Abstract The outer parts of collision mountain belts are commonly represented by fold and thrust belts. Many of the key concepts in the structural geology of fold and thrust belts have origins in ancient orogens such as the Appalachians and Caledonian chains of Europe, together with the Alps. Impetus in thrust belt research then came from the desire to exploit geological resources that reside in the subsurface, especially arising from hydrocarbon exploration in the foothills of the Canadian Cordillera in the 1960s and 1970s. Notwithstanding decades of exploitation, continental fold and thrust belts are still estimated to hold reserves of 700 billion barrels of oil equivalent. But exploration will focus increasingly on small, hard-to-resolve structures. Basic geological understanding remains as important today as it did for the pioneering explorers in the Canadian foothills. It is a theme that runs throughout this Special Publication.

Abstract The tectonic framework of NW Himalaya is different from that of the central Himalaya with respect to the position of the Main Central Thrust and Higher Himalayan Crystalline and the Lesser and Sub Himalayan structures. The former is characterized by thick-skinned tectonics, whereas the thin-skinned model explains the tectonic evolution of the central Himalaya. The boundary between the two segments of Himalaya is recognized along the Ropar–Manali lineament fault zone. The normal convergence rate within the Himalaya decreases from c. 18 mm a −1 in the central to c. 15 mm a −1 in the NW segments. In the last 800 years of historical accounts of large earthquakes of magnitude M w ≥ 7, there are seven earthquakes clustered in the central Himalaya, whereas three reported earthquakes are widely separated in the NW Himalaya. The earthquakes in central Himalaya are inferred as occurring over the plate boundary fault, the Main Himalayan Thrust. The wedge thrust earthquakes in NW Himalaya originate over the faults on the hanging wall of the Main Himalayan Thrust. Palaeoseismic evidence recorded on the Himalayan front suggests the occurrence of giant earthquakes in the central Himalaya. The lack of such an event reported in the NW Himalaya may be due to oblique convergence.

ABSTRACT For the first time, modern seismic reflection data along with gravity and magnetic data were used to image the structure of a fold-and-thrust belt overlying the SW margin of the East European craton in SE Poland. These data demonstrate that the Variscan orogen extends eastward much farther than previously believed and terminates against the East European craton basement slope. The structural setting of this newly documented eastern extension of the Variscan fold-and-thrust belt in SE Poland is comparable to that of the Alleghanian orogen emplaced on the margin of the North American craton. Variscan deformation documented in SE Poland is more intense than anywhere else beneath the Permian–Mesozoic German-Polish Basin east of the Harz Mountains, probably because of buttressing by the relatively shallow basement of the East European craton. Our study focused on two regional tectonic units: (1) the Radom-Kraśnik block, a NW-SE–elongated structural high where early Paleozoic to Devonian strata subcrop beneath the Permian–Mesozoic cover, and (2) the Lublin Basin, a major Paleozoic sedimentary basin developed above the SW slope of the East European craton. The seismic data image the Radom-Kraśnik block as a thin-skinned fold-and-thrust belt with a 10–12-km-thick pile of Ediacaran (?) to Devonian sediments tectonically emplaced on the margin of the East European craton. These sediments are involved in a NNE-vergent stack of thrust units striking oblique to the East European craton margin slope. Individual thrusts branch off from a basal detachment that is located in the basal part of Ediacaran sediments unconformably overlying the East European craton crystalline basement. The frontal part of the Radom-Kraśnik fold-and-thrust belt is a triangle zone related to the jump of the basal detachment from the intra-Ediacaran position to the base of the Silurian shales. The base-Silurian detachment continues under the gently folded Lublin Basin and emerges along the Kock fault zone, which is a thin-skinned ramp placed over a basement step at depth. The Kock fault zone could be considered an analogue to the so-called mushwad structures described within the frontal part of the Appalachians.