Abstract of talk by Marie-Agnès CourtyCNRS-CM. Lab. de Science des Sols et Hydrologic, INA P-G, 78850 Grignon, France. email: fedoroff[at]diamant.jouy.inra.drPresented at the SIS Conference: Natural Catastrophes during Bronze Age Civilisations (11th-13th July 1997)
Further investigations allow to re-examine the nature, age, causes and effects of the third millennium catastrophe identified from our earlier findings. Test on various late Gird millennium BC archaeological deposit and contemporaneous provides evidence for the regional occurrence in northern Syria of a layer with an uncommon petrographic assemblage, dated at ca. 2350 BC (transition between late Early Dynastic and Early Akkad). It consists of fine send-sized, well sorted spherules of various composition (silica, silicates and fibro-radiated calcite), millimetric fragments of a black, vesicular, amorphous material made of silicates with Mg-Ca carbonate and phosphate inclusions, ovoid micro-aggregates made of densely packed crystals (calcite, gypsum or feldspars) and exogenous angular fragments of a coarse crystallised igneous rock. All these particles are only present in this specific layer and are finely mixed with mud-brick debris or with a burnt surface horizon in the contemporaneous soils. In occupation sequences, the layer displays an uncommon dense packing of sand-sized, very porous aggregates that suggests disintegration of the mud-brick construction by an air blast. In the virgin soil, the burnt horizon contains black soot and graphite, and appears to have been instantaneously fossilised by a rapid and uncommon colluvial wash. Occurrence in a previously recorded thick tephra deposit of particles identical to some of the mysterious layer and resemblance of its original pseudo-sand fabric with t he exploded one of the mysterious layer confirms that the later is contemporaneous with the tephra deposit It has been however impossible to find typical tephra shards in sites located at a few km around the one with the tephra deposit The restricted occurrence of the later suggests that the massive tephra accumulation can no longer be considered as a typical fallout derived from the dispersion of material from a terrestrial volcanic explosion. Analytical investigations in various directions have been unable, so far, to refute or confirm that a cosmic event would have been the cause for production of both the widely distributed mysterious particles and the localised thick tephra. Origin of this mysterious phenomena still remains unsolved.
The excellent stratigraphical correlation between sites that are distant of a few hundred km clearly shows that the instantaneous dust fallout, previously considered as the initiative mechanism to the ca. 2200 yr BC abrupt climate change, occurred more than one hundred years earlier. The loose soil fabric, originally correlated with effects of strong winds and rapid establishment of aridity, can now be re-interpreted and possibly assigned to a violent blow-up. The theory of the Akkad empire collapse has, however, lost its basis. Soil specialists, geochemists and archaeologists should join their effort to solve this problem, and debate the exact nature of the socio cultural echo to this extraordinary event Our study illustrates the exceptional potential of archaeological sites to offer well preserved sedimentary archives of instantaneous phenomena that have shacked past terrestrial environments. It also demonstrates the importance of a high temporal resolution for debating causality of natural catastrophe on societal phenomena. Soil-sedimentary markers are in a way less subjective than historical sources for providing such a precision, although their interpretation might also be controversial, particularly when facing lack of analogues from the past or the present.