Early Kimmeridgian radiolarian fauna from the Sillenkopf Formation near Kronalalm and its evidence for the Late Jurassic geodynamic history of the Eastern Alps (Northern Calcareous Alps, Steinernes Meer, Germany)

Forty-eight well-preserved radiolarian species/morphotypes are reported from a siliceous limestone of
the Kronalalm section in the Berchtesgaden National Park (Northern Calcareous Alps, Germany), which
elucidated an early Kimmeridgian age. The siliceous limestone is attributed to the Oxfordian–Tithonian
Sillenkopf Formation of the upper part of the Ruhpolding Radiolarite Group in the Tirolic Nappe system.
Facies comparisons of this Sillenkopf Formation outcrop are made 1) with the more basin-ward deposited

type sections of the Sillenkopf Formation and 2) with adjacent sections to the south, where an Oxfordian-
Kimmeridgian basinal facies is missing due to intra-Upper Jurassic erosion. In those sections to the

south, upper Kimmeridgian–Tithonian bituminous carbonates with intercalated polymictic mass-transport
deposits and bioclastic debris (Ledererkar Formation) were deposited in a slope-basin above an erosional
unconformity, directly on top of Lower Jurassic condensed red limestones. Our findings clearly evidence
a today not anymore existing Late Jurassic carbonate platform south of today’s Northern Calcareous Alps,
which shed its material northward into the Sillenkopf Basin.