Southeast Anatolian Orogenic Belt revisited (geology and evolution)

2019 ◽  
Vol 56 (11) ◽  
pp. 1163-1180 ◽  
Author(s):  
Yücel Yılmaz
Keyword(s):  
High Pressure ◽  
Middle Eocene ◽  
Late Eocene ◽  
Orogenic Belt ◽  
Arabian Plate ◽  
Volcanic Arc ◽  
High Pressure Metamorphism ◽  
The North ◽  
Oceanic Slab ◽  
Arabian Platform

The Southeast Anatolian Orogenic Belt consists of the Arabian Platform, a zone of imbrication, and a nappe zone. The Arabian Platform is represented by a thick marine succession. The zone of imbrication is a narrow belt sandwiched between the Arabian Platform and the nappes. The nappes are the highest tectonic unit. They consist of two continental slivers separated by ophiolitic associations representing oceanic environments. They were involved in the orogenic development and formed two metamorphic belts. The oceanic environment survived by the end of Middle Eocene. A northward subduction began in this ocean and generated the Elbistan–Yüksekova arc built above the Göksun ophiolite. Development of the Southeastern Anatolian Orogenic Belt began in the north, where the Binboğa–Malatya metamorphic massif, collided with the Elbistan volcanic arc to the end of Early Eocene period. Later new tectonic entities were accreted to this progressively growing and southerly transporting nappe stack. In the lower plate, the southern continental sliver that was attached to the oceanic slab subducted together and underwent high-pressure metamorphism. The subducting oceanic slab retreated. Asthenospheric inflow caused high-temperature metamorphism, which superimposed on the previous high-pressure metamorphism. The oceanic and continental fragments formed the Bitlis Massif and the Berit metaophiolite when exhumed. A younger volcanic arc was built on the ocean floor to the south. Accretion of the volcanic arc to the nappe pile occurred during the Late Eocene period. The orogenic belt was formed when the nappes collided with the Arabian plate during the Late Miocene.

Pre-Priabonian Palaeogene formations in southwestern Bulgaria and northern Greece: stratigraphy and tectonic implications

1998 ◽  
Vol 135 (1) ◽  
pp. 101-119 ◽  
Author(s):  
IVAN S. ZAGORCHEV
Keyword(s):  
Late Cretaceous ◽  
Middle Eocene ◽  
Regional Metamorphism ◽  
Late Eocene ◽  
Thin Layers ◽  
The South ◽  
Northern Greece ◽  
The North ◽  
Early Oligocene ◽  
Metamorphic Core

The Paril Formation (South Pirin and Slavyanka Mountains, southwestern Bulgaria) and the Prodromos Formation (Orvilos and Menikion Mountains, northern Greece) consist of breccia and olistostrome built up predominantly of marble fragments from the Precambrian Dobrostan Marble Formation (Bulgaria) and its equivalent Bos-Dag Marble Formation (Greece). The breccia and olistostrome are interbedded with thin layers of calcarenites (with occasional marble pebbles), siltstones, sandstones and limestones. The Paril and Prodromos formations unconformably cover the Precambrian marbles, and are themselves covered unconformably by Miocene and Pliocene sediments (Nevrokop Formation). The rocks of the Paril Formation are intruded by the Palaeogene (Late Eocene–Early Oligocene) Teshovo granitoid pluton, and are deformed and preserved in the two limbs of a Palaeogene anticline cored by the Teshovo pluton (Teshovo anticline). The Palaeocene–Middle Eocene age of the formations is based on these contact relations, and on occasional finds of Tertiary pollen, as well as on correlations with similar formations of the Laki (Kroumovgrad) Group throughout the Rhodope region.The presence of Palaeogene sediments within the pre-Palaeogene Pirin–Pangaion structural zone invalidates the concept of a ‘Rhodope metamorphic core complex’ that supposedly has undergone Palaeogene amphibolite-facies regional metamorphism, and afterwards has been exhumed by rapid crustal extension in Late Oligocene–Miocene times along a regional detachment surface. Other Palaeogene formations of pre-Priabonian (Middle Eocene and/or Bartonian) or earliest Priabonian age occur at the base of the Palaeogene sections in the Mesta graben complex (Dobrinishka Formation) and the Padesh basin (Souhostrel and Komatinitsa formations). The deposition of coarse continental sediments grading into marine formations (Laki or Kroumovgrad Group) in the Rhodope region at the beginning of the Palaeogene Period marks the first intense fragmentation of the mid- to late Cretaceous orogen, in particular, of the thickened body of the Morava-Rhodope structural zone situated to the south of the Srednogorie zone. The Srednogorie zone itself was folded and uplifted in Late Cretaceous time, thus dividing Palaeocene–Middle Eocene flysch of the Louda Kamchiya trough to the north, from the newly formed East Rhodope–West Thrace depression to the south.

scholarly journals New microplanktonic biostratigraphy and depositional sequences across the Middle–Late Eocene and Oligocene boundaries in eastern Jordan

GeoArabia ◽  
2015 ◽  
Vol 20 (3) ◽  
pp. 145-172
Author(s):  
Sherif Farouk ◽  
Mahmoud Faris ◽  
Fayez Ahmad ◽  
John H. Powell
Keyword(s):  
Middle Eocene ◽  
Planktonic Foraminifera ◽  
Eastern Desert ◽  
Late Eocene ◽  
Arabian Plate ◽  
Rapid Decline ◽  
Calcareous Nannofossil ◽  
Upper Eocene ◽  
Depositional Sequences ◽  
Global Correlation

ABSTRACT The first detailed calcareous nannofossil and planktonic foraminiferal biostratigraphic and integrated lithofacies analyses of the Eocene–Oligocene transition at the Qa’ Faydat ad Dahikiya area in the Eastern Desert of Jordan, on the border with Saudi Arabia, is presented. Three calcareous nannofossil zones namely: Discoaster saipanensis (NP17), Chiasmolithus oamaruensis (NP18) and Ericsonia subdisticha (NP21), and three planktonic foraminiferal zones: upper part of Truncorotaloides rohri (E13), Globigerinatheka semiinvoluta (E14) and Cassigerinella chipolensis/Pseudohastigerina micra (O1) are identified. Calcareous nannofossil bioevents recorded in the present study show numerous discrepancies with the Standard biostratigraphic zonal schemes to detect the Middle/Upper Eocene boundary (e.g. the highest occurrences (HOs) of Chiasmolithus solitus, C. grandis, and lowest occurrences (LOs) of C. oamaruensis, Isthmolithus recurvus are not considered reliable markers for global correlation). The Middle/Upper Eocene boundary occurs in the current study above the extinctions of large muricate planktonic foraminifera (large Acarinina and Truncorotaloides spp.) which coincide within the equivalent calcareous nannofossil NP18 Zone. These microplanktonic bioevents seem to constitute more reliable markers for the base of the Upper Eocene in different provinces. The uppermost portion of the Middle Eocene is characterized by an observed drop in faunal content and, most likely, primarily denotes the effect of the major fall in eustatic sea level. A major unconformity (disconformity) marked by a mineralized hardground representing a lowstand is recorded in the present study at the Eocene–Oligocene transition that reveals an unexpected ca. 2.1 Myr duration, separating Eocene (NP18/E14 zones) from Oligocene (NP21/O1 zones). Furthermore, the microfossil turnover associated with a rapid decline of the microfossil assemblages shows a distinct drop in diversity and abundance towards the Eocene/Oligocene unconformity and is associated with a sharp lithological break marked, at the base, by a mineralized hardground representing a major sequence boundary. These bioevents, depositional sequences and the depositional hiatus correlate well with different parts of the Arabian and African plates, but the magnitude of the faunal break differs from place to place as a result of intraplate deformation during the regional Oligocene regression of Neo-Tethys on the northern Arabian Plate. The presence of the Lower Oligocene shallow-marine calcareous planktonic assemblages in the study area indicate that communication between the eastern and western provinces of the western Neo-Tethys region still existed at this time.

scholarly journals The Tectonic Evolution of Interior Oman

GeoArabia ◽  
1996 ◽  
Vol 1 (1) ◽  
pp. 28-51 ◽  
Author(s):  
Ramon J.H. Loosveld ◽  
Andy Bell ◽  
Jos J.M. Terken
Keyword(s):  
Sedimentary Basins ◽  
Late Eocene ◽  
Indian Plate ◽  
Arabian Plate ◽  
Time Interval ◽  
Passive Margins ◽  
The North ◽  
Hydrocarbon Traps ◽  
Early Oligocene ◽  
Sea Floor Spreading

ABSTRACT The evolution of Oman’s onshore sedimentary basins from the Late Precambrian to the Present is reflected by six tectono-stratigraphic units. Unit I, the Precambrian basement, represents continental accretion. Units II and III, Infracambrian to Ordovician, may reflect two periods of rifting, possibly related to Najd movements in western Saudi Arabia. The northeast-southwest trending salt basins formed during this time interval. A classical “steer’s head” basin geometry is developed in North Oman, whereas a less complete rift-sag sequence is preserved in South Oman. Of the entire time-span from Late Silurian to Mid-Carboniferous, only little Devonian (Emsian) sediment is preserved. Unit IV, Late Carboniferous to Mid-Cretaceous, reflects the break-up of Gondwana and the creation of the northeastern and southeastern passive margins of the Arabian Plate. Unit V documents intra-plate deformation related to Late Cretaceous continent-ocean obduction in the north and transpressional movements of the Indian Plate in the east. Unit VI, spanning the Tertiary, represents a return to quiet conditions followed by continent-continent collision in the north. Following Late Eocene uplift, the Gulf of Aden rift developed in the south in the early Oligocene, with sea-floor spreading from the Late Miocene onwards. Salt flow and dissolution, both playing a major role in the configuration of most intra- and post-salt hydrocarbon traps in Oman, are episodic and can be related to tectonic events.

Interpretation of structures in the southeastern Nechako Basin, British Columbia, from seismic reflection, well log, and potential field data1This article is one of a series of papers published in this Special Issue on the theme of New insights in Cordilleran Intermontane geoscience: reducing exploration risk in the mountain pine beetle-affected area, British Columbia.2Geological Survey of Canada Contribution 20100002.

2011 ◽  
Vol 48 (6) ◽  
pp. 1000-1020 ◽  
Author(s):  
Nathan Hayward ◽  
Andrew J. Calvert
Keyword(s):  
British Columbia ◽  
Potential Field ◽  
Seismic Reflection ◽  
Middle Eocene ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Late Eocene ◽  
Strike Slip ◽  
Potential Field Data ◽  
The North

The structure and stratigraphy of the southeast Nechako Basin, which are poorly understood primarily because of substantial volcanic cover, are investigated in an analysis of seismic reflection, well, and potential field data. Formation and development of the SE Nechako Basin resulted in sub-basins containing Cretaceous and Eocene rocks. Interpretation reveals that dextral transtension in the Early to Middle Eocene created NNW-trending, en echelon, strike-slip faults linked by pull-apart basins, which locally contain a thickness of Eocene volcaniclastic rocks of >3 km. This structural pattern is consistent with regional observations that suggest the transfer of slip from the Yalakom fault to the north via a series of en echelon strike-slip faults. In the Middle to Late Eocene, faults associated with a change in the direction of stress, echoed by the north-trending right-lateral Fraser fault, reactivated and cut earlier structures. A simple model agrees with local observations, that northeast-directed compression was subparallel to the relic Cretaceous grain. Cretaceous rocks are discontinuous throughout the basin and may be remnants of a broader basin, or a number of contemporaneous basins, formed in a regional transpressional tectonic setting that caused northeast-directed thrusting along the eastern side of the Coast Plutonic Complex. Results suggest that thrusting affected most of the SE Nechako Basin, as observed across the Intermontane Belt to the northwest and southeast. The pattern of deposition of Neogene volcanic rocks of the Chilcotin Group was in part controlled by the Eocene structural grain, but we find no evidence of Neogene deformation.

scholarly journals North Atlantic marine biogenic silica accumulation through the early to middle Paleogene: implications for ocean circulation and silicate weathering feedback

2021 ◽  
Vol 17 (5) ◽  
pp. 1937-1954
Author(s):  
Jakub Witkowski ◽  
Karolina Bryłka ◽  
Steven M. Bohaty ◽  
Elżbieta Mydłowska ◽  
Donald E. Penman ◽  
...  
Keyword(s):  
North Atlantic ◽  
Biogenic Silica ◽  
Middle Eocene ◽  
Nutrient Supply ◽  
Late Eocene ◽  
Silicate Weathering ◽  
Early Eocene ◽  
The North ◽  
History Of ◽  
The North Atlantic

Abstract. The Paleogene history of biogenic opal accumulation in the North Atlantic provides insight into both the evolution of deepwater circulation in the Atlantic basin and weathering responses to major climate shifts. However, existing records are compromised by low temporal resolution and/or stratigraphic discontinuities. In order to address this problem, we present a multi-site, high-resolution record of biogenic silica (bioSiO2) accumulation from Blake Nose (ODP Leg 171B, western North Atlantic) spanning the early Paleocene to late Eocene time interval (∼65–34 Ma). This record represents the longest single-locality history of marine bioSiO2 burial compiled to date and offers a unique perspective into changes in bioSiO2 fluxes through the early to middle Paleogene extreme greenhouse interval and the subsequent period of long-term cooling. Blake Nose bioSiO2 fluxes display prominent fluctuations that we attribute to variations in sub-thermocline nutrient supply via cyclonic eddies associated with the Gulf Stream. Following elevated and pulsed bioSiO2 accumulation through the Paleocene to early Eocene greenhouse interval, a prolonged interval of markedly elevated bioSiO2 flux in the middle Eocene between ∼46 and 42 Ma is proposed to reflect nutrient enrichment at Blake Nose due to invigorated overturning circulation following an early onset of Northern Component Water export from the Norwegian–Greenland Sea at ∼49 Ma. Reduced bioSiO2 flux in the North Atlantic, in combination with increased bioSiO2 flux documented in existing records from the equatorial Pacific between ∼42 and 38 Ma, is interpreted to indicate diminished nutrient supply and reduced biosiliceous productivity at Blake Nose in response to weakening of the overturning circulation. Subsequently, in the late Eocene, a deepwater circulation regime favoring limited bioSiO2 burial in the Atlantic and enhanced bioSiO2 burial in the Pacific was established after ∼38 Ma, likely in conjunction with re-invigoration of deepwater export from the North Atlantic. We also observe that Blake Nose bioSiO2 fluxes through the middle Eocene cooling interval (∼48 to 34 Ma) are similar to or higher than background fluxes throughout the late Paleocene–early Eocene interval (∼65 to 48 Ma) of intense greenhouse warmth. This observation is consistent with a temporally variable rather than constant silicate weathering feedback strength model for the Paleogene, which would instead predict that marine bioSiO2 burial should peak during periods of extreme warming.

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.

Metamorphic rocks of an intermediate facies series juxtaposed at the Start boundary, southwest England

1981 ◽  
Vol 118 (3) ◽  
pp. 297-301 ◽  
Author(s):  
D. Robinson
Keyword(s):  
High Pressure ◽  
Diffraction Analysis ◽  
Mineral Assemblage ◽  
White Mica ◽  
Lower Pressure ◽  
Metamorphic Rocks ◽  
X Ray Diffraction ◽  
X Ray ◽  
High Pressure Metamorphism ◽  
The North

SummaryX-ray diffraction analysis of metamorphic rocks from the Start peninsula shows that the dominant mineral assemblage in the Start schists is quartz-muscovite-chlorite ± paragonite ± albite. The assemblage in the Devonian phyllites to the north of the Start boundary is quartz-muscovite-chlorite and the crystallinity of the white mica there is indicative of greenschist fades. The b0 parameter of white micas indicates that the metamorphism was of an intermediate facies series (Barrovian type), but of a lower pressure variety to the north of the Start boundary juxtaposed against a higher pressure variety to the south. No evidence exists of the high pressure metamorphism needed to support tectonic models in which the Start boundary is identified as a suture representing a Variscan subduction margin.

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