PALEOMAGNETISM OF THE CARBONIFEROUS TEPUEL GROUP, CENTRAL PATAGONIA, ARGENTINA

Samples of the Carboniferous glaciogenic sequences of the Tepuel Group , western central Patagonia, Argentina, were collected from 23 sites i n two localities, Sierra de Tepuel (43.7 degrees S, 70.5 degrees W) an d Las Salinas (43.2 degrees S, 70.3 degrees W). Most were fine sandsto nes to siltstones of late Visean to Westphalian age. A characteristic remanent magnetization was determined in most sites by alternating fie ld and/or thermal cleaning. At Sierra de Tepuel all samples were parti ally overprinted by a secondary magnetization apparently related to Me sozoic magmatic activity in this area. However, site mean directions o f the characteristic remanence from both localities passed a tilt test , indicating a pretectonic (pre-Early Permian?) magnetization. Isother mal remanent magnetization experiments showed magnetite as the main an d often the only magnetic carrier, while thin section analyses indicat ed a detrital origin for this mineral, suggesting a depositional or po stdepositional magnetization. The paleomagnetic pole for the Tepuel Gr oup (Namurian-Westphalian) at 316.1 degrees E, 31.7 degrees S (number of sites N=16, minor and major semi-axes of confidence delta p=15.0 de grees, delta m=16.0 degrees), is considered a key pole for the Middle Carboniferous of South America and Gondwana, confirming the apparent p olar wander path for the supercontinent for which the pole moved from central to southern Africa in the Early Carboniferous, followed by a r apid motion from southern Africa to Antarctica during the late Westpha lian. The agreement of the Tepuel pole with this Gondwanan path confir m that Patagonia was already part of South America by the Middle Carbo niferous.