Sense of displacement on the Cobequid–Chedabucto fault system, Nova Scotia, Canada

1987 ◽  
Vol 24 (2) ◽  
pp. 217-223 ◽  
Author(s):  
C. K. Mawer ◽  
J. C. White
Keyword(s):  
Nova Scotia ◽  
Fault Zone ◽  
Shear Bands ◽  
Fault System ◽  
Progressive Development ◽  
The North ◽  
Ductile Shearing ◽  
History Of ◽  
Appalachian Orogen ◽  
Meguma Terrane

The Cobequid–Chedabucto fault system of the Canadian Appalachians is a major anastomosing fault system over 300 km in length. It separates the Meguma Terrane of southern Nova Scotia from the Avalon Terrane to the north. These terranes are distinct tectonic and lithological entities in the Appalachian Orogen. Two areas at either end of this fault system have been examined in detail to determine the sense and history of offset along it. Both areas are situated on major component fault zones of the system, and both exhibit structures due to early intense ductile shearing that are overprinted by semi-brittle to brittle structures caused by later faulting. Along the eastern Chedabucto fault zone (area A), ductile structures were examined. This area is characterized by the progressive development of S–C textures and shear bands, rotated syntectonic porphyroblasts, and asymmetric minor folds, features indicative of and caused by ductile shearing. Along the western Cobequid fault zone (area B), semi-brittle and brittle structures were studied. A distinctive asymmetric geometrical package of faults, self-similar at a variety of scales, is developed throughout this part of the fault system. Ductile and brittle displacement sense (kinematic) indicators at both sites indicate a protracted history of dextral strike-slip movement. No evidence was observed for major sinistral movement.

The margins of Avalonia

1997 ◽  
Vol 134 (5) ◽  
pp. 627-636 ◽  
Author(s):  
L. R. M. COCKS ◽  
W. S. MCKERROW ◽  
C. R. VAN STAAL
Keyword(s):  
Nova Scotia ◽  
Cape Cod ◽  
The South ◽  
Cape Breton Island ◽  
Northern Margin ◽  
The North ◽  
Southern Margin ◽  
Iapetus Ocean ◽  
History Of ◽  
Meguma Terrane

During Cambrian and earliest Ordovician times, Avalonia was an area forming an integral part of the huge Gondwanan continent, probably along the northern margin of Amazonia, until in early Ordovician (late Arenig or Llanvirn) time it split off from Gondwana, leaving a widening Rheic Ocean to its south. Today, its southern margin with Gondwana extends northeast from east of Cape Cod, Massachusetts, through Nova Scotia north of the Meguma terrane, and thence below sea level to the south of Newfoundland. On the eastern side of the present Atlantic, the southern margin may separate southwest Portugal from the rest of the Iberian Peninsula; it can be traced eastwards with more certainty from the south Cornwall nappes to a line separating the Northern Phyllite Belt (on the southern margin of the Rhenohercynian terrane) and the Mid-German Crystalline High. There is no certain evidence of Avalonian crust to the northeast of the Elbe Line. The northern margin of Avalonia extends westwards from south of Denmark to the British Isles, where it merges with the Iapetus Ocean suture between Scotland and England. Traced westwards, it crosses Ireland and reappears in northern Newfoundland to the east of New World Island, where it may follow the trace of the Dog Bay Line and the Cape Ray Fault. Recent work suggests that the northern margin of Avalonia may clip the northern tip of Cape Breton Island in Nova Scotia, and then enter the North American mainland at the Bay of Chaleur; it may then be traced from north and west of the Popelogan and Bronson Hill arcs to Long Island Sound near Newhaven, Connecticut. The Cambrian to Devonian faunas reflect the history of Avalonia: initially they were purely Gondwanan but, as Ordovician time proceeded, more genera crossed firstly the Tornquist Ocean as it narrowed between Avalonia and Baltica to close in latest Ordovician and early Silurian times, and secondly the Iapetus Ocean, so that by the early Silurian most of the benthic shelly faunas, apart from the ostracods, were the same round the adjacent margins of all three palaeocontinents.

Recent and active deformation in the North Evia domain, a diffuse plate boundary between Eurasia and Aegean plates in the Western termination of the North Anatolian Fault. 

2021 ◽  
Author(s):  
Fabien Caroir ◽  
Frank Chanier ◽  
Virginie Gaullier ◽  
Julien Bailleul ◽  
Agnès Maillard-Lenoir ◽  
...  
Keyword(s):  
Fault Zone ◽  
Plate Boundary ◽  
Fault Zones ◽  
North Anatolian Fault ◽  
Fault System ◽  
Eurasian Plate ◽  
Slip Rates ◽  
The North ◽  
South West ◽  
North Aegean

<p>The Anatolia-Aegean microplate is currently extruding toward the South and the South-West. This extrusion is classically attributed to the southward retreat of the Aegean subduction zone together with the northward displacement of the Arabian plate. The displacement of Aegean-Anatolian block relative to Eurasia is accommodated by dextral motion along the North Anatolian Fault (NAF), with current slip rates of about 20 mm/yr. The NAF is propagating westward within the North Aegean domain where it gets separated into two main branches, one of them bordering the North Aegean Trough (NAT). This particular context is responsible for dextral and normal stress regimes between the Aegean plate and the Eurasian plate. South-West of the NAT, there is no identified major faults in the continuity of the NAF major branch and the plate boundary deformation is apparently distributed within a wide domain. This area is characterised by slip rates of 20 to 25 mm/yr relative to Eurasian plate but also by clockwise rotation of about 10° since ca 4 Myr. It constitutes a major extensional area involving three large rift basins: the Corinth Gulf, the Almiros Basin and the Sperchios-North Evia Gulf. The latter develops in the axis of the western termination of the NAT, and is therefore a key area to understand the present-day dynamics and the evolution of deformation within this diffuse plate boundary area.</p><p>Our study is mainly based on new structural data from field analysis and from very high resolution seismic reflexion profiles (Sparker 50-300 Joules) acquired during the WATER survey in July-August 2017 onboard the R/V “Téthys II”, but also on existing data on recent to active tectonics (i.e. earthquakes distribution, focal mechanisms, GPS data, etc.). The results from our new marine data emphasize the structural organisation and the evolution of the deformation within the North Evia region, SW of the NAT.</p><p>The combination of our structural analysis (offshore and onshore data) with available data on active/recent deformation led us to define several structural domains within the North Evia region, at the western termination of the North Anatolian Fault. The North Evia Gulf shows four main fault zones, among them the Central Basin Fault Zone (CBFZ) which is obliquely cross-cutting the rift basin and represents the continuity of the onshore Kamena Vourla - Arkitsa Fault System (KVAFS). Other major fault zones, such as the Aedipsos Politika Fault System (APFS) and the Melouna Fault Zone (MFZ) played an important role in the rift initiation but evolved recently with a left-lateral strike-slip motion. Moreover, our seismic dataset allowed to identify several faults in the Skopelos Basin including a large NW-dipping fault which affects the bathymetry and shows an important total vertical offset (>300m). Finally, we propose an update of the deformation pattern in the North Evia region including two lineaments with dextral motion that extend southwestward the North Anatolian Fault system into the Oreoi Channel and the Skopelos Basin. Moreover, the North Evia Gulf domain is dominated by active N-S extension and sinistral reactivation of former large normal faults.</p>

Walker Creek fault zone, central Rocky Mountains, British Columbia-southern continuation of the Northern Rocky Mountain Trench fault zone

2000 ◽  
Vol 37 (9) ◽  
pp. 1259-1273 ◽  
Author(s):  
M E McMechan
Keyword(s):  
Fault Zone ◽  
Late Cretaceous ◽  
Lateral Displacement ◽  
Shear Bands ◽  
Rocky Mountain ◽  
Strike Slip ◽  
Fault System ◽  
Early Eocene ◽  
Fold And Thrust Belt ◽  
Slip Displacement

Walker Creek fault zone (WCFZ), well exposed in the western Rocky Mountains of central British Columbia near 54°, comprises a 2 km wide zone of variably deformed Neoproterozoic and Cambrian strata in fault-bounded slivers and lozenges. Extensional shear bands, subhorizontal extension lineations, slickensides, mesoscopic shear bands, and other minor structures developed within and immediately adjacent to the fault zone consistently indicate right-lateral displacement. Offset stratigraphic changes in correlative Neoproterozoic strata indicate at least 60 km of right-lateral displacement across the zone. WCFZ is the southern continuation of the Northern Rocky Mountain Trench (NRMT) fault zone. It shows a through going, moderate displacement, strike-slip fault system structurally links the NRMT and the north-central part of the Southern Rocky Mountain Trench. Strike-slip motion on the WCFZ occurred in the Late Cretaceous to Early Eocene at the same time as northeast-directed shortening in the fold-and-thrust belt. Thus, oblique convergence in the eastern part of the south-central Canadian Cordillera was apparently resolved into parallel northwest-striking zones of strike-slip and thrust faulting during the Late Cretaceous to Early Eocene. The change in the net Late Cretaceous to Early Eocene displacement direction for rocks in the Rocky Mountain trenches from north (56-54°N) to northeast (52-49°N) suggests that the disappearance of strike-slip displacement and increase in fold-and-thrust belt shortening in the eastern Cordillera between 56° and 49°N is largely the result of a north-south change in relative plate motion or strain partitioning across the Cordillera, rather than the southward transformation of right-lateral strike-slip displacement on the Tintina - NRMT fault system into compressional deformation.

Transpressional deformation in the mantle below the North Anatolian fault system, Turkey

2020 ◽  
Author(s):  
Basil Tikoff ◽  
Vasili Chatzaras ◽  
Timothy Chapman ◽  
Naomi Barshi ◽  
Ercan Aldanmaz ◽  
...  
Keyword(s):  
Fault Zone ◽  
Electron Backscatter Diffraction ◽  
Preferred Orientation ◽  
North Anatolian Fault ◽  
Mantle Xenoliths ◽  
Fault System ◽  
Alkali Basalts ◽  
Crystallographic Preferred Orientation ◽  
The North ◽  
Backscatter Diffraction

<p>The North Anatolian Fault Zone (NAFZ) is a 1200-km-long, dextral intracontinental transform fault zone, and initiated ca. 13–11 Ma ago.  The NAFZ formed in response to the N-S convergence of the Eurasian and Arabian plates, accommodated by the westward motion of the Anatolia plate relative to Eurasia plate.  Mantle xenoliths were sampled in late Miocene (11.68±0.25 to 6.47±0.47 Ma) alkali basalts and basanites, immediately N of the trace of the North Anatolian fault, and were previously interpreted to sample the mantle portion of the North Anatolian fault/shear zone at depth.  The studied xenoliths are mainly spinel lherzolites and harzburgites.  Equilibration temperatures estimated from two-pyroxene geothermometers range from 775 to 975 °C, while pressures estimated from the Cr in clinopyroxene geobarometer and pseudosection modelling range from 12 to 22 kbar, which correspond to depths of 40–80 km.  We used high‐resolution X-ray computed tomography to quantify the xenolith fabric defined by the 3D shape preferred orientation of spinel grains.  Spinel displays dominantly oblate fabric ellispoids, consistent with flattening strain.  Olivine has two main crystallographic preferred orientation patterns, the axial-[010] and the A-type, determined with electron backscatter diffraction.  The axial-[010] pattern is consistent with the spinel fabric and other microstructures that show flattening strains.  To further constrain the strain path, we analyze the crystallographic vorticity axes in olivine, which show a complex pattern.  Our results are consistent with an interpretation of transpressional deformation in the upper mantle below the NAFZ, during the early stages of the development of the transform system.  Transpressional deformation is consistent with collision-induced, strike-slip extrusion of Anatolia.</p>

A late-glacial – Holocene palaeoecological record from Pye Lake on the eastern shore of Nova Scotia, CanadaGeological Survey of Canada Contribution 20080395.

2009 ◽  
Vol 46 (9) ◽  
pp. 637-650 ◽  
Author(s):  
Robert J. Mott ◽  
Ian R. Walker ◽  
Samantha L. Palmer ◽  
Martin Lavoie
Keyword(s):  
Nova Scotia ◽  
Younger Dryas ◽  
Late Glacial ◽  
Forest Composition ◽  
Eastern Shore ◽  
The North ◽  
Tundra Vegetation ◽  
History Of ◽  
Climatic History ◽  
Recent Sediments

Pollen and chironomid analyses and radiocarbon dating at Pye Lake on the eastern shore of Nova Scotia are used to outline the vegetation and climatic history of the area. The coast was deglaciated prior to ∼12 200 14C BP (14 300 cal BP), and herbaceous tundra vegetation invaded the area. Midge-inferred maximum summer surface-water temperatures in the lake ranged between 9 and 11 °C. Subsequent gradual warming to ∼18 °C by 10 800 14C BP (12 725 cal BP) favoured the migration of a variety of herbaceous and shrub taxa into the region. Rapid cooling to ∼10 °C saw vegetation revert to herbaceous tundra communities. This interval, related to the Younger Dryas cold interval of the North Atlantic and Europe, lasted until ∼10 000 14C BP (11 630 cal BP). The climate then warmed again to conditions similar to those that prevailed immediately before onset of Younger Dryas cooling. Further warming saw successive tree species migrate into the area until, by the mid-Holocene, the forests contained most of the taxa prevalent today. Since ∼3500 years ago, cooling of the climate has favoured conifer species over broad-leaved taxa. Agriculture and logging practices in the last 150 years have altered the forest composition, but pollen analysis of the most recent sediments cannot resolve these changes adequately.

scholarly journals A review of the Pan-African evolution of the Arabian Shield

GeoArabia ◽  
2002 ◽  
Vol 7 (1) ◽  
pp. 103-124 ◽  
Author(s):  
Pierre Nehlig ◽  
Antonin Genna ◽  
Fawzia Asfirane ◽  
C. Guerrot ◽  
J.M. Eberlé ◽  
...  
Keyword(s):  
Structural Evolution ◽  
Sedimentary Basins ◽  
Fault Zones ◽  
Fault System ◽  
Arabian Shield ◽  
Geologic History ◽  
Lower Paleozoic ◽  
The North ◽  
Pan African ◽  
History Of

ABSTRACT Recent fieldwork and the synthesis and reappraisal of aeromagnetic, geologic, structural, geochemical, and geochronologic data have provided a new perspective on the structural evolution and geologic history of the Arabian Shield. Although Paleoproterozoic rocks are present in the eastern part of the Shield, its geologic evolution was mainly concentrated in the period from 900 to 550 Ma during which the formation, amalgamation, and final Pan-African cratonization of several tectonostratigraphic terranes took place. The terranes are separated by major NW-trending faults and by N-, NW- and NE-oriented suture zones lined by serpentinized ultramafic rocks (ophiolites). Terrane analysis using the lithostratigraphy and geochronology of suture zones, fault zones, overlapping basins, and stitching plutons, has helped to constrain the geologic history of the Arabian Shield. Ophiolites and volcanic-arcs have been dated at between 900 and 680 Ma, with the southern terrane of Asir being older than the Midyan terrane in the north and the Ar Rayn terrane in the east. Final cratonization of the terranes between 680 and 610 Ma induced a network of anastomosing, strike-slip faults consisting of the N-trending Nabitah belt, the major NW-striking left-lateral transpressive faults (early Najd faults), lined by gneiss domes and associated with sedimentary basins, and N- to NE-trending right-lateral transpressive faults. Following the Pan-African cratonization, widespread alkaline granitization was contemporaneous with the deposition of the Jibalah volcanic and sedimentary rocks in transtensional pull-apart basins. Crustal thinning was governed by the Najd fault system of left-lateral transform faults that controlled the formation of the Jibalah basins and was synchronous with the emplacement of major E- to NW-trending dike swarms throughout the Arabian Shield. The extensional episode ended with a marine transgression in which carbonates were deposited in the Jibalah basins. Continuation of the thinning process may explain the subsequent deposition of the marine formations of the lower Paleozoic cover. Our interpretation of the distribution and chronology of orogenic zones does not correspond entirely to those proposed in earlier studies. In particular, the N-trending Nabitah and NW-trending Najd fault zones are shown to be part of the same history of oblique transpressional accretion rather than being two distinct events related to accretion and dispersion of the terranes.

scholarly journals Natural history of the terrestrial green alga, Prasiola crispa (Trebouxiophyceae), and associated Herring Gulls on Brier Island, Nova Scotia

2017 ◽  
Vol 49 (1) ◽  
pp. 49
Author(s):  
David J. Garbary ◽  
Nicholas M. Hill
Keyword(s):  
Nova Scotia ◽  
Coastal Wetland ◽  
Larus Argentatus ◽  
Bay Of Fundy ◽  
Nutrient Inputs ◽  
Herring Gulls ◽  
The North ◽  
Prasiola Crispa ◽  
History Of ◽  
First Time

The local distribution of Prasiola crispa is reported for the first time in Nova Scotia. It was common on emergent basalt outcrops in a coastal wetland on the Bay of Fundy shores of Brier Island. The alga was present on 19 of 102 basalt outcrops in one of the breeding colonies of the Herring Gull, Larus argentatus, and was only associated with basalt outcrops with gull feces. Patches of P. crispa were typically associated with the north facing slopes of the rock or were present in depressions or parts of the rock shaded by adjacent vegetation. At Western Light, the gulls are both facilitating the presence of P. crispa and acting as ecosystem engineers by nesting in the adjoining vegetation where their trampling and nutrient inputs are modifying the surrounding wetland ecosystem. 

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