Photo-interpretation for geological mapping of Changwat Khon Kaen and adjacent areas

Abstract

The study area is located in Changwat Khon-Kaen and its vicinity covering the area of approximately 3,700 aquare kilometers. The west and north of the area are bounded by mountainous-hilly terrains of the Mesozoic sedimentary rocks whereas in the central parts, the undulating terrains are wide spread with the surficial deposits of Tertiary to Quaternary. Lam Chi and Lam Nam Phong are the two main rivers running from the north and southwest to the east forming board flood plains. The objective of the study is to establish appropriate mapping schemes with reference to the remote sensing techniques. The ultimate output anticipated is the photogeological map of the proposed area of the study. The aerial photographs, Landsat imageries and appropriate topographic maps are utilized. With time and facilities available, the visual image interpretation is employed, together with spot field observations. After the existing data are analysed and concluded, the mapping schemes are then proposed and tried. The results are collected and organized in photo-analysis charts, Finally, the information presentation is then illustrated in forms of photogeological map of the study area. The results of the study reveal that the aerial photographs of World Wide Survey Series (1953 A.D.) of about 1:40,000 scale and the Landsat imageries recorded at just the end of the rainy season are the most suitable base data for visual interpretation. However, for the Landsat imageries, those recorded on October 7, 1979 of band 7 gave the best images for this work. The study yields 10 Photogeological units of the Unit A, B, C, D1, D2, E, M1,M2, M3 and Q are observed in ascending sequences. The Unit Q can be further divided into Q1, Q2, Q3, and Q4 subunits based on their properties and geological appearance. Thickness of some measurable units are calculated and presented. The geological structure observed is mostly flat-lying of a large shallow major syncline through and their axis lies almost north-south. A series of large second – order folds and photolineament of fractures are commonly recognized. However, this area can be considered very suitable location for the study of the representative of Mesozoic rocks through the surficial unconsolidated deposits of Quaternary which extensively appear in the whole Khorat Plateau.