At first sight, the images appear to consist of Benthic foraminifera; it could be Bolivina or Bulimina genus. Although it can't be confirmed more without more accurate information.

Do you have a size?

As said in first post the size is about 500-600 µm long

Other colleagues alsi suggest linings of a biseriate coiled foraminfera.

Some think to genus Textularia.

The question is thus, is it really freshwater deposit as geilogists say ?

Thanks a lot to all for your cooperation

marc