ABSTRACT
The study area near Keban consists of the allochthonous Keban
division of the Keban-Malatya crystalline complex and the
Yuksekova island-arc rocks of the Bitlis-Puturge Complex in the
northern margin of the Bitlis Suture Zone. Detailed mapping shows
that the Palaeozoic-Triassic Keban Metamorphics are composed of
the following formations: (1) white, massive, karstic Kirklar
Marble; (2) phyllitic psammite with calcschist interlayers Calik
Formation; and (3) semi-crystallized gray Koyunatlayan Limestone.
These formations define a tectonostratigraphy with the Kirklar
Marble at the base and the Koyunatlayan Limestone at the top. The
detailed lithological description of the Keban Metamorphic rock
assemblages suggest that they represent a deformed continental
margin sedimentary sequence that has been metamorphosed to lower
greenschist facies sometime in Jurassic to early Cretaceous times.
The Keban crystalline rock units were cut by a group of hypabyssal
igneous rocks (syenite porphyry) which were produced during an
extensional regime (rifting) in late Cretaceous. In the map area,
the Campanian-lower Maastrichtian Yuksekova Volcanic rocks are
represented by mafic extrusives and mafic volcaniclastics. They
have experienced a low grade greenschist metamorphism.
In the Keban Metamorphics, structural data indicate at least two
phases of penetrative deformational events (D1 and D2). There is
also evidence for two non-penetrative tectonic deformations (Too
and T3). The contacts between the metamorphic rock units are
folded thrust faults (post-early Paleooene Pertek thrusting: Too)
marked by fault rocks; no associated folding has been seen. Along
the fault zones, a number of major mylonite and/or high-strain
zones occur in the form of ductile shear zone, each up to few
thousands of meters long and several meters wide. Besides the
foliated mylonites, the fault rocks of the Keban Metamorphics are
represented by fault breccias and gouge zones which display an
incohesive random-fabric. Detailed structural analysis shows that
the deformation mechanisms in each fault rock depends largely on
its main mineral constituent. In the map area, from east to west,
the N-S striking fault zones change from brittle-ductile shear
zones into brittle zones with the western side of the zone showing
less ductile features (eg. the Corik and Bezirgandere Faults) than
the eastern side (eg. the Hirsiz and Gelintas Faults). D1
deformation phase is marked by tight to isoclinal folds (F1);
associated foliation (S1: slaty cleavage and/or schistosity) and
mineral elongation lineation (L1). D1 does not overprint any
earlier deformation phase, but it does overprint the earlier
tectonic structure (Too). It is overprinted by later D2
deformation phase. D2 is marked by open folds (F2 ); a crenulation
cleavage (S2) and an intersection lineation (L2). They overprint
both the earlier tectonic structure (Too) and the earlier
deformation phase (D1).
In the study area, the contact between the Keban Metamorphics and
the Yuksekova Volcanic Complex is a fault contact which strikes in
N-S direction (the Keban Fault: T3). The structural analysis
conducted along the Keban Fault shows that this is a sinistral
strike-slip fault with a large thrust component. The age of the
fault is determined as post-early Paleocene to medial Eocene. The
Keban Fault is marked by brittle fault rocks, slickensides,
mylonite and other foliated highly-strained ductile fault rocks.
No folds associated with this tectonic structure have been seen.
Savci, G., 1983. Structure and Tectonics of the Keban
Metamorphics in the northern margin of the Bitlis Suture Zone,
Southeastern Turkey. Unpublished MSc. thesis, State University of
New York at Albany. 201 pp., +viii; 5 folded plates (maps).
University at Albany Science Library call number: SCIENCE
Oversize (*) QE 40 Z899 1983 S29
Savci MS thesis scanned text pdf (16MB)
Plate
1
- Geological Map of Keban area
(uncoloured geological
map, scale 1: 10,000) - 2.4MB pdf file
Plate
2 - Geological cross-section (of Keban area)
(uncoloured section, scale
1: 10,000, v.e. 2x) - 1.2MB pdf file
Plate
3 - Profile sketches and locations of folds in the Keban
metamorphics near Keban
(uncoloured sketch diagrams
and location maps) - 2.6MB pdf file
Plate
4 - Detailed structural map showing the relationship between the
Keban Metamorphics and the Yuksekova Volcanic Complex
(uncoloured outcrop maps
1:80 and 1:2 scales) - 1.9MB pdf file
Plate
5 - Simplified form surface and tectonic map of the Keban
Metamorphics near Keban
(uncoloured structural map,
scale 1: 35,000) - 0.8MB pdf file
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Geological Sciences Program, University at Albany