Olduvai
Gorge
Olduvai Gorge is an archaeological
site located in the eastern Serengeti Plains, which is in
northern Tanzania. The gorge is a very steep sided ravine
roughly 30 miles long and 295 ft. deep. Exposed deposits
show rich fossil fauna, many hominid remains and items belonging
to the one of the oldest stone tool technologies, called
Olduwan. The time span of the objects recovered date from
2,100,000 to 15,000 years ago.
The main Olduvai Beds are
in a lake basin about 16 miles in diameter. The rocks under
the basin date to 5.3 million years ago. There have been
seven major Beds distinguished they are ranked from oldest
to youngest; Bed I, Bed II, Bed III, Bed IV, the Masek Beds,
the Ndutu Beds, and Baisiusiu Beds.
Bed I dates to 2,100,000 years
old and is 197 feet thick. It is mainly formed of lava flows,
volcanic-ash deposits and other sediments. The upper part
of the bed contains varied fauna and evidence of the Olduwan
industry. Skeletal remains of hominids are assigned to the
Homo Habilis an Australopithecus Boisei families. Campsites
and what is believed to be a butchery site have also been
excavated from this bed.
The Hominid living sites in
Bed I are found mainly where streams from the volcanic highlands
carried fresh water to Olduvai lake. The conditions for
the preservation of the sites is mainly due to the ash falls
from the nearby volcanoes and the inconsistency of the lake's
depth. The debris found at the sites are various Olduwan
tools, bone and teeth from animals, mainly from fair sized
antelopes. Also a loosely built circle of lava blocks was
found, suggesting that crude shelters were formed here as
well.
The living sites in Beds II-IV
are normally found in what would have been river and stream
channels. Therefore, many of the sites were displaced by
water action.
Bed II is 66-98 feet thick
and is 1,150,000 to 1,700,000 years old. It has two main
divisions of rock layer, upper and lower, that were separated
by an erosional break. The lower part of Bed II is similar
to Bed I. The upper part was formed after fault shifts had
reduced the ancient lakes size. It is in this part of Bed
II that the development of the Acheulian industry starts
to show. Here also are the remains of Homo Habilis, Homo
Erectus and Australopithecus Boisei.
The gorge was modified by
fault shifting and erosion. It is after these geographical
changes that Beds III and IV were created. These two Beds
range from 1,150,00 to 600,000 years ago. These two Beds
are separable only in the eastern part of the gorge and
are combined elsewhere into a single unit. They have a maximum
thickness of about 98 feet and consists mainly of sediment
from streams that fed Olduvai Lake.
During a period of major faulting
and volcanism roughly 400,000 to 600,000 years ago, the
Masek Beds accumulated. They are up to 82 ft. thick and
again contain mostly stream sediments with some aeolian
(wind-worked) tuff. It is assumed the climate at this time
was probably much like today based on the deposits found
there. There is only one major archaeological site found
in these beds and it is of the Acheulian tool industry.
The Ndutu Beds were formed
by faulting, erosion and the filling of the gorge around
32,000 years ago. It consists mainly of aeolian tuff. In
this Bed two sites have been found which date to the Middle
Stone Age.
The last of the archaeological
Beds is the Naisiusiu. It lays in the bottom of the Gorge
at what is now the present depth. It only has a depth of
33 ft and also consists of aeolian tuff. It contains one
site that has microlithic tools and one complete Homo Sapien
skeleton, both of which date to 17,000 years ago.
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