Paleomagnetic results from the Silurian of the Yangtze paraplatform

Abstract

Samples have been collected from sites from three localities located in Sichuan and in Yunnan provinces. The samples were taken from limestones and red siltstones covering most of the Silurian of the South China Block. The results from the limestone sites were disappointing and all the sites that yielded successful results were from red siltstones. Characteristic high temperature components were successfully isolated from fifteen of these sites. The sites from Xiushan County, Sichuan (28.48 ° N, 108.99 ° E), successfully pass the fold test at the 99% level indicating that the magnetization was acquired before folding in the Mesozoic. The direction obtained from this locality is directed toward the east with shallow positive inclinations ( D = 85.6°, I = 12.1°, α 95 = 5.33°); the results obtained from a single red bed locality from Qijiang County, Sichuan (28.58 °N, 106.85 °E), yield a similar direction. The results from the upper Silurian of Yunnan (25.5°N, 103.73° E) were obtained from only two sites and the isolated directions were towards the west with shallow inclinations. This direction is opposed to the characteristic directions obtained from Sichuan and are interpreted as a reversed Silurian direction. The paleomagnetic pole position determined from all sites given equal weight ( N = 15) falls at 4.9°N lat., 194.7°E long, with α 95 = 5.61°.