Abstract
We use a databased lithospheric-scale 3D structural model of the Molasse Basin area and the adjacent part of the Alpine orogen to calculate the present-day 3D thermal field of this continental collision zone. With our work we contribute to the understanding of the temperature distribution and the existence of pronounced positive and negative thermal anomalies in the Molasse Basin. We assume conductive heat transport and compare calculated temperatures to measured values and to other published 3D models. Areas where predicted and observed temperatures match closely are interpreted to be dominated by conductive heat transport. For areas, where a poor fit between modelled and observed temperatures has been obtained, we discuss possible reasons of this misfit. In particular, an additional contribution by fluid flow to the heat transport is likely. We conclude that the thermal field is controlled by conduction in the lithospheric mantle and the crystalline crust. Furthermore, we show that the positive and negative thermal anomalies in the Molasse Basin are partly triggered by the structural configuration of the crystalline crust. In particular, the domains of the Tauern Body and the upper part of the Alpine crust on the one hand and the insulating Molasse Basin sediments on the other hand control the shallow thermal field of the Molasse Basin area in response to their contrasting thermal properties. Our results demonstrate that the foreland basin and the adjoining Alps have to be regarded as an interdependent system that needs to be considered adequately if the present-day 3D thermal field of that area is assessed.
Highlights
The North Alpine Foreland BasinThe North Alpine Foreland Basin, known as the European Molasse Basin, is a Tertiary foreland basin situated in the northern front of the European Alps (Fig. 1)
The base of the domain influenced by conductive heat transport is represented by the thermal Lithosphere-Asthenosphere Boundary (LAB), which is defined as the 1300 °C-isotherm
The geothermal gradient is much steeper in areas of a shallower LAB than in areas of a deep LAB (Alps)
Summary
The North Alpine Foreland BasinThe North Alpine Foreland Basin, known as the European Molasse Basin, is a Tertiary foreland basin situated in the northern front of the European Alps (Fig. 1). With the stacking of the Alpine mountains in the course of the collision process significant loads have been imposed onto the colliding tectonic plates, leading to a flexural response of the crystalline crust underlying the Alps and the creation of the wedge-shaped Molasse Basin Today this foredeep is filled with clastic sediments, the Molasse, originating from. Several studies have been conducted using different approaches addressing the temperature distribution in the Molasse Basin (numerical modelling approach: Rühaak et al 2010, interpolation approach: Agemar et al 2014a, b) or the European Alps (Vosteen 2003; Ebbing 2004; Ebbing et al 2006) Studies regarding both the basin and the mountain chain as an interdependent system are either two-dimensional, of local scale, or have an insufficient resolution of geological structures and tectonic elements to reproduce the local to regional temperature variations. It remains open which heat transport processes are acting on a regional scale
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