| Abstract: | Abstract— We have measured excess Ir and depletion of 14C, two independent indicators of cosmic material, in peat cores from the central Tunguska impact site. Both Ir and 14C show pronounced anomalies in the same stratigraphical depth interval. We have estimated an integral deposition of nonradioactive cosmogenic C of 6.8 ± 1.0 mg C cm?2, and an integrated Ir deposition of 5.9 ± 1.2 pg Ir cm?2. The very high C/Ir ratio and a deduced δ13C value of +55 ± 10% relative to V Pee Dee Belemnite (VPDB) of the impactor material found in this study points towards a cometary type impactor, rather than a chondritic or achondritic asteroidal type impactor. |
