AAPG Middle East Geoscience Technology Workshop, Integrated Emerging Exploration Concepts

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A New Look at Structural Concepts and Modelling to Inform Exploration


Conceptual models of fold-thrust belts inform the drawing of cross-sections and the creation of 3D models. These conceptual models are based on named 'end-members' such as fault-propagation fold, detachment fold, fault-bend fold and trishear. These end-member models are really useful for filling unconstrained space in cross-sections with geologically reasonable geometries and building understanding at regional scale. Each named end-member model is based on a theoretical understanding of how the fold-thrust pair forms. The original models are based on simple geometric principals, these were also easy to programme into initial cross-section construction and section balancing software (see Groshong et al. 2006 and 2012 for reviews). It wasn’t until the advent of trishear (Erslev, 1991) that numerical, rather than geometrical, models were applied to fold-thrust belts to inform understanding. As software packages developed into fully 3D environments the structural restoration and balancing algorithms based on the end-member concepts were morphed into pseudo-3D balancing and restoration packages that assumed never ending lateral continuity. Geomechanical and pseudo-geomechanical 3D solutions were also created to address such issues, albeit at high expense to run. But where are we today? Despite acknowledgement that many of these end-member solutions do not fit our knowledge of how fold-thrust belts deform (Torvela and Bond, 2012; Butler et al. 2018 and 2019) we are still in a situation where these models dominate thinking consciously and sub-consciously. This is partly because we have not managed to develop models or concepts that better represent known complexities and are not able to make predictions as we do not have the detailed understanding of what controls these complexities to represent more effectively the heterogeneities seen. We are what psychologists would describe as anchored to our known models. We are looking for solutions in our know solution space, the ‘end-member’ models. This phenomenon is also called the street light effect we are looking where we know we can see and not in the darkness of the unknown. Here I discuss these psychological biases and their impact on everything from the data we collect to the models we propose. I do this with reference to fold-thrust examples from natural rock outcrops to seismic sections and the models we create from them. The aim is to raise awareness of the different structural styles that are present in fold-thrust belts, the controls on their heterogeneities and the true range of lateral continuity.