Sandstone Paleogeography And Sedimentation Dynamics Of Ujoh Bilang-Batubelah Limestone Member, Upstream Mahakam River, Ujoh Bilang Area, East Kalimantan Province | Novian | Journal of Applied Geology 7201 12586 1 PB

PALEOGEOGRAPHY AND SEDIMENTATION DYNAMICS OF UJOH BILANG-BATUBELAH LIMESTONE MEMBER were done on the Southwestern tip of Ujoh Bi- lang syncline. Section 2 and 3 are younger than section 1 and there is a lag between measure- ments in section 2 until 3 to section 1. Sections 2 and 3 have the same relative age. Section 4 is younger than section 1 but younger than sec- tion 2–3. Stratigraphic measurement of section 4 was conducted in Batubelah cliff. Several rock samples were taken for analysis. Three rock samples were taken to be analyzed with sieve method in order to see small foraminifera con- tent, six samples were made into thin sections in order to view the content of minerals and fos- sils, especially foraminifera, and one rock sam- ple was analyzed by smear slide method in or- der to view nannoplankton content. 3 Facies The stratigraphic record resulting from field measurements combined with laboratory anal- ysis can be divided into 12 facies Figure 2. De- scription of each facies are given as follows: Claystone facies A. Claystone facies has dark grey color with iron concretions which often form their own concretion layers Figure 3a. Thickness of this facies is around 4–15 m with bed thicknesses vary from 30 cm up to 300 cm and contain few foraminifera fossil. This facies is interpreted to be deposited in lagoonal area. Interbedded fine sandstone and claystone fa- cies B. Interbedded fine sandstone and clay- stone facies has nearly similar thickness; about 10 cm. Sandstone has brown to reddish brown color. Sedimentary structures which developed are parallel lamination, ripple, load cast and oc- casionally trace fossil ophiomorpha Figure 3b, fine grained, grains supported, composed dom- inant by quartz and feldspar. Claystone has dark grey in color. This facies is interpreted was deposited in tidal area, especially in sub tidal- offshore. Interbedded medium sandstone and clay- stone facies C. Interbedded medium sand- stone and claystone facies has nearly similar characteristics with the previous facies facies B. The differences lie in grain size which com- poses the sandstone that is medium sand. This facies is interpreted was deposited in tidal area, especially in intra-tidal – sub tidal. Sandstone facies

D. Sandstone

facies consists of yellowish white sandstone with laminated-bedded, ripple and occasionally Ophiomorpha trace fossil. The grain size ranges from fine to medium sand, grain-supported, rounded, and composed dominantly by quartz and feldspar. Thickness of this facies is about 6 – 11 m with bed thickness range from 10 – 20 cm. This facies is interpreted to be deposited in shallow marine environment, especially in shore face in fair weather wave zone. Claystone with fine sandstone intercalation facies E. Claystone with fine sandstone in- tercalation facies is 19 m thick with bed thick- ness ranging from 30 cm to 150 cm. Clay- stone is dark grey without Foraminifera con- tent. Sandstone is brown in color with bed- ded sedimentary structure, fine sand grain size, grain-supported, rounded, and composed by quartz and feldspar. Thickness of sandstone varies from 10 cm to 30 cm. This facies is in- terpreted to be deposited in transition zone be- tween shore face-offshore, that is, between fair- storm weather wave base zone. Claystone with large foraminifera facies F. Claystone with large foraminifera fa- cies is grey in color Figure 3c, massive in the lower part. In the upper part it has thin bed that curves downward and composed by large foraminifera with good grain orienta- tion. Towards the top, foraminifera content increases with more random orientation. Large foraminifera are dominated by lenticular form. This facies is interpreted to be deposited in a shallowing upward offshore area. Muddy allochem limestone facies G. Muddy allochem limestone facies has light grey color, consists of large foraminifera that mixes with algae in the lower part, and toward the top gradually changes into large foraminifera with c 2012 Department of Geological Engineering, Gadjah Mada University 101 N O V IA N a n d W IJ A Y A N T I Figure 2: Facies in study area. Coarsening and shallowing up ward pattern are recognize from vertical succession. 1 2 c 2 1 2 D ep a rt m en t o f G eo lo g ic a l E n g in ee ri n g , G a d ja h M a d a U n iv er si ty PALEOGEOGRAPHY AND SEDIMENTATION DYNAMICS OF UJOH BILANG-BATUBELAH LIMESTONE MEMBER Figure 3: Several outcrop of facies in study area: a Facies A: Black clay; b Facies B: Interbedded fine sandstone with claystone; c Facies F: Claystone with large foramiinfera; d Facies H: Foraminiferal