PRELIMINARY PALEOMAGNETIC DATA ON LATE CAMBRIAN TO ORDOVICIAN CARBONATE BEDS OF TAMDY SERIES FROM THE LESSER KARATAU MICROCONTINENT, SOUTH KAZAKHSTAN

The Ural-Mongol fold belt is considered to play a significant role in the formation of Eurasia supercontinent. It consists of Precambrian crust and several island arc domains and stretches from North Urals to Kazakhstan and Tien Shan to Altai and Mongolia to the Pacific. Due to nearly complete absence of reliable age determination and paleomagnetic data from the associated microcontinents the evolutionary history of the UMB is poorly understood. To better understand the evolution of the UMB during the Paleozoic times (Late Cambrian-Ordovician) we undertook a paleomagnetic study of the Carbonate beds of Kyrshabakty, Chulaktau and Tamdy Suites of the Tamdy series in the Lesser Karatau microcontinent in South Kazakhstan. The Tamdy series of rocks consists of massive dolomites of Nemakit-Daldynian age and Cambrian to Ordovician limestones. The abundant fossil fauna found in these rocks assign a Cambrian-Ordovician age to these rocks. We present some preliminary paleomagnetic data from these massive dolomites/limestones. Out of 68 sites sampled, 20 are fully demagnetized up to date using cryogenic thermal demagnetization technique. Apart from a low temperature component aligned along the present day field, an intermediate to high temperature component is also successfully isolated from most of the samples. This intermediate to high temperature component of ubiquitously reverse polarity is of post folding origin as evident from the tilt corrected data and was likely to have been acquired in the late Paleozoic. A second high-temperature component observed in several sites, indicating paleolatitudes of ~20 degrees is consistent with a peri-Siberian position for Lesser Karatau. In our presentation, we will discuss various tectonic implications of this data to understand the paleogeography and evolution of Eurasia.