FOLDING formation research
about the study of folded structures of several scale levels into thin-layered flysch-like sediments in a Hinterland
II. SEPARATE FOLDS AND AN ESTIMATION OF STRAIN VALUE
7. Multilayer folds (rank 2) – since 1981.
·Description. First version of numerical
(kinematical) model of multilayer “similar type” folds (MLF) was created at
1977 and published in 1981. The model used three kinematical mechanisms: 1)
buckling (rotation), 2) flattening and 3) shearing for competent layer in
hinge and flank situation. The shortening value for the fold estimated using
geometry of competent layer (flank angle of dip and ratio flank/hinge thickness).
There is theoretical scheme of appearance of these mechanisms from application
of physical primitive mechanisms “buckling”, “pure shearing” and “simple
shearing” for two cases – horizontal layer (hinge) and inclined layer (flank
of fold). Some natural folds in Chiaur tectonic
zone of Greater Caucasus were study. This material was used also for
comparison of results with method of single viscous layer folds as
confirmation of reliability MLF method. The second version used the first two
mechanisms (not 3) - shearing) for competent layer. In addition the 1)
rotation is combined with “shearing along bedding” for incompetent
layer and 4 situations (competent –incompetent layers, hinge – flank) were
characterized by ellipse deformation of intra-layer inclusions (rank1).
Shortening values of tens folds for
·Publications. First Russian text was published in (Yakovlev F.L. “Two methods…”, 1981; PDF-R, N 2 in List-En). First English version (without picture) was published in (Yakovlev F. The method for shortening …”, 1997; PDF N 5 in List-En). Second version (in Russian) was published in Yakovlev. “Investigation of the processes…”, 2002, text 319-320, picture 319; PDF-R, N 9 in List-En). The material of comparison of results of two methods was in the same paper on page 319. The first application of method as comparison of intra-layer deformation model data with natural one was published in (Yakovlev, Voitenko, at al. “Regarding ratio of shortening deformations...”, 2003; PDF, see full list). The comparison of two models (MLF vs. SVLF) in English was published in (Yakovlev, “Similar” folds..., 2007; PDF N 20 in List-En,). Important results were obtained due to this method in Vorontsovsky nappe structure (Yakovlev, et. al. “Tectonic paleostress fields and deformation…”, 2007; PDF N 21 in List-En;). The last information is abstract, diagrams including (Yakovlev, F. 2008 “Measurements of shortening…”, SlovTec-08, PDF, N 25 in List-En). Full information exists in the poster (SlovTec-08) also. (see download materials). Theoretical scheme of appearance of these mechanisms has published in (Yakovlev F.L. “Tectonophysical methods of study …”. 2009. pp. 318-347. [in Russian]. PDF- R.(*) N 35 in List-En)
·Some ideas. There is topic for diploma work about comparison of objects ranks 1 with 2. A student may find the competent layer in similar type fold in field, to collect measurements of geometrical parameters and to collect the set of specimens. Usual strain-analysis is used for 3D ellipsoid deformation calculation for specimens. The theoretic model and geometry of fold in competent layer is used for ellipsoid deformation prediction. Results of work will be 1) Comparison of natural object and model one, 2) To obtain the value of deformation for specimens and for the fold. Other idea is to study the deformations if you have set of folds which geometry may be measured. In this case you may mapping these results or to use it for study of structures in ranks 3-4-5.
·Materials. (Partly the same as in point 2 upper) The program code (*.exe + explanation + test examples for study) may send after your inquiry using e-mail. There are a set of monograms for parameters of intra-layer deformations (non-published), which you may used. There are pictures (field drawing) and photos (negative films 60x90 mm) for Chiaur zone of Greater Caucasus mainly, for other tectonic zones and for Vorontsovsky nappe. Total amount is near 50-70 objects. Let me know about your interest by e-mail *: email@example.com
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