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Paleomagnetic analysis of curved thrust belts reproduced by physical models
Language
English
Status
Published
JCR Journal
JCR Journal
Peer review journal
Yes
Title of the book
Issue/vol(year)
5 / 36 (2003)
Publisher
Elsevier
Pages (printed)
633-654
Issued date
December 2003
Abstract
This paper presents a new methodology for studying the evolution of curved mountain belts by means of paleomagnetic analyses performed on analogue models. Eleven models were designed aimed at reproducing various tectonic settings in thin-skinned tectonics. Our models analyze in particular those features reported in the literature as possible causes for peculiar rotational patterns in the outermost as well as in
the more internal fronts. In all the models the sedimentary cover was reproduced by frictional low-cohesion materials (sand and glass micro-beads), which detached either on frictional or on viscous layers. These
latter were reproduced in the models by silicone. The sand forming the models has been previously mixed with magnetite-dominated powder. Before deformation, the models were magnetized by means of two permanent magnets generating within each model a quasi-linear magnetic field of intensity variable between 20 and 100 mT. After deformation, the models were cut into closely spaced vertical sections and
sampled by means of 1x1-cm Plexiglas cylinders at several locations along curved fronts. Care was taken to collect paleomagnetic samples only within virtually undeformed thrust sheets, avoiding zones affected by pervasive shear. Afterwards, the natural remanent magnetization of these samples was measured, and alternating field demagnetization was used to isolate the principal components. The characteristic components of magnetization isolated were used to estimate the vertical-axis rotations occurring during model deformation. We find that indenters pushing into deforming belts from behind form non-rotational curved
outer fronts. The more internal fronts show oroclinal-type rotations of a smaller magnitude than that expected for a perfect orocline. Lateral symmetrical obstacles in the foreland colliding with forward propagating belts produce non-rotational outer curved fronts as well, whereas in between and inside the obstacles a perfect orocline forms only when the ratio between obstacles’ distance and thickness of the
cover is greater than 10. Finally, when a belt collides with an obstacle in the foreland oblique to the shortening direction the outer front displays rotations opposite in sign to oroclinal-type rotations, whereas
the internal fronts seem to assume an "oroclinal type" rotational pattern. Furthermore rotation is easier in laterally unconfined models, i.e. when the wedge can "escape" laterally. The results from our models may be useful when compared to paleomagnetic rotations detected in natural arcs. In these cases, our results may allow for better understanding the tectonic setting controlling the genesis of curved mountain fronts, as is the case of the Gela Nappe of Sicily we compare with some of our models.
the more internal fronts. In all the models the sedimentary cover was reproduced by frictional low-cohesion materials (sand and glass micro-beads), which detached either on frictional or on viscous layers. These
latter were reproduced in the models by silicone. The sand forming the models has been previously mixed with magnetite-dominated powder. Before deformation, the models were magnetized by means of two permanent magnets generating within each model a quasi-linear magnetic field of intensity variable between 20 and 100 mT. After deformation, the models were cut into closely spaced vertical sections and
sampled by means of 1x1-cm Plexiglas cylinders at several locations along curved fronts. Care was taken to collect paleomagnetic samples only within virtually undeformed thrust sheets, avoiding zones affected by pervasive shear. Afterwards, the natural remanent magnetization of these samples was measured, and alternating field demagnetization was used to isolate the principal components. The characteristic components of magnetization isolated were used to estimate the vertical-axis rotations occurring during model deformation. We find that indenters pushing into deforming belts from behind form non-rotational curved
outer fronts. The more internal fronts show oroclinal-type rotations of a smaller magnitude than that expected for a perfect orocline. Lateral symmetrical obstacles in the foreland colliding with forward propagating belts produce non-rotational outer curved fronts as well, whereas in between and inside the obstacles a perfect orocline forms only when the ratio between obstacles’ distance and thickness of the
cover is greater than 10. Finally, when a belt collides with an obstacle in the foreland oblique to the shortening direction the outer front displays rotations opposite in sign to oroclinal-type rotations, whereas
the internal fronts seem to assume an "oroclinal type" rotational pattern. Furthermore rotation is easier in laterally unconfined models, i.e. when the wedge can "escape" laterally. The results from our models may be useful when compared to paleomagnetic rotations detected in natural arcs. In these cases, our results may allow for better understanding the tectonic setting controlling the genesis of curved mountain fronts, as is the case of the Gela Nappe of Sicily we compare with some of our models.
References
Angelier, J., 1979. Determination of the mean principal directions of stress for a given fault population. Tectonophysics
56, 17–26.
Angelier, J., 1984. Tectonic analysis of fault slip data set. J. Geophys. Res. 89, 5835–5848.
Beck, M.E., 1998. On the mechanism of crustal block rotations in the central Andes. Tectonophysics 299, 75–92.
Borradaile, G.J., 1993. The rotation of magnetic grains. Tectonophysics 221, 381–384.
Borradaile, G.J., Mothersill, J., 1989. Tectonic strain and Paleomagnetism: experimental investigation. Physics of the
Earth and Planetary Interiors 56, 254–265.
Carey, W., 1955. The orocline concept in geotectonics. Pap. Proc. R. Soc. Tasmania 89, 255–289.
Channell, J.E.T., Oldow, J.S., Catalano, R., D’Argenio, B., 1990. Paleomagnetically determined rotations in the western
Sicilian fold and thrust belt. Tectonics 9 (4), 641–660.
Channell, J.E.T., Di Stefano, E., Sprovieri, R., 1992. Calcareous plankton biostratigraphy, magnetostratigraphy and
palaeoclimatic history of the Plio-Pleistocene Monte San Nicola section (southern Sicily). Bollettino della Societa`
Paleontologica Italiana 31, 351–382.
Choukroune, P., 1969. Un example d’analyse microtectonique d’une serie calcaire affectee de plis isopaque (concentrique).
Tectonophysics 7, 57–70.
Costa, E., Vendeville, B.C., 2002. Experimental insights on the geometry and kinematics of fold-and-thrust belts above
weak, viscous evaporitic decollement. Journal of Structural Geology 24, 1729–1739.
Davis, D., Suppe, J., Dahlen, F.A., 1983. Mechanics of fold and thrust belts and accretionary wedges. J. Geophys. Res.
88, 1153–1172.
Eldredge, S., Bachtadse, V., Van der Voo, R., 1985. Paleomagnetism and the orocline hypothesis. Tectonophysics 119,
153–179.
Gattacceca, J., Speranza, F., 2002. Paleomagnetism of Jurassic to Miocene sediments from the Apenninic carbonate
platform (southern Apennines, Italy): evidence for a 60 counterclockwise Miocene rotation. Earth Planet. Sci. Lett.
201, 19–34.
Gwinn, V., 1967. Curvature of marginal folded belts flanking major mountain ranges: Accented or caused by lateral
translation of epidermal stratified cover? Spec. Pap. Geol. Soc. Am. 115, 1–87.
Hirt, A.M., Lowrie, W., 1988. Paleomagnetism of the Umbrian-Marches orogenic belt. Tectonophysics 146, 91–103.
Hubbert, M.K., 1951. Mechanical bases for certain familiar geologic structures. Geol. Soc. Am. Bull. 62, 355–372.
Kirschvink, J.L., 1980. The least-square line and plane and the analysis of paleomagnetic data. Geophys. J. R. Astron.
Soc. 62, 699–718.
Krantz, R.W., 1991. Measurements of friction coefficients and cohesion for faulting and fault reactivation in laboratory
models using sand and sand mixtures. Tectonophysics 188, 203–207.
Lickorish, W.H., Grasso, M., Butler, R.W.H., Argnani, A., Maniscalco, R., 1999. Structural styles and regional tectonic
setting of the ‘‘Gela Nappe’’ and frontal part of the Maghrebian thrust belt in Sicily. Tectonics 18, 655–668.
Macedo, J., Marshak, S., 1999. Controls on the geometry of fold-thrust belt salients. Geol. Soc. Am. Bull. 111, 1808–
1822.
Marshak, S., 1988. Kinematics of orocline and arc formation in thin-skinned orogens. Tectonics 7 (1), 73–86.
Marshak, S., Wilkerson, M.S., Hsui, A., 1992. Generation of curved fold-thrust belts: Insights from simple physical
and analytical models. In: McClay, K.R. (Ed.), Thrust Tectonics. Chapman and Hall, London, pp. 59–90.
Mulugeta, G., 1988. Modelling the geometry of Coulomb thrust wedges. Journal of Structural Geology 10 (8), 847–
859.
Ragg, S., Grasso, M., Muller, B., 1999. Patterns of tectonic stress in Sicily from borehole breakout observations and
finite element modelling. Tectonics 18, 669–685.
Reches, Z., 1987. Determination of the tectonic stress tensor from slip along faults that obey the Coulomb yeld condition.
Tectonics 6, 849–861.
Ron, H., Freund, R., Garfunkel, Z., 1984. Block rotation by strike-slip faulting: structural and paleomagnetic evidence.
J. Geophys. Res. 89 (B7), 6259–6270.
Ron, H., Nur, A., Aydin, A., 1993. Stress field rotation or block rotation: an example from the Lake Mead fault system.
Annali di Geofisica XXXVI (2), 65–73.
Scheepers, P.J.J., Langereis, C.G., 1993. Analysis of NRM directions from Rossello composite: Implications for tectonic
rotations of the Caltanissetta basin, Sicily. Earth Planet. Sci. Lett. 119, 243–258.
Schellart, W.P., 2000. Shear test results for cohesion and friction coefficients for different granular materials: scaling
implications for their usage in analogue modelling. Tectonophysics 324, 1–16.
Schwartz, S.Y., Van der Voo, R., 1983. Paleomagnetic evaluation of the orocline hypothesis in the central and southern
Appalachians. Geophys. Res. Lett. 10, 505–508.
Speranza, F., Sagnotti, L., Mattei, M., 1997. Tectonics of the Umbria-Marche-Romagna Arc (central northern Apennines,
Italy): new paleomagnetic constraints. J. Geophys. Res. 102, 3153–3166.
Speranza, F., Maniscalco, R., Mattei, M., Di Stefano, A., Butler, R.W.H., Funiciello, R., 1999. Timing and magnitude
of rotations in the frontal thrust system of southwestern Sicily. Tectonics 18 (6), 1178–1197.
Speranza, F., Maniscalco, R., Grasso, M., 2003. Pattern of orogenic rotations in central-eastern Sicily: implications for
the timing of spreading in the Tyrrhenian Sea. Journal of the Geological Society, London 160, 183–195.
Storti, F., McKlay, K., 1995. Influence of syntectonic sedimentation on thrust wedges in analogue models. Geology 23,
999–1002.
Vendeville, B., Cobbold, P.R., Davy, P., Brun, J.P. and Choukroune, P., 1987. Physical models of extensional tectonics
at various scales. In: Coward, M.P., Dewey, J.F., Hancock, P.L. (Eds.), Continental Extensional Tectonics. Spec.
Publ. Geol. Soc. 28. Geological Society, London, pp. 95–107.
56, 17–26.
Angelier, J., 1984. Tectonic analysis of fault slip data set. J. Geophys. Res. 89, 5835–5848.
Beck, M.E., 1998. On the mechanism of crustal block rotations in the central Andes. Tectonophysics 299, 75–92.
Borradaile, G.J., 1993. The rotation of magnetic grains. Tectonophysics 221, 381–384.
Borradaile, G.J., Mothersill, J., 1989. Tectonic strain and Paleomagnetism: experimental investigation. Physics of the
Earth and Planetary Interiors 56, 254–265.
Carey, W., 1955. The orocline concept in geotectonics. Pap. Proc. R. Soc. Tasmania 89, 255–289.
Channell, J.E.T., Oldow, J.S., Catalano, R., D’Argenio, B., 1990. Paleomagnetically determined rotations in the western
Sicilian fold and thrust belt. Tectonics 9 (4), 641–660.
Channell, J.E.T., Di Stefano, E., Sprovieri, R., 1992. Calcareous plankton biostratigraphy, magnetostratigraphy and
palaeoclimatic history of the Plio-Pleistocene Monte San Nicola section (southern Sicily). Bollettino della Societa`
Paleontologica Italiana 31, 351–382.
Choukroune, P., 1969. Un example d’analyse microtectonique d’une serie calcaire affectee de plis isopaque (concentrique).
Tectonophysics 7, 57–70.
Costa, E., Vendeville, B.C., 2002. Experimental insights on the geometry and kinematics of fold-and-thrust belts above
weak, viscous evaporitic decollement. Journal of Structural Geology 24, 1729–1739.
Davis, D., Suppe, J., Dahlen, F.A., 1983. Mechanics of fold and thrust belts and accretionary wedges. J. Geophys. Res.
88, 1153–1172.
Eldredge, S., Bachtadse, V., Van der Voo, R., 1985. Paleomagnetism and the orocline hypothesis. Tectonophysics 119,
153–179.
Gattacceca, J., Speranza, F., 2002. Paleomagnetism of Jurassic to Miocene sediments from the Apenninic carbonate
platform (southern Apennines, Italy): evidence for a 60 counterclockwise Miocene rotation. Earth Planet. Sci. Lett.
201, 19–34.
Gwinn, V., 1967. Curvature of marginal folded belts flanking major mountain ranges: Accented or caused by lateral
translation of epidermal stratified cover? Spec. Pap. Geol. Soc. Am. 115, 1–87.
Hirt, A.M., Lowrie, W., 1988. Paleomagnetism of the Umbrian-Marches orogenic belt. Tectonophysics 146, 91–103.
Hubbert, M.K., 1951. Mechanical bases for certain familiar geologic structures. Geol. Soc. Am. Bull. 62, 355–372.
Kirschvink, J.L., 1980. The least-square line and plane and the analysis of paleomagnetic data. Geophys. J. R. Astron.
Soc. 62, 699–718.
Krantz, R.W., 1991. Measurements of friction coefficients and cohesion for faulting and fault reactivation in laboratory
models using sand and sand mixtures. Tectonophysics 188, 203–207.
Lickorish, W.H., Grasso, M., Butler, R.W.H., Argnani, A., Maniscalco, R., 1999. Structural styles and regional tectonic
setting of the ‘‘Gela Nappe’’ and frontal part of the Maghrebian thrust belt in Sicily. Tectonics 18, 655–668.
Macedo, J., Marshak, S., 1999. Controls on the geometry of fold-thrust belt salients. Geol. Soc. Am. Bull. 111, 1808–
1822.
Marshak, S., 1988. Kinematics of orocline and arc formation in thin-skinned orogens. Tectonics 7 (1), 73–86.
Marshak, S., Wilkerson, M.S., Hsui, A., 1992. Generation of curved fold-thrust belts: Insights from simple physical
and analytical models. In: McClay, K.R. (Ed.), Thrust Tectonics. Chapman and Hall, London, pp. 59–90.
Mulugeta, G., 1988. Modelling the geometry of Coulomb thrust wedges. Journal of Structural Geology 10 (8), 847–
859.
Ragg, S., Grasso, M., Muller, B., 1999. Patterns of tectonic stress in Sicily from borehole breakout observations and
finite element modelling. Tectonics 18, 669–685.
Reches, Z., 1987. Determination of the tectonic stress tensor from slip along faults that obey the Coulomb yeld condition.
Tectonics 6, 849–861.
Ron, H., Freund, R., Garfunkel, Z., 1984. Block rotation by strike-slip faulting: structural and paleomagnetic evidence.
J. Geophys. Res. 89 (B7), 6259–6270.
Ron, H., Nur, A., Aydin, A., 1993. Stress field rotation or block rotation: an example from the Lake Mead fault system.
Annali di Geofisica XXXVI (2), 65–73.
Scheepers, P.J.J., Langereis, C.G., 1993. Analysis of NRM directions from Rossello composite: Implications for tectonic
rotations of the Caltanissetta basin, Sicily. Earth Planet. Sci. Lett. 119, 243–258.
Schellart, W.P., 2000. Shear test results for cohesion and friction coefficients for different granular materials: scaling
implications for their usage in analogue modelling. Tectonophysics 324, 1–16.
Schwartz, S.Y., Van der Voo, R., 1983. Paleomagnetic evaluation of the orocline hypothesis in the central and southern
Appalachians. Geophys. Res. Lett. 10, 505–508.
Speranza, F., Sagnotti, L., Mattei, M., 1997. Tectonics of the Umbria-Marche-Romagna Arc (central northern Apennines,
Italy): new paleomagnetic constraints. J. Geophys. Res. 102, 3153–3166.
Speranza, F., Maniscalco, R., Mattei, M., Di Stefano, A., Butler, R.W.H., Funiciello, R., 1999. Timing and magnitude
of rotations in the frontal thrust system of southwestern Sicily. Tectonics 18 (6), 1178–1197.
Speranza, F., Maniscalco, R., Grasso, M., 2003. Pattern of orogenic rotations in central-eastern Sicily: implications for
the timing of spreading in the Tyrrhenian Sea. Journal of the Geological Society, London 160, 183–195.
Storti, F., McKlay, K., 1995. Influence of syntectonic sedimentation on thrust wedges in analogue models. Geology 23,
999–1002.
Vendeville, B., Cobbold, P.R., Davy, P., Brun, J.P. and Choukroune, P., 1987. Physical models of extensional tectonics
at various scales. In: Coward, M.P., Dewey, J.F., Hancock, P.L. (Eds.), Continental Extensional Tectonics. Spec.
Publ. Geol. Soc. 28. Geological Society, London, pp. 95–107.
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