FISH IN THE TENERE (NIGER)
This is a discussion, and you are asked to add your knowledge and views through info@desertdiningclub.or.uk

David and Lillis Lyon visited the Air and the Ténéré in 2004, and took photographs of fossilised fish bones in the lake.  His report records: "Lake of T-I-n Ouaffadene [N 2o 10 140  :  E 9  10  571] with its little hill to the west clearly visible on the otherwise flat horizon from 30 km away.  The dried up lake is about 500m in diameter and has number of calcareous deposits of varying thickness within it.  There are numerous pieces of skeleton in the deposits and the sand bed of the lake including fish skeletons. At the margins of the lake are calcified ferns."


Click on photo to enlarge

Fish bones.  What sort of fish?

More fish bones.  What species?

Photo of the 'calcified ferns' on the lake margins.

David Hall, at first sight thought the picture on the left showed a camel skeleton, but later wondered if the fish was a cat fish.  Dr David Thomas (member of the Club) said: "My first reaction as a zoologist to your photo was that the vertebrae look very fish-like: simple "cotton reels" (albeit with attenuated waists) abutting end-to-end and pretty undifferentiated one from another.  Such structures work very well for swimming fish, all of whose weight is supported by the water: the vertebral column has mainly to resist longitudinal compression resulting from trunk muscle contractions, and allow the body to flex laterally during swimming.  Terrestrial vertebrates (whose vertebral columns now have to support body weight as well as flexing with locomotion) typically have adjacent vertebrae with bony processes interlocking & articulating with one another to maintain the integrity of vertebral column axis under loads which aren't parallel with the axis.  Vertebrae of terrestrial vertebrates also have dorsal and lateral processes for muscle attachment (see any sheep skeleton next time you walk in the hills).  When you get to something the size of camels, the loads are large and these various bony processes on the vertebrae are correspondingly well developed."  

The late Professor J Desmond Clark talked of the 'Old Neolithic' hunters and fishers around the swamps had a diet which included Nile perch and mudfish.  (in Geogr. J. 137,4456).

What are the fish?  Are they cat fish, Nile perch or 'mudfish'?
How big have been the fish found in the Ténéré?
What of the calcified ferns?

COMMENTS WELCOMED TO info@desertdiningclub.org.uk

RESPONSES:
1.  Mike Saunders, Deputy Leader of the British Expedition to the Air Mountains 1970, writes: "I remember going to the lake (Lake of T-I-n Ouaffadene) by the cimetiere des Addax, and helping to lift a complete fossilised fish, looking like, and said by the cognoscenti to be, a catfish.  It was complete, embedded in a matrix of diatomite so that you could see all of one side of it, and it was about 18 inches long.  I seem to remember that it came from near the top of the steep bank, the top of which was said to mark the lake shore line.  There were also many, many snail shells there, I think mainly the long thin conical sort about 1/2 inch long.  The Latin name escapes me, but they were like the snails which were found in slow moving water  and which are vectors for the schistomsome parasite.  We did not see live addax, but saw plenty of addax skeletons.  (Received 27 December 2006)


2.  Professor Martin A J Williams, geographer, geomorphologist, Quaternary geologist, and Foundation Professor of Envirnmental Studies, University of Adelaide.  As a member of the British Expedition to the Air Mountains 1970, he, with the late Professor J Desmond Clark (Berkeley) and Professor Andy Smith (Cape Town), spent three months working at Adrar Bous and the area to the south of it.  He comments:

We paid two brief visits to Tin Ouaffedene, an isolated flat-topped hill of greywacke sandstone and quartzite located ~30 km SE of Adrar Bous.  On some of the older small-scale maps it appears as 'Piton Isolé' or as 'Cimetière des Addax'.  We gave it the informal name of 'Piton Faure' in honour of the geological research conducted in this region by Professor Hugues Faure.  On later 1: 100 000 scale maps it appears as Tin Ouaffedene which appears to be its correct local name.

Click on photo to enlarge

Piton Isolé, Cimetière des Addax, or Piton Faure

Diatomite on the ancient lake bed.   Pictures by David Lyon (2004)

The hill is surrounded by a peripheral wind-scoured depression or deflation hollow ~30 m deep.  Wind-eroded remnants of diatomite crop out on the floor of the depression and to heights of 15 m above the floor of the depression.  The approximate elevation of the top of the diatomite is 655 m. A well-defined break of slope at 670 m probably marks the upper limit of the lake.  Beneath the break of slope there is a small scarp comprising 30 cm of grey-brown vesicular clay loam over 60 cm of massive brown sandy loam.  The vesicular clay loam grades into a vesicular ferricrete.  We recovered fish bones and shells from one
section (section A of 7/2/70) 2-3 m beneath the uppermost diatomite surface.  From the top down, section A comprised 3 cm of diatomite with fish bones over 22 cm of grey medium sand with shells over 20 cm of white silt with very fine charcoal over a further layer of diatomite.  Two shell samples were collected for radiocarbon dating and yielded statistically identical ages of 9 570±130 BP (SUA-2718) and 9 610±230 BP (SUA-2719).  The dates were subsequently confirmed by ages of 9220 and 9260 BP reported by Roset et al. (1990).  [They are also statistically identical to ages of 9130, 9100 and 9030 BP from Diatomite I at Adrar Bous].  These ages indicate that the uppermost diatomite at this site was coeval with the highest levels attained by Lake Chad during the Holocene (Servant 1973, Servant and Servant-Vildary 1980).  Considerably more detail is now available from this site as a result of the PALHYDAF drilling project. Fontes and Gasse (1991) provided an excellent summary of this work and Dubar
(1984) has given a detailed analysis of the diatoms with some additional radiocarbon dates similar to ours.

The Piton Faure radiocarbon dates obtained by me are:
SUA-2719 : 9, 610 +/- 230 years BP
SUA-2718: 9, 570+/- 130 years BP
These are radiocarbon years and not calendar years.

Key references:
Williams, M.A.J., Abell, P.I. and Sparks, B.W. (1987). Quaternary landforms,
sediments, depositional environments and gastropod isotope ratios at Adrar Bous,
Tenere Desert of Niger, south-central Sahara. In: Frostick, L. and Reid, I.
(eds) Desert Sediments: Ancient and Modern. Geological Society Special
Publication No. 35, pp. 105-125.

Dubar, C. (1984) Eléments de Paléohydrologie de l'Afrique Saharienne: les dépôts
quaternaires d'origine aquatique du Nord-Est de l'Aïr (Niger, PALHYDAF site 3).
Docteur en Sciences thesis, Université Paris-Sud, Centre d'Orsay, 170 pp.