Berau Basin is located as a part of Great Tarakan Basin (Figure 1) within Berau Regency Northeast Kalimantan. It has latitude of 1˚12'00"S - 2˚36'00"S and longitude of 116˚00'00"E - 118˚57'00"E with the total area of this basin approximately 150 km² West-East. In northern part, it has bounded by Mesozoic and older rocks of the Sampurna High, to the western part by the strongly folded Mesozoic to Eocene mélange of the Kucing High, and to the southern part by Mangkalihat High separating the Berau Basin and Kutai Basin in the south. This high was associated with the Fault Zone along the north shore of the Mangkalihat Peninsula, and the basin extends toward the Makassar Trough of the Celebes Sea in eastern part.

The Kalimantan island was a relatively stable Sundaland in the Upper Mesozoic times. The tectonics in the northeast Kalimantan area was the result of collision between Indian and Eurasian Plates at 50 Ma [1]. This collision caused the back arc extension connected to subduction rollback in the west Pacific, and the opening of the Berau Basin by Rifting in the Eocene [2], however, thought that collision was less significant.

Regional stratigraphy of Berau Basin was classified into pra-Tertiary, Tertiary, and Quartenary deposits (Figure 2). The oldest age rocks of Tertiary period is Danau Formation, consist of strong tectonics rocks and metamorf with highly significance thickness in the age of Permian-Carbon or Jurassic Cretaceous.

The basin-fill succession of the Berau Basin can be simply divided into 5 major cycles of sedimentation [3], there are cycle 1 (Late Eocene-Oligocene), cycle 2 (Early Miocene-Middle Miocene), cycle 3 (Middle Miocene- Late Miocene), cycle 4 (Pliocene) and cycle 5 (Quartenary). Every cycle reflects different lithological characteristics, which may have been associated to tectonism and relative sea-level changes leading to transgressive and regressive events.

The oldest sedimentary cycle is a syn-rift volcanic bearing siliciclastic-rich unit of the Middle to Upper Eocene which called Sekatak Group consisting of Sembakung Formation and the unconformibly overlying Sujau and Malio Formations. This group were sedimented unconformably overlies pre-rift, Triassic to Cretaceous Sundaland basement rocks, also underlies the post-rift unconformity below the younger group sediments.

The youngest which called Simenggaris Group is divided into five lithostratigraphic units, Meliat/Latih (oldest), Tabul/Domaring, Tarakan/Sajau, and Bunyu (youngest) Formations.

The Sajau coal measures in Tanah Kuning, Mangkupadi in northern part and in the Kasai, Batu-Batu area southern part of the basin typically consist of siliciclastic rocks and coals. The Sajau formation is the one of two coal carrier formations in Berau Basin beside of Latih Formation. This formation consisting claystone, shalestone, sandstone, conglomerates with interlaminated coal, also containing molluscs, quartzit, and mica. The lithological structure which can be found are cross and parallel lamination. The coal thickness in this formation is 0.2 - 1 m, black and brownish layer within 775 m of the total layers. The sedimentation process begin on the fluvial and deltaic system over Pliocene-Pleistocene period which conformably overlying Waru Formation.

In this research, the first parameter were found from HPLC process of two samples (Table 1).

The tables above shows a very low percentage (<10%) of saturated and aromatics fractions which significantly different with NSO and asphaltine percentage that can be found of two samples. In this result, the main characteristics of coal has been proven according to a great abundance of asphaltine (>50%) also high amount of NSO with saturated and aromatics are under 10%.

The two saturated samples has been injected to GC instruments in order to find the chromatograph of each sample. Those chromatograph will showing all the general biomarkers distribution and percentage of UCM (Unresolved Complex Mixture) area. Generally, both samples shows the domination of long chain carbons rather than short chain carbon with large area of UCM which defined as moderately degraded (Figure 3).

The distributions of n-alkana shows that long chain carbon domination begin with medium carbon in nC₂₂ then reach the highest abundance when nC₃₁ with percentage is more than 30% (Table 2).

Based on Moldowan et al., 1992 [5], peak domination of long chain carbon which shows in a larger retention time proves that the maturity of coal samples is remain in immature stage.

Furthermore, the percentage of pristane and phytane is very low in all samples (Figure 4), so it needs larger magnification to identify both pristane and phytane to determine redox conditions during sedimentation.

All the identified pristane and phytane then will be calculate to find the ratio value (Table 3).

In GCMS analysis, saturated fractions have been used for biomarkers identification for depositional environment and maturity assessment of each samples. For saturated, several majors biomarkers have been discovered such as Terpanes from ion m/z 191, Steranes from ion m/z 217, and Bicyclic from ion m/z 123. Those biomarkers appears as peak of MIC (Mass Ionic Carbon) chromatograph which will be calculated in percentage as the paleoenvironmental implications. Beside that, TIC (Total Ionic Carbon) chromatograph could be used to determine the distribution of three majors biomarker above [6] (Figure 5).

Both of samples shows tricyclic diterpane, Tm, Ts, hopanes, moretanes and olenanes, and gammacerane that

spreading along retention time 28 - 42.5 mins within temperature 242.5 - 300 C. But, unfortunately gammacerane could not be identified in ion m/z 191, but it has be shown in chromatograph ion m/z 412. All the identified biomarkers have been calculated as shown below (Table 4).

Several biomarkers from steranes has been discovered from chromatograph ion m/z 217 there are diacholestane, cholestane, cyclic alkane, and methylated sterane. Those biomarkers were dispersed in retention time 12 - 40 mins with temperature 170 - 300 C. But diacholestane and cholestane from all samples can only identified from ion m/z 205 (Table 5).

A number of biomarkers have been found from chromatograph ion m/z 123 including bicyclic, pentamethyldecahydronaphtalene, drimane, and homodrimane. Those compounds were distributed thougr retention time 9 - 43 mins within temperature 150 - 300 C. Those biomarkers also calculating in the table below (Table 6).

In source rock sample, gammacerane usually appear on chromatograph m/z 191 and m/z 412, but in these samples, gammaceran can only find in m/z 412 which further identified as Gammacerane and Norgammacerane with calculation as the table below (Table 7).

Lupane is a unique biomarker that indicates the domination of terrestrial source during sedimentation process and identically found in coal samples. Moreover, lupane is strongy associated with oleananes as an implications of sample which came from terrestrial with high effecting by vegetation sources. Lupane generally found in long chain carbon within retention time 35 - 45 mins in temperature around 290 - 300 C. There are two identified lupane in this ion m/z 177, such as lupane and lup-20(29)-en-3-ol.

In other MIC chrmatograph, there also some association between gammacerane, olenanes, and lupanes which can be found in ion m/z 163, ion m/z 231, ion m/z 259, ion m/z 370, and ion m/z 398.

The coal maturity could be determine from several parameters which have been identified in this research. The first parameter was recognized from extraction data from two samples

Based on extract composition plot, we can examine that the maturity of both samples are still in immature coal stage according to very high abundance of NSO and asphaltine from these samples (Figure 6).

The other parameter that can be used for maturity determination is triterpane from MIC chromatograph ion m/z 191. The result of calculations are plotting in crossplot below (Figure 7).

The diagram above describes the maturity of sample S-003 is slightly different with sample SG-19. Sample S-003 was plotted in immature area with higher terrestrial influence than SG-19, while sample SG-19 was plotted in the edge of early mature area. That diagram support the result of extraction composition plot.

Some parameters have been used to determine the conditions during sedimentation and conditions of depositional environment of each samples. All parameters in this research were interpreted in the form of crossplot diagram (Figure 8).

From the crossplot above, sample S-003 is in the edge of terrestrial source area while SG-19 is in mixed organic input. So, sample S-003 have been dominated by terrestrial source than SG-19 while sedimentation process.

The Figure 9, shows that all the samples are in highly anoxic condition with very low ratio value of Pr/Ph. It is related to the high salinity of environment while sedimentation that shows by highly abundance of gammacerane.

The other parameter which support terrestrial input domination is highly amount of olenanes which can be identified from several chromatograms proves that depositional environment was dominated by terrestrial input especially vegetation source. The other parameters are the great abundance of lupane and cholestane which indicates vegetation input in terrestrial settings. There also cadinanes, that found in MIC chromatograph ion m/z 156 that also implicates terrestrial input especially angiosperm domination rather than gymnosperm.

The absence of diterpenoids in all samples of ion m/z 191 can be an indicator of terrestrial input without or less in gymnosperms domination. The other parameters such as beta-Carotane and Carotenoids has been used to determine the lacustrine settings of deposition, but those parameters were cannot be found in both coal samples.

Based on that diagram (Figure 10), sample S-003 was identified in higher plant source domination while sample SG-19 is in terrestrial setting. So it has been proven that all samples were deposited in terrestrial sources domination.

Based on previous diagram, sample S-003 and SG-19 were plotted in area of highly terrestrial input due to great abundance of oleananes which can be found in most of MIC chromatograms (Figure 11).