Thailand is almost unique in having not only almost complete high-quality aeromagnetic and radiometric coverage of its land area, but in making the maps widely available via the website of the Department of Mineral Resources (DMR). The surveys were flown in the period from 1984 to 1989 by Kenting Earth Sciences for the DMR (Tulyatid & Fairhead 1999). The postings include maps of total magnetic intensity after correction for the regional background (the International Geomagnetic Reference Field or IGRF), of total gamma ray count and of count levels in the ‘thorium’ and ‘uranium’ channels. Thorium, uranium and also potassium sources can be discriminated on the basis of the energy of the gamma-rays produced, and surface-layer concentrations can be estimated once the data have been corrected for cosmic rays and overlapping radiation peaks from other sources. A Ternary or ‘false colour’ map, in which the potassium, uranium and thorium counts determine the relative intensities of the primary colours, is also posted.
Gravity coverage is less uniform. Regional data have been obtained by a number of organizations, and some of the processed results have been filed with the Bureau Gravimeetrique International in Toulouse. A somewhat more comprehensive database has been established by the Royal Thai Survey Department (RTSD) in order to define the geoid. This surface, defined as the gravity equi-potential that at sea coincides with mean sea level, provides the surveyor’s reference surface inland. More detailed work by other organizations has been concentrated in the sedimentary basins,
Figures & Tables
The Geology of Thailand
This is the first volume in the English language to cover the entire range of the geology of Thailand since the joint Thai—US account by Brown et al. exactly 60 years ago. Over this period there has been a phenomenal growth in interest in this core area of SE Asia. This has been led by geologists in Thailand, but with important and highly significant input from geologists based elsewhere in Asia and in Europe, Australasia and North America. Some of that research was prompted by commercial considerations, since Thailand has important energy and mineral resources, while other research has sought to understand better the stratigraphic and structural history, including the plate-tectonic story which Thailand's rocks reveal. This new volume seeks to bring together all of this knowledge into a single accessible book; it is the work of an international team drawn from Thailand, Japan, Australia, USA, Canada, Germany and the UK.