PALEOMAGNETIC ANALYSIS PROGRAM FOR RESEARCH AND UNDERGRADUATE LABS

Paleomagnetic Analysis Program is a single integrated software package for on-screen visualization and analysis of paleomagnetic data, and for printing of graphic outputs. Undergraduate labs at Purdue learn the system within a half-hour, and complete a typical full paleomagnetic, pole and magnetostratigraphy analysis of 30-sample outcrops within the same lab period, including presentation graphics. Written in Visual Basic 6.0, this mouse-driven program has a graphic user interface, uses pull-down menus, and runs directly under Windows operating system or on Macintosh computers through Virtual PC. The program accepts both fixed-length and delimited data files, each of which can contain up to 500 samples, and each sample can have up to 50 demagnetization steps.

When the user clicks on a sample from the list in a window, the demagnetization information is displayed in new windows as numerical data and graphics. Data visualization methods include vector Zijderveld plots and stereographic- or Lambert equal-area projections in either geographic or tilt-corrected coordinates for selected demagnetization steps of a single sample or for a single demagnetization step of all samples. Characteristic directions of each sample are derived from a three-dimensional least-squares analysis of mouse-selected demagnetization steps. Mean directions from Fisher analysis are computed from click-selected samples using a selected demagnetization step or the characteristic directions. These mean directions are automatically computed for each polarity by a routine that compensates for pervasive overprint directions, and that can also utilize subjective weighting of sample directions. Output includes paper plots of all projections, and the capability to cut-and-paste analytical results and plots into word-processing or graphics programs.