Trace-element and isotopic compositions of fossilized shark teeth
sampled from Miocene marine sediments of the north Alpine Molasse Basin,
the Vienna Basin, and the Pannonian Basin generally show evidence of
formation in a marine environment under conditions geochemically
equivalent to the open ocean. In contrast, two of eight shark teeth from
the Swiss Upper Marine Molasse locality of La Moliere have extremely low
delta O-18 values (10.3% and 11.3%) and low Sr-87/Sr-86 ratios
(0.707840 and 0.707812) compared to other teeth from this locality
(21.1%,22.4%o and 0.708421-0.708630). The rare earth element (REE)
abundances and patterns from La Moliere not only differ between dentine
and enameloid of the same tooth, but also between different teeth,
supporting variable conditions of diagenesis at this site. However, the
REE patterns of enameloid from the ``exotic'' teeth analyzed for O and
Sr isotopic compositions are similar to those of teeth that have O and
Sr isotopic compositions typical of a marine setting at this site.
Collectively, this suggests that the two ``exotic'' teeth were formed
while the sharks frequented a freshwater environment with very low
O-18-content and Sr isotopic composition controlled by Mesozoic
calcareous rocks. This is consistent with a paleogeography of
high-elevation (similar to 2300 m) Miocene Alps adjacent to a marginal
sea.