Understanding the evolution of the basin and tectonostratigraphy is the key role to reveal all geological aspects and potential hydrocarbon resources. Northeast Borneo has many hydrocarbon resources especially in Mahakam delta. However, Berau sub-basin remains unclear due to lack of G&G data. This paper presents a new concept of tectonostratigraphy and basin evolution based on subsurface and surface data integrated with thin section as well as radiolaria analysis to determine the age of such basin. Present-day aerogravity data shows that Berau sub-basin has two depocenters trending N-S and E-W and is bordered by Mangkalihat High (MKH) in the south and Rajang Embaluh Group (REG) in the west area. The metamorphic belt in REG area was formed in Early Jurassic (190 Ma), meanwhile in MKH, the ophiolite sequence was formed during Middle-Late Jurassic based on the presence of Holocrptocanium sp. in chert interbedded with mudstone. Based on the analysis, Berau sub-basin experienced subduction to obduction during Early Jurassic to Late Jurassic. In Cretaceous, Berau sub-basin is filled with conglomerate, shale and quartz sandstone of Telen and Benggara Fm. that has provenance from MKH and REG area. In Paleogene, major breakup unconformity can be seen on the seismic section and spread across the basin overlaid by shale with tuff of Eocene-Oligocene Sembakung Fm. The deposition of Sembakung Fm is controlled by extensional regime caused by subduction rollback in NW Borneo. The carbonate sequence has dominated this area in Late Oligocene to Early Miocene. Following the collision of Kuching high in Middle -Late Miocene, the deposition was dominated by deltaic sediment due to regional regression phase. In Plio-Pleistocene period, Berau sub-basin consists of carbonate and deltaic sediment from Domaring and Sajau Fm. In this time structural reactivation and inversion due to transpressional system with SE-NW pattern had controlled Berau sub-basin. Based on the evolution of Berau sub-basin, four hydrocarbon plays are identified in this paper, Mesozoic Play especially in Telen Fm, Paleogene Carbonate Play in Tabbalar & Birang Fm, Middle Miocene Play especially in Latih Fm and Plio-Pleistocene Play in Sajau Fm and Labanan Fm. Working petroleum system in the basin manifested by many oil seeps that can be found in surface and postmortem of several wells data shows commercial to sub-commercial and abundant oil and gas show.

We analyzed the tectonics and stratigraphy of the Southern Great Tarakan Basin to determine its tectonic evolution during the Mesozoic-Cenozoic Eras, the evolution of basin geometry, and the potential of hydrocarbon using integrated surface and subsurface data. Southern Great Tarakan Basin can be divided into three sub-basins, Berau, Muara, and South Tarakan. They comprise deposits of Jurassic to Quaternary age, which can be assigned five mega sequences based on their lithological characteristics and tectonic development. We divide the tectonic events into four main phases; (1) contractional Jurassic-Cretaceous, (2) extensional Paleogene, (3) subsidence Early Neogene, and (4) contractional Late Neogene. The development of the strike-slip activity influenced the geometric evolution of the two sub-basins. NW-SE transpressional structures formed during the contraction phase caused most of the existing structure in Paleogene reactivated and inverted, followed by basement uplift and erosion. Consequently, the evolution of the transpressional system caused The Great Tarakan Basin to be divided into five sub-basins during the Late Miocene-Pliocene. Moreover, five horizons with hydrocarbon potential exist in the southern part of The Greater Tarakan Basin; three plays in the Berau Sub-basin, and two main plays in the Muara Sub-basin. The Late Neogene structures in the Berau Sub-basin control the accumulation, migration, and trapping mechanism, whereas these structures do not exist in Muara; hence, this sub-basin is dominated by stratigraphic traps.

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The geomorphological understanding of earth dynamics, including the relationship between landforms and their processes, was one of the earliest and most specific contributions to disaster prevention. Disaster geomorphology is one of the approaches in disaster studies, which includes aspects of landforms, processes, and results of physical processes that have the potential and can cause disasters. The landform is of risk factors that can turn natural hazards into natural disasters and determines the damage that disasters can cause to human activities. Following the 2006 South Java Tsunami, infrastructural development occurred massively in the 2006 South Java Tsunami inundation areas. Several tsunami risk mitigation efforts were conducted but solely based on the 2006 tsunami scenario and ignored the existence of more considerable tsunami hazards from the Sunda Megathrust. This consideration may lead to an increasing risk of future tsunamis. We evaluate and appraise favorable and unfavorable geomorphological features to reduce the risk of future tsunamis. Pangandaran has a unique landform compared to other areas on the south coast of Java, and this landform has the potential to reduce future tsunami risk. Typical landforms studied include coastal plains, alluvial plains, Tombolo, tied islands, and structural hills. The results show that the morphological features of the Tombolo and the coastal plain area are categorized as high risk when a tsunami occurs. The tied island is categorized as a favorable morphology where these morphological units have the advantage of elevation and efficient distance to the tsunami risk zone. Evacuation facilities are also needed, especially in the coastal plain and Tombolo areas (with a height of >20 meters), to reduce disaster risk, particularly mortality caused by tsunami events.