Modes of Oblique Inversion: A Case Study From the Cretaceous Fold and Thrust Belt of the Western Transdanubian Range (TR), West Hungary. Issue 3 (4th March 2022)

• Record Type: Journal Article
• Authors: Héja, G.; Ortner, H.; Fodor, L.; Németh, A.; Kövér, S.
• Is Part Of: Tectonics. Volume 41:Issue 3(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-03-04
• Subjects: oblique inversion -- structural inheritance -- Austroalpine orogeny; Geology, Structural -- Periodicals; 551.8
• DOI: 10.1029/2021TC006728
• Languages: English
• ISSNs: 0278-7407

Abstract

Abstract: Inversion of pre‐existing normal faults is a frequent phenomenon in orogenic belts. However, their impact on the evolution of the Cretaceous Eoalpine orogeny is poorly studied, despite the widespread presence of Triassic and Jurassic normal faults. Our study area is the SW part of the Transdanubian Range (TR), which represents the uppermost thick‐skinned nappe of the Eoalpine orogeny in the Alpine realm. The variable trend of Cretaceous contractional structures within the Transdanubian Range has been traditionally explained by poly‐phase shortening. However, based on the combined analyses of field observations and 3D seismic data, we found that the complex geometry of Cretaceous contractional structures can be explained rather by the oblique inversion of segmented Late Triassic grabens. In general, the SW part of the TR can be characterized by N‐S trending contractional structures. NW‐SE striking oblique ramps are nucleated above Late Triassic normal faults, whereas NE‐SW trending folds and thrust with limited strike‐parallel length evolved due to the inversion of pre‐existing breached relay ramps, which connected the segments of Late Triassic normal faults. We determined different types of oblique ramps, incuding normal faults, which suffered transpressional reactivation, oblique hanging wall breakthrough thrusts, oblique footwall short‐cut and hanging wall by‐pass thrusts. Only very steep normal faults, or those that strike at low angle to the regional E‐W shortening direction, were not reactivated. Key Points: The oblique ramps of the study area formed due to the oblique inversion of a rift related graben‐system During inversion, those pre‐existing normal faults were reactivated, that enclosed a high angle to the direction of shortening Spatial relationship of the inversion related obliqe ramps and the earlier normal faults led us to define four styles of oblique inversion