Transects along the Taskan and Indigirka rivers

Principal Investigator: David Stone

Sampling trips down the Taskan River (1995), a tributary of the Kolyma, and the Indigirka River (1997) were made to collect for paleomagnetic and geochronologic studies. The main aim of the studies is to determine the paleogeography of the Kolyma-Omolon Superterrane (KOS). The major components of the KOS are the Omulevka and Prikolyma terranes, both of which are large fragments of apparently passive continental margin, and the Omolon terrane, which has a core containing Precambrian crystalline basement rocks. Russian paleomagnetic studies have indicated that these terranes originated as part of the Siberian craton, rifted off in Devonian time, drifted into the southern hemisphere, then back to their present locations in mid-Mesozoic time. The Taskan and Indigirka sampling programs were designed to sample suites of rocks from the Omulevka Terrane ranging in age from Cretaceous to Silurian. A problem which has appeared in all paleomagnetic studies of the older rocks of Northeast Russia is the near pervasive presence of a very steep magnetic overprint. This overprint is dominant in most of the samples we collected, but could often be removed by careful thermal magnetic cleaning, leaving a Characteristic Magnetization recorded in the last few demagnetization steps. These Characteristic magnetizations in the samples from the Taskan River sites give good paleomagnetic directions for Jurassic through Silurian time, and indicate a steady increase in paleolatitude. These results compare very favorably with results from the Omolon terrane obtained by our Russian colleagues, and indicate that the whole KOS was at equatorial latitudes in mid-Paleozoic time, and systematically migrated to their present high latitudes by Late Mesozoic time. When these paleolatitudes are compared with the paleolatitudes of the current positions of these terranes on the Siberian platform, it shows no displacement in Silurian-Devonian time, significant southerly displacement by latest Paleozoic, and a steady return to their current relative latitudes in Latest Jurassic-Early Cretaceous time.

Current news |Research disciplines| People|Current Research Topics|
Student Research Opportunities|Analytical Facilities| Publications | Home Page