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

Abstract

Cheko, a small lake located in Siberia close to the epicentre of the 1908 Tunguska explosion, might fill a crater left by the impact of a fragment of a Cosmic Body. Sediment cores from the lake’s bottom were studied to support or reject this hypothesis. A 175‐cm long core, collected near the center of the lake, consists of an upper ∼1 m thick sequence of lacustrine deposits overlaying coarser chaotic material. 210Pb and 137Cs indicate that the transition from lower to upper sequence occurred close to the time of the Tunguska Event. Pollen analysis reveals that remains of aquatic plants are abundant in the top post‐1908 sequence, but are absent in the lower pre‐1908 portion of the core. These results, including organic C, N and δ13C data, suggest that Lake Cheko formed at the time of the Tunguska Event.

New evidence of meteoritic origin of the Tunguska cosmic body

“…The origin of the Tunguska blast was explained by a huge meteorite impact (e.g. 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.…”

“…Later Gasperini et al (2009) provided more evidence that the crater of interest was formed at the time of the Tunguska event.…”

Risk assessment of Tunguska-type airbursts

“…However, estimates are based on man-made explosions, and the real impact from Tunguska-type airbursts remains unknown at the present time. Moreover, there is a debate about a possible impact crater at the Tunguska site (Gasperini et al 2007(Gasperini et al , 2008(Gasperini et al , 2009Collins et al 2008), which adds even more uncertainty on the potential of ''Tunguska-generated'' tsunamis. Although the 1908 Tunguska event caused a medium-sized earthquake, it is unclear how ground shaking would significantly increase losses compared to the shock wave.…”

Origin of John’s Stone: A quartzitic boulder from the site of the 1908 Tunguska (Siberia) explosion

“…If the Tunguska cosmic body were quartzitic, the quartz grains found in sediment cores collected from Lake Cheko (Gasperini et al, 2009) could have resulted from dust produced by the explosion in the atmosphere of the main body. Abundant production of dust was documented in the Chelyabinsk event (Borovicka et al, 2013;Popova et al, 2013).…”

“…Clear-cut non-controversial fragments of the cosmic body have never been found, although a possible impact crater filled up by a %350 m diameter lake (Lake Cheko) has been reported ca. 8 km NNW of the TE epicenter (Gasperini et al, 2007(Gasperini et al, , 2008(Gasperini et al, , 2009(Gasperini et al, , 2012(Gasperini et al, , 2014. An alternative explanation is that the TE was caused by the explosion in the atmosphere of high pressure gases ejected from the Earth's mantle in cryptoexplosion events (Ol'khovatov, 2002;Kundt, 2001;Vannucchi et al, 2015).…”