ANALYSIS OF STRATIGRAPHY AND SEDIMENTATION DYNAMICS OF COAL, SAWAHLUNTO FORMATION, OMBILIN BASIN

Abstract

The study area located in Air Dingin Village, Sawahlunto city, West Sumatra at coordinates 0°
40' 30" S - 0° 41' 35" S and 100° 46' 15" E - 100° 47' 50" E. The data has been collected in the field by
measuring thickness of layer on outcrops. Lithologies in this study area are dominated by fine to coarse
sandstone and layering of claystone, coal and siltstone. However, on the west are dominated by sandstone
overlay with siltstone layer and sandstone layer on the east of study area. Suspicion occurs on changes of
depositional environment from west to east on study area. Result from cross-sectional analysis of lithology,
outcrops show the characteristic of sedimentary structures form such as massive sandstone, graded bedding,
parallel lamination, cross lamination, wavy lamination, cross bedding, bedding, cross lamination, gradation,
normal gradation and convolute lamination, oxbow lake facies, point bar facies, meander facies, braided river
facies and alluvial fan on mid part. While the results of the analysis of the volume of coal maceral deposited
on wet swamp forest area, limnic facies is indicated by values TPI 0.7%-1.08% and Gi 3.82%-13.28% low TPI
and medium GI. Peatland ecosystems show an Ombrotrophic environment, with prices of GWI 0.00% and VI
0.00% to 015% low GWI and medium VI. The triangle plot shows the telmatic facies of the depositional
environment of wet swamp forest, with an average price of T 93.17%, F 6.83%, D 0.25%, with a high
percentage value of maceral telocollinite.