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Titolo:
Passive roof thrusting and forelandward fold propagation in scaled brittle-ductile physical models of thrust wedges
Autore:
Bonini, M;
Indirizzi:
Ctr Studio Geol Appennino & Catene Perimediterran, CNR, Analogue ModellingLab, I-50121 Florence, Italy Ctr Studio Geol Appennino & Catene Perimediterran Florence Italy I-50121
Titolo Testata:
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
fascicolo: B2, volume: 106, anno: 2001,
pagine: 2291 - 2311
SICI:
0148-0227(20010210)106:B2<2291:PRTAFF>2.0.ZU;2-E
Fonte:
ISI
Lingua:
ENG
Soggetto:
NORTHEASTERN BROOKS RANGE; WESTERN OVERTHRUST BELT; BARBADOS RIDGE COMPLEX; X-RAY TOMOGRAPHY; ANALOG MODELS; SALT RANGE; CONTINENTAL LITHOSPHERE; PIGGYBACK-BASIN; FLUID PRESSURES; POTWAR PLATEAU;
Tipo documento:
Review
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
104
Recensione:
Indirizzi per estratti:
Indirizzo: Bonini, M Ctr Studio Geol Appennino & Catene Perimediterran, CNR, AnalogueModellingLab, Via G Pira 4, I-50121 Florence, Italy Ctr Studio Geol Appennino & Catene Perimediterran Via G Pira 4 Florence Italy I-50121
Citazione:
M. Bonini, "Passive roof thrusting and forelandward fold propagation in scaled brittle-ductile physical models of thrust wedges", J GEO R-SOL, 106(B2), 2001, pp. 2291-2311

Abstract

A set of scaled analogue models was performed to investigate the role of adecollement layer in the structural style of fold-and-thrust belts. Silicone putty (SGM 36) has been employed to represent the ductile decollement, while frictional material (quartz sand) has been used to simulate the brittle behavior of roof and floor sequences, situated above and below the decollement, respectively. In order to explore a wide combination of strength profiles, models have been deformed under five distinct rates of compression (0.15, 0.3. 0.45, 0.6, and 1.5 cm h(-1)) employing four different thicknesses for the silicone layer (0.1, 0.2, 0.4, and 0.8 cm). Experimental results indicate that roof sequences exhibit two distinct styles of deformation: (1) passive roof duplex (PRD) geometry [e.g., Banks; and Warburton, 1986] and(2) outward propagation of folding (OFP) along the decollement [e.g., Davis and Engelder, 1985]. In PRD geometry the roof sequence remains relatively"stationary" being underthrust by a wedge-shaped floor duplex, while in OFF, displacement along the floor thrusts is transferred horizontally along the decollement layer. Experiments suggest the occurrence of a genetic relationship between shear stresses (at the base of the roof sequence 2, and within the ductile layer tau (d)) and the development of PRD or OFF geometry. For a given strain rate the deformation pattern of roof sequences depends upon the tau (b)/tau (d) ratio as well as the absolute tau (b) and tau (d) values. The transition field between OFF and PRD styles has been approximated by curvilinear regression of transition-style experimental data points, with a minimum value of 2,, varying between about 112 and 160 Pa, to enter the PRD field. Syntectonic sedimentation in the molasse basin is found to inhibit development of folding into the foreland but to promote PRD style. Experiments simulate many of the principal characteristics of fold-and-thrustbelts developed above a basal evaporite decollement, as well as the development of passive roof duplexes at mountain fronts. Shear stress values inferred for many fold-and-thrust belts correlate well the deformation fields predicted by the present experimental study, allowing to propose a simple model describing the mechanical behavior of natural roof sequences underlain by a decollement layer.

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Documento generato il 06/04/20 alle ore 08:36:54