The Koro Toro, Kossom Bougoudi and Kollé sites (KT, KB, KL).
These three groups of fossiliferous sites are quite close to one another. Fossils, notably of mammals, are aged between 3 and 5 million years. Between these zones, other fossils were located, most commonly fish which are locally abundant. Sites further from the ‘central zone’ yielded several well-preserved elephant teeth, which are much more recent, some being only a few thousand years old.
The KT sites (KT).
The KT sites were located from January, 1994 to July, 2000 in the following order : KT1 to KT 11, January 1994 ; KT12 and KT 13, January, 1995 ; KT14 to KT 35, January, 1996 ;KT36 to KT38, November, 1997 ; KT39, January, 1998 ; KT40, July, 2000 (KT30 doesn’t exist). The KT area, being the first fossiliferous zone found, was surveyed in such a way as to locate the sites which are dispersed over the landscape so as to document the overall potential of the area.The central fossiliferous zone is in fact subdivided into two, both of which are on the footslopes of a scarp represented by sand ridges which bordered ancient Lake Mega-Chad. The zone, having yielded australopithecines at sites KT12, KT13 and KT40 is located at the foot of a group of parallel sand ridges which are higher than 340 metres altitude, overlooking the fossiliferous zone by some 20 metres. These three sites are in a similar topographic situation, at the foot of the first sand ridge (or near the foot of the ridge in the case of KT13). Towards the west, the altitude decreases gradually towards the regions covered in diatomite or sand, but this area did not yield any fossils other than fish. To the east, in the sand ridges and beyond, sub-fossils of mammals (notably bovids) were found.
The Kollé sites (KL).
With the exception of sites 1 and 18 which are far from the main fossil area, each of which yielded a single fossil of a recent elephant, the sites of Kollé are located on a clearly defined plateau. Scenes from Google Earth indicate that the sites occur between 320 metres in the south and 330 metres in the north, most of them between 324 and 320 metres. This plateau has clear margins, with relief of some 20 metres in the south and west, the edge of the plateau being either a scarp as in the west and south-west, or by a regular but pronounced slope. To the north-west the shape of the scarp is that of a thick sand ridge. From south-east to the north, the plateau is delimited by a sereis of sand ridges ranging in altitude from 335-340 metres, blending northeastwards into a dune field.
The first expedition to Kollé was done in 1995 by Pierre Vincent and Alain and Najia Beauvilain when returning from the discovery of the meteorite impact at Gwéni-Fada. The abundance of fossils was noted and the co-ordinates of future sies were noted down (KL3 and KL5). The sites were registered in January, 1996 (KL1 to KL15) ; KLX in January 1997 ;KL17, 18 and 20 in 1998; and KL 22in 1999 (KL5 and KL 19 are identical as are KL14 and KL15).
Some sites are a few metres from each other, such as KL2, KL3 and KL10. In fact, on this plateau which covers about 900 hectares, the numbering of sites was based on spectacular fossil finds, most often elephants, so as to determine their location precisely.
The Kossom Bougoudi sites (KB).
With the exception of some distant sites such as KB1, KB12, KB26, the main fossiliferous area of KB is located to the north of and at the foot of a clearly marked scarp. The sites are between 301 and 295 metres in altitude, declining in altitude northwards. To the east of the main zone, sites KB27, KB30 and KB31 are in similar topographic positions. They were discovered from January, 1996 for KB1 to KB3 ; in 1997 for KB4 to KB27 ; and in 1998 for KB28 to KB31 (KB5 and KB6 are the same site and KB29 does not exist).