Document Type : Original Research Paper

Authors

1 M. Sc, Department of Geology, Sistan and Baluchestan University, Zahedan, Iran

2 Assistant Professor, Department of Geology, Sistan and Baluchestan University, Zahedan, Iran

Abstract

In Eastern Iran, the Eocene platform deposits of northwest of Birjand, are a suitable case; because a thin thrust sheet of Eocene carbonate have had the possibility to slide and fold upon an upper cretaceous plastic footwall. Moreover, this carbonate sheet entirely covered the structural arc, conduct us to recognize the origin of the bending. Achieving to this goal, we passed the structural arc along the six cross sections; four sections along radial trends and two transversal sections parallel to the inflection line. In these measurements, folds and thrust faults were defined as far as possible. The cross sections have been restored by the "Move Softwear". The amount of shortening along the radial sections were measured respectively from the east to the west are the 30-40% along A, 25-35% along B, 35-45% along C, and 15-25% along D; and along the transversal section are respectively from the south to the north about the 35-55% along E and 25-35% along F. The shortening amount in the platform carbonate at two-facing ends of the structural arc as well as the one along the inflection line are the greatest. The pattern of shortening in the arc seems to follow a buckle folding mechanism.

Keywords

Main Subjects

References
Berthiaux, A., Christman, P., Fauvelet, E., Hatrival, J. N., Vaslet, D. and Vahdati, A., 1991- Geological Map of Qayen, Scale: 1:250,000, Geological Survey of Iran, Tehran, https://www.researchgate.net/figure/Geological-map-of-the-site-Geological-Survey-of-Iran-100-000-sheet-map-of-Shiraz_fig12_271993938.
Dahlstrom, C., 1969- Balanced cross sections. Canadian Journal of Earth Science, 6, 743–758, https://www. nrcresearchpress.com/doi/abs/10.1139/e69-069.
Ellis, E. C., Wang, H. and Xiao, H. S., 2006- Measuring long- term ecological changes in densely populated landscapes using current and historical high resolution imagery. Remote Sense Environ, Vol. 100, pp. 457- 473, https://doi.org/10.1016/j.rse.2005.11.002.
Ghassemi, M. R., Schmalholz, S. M. and Ghassemi, A. R., 2010- Kinematics of constant arc length folding for different fold shapes, Journal of  Structural Geology, Vol 32, 755 -765, DOI: 10.1016/j.jsg.2010.05.002.
Hubert, M. K., 1937- Theory of scale models as applied to the study of geological structures, Bull. Geol. Soc. Am, Vol. 48, pp. 1459- 1520, https://doi.org/10.1130/GSAB-48-1459.
Johnston, S. T. and Weil, A. B., 2013- Gutiérrez-Alonso. G., Oroclines: Thick and thin, pp. 643-663, DOI: https:// doi.org/10.1130/B30765.1.
Koyi, H. A. and Maillot, B., 2007- Tectonic thickring of hanging- Wall units over a ramp. Journal of Structural Geology, Vol. 29, pp. 924- 932, DOI: 10.1016/j.jsg.2007.02.014.
Marshak, S. and Woodward, N., 1988- Introduction to cross-section balancing. In Marshak, S., and Mitra, G., eds. Basic methods of structural geology, Part II. Prentice Hall: Upper Saddle River, 303–332, https://www. researchgate.net/profile/John_Suppe/publication/281193105_Balanced_Geological_Cross-Sections_An_ Essential_Technique_in_Geological_Research_and_Exploration.
Mitra, P., Murthy, C. A. and Pal, S. K., 2000- Data condensation in large databases by incremental learning with support vector machines, In: Proc. Internat. Conf. Pattern Recognition (ICPR2000), Barcelona, Spain. Pp. 712- 715, http://cse.iitkgp.ac.in/~pabitra/paper/icpr00_svm.pdf.
Pang, K. N., Chung. S. L., Zarrinkoub. M. H., Mohammadi. S. S., Yang. H. M., Chu. C. H., Lee. H. Y. and Lo, C. H., 2012- Age, geochemical characteristics and petrogenesis of Late Cenozoic intraplate alkali basalts in the Lut–Sistan region, eastern Iran, Chemical Geology, Vol. 306-307, pp. 40-53, www.academia.edu/1838879.
Passchier, C. W. and Trouw, R. A. J., 2005- Microtectonics. Springer Verlag, Second edition, 366p, https:// www.springer.com/gp/book/9783540640035.
Pastor-Galán,D., Gutiérrez-Alonso,G., Mulchrone, K. F. and Huerta,P., 2012- Conical folding in the core of an orocline. A geometric analysis from the Cantabrian Arc (Variscan Belt of NW Iberia), pp. 210-223, https:// doi.org/10.1016/j.jsg.2012.02.010.
Pluijm, B. A. V. and Marshak, S., 2004- Earth structure an introuduction to Structural Geology and Tectonics. W. W. Norton and Company New York. London, pp. 656- 683, https://ben.earth.lsa.umich.edu/ES/.
Vahdati Daneshmand, F., Ohanian, T., Tatevosian, S., Shah beig, A., Salehi Rad, R., Vasigh, H., Soheili, M., Movahhed avall, H., Emami, M. H. and Navai, I., 1991- Geological Map of Birjand, Scale: 1:250,000, Geological Survey of Iran, Tehran, http://www.gsi.ir/fa/map.