scholarly journals Tectonic domains and exhumation history of the Omineca Belt in southeastern British Columbia from 40Ar/39Ar thermochronology

2020 ◽  
Vol 57 (8) ◽  
pp. 918-946
Author(s):  
Ewan R. Webster ◽  
Douglas A. Archibald ◽  
David R.M. Pattison ◽  
Jessica A. Pickett ◽  
Joel C. Jansen
Keyword(s):  
British Columbia ◽  
Late Cretaceous ◽  
Regional Scale ◽  
Metamorphic Rocks ◽  
Normal Faults ◽  
Canadian Cordillera ◽  
Data Set ◽  
Rapid Cooling ◽  
Central Domain ◽  
Eastern Domain

A large geochronological data set comprising 40Ar/39Ar and K–Ar (hornblende, muscovite, biotite, and K-feldspar), Rb–Sr (muscovite), fission track (zircon and apatite) and U–Pb (zircon and monazite) dates has been compiled for the southern Kootenay Arc and western Purcell anticlinorium in the Omineca Belt of the Canadian Cordillera in southeastern British Columbia. New 40Ar/39Ar data for hornblende, muscovite, biotite, and alkali feldspar are presented and combined with data from other studies. We integrate these data with recent advances in the geology of the region to define three partially fault-bounded domains with differing geological and exhumation histories, here termed the western, central, and eastern domains. The western domain is characterized by (1) late synkinematic Jurassic plutons with hornblende, muscovite, and biotite 40Ar/39Ar plateau dates between 170 and 165 Ma, some of which are within error of the U–Pb zircon dates for these plutons, and (2) late Early Cretaceous (118–102 Ma) plutons commonly with concordant mica 40Ar/39Ar plateau dates of a similar age range, indicating rapid cooling following emplacement of both suites. The central domain is bounded by regional-scale normal faults (Gallagher and Midge Creek faults, Blazed Creek/Next Creek faults, and Purcell Trench fault) and contains superposed Early and Late Cretaceous zones of Barrovian metamorphic rocks and several mid- to Late Cretaceous, post-kinematic plutons. The transition from the western domain into the central domain is characterized by 40Ar/39Ar mica age spectra showing a progression of increasing thermal overprinting. Along the north–south length of the central domain, biotite and muscovite yield Paleocene to Eocene K–Ar and 40Ar/39Ar plateau dates between 66 and 40 Ma. The eastern domain consists of (1) a southern portion that occurs in the hanging wall of the Purcell Trench fault, comprising mid-Cretaceous intrusions of the Bayonne magmatic suite emplaced into biotite zone metasedimentary rocks of the Mesoproterozoic Belt-Purcell Supergroup in the western Purcell anticlinorium, and (2) a northern portion that shows a continuous transition with the northern part of the central domain north of the terminus of the Purcell Trench fault. Cretaceous igneous rocks in the southern portion of the eastern and western domains have 40Ar/39Ar mica plateau dates that are <9 Myr younger than U–Pb zircon dates, indicating rapid cooling shortly after emplacement. 40Ar/39Ar step-heating reveals that there was a mid- to Late Cretaceous thermal disturbance in the eastern domain, possibly related to emplacement of younger plutons at deeper crustal levels and the Late Cretaceous Barrovian metamorphic event recorded in rocks of the central domain, such that biotite with dates <ca. 73 Ma yield plateau age spectra but those with older dates are disturbed. The new geochronology, combined with recent mapping and metamorphic studies, leads to the conclusion that the exhumation of the Barrovian metamorphic rocks of the central domain was a multi-stage process. The central domain experienced rapid tectonic decompression and minor pluton emplacement in the Late Cretaceous to early Paleocene (76–61 Ma) when the Cordilleran orogen was under regional contraction during which most of the exhumation occurred. Final exhumation in the footwall of Eocene normal faults was less significant and occurred between 53 and ca. 46 Ma when the Cordilleran orogen had transitioned to regional extension, by which time the three domains had attained a similar crustal level. These episodes of exhumation are similar to those found in other core complexes in the southern Canadian Cordillera and contiguous northern Idaho and Washington. The earlier episode is coincident with regional-scale, Late Cretaceous thrust faulting in the Foreland Belt of the Rocky Mountains. Eocene normal faulting and final exhumation of core complexes in the Omineca Belt mark the end of contraction in the Foreland Belt.

scholarly journals Polyphase evolution of Pelagonia (northern Greece) revealed by geological and fission-track data

Solid Earth ◽  
2015 ◽  
Vol 6 (1) ◽  
pp. 285-302 ◽  
Author(s):  
F. L. Schenker ◽  
M. G. Fellin ◽  
J.-P. Burg
Keyword(s):  
Early Cretaceous ◽  
Late Cretaceous ◽  
Fission Track ◽  
Regional Scale ◽  
Normal Faults ◽  
Recent Sediment ◽  
Northern Greece ◽  
Rapid Cooling ◽  
Fission Track Ages ◽  
Pelagonian Zone

Abstract. The Pelagonian zone, situated between the External Hellenides/Cyclades to the west and the Axios/Vardar/Almopias zone (AVAZ) and the Rhodope to the east, was involved in late Early Cretaceous and in Late Cretaceous–Eocene orogenic events whose duration and extent are still controversial. This paper constrains their late thermal imprints. New and previously published zircon (ZFT) and apatite (AFT) fission-track ages show cooling below 240 °C of the metamorphic western AVAZ imbricates between 102 and 93–90 Ma, of northern Pelagonia between 86 and 68 Ma, of the eastern AVAZ at 80 Ma and of the western Rhodope at 72 Ma. At the regional scale, this heterogeneous cooling is coeval with subsidence of Late Cretaceous marine basin(s) that unconformably covered the Early Cretaceous (130–110 Ma) thrust system from 100 Ma. Thrusting resumed at 70 Ma in the AVAZ and migrated across Pelagonia to reach the External Hellenides at 40–38 Ma. Renewed thrusting in Pelagonia is attested at 68 Ma by abrupt and rapid cooling below 240 °C and erosion of the gneissic rocks. ZFT and AFT in western and eastern Pelagonia, respectively, testify at ~40 Ma to the latest thermal imprint related to thrusting. Central-eastern Pelagonia cooled rapidly and uniformly from 240 to 80 °C between 24 and 16 Ma in the footwall of a major extensional fault. Extension started even earlier, at ~33 Ma in the western AVAZ. Post-7 Ma rapid cooling is inferred from inverse modeling of AFT lengths. It occurred while E–W normal faults were cutting Pliocene-to-recent sediment.

scholarly journals Polyphase evolution of Pelagonia (northern Greece) revealed by geological and fission-track data

2014 ◽  
Vol 6 (2) ◽  
pp. 3075-3109 ◽  
Author(s):  
F. L. Schenker ◽  
M. G. Fellin ◽  
J.-P. Burg
Keyword(s):  
Early Cretaceous ◽  
Late Cretaceous ◽  
Fission Track ◽  
Regional Scale ◽  
Normal Faults ◽  
Recent Sediment ◽  
Northern Greece ◽  
Rapid Cooling ◽  
Basement Rocks ◽  
Fission Track Ages

Abstract. The Pelagonian zone, between the External Hellenides/Cyclades to the west and the Axios/Vardar/Almopia zone (AVAZ) and Rhodope to the east, was involved in late Early Cretaceous and in Late Cretaceous-Eocene orogenic events whose duration are still controversial. This work constrains their late thermal imprints. New and previously published zircon (ZFT) and apatite (AFT) fission-track ages show cooling below 240°C of the metamorphic western AVAZ imbricates between 102 and 93–90 Ma, of northern Pelagonia between 86 and 68 Ma, of the eastern AVAZ at 80 Ma and of western Rhodope at 72 Ma. At the regional scale, this heterogeneous cooling is coeval with subsidence of Late Cretaceous marine basin(s) that unconformably covered since 100 Ma the Early Cretaceous (130–110 Ma) thrust system. Thrusting restarted at 70 Ma in the AVAZ and migrated across Pelagonia to reach the External Hellenides at 40–38 Ma. Renewed thrusting in Pelagonia is attested at 68 Ma by abrupt and rapid cooling below 240°C and erosion of the basement rocks. ZFT and AFT in western and eastern Pelagonia, respectively, set at 40 Ma the latest thermal imprint related to thrusting. Central-eastern Pelagonia cooled rapidly and uniformly from 240 to 80°C between 24 and 16 Ma in the footwall of a major extensional fault. Extension started even earlier, at 33 Ma in the western AVAZ. Post-7 Ma rapid cooling is inferred from inverse modeling of AFT lengths. It occurred while E–W normal faults were cutting Pliocene-to-recent sediment.

scholarly journals Deconstructing the Infrastructure: A Complex History of Diachronous Metamorphism and Progressive Deformation during the Late Cretaceous to Eocene in the Thor-Odin–Pinnacles Area of Southeastern British Columbia

2016 ◽  
Vol 43 (2) ◽  
pp. 103 ◽  
Author(s):  
Deanne Van Rooyen ◽  
Sharon D. Carr
Keyword(s):  
British Columbia ◽  
Late Cretaceous ◽  
Normal Fault ◽  
Columbia River ◽  
Metamorphic Rocks ◽  
High Grade ◽  
Basement Rocks ◽  
History Of ◽  
Complex Structural ◽  
Structural Levels

The Thor-Odin dome is a basement-cored tectonothermal culmination in southern British Columbia containing high-grade metamorphic rocks that were polydeformed in the Late Cretaceous to Eocene. The rocks south of the Thor-Odin dome that extend ca. 20 km to the Pinnacles culmination and Whatshan batholith comprise a heterogeneous tract of polydeformed medium- to high-grade metamorphic rocks and host the South Fosthall pluton near the base of the structural section. They lie in the footwall of the Columbia River fault (CRF) zone, a moderately east-dipping, ductile-brittle, normal fault that was active after ca. 55 Ma and reactivated periodically up to 30 Ma. This tract of rocks has been interpreted as a mid-crustal zone that was exhumed and cooled during Eocene extension or, alternatively, a mid-crustal channel that was bounded at the top by the CRF and was active during the Late Cretaceous to Eocene. However, the timing of metamorphism, deformation, anatexis in basement rocks, and intrusion of leucogranite plutons reveals that there are four tectonothermal domains within the tract that each experienced metamorphism, deformation and cooling at different times. These rocks record Cretaceous metamorphism and cooling in the upper structural levels and three stages of progressive metamorphism and penetrative deformation that migrated into deeper crustal levels in the Paleocene and Eocene producing a complex structural section that was exhumed in part due to motion on the Columbia River fault zone, and in part due to NE-directed transport over a basement ramp.RÉSUMÉLe dôme de Thor-Odin correspond à une culmination tectonothermique d’un noyau de socle dans le sud de la Colombie-Britannique renfermant des roches métamorphiques de haute intensité polydéformées entre le Crétacé supérieur et l’Éocène. Les roches au sud du dôme de Thor-Odin qui s’étendent sur environ 20 km jusqu’à la culmination des Pinnacles et du batholite de Whatshan sont constituées d’une bande hétérogène de roches polydéformées à faciès métamorphique d’intensité moyenne à élevée qui constitue l’encaissant du pluton de South Fosthall près de la base de la colonne structurale. Elles se trouvent dans l'éponte inférieure de la zone de faille de la rivière Columbia (CRF), une faille normale à pendage modéré vers l’est, ductile-fragile, qui a été active après 55 Ma environ et a été réactivée périodiquement jusqu'à 30 Ma. Cette bande de roches a été interprétée comme une zone de mi-croûte qui a été exhumée et a refroidi durant l’extension éocène ou alors comme un canal mi-crustal qui a été limité au sommet par la CRF, et qui a été actif de la fin du Crétacé jusqu’à l’Éocène. Toutefois, la chronologie du métamorphisme, de la déformation, de l’anatexie dans les roches du socle, et de l'intrusion de plutons de leucogranite, montre qu'il existe quatre domaines tectonothermiques pour chaque bande qui ont subit du métamorphisme, de la déformation et du refroidissement à différents moments. Ces roches exhibent un métamorphisme et un refroidissement crétacé dans les niveaux structuraux supérieurs et trois stades de métamorphisme progressif et de déformation pénétrative qui ont migré dans les niveaux crustaux profonds au Paléocène et à l’Eocène constituant ainsi une colonne structurale complexe qui a été exhumée en partie en raison du mouvement de la zone de faille de Columbia River, et en partie en raison du transport vers le N.-E. sur une rampe de socle.

Interpretation of isotopic ages and 87Sr/86Sr initial ratios for plutonic rocks in the Whitehorse map area, Yukon

1979 ◽  
Vol 16 (10) ◽  
pp. 1988-1997 ◽  
Author(s):  
Gregg W. Morrison ◽  
Colin I. Godwin ◽  
Richard L. Armstrong
Keyword(s):  
British Columbia ◽  
Oceanic Crust ◽  
Late Cretaceous ◽  
Canadian Cordillera ◽  
Initial Ratio ◽  
Eastern Margin ◽  
The North ◽  
Plutonic Complex ◽  
Coast Plutonic Complex ◽  
North American Craton

Sixteen new K–Ar dates and four new Rb–Sr isochrons help define four plutonic suites in the Whitehorse map area, Yukon. The Triassic(?) suite, defined on stratigraphic evidence, is the southern extension of the Yukon Crystalline Terrane and is correlative with plutonic suites in the Intermontane Belt in British Columbia. The mid-Cretaceous (~100 Ma) suite in the Intermontane Belt in the Whitehorse map area is time equivalent to plutonic suites in the Omineca Crystalline Belt to the east. Late Cretaceous (~70 Ma) and Eocene (~55 Ma) suites include volcanic and subvolcanic as well as plutonic phases and are correlative with continental volcano–plutonic suites near the eastern margin of the Coast Plutonic Complex. The predominance of the mid-Cretaceous suite in the Intermontane Belt in Whitehorse and adjacent map areas in Yukon and northern British Columbia suggests that this area has undergone posttectonic magmatism more characteristic of the Omineca Crystalline Belt than of the Intermontane Belt elsewhere in the Canadian Cordillera.87Sr/86Sr initial ratio determinations suggest that the southern extension of the Yukon Crystalline Terrane in the western part of the Whitehorse map area and in northern British Columbia includes Precambrian crust separated from the North American craton by Paleozoic oceanic crust of the Intermontane Belt.

Spatially overlapping episodes of deformation, metamorphism, and magmatism in the southern Omineca Belt, southeastern British Columbia

2018 ◽  
Vol 55 (1) ◽  
pp. 84-110 ◽  
Author(s):  
Ewan Russell Webster ◽  
David R.M. Pattison
Keyword(s):  
British Columbia ◽  
Early Cretaceous ◽  
Late Cretaceous ◽  
Middle Jurassic ◽  
Canadian Cordillera ◽  
Spatial Relationships ◽  
Metamorphic Belt ◽  
Facies Metamorphism ◽  
Contact Aureoles ◽  
Greenschist Facies Metamorphism

The southeastern Omineca Belt of the Canadian Cordillera preserves a record of overlapping Barrovian and Buchan metamorphism spanning 180–50 Ma. This paper documents the timing, character, and spatial relationships that define separate domains of Middle Jurassic, Early Cretaceous, and Late Cretaceous deformation and metamorphism, and the nature of the geological interfaces that exist between them. A domain of Early Jurassic deformation (D1) and regional greenschist-facies metamorphism (M1) is cross-cut by Middle Jurassic (174–161 Ma) intrusions. Associated contact aureoles are divided into lower pressure (cordierite-dominated; ∼2.5–3.3 kbar; 1 kbar = 100 MPa) and higher pressure (staurolite-bearing; 3.5–4.2 kbar) subtypes; contact metamorphic kyanite occurs rarely in some staurolite-bearing aureoles. Jurassic structures are progressively overprinted northwards by Early Cretaceous deformation and metamorphism (D2M2), manifested in a tightening of Jurassic structures, development of more pervasive ductile fabrics, and Barrovian metamorphism. The D2M2 domain is the southerly continuation of the 600 km long Selkirk–Monashee–Cariboo metamorphic belt. Mid-Cretaceous intrusions (118–90 Ma) were emplaced throughout the D2M2 domain, the earliest of which contain D2 fabrics, but cut M2 isograds. The D2M2 domain makes a continuous, southeasterly transition into a domain of Late Cretaceous regional Barrovian metamorphism and deformation (D3M3; 94–76 Ma). The interface between these two domains is obscured by the coaxial nature of the deformation and the apparent continuity of the metamorphic zones, resulting in a complex and cryptic interface. Similarities between the D3M3 domain and the Selkirk Crest of Idaho and Washington suggest that this domain is the northerly continuation of the northward-plunging Priest River Complex.

Superimposed low-grade metamorphism in the Mount Fisher area, southeastern British Columbia—implications for the East Kootenay orogeny

1982 ◽  
Vol 19 (3) ◽  
pp. 476-489 ◽  
Author(s):  
M. E. McMechan ◽  
R. A. Price
Keyword(s):  
British Columbia ◽  
Late Cretaceous ◽  
Rocky Mountains ◽  
Regional Metamorphism ◽  
Low Grade ◽  
Canadian Cordillera ◽  
Windermere Supergroup ◽  
Granitic Intrusion ◽  
Block Faulting ◽  
Middle Proterozoic

Middle Proterozoic (~1500–1350 Ma) Belt–Purcell strata exposed in the Purcell and southwestern Rocky Mountains were affected by at least three distinct episodes of deformation and regional metamorphism. The oldest episode (1300–1350 Ma) apparently terminated Belt–Purcell sedimentation and involved folding, regional metamorphism, and granitic intrusion. The second episode (800–900 Ma) occurred during deposition of the Windermere Supergroup and involved uplift, block faulting, and low-grade regional metamorphism. Mesozoic–Cenozoic metamorphism, deformation, and plutonism overprinted the results of the earlier deformation and metamorphism.Illite crystallinity and muscovite polymorph ratios indicate that Purcell strata in the Mount Fisher area are in the lower green-schist to prehnite–pumpellyite facies of regional metamorphism. In the Steeples and Fisher blocks this metamorphism is related to structures that formed during the Late Cretaceous – Paleocene deformation. However, in the Sand Creek block the regional metamorphism is related to the development of a spaced cleavage that is folded by a Late Cretaceous – Paleocene nappe. Regional considerations suggest that this cleavage formed during the 1300–1350 Ma episode of deformation and metamorphism.The "East Kootenay orogeny" as currently defined embraces the two older episodes of tectonism. It is proposed that the term East Kootenay orogeny be restricted to designate the 1300–1350 Ma episode and that the term "Goat River orogeny" designate the 800–900 Ma episode of tectonism. The East Kootenay and Goat River orogenies appear to be correlative with the Racklan and Hayhook orogenies recognized in the northern Canadian Cordillera.

Metamorphic rocks in the Antarctic Peninsula region

2008 ◽  
Vol 145 (5) ◽  
pp. 655-676 ◽  
Author(s):  
ANKE S. WENDT ◽  
ALAN P. M. VAUGHAN ◽  
ALEXANDER TATE
Keyword(s):  
Shear Zone ◽  
Antarctic Peninsula ◽  
Temperature Data ◽  
Metamorphic Rocks ◽  
Central Domain ◽  
Oblique Convergence ◽  
Gondwana Margin ◽  
Western Side ◽  
The Antarctic ◽  
Eastern Domain

AbstractThe distribution of metamorphic rocks in the Antarctic Peninsula region, new quantitative peak pressure–temperature data along the Antarctic Peninsula, and a literature review on the current knowledge of metamorphic conditions in the Antarctic Peninsula region have been compiled into a single metamorphic map. The pressure–temperature data for the Antarctic Peninsula indicate (1) burial of supracrustal rocks to low to mid-crustal depth along the eastern and western side of the Antarctic Peninsula and on some islands adjacent to the western side of the peninsula; (2) uplift of lower- to mid-crustal metamorphic rocks along major shear and fault zones; and (3) a reversed succession of metamorphic grades for the western domain of the Antarctic Peninsula region compared to the eastern domain along the Eastern Palmer Land Shear Zone (EPLSZ) of the Antarctic Peninsula. The metamorphic data are consistent with oblique convergence between Alexander Island (the Western Domain), Palmer Land (Central Domain) and the Gondwana margin (the Eastern Domain), supporting a model of (1) exhumation and shearing of the higher pressure rocks from central western (up to 9.4 kbar) and from northeast (7 kbar to 9 kbar) Palmer Land, (2) the exhumation and shearing of low to medium pressure rocks in western Palmer Land and along the Eastern Palmer Land Shear Zone, and (3) shallow burial and subsequent exhumation of sediments of the Gondwana margin along the Eastern Palmer Land Shear Zone. Based on the high-amphibolite grade rocks exposed in central western Palmer Land, our data also support earlier suggestions that the Eastern Palmer Land Shear Zone is the surface expression of a northwest- to west-dipping, deep-level, high-temperature crustal shear zone extending below the western part of the Central Domain of the Antarctic Peninsula.

40Ar/39Ar thermochronology of the Thor-Odin – Pinnacles area, southeastern British Columbia: tectonic implications of cooling and exhumation patterns

2016 ◽  
Vol 53 (10) ◽  
pp. 993-1009 ◽  
Author(s):  
D. van Rooyen ◽  
S.D. Carr
Keyword(s):  
British Columbia ◽  
Shear Zone ◽  
Late Cretaceous ◽  
Columbia River ◽  
Metamorphic Rocks ◽  
Structural Level ◽  
High Grade ◽  
Extensional Deformation ◽  
Structural Levels ◽  
Upper Boundary

The Thor-Odin dome is a basement-cored tectonothermal culmination in southern British Columbia, containing high-grade metamorphic rocks that were polydeformed during the Cordilleran orogenesis. A north–south 40Ar/39Ar thermochronology transect was carried out throughout a ∼7 km thick tilted section in the Thor-Odin dome and structurally overlying rocks to construct thermochronological histories using existing U–Pb geochronology data with new 40Ar/39Ar data and to determine the nature of the boundary between the dome and overlying rocks at Cariboo Alp. Hornblende cooling dates are ∼62–58 Ma at the highest structural level, ∼57–55 Ma in the middle, and ∼57–53 Ma at Cariboo Alp on the upper boundary of the dome. Muscovite and biotite cooling dates are ∼53–50.5 Ma; identical throughout the dome, margin, and overlying panel. The Cariboo Alp area separating the Thor-Odin dome from overlying rocks did not accommodate major post-cooling extensional deformation; rather, it is a Late Cretaceous to Paleocene compressional shear zone. These domains cooled at different rates from >700 to ca. 300 °C, with upper structural levels cooling at rates of ca. 20 °C/Ma and the lowest levels at rates in excess of 120 °C/Ma. All levels passed through the closure temperature for argon in biotite (here calculated to be 320–330 °C) together at ca. 52–51 Ma. Differential cooling rates are the result of interaction between northeast-directed compressional transport of rocks towards the foreland of the orogen overlapping with activity on the Columbia River fault zone, reflecting crustal-scale extension that reached a peak in the Eocene.

scholarly journals Late Cretaceous – Early Palaeogene inversion-related tectonic structures at the NE margin of the Bohemian Massif (SW Poland and northern Czechia)

2021 ◽  
Author(s):  
Andrzej Głuszyński ◽  
Pawel Aleksandrowski
Keyword(s):  
Late Cretaceous ◽  
Bohemian Massif ◽  
Wide Spectrum ◽  
Regional Scale ◽  
Crystalline Basement ◽  
Underground Mines ◽  
Normal Faults ◽  
Tectonic Structures ◽  
The North ◽  
Sedimentary Fill

Abstract. A brief, regional-scale review of the Late Cretaceous – Early Palaeogene inversion-related tectonic structures affecting the Sudetes and their foreland at the NE margin of the Bohemian Massif is presented and complemented with results of new seismic studies. The Sudetes expose Variscan-deformed basement, partly overlain by post-orogenic Permo-Mesozoic cover, containing a wide spectrum of tectonic structures, both brittle and ductile, in the past in this area referred to as young Saxonian or Laramide. We have used newly reprocessed legacy seismics to study these structures at the two main post-Variscan structural units of the area, the North-Sudetic and Intra-Sudetic synclinoria, and discuss the results together with regionally-distributed examples coming from quarries and underground mines as well as those from the literature. The Late Cretaceous – Early Palaeogene tectonic structures in consecutively reviewed Sudetic tectonic units, from the north to south, typically include gentle to moderate buckle folds of detachment type or fault-related, high-angle reverse and normal faults, as well as low-angle thrusts – often rooted in the crystalline basement. The structures hitherto described as grabens, are frequently believed to be bounded by reverse faults (hence we use the term ‘reverse grabens’) and typically reveal strongly synclinal pattern of their sedimentary fill. The crystalline basement top, as imaged by seismic sections in the North Sudetic Synclinorium below the detachment-folded cover, is synformally down-warped with a wavelength of up to 30 km, whereas on the elevated areas, where the basement top is exposed at the surface, it is up-warped (i.e. tectonically buckled). The reviewed compressional structures typically show an orientation fitting the regionally-known Late Cretaceous – Early Palaeogene tectonic shortening direction of NE-SW to NNE-SSW The same applies to the regional joint pattern, typically comprising an orthogonal system of steep joints of c. NW-SE and NE-SW strikes. All the reviewed structures are considered as due to the Late Cretaceous – Early Palaeogene tectonic shortening episode, although some of the discussed faults with a strike-slip component of motion may have been modified, or even produced, by later, Late Cenozoic, tectonism.

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