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


9.   Folded domain morphology and inclined shearing zones (rank 3) – since 1997.

·Description. Detailed structural sections of NW Caucasus were used as source of this study. The systematic measurements of domain geometry properties (Fig. 1) and kind of its statistic study were worked out. Part of domain has properties (colored sectors at Fig.2) of “near-thrust” geometry (the angle between axial surface and envelope plain lead to 180° and the shortening value is increasing at the same time). It is better seen on diagram (AX-EN/SH, Fig. 3). This phenomenon was used for comparison the natural objects set with the theoretical models for the elucidation of mechanisms formation. Simple shearing along inclined zone in combination with shortening was used in two kinds: initial dip of zone 45° and 20° (shearing angle of horizontal pressure, Fig.4, and as a shearing along stratification or basement top, comparatively). For the North-West Caucasus structures it was shown that such structures has shape of elongated zones and that these zones have initial inclination of dip near 45° and combination of iterations as shearing angle 6° and shortening 1%. The combination of simple shearing along zone (like thrust movement) and horizontal shortening (flattening) is enough for explanation of main properties of fold related deformation of these zones. The set of longitudinal zones exist for East half of NW Caucasus and some diagonal zones exist for West half of NW Caucasus.

·Publications. First publication about the phenomena is the preprint (Yakovlev F.L. “The recognition of...”, 1997; PDF-R, N 8 in List-En). The materials about NW Caucasus structures was published in (Yakovlev F.L. “Mechanisms of linear folding...”, 2003; pictures exist, (PDF-R), N 49 in Full-List-En), abstract in English (Yakovlev F. 2005. “Inclined zones of ductile...”, 2005; PDF, N 16 â in List-En). Full paper is not exists, but the material of poster EGU-05 may be download.

·Materials. There are files of domains geometry measurements, the material of its visualization in peculiar program. The material of comparison of two models (20 and 45 degrees initial dip) exists also for different combination of simple shearing and flattening.


Fig. 1. Main parameters of domain morphology: shortening value (Sh, 4), dip of axial surface (AX, 3), dip of envelope plain (EN, 2). Dip angles are measuring regarding horizontal plain (1).


Fig. 2. Main diagnostic diagram, parameters are: AX (vertical axis), EN (horizontal axis), SH (as colors of points, axis toward obsever)

Fig. 3. The expression of inclined zone of plastic shearing in domain morphology.
1 – averaged points for SH intervals, 2 – domain vergence to South, 3 – to  North

Fig. 4. Scheme of inclined zone of plastic simple shearing (“near thrust” local mechanism )


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