Towards the inversion of tectonic signals from deep-marine archives:Competing tectonic signal propagation from across the Alps into the marine sink

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The sedimentary fill of peri-orogenic basins is a product of the interplay between tectonics, climate, sediment transport, and transient storage processes. In turn, sediment archives are often used to reconstruct past tectonic activity and mountain building over various time scales. However, our ability to quantitatively assess how changes in tectonic exhumation influence terrestrial erosion and sediment budgets, and how and at what rate these signals propagate through sediment-routing systems into the marine archives is severely limited. Moreover, these signals may be modified, dampened or even destroyed along their travel paths. Hence, we need to quantify the travel times of tectonic signals into the stratigraphic record and the imprint of these signals on the resulting stratigraphy. This is important to interpret sedimentary archives correctly and to ultimately invert these archives to the upland control factors that shaped these sedimentary successions. A key area to investigate such signals is the Northern Alpine Foreland Basin due to the large amount of available data in the Alpine source area and its foreland. Three major tectonic exhumation and uplift events occur during the late Oligocene to middle Miocene in the Alps: the exhumation of Penninic units in the Lepontine Dome and the Tauern Window, and the uplift of paleosurfaces in the Northern Calcareous Alps. Each of these tectonic events is characterized with a unique sediment-provenance signature that allows us to estimate how and at what rate these tectonic signals propagate into Late Oligocene to Miocene sediments and how they are manifested in the sedimentary sink. The sedimentary successions in the Upper Austrian Molasse Basin were investigated using a large 3D seismic-reflection cube (3300 km2). We recently established a new biostratigraphic and chemostratigraphic framework based on foraminifers, nanofossils and ∂13C. We sampled sediment core and outcrop for heavy mineral extraction. Moreover, we calculated spatially averaged sedimentation rates using the new geochronologic control and sediment volumes. We propose to analyze the sediment archives for the unique tectonic exhumation and uplift signatures using heavy mineral-assemblage analyses and apatite thermochronology (U-Pb, AFT, AHe), apatite geochemistry, and Nd and Sm isotopic composition of apatite and mudstone. We will determine lag times between the individual exhumation and uplift events in the Alps and the arrival of its sedimentary response in the basin. Our results will quantify sediment volumes exported to the Upper Austrian Molasse and determine travel time and mode of distinct tectonic exhumation and uplift signals into the adjacent sediment archives. The quantification of the travel times and the expression of these tectonic signals in the deep-marine stratigraphic record are crucial in our strive to correctly interpret sediment archives and to ultimately be able to invert these records into their upland forcings.