Isotopic–geochemical study of nitrogen and carbon in peat from the Tunguska Cosmic Body explosion site

Abstract

Isotopic-geochemical investigations were carried out on peat samples from the 1908 Tunguska Cosmic Body (TCB) explosion area. We analyzed two peat columns from the Northern peat bog, sampled in 1998, and from the Raketka peat bog, sampled during the 1999 Italian expedition, both located near the epicenter of the TCB explosion area. At the depth of the "catastrophic" layer, formed in 1908, and deeper, one can observe shifts in the isotopic composition of nitrogen (up to ⌬ 15 N ϭ ϩ7.2‰) and carbon (up to ⌬ 13 C ϭ ϩ2‰) and also an increase in the nitrogen concentration compared to those in the normal, upper layers, unaffected by the Tunguska event. One possible explanation for these effects could be the presence of nitrogen and carbon from TCB material and from acid rains, following the TCB explosion, in the "catastrophic" and "precatastrophic" layers of peat. We found that the highest quantity of isotopically heavy nitrogen fell near the explosion epicenter and along the TCB trajectory. It is calculated that 200,000 tons of nitrogen fell over the area of devastated forest, i.e., only about 30% of the value calculated by Rasmussen et al. (1984). This discrepancy is probably caused by part of the nitrogen having dispersed in the Earth's atmosphere. The isotopic effects observed in the peat agree with the results of previous investigations (Kolesnikov et al., 1998a(Kolesnikov et al., , 1998bRasmussen et al., 1999) and also with the increased content of iridium and other platinoids found in the corresponding peat layers of other columns (Hou et al., 1998(Hou et al., , 2000. These data favor the hypothesis of a cosmochemical origin of the isotopic effects.

A multitracer study of peat profiles from Tunguska, Siberia

“…7), with lower concentrations in the upper 30 cm and higher values below this level suggests that the bog is presently ombrotrophic, in agreement with the characteristic presence of Sphagnum indicated by Kolesnikov et al (2003). The same trend is observed also for Sr that is linearly correlated with Ca in the peat profile (R 2 = 0.87, p < 0.06) as a result of their similar ionic radii leading to a great geochemical affinity.…”

“…Since then a certain number of papers reporting results arising from the application of several analytical and isotopic techniques applied to Tunguska peat have been published. All of them indicate the occurrence of some chemical (Iridium and Platinum group elements) and/or of isotopic anomalies possibly connected to TCB (Kolesnikov et al, 1998a,b;Hou et al, 1998;Kolesnikov et al, 1999;Rasmussen et al, 1999;Hou et al, 2000;Kolesnikov et al, 2003;Hou et al, 2004).…”

New evidence of meteoritic origin of the Tunguska cosmic body

“…Yavnel, 1957;Florensky, 1963;Longo et al, 1994;Serra et al, 1994;Longo, 2007;Gasperini et al, 2007Gasperini et al, , 2009Badyukov et al, 2011) or by a comet (e.g. Florensky, 1968Florensky, a, 1968Golenetsky et al, 1977;Ganapathy et al, 1983;Zbik, 1984;Nazarov et al, 1990;Hou et al, 1998;Kolesnikov et al, 1999;Rasmussen et al, 1999;Kolesnikov et al, 2003Kolesnikov et al, , 2005Gladysheva, 2007), or by a cosmic body. However, no clear differences between comet and meteorite impacts were established (Dolgov et al, 1973;Nazarov et al, 1983;Hou et al, 2000;2004;Kolesnikov et al, 2005).…”

Sediments from Lake Cheko (Siberia), a possible impact crater for the 1908 Tunguska Event

“…Geochemical markers of a cosmic impact in the Tunguska region Serra et al, 1994;Hou et al, 1998Hou et al, , 2004Kolesnikov et al, 1999Kolesnikov et al, , 2003, although compatible with the hypothesis of a cosmic body impact, are by no means conclusive and several different scenarios have been proposed for the TE (see Longo, 2007).…”