbon analyzed from BH-1 indicate the highest percentage at 26-27 m depth with percentage 71.6%. From BH-2 the highest value is indicated at 33-34 m depth with percentage 78.0%. From all this information it is known that the formation of biogenic gas from the abundance of TOC is in the layers of hydrous clay and clay where is in an anaerobic sulfate-reduction environment.

Gas biogenik dikenal sebagai gas rawa atau gas dangkal yang terbentuk dari bakteri metanogenik pada lingkungan anaerobik, khususnya pada daerah-daerah yang tingkat sedimentasinya sangat tinggi.Tujuan penelitian untuk mengetahui secara lebih rinci akan keberadaan gas tersebut di Delta Mahakam. Sungai tersebut merupakan sungai terbesar dan terpanjang di wilayah Kalimantan Timur dan mempunyai tingkat sedimentasi sangat tinggi. Daerah tersebut sangat cocok untuk penelitian indikasi gas biogenik. Hasil penelitian ditandai dengan terdapatnya kantong gas pada rekaman strata box, yang berada pada kedalaman lebih dari 10 (sepuluh) meter. Berdasarkan analisis laboratorium terhadap sampel gas yang diambil di bekas lubang bor adalah gas metan.Kata kunci: rekaman strata box, gas metan, Delta MahakamBiogenic gas known as swamp gas or shallow gas formed by methanogenic bacteria in anaerobic environments, especially in areas that the sedimentation rate is very high. The objective of the research is to find out more detail the occurrence of gas in the Mahakam Delta. The river is the largest and longest river in the East Kalimantan, and it has a very high sedimentation rate.  This area is very good to study the indication of the biogenic gas. The result is signed by gas pocket in the strata box records, whereas at a depth of more than 10 (ten) meters. Based on the laboratory analysis of the samples taken from the former gas borehole is a methane gas.Keywords: strata box records, methane gas, Mahakam Delta.

ABSTRAKKondisi morfologi dasar laut dari suatu perairan khususnya di selat dapat mempengaruhi kecepatan arus laut. Indonesia sebagai negara kepulauan memiliki banyak pulau dan selat. Bertambahnya kecepatan arus laut dapat dimanfaatkan sebagai salah satu sumber energi yang ramah lingkungan. Selat Lampa yang berada di Pulau Natuna merupakan salah satu wilayah dari pulau-pulau kecil di Provinsi Kepulauan Riau yang masih mengalami krisis energi listrik. Hasil pengukuran kedalaman laut di lokasi penelitian secara keseluruhan berkisar antara 0 meter dan 59,59 meter. Dari hasil penelitian diketahui bentuk morfologi bawah laut pada lokasi ini pada umumnya relatif landai dengan kemiringan sekitar 5 o -10 o . Namun pada bagian selat antara Pulau Setanau dan Pulau Setahi memiliki morfologi yang agak curam yang ditunjukkan oleh kontur yang lebih rapat dengan kedalaman berkisar 5 meter sampai dengan 30 meter. Hasil pengukuran dan pemodelan kecepatan arus laut menunjukkan bahwa pada lokasi selat antara Pulau Setanau dan Pulau Setahi memiliki kecepatan arus laut berkisar antara 0,3 meter/detik sampai dengan 1,28 meter/ detik. Sehingga lokasi ini sesuai untuk penempatan turbin pembangkit listrik tenaga arus laut. Kata Kunci : Morfologi dasar laut, Kecepatan arus laut, Energi arus laut, Pulau-pulau kecil terluar, Selat Lampa, Pulau Natuna, Kepulauan Riau, Potensi energi listrik tenaga arus laut ABSTRACTThe morphology condition of the seabed, especially in the strait, can affect the velocity of ocean currents in these waters. Indonesia as an archipelagic country has many islands and straits. Increasing the speed of ocean currents will be very potential to be utilized as one source of alternative energy that is environmentally friendly. Lampa Strait located on the island of Natuna is one of the small islands in Riau Islands Province which is still experiencing energy crisis. This location was chosen as the location of research for the potential energy of Tidal current. The results of sea depth measurements at the study sites overall ranged between 0 meters and 59.59 meters. From the results of the research is known the underwater morphology at this location is generally relatively sloping with a slope of about 5 o to 10 o But in the strait between the island of Setanau and Setahi Island has a rather steep morphology shown by a more dense contour with a depth ranging from 5 meters to with 30 meters. The result of ocean current measurement and modeling shows that at the location of the strait between Setanau Island and Setahi Island has a stronger ocean current speed ranging from 0,3 meters / second to 1,28 meters / second. So this location is suitable for the placement of turbines of Tidal current power plants.