21 July, 2008

Modern and ancient beaches?

Another example of geology I saw while travelling through Romania is situated in Costinesti at the Black Sea. Also there is a lagoonal lake north at Eforie I think. Anyways, walking northward on the beach from Costinesti into the direction of the big shipwreck and passing it for about 200m one will enter the realm of seashells. The entire beach is entirely composed of nothing but shells of mussels (mainly Mytilus sp. I think) and snails!

Now compare the above image to this one:

Here is an enlarged view and sample of this rock type:

Noticably the entire rock is composed only of shells and their fragments and as I found out back at home also tiny nodules that I think are pellets. I wonder if it would be correctly classified as a Bio(pel)sparudite (it is hard to say if it is micrite or sparite without a thin section) or Grainstain or Packstone. It's definitly a limestone though. It fizzes like crazy. I assume we are locking at a modern and ancient example of very similar if not identical depositional environments where a lot of shells are washed together with some pelletal grains. On second thought the pellets might also be later formations of micrite. They are really tiny.

A shame I do not know anything about the coastal geology of Romania but I like to think of the above foto as modern and ancient examples united right next to each other. If I should be mistaken feel free to correct me. Perhaps Zoltan or one of our sedimentologists can shed some light on this?

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