Up-Scaling Field Observations to Ground Truth Seismic Interpretations and Test Dynamic Models of Deep Water Rifted Margins: What are the Challenges?

Abstract:

Recent advances on the study of rifted margins resulted from the development of new, high-resolution seismic imaging methods and dynamic modelling that enable to image the crustal scale structure of rifted margins and experiment under what conditions they formed. However, both the used parameter space as well as the seismic interpretations and model results need to be ground truth by direct observations and data. In the case of deep-water rifted margins, the problem is that drill hole data is expensive, rare and only available from a handful of examples worldwide. In contrast, remnants preserving kilometre-scale outcrops of former deep-water rifted margins have been described from the Alps and the Pyrenees in Western Europe. These large-scale outcrops provide a direct access to mantle and crustal rocks and the associated sedimentary sequences and magmatic additions. The combination of world-class outcrops, classical, field-based mapping and analytical methods can provide the missing data that is necessary to calibrate and test dynamic models as well as to ground truth seismic interpretations. In my presentation I will use observations and data from key outcrops from the most distal fossil Alpine Tethys margins exposed in SE Switzerland with the aim to describe the deformation processes and conditions during final rifting and to test rift modes (semi-ductile flow vs. brittle poly-phase faulting). I will in particular focus on the way strain is distributed and the bulk rheology evolves during hyper-extension and mantle exhumation and compare the observations with model results and seismic interpretations. Up-and down scaling observations/data and bridging multiple spatial and temporal scales is a key to understand the large-scale extensional processes that are at the origin of the formation of hyper-extend and exhumed mantle domains. The major challenge is to understand how the learnings obtained from the well-documented examples in the Alps and Pyrenees can be used to test and ground truth models and interpretations of yet undrilled deep water rifted margins. Combining outcrop scale observations and modelling results and seismic interpretations will enable to develop more coherent geologically meaningful models and interpretations describing the structural evolution of deep water rifted margins.