THE LEGEND OF THE 7 LAKES: EPISODE 1- The Legend

March 14, 2009 at 09:20 | Posted in 7 lakes, geology, Nigeria, UNN | 5 Comments
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It all began with my first visit to a University hall of residence and Study centre for students with a funny name: Uhere. ‘What kind of name is that?’ I asked. I was told that it is the local dialect’s word for wind. I was also told that the centre is named after a river somewhere around. That was in my first undergraduate year (2003). A year later, I became a resident at the center and we one day had a get-together with a lecturer from the department of tourism at the university. He told us, among many other things, about some tourist locations in Enugu state and mentioned Uhere River and The seven lakes of Opi. I was a bit skeptical about their existence, with ‘geological’ reasons for my doubt. The Nsukka area sits on the late cretaceous (Maastrichian) Ajali Sandstone formation (a.k.a false-bedded sandstone), consisting of characteristically friable cross-bedded sandstones. Ajali formation is also a good aquifer, supplying water to the areas around Nsukka all the way down to Enugu (city) area and even Okigwe. In Nsukka the groundwater level is deep (more than 100m on average) and if it is the same in Opi which is close to Nsukka (about 10 km to the southwest), how would the lakes be able to hold water on such a porous and permeable formation?

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  1. I think you’ve got somethings wrong….the Nsukka town sits on top of the Nsukka Formation which in turn is overlying the falsebedded Ajali Formation with the Mamu Formation underlying Ajali Formation.
    As you know, the Mamu comprises less porous sediments (shale, shaly siltstones and interbedded oolitic ironstone beds) unlike the Ajali Formation.

    Now, the Opi area sits at the scarp face of the Enugu Cuesta and exposes thick sand successions of the Ajali along canyon like faces (like we both saw on our first adventurous trip to find the lakes) probably as a result of erosion aided by the steep topography of the area. However, the Mamu is not exposed at this very particular area but at Eha alumona, some 8 – 10 kilometers north of Opi), the Mamu is exposed at the base of thick sand successions of the Ajali.

    If you remember vividly how far we descended before we got to River Uhere then u’ll agree with me that it would naturally have surpassed the 100 meter depth (when checked vertically down from Opi town to the river) and if that is so then the Mamu Formation would obviously be very close to the surface at the area where we saw the river and where the lakes are situated. That said, it is possible that these lakes as well as River Uhere are marking the contact between the Ajali and the Mamu Formations and are being supplied frequently with water as a result of the canyon like topography of the area making run – off from the cliffs as well as the infiltration of water through the very porous Ajali Formation principal processes.

    However, I think we should go back there and see the rest of the lakes. I have being privileged to see three.

  2. […] THE LEGEND OF THE 7 LAKES: EPISODE 2- The Excursions July 18, 2009 at 12:37 | In 7 lakes, Nigeria, Uhere, petroleum | Leave a Comment Tags: enugu, Nigeria, opi, Uhere This is the second of installment of my encounter with the lakes of Opi in Enugu state. For the first part of the series see here. […]

  3. […] the third post in the series on the lakes of Opi, Enugu state, Nigeria. Previous posts can be found here and […]

  4. Interesting writes…I was fink lotsgeoconsult has a good explanation anyways…fundermentally, the lake sits on a less-permeable formation hence its ability to hold the lake water, even if we find ajali sands bedding the lake, it might just suggest that the formation is thoroughly soaked in that area by the voluminous confined water and would have sunk down the porous sands but has been otherwise held in place by an underlying mamu formation.

  5. nsukka formation is overlain by ajali sand stone which are both campanian maastrichtian in age


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