The Alpstein in three dimensions: fold-and-thrust belt visualization in the Helvetic zone, eastern Switzerland

Abstract

To investigate the geometrical relationships between folding and thrust faulting, we built a 3D geological model of the Helvetic fold-and-thrust belt in eastern Switzerland from several existing and two newly drawn cross-sections in the Säntis area. We partly redrew existing cross-sections and validated them by checking for line length balance; to fill areas with no data we drew additional cross-sections. The model was built based on surface interpolation of the formation interfaces and thrusts between the cross-sections, which allowed generating eight main surfaces. In addition, we used cave data to validate the final model in depth. The main structural elements in the Säntis area, the Säntis Thrust and the Sax-Schwende Fault, are also implemented in the model. The result is a 3D structural model of the area, which provides an intuitive way for examining a portion of a complex structural nappe. The 3D model highlights the shapes of the main anticlinesyncline pairs and how these fold trains vary laterally in amplitude and wavelength. It shows how lateral variations in fold style correlate with regional shortening gradients as determined from line-length balancing. The model also clearly shows the lateral extension, the trend, and the variation in displacement along the principal faults. The reconstruction of horizons in 3D allows the investigation of cross-sections in any given direction. The 3D model is useful for developing and understanding how the internal nappe structures, namely folds and thrust faults, change along strike due to palaeogeographic and stratigraphic variations. Lateral stratigraphy variations correlate with different deformation responses of the nappe. Changes can occur either abruptly across transverse faults or in a more gradual manner. Keywords Central Alps Á Helvetic nappes Á Säntis Thrust Á 3D modelling Á Line balancing Á Depth validation with cave data Editorial handling: A. G. Milnes.

Kinematics of the Alpenrhein-Bodensee graben system in the Central Alps: Oligocene/Miocene transtension due to formation of the Western Alps arc

“…Graben development is closely associated with NW directed thrusting in the Helvetics as suggested by, in part, mutual crosscutting relations of nappe emplacement and graben‐related striations. N‐S trending vertical strike‐slip faults (e.g., Sax‐Schwende Fault in Figure ) accommodating left‐lateral motion concomitant with nappe imbrication [ Funk et al ., ; Sala et al ., ] is in line with our reasoning that left‐lateral strike‐slip faulting and thrusting were coeval and suggests that the wrench corridor was not confined to the Alpenrhein valley. Direct U‐Pb dating of brittle deformation provided internally consistent ages ranging from 25.3 ± 5.6 Ma to 21.8 ± 3.4 Ma for growth of calcite fibers, which agree well with the structural observations.…”

“…Simplified tectonic map of Alpine nappe stack across Alpenrhein Graben; map modified and simplified from 1:200,000 map of Vorarlberg [ Oberhauser and Rataj , ; Ortner et al ., ; Sala et al ., ; Pomella et al ., ]; refer to Figure for location of map. Nappe contacts west of Alpenrhein Graben are south dipping; geology east of Alpenrhein valley is characterized by large‐wavelength syncline/anticline pair cored by Austroalpine and Helevtic Säntis Nappe; Säntis Nappe shows drastic change in outcrop pattern across Alpenrhein Graben with apparent sinistral offset; note also sinistral faults in vicinity of Alpenrhein Graben (Iller Fault, Ostergunden fault system, Sax‐Schwende Fault); contacts of imbricated Molasse with Säntis Nappe above and undeformed Molasse below are hardly offset.…”

Linking Alpine deformation in the Aar Massif basement and its cover units – the case of the Jungfrau–Eiger mountains (Central Alps, Switzerland)

“…The lithostratigraphic and tectonic studies, which resulted in the reconstruction of this scenario, have been conducted over the course of more than 150 years (e.g., Escher von der Linth, 1839; Baltzer, 1880) and have mainly been focused on a few key regions of this ECM. These mainly include the south and southwest (SW) sectors of the Aar Massif (i.e., Krayenbuhl and Steck, 2009;Herwegh and Pfiffner, 2005;Steck, 1984Steck, , 1968 and the area surrounding the Jungfrau and the Mönch mountains (i.e., Rohr, 1926;Scabell, 1926;Collet and Paréjas, 1931;Günzler-Seifert and Wyss, 1938;Kammer, 1989 and refer-Published by Copernicus Publications on behalf of the European Geosciences Union. 1100 D. Mair et al: Linking Alpine deformation in the Aar Massif basement and its cover units ences therein).…”

Kinematic 3-D Retro-Modeling of an Orogenic Bend in the South Limón Fold-and-Thrust Belt, Eastern Costa Rica: Prediction of the Incremental Internal Strain Distribution

“…The construction of 2-D balanced sections has evolved into a key technique in the analysis of contractional tectonics (e.g., DAHLSTROM 1969DAHLSTROM , 1990COOPER and TRAYNER 1986;DEPAOR 1988;WU et al 2005; TANassumed. The analysis of fold-and-thrust belts in map view (e.g., AFFOLTER and GRATIER 2004) and 3-D (e.g., TANNER et al 2003, SALA et al 2014) also underwent considerable progress in the last decades. A 3-D approach integrates lateral geometric variations obtained from map and depth views into the cross section-based structural restoration (TANNER et al 2003).…”