scholarly journals Structure and deformation history of Astypalea island, Aegean Sea

2001 ◽  
Vol 34 (1) ◽  
pp. 329 ◽  
Author(s):  
U. RING
Keyword(s):  
High Pressure ◽  
Large Scale ◽  
Aegean Sea ◽  
Structural Data ◽  
Crustal Extension ◽  
High Angle ◽  
Deformation History ◽  
Crustal Shortening ◽  
Tectonic Position ◽  
History Of

Astypalea Island lies south of the Late Cretaceous to Eocene high-pressure belt of the Cyclades and north of the Miocene high-pressure belt of the External Hellenides. The rocks of the island belong to the Tripolitza unit. The latter unit occupies a critical tectonic position in Astypalea between the unmetamorphosed Tripolitza rocks in Crete and the high-pressure Basal unit, which is correlated to the Tripolitza unit, in the Cyclades. We have subdivided the deformation history of Astypalea Island into four events, D; through D4. The problem with interpreting the structural data is that the Di and D2 events cannot unequivocally be ascribed to horizontal crustal contraction or crustal shortening. In our interpretation, Dt caused top-S internal imbrication within the Tripolitza unit as a result of crustal shortening. We envision that this event occurred when the Phyllite-Quartzite and Plattenkalk units were underthrust beneath the Tripolitza unit in the Oligocene. D was probably associated with top-N extension and may be related to large-scale crustal extension across the Cretan detachment in the Early Miocene. D3 caused high-angle faulting due to E-W contraction and D4 was due to N-S extension.

scholarly journals Along-strike variations in the Hellenide Anatolide orogen: A tale of different lithospheres and consequences

2017 ◽  
Vol 47 (2) ◽  
pp. 625 ◽  
Author(s):  
U. Ring ◽  
K. Gessner ◽  
S. Thomson ◽  
V. Markwitz
Keyword(s):  
High Pressure ◽  
Large Scale ◽  
Aegean Sea ◽  
Fold Belt ◽  
Lithosphere Structure ◽  
Continental Extension ◽  
Lithospheric Thinning ◽  
Anatolian Peninsula ◽  
History Of ◽  
Exhumation History

Structure and exhumation history of the Hellenide-Anatolide Orogen in the Aegean Sea region and the adjacent Anatolian peninsula is controlled by along-strike variations of pre-Alpine palaeogeography. In the Hellenides, Mesozoic extension created ribbon-like continental fragments of thinned and dense lithosphere that pinch out eastwards. In the east, the relatively large Anatolide microcontinent mostly escaped Mesozoic extension and lithospheric thinning, presumably because it had a distinctly different, thicker and more depleted lithosphere. In the Aegean transect these alongstrike differences in lithosphere structure ultimately resulted in sustained highpressure metamorphism followed by progressive slab retreat since about 60 Ma. Further east, collision of the Anatolide microcontinent at about 42 Ma formed a south verging greenschist-facies thrust-and-fold belt. Pronounced slab retreat in the Aegean forced differential extension resulting in a broad sinistral wrench corridor that started to from at 24-23 Ma. Since then, extension in both regions mainly controlled denudation. This review highlights how differences in pre-orogenic architecture control lithospheric thickening and the subsequent exhumation of high-pressure rocks, and how large-scale continental extension evolves

Deformation history of the Marmara Granitoid and implications for a dextral shear zone in NW Anatolia

2020 ◽  
Author(s):  
Salim Birkan Bayrak ◽  
Işıl Nur Güraslan ◽  
Alp Ünal ◽  
Ömer Kamacı ◽  
Şafak Altunkaynak ◽  
...  
Keyword(s):  
Shear Zone ◽  
Boundary Migration ◽  
Microstructural Analysis ◽  
Structural Data ◽  
Ductile Deformation ◽  
Brittle Deformation ◽  
Deformation History ◽  
Shear Sense ◽  
History Of ◽  
Dextral Shear

<p>Marmara granitoid (47 Ma) is a representative example of the Eocene post-collisional magmatism which produced several granitic plutons in NW Anatolia, Turkey. It is a W-E trending sill-like magmatic body which was concordantly emplaced into the metamorphic basement rocks of Erdek Complex and Saraylar Marble. The granitoid is represented by deformed granodiorite which displays well-developed lineation and foliation in meso-scale defined by the elongation of mica and feldspar crystals and recrystallization of quartz however, in some places, magmatic textures are preserved. Deformed granodiorite is broadly cut by aplitic and pegmatitic dikes and contains mafic enclaves which display the same deformation indicators with the main granitoid.</p><p>Microstructural analysis shows that the solid-state deformation of the Marmara granitoid is classified as ductile deformation with high temperatures and ductile-to-brittle deformation with relatively lower temperatures. Evidence for the ductile deformation of the granitoid is represented by chessboard extinction of quartz, grain boundary migration (GBM) and subgrain rotation recrystallisation (SGR) which exhibits that the deformation temperature changed from 600 <sup>o</sup>C to 400<sup>o</sup>C. Bulging recrystallization (BLG), grain size reduction of amphibole, biotite and plagioclases and microcracks on plagioclases were considered as overlying ductile-to-brittle deformation signatures which develop between 300-<250 <sup>o</sup>C temperatures.</p><p>All of these field and micro-structural data collectively suggest that the shear sense indicators such as micafish structures and δ type mantled porphyroclasts displayed stair-steppings pointing out to a right lateral movement, indicating that the structural evolution and deformation history of Marmara granitoid was controlled by a dextral shear zone.</p>

Interference fold patterns of the early Precambrian Rock Groups in the Songshan area, China

1982 ◽  
Vol 119 (5) ◽  
pp. 433-461 ◽  
Author(s):  
Shutian Suo ◽  
Ruqi Liu ◽  
Xingyuan Ma
Keyword(s):  
Large Scale ◽  
North China ◽  
Small Scale ◽  
Deformation History ◽  
North China Platform ◽  
Early Proterozoic ◽  
The North ◽  
Regional Deformation ◽  
History Of ◽  
Insight Into

SummaryThe Songshan area is located in the southern part of the North China platform, which is one of the most completely cratonized tectonic units of China. Its basement has experienced a complex evolutionary history and was eventually consolidated at the end of early Proterozoic time about 1.7 Ga ago.A systematic study has been made of the deformation history of the lower Proterozoic Songshan Group and the Archean Dengfeng Group. At least two widespread episodes of deformation can be recognised in the early Proterozoic Zhongyue tectonic cycle and three in the Archean Songyang cycle. Large scale and small scale interference patterns of the superimposed folding are investigated with the aim of recognizing possible regularities in their occurrence and of gaining an insight into the regional deformation history. Two important aspects of superimposition relationships are illustrated: the control of earlier structures upon later ones and the reform of the former by thelatter; their geometrical regularities are also dealt with respectively.

scholarly journals Coastal cliff at Lenzer Bach on Jasmund Peninsula, Rügen Island (Pleistocene Stripe 4): reconstructed history of glacitectonic deformation based on fold geometry and microstructural mapping

2019 ◽  
Vol 2 ◽  
pp. 35-41 ◽  
Author(s):  
Paul Mehlhorn ◽  
Laura Winkler ◽  
Franziska-Charlotte Grabbe ◽  
Michael Kenzler ◽  
Anna Gehrmann ◽  
...  
Keyword(s):  
Large Scale ◽  
Temporal Relationship ◽  
Proximal Part ◽  
Deformation History ◽  
Ice Flow ◽  
Coastal Cliff ◽  
History Of ◽  
Internal Deformation ◽  
Spatio Temporal ◽  
Late Weichselian

Abstract. A thrust-bound footwall syncline located within the proximal part of the southern Jasmund Glacitectonic Complex is investigated, exploring the spatio-temporal relationship between glacitectonic macro- and microstructures. Orientation and geometry of macroscale folds and thrust faults reveal a two-phased deformation history recorded by the sedimentary sequence. The deformation is a result of glacitectonic imbrication and subsequent ice flow across Jasmund Peninsula during the late Weichselian. Clast microfabrics preserved within the folded glacial diamicts reveal that till-internal deformation is mainly related to subglacial shearing within the glacier bed, which predates large-scale imbrication and folding.

scholarly journals Deformation history of the high-pressure Lycian Nappes and implications for tectonic evolution of SW Turkey

Tectonics ◽  
2003 ◽  
Vol 22 (2) ◽  
pp. n/a-n/a ◽  
Author(s):  
Gaëtan Rimmelé ◽  
Laurent Jolivet ◽  
Roland Oberhänsli ◽  
Bruno Goffé
Keyword(s):  
High Pressure ◽  
Tectonic Evolution ◽  
Deformation History ◽  
Sw Turkey ◽  
History Of

Tectonic evolution of the Yaoundé segment of the Neoproterozoic Central African Orogenic Belt in southern Cameroon

2007 ◽  
Vol 44 (4) ◽  
pp. 433-444 ◽  
Author(s):  
Hubert Mvondo ◽  
Sébastien Owona ◽  
Joseph Mvondo Ondoa ◽  
Jean Essono
Keyword(s):  
Large Scale ◽  
Regional Scale ◽  
Orogenic Belt ◽  
Ductile Deformation ◽  
Deformation History ◽  
Granulite Metamorphism ◽  
High Pressure Granulite ◽  
Southern Cameroon ◽  
History Of ◽  
East West

The deformation history of the Neoproterozoic Central African Orogenic Belt in southern Cameroon is well recorded in the low- to high-grade rocks outcropping in the area around Yaoundé. The fabrics in these rocks are consistent with two main ductile deformation events D1 and D2. D1 predated emplacement of calc-alkaline dioritic bodies and caused the formation of nappes that resulted in high-pressure granulite metamorphism of soft sediments. A strong overprinting of these nappes during D2 symmetric extension, probably associated with large-scale foliation boudinage and (or) gneissic doming and intense magmatic underplating, gave rise to regional flat-lying fabrics. The latter were further buckled by D3 and D4 folding phases defining a vertical constriction occurring with a major east–west to NW–SE shortening direction. The corresponding F3 and F4 folds trend north–south to NE–SW and east–west to NW–SE, respectively, and represent the main regional strain patterns. Based on the east–west to NW–SE maximum shortening orientation indicated by F3 folds, it is proposed that the nappe-stacking phase D1 occurred in the same direction. The deformation history in the area can thus be described as corresponding principally to alternating east–west to NW–SE contractions and north–south to NE–SW orogenic-parallel extensions. At the regional scale, this could be due to the Transaharan east–west collisional system.

Alpine high-pressure metamorphism at the Almyropotamos window (southern Evia, Greece)

2000 ◽  
Vol 137 (4) ◽  
pp. 367-380 ◽  
Author(s):  
YONATHAN SHAKED ◽  
DOV AVIGAD ◽  
ZVI GARFUNKEL
Keyword(s):  
High Pressure ◽  
Large Scale ◽  
Structural Data ◽  
Late Eocene ◽  
Crustal Thickening ◽  
Lower Grade ◽  
The South ◽  
Northern Greece ◽  
High Pressure Metamorphism ◽  
Early Oligocene

The Alpine orogenic belt of the Hellenides has been strongly reworked by ductile and brittle extensional tectonics. Extensional structures have affected the central Aegean region and obliterated much of the original orogenic architecture since at least early Miocene times. In the area of Almyropotamos (on the island of Evia, flanking the western part of the Aegean) a unique remnant compressional nappe stack involving Tertiary metamorphic rocks has been preserved. This nappe sequence comprises a high-pressure rock unit on top of a lower grade unit. The upper unit (South Evia Blueschist Belt) is thought to be the westward continuation of the Cycladic blueschist belt metamorphosed at high-pressure conditions during Late Cretaceous–Eocene times. The underlying unit (the Almyropotamos Unit) is a continental margin sequence covered by a flysch and containing Lutetian nummulites, indicating that this unit accumulated sediments until at least late Eocene times.In the present study we analyse the petrology of the Almyropotamos nappe stack and define the P–T conditions of each of the different rock units exposed there. The presence of glaucophane, lawsonite rimmed by epidote, and jadeite (70 mol.%) suggest that peak P–T conditions in the South Evia Blueschist Belt reached approximately 10–12 kbar and 350–450 °C. Unlike previous studies, which estimated that the underlying Almyropotamos Unit reached only greenschist-facies conditions, glaucophane relics and Si-rich phengites were found by us in this unit. These indicate that high-pressure metamorphism and crustal thickening in this part of the Aegean lasted until at least the late Eocene or early Oligocene. We note that in this respect the architecture of southern Evia resembles that of northern Greece (Olympos, Ossa). Our structural data indicate that rock units in the Almyropotamos area record different folding phases, with the South Evia Blueschist Belt having a more complex fold history than the underlying Almyropotamos Unit. The entire nappe stack shares large-scale folds which are E–W trending, and locally overturned-to-the-south, and which may represent (at present coordinates) N–S contraction and nappe transport.

Freeze-etch TEM of aqueous polymer gel network morphology

1986 ◽  
Vol 44 ◽  
pp. 796-797
Author(s):  
J. A. N. Zasadzinski ◽  
R. K. Prud'homme
Keyword(s):  
Metal Ion ◽  
Polymer Network ◽  
Polymer Gels ◽  
Polymer Gel ◽  
Deformation History ◽  
Crosslinked Polymer ◽  
Aqueous Polymer ◽  
History Of ◽  
Gel Network ◽  
Network Morphology

The rheological and mechanical properties of crosslinked polymer gels arise from the structure of the gel network. In turn, the structure of the gel network results from: thermodynamically determined interactions between the polymer chain segments, the interactions of the crosslinking metal ion with the polymer, and the deformation history of the network. Interpretations of mechanical and rheological measurements on polymer gels invariably begin with a conceptual model of,the microstructure of the gel network derived from polymer kinetic theory. In the present work, we use freeze-etch replication TEM to image the polymer network morphology of titanium crosslinked hydroxypropyl guars in an attempt to directly relate macroscopic phenomena with network structure.

Sign in / Sign up

Export Citation Format

Share Document