Geometrical analysis of structural data collected at high South latitude: A modular arithmetic method that addresses meridional convergence
Open-File Report
2007-1047-SRP-061
By: C.S. Siddoway and M.F. Siddoway
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Abstract
The convergence of meridians toward the South Pole causes unique problems for geometrical comparison of
structural geological and geophysical datasets from Antarctica. The true North reference direction ordinarily is used for
measuring and reporting vector data (strike, trend) in Antarctica, as elsewhere. However, over a latitude distance of just
100 km at 85° South, the angular difference in the true North direction exceeds 10°. Consequently, when performing a
regional tectonic analysis of vector data (strike, trend) for structures such as faults, dike arrays, or geophysical
lineaments oriented with respect to North at different sites, it is necessary to rotate the data to a common reference
direction. A modular arithmetic function, performed as a spreadsheet calculation, offers the means to unify data sets
from sites having different longitude position, by rotation to a common reference direction. The function is
SC ≡ SM + ∆L (mod 360), where SC = converted strike; SM = measured strike; ∆L = angle in degrees longitude between
reference longitude and study site; and 360, the divisor, is the number of degrees in Earth’s circumference. The method
is used to evaluate 1) paleomagnetic rotation of the Ellsworth-Whitmore Mountains with respect to the Transantarctic
Mountains, and 2) orogenic curvature of the Ross Orogen
Suggested Citation
Siddoway, C., Siddoway, M., 2007, Geometrical analysis of structural data collected at high South latitude: A modular arithmetic method that addresses meridional convergence: U.S. Geological Survey Open-File Report 2007-1047-SRP-061, Report: 5 p.; Plate: XLS file, https://doi.org/10.3133/ofr20071047SRP061.
ISSN: 2331-1258 (online)
Study Area
| Publication type | Report |
|---|---|
| Publication Subtype | USGS Numbered Series |
| Title | Geometrical analysis of structural data collected at high South latitude: A modular arithmetic method that addresses meridional convergence |
| Series title | Open-File Report |
| Series number | 2007-1047-SRP-061 |
| DOI | 10.3133/ofr20071047SRP061 |
| Year Published | 2007 |
| Language | English |
| Publisher | U.S. Geological Survey |
| Publisher location | Reston, VA |
| Description | Report: 5 p.; Plate: XLS file |
| Larger Work Type | Report |
| Larger Work Subtype | USGS Numbered Series |
| Larger Work Title | Antarctica: A Keystone in a Changing World--Online Proceedings for the Tenth International Symposium on Antarctic Earth Sciences. Santa Barbara, California, U.S.A.--August 26 to September 1, 2007 |
| Other Geospatial | Antarctica |
| Additional Online Files (Y/N) | Y |