The continental Hessenreuth Formation: syntectonic deposition during Late Cretaceous inversion (Danubian Cretaceous Group, Bavaria, Germany)

The strata of the Danubian Cretaceous Group reflect dynamic depositional conditions in a peri-continental setting at the northern margin of the Alpine Tethys. From the Middle Turonian onwards, tectonic inversion along the Franconian Lineament started, reflected by the deposition of coarse-grained and extremely immature siliciclastics of the continental, more than 466 m thick Hessenreuth Formation, comprising the mid-Middle Turonian–Middle Coniacian depositional sequences DS Tu 3–Co 2. The composite section studied consists of successions cored by the deep Friedersreuth 10/1990 borehole as well as several shallow boreholes and outcrops. The >63 m thick Glashütte Member below 312 m ASL is characterized by beige-pink, conglomeratic sandstones alternating with thin brick-red, argillaceous-silty soil horizons. The Parkstein Member (312–390 m ASL) is dominated by several-meters-thick, partly inversely graded sandstone packages, interbedded by a few thin carbonaceous silt and clay beds with plant debris. The tripartite Friedersreuth Member (390–562 m ASL) starts with a cyclic conglomeratic-brecciform debris-flow unit, followed by a chaotic mud-flow unit, and is capped by predominantly fine-grained, plant-rich siliciclastics. The uppermost ca. 153 m constitutes the Hesserberg Member, i.e., mica-rich, coarse conglomerates that include meter-scale boulders. These alluvial subunits can be correlated to the mixed marginal marine / continental succession of the Bodenwöhrer Senke, ca. 60 km in the south, and the neritic deposits around Regensburg–Kelheim. Palynoassemblages are dominated by angiosperm pollen of the Normapolles group. Below 515 m ASL, the Turonian marker Complexiopollis christae occurs, while above 555 m ASL, Minorpollis minimus characterizes the Coniacian.