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last update 14/10/2009 |
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Yakovlev
Fedor Home-page |
FOLDING formation research Guide: about the study of folded structures of several
scale levels into thin-layered flysch-like sediments in a Hinterland |
V. RESTORATION OF STRUCTURE FOR DOMAINS AND TECTONIC
ZONES, BALANCING SECTIONS
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Folder 13. Retro-deformation for
linear folding structures in cross-section (core of method) (ranks 3, 5) –
since 1987. ·Description. The idea of ellipsoid of strain
(ellipse for 2D strain in case of linear folding) is used for the restoration
of prefolded state of cross-section. Cross-section
is divided to set of domains and three parameters of domain geometry measured
(Fig. 1): axial
surface dip inclination (AX), envelope dip inclination (EN), shortening of
folds (SH) (see folders 6, 7). The domains part of cross-section line
measured also as length and it angle of tilting. Three cinematic operations (Fig. 2) are used for transformation of
ellipsoid to sphere (of ellipse to cycle): 1) rotation to horizontal position
of envelope plane, 2) simple horizontal shearing to vertical position of
axial plane and 3) pure shearing (horizontal extension) to folds disappearing
(ellipse is transforming to cycle). Length of domains section line and it
tilting have the same perturbations and new length of line and it tilting
appear in horizontal prefolded layering. A
consecutive junction of all domains is method of prefolded
section restoration (Fig. 3). It
is a single balancing sections method for hinterland structures now. The
fault displacements may be calculated also (Fig. 4). Each fault plain is used as
boundary of adjoining domains, of cause. The dip angle of fault plain should
be measured for natural structure. It is assumed that this plain is part of
domain and initial dip of plain may be calculated by the same three cinematic
operations as for domain. Difference of “stratigraphic” levels between
layers, which is contacting on fault on its sides, is vertical displacement.
The horizontal displacement is calculating as function of vertical shift and
initial dip of fault plain. ·Publications. First publication of core
of method is paper (Yakovlev F.L. “A Study of the Kinematic…”,
1987, pages 319-320; PDF, N
3 in List-En,). The explanation of computer program was made in (Yakovlev
F.L. “Investigation of the processes …”, 2002, pages 323-325; PDF-R, N 12 in List-En,). Full new description has
published in (Yakovlev F.L. Reconstruction of
Linear Fold Structures …, 2009, pp.
1023–1034. [in Russian, in English]. PDF-en N 36
in List-En) ·Materials.
There are computer program for recent section visualization (for each domain)
and it transformation to prefolded
state and it visualization also. The measurements of domain geometry are used
as txt-files. Test examples exist for theoretic and natural; structures. Let me know about your interest by e-mail. *: yak@ifz.ru |
Fig.
1. The domain parameters: 1 – horizontal plain, 2 – envelope plain dip, 3
– axial plain dip, 4 – ellipsoid of strain for domain isometric layering
rocks volume |
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Fig.
2. Three cinematic operations from recent state (1) to ptefolded one (4). A – rotation up to horizontal position
of envelope plain, B – simple shearing up to vertical position of axial
plain, C – elongation (pure shearing) up to folds disappearing (ellipse
became circl) |
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Fig.
3. (to right upper) The PC-program procedures and testing. Upper
section: 10 domains were transformed by convection (1-st
stage) and flattening 50% (2-nd stage). Last two
domains parameters as “measured” (black) and restored (three lower blue lines)
and total resume are shown in table. Restored “prefolded” states of domains as common structure are
shown at lower section. The goal prefolded length of
10000 was calculated as 9906 with the error near 1%. |
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Fig. 4. The natural folded structure
section (part of section number 7, North-West Caucasus) after measurements of
domain parameters and construction by PC-program. Upper section – recent structure,
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© 2009, ÈÔÇ ĐÀÍ, ßêîâëåâ |