Potentially astronomically forced climate sensitivity of Lake Pannon during the Tortonian Thermal Maximum (Late Miocene, Vienna Basin, Austria)

We present XRF-based element data and magnetic susceptibility measurements of a 60-m-long core of Upper Miocene deposits of Lake Pannon from the Vienna Basin (Austria). The deposits formed during the Tortonian Thermal Maximum, which was a global warming event during the Late Miocene. Statistically significant cyclicities occur in all records centering around -22 m, -12 m, -10 m, -7.2 m and -1.5 m. The modulation of the -12-m-cycle is strikingly similar to that of the precession band between 10.45 and 10.34 Ma and is used herein as hypothetical tie point for tuning. Consequently, the -22-m-cycle is interpreted as an expression of the obliquity cycle. This hypothetical correlation lacks a tie point by absolute dating but is supported by the resulting sedimentation rate of 0.53 m/kyr, which is well in the range of published data. Moreover, the expected phase relations between the assumed precession and obliquity signals fit excellently with the observed paleoenvironmental data. Obliquity is reflected by changes in sediment input and lake level oscillations. Obliquity maxima coincided with increased input of coarser sediment and enhanced lake bottom oxygenation, whereas pelitic sedimentation and lake bottom anoxia prevailed during obliquity minima. Precession is reflected by shifts in precipitation. Maxima in lake productivity, indicated by phytoplankton blooms and a high abundance of ostracods, occurred during precession minima. The striking cyclicity in the Ca/Ti and Rb/Sr ratios suggests a periodic interplay of two source areas. Increased runoff from the Calcareous Alps, drained via the Paleo-Liesing river, occurred during precession minima, whereas siliciclastic input from the Rhenodanubian Flysch Unit via the Paleo-Wien river prevailed during precession maxima. The maximum of freshwater influx occurred during an obliquity maximum coinciding with a precession minimum, which agrees with model data and other geological records in the Circum-Mediterranean region. The shortest cycle potentially represents the Hallstatt cycle, which was already detected in other records of Lake Pannon and is a further anchor to link sub-Milankovitch cycles with astronomical cycles in Lake Pannon deposits.