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This study aimed to investigate the variations of fossil traces in the limestone layers of the Selorejo Formation, as well as the level of rock porosity in the petroleum system. Field mapping, stratigraphic measurements, profiling outcrops, rock sampling, and porosity analysis were conducted to collect data. The results showed that the Selorejo Formation contained various types of fossil traces, such as Planolites, Helminthopsis, Thalassinoides, Conichnus, Chondrites, Macaronichnus, Bergauria, Ophiomorpha, Skolithos, Terebellina Asterosoma, and Palaeophycus. Moreover, rock layers containing trace fossils had lower porosity than those without them. The more trace fossils in the rock layer, the worse the porosity. This finding could be useful in petroleum exploration, as the porosity of rock layers with fossil traces needs to be taken into account when assessing oil and gas reservoir potential. [ABSTRACT FROM AUTHOR]

The Sambipitu Formation at Kali Ngalang, Gedangsari, Gunungkidul in Yogyakarta consists of sandstone at the top layer and carbonate sandstone at the bottom layer. It indicates that this formation was once of a transitional area between land and marine. This diverse lithology is also reflected by the minerals that make up these sedimentary rocks. The diversity of minerals that make up the sedimentary rocks of the Sambipitu Formation cannot be separated from the original rock that formed by tectonic arrangements before, during, and after. The quantitative petrographic analysis is used for naming rocks, determining the tectonic setting sediment maturity, and the source of the materials constituents. Calculating and plotting on ternary diagram of polymic quatrz, sedimentary lithic and volcanic lithic,and feldspar can reveal the make up of sedimantary rocks. Based on field observations and petrographic results, the rocks that make up the Sambipitu Formation are composed of clastic sedimentary rocks (arkosic wacke and lithic wacke) and clastic limestones (grainstone, wackestone, and packestone). The results of analysis about tectonic provenance revealed that research area is in the form of a volcanic island arc with immature sedimentary level. The origin of source material is from orogen arc that indicated as an increasing activity's volcanic around magmatic arc area. [ABSTRACT FROM AUTHOR]

The characteristics of sediment deposits in the fluvial system reflect the sedimentary process. Grain's "figure", mineral composition, and source deposits (provenance) are the parameters which to identify the process. This study aims to determine the controlling factors of river sedimentation by comparing the parameters in the Bogowonto river, Purworejo, Central Java and Progo river, Kulonprogo, Yogyakarta. The methods of this research were provenance and thin section analyses covering all samples collected from upstream to downstream along the rivers. The six samples comprise three samples from the Bogowonto river and three samples from the Progo river representing upstream, middle, and downstream areas. The mineral composition of sand in Bogowonto river are Quartz about 16.67%, Feldspar 20.67%, Mafic minerals 20%, Opaque 36%, and Lithic about 6.67%. While, in the Progo river consist of Quartz 23.33%, Feldspar about 25.67%, Mafic minerals 23.33%, Opaque 17.67%, and Lithic occupy around 10%. Dickinson & Suczek's diagram indicates the sources of the Bogowonto river and the Progo river sediment come from the volcanic arc (dissected arc) that happened during Oligonece to Holocene period due to subduction tectonic setting. The high feldspar and coarse grain size in Progo indicates the young sediment material with a low energy mechanism, while the high opaque mineral in Bogowonto shows the dominant basaltic source and massive weathered host rocks. The high amount of lithic in the Progo river is interpreted as a variative source from rock formations due to long stream erosion [ABSTRACT FROM AUTHOR]

The interesting concern on the Watupuru River Traverse is the outcroping of Nanggulan Formation shale rock of Eocene Age. There are 2 outcrops of source rock which have different of organic composition and potential of hydrocarbons (HC) along of Watupuru traverse. Paleontological analysis results from measurements of 2 profiles of shale outcrops, the age of shale outcrops 1 and 2 along of track Watupuru River of Late Eocene – Middle Oligocene (P17 – P19) evidenced by the fossils of Globigerina ampliapertura, Globigerina praebulloides leroyi, and Pseudohastigerina micra including Nanggulan Formation. This is confirmed with Kulon Progo Regional Stratigraphy by Rahardjo, et al [5]. The methodology research are shale outcrops profile making (shale outcrops-1 and outcrop-2), organic petrological analysis is to determine the characteristics of the maceral constituents of shale. Meanwhile geochemical analysis is from Total Organic Carbon (TOC), vitrinite reflectance and pyrolysis rock-eval. Based on the results of organic petrology and organic geochemical analysis of 5 shale samples of Nanggulan Formation, which are found in two shale outcrops, where shale outcrop-1 the quality of organic material is moderate to very good organic, dominated by the vitrinite maceral group, kerogen type III (HC potential to gas prone), the origin from terrestrial environment, vitrinite reflectance (Ro=0.26-0.32% Vol.) is immature. While shale outcrop-2 the quality of organic material is very good - special, dominated by alginite maceral, kerogen type II (HC potential to oil prone) the origin from freshwater-saline water environment, vitrinite reflectance (Ro=0.25-026 % Vol.) is immature. [ABSTRACT FROM AUTHOR]

Garut Regency, especially Arinem area and its surrounding is generally comprised of igneous rock from the activity of ancient magmatic and young volcano of Papandayan, accountable for potential ore deposit. Arinem Cisewu and its surrounding is an area of alteration and mineralization, such as gold, copper, lead and zinc. There are lithology units resulted from ancient volcanism process in the form of volcanic sediment and intrusion, and other geological processes assisting the formation of ore mineral deposit. Geological structures controlling the ore deposit potential was found in the research area. The location of our research is a part of Mining Permit of Aneka Tambang Mining Company and also several artisanal mining of gold, copper and galena that had been closed down. Previous research showed that the area and its vicinity has Epithermal Low Sulfidation deposit type which generally could be identified in the quartz veins. This research is a continuation of the previous one in order to know the temperature of mineralization and alteration zone, as well as lithology and geological structure in research area. The general method of this research is surface mapping, and the temperature data was obtain by fluid inclusion analysis of the quartz vein samples acquired in the area. There are 4 samples of quartz vein but only 2 are eligible to be analyzed and interpreted to represent the temperature of mineralization in the area. Based on the analysis result, we conclude that the temperature of mineralization in the research area is between 231°C – 420°C. [ABSTRACT FROM AUTHOR]