pdf: http://pages.unibas.ch/earth....023.pdf

The Kimmeridgian shallow-water carbonates of the Swiss Jura Mountains display stratigraphic levels containing mass accumulations
of nerineoidean gastropods. The macro- and microfacies of the rocks with these nerineoidean assemblages suggest that their occurrence
was related to water depth, physical energy within the habitat, sedimentation rate, substrate stability, and food supply. Typical nerineoidean shells are high spired and exhibit unique spiral laminae (folds) on the internal walls. Mass accumulations consisting of large,
heavy individuals are believed to represent a semisessile, suspensionfeeding community that utilized an external food source. During
times of enhanced precipitation and run-off from the hinterland, terrestrial organic matter may have been supplied into the shallow sea,
thus forming a source of food for the nerineoids. Alternatively, relative sea-level change during transgression may have led to largescale
coastal erosion and flooding of the platform, also potentially leading to a mobilization of organic matter. Size and morphology of
the high-spired shells seem to indicate a trend toward maximal external volume. Development of folds within the shell is interpreted as
a modification to maintain a small internal volume. The faunal and floral composition of the strata indicates a suspension-rich, highenergy
environment with a low-sedimentation rate and a stable substrate. This allowed mass colonization by epifaunal nerineoids, which,
in turn, formed a frameworklike structure. The heavy shells acted as a grid, trapping the sediment in between. In this way, a reinforced
carbonate accumulation formed.