Downloaded from http://sp.lyellcollection.org/ by guest on September 27, 2021 Kinematic evolution and structural styles of fold-and-thrust belts J. POBLET1* & R. J. LISLE2 1Departamento de Geologı´a, Universidad de Oviedo, C/Jesu´s Arias de Velasco s/n, 33005 Oviedo, Spain 2School of Earth and Ocean Sciences, Cardiff University, Park Place, Cardiff CF10 3YE, UK *Corresponding author (e-mail: [email protected]) Abstract: Fold-and-thrust (FAT) belts occur worldwide and have long been the focus of research of structural geologists who have devised a variety of techniques to image, characterize and model their main structural features. This introductory chapter reviews the principal geological features of FAT belts formed in different settings, emphasizing aspects related to their kinematic evolution and structural styles. Despite great advances, challenges remain, particularly in the understanding of the spatial and temporal evolution (4D) of FAT belts and their controlling factors. These research efforts are being assisted by the growing availability to researchers of relatively new tools to collect field data, high quality 3D seismic data, and computer and laboratory modelling tools. This volume includes technical papers presented in the conference ‘International Meeting of Young Researchers in Structural Geology and Tectonics (YORSGET-08)’ held in Oviedo (Spain), together with other papers on the same theme. These papers deal with FAT belts in different parts of the world and cover a broad range of different aspects, from detailed structural analysis of single structures to regional issues, and from studies based on classical field structural geology to modelling. Fold-and-thrust belts, or FAT belts for short, have a The application of classical methods of studying worldwide distribution (see surveys in Nemcok deformation mechanisms in rocks and of quantify- et al. 2005; Cooper 2007), have formed in all eras ing geological strain (e.g. Ramsay 1967; Durney of geological time, and are widely recognized as & Ramsay 1973; Fry 1979a, b) to FAT belts has the most common mode in which the crust accom- led to greater understanding of deformation on a modates shortening. Generations of geologists have small scale and has given insights into the mechan- struggled to understand their origin, geometry, evol- isms responsible for the development of individual ution and the control exerted on them by different structures such as folds and faults. A number of structural, tectonic, stratigraphic and petrological techniques were initially devised to analyze the parameters (see for instance monographic books structure of FAT belts, for example: (a) balanced such as McClay & Price 1981; MacQueen & and restored cross-sections (e.g. Dahlstrom 1969; Leckie 1992; McClay 1992a, 1994; Mitra & Fisher Mitra & Namson 1989); (b) construction of geologi- 1992; Nemcok et al. 2005; Lacombe et al. 2007). cal cross-sections using techniques such as depth to A number of factors have contributed to our detachment estimations (e.g. Chamberlin 1910; greater understanding of the structure of FAT Mitra & Namson 1989) and the Busk and dip belts; some of them derive from detailed analyses domain methods (Busk 1929; Suppe 1985, respect- of prevalent patterns of faulting and folding and ively); and (c) advances in the understanding of their related structural features, whereas others quantitative relationships between thrusts and their come from other earth science disciplines. Many related folds and the rules to help to constrain the important concepts were developed and applied structural geometries (Suppe 1983; Jamison 1987; to FAT belts as early as the 1970s, or even before, Mitra 1990; Suppe & Medwedeff 1990). These tech- and have been subsequently modified. Since a com- niques have enabled construction and validation of prehensive historical review of research progress admissible and retro-deformable geological sections is almost impossible here, only a few important across single structures, structural units and entire landmarks are briefly described, starting with struc- FAT belts. They have also provided guidelines for tural methods from small- to large-scale and seismic interpretation, and proved to be essential following with techniques applied to these regions tools in structural interpretation widely applied else- furnished by related disciplines such as petroleum where, particularly in areas of scarce and/or poor geology, geophysics, geomorphology, petrology quality data. The study of accretionary wedges and sedimentology. played a key role in the development of the From:Poblet,J.&Lisle, R. J. (eds) Kinematic Evolution and Structural Styles of Fold-and-Thrust Belts. Geological Society, London, Special Publications, 349, 1–24. DOI: 10.1144/SP349.1 0305-8719/11/$15.00 # The Geological Society of London 2011. Downloaded from http://sp.lyellcollection.org/ by guest on September 27, 2021 2 J. POBLET & R. J. LISLE Coulomb wedge theory (e.g. Davis et al. 1983; isotopes, magnetostratigraphy, fission tracks, cos- Dahlen et al. 1984). This theory, which incorporates mogenic nuclides, and so on (e.g. Vance & Mu¨ller the best of the gravity-driven v. surface force-driven 2003; Alle`gre 2008; Lisker et al. 2009; Dunai motion hypotheses, was a major step forward in the 2010) have enabled estimates to be derived for understanding of the kinematics and dynamics of both the timing and the short- and long-term rates FAT belts because it allowed the inclusion of the of motion of single structures and larger-scale tec- effects of gravity and topography and provided tonic processes. These have demonstrated, for answers to the problems of structure sequencing in instance, that synchronous movement of different these regions. thrusts is a significant feature in the kinematic evol- The contribution of geophysics has been hugely ution of FAT belts, which, in turn, has important beneficial to FAT belt research. In particular, since implications for thrust sequences and the balancing/ many belts contain major oil and gas accumulations restoration of cross-sections and forward modelling in structural traps, the geophysical explorations of thrust terrains. A great deal of recent research has carried out by the hydrocarbon industry have sup- been focused on the dynamic interaction between plied an enormous amount of subsurface data. FAT belt evolution and surficial processes such as From the early seismic experiments in the late syn-kinematic sedimentation, erosion, uplift and 1920s in the Zagros FAT belt and in Oklahoma subsidence from lithosphere-scale (e.g. Beaumont until the present day, seismic imaging has furnished et al. 1992; Kooi & Beaumont 1996) to individual additional constraints on the geological interpret- structure-scale (e.g. Riba 1976; Suppe et al. 1992; ation of the deep geometry of structures, which Hardy & Poblet 1994). Thus, whereas the geometry had previously relied on geological data collected of the syn-tectonic sediments and basins within the at the surface. Seismic has, in some cases, also FAT belts is influenced by development of struc- allowed mapping of subsurface structures that are tures, the latter in turn are themselves strongly decoupled from their surface structural expression. affected by sedimentation and erosion. In short, Without forgetting the important contribution studies based on tectonic geomorphology and made by some other branches of geophysics, such palaeoseismology, P–T–t paths, geochronology as gravimetry for constraining of the deep structural and surficial processes in FAT belts sparked an configuration, or palaeomagnetism in the under- increasing interest in quantitative modelling of the standing of rotations around vertical axes, one of evolution of these belts at various scales. the most important boons to mapping of FAT belts has been the development of 3D seismic survey methods. 3D seismic data volumes provide a con- Types of FAT belts tinuous and more accurate image of the subsurface than can be obtained with 2D seismic methods Summarizing the main features of FAT belts is not (Hart 1999). Aided by the development of structural an easy task because they are remarkably diverse. tools, for example, Geosec 3D, 3D Move, Lithotect Although they exhibit a number of common charac- and Gocad software packages to visualize, charac- teristics, no single map or cross-section can provide terize and model the 3D structure of folds and a universal portrayal of a FAT belt because many thrusts, 3D seismic is starting to supply answers, parameters exert an important influence on them particularly with respect to the questions of the (see, for instance, Fitz-Diaz et al. 2011). These geometry of structures along strike and whether factors include the plate tectonics setting in which structures evolve in a self-similar fashion, that is, they developed, whether only the cover or both the whether observed spatial variations in fold geome- cover and basement rocks are involved in the struc- try reflect temporal geometric evolution (Elliott tures, the role of mechanical stratigraphy, the pres- 1976; Means 1976), or whether they evolve through ence, distribution and thickness of a salt/shale different structural forms. detachment, the occurrence of syn-orogenic ero- The contributions of tectonic geomorphology sion and deposition leading to burial, the depth to and palaeo-seismology of mountain fronts (Bull detachment and the effective elastic thickness of 2007 and references therein) have helped to deter- the lithosphere (e.g. Royden 1993), the occurrence