In regard to Tunguska and bioturbation, Meteorites USA asked: “Paul H's post on bioturbation brings up an interesting question. The first expedition led by Leonid Kulik to Tunguska in 1927 to study the devastation and search for meteorites happened 19 years AFTER the event in 1908, (He had an earlier expedition in 1921 but wasn't successful in reaching the epicenter until 1927).
19 years is a LONG time for meteorites in the forested and swampy environment full of little critters, insects, and plants that could bury any stones. How deep can meteorites be buried in 19 years of snow, rain storms, mudslides, spring melt, critters, ants, termites, and other animals? This is very interesting point, because 19 years likely would be sufficient time for relatively small fragments of meteorite to be buried. Dr. Donald Johnson found right after buying the in which he lives, a layer of bricks buried beneath 2 or 3 inches of soil. This had been bricks that had been placed on the ground, without using any mortar hold them together, as simple patio. Given when the house was built, the bricks could not have been placed on the ground more than 20 years before he found them. It was this discovery that inspired him to start his research on bioturbation from what can remember of his class lectures. The depth of burial at Tunguska, would depend, in part, on how deep any permafrost present at that location melts each year and how deep that and other processes allow bioturbation to occur. I suspect that between bioturbation and cryturbation, any small and even relatively large, meteorite fragment would very quickly disappear beneath the soil and muck. It would be interesting to find some specific information about the soils present at the Tunguska Site and do a detailed taphonomic analysis of what the soil and sediment data means in terms of "meteorite taphonomy". It would be no different then doing an analysis of site formation processes for an archaeological survey area in order to either predict where the archaeologists should look for artifacts or in order to interpret what was or was not found by the archaeologists when they surveyed an area. I have done enough site formation processes analyses for archaeologists, that I could, for a scientific search for meteorites, do the same thing for a strewn field and make a prediction of where a person would expect meteorites to be found. Best Regards, Paul H. Bets Regards, Paul Paul H. ______________________________________________ http://www.meteoritecentral.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list