Petrographic Characteristics and Depositional Environment Evolution of Middle Miocene Sediments in the Thien Ung - Mang Cau Structure of Nam Con Son Basin

• Main Authors: Pham Bao Ngoc, Tran Nghi, Nguyen Trong Tin, Tran Van Tri, Nguyen Thi Tuyen, Tran Thi Dung, Nguyen Thi Phuong Thao
• Format: Article
• Language: English
• Published: Geological Agency 2017-08-01
• Series: Indonesian Journal on Geoscience
• Subjects: calcareous sandstone; calcarinate sandstone; calcareous clayey siltstone; bituminous calcareous claystone; turbulent flow structure; Thien Ung - Mang Cau structure
• Online Access: https://ijog.geologi.esdm.go.id/index.php/IJOG/article/view/387
• ISSN: 2355-9314; 2355-9306

<p><span>DOI: 10.17014/ijog.4.3.143-157</span></p><p>This paper introduces the petrographic characteristics and depositional environment of Middle Miocene rocks of the Thien Ung - Mang Cau structure in the central area of Nam Con Son Basin based on the results of analyzing thin sections and structural characteristics of core samples. Middle Miocene sedimentary rocks in the studied area can be divided into three groups: (1) Group of terrigenous rocks comprising greywacke sandstone, arkosic sandstone, lithic-quartz sandstone, greywacke-lithic sandstone, oligomictic siltstone, and bitumenous claystone; (2) Group of carbonate rocks comprising dolomitic limestone and bituminous limestone; (3) Mixed group comprising calcareous sandstone, calcarinate sandstone, arenaceous limestone, calcareous claystone, calcareous silty claystone, dolomitic limestone containing silt, and bitumen. The depositional environment is expressed through petrographic characteristics and structure of the sedimentary rocks in core samples. The greywacke and arkosic sandstones are of medium grain size, poor sorting and roundness, and siliceous cement characterizing the alluvial and estuarine fan environment expressed by massive structure of core samples. The mixed calcareous limestone, arenaceous dolomitic limestone, and calcareous and bituminous clayey siltstone in the core samples are of turbulent flow structure characterizing shallow bay environment with the action of bottom currents. The dolomitic limestones are of relatively homogeneous, of microgranular and fine-granular texture, precipitated in a weakly reducing, semi-closed, and relatively calm bay environment.</p>