An integrated paleomagnetic analysis program for stratigraphy labs and research projects
This paper describes a Windows-based paleomagnetic analysis program integrates on-screen visualization and analysis of paleomagnetic data and printing graphic outputs. The program is easy to understand and use with its graphic user interface. It accepts fixed length or delimited data files, each of which can contain up to 500 samples with a variable number of demagnetization steps (up to 50). The integrated toolboxes accept keyboard or copy-and-paste data input, and allow the user to calculate paleolatitudes, convert between spherical and Cartesian coordinates, and perform many functions of the main program. The main program converts an ASCII data file into a specially formatted file (*.mag) for random read/write access. After conversion, the *.mag file is automatically opened, and a list of sample is displayed in a small window. When a sample on the list is clicked, the associated demagnetization data are displayed in a nearby window. The user can visualize the data using the Zijderveld (/modified Zijderveld) projection and the stereographic (/Lambert equal-area) projection simultaneously or individually. The data visualized can be in either geographic or tilt-corrected coordinates, from all or certain demagnetization steps of a sample, or from a single demagnetization step of all samples. Characteristic directions of each sample are derived from a three-dimensional least-squares fit of selected demagnetization steps by principal component analysis (PCA). Mean directions from "Fisher" analysis are computed from click-selected samples using a designated 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. The graphic outputs can be printed on paper or screen-captured into graphic software, and the analytical results can be copied and pasted into word-processing programs. (C) 2003 Elsevier Science Ltd. All rights reserved.
demagnetization least-squares fit principal component analysis zijderveld projection stereographic projection lambert equal-area projection fisher analysis