Paleoenvironment of Tanjung Formation Barito Basin- Central Kalimantan Based on Palynological Data

The research area is located in the Muara Teweh, North Barito, Central Kalimantan. The cocking coal deposits are well known as they were produced from this area.  Upper part of Tanjung Formation is target coal production. The study objectives are to analyze paleoenvironment and to determine the relative age of coal deposits based on palynological data. Preparing palinological analysis used standard procedure by hydrofluoric acid method.Palynomorphs data  grouped into six types of ecology, and the sequence is as follows ; fresh water and lowland (41,75 %), brackish water  swamp (30,10%), Peat and freshwater swamp (17,96%), marine element (7,77 %), back mangrove (1,46%) and upland element (0,97). Palmae pollen is very dominant, especially from freshwater and peat swamp that grow around coastal area i.e. Dicolcopollis, Proxapertites cursus, Proxapertites operculatus, Longapertites and Palmaepollenites kutchensis. Although marine  fossil found, but the frequency  less than one percent,  that was the  evidence of influence sea water to swamp area. The palynomorphs indicate the coal sedimented at upper delta plain.  Fossil index of relative age consist of    Proxapertites cursus, Proxapertites operculatus, Magnastriatites howardi Verrucatosporites usmensis, Retistephanocolpites , and Ixonantes type which refer to Late Eocene.


Int r oduct i on
Tertiary Barito basin spread through Central Kalimantan until South Kalimantan. The northern basin bordered by West Kutai Basin, and in the w est by Schw aner High, to the east by M eratus High, in the south of the Java Sea. The basin covering an area of some 75,000 km2, sediment thickness varies from about 2000 to 5000 met ers. Basin formation started at the Late Cretaceous after the collision microcontinent bet w een Paternoster and SW Borneo microcontinent (Satyana and Idris, 2006). The complete cycle sedimentation of sedimentary rock is found in this basin from Eocene to M iocene by regression and transgression series. Tanjung Formation rocks is an oldest sedimentary rock in this basin w hich w as deposited unconformity above Pre-Tertiary basement rock. Sediment deposition process takes place in an environment fluvio-deltaic, delta front until neritic zone. The Tanjung Formation occurred since Late Paleocene until Late Eocene (Satyana and Silitonga, 1994). Coal w as a sedimentary rock that filled the earliest Tanjung Formation, so that coal is the oldest sedimentary rocks that formed in the Barito basin. Tanjung Formation generates cooking coal that estimated formed in the Late Eocene (Belkin dan Tew alt, 2007;Friederich, et al, 2009;Nas dan Hindartan, 2010). Construction of Tanjung Formation started since Paleocene until Late Eocene (Satyana and Silitonga, 1994). The area spread from Central Kalimantan until South Kalimantan, so very possibly to occupy various environment. Research focus on coal Tanjung Formation of Muara Tew eh, Central Kalimantan. This objective of study to determine t he age and depositional environment condition during the sedimentation of Tanjung Formation w hich w as exposed in the study area.
The Tanjung   The upper part consists of alternating quartz sandstone, silt stone, limestone, and coal. The relative age of Tanjung Formation is Late Eocene, it lays unconformity on the basement M esozoic rocks, a thickness of sediment about 1,300 meters and the depositional environment is the sw am p.
Berai Formation composed of gray and w hite limestone, fine to medium grained, partly recrystallized, contains a large foraminifera and coral, partially layered, it lays conformity on the Tanjung Formation, relative age about M iddle Oligocene to Late Oligocene, deposited in Shallow marine environment, the thickness reach 1.250 meters, it occupies a steep karst hills.
Karam uan Formation composed of consists of gray mudstone, partly calcareous and fossilized; quartz sandstones; gray siltstone; light -gray tuffaceous siltstone, there is fossil insert in the limestone, carbonaceous siltstone, shally siltstone overlie the Tanjung Formation conformably, and estimated interfingering w ith Berai Formation, deposited in shallow marine to outer self. M ontalat Formation characterized by w hite quartz sandstones, cross bedding structures, partly calcareous, deposited overlie the Formasi Tanjung conformably in a marine environment, interfingering w ith Berai Formation, Oligocene, the sediment about 1.400 meters t hick.
Warukin Formation, the character of the sandstone includes beds t hat are medium grained, w ell sorted. Contain carbonaceous mudstone, carbonaceous siltstone. Party conglomeration sandstone, semi-solid, cross and parallel lam inations. This formation overlies the Berai Formation, the depositional environment of the Warukin Formation is coastal at M iddle M iocene, estimated to be 500 meters in thickness.
Alluvial deposit Consist of gravel, pebbles, sand, mud and plant debris.

M at er i al and M et hods
Sample have been prepared by the standar d method using hydrofluoric acid digestion continued by oxidation. The function of each chemical material is; concentrated hydrofluoric acid to remove silica, potassium hydroxide to remove humic acid, hydrogen chloride to remove carbonate, zinc chloride w ith specific gravity 2.2 to separate palynomorphs from others material. Acetolysis is a process to remove cellulose. Before making slides, palynomorphs colored by safranin. Examination of palynomorphs w as using transmission light microscope in different magnification of 100x, 400x, and 1000x.
Based on the environment of palynomorphs origin then grouped based on their environmental, in this case grouped into six i.e: marine, back mangrove, brackish w ater sw am p, freshw at er sw am p, freshw ater and upland element. M arine palynomorphs w hich observed only dinocyst and linning test foram inifera, both of them w ere found in the sam ple. Back mangrove element referred to pollen and spore that produced by vegetation w hich grow s behind mangrove environment. Freshw at er sw am ps elements are pollens and spores that came from around stream s or lake w hich influenced by rain and seasonal flooding so causes w ater levels to fluctuate sw am py condition. Freshw ater element s are pollen, spore, and algae w hich cam e from the freshw ater environment around low land area. The upland element is pollens and spore w hich produced by vegetation cam e from mountain vegetation. Type of vegetation environmen have been publish by Haseldonxk (1974).

4.1.Paleoenvi r nm ent
Acquired 206-grain palynomorphs that comprising 7.84% of the marine environment, w hich consists of Dinoflagellate cyst and linning t est foraminifera. Brackish w ater sw am p 19.61%, consisting of pollen/spore derived from the fact brackish environment is deri ved from mangrove and back mangrove. Peat and Freshw at er sw am p 30.39%, those are pollen and spore w hich produced by plants from peat sw am ps, freshw ater sw am ps, and riparian. Freshw at er and low land 41.18%, consist of pollen w hich produced by low land and fr eshw at er plants. Upland pollen 0.98%, the result of w indtransported pollen (Fig 3).Overall palmae pollen is the highest pollen t hat consisting of Proxapertites cursus, Proxapertites operculatus, Palmapollenites kuthensis, Longapertites and Dicolcopollis. The plants grow in t he coastal areas, especially in t he brackish marshes that posit ion area is behind the mangrove until around the river. This fact supported by Acrostichum aureum spores w ere found at the site as indicator brackish area.The collision of India and Asia plate in the middle Eocene to propagate plants from India to Southeast. Asia region. At that time both the northern region of the Indian plate and the Sunda region experiencing alw ays w et climate, w hich is reflected in the equatorial climat e and common events coal formation in both areas (M orley1998, 2003). Pollens are considered developing in the Sunda Region follow the collision and found at the study area are Palmapollenites kutchaensis, Retistephonocolpites , Magnastritatites grandiosus / Magnastriatites how ardii, Ixonanthes type / Spiniulotriporites spinous, Lakiapollis ovatus.Even marine fossils obtained very few , its presence indicates that the sediment deposition occured in the transitional basin. Dinoflagellate cyst and inner test foram inifera are marine fossils that transported by tidal current through a channel and a connection betw een t he deposition area and the sea. Based on palynomorphs composit ion w hich dominated by pollen and spore from sw am p environment that refers to the delta environment, particularly delta plain.  Palmapollenites khutcensis existed since Eocene until Oligocene, and Retistephanocolpites w iliamsi appeared in the M iddle Eocene and disappeared in the Late Oligocene. Based on those taxa the establishment process of coal in the study area during Late Eocene (Fig 4).

Conclusi ons
The result s show ed that the Tanjung coal formation in the Barito Basin w as formed at Late-Eocene. This is different from previous research that said Tanjung Formation in the M uara Tew eh the age relative w as early Eocene. The dominance of pollen w hich derived from sw am p habitat indicates that the process of coal sedimentation occurred in the sw am p environment w ith marine influence.