A sedimentological, biostratigraphic, and petrographical investigation was conducted on exposed sedimentary rocks in the Seulimeum Formation in the Northwest Aceh Basin, Sumatra. Sedimentary facies analysis suggests a deep-marine depositional environment consists of an inner fan, middle fan, and outer fan to basin plain deposits. New foraminiferal data designated a late Miocene to early Pleistocene age for the studied rock unit, equivalent to N17 to N21 zone, with paleobathymetry in the bathyal environment. Petrographically, the sandstone of the Seulimeum Formation is included as subarkose, sublithic arenite, and lithic arenite, or classified as litho-quartzose, feldspatho-litho-quartzose, and litho-feldspatho-quartzose. Provenance analysis suggests that the origin of the sandstones is from the arc orogen sources. Furthermore, it is concluded that the development of the GSF zone in the late Neogene controls the formation of the deep-marine depositional setting. The west-south-west part of the fault is the footwall part (the Barisan Mountains), as the main high area of sedimentary source material consisting dominantly of the Woyla Group, with some contributions from Bentaro volcanic and Paleogene to early Neogene sediments. Our findings also suggest that the beginning of the Great Sumatran Fault, which corresponds with the uplift of the Barisan Mountains in the northern part of Sumatra, took place in the late Miocene, between 8.6 and 5.9 Ma.

DOI: 10.17014/ijog.6.1.73-101Epiclastic sediments at Kulon Progo, Wonosari, and Punung areas were deposited in marine and terrestrial environments. The aim of this study is to reconstruct biostratigraphy, depositional environments, and sequence stratigraphy of several sections of these epiclastic sediments. Combined foraminiferal and palynological analysis needs to be done to better understand the age correlation of epiclastic sediments of those three studied areas. Epiclastic sediments at Wonosari area (Sambipitu Formation) were deposited at N7-N8 zones, late Early Miocene, while at Kulon Progo area (lower part of Jonggrangan Formation) and Punung area (Jaten, Wuni, and Nampol Formations) were deposited at Middle Miocene. Sediments of the lower part of Jonggrangan Formation were deposited in various environments: mangrove and inner to middle shelf. Depositional environments at the lower part of Sambipitu Formation at Kali Ngalang section are peat swamp and mangrove environments which are more landward compared to the upper part of sediments of Sambipitu Formation which were deposited in marine environments: inner shelf, middle shelf, and outer shelf. At Punung area, the depositional environments are riparian forest, alluvial swamp, backmangrove, mangrove, and inner shelf. MFS-A and MFS-B at Wonosari area found in N8 zone, late Early Miocene, were made as a regional datum correlation for this area, because they are the good age control as they show low diachronous. MFS-1 and MFS-2 at Kulon Progo and Punung areas are found in Florschuetzia meridionalis zone, Middle Miocene.

This study reports on the recent sedimentological and palynological analysis of the rock unit outcropping at the road between Timika and Tembagapura from KM 73 to KM 92, Papua, Indonesia. The unit has been previously regarded as being late Proterozoic to Permian in age. Sedimentary facies analysis suggests a non-channelised deep-lacustrine slump and debris-flow dominated environment consists of delta front, slump, debrite, turbidite and lacustrine mud deposits. New palynological data designated a late Miocene to Pliocene age for the analysed samples, based on the occurrence of Nothofagus brassii type pollen, Stenochlaena milnei type spores (Stenochlaenidites papuanus), Dacrycarpus pollen (Dacrycarpites australiensis) without Proteaceae pollen (Proteacidites spp.). The palynomorph assemblage is interpreted to consist of two main groups: autochthonous and allochthonous components. The autochthonous component is dominated by freshwater algae with the co-occurrence of diatoms, freshwater sponge spicules, Pseudoschizaea, testate amoebae and aquatic plants. The allochthonous pollen component is derived from five major vegetation types: lowland rain forest, lower montane forest, upper montane forest, swamp forest and scrub/grassland. The palynomorph assemblages support the notion of a fluvial–lacustrine depositional environment in an inland position away from marine influences. Furthermore, the studied rock unit is considered to be deposited in the piggyback basin between Papuan Fold and Thrust Belt during the Central Range orogeny.

DOI:10.17014/ijog.6.2.185-208Cretaceous sediments are among the important petroleum system elements for hydrocarbon exploration in Tanimbar area. However, little is known about their facies associations and depositional environments. Facies association analyses have been carried out in fourteen surface sections. Early Cretaceous Arumit Formation comprises three facies associations: subtidal, intertidal, and supratidal deposits. A progradational open-coast tidal flat depositional environment suggests the deposition of sediments of the Arumit Formation. The presence of tidal rhythmites, mud drapes, and fluid mud in those sediments are diagnostic features of a tide domination process in deposition of this unit. Early to Late Cretaceous Ungar Formation in the studied area consists of four facies associations: intertidal, marine offshore to lower shoreface, upper shoreface, and foreshore deposits. An open-coast wave dominated depositional environment is proposed for deposition of sediments of the Ungar Formation. Wave dominated environments in the coarsening upward interval is represented by hummocky cross stratification, cross-bedded sand and gravel, planar parallel stratification, and low-angle stratified beds.

The offshore area in the northeast of Kendari city, the southeast arm of Sulawesi, is an area with favourable hydrocarbon prospectivity shown by numerous oil and gas seeps in the surrounding coastal area. It is a frontier basin in eastern Indonesia, known as the Manui Basin. An exploration well named Abuki-1 was drilled in 1990 suggested a Miocene transgressive sequence as a potential reservoir and source rock at this basin. However, this unit has no analogous exposure in the onshore area resulting in the lack of study and knowledge of this potential Miocene unit. Therefore, we revisit the sedimentary rocks exposure nearby Abuki-1 well in the Toronipa peninsula to study about its sedimentary facies and palynological contents. These outcrops by previous researchers were included in Toronipa Member of Meluhu Formation, and a Triassic age was suggested for this unit. By contrast, our result shows that these exposures are Middle to Late Miocene in age as indicated by the occurrence of the Florschuetzia group pollens (Florschuetzia trilobata, F. levipoli, and F. meridionalis). The absence of Plio-Pleistocene pollen and spores index fossils (Stenochlaena milnei group, Dacrycarpus imbricatus, and Phyllocladus) supports the Middle to Late Miocene age interpretation. A wave-dominated estuary depositional model is proposed based on the presence of river-dominated, mixed-energy, and wave-dominated facies associations. We suggest that the studied sediments are the outcrop analogues for the Middle to Late Miocene transgressive sequence found in Abuki-1 well. Furthermore, we recommend that these Miocene estuary-fill complexes should have excellent hydrocarbon potential. The reservoir potential is the sand deposits of the fluvial, tidal, washover, and shoreface facies with moderately to well-sorted characteristics. The source rocks candidate is the mud of lagoon, tidal flat, floodplain, and marine offshore facies. Moreover, the Manui Basin, with its Miocene estuarine deposits, requires further study to reveal its hydrocarbon accumulation potential.