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Yakovlev Fedor



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FOLDING formation research




about the study of folded structures of several scale levels into thin-layered flysch-like sediments in a Hinterland



Folder 10.   Estimation of values of folds shortening for study of nappe structures origin (ranks 2, 3) since 2006.

Description. The conception of ellipsoid of strain for measurements of folds and domains morphology (exactly axial surface dip inclination and shortening of folds value only, Fig. 3) were used for the goal of an elucidation (choice) of two mechanisms of nappe formation as numerical (kinematic) models. The idea was that lateral shortening (pushing from the hinterland) results in an increasing of shortening value of folds and more vertical orientation of its axial surface (Fig. 5A, 6). The simple horizontal shearing (gravitational sliding from hinterland) results in an increasing of shortening value of folds and decreasing of axial surface dip (to almost horizontal, Fig. 5B, 7). Measurement of shortening value (Fig. 4, see also Folder 7) and axial surface dip of near 40 folds (using the several photos, Fig. 1) of Vorontsovsky nappe (near town Sochi, North-West Caucasus, Fig. 2) have shown the coincidence the natural data with horizontal simple shearing mechanism model (Fig. 8).The solution was made that gravitational sliding as reason of nappe forming was more realistic. Geological history analysis has confirmed this solution. Details. (quazi-paper, welcome)

Publications. First publication is (Yakovlev, Sim About the relationship , 2007; PDF-R, N 19 in List-En). First publication in English is (Yakovlev, Sim, Marinin, Tectonic paleostress fields ..., 2007; PDF, N 21 in List-En). The last information in English is abstract, diagrams including (Yakovlev F., Sim L., Marinin A. The identification of gravitational mechanism of Vorontsovsky nappe, SlovTec-08, PDF, N 26 in List-En). Full information exists in the poster CorelDraw9 file (SlovTec-08) also. (see download materials). The full paper in Russian is (Yakovlev F.L., Marinin A.V., Sim L.A., Gordeev P.P. Paleo-stress fields and strain fields of Vorontsovsky nappe , 2008, PDF-R, N 33 in List-En).

Materials. There are photos of set of folds. The nomogram for shortening value estimation, the table of measurements, also as materials of two kind of modeling may be sent for an education goal. The poster (*.cdr) exits also. Let me know about your interest by e-mail. *:

Fig. 1. The natural fold from Vorontsovsky nappe bottom. North to right. Geometry parameters such as dip of axial plain, angle between flank and axial plain, thickness of layer on flank and hinge were measyred

Fig. 2. The sketch geological map of Vorontsovsky nappe near town Sochi (North-West Caucasus, incut map). The displacement distance is more then 15 km. The studied structures were found near front and bottom part of the nappe.

Fig. 3. The scheme of folded domain. Axial plain dip (3) and shortening value of folds (4) were used for comparison with models

Fig. 4. The nomogram for shortening value (SH) estimation. Geometrical parameters (dip angle of flank regarding perpendicular to axial plain and ratio of thickness of layer flank/hinge) were used. Small black points show SH value as positions among isolines.

Fig. 5. Two competitive models of natural folds forming. A lateral shortening mechanism as result of pressure from Greater Caucasus,
B Horizontal simple shearing as result of gravitational sliding.

Fig. 6. The trend of deformation parameters changing for lateral shortening (flattening) mechanism

Fig. 7. The trend of deformation parameters changing for horizontal simple shearing mechanism

Fig. 8. The trend of natural folds (blue line for aquamarine poits) in comparison with lateral shortening (negation) and horizontal shearing (agreement).

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