Spatial modeling by computer.- Methods of thematic map comparison.- A study of two-dimensional grain sequences in rocks.- Application of fuzzy sets to the subdivision of geological units.- Quality of time scales - a statistical appraisal.- Biased kriging: a theoretical development.- Kriging hydrochemical data.- Analysis of massive sulfides within the Mountain View Area of the Stillwater Complex, Montana - a statistical formulation and test of the sulfide liquid immiscibility model.- Computer processing of dipmeter log data: enhancement of a subsurface exploration tool.- Crustal abundance modeling of mineral resources: recent investigations and preliminary results.- Use of decision theory for pattern recognition in geology.- Lithological-mineralogical peculiarities of sedimentary rocks in abnormal thermobarc conditions and prediction of oil and gas content at great depths.- GEOL: an interactive system for data processing.- Numerical classification of Mesozoic volcanic rocks in the eastern part of China and its geological significance.

Since founding at the 23rd International Geological Congress in Prague in 1968, the International Association for Mathematical Geology has organized sessions in conjunction with the Congress. The 27th IGC in Moscow was no exception and the IAMG again held sessions and assisted the Congress in organizing Section 20 -Mathematical Geology and Geological Information ( D. F. Merriam, D. A. Rodionov, and R. Sinding-Larsen, conveners). All together 128 abstracts were published in the technical proceedings. Several of the papers were published prior to the Congress, others were not available, and others deemed not appropriate for publication in this volume. This collection then contains those papers aVailable and representative of the sessions. The collection is truly international with contributions from Canada, China, France, Poland, the UK, USA, and USSR. They are representative of the state-of-the-art as of the early 1980s in a variety of fields. The application of geomathematics/geostatistics to geological problems has been hastened by the availability of computers. These papers reflect that orientation -most of the results would not have been possible without the use of computers. Most of the approaches utilize techniques readily aVailable and adapted to solving geological problems -simulation, image analysis, decision theory, fuzzy sets, etc. However, one area, that of geostatistiques which includes Kriging, has been designed especially for use by earth scientists of the French school to solve geological problems.