Researchers from Herzen RSPU have discovered new evidence in Lake Onego supporting the hypothesis of a large cosmic body impact on Earth approximately 12.8 thousand years ago, "Pervy Tekhnichesky" was informed by the university's press service. The marker of the ancient catastrophe is the "pink horizon" — a layer with a sharp change in color in bottom sediments, which is traceable throughout the entire water area of the lake.
Dean of the Faculty of Geography, Dmitry Subetto, stated that high concentrations of iron oxide particles, ranging from tens to hundreds of micrometers in size, were found in this layer. According to him, the clear boundary of the layer and its wide distribution may indicate an external input of matter — for example, cosmic dust. The finding strengthens the version that the "pink horizon" is associated with a meteorite impact 12,900–12,800 years ago, which could have triggered a sharp cooling for a thousand years.
For the first time, ultra-precise magnetic measurements with a step of only 4–5 mm were used to study the layer, which allowed obtaining its "magnetic fingerprint" for comparison with sediments in other regions. Microbial mats and biofilms, presumably formed at a depth of more than 100 meters, were also found within the horizon.
The study allowed reconstructing the history of Lake Onego after the last glaciation. About 13 thousand years ago, the reservoir was three times larger than it is today — its area reached 33 thousand sq. km, the water volume was 900 cubic km, and the maximum depth reached 300 meters. Over 1–2 thousand years, about 52 cubic km of bottom sediments (more than 30 billion tons of dry matter) accumulated in it — 10 times more than in the subsequent 9–10 thousand years.