>Sea water is much heavier than fresh water and may penetrate the deeper
>parts of the Congo river estuary way inland.

Yes, but at low tide the river will flow and terebrids will not stand
this. At all times there will be fresh water coming in and mixing, so
the water willl never be marine.
>
>The shells may be Pleistocene
>fossils too. At times sea level has been much higher than today.

Subfossils, if not very old. Such relicts occur off New Zealand's SE
coast. Never even buried, some of them.
--
Andrew Grebneff
Dunedin, New Zealand
64 (3) 473-8863
<[log in to unmask]>
Fossil preparator
Seashell, Macintosh & VW/Toyota van nut
I want your sinistral gastropods!
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Q: Because it reverses the logical flow of conversation.
A: Why is top posting frowned upon?