Geoinformatics

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In this study, we constructed an objective three dimensional geological model (3DGM) of the Kisarazu distinct, Chiba Prefecture, central Japan based on logical procedures. In this modeling, we first constructed a Logical Model of Geological Structure (LMGS) that defines a logical relation between geological boundary surfaces and geological units. Secondly, we generated Digital Elevation Models (DEMs) of geological boundary surfaces using 44 geological columns. Thirdly, we constructed a 3DGM using the LMGS and the DEMs. Finally, we generated a geological map and some geological cross-sections from the logic-based 3DGM. In addition, we numerically and visually compared these results with the geometric-based geological map and geological cross-sections. As a result, the logic-based model was similar to the geometric-based one, but detailed comparison revealed many differences between these two models. Most possible causes of the differences are (1) shapes of topographic surfaces, (2) estimation method and drawing method of geological boundary, and (3) intervention of modeler's knowledge and experience in geometric procedures.

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A point-count application on the MS-Excel VBA (Visual Basic for Applications) has been developed. This program is started by the switch of User Form Control in an Excel spread sheet, and counting is driven by the typing of personal computer keyboard. Up to fifteen mineral species are countable by single-hand touch typing of keyboard for petrologic modal analysis. With changing mineral names of the Excel sheet, this tally counter can be used to count other things, such as counting of microfossils. This application is downloadable from the web page of the Japan Society of Geoinformatics.

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