A structural analysis of a metamorphic fold–thrust belt, northeast Gagnon terrane, Grenville Province

1992 ◽  
Vol 29 (9) ◽  
pp. 1915-1927 ◽  
Author(s):  
Dennis Brown ◽  
Taoby Rivers ◽  
Tom Calon
Keyword(s):  
Deep Level ◽  
Greenschist Facies ◽  
Thrust Belt ◽  
Structural Elements ◽  
Thrust Sheet ◽  
Grenville Province ◽  
Lake Formation ◽  
Transport Direction ◽  
Tectonic Transport ◽  
Thrust Sheets

Northeast Gagnon terrane is located within the Parautochthonous Belt of the Grenville Orogen, near the projected intersection of the front zones of the Grenville and New Quebec orogens. The area consists principally of supracrustal units of the Early Proterozoic Knob Lake Group, and a newly recognized unit, the Equus Lake formation. Both are intruded by the Middle Proterozoic Shabogamo gabbro. Structural elements in the rocks record evidence of a polyorogenic history that is attributed to both the ca. 1800 Ma Hudsonian and the ca. 1000 Ma Grenvillian orogenies. This paper is concerned with the latter.Grenvillian deformation resulted in the formation of a relatively deep-level fold–thrust belt. Three thrust sheets can be defined on the basis of basal thrusts, variations in morphology and orientation of structural elements, and internal thrust sheet geometry. The polydeformational style of the area, rotation of fold axes into subparallelism with the tectonic transport direction, and internal imbrication lead to a complex internal thrust sheet geometry. Thrusting has produced and inverted the metamorphic gradient, with lower greenschist facies in the basal thrust sheet and upper greenschist facies in the upper thrust sheet.Documentation of the northeastern margin of Gagnon terrane as a north- to northwest-directed metamorphic fold–thrust belt corroborates similar interpretations for Gagnon terrane from elsewhere along the Grenville Front and is in accord with the models of the Grenville Province as a collisional orogen. Furthermore, it is suggested that northeast Gagnon terrane is an exhumed, internal, ductile part of a fold–thrust belt.

scholarly journals Examining the tectono-stratigraphic architecture, structural geometry, and kinematic evolution of the Himalayan fold-thrust belt, Kumaun, northwest India

Lithosphere ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 414-435 ◽  
Author(s):  
Subhadip Mandal ◽  
Delores M. Robinson ◽  
Matthew J. Kohn ◽  
Subodha Khanal ◽  
Oindrila Das
Keyword(s):  
Cross Section ◽  
Structural Model ◽  
Kinematic Model ◽  
Thrust Belt ◽  
Main Central Thrust ◽  
Thrust Sheet ◽  
Balanced Cross Section ◽  
Kinematic Evolution ◽  
Thrust Sheets ◽  
Northwest India

Abstract Existing structural models of the Himalayan fold-thrust belt in Kumaun, northwest India, are based on a tectono-stratigraphy that assigns different stratigraphy to the Ramgarh, Berinag, Askot, and Munsiari thrusts and treats the thrusts as separate structures. We reassess the tectono-stratigraphy of Kumaun, based on new and existing U-Pb zircon ages and whole-rock Nd isotopic values, and present a new structural model and deformation history through kinematic analysis using a balanced cross section. This study reveals that the rocks that currently crop out as the Ramgarh, Berinag, Askot, and Munsiari thrust sheets were part of the same, once laterally continuous stratigraphic unit, consisting of Lesser Himalayan Paleoproterozoic granitoids (ca. 1850 Ma) and metasedimentary rocks. These Paleoproterozoic rocks were shortened and duplexed into the Ramgarh-Munsiari thrust sheet and other Paleoproterozoic thrust sheets during Himalayan orogenesis. Our structural model contains a hinterland-dipping duplex that accommodates ∼541–575 km or 79%–80% of minimum shortening between the Main Frontal thrust and South Tibetan Detachment system. By adding in minimum shortening from the Tethyan Himalaya, we estimate a total minimum shortening of ∼674–751 km in the Himalayan fold-thrust belt. The Ramgarh-Munsiari thrust sheet and the Lesser Himalayan duplex are breached by erosion, separating the Paleoproterozoic Lesser Himalayan rocks of the Ramgarh-Munsiari thrust into the isolated, synclinal Almora, Askot, and Chiplakot klippen, where folding of the Ramgarh-Munsiari thrust sheet by the Lesser Himalayan duplex controls preservation of these klippen. The Ramgarh-Munsiari thrust carries the Paleoproterozoic Lesser Himalayan rocks ∼120 km southward from the footwall of the Main Central thrust and exposed them in the hanging wall of the Main Boundary thrust. Our kinematic model demonstrates that propagation of the thrust belt occurred from north to south with minor out-of-sequence thrusting and is consistent with a critical taper model for growth of the Himalayan thrust belt, following emplacement of midcrustal Greater Himalayan rocks. Our revised stratigraphy-based balanced cross section contains ∼120–200 km greater shortening than previously estimated through the Greater, Lesser, and Subhimalayan rocks.

scholarly journals Thrust tectonics in the Wetterstein and Mieming mountains, and a new tectonic subdivision of the Northern Calcareous Alps of Western Austria and Southern Germany

2021 ◽  
Author(s):  
Hugo Ortner ◽  
Sinah Kilian
Keyword(s):  
Eastern Alps ◽  
Northern Calcareous Alps ◽  
Main Body ◽  
Thrust Belt ◽  
Southeastern Part ◽  
Thrust Sheet ◽  
Northern Calcareous ◽  
Lateral Contact ◽  
Thrust Tectonics ◽  
Thrust Sheets

AbstractWe investigate the tectonic evolution of the Wetterstein and Mieming mountains in the western Northern Calcareous Alps (NCA) of the European Eastern Alps. In-sequence NW-directed stacking of thrust sheets in this thin-skinned foreland thrust belt lasted from the Hauterivian to the Cenomanian. In the more internal NCA major E-striking intracontinental transform faults dissected the thrust belt at the Albian–Cenomanian boundary that facilitated ascent of mantle melts feeding basanitic dykes and sills. Afterwards, the NCA basement was subducted, and the NCA were transported piggy-back across the tectonically deeper Penninic units. This process was accompanied by renewed Late Cretaceous NW-directed thrusting, and folding of thrusts. During Paleogene collision, N(NE)-directed out-of-sequence thrusts developed that offset the in-sequence thrust. We use this latter observation to revise the existing tectonic subdivision of the western NCA, in which these out-of-sequence thrusts had been used to delimit nappes, locally with young-on-old contacts at the base. We define new units that represent thrust sheets having exclusively old-on-young contacts at their base. Two large thrust sheets build the western NCA: (1) the tectonically deeper Tannheim thrust sheet and (2) the tectonically higher Karwendel thrust sheet. West of the Wetterstein and Mieming mountains, the Imst part of the Karwendel thrust sheet is stacked by an out-of-sequence thrust onto the main body of the Karwendel thrust sheet, which is, in its southeastern part, in lateral contact with the latter across a tear fault.

A test of detailed Nd isotope mapping in the Grenville Province: delineating a duplex thrust sheet in the Kipawa–Mattawa region

2006 ◽  
Vol 43 (4) ◽  
pp. 421-432 ◽  
Author(s):  
M K Herrell ◽  
A P Dickin ◽  
W A Morris
Keyword(s):  
Shear Zone ◽  
Shear Zones ◽  
Data Sets ◽  
Aeromagnetic Data ◽  
Thrust Sheet ◽  
Grenville Province ◽  
Nd Isotope ◽  
Tectonic Model ◽  
Thrust Sheets ◽  
Archean Crust

Over sixty new neodymium model ages were determined on orthogneisses from the Kipawa–Mattawa region of the Grenville Province to refine previous Nd isotope mapping work in this area. The combined Nd data sets support a tectonic model involving three major thrust sheets in the Kipawa area, separated by major shear zones. The uppermost sheet is correlated with the Allochthonous Polycyclic Belt, represented in the study area by the Lac Watson nappe, along with two allochthonous klippen. These have Nd model ages < 1.8 Ga, consistent with previous work. Within the underlying Parautochthonous Belt, previous workers identified a second major shear zone, separating rocks with Archean and Proterozoic crystallization ages, respectively. These two thrust sheets also have distinct Nd isotope signatures. The lowermost sheet consists of metamorphosed but otherwise relatively pristine Archean crust with Nd model ages > 2.6 Ga, whereas the overlying sheet consists of magmatically reworked Archean parautochthon with model ages from 1.8–2.6 Ga. A residual magnetic-field map developed from aeromagnetic data was compared with the terrane boundaries determined from isotopic data. The aeromagnetic data accurately reflect the margin of relatively pristine Archean crust in the study area, but this boundary does not correspond to the Allochthon Boundary Thrust. Instead, this boundary resulted from downcutting of the basal shear zone of the allochthon. This caused décollement of the strongly reworked Archean parautochthon to generate a duplex thrust sheet that was transported northwestwards over pristine Archean crust.

scholarly journals U-Pb dates measured in fracture-filling calcites from the SE Pyrenees: syn- or post-kinematic mineral growth?

2021 ◽  
Author(s):  
David Cruset ◽  
Jaume Vergés ◽  
Anna Tarvé
Keyword(s):  
Fluid Flow ◽  
Foreland Basin ◽  
Strike Slip ◽  
Normal Faults ◽  
Thrust Sheet ◽  
Tectonic Transport ◽  
Thrust Sheets ◽  
Interparticle Porosity ◽  
Clumped Isotope ◽  
Geochemical Analyses

&lt;p&gt;Recently, U-Pb dating of fracture-filling carbonates has revealed as a powerful tool to constrain the absolute timing of deformation in fold and thrust belts. However, geochronological studies of these minerals have to be combined with petrological observations and geochemical analyses to decipher if measured dates document fluid flow synchronously to deformation or post-kinematic events.&lt;/p&gt;&lt;p&gt;The Pyrenean compressional belt formed from Late Cretaceous to Oligocene due to the stacking of three thrust sheets and a deformed foreland basin. From top-and-older to bottom-and-younger, these consist of the B&amp;#243;ixols-Upper Pedraforca, Lower Pedraforca and Cad&amp;#237; thrust sheets and the Ebro foreland basin. Here, we quantify the duration of thrust sheet emplacement and shortening rates in the SE Pyrenees using U-Pb dating of 43 calcites filling fractures and interparticle porosity.&lt;/p&gt;&lt;p&gt;Four fracture sets related to compressional tectonics and one set related to extension are identified. The compressive sets include: 1) N-S, NNW-SSE and NNE-SSW trending veins; 2) E-W trending folding-related veins; 3) E-W trending reverse faults; and 4) NW-SE and NE-SW trending strike-slip faults. Fractures related to extension are NNW-SSE and NW-SE trending normal faults.&lt;/p&gt;&lt;p&gt;Elongated blocky, blocky and bladed calcite textures of the dated cements are observed. Elongated textures are observed in reverse, strike-slip and normal faults and occasionally in N-S, NNW-SSE and NNE-SSW and E-W veins. In these fractures, calcite crystals are arranged parallel, oblique, or perpendicular to fracture walls and provide evidence for syn-kinematic growth. Blocky and bladed textures have been identified in N-S, NNW-SSE and NNE-SSW veins, E-W folding-related veins, reverse and strike-slip faults and in calcite precipitated between sedimentary breccia clasts. Although these textures indicate precipitation after vein opening or at lower rates than vein opening, their presence in crack-seal veins and in stepped slickensides also indicates syn-kinematic growth. Moreover, clumped isotope temperatures measured in several blocky and bladed calcites precipitated in veins and faults indicate that most of them precipitated from fluids in thermal disequilibrium with host rocks, revealing rapid fluid flow and precipitation just after fracturing. Contrarily, low temperatures measured in blocky and bladed calcite precipitated in the interparticle porosity of sedimentary breccias indicate late fluid migration.&lt;/p&gt;&lt;p&gt;U-Pb dating applied to fracture-filling calcites in the SE Pyrenean fold and thrust belt yielded 46 ages from 70.6 &amp;#177; 0.9 Ma to 2.8 &amp;#177; 1.8 Ma (Cruset et al., 2020). The results reveal minimum durations for the emplacement of each thrust sheet (18.7 Myr for the B&amp;#243;ixols-Upper Pedraforca, 11.6 Myr for the Lower Pedraforca and 14.3 Myr for the Cad&amp;#237;), and that piggy-back thrusting was accompanied by post-emplacement deformation of upper thrust units above the lower ones during tectonic transport. These estimated durations, combined with the minimum shortening established for the B&amp;#243;ixols-Upper Pedraforca, Lower Pedraforca and Cad&amp;#237; thrust sheets by other methods, allows calculating shortening rates of 0.6 mm/yr, 3.1 mm/yr and 1.1 mm/yr, respectively. Finally, the results also reveal the development of local normal faults at late Oligocene times during the final stages of compression and exhumation.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;References:&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Cruset et al. (2020)&lt;/strong&gt;. Geological Society of London. 177, 1186-1196.&lt;/p&gt;

scholarly journals Tectonic Transport Directions, Shear Senses and Deformation Temperatures Indicated by Quartz c-Axis Fabrics and Microstructures in a NW-SE Transect across the Moine and Sgurr Beag Thrust Sheets, Caledonian Orogen of Northern Scotland

Geosciences ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 411
Author(s):  
Richard D. Law ◽  
J Ryan Thigpen ◽  
Sarah E. Mazza ◽  
Calvin A. Mako ◽  
Maarten Krabbendam ◽  
...  
Keyword(s):  
East Coast ◽  
Published Data ◽  
Metasedimentary Rocks ◽  
Edge Field ◽  
Transport Direction ◽  
Tectonic Transport ◽  
Thrust Sheets ◽  
Extension Direction ◽  
Structural Levels ◽  
Normal Sense

Moine metasedimentary rocks of northern Scotland are characterized by arcuate map patterns of mineral lineations that swing progressively clockwise from orogen-perpendicular E-trending lineations in greenschist facies mylonites above the Moine thrust on the foreland edge of the Caledonian Orogen, to S-trending lineations at higher structural levels and metamorphic grades in the hinterland. Quartz c-axis fabrics measured on a west to east coast transect demonstrate that the lineations developed parallel to the maximum principal extension direction and therefore track the local tectonic transport direction. Microstructures and c-axis fabrics document a progressive change from top to the N shearing in the hinterland to top to the W shearing on the foreland edge. Field relationships indicate that the domain of top to the N shearing was at least 55 km wide before later horizontal shortening on km-scale W-vergent folds that detach on the underlying Moine thrust. Previously published data from the Moine thrust mylonites demonstrate that top to the W shearing had largely ceased by 430 Ma, while preliminary isotopic age data suggest top to the N shearing occurred at ~470–450 Ma. In addition, data from the east coast end of our transect indicate normal-sense top down-SE shearing at close to peak temperatures at ~420 Ma that may be related to the closing stages of Scandian deformation, metamorphism and cooling/exhumation.

Thrust tectonics on Brøggerhalvøya and their relationship to the Tertiary West Spitsbergen Fold-and-Thrust Belt

2002 ◽  
Vol 139 (1) ◽  
pp. 47-72 ◽  
Author(s):  
K. SAALMANN ◽  
F. THIEDIG
Keyword(s):  
Middle Eocene ◽  
Kinematic Model ◽  
Thrust Belt ◽  
Fold Belt ◽  
Kinematic Evolution ◽  
Fold And Thrust Belt ◽  
Thrust Tectonics ◽  
Tectonic Transport ◽  
Thrust Sheets ◽  
West Spitsbergen

The Tertiary fold-and-thrust belt on Brøggerhalvøya is characterized by a NE-vergent pile of nine thrust sheets. The sole thrust of the pile is located in Precambrian phyllites and climbs up-section to the northeast. Four lower thrust sheets consisting predominantly of Upper Palaeozoic sediments are overlain by two thrust sheets in the central part of the stack which contain a kilometre-scale syncline and anticline. The fold is cut by juxtaposed thrusts giving rise to the formation of three structurally higher basement-dominated thrust sheets. A multiple-stage kinematic model is proposed including (1) in-sequence foreland-propagating formation of the lower thrust sheets in response to N–S subhorizontal bedding-parallel movements, (2) a change in tectonic transport to ENE and out-of-sequence thrusting and formation of the kilometre-scale fold-structure followed by (3) truncation of the kilometre-scale fold and stacking of the highest basement-dominated thrust sheets by hind-ward-propagating out-of-sequence thrusting. The strain of the thrust sheets is predominantly compressive with the exception of the structurally highest thrust sheets, reflecting a temporal change to a more transpressive regime. Thrusting was followed by (4) N–S extension and (5) W–E extension. Comparison of the structural geometry and kinematic evolution of Brøggerhalvøya with the data reported for the fold belt further south allows us to assume a coeval evolution with the fold belt. A latest Paleocene/Early Eocene age for the main phase of thrusting is suggested for the West Spitsbergen Fold-and-Thrust Belt; the main phases therefore pre-date the separation of Svalbard and Greenland due to right-lateral movements along the Hornsund Fault Zone. The fold belt's temporal evolution followed by the formation of the Forlandsundet Graben can be linked with the plate-kinematic framework in the span between latest Paleocene and Middle Eocene times.

scholarly journals The Caledonian thin-skinned thrust belt of Kronprins Christian Land, eastern North Greenland

2004 ◽  
Vol 6 ◽  
pp. 41-56 ◽  
Author(s):  
A.K. Higgins ◽  
N.J. Soper ◽  
M. Paul Smith ◽  
Jan A. Rasmussen
Keyword(s):  
Passive Margin ◽  
Thrust Belt ◽  
Thrust Sheet ◽  
East Greenland ◽  
Total Displacement ◽  
Thrust Sheets ◽  
Extreme North ◽  
North Greenland

Kronprins Christian Land in the extreme north of the East Greenland Caledonides, exposes a thin-skinned thrust belt up to 50 km wide developed in Ordovician–Silurian platform limestones and dolostones of the Iapetus passive margin. This thrust belt is characterised by a series of SSW–NNE-trending and east-dipping Caledonian thrusts with westward displacements of generally a few kilometres each. It passes westwards into undisturbed autochthonous foreland. Based on a line and area restoration, total displacement along a well-exposed WNW–ESE section through the thrust belt amounts to 17.6 km, which represents a shortening of 45% in the line of section. Biostratigraphic control in the limestone and dolostone succession is based on conodonts and macrofossils. The alteration colours of the conodonts provide estimates of maximum burial temperatures, which show that the thickness of the overlying thrust sheets ranged from about 6 to 12.5 km from west to east across the thrust belt. Since the estimated former thickness of the Vandredalen thrust sheet above the thin-skinned parautochthonous thrust belt is insufficient to yield the temperatures attained, higher thrust sheets must once have extended across the region.

scholarly journals Des​criptive text to the Geological map of Greenland, 1:500 000, Lambert Land, Sheet 9

2015 ◽  
pp. 1-29 ◽  
Author(s):  
Anthony K Higgins
Keyword(s):  
Early Carboniferous ◽  
Ground Moraine ◽  
Thrust Belt ◽  
Regional Survey ◽  
Thrust Sheet ◽  
East Greenland ◽  
Metasedimentary Rocks ◽  
The North ◽  
Thrust Sheets ◽  
Geological Map

The Lambert Land 1:500 000 scale geological map sheet covers a segment of the East Greenland Caledonian orogen extending between latitudes 78°–81°N and longitudes 13°–29°W. The region was geologically mapped in the summers of 1978–1980 and 1993–1995 as part of a regional Survey mapping programme, and the map sheet was printed in 2000. The region covered by the Lambert Land map sheet comprises a northern segment of the East Greenland Caledonides that is in thrust contact with the Caledonian foreland. The contact is an Edipping, NNE–SSW-trending thrust that runs through Kronprins Christian Land from west of Blåsø in the south to the region east of Sjælland Fjelde in the north. The Caledonian foreland succession is exposed in Mylius-Erichsen Land and Amdrup Højland on the west side of Danmark Fjord, and in western Kronprins Christian Land on the east side of Danmark Fjord. The several kilometre thick foreland succession ranges in age from Palaeoproterozoic to Silurian. In western Kronprins Christian Land the undeformed Ordovician–Silurian carbonates of the foreland pass eastwards into the so-called Thinskinned fold-and-thrust belt developed in the same strata that farther eastwards are structurally overlain by the allochthonous Vandredalen thrust sheet. This thrust sheet is in its turn overlain by a group of thrust sheets that make up the mountainous high ground of central parts of Kronprins Christian Land, and structurally form the so-called Western thrust belt; these rock units have a deeper crustal origin. In the extreme east the Nørreland thrust sheet is exposed in a coastal strip that comprises Palaeoproterozoic crystalline gneisses that include eclogite-facies enclaves and units of meta-igneous and metasedimentary rocks. Post-Caledonian rocks crop out in the north-eastern coastal parts of the map sheet area, and include sedimentary rocks of early Carboniferous to late Jurassic age that form part of the Wandel Sea Basin succession. Undifferentiated Quaternary deposits, ground moraine, alluvial fans and talus are distinguished where they obscure significant areas of bedrock.

Structural analysis of Bic fault, a thrust-related strike-slip fault of the external domain of the Taconic Orogen, Appalachians, Quebec, and metallogenic implications

1991 ◽  
Vol 28 (5) ◽  
pp. 788-799 ◽  
Author(s):  
P. Rhéaume ◽  
K. Schrijver
Keyword(s):  
Strike Slip ◽  
Strike Slip Fault ◽  
Thrust Sheet ◽  
Kink Bands ◽  
Strain Ellipsoid ◽  
Adjacent Part ◽  
External Domain ◽  
Dextral Strike Slip Fault ◽  
Thrust Sheets ◽  
Stage 1

The Bic fault is exposed along the shoreline of the St. Lawrence River, 21 km southwest of Rimouski, for 210 m at Cap à l'Orignal and for 100 m at Cap Enragé. The fault brings in contact two major thrust sheets, the Des Seigneuries and the Des Iles, Cambrian lithologies of the former overlying Ordovician rocks of the latter. In the Taconic Orogen, such contacts are normally thrust faults, but the Bic fault is a dextral strike-slip fault, striking east–west and dipping southward. A study of a narrow zone straddling the fault and an adjacent part of the Des Seigneuries thrust sheet has led to the recognition of four successive stages of deformation, all compatible with a northeast–southwest-trending strain ellipsoid. The two first stages are most important: stage 1 brought about regional folding and faulting, whereas stage 2 was characterized by the development of various structural elements (C–S fabrics, stretching lineation, Riedel shears, and kink bands) exclusive to the fault zone. We infer that (i) in the study area, the Bic fault constituted a lateral ramp along which the Des Seigneuries thrust sheet slid horizontally westward; and (ii) emplacement of Ba–Pb–Zn deposits took place slightly after this movement, probably during regional uplift of the orogen in Late Ordovician to Early Silurian time. The latter hypothesis tends to be corroborated by model lead ages of galena in two deposits.

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