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Palinspastic Reconstruction Versus Cross-Section Balancing: How Complete Is the Central Taurides Fold-Thrust Belt (Turkey)?

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2018-11-01
McPhee, Peter J.
van Hinsbergen, Douwe J. J.
Maffione, Marco
Altıner, Demir
In many fold-thrust belts, cross section-derived shortening estimates are significantly lower than predicted based on plate convergence. This has led to controversial hypotheses that shortening may be largely underestimated due to wholesale underthrusting (convergence without shortening) below far-traveled continent or ocean-derived nappes. The Late Cretaceous-Eocene Taurides fold-thrust belt (southern Turkey) may contain a highly incomplete shortening record of convergence likely caused by wholesale underthrusting. To estimate this underthrusting, we calculate convergence across the belt using a map-view palinspastic reconstruction that takes into account major rotations of tectonic units during their accretion. We use paleomagnetic and fault kinematic analysis, timing of accretion, and Africa-Eurasia convergence to constrain our reconstruction. Our paleomagnetic results confirm an ~40 degrees clockwise vertical axis rotation of the Geyikda nappe that forms the core of the belt, which we interpret is accommodated by a lateral gradient in underthrusting on faults structurally above and below the Geyikda nappe. We reconstruct ~400-450km of convergence across the Taurides during their accretion. We compare this predicted convergence to shortening calculated from balanced cross sections, in which we reconstruct a minimum of 154-km shortening: 57km within far-traveled nappes, 70-km thrusting of far-traveled nappes over the Geyikda nappe, and 27-km shortening within the Geyikda nappe. Shortening in the Taurides created a significant nappe stack, but the majority of convergence was accommodated by wholesale underthrusting with barely a trace at the surface, including ~160km of convergence by rotation of the belt, and 90-130km related to missing Africa-Eurasia convergence.