Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Ramp initiation in a thrust wedge

Abstract

Collisional mountain belts are characterized by fold and thrust belts that grow through sequential stacking of thrust sheets from the interior (hinterland) to the exterior (foreland) of the mountain belt1,2,3,4,5. Each of these sheets rides on a fault that cuts up through the stratigraphic section on inclined ramps that join a flat basal fault at depth. Although this stair-step or ramp–flat geometry is well known, there is no consensus on why a particular ramp forms where it does. Perturbations in fault shape6,7, stratigraphy8,9, fluid pressure10,11, folding2,12, and surface slope13,14 have all been suggested as possible mechanisms. Here we show that such pre-existing inhomogeneities, though feasible causes, are not required. Our computer simulations show that a broad foreland-dipping plastic strain band forms at the surface near the topographic inflection produced by the previous ramp. This strain band then migrates towards the rigid base, where the plastic strain is preferentially concentrated in a thrust ramp. Subsequent ramps develop toward the foreland in a similar fashion. Syntectonic erosion and deposition may strongly control the location of thrust ramps by enhancing or removing the surface point of initiation.

Your institute does not have access to this article

Access options

Buy article

Get time limited or full article access on ReadCube.

$32.00

All prices are NET prices.

Figure 1: Thrust sheet breadth versus restored distance from the thrust front.
Figure 2: Thrust wedge after 2,500 m of backstop (left boundary) displacement.
Figure 3: Thrust wedge deformation after 2,820 m of backstop displacement.
Figure 4: Thrust wedge deformation after 3,070 m of backstop displacement.
Figure 5: Magnitude of model surface displacement accumulated during two intervals of backstop displacement.

References

  1. Bally, A. W., Gordy, P. L. & Stewart, G. A. Structure, seismic data, and orogenic evolution of the southern Canadian Rocky Mountains. Can. J. Petrol. Geol. 14, 337–381 (1966)

    Google Scholar 

  2. Dahlstrom, C. D. A. Structural geology in the eastern margin of the Canadian Rocky Mountains. Bull. Can. Petrol. Geol. 18, 332–406 (1970)

    Google Scholar 

  3. Armstrong, F. C. & Oriel, S. S. Tectonic development of Idaho-Wyoming thrust belt. Am. Assoc. Petrol. Geol. Bull. 71, 1847–1866 (1965)

    Google Scholar 

  4. Wiltschko, D. V. & Dorr, J. A. Timing and deformation in overthrust belts and foreland of Idaho, Wyoming, and Utah. Am. Assoc. Petrol. Geol. Bull. 67, 1304–1322 (1993)

    Google Scholar 

  5. Jordan, T. E., Allmendinger, R. W., Damanti, J. F. & Drake, R. E. Chronology of motion in a complete thrust belt; the Precordillera, 30-31° S., Andes Mountains. J. Geol. 101, 135–156 (1993)

    ADS  Article  Google Scholar 

  6. Wiltschko, D. V. & Eastman, D. B. Role of basement warps and faults in localizing thrust-fault ramps. Geol. Soc. Am. Mem. 158, 177–190 (1982)

    Google Scholar 

  7. Knipe, R. J. Footwall geometry and the rheology of thrust sheets. J. Struct. Geol. 7, 1–10 (1985)

    ADS  Article  Google Scholar 

  8. Bombalakis, E. G. Thrust–fault mechanics and origin of a frontal ramp. J. Struct. Geol. 8, 281–290 (1986)

    ADS  Article  Google Scholar 

  9. Platt, J. P. The mechanics of frontal imbrication, a first-order analysis. Geologische Rundschau 77, 577–589 (1986)

    ADS  Article  Google Scholar 

  10. Davis, D., Suppe, J. & Dahlen, F. A. Mechanics of fold-and-thrust belts and accretionary wedges. J. Geophys. Res. 88, 1153–1172 (1983)

    ADS  Article  Google Scholar 

  11. Cello, G. & Nurr, A. Emplacement of foreland thrust systems. Tectonics 7, 261–272 (1988)

    ADS  Article  Google Scholar 

  12. Goff, D. F., Wiltschko, D. V. & Fletcher, R. C. Decollement folding as a mechanism for thrust-ramp spacing. J. Geophys. Res. 101, 11341–11352 (1996)

    ADS  Article  Google Scholar 

  13. Panian, J. & Pilant, W. L. A possible explanation for foreland thrust propagation. J. Geophys. Res. 86, 8607–8615 (1990)

    ADS  Article  Google Scholar 

  14. Goff, D. F. & Wiltschko, D. V. Stresses beneath a ramping thrust sheet. J. Struct. Geol. 14, 437–449 (1992)

    ADS  Article  Google Scholar 

  15. Bally, A. W., Burbi, L., Cooper, C. & Ghelardoni, R. Balanced sections and seismic reflection profiles across the central Apennines. Mem. Soc. Geol. It. 35, 257–310 (1986)

    Google Scholar 

  16. Royse, F. Jr, Warner, M. A. & Reese, D. L. Deep Drilling Frontiers of the Central Rocky Mountains 41–54 (Rocky Mountain, Assoc. Geol, 1975)

    Google Scholar 

  17. Suppe, J. A retrodeformable cross section of northern Taiwan. Proc. Geol. Soc. China 23, 46–55 (1980)

    Google Scholar 

  18. Dixon, J. S. Regional structural synthesis, Wyoming salient of western overthrust belt. Am. Assoc. Petrol. Geol. Bull. 66, 1560–1580 (1982)

    Google Scholar 

  19. Price, R. A. & Mountjoy, E. W. Geologic structure of the Canadian Rocky Mountains between Bow and Athabasca rivers—a progress report. Structure of the southern Canadian Cordillera. Geol. Assoc. Can. Spec. Pap. 6, 7–25 (1970)

    Google Scholar 

  20. Hill, K. C. Structure of the Papuan fold belt, Papua New Guinea. Am. Assoc. Petrol. Geol. Bull. 75, 857–872 (1991)

    Google Scholar 

  21. Williams, G. D. Thrust tectonics in the south central Pyrenees. J. Struct. Geol. 7, 11–17 (1985)

    ADS  Article  Google Scholar 

  22. Kraig, D. H., Wiltschko, D. V. & Spang, J. H. Interaction of basement uplift and thin skinned-thrusting, Moxa arch and the Western Overthrust Belt, Wyoming: A hypothesis. Am. Assoc. Petrol. Geol. Bull. 99, 654–662 (1987)

    Article  Google Scholar 

  23. Elliot, D. The motion of thrust sheets. J. Geophys. Res. 81, 949–963 (1976)

    ADS  Article  Google Scholar 

  24. Chapple, W. M. Mechanics of thin-skinned fold-and-thrust belts. Geol. Soc. Am. Bull. 89, 1189–1198 (1978)

    ADS  Article  Google Scholar 

  25. Makel, G. & Walters, J. Finite-element analysis of thrust tectonics: computer simulation of detachment phase and development of thrust faults. Tectonophysics 226, 167–185 (1993)

    ADS  Article  Google Scholar 

  26. Mandl, G. & Shippam, G. K. Mechanical model of thrust sheet gliding and imbrication. In Thrust and Nappe Tectonics 79–98 (Geol. Soc. Lond. Spec. Publ., 1981)

    Google Scholar 

  27. Davies, R. K. & Fletcher, R. C. Shear bands in a plastic layer at yield under combined shortening and shear: A model for the fault array in a duplex. In Deformation Mechanisms, Rheology and Tectonics, 123–131 (Geol. Soc. Lond. Spec. Publ. 54, 1990)

    Google Scholar 

  28. Hibbitt, H. D., Karlson, B. I. & Sorenson, E. P. ABAQUS Theory Manual (Hibbitt, Karlson & Sorenson, Pawtucket, RI, 1997)

    Google Scholar 

  29. Handin, J. & Hager, R. V. Experimental deformation of sedimentary rocks under confining pressure: Tests at room temperature on dry samples. Am. Assoc. Petrol. Geol. Bull. 41, 1–50 (1957)

    Google Scholar 

  30. Malvern, L. E. Introduction to the Mechanics of a Continuous Media (Prentice-Hall, Englewood Cliffs, NJ, 1969)

    Google Scholar 

Download references

Acknowledgements

The NSF Tectonics programme supported this work. We wish to thank B. Johnson and J. Melosh for discussions.

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to John Panian.

Ethics declarations

Competing interests

The authors declare that they have no competing financial interests.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Panian, J., Wiltschko, D. Ramp initiation in a thrust wedge. Nature 427, 624–627 (2004). https://doi.org/10.1038/nature02334

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nature02334

Further reading

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing