 |
Science Frontiers ONLINE No. 125: Sep-Oct 1999 |
|
| 
|
Fossil Meteorites
Over a century ago, astronomer H.W.M. Olbers (of Olbers Paradox fame) remarked that meteorites are extremely rare in the fossil record. While meteorites are found in profusion in some specially favored surface deposits (Antarctica and Australia's Nullarbor Plain), there are very few records of any being found in the immense volumes of coal, gold ores, and other geological materials that have been mined down the centuries. Of course, many meteorites escaped the notice of miners who were looking for something else. Nevertheless, few have been reported from strata more than a few thousand years old. (See ESI8 in Neglected Geo logical Anomalies.)
It is therefore surprising that a veritable lode of fossil meteorites has been found in a limestone quarry at Kinnekulle, in southern Sweden.
"During the sawing of a few thousand cubic meters of Ordovician limestone into 2-3 cm thick slices, 25 fossil meteorites have been found. All meteorites, except, four, have been found in a 60 cm thick bed called the Archaeologist. This bed represents a few hundred thousand years and contains several hard ground surfaces...Many of the Archaeologist meteorites are prominently angular in shape whereas others are round. This seems difficult to reconcile with an atmospheric breakup of a single large meteorite."
B. Schmitz and M. Tassinari, the authors of this paper, suggest that this rare concentration of fossil meteorites represents an unusual event in the solarsystem history, possibly a major collision in the asteroid belt.
(Schmitz, Birger, and Tassinari, Mario; "Early Ordovician Meteorites: How Many Falls?" Eos, 79:F50, 1998.)
Comment. It should be added that tektites and microtektites (impact debris) are likewise found mainly in recent, superficial deposits, even though many ancient impact craters are now recognized on earth.