Is there any significance of lacustrine gastropoda fossils regarding paleoenviroment interpretation?
Shell stable isotopes, for oxygen and carbon reveals, if the gastropoda had lived in brackish, lacustrine or palustrine environment.

For discussion please see paper below.

Latal, C., Piller, W. E., &amp; Harzhauser, M. (2004). Palaeoenvironmental reconstructions by stable isotopes of Middle Miocene gastropods of the Central Paratethys. Palaeogeography, Palaeoclimatology, Palaeoecology, 211(1-2), 157-169.