Stratigraphy and sedimentology of the Sierra de Beauvoir.

D. R. MARTINIONI

Ushuaia

Otro; Newsletter - SAMC News - Project Reports; 1995

IUGS-IGCP - Project 381 South Atlantic Mesozoic Correlations

REPORT SUMMARY:   The study focus on the stratigraphy, sedimentology, and paleontology of the Mesozoic marine succession north of Lago Fagnano. In the previous literature all the rocks just north of Lago Fagnano were assigned to a single unit (the Beauvoir Formation), assumed to be of Early Cretaceous age. However, this assumption was based on local observations and not on field, systematic mapping of the area. Preliminary results, intended to be published next year, indicate that the sedimentary succession is more complicated, including several stratigaphic units of Jurassic, Cretaceous, and Tertiary age. In addition, important evidence was also found that allows for a better understanding of rocks similar to basaltic spilites already known elsewhere in the cordillera. The central belt of the Lemaire Formation and the associated melanocratic rocks were up-thrusted against the Yahgan Formation. In the fault zone, two main north vergent thrust faults were recognized. The thrusts parallel the lithological boundaries and coincide with major NW-SE lineaments, clearly visible in a radar multitemporal image (ERS1-SAR), In the nearby Chilean area to the west these lineaments are in agreement with a previously recognized major, north vergent thrust fault along which the basement rocks were uplifted against sedimentary rocks similar to the Yahgan Formation.