Detection of peat paleo-environment based on TPI-GI: evidence from South Barito
Jaya, A.P.(1*), Tabri, K.N.(1), Dwitama, P.E.(2), and Irawan, D.E(1).
1) Faculty of Earth Sciences and Technology, Institut Teknologi Bandung
2) Center for Geological Resources Survey of Indonesia
Tissue Preservation Index (TPI) and Gelification Index (GI) can be used to interpret peat paleo-environment. In this paper we will discuss the value of both indexes from South Barito area. We tested 20 samples taken from seven coal seams (A1, A2, A3, B1, B2, B3, and B4), but only 15 of them were used for further analysis. The samples were processed to form polished pellet with thin film of immersion oil on the pellet’s surface. A reflected ray microscope (Carl Zeiss) was used to observe the reflectance using white and blue light. We lively determine the type of maseral group based on Australian standard, 1986. The value of each maseral then fed into Diesel equation to retrieve the TPI and GI value. The resulting values were plotted on Diessel diagram to interpret the paleo environment.
We identify three maseral groups: 1) vitrinite with average value of 93.1 and telovitrinite dominant with average value of 56.3; 2) inertinite with average value 1.7 and telovitrinite dominant with average value of 1.5; and 3) liptinite with average value of 1.6 and cutinite dominant with average value of 0.8. The TPI values are max 1.82, min and average 1.56, and GI values 96.5 max, 28.46 min, and 65.78 average.
From the Diesel Diagram we see that the data fall into telmatic zone with wet forest swamp type, and upper delta plain environment. The values of TPI indicates the coal were built from well-preserved wood plants under continuous oxydation process. GI values supports the oxydation state, along with maseral gelification. High GI values also indicates limited anaerobic decomposition.