GCN Circular 11230
N. R. Tanvir, K. Wiersema (U. Leicester) and A. J. Levan (U. Warwick) report on behalf of a larger collaboration: We observed the location of GRB 100906A (Markwardt et al. GCN 11227; Ivanov et al. GCN 11228; Melandri et al. GCN 11229) with the Gemini-North Telescope on Mauna Kea using the GMOS spectrograph. Observations began at 14:30 UT, approximately 40 minutes post burst. We detect strong continuum from the afterglow, and identify numerous absorption lines, including CIV (1458, 1551A), FeII (2344, 2374, 2383A) at a common redshift of z=1.727. Further analysis is ongoing. We acknowledge the support of Chad Trujillo in obtaining these observations.