Click on the stratum key at right for more information about each stratum.
This card provides you with information on the stratigraphy of Site FLK NN at Olduvai Gorge. You may get more specific information on each stratum by clicking on that stratum's symbol in the key to the right of the drawing. There is only one profile drawing for this site.
Profile Drawings - FLK NN Site Model
The surface scree at site FLK NN consists of loose soil and gravels deposited and reworked by wind and water in recent history.
This over burden reached a maximum thickness of 10-12 feet in Trench II. The upper parts of the tuff consisted of wind-blown tuff. The lower portion, however, contained pockets and channels filled with gravel and blackish sand. Some intrusive fossil bones and artifacts were recovered from these channels, having been deposited there by erosion.
Tuff Id in this locality is a massive member, consisting of purely trachytic tuff. This tuff has been dated using the K-Ar technique in other areas of the Gorge, but not at this site. Tuffs closer to the occupation surfaces have been dated here.
This is a tripartite member containing interbedded deposits of tuff and clay. It is probably the result of lake margin transgression and regression cross-bedding tuffs and clays.
This is a very hard, white colored tuff and ash layer that immediately overlies the green clay Zinjanthropus age occupation floor. It consists of anorthoclase tuff, and has been K-Ar dated to 1.78 million years before present. Sample number KA-850.
This level consisted of a greenish grey silty clay that contained many tabular and irregular limestone chunks. The upper part of the level was irregular and much more friable than the lower part, indicating that it had been exposed to weathering for some period of time before being covered. A number of fossil bones of antelope, suids, equids and tortoise were recovered along with a small quantity of stone tools. Only five tools were recovered, and of the obviously human modified material, only two waste flakes were noted. Thus even though this level is contemporaneaous with the Zinjanthropus (A. boisei ) occupation floor from Site FLK I, there does not appear to have been any substantial hominid activity here during the time that this clay was being deposited.
Level 2 consisted of a very fine-grained, buff-white tuff. In some areas the base and central parts of the tuff tended to be clayey, and it was in these pockets that the majority of the fossil bones recovered from this level were found. The remains of larger mammals were remarkably more complete than in either Levels 1 or 3. There were fewer broken bones, and more completely articulated skeletons in this level than the other levels. No artifacts were recovered from this level. It appears that this level was deposited during a period when no hominids were occupying this portion of the basin, and provides a clear demarcation between the deposits of Levels 1 and 3.
Level 3 consisted of a silty clay of a light grey color. The stratum contained some inclusions of nodular and tabular limestone, but not so dense as in Level 1. This level varied in thickness from 6 inches to 2 feet and filled pockets in the upper surface of of Tuff Ib, which contained impressions of root casts and reed stalks in it. This level contained the majority of the hominid remains found at this locality as well as the majority of the stone tools. Almost all of the cultural materials recovered from this level were either on the surface of the clay, or were within the upper few inches of it. Pockets of fish and amphibian bone found in the middle portions of the layer indicate that the lake may have receded, providing a dry surface for occupation along the lake margin. By comparison with the wealth of material from Site FLK I, the main occupation zone of this site either suffered more postdepositional erosion, or was occupied for a much shorter period of time. The hominid remains from this stratum have been assigned to Homo habilis (fragmentary cranium, mandible, clavicle, hand and foot bones).
Tuff Ib seals the occupation layers of Levels 1, 2, and 3 from the lower, non-culture bearing deposits from the site. This stratum is the same Tuff Ib that seals the lower deposits at Site DK, and thus places the FLK NN cultural deposits later in time than the DK cultural deposits. This tuff was dated to 1.64 million years B.P. using K-Ar techniques at Site FLK I. Although this is a younger date that the one obtained from the hard white-buff tuff above Level 1, the range of error between the two dates overlaps. Thus, the deposits from Levels 1-3 at this site must date in the range 1.75 million years ago.
This was a thick bed of green colored clays. No cultural materials were recovered. Faunal remains consist primarily of bird bones. Area may have been a nesting area for migratory waterfowl during this time.
A non-culture bearing sandy tuff zone. Partially weathered.
This was a zone of green, silty clays, indicating very slow water movement. No cultural debris or hominid fossils.
This was a very fine-grained tuff with a buff to yellow color. It did not contain any cultural debris or hominid fossils.
This stratum consisted of a very sandy silt, indicating alternating water and wind deposition. The deposit had numerous rootlet casts in its upper surface. This stratum probably records a period of lake transgression and regression. No cultural debris or hominid fossils were recovered from this stratum.
This layer consisted of a brown to grey colored tuff. It was devoid of hominid fossils or cultural debris.
This was a very hard, white colored tuff sealing the clay deposits below it. There were no cultural remains found in this level.
This stratum consisted of a grey to green colored silty clay, sealed by the tuff above, and abutting the basement basalt deposit to the southeast. Curturally sterile.
This was a very thin tuff deposit of no apparent consequence. Culturally sterile.
This was a culturally sterile clay deposit overlaying the basement basalt.
This basalt member forms the bottom of the observable deposits at Site FLK NN. It consists of very ancient flows from the Ngorongoro volcano that underlay all of the Olduvai deposits and from the very bottom of Bed I.