Insights into the Position of Kyrgyzstan in the Silurian

Abstract

This study examined 101 cores from 16 basaltic flows from the Silurian in northern Kyrgyzstan with the aim of understanding the paleoposition of Kyrgyzstan. This is important as very little is known about the Kazakhstania terranes which comprises Kyrgyzstan in the early to middle Paleozoic. The result of this study may help us understand the amalgamation process of the island arcs and microcontinents that were thought to have joined together in the Ordovician. The magnetic behavior of the cores from this collection seems to suggest that both hematite and low-titanium magnetite are present as the magnetic carrier. Characteristic magnetization is carried by low-titanium magnetite while secondary magnetization is prominent and carried by hematite. The magnetic behavior of samples with hematite could reflect ancient magnetic directions but are poorly clustered. In contrast, samples with magnetite show steep magnetic directions that resemble Cenozoic magnetizations. To increase accuracy and credibility of the data, visual inspection and reliability criteria of Van der Voo (1990) were used to filter highly erroneous samples. Overall formation mean of the study sites gave paleomagnetic directions that are southerly and up and northerly and down. Scattered directions are present owing to undefined folding events and complicated tectonic history in the study area. U-Pb radiometric age analysis of zircon from the basalt revealed an age of 423 ± 5.4Ma with a confidence level of 96.1%. The expected direction from volcanic rocks of this locality is not steep if the age is Silurian; however this study has obtained both steep and shallow directions with noisy behavior in thermal demagnetization and failing a fold test. We attribute this disappointing remanence to late-stage alteration. By considering only characteristic magnetic directions, the final mean of site directions was calculated to have declination and inclination of 181.7° and -86.6° respectively with the a95 of 12.3° which does not agree with an expected direction of Silurian age.