Sedimentological Characteristics and Geochemical
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ISSN 2319-8885 Volume.08, Jan-Dec-2019, Pages:355-360 www.ijsetr.com Sedimentological Characteristics and Geochemical Classification of Sandstones of Upper Pegu Group in Chauk Township, Magway Region 1 2 MAY THU AYE , KHIN SEIN MYINT 1Dept of Civil Engineering, Technological University, Magway, Myanmar, Email: [email protected]. 2Dept of Biotechnology, Technological University, Yamethin, Myanmar, Email: [email protected]. Abstract: The study area is situated on the eastern bank of ʹ ʺ ʹ ʺ ʹ ʺ ʹ ʺ -13 UTM Map. It is covered by the Oligocene to Pliocene clastic sedimentary rocks. Among them, Pyawbwe and Kyaukkok formations were studied to predict the geochemical characteristics of the study area. To conduct XRF analysis, six sandstone samples were taken from the selected layer of sandstone in the Pyawbwe Formation and six sandstones were taken from the selected sandstone layers in the Kyaukkok Formation. According to the chemical classification of sandstone diagram, the sandstones of Pyawbwe and Kyaukkok f m f ‘L ’. Keywords: River, Rocks, Pyawbwe, Kyaukkok, Sandstones, Litharenite. I. INTRODUCTION II. TOPOGRAPHY The study area, Chauk Oil Field, is situated on the eastern Topographically, the study area can roughly be said as bank of the rolling terrain topography and a range of small hills is running NNW-SSE direction in the eastern part. The highest m f point of the study area located at the northeastern margin is ʹ ʺ ʹ ʺ ʹ ʺ about 180m above sea level. The western part of the area is ʹ ʺ -13 UTM Map (Fig 1). bounded by the Ayeyarwaddy River flowing from NNE to SSW. Low land topography is present in the western and central parts of the area (Fig.2). There are numerous streams in this area and the main streams such as Tama Aik Chaung, Ayesayti Chaung, and Kyaukte Chaung. All streams flowing from the eastern part enter into the Ayeyarwaddy River. The major drainage pattern of the present area shows trellis and parallel pattern. Figure1. Location map of Chauk Area. The present area is approximately 63 square kilometer (24.1 square mile), 9 km (5.6 mile) long in north-south direction, and 7 km (4.3 mile) wide in east-west direction. This area is easily accessible by car throughout the year from Pagan-NaungOo, Kyaukpataung, Yenangyaung and Seikpyu. Figure2. Physicographic map of Chauk Area. Copyright @ 2019 IJSETR. All rights reserved. MAY THU AYE, KHIN SEIN MYINT III. STRATIGRAPHY IV. OKHIMINTAUNG FORMATION The research area is covered by the Oligocene to Pliocene The name of this formation was previously called the clastic sedimentary rocks. The strata can be classified into “O m ’’ L m four major stratigraphic units such as (1) Okhmintaung m f m Formation of lower Pegu Group (2) Pyawbwe Formation, m f m and (3) Kyaukkok Formation of Upper Pegu Group and (4) O m ) NNW of Thayet, Irrawaddy Formation (Fig.3). The late Oligocene strata are Magway Region. The stratigraphic thickness in type section constituted mainly of yellowish - brown colored, medium - is 3000 feet. grained sandstones interbedded with the laminated shale. The Miocene of Upper Pegu Group is yellowish - brown A. Distribution and Thickness colored sandstones and light-gray colored shale and The Okhmintaung Formation generally occupies in the fossiliferous conglomerate band. Late Miocene - Pliocene core of Chauk Anticline, in the SE of Patamyataung and near Irrawaddy Formation is characterized by buff color to the Kyaukte village. The best exposure of this formation is yellowish grey, thick - bedded to massive, unfossiliferous exposed along Kyaukte - Ohnmya road section and east of friable sandstones which are widely exposed in the flank of Chauk. The thickness of Okhmintaung Formation exposed in the major anticline. The stratigraphic succession and the present area is 164 m in the present study (Fig. 4). lithology of the Chauk area are shown in Table (1). B. Lithology The Okhmintaung Formation is composed of medium to thick bedded sandstone intercalated with shale beds and minor thin conglomerate beds. In the study area, yellowish brown colored, fine to medium - grained, medium to thick - bedded sandstone with mud lamination and indurated sand (Fig.5). In the lower part of this formation. In the upper part, the shale becomes more frequent. C. Fauna and Age and Collection This formation is a few amounts of fossils and it contains gastropods fossils and colonary coral. Based on the discovered fossils and previous works on this formation, the age of this unit has been named as the Late Oligocene age. Figure3. Geological Map of Chauk Area (Modified after M.O.G.E, 1980). Table1. Stratigraphic succession of Chauk Area Figure4. Stratigraphic column of Okhmintaung Formation at Kyaukte Chaung section. International Journal of Scientific Engineering and Technology Research Volume.08, Jan-Dec-2019, Pages: 355-360 Sedimentological Characteristics and Geochemical Classification of Sandstones of Upper Pegu Group in Chauk Township, Magway Region A. Distribution and Thickness In the study area, the Pyawbwe Formation exposed both eastern and western flank of Chauk Anticline. According to the asymmetrical nature of the anticline, the exposure of the Pyawbwe Formation in the western flank of major anticline may be wider than that of the eastern flank. In the study area, the best exposure of this formation is exposed near Kyaukte village and along the railway section from Chauk to Tayawgon station. In present study, the thickness of Pyawbwe Formation is about 290 m in Kyaukte section. B. Lithology The Pyawbwe Formation consists mainly of pale brown to bluish grey shale (Fig.6), grey sandy concretionary shale with thin fossiliferous sandstone, occasionally intercalated with indurated sandstone bands and thin conglomerate band. Figure 5. The alternation of light brown, medium bedded In the upper part of this formation, light brown to dark sandstone and grey to bluish grey shale with gypsum brown, fine to medium - grained, medium to thickly - near the west gate of Kyaukte Village bedded, planner and through cross bedding (Fig.7). ). V. PYAWBWE FORMATION C. Fauna and Aga and Collection m f f m f L The marine fossils of corals and brachiopods are collected “ m ’’ from this formation in the study area. The presence of ) in Minbu Township, marine fossils and secondary data, the age of this formation Magway Region. It is typically about 600 meters thick. The may be regarded as Early Miocene. The lithological and Pyawbwe Formation was previously called the Pyawbwe paleontological significances of this unit can be correlated Clays. with the Pyawbwe Formation of Salin Basin, Kama Clay near Pyay, and Shwetaung Clay of the Taungtalon area in the Kyaukse District. Figure 7. Pale brown to bluish grey shale lenticular sand at the stream section near the east entrance of Kyaukte Vill ). VI. KYAUKKOK FORMATION The name of this formation was given by Lepper (1933) as “ m ’’ ) in the Minbu District, Magway Region. In 1969, Aung Khin and Kyaw Win revised these “ m ” A. Distribution and Thickness Figure 6. Stratigraphic column of Pyawbwe Formation The Kyaukkok Formation is well exposed in both flanks at Kyaukte Chaung section. of the Major Anticline in the study area. This formation is International Journal of Scientific Engineering and Technology Research Volume.08, Jan-Dec-2019, Pages: 355-360 MAY THU AYE, KHIN SEIN MYINT well cropped out around the Ayesayti Pagoda Hill, The Kyaukkok Formation is not fossiliferous, fossils such Yankintaung (Aungmyay monastery) and west of Chauk as Oliva sp., Conus sp., Corbula sp., and shark teeth railway station. The exposed thickness of this formation is collected from the Kyaukkok Formation (Khin Aung Than, different in places. Generally it was 266 m thick in the 1983), from these faunal assemblages and stratigraphic western flank of anticline (Fig.8). position, the age of Kyaukkok Formation may be regarded as Middle Miocene. The marine fossils of gastropods (Conus B. Lithology sp.), coral and brachipods are collected from the Kyaukkok This formation is dominantly made up of brown to buff Formation in the present study. colored, fine to medium - grained, medium to thick - bedded sandstone with thin shale partings and sandstones with VII. IRRAWADDY FORMATION calcareous concretions rich in fossils. Thinly to medium - m “ W ’’ f bedded, yellowish brown sandstone interbedded with light Theobald (1873) to a sandy, gritty to pebbly sandstone grey shale are also found within the Kyaukkok Formation containing abundant silicified wood fossils which overlies (Fig.9). In the lower part of the formation, medium - grained the Upper Pegu Group. Later, Noething (1900) described the sandstones are more common, and gradually coarser towards m “ ’’ f m the upper part of this unit. Thick bedded sandstone Aung Khin and Kyaw Win (1969) renamed this rock as the comprises hard calcareous bands, concretions, mud clasts m ‘‘ m ’’ f f and calcic nodules. overlies unconformably the rocks of the Upper Pegu Group. C. Fauna and Age and Collection A. Distribution and Thickness The Irrawaddy Formation is well exposed in the Pinmagon, near the Ayeyarwaddy Bridge in the western flank of Chauk Anticline and near the Ohnmya village, NE of Chauk in the eastern flank. This formation is composed of brown to whitish color, coarse to gritty sandstones, mottle clays and occasional pebbly sandstones with silicified wood fossil. B. Lithology The sandstones of yellowish brown to buff colored, massive to thick - bedded with large scale cross bedding are mainly composed in Irrawaddy Formation of Chauk area. Gritty sandstones with pebbly layers are dominant in the lower part. The pebbles are ranging from ½ to 2 inches in Figure 8. diameter and they are well rounded and fairly sorted. ). Silicified wood fossils are locally developed in the lower part of this formation. VIII. GEOCHEMICAL CLASSIFICATION OF EARLY TO MIDDLE MIOCENE SANDSTONES The Pyawbwe Formation and Kyaukkok Formation are generally exposed along North–South trending in the study area.