Abstract A series of analogue models were run to investigate oblique inversion of pre-existing grabens when overprinted by later shortening and the effect of these grabens on development of contractional structures. Obliquity angle ( α ) defining the initial trend of pre-existing grabens relative to the shortening direction, was systematically changed from 0°, 10°, 20°, 30°, 40°, 50°, 65° and 90°. Different structural styles are shown in different models and also in sections cutting across different parts of the models. Model results show that existence of multi-grabens enhances lateral discontinuity of overprinted thrusts in map view. With increasing the obliquity angle, more and longer lateral ramps developed sub-parallel to the graben trends. The pre-existing grabens were apparently rotated from their initial trends during shortening. Some of the normal faults bounding the grabens were partially inverted and resulted in bulging of the syn- and post-rift graben fill sediments. Most normal faults were displaced and rotated by thrusting, and provided relatively weak zones for propagation of thrusts. By comparing with observations from Qingxi graben in western China and from the SW Taiwan fold-and-thrust belt, where oblique inversion occurred, model results can be used to interpret unclear relationships between thrusts and pre-existing extensional structures during superimposed deformation.

Abstract The Mesozoic of Nuevo Leon is composed of more than 10,000 m of sedimentary rocks displaying abrupt physical changes and containing abundant planktonic foraminifera, allowing precise chronostrati-graphic determinations. This succession has been deposited in the western extension of the ancestral Gulf of Mexico (Mexican Sea). Its paleogeographic setting corresponds to the oblique subduction of the Kula-Far-allon plate under the North American plate. Active oblique subduction of the western margin of Mexico has resulted in the structural features of the Mesozoic sedimentary cover, forming a folded belt made of an intricate array of mountain ranges corresponding to the Nuevo Leones Cordillera characterized by: (1) kilomet-ric-scale anticlinal ridges and narrow synclinal valleys of the Jurassic-Cretaceous sedimentary cover commonly displaying box (fan-shaped) folds; (2) a well-developed pattern of en echelon anticlinal folds; (3) juxtaposition of tectonostratigraphic domains; (4) asymmetrical, overturned, doubly plunging anticlines evolving into faulted anticlines; (5) disrupted, long and sinuous fold trends; (6) lack of large horizontal displacement due to overthrusting; (7) folding being predominant over faulting; (8) local thrusting with opposite vergence; and (9) lack of volcanism and regional metamorphism. Those features are the result of transpressional tectonics since the mid-Jurassic including a greater basement involvement in the tectonic deformation. Analysis of the megastructures exposed in the region using SIR-A and LANDSAT imagery of northeast Mexico revealed that the megastructures of the Mesozoic Cordillera between parallels 22°00' and 26°00' and meridians 99° 00’ and 101°00’ can be referred to deformation of the thin sedimentary cover above transcurrent faults following the morphological pattern of the lab experiment by Odonne and Vialon. The folding styles of the Nuevo Leones Cordillera were analyzed in light of tectonic transpression and wrench-fault tectonics driven by transcurrent faults in the basement as established by Harland, Lowell, and Beck, resulting in the recognition of subsurface faults in the basement. We associate the geometric arrangement of the megastructural trends to sense of displacement of strike-slip (transcurrent) faults and fold patterns as demonstrated by Odonne and Vialon (1983) and the well-known strike-slip tectonic setting of New Zealand as described by Bishop (1967).