Fabric evolution at basement–cover interfaces in a fold-and-thrust belt and implications for décollement tectonics (Autochthon, Lower Allochthon, central Scandinavian Caledonides)

Angerer, Thomas; Greiling, Reinhard O.

doi:10.1007/s00531-012-0765-4

Cited by 7 publications

(2 citation statements)

References 92 publications

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“…The overlying Sjoutälven Group comprises the Långmarkberg (S5, 50 m) and Gärdsjön (S6, 280 m) formations, overlain by the Tåsjön Group (Fjällbränna Formation, S7, 80 m; Gayer & Greiling, 1989; Kumpulainen & Greiling, 2011). These were deformed by E- to ESE-directed thrusting during anchizone to epizone metamorphism (Gayer & Greiling, 1989; Bierlein & Greiling, 1993; Warr, Greiling & Zachrisson, 1996; Angerer & Greiling, 2012). Gayer & Greiling (1989) estimated a bulk 50% shortening.…”

Section: Orogenic Transectsmentioning

confidence: 99%

“…Brittle imbrication in the Lower Allochthon, mostly with thrust shortening of <60% (Chapman, Gayer & Williams, 1985; Hossack, Garton & Nickelsen, 1985; Morley, 1986, 1987 a , 1987 b ; Townsend et al 1986; Gayer & Greiling, 1989; Townsend, Rice & Mackay, 1989; Bierlein & Greiling, 1993; Greiling, Gayer & Stephens, 1993) occurred during diagenetic zone to anchizone metamorphism (Kisch, 1980; Anderson, 1989; Rice et al 1989 a ; Warr, Greiling & Zachrisson, 1996; Angerer & Greiling, 2012).…”

Section: Scandinavian Caledonides Overviewmentioning

confidence: 99%

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Restoration of the external Scandinavian Caledonides

Rice

Anderson

2016

Geol. Mag.

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-Three models are evaluated for restoring basement rocks coring tectonic windows (WindowBasement) in the Scandinavian Caledonides; parautochthonous (Model I) and allochthonous (models II/III), with initial imbrication of the Window-Basement post-dating or pre-dating, respectively, that in the external imbricate zone (Lower Allochthon). In Model I, the Window-Basement comes from the eastern margin of the basin now imbricated into the Lower Allochthon, while in models II/III it comes from the western margin. In Model II, the Window-Basement formed a basement-high between Tonian and Cryogenian sediments imbricated into the Middle and Lower allochthons; in Model III deposition of the Lower Allochthon sediments commenced in Ediacaran times. Balanced cross-sections and branch-line restorations of four transects (Finnmark-Troms, Västerbotten-Nordland, Jämtland-Trøndelag, Telemark-Møre og Romsdal) show similar restored lengths for the models in two transects and longer restorations for models II/III in the other transects. Model I can result in c. 280 km wide gaps in the restored Lower Allochthon, evidence for which is not seen in the sedimentology. The presence of <3 km thick alluvial-fan deposits at the base of the Middle Allochthon indicates proximal, rapidly uplifting basement during Tonian-Cryogenian periods, taken as the origin of the Window-Basement during thrusting in models II/III. Model I requires multiple changes in thrusting-direction and predicts major thrusts or back-thrusts, currently unrecognized, separating parts of the Lower Allochthon; neither are required in models II/III. Metamorphic data are consistent with models II/III. Despite considerable along-strike structural variability in the external Scandinavian Caledonides, models II/III are preferred for the restoration of the Window-Basement.

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Section: Orogenic Transectsmentioning

confidence: 99%

Section: Scandinavian Caledonides Overviewmentioning

confidence: 99%

Restoration of the external Scandinavian Caledonides

Rice

Anderson

2016

Geol. Mag.

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An early Cambrian post-rift basin within the Baltica–Iapetus passive margin (north-central Scandinavian Caledonides)

Greiling,

Kathol,

Kumpulainen

2023

Int J Earth Sci (Geol Rundsch)

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Field data from recent geological mapping over a major part of the north-central Scandinavian Caledonides combined with published information give a detailed view of early Cambrian basin successions, comprising the Gärdsjön formation (Gf; Jämtland supergroup) in the Lower Allochthon and autochthonous equivalents (Dividal Group). The Gf comprises ten units of sandstone and siltstone or mudstone (Gf I—X, > 300 m thick). Green siltstones with red layers (Gf VI, c. 521 to 519 Ma) and green–grey siltstones at the top (Gf X, c. 516.5 to 513.5 Ma) are regional key horizons. Gf V, VI, VII, IX, and X deposition may be related to eustatic events. Restoration of Caledonian shortening reveals a major “Hornavan-Vattudal basin” (HVB; > 330 km NW–SE, > 400 km NE-SW) between the Grong–Olden culmination in the S and the Akkajaure–Tysfjord culmination in the N. Published zircon ages imply the latter separated the HVB from those shed from the Timan orogen in the N. The eastern basin margin straddles the present Caledonian erosional margin. Basement highs identified here within the Nasafjället, Bångonåive, and Børgefjellet “basement” windows define the western margin. They separate the HVB from the outer shelf towards the Iapetus Ocean in the W. The onset of sedimentation is time-related with E–W extension at c. 544–534 Ma. NNE–SSW-directed extension occurs after c. 518 Ma, perhaps related with Timan late-orogenic extension. The HVB is distinctly younger (c. 535–513.5 Ma) than Rodinia break-up and Iapetus ocean formation (> 550 Ma), comparable with post-rift basins in inner parts of modern passive margins. Graphical Abstract

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A rock magnetic profile through the ejecta flap of the Lockne impact crater (central Sweden) and implications for the impact excavation process

Melero-Asensio

Martín-Hernández

Ormö

2015

Journal of Applied Geophysics

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The well-documented, well-preserved, and well-exposed Lockne crater is a reference crater for marine-target impact on Earth. To date, it has been subjected to 11 short core drillings and over 5000 outcrop descriptions, as well as several geophysical surveys. The rich data allows detailed analysis of the cratering and modification processes. A unique feature with Lockne is its pristine ejecta layer. The ejecta differs, however, from the typical text book example of a land target crater in that it, to great extent, is made up of relatively extensive, coherent ejecta flaps resting on a target surface with no structural rim uplift. However, little is known about the marine impact excavation process generating the flaps. Here, we provide a lithological description coupled with an analysis of the rock magnetic properties of the Lockne-9 core through the western, downrange ejecta flap. The 31.04m long drillcore shows ~23m of monomict (mafic) breccia overlying a ~5m thick mixed zone of breccia with fracture fill and matrix derived from Palaeozoic sedimentary target sequence (i.e. Lower Cambrian alum shale and conglomerate). The whole breccia package rests with sharp contact on the fractured, granitic basement. The conspicuous lithological and petrophysical differences between the overlying breccias and the basement suggest the former was transported as ejecta. The rock magnetic properties of the ejecta show a magnetic signal that must have existed before the impact event took place. Thus, during the cratering process the ejecta at the studied location was relocated en masse from the central part of the crater to form an ejecta flap, in contrast to the standard ballistic emplacement of individual particles in an ejecta curtain. Highlights:-Rock-magnetism reveals a high magnetisation zone of pre-impact nature -Petrophysical characterization and description of the Lockne-9 core (central Sweden) -Magnetic signal is dominated by magnetite/titanomagnetite -Comparisons of affected and non-affected samples suggest a quick flap formation Research Highlights INSIGHTS IN THE EJECTION PROCESS OF THE LOCKNE MARINE-TARGET IMPACT CRATER FROM ROCK MAGNETIC PROPERTIES IN THE LOCKNE-9 DRILL Abstract:The well-documented, well-preserved, and well-exposed Lockne crater is a reference crater for marine-target impact on Earth. To date, it has been subjected to 11 short core drillings and over 5000 outcrop descriptions, as well as several geophysical surveys. The rich data allows detailed analysis of the cratering and modification processes.A unique feature with Lockne is its pristine ejecta layer. The ejecta differs, however, from the typical text book example of a land target crater in that it, to great extent, is made up of relatively extensive, coherent ejecta flaps resting on a target surface with no structural rim uplift. However, little is known about the marine impact excavation process generating the flaps. Here, we provide a lithological description coupled with an analysis of the rock magnetic properties of the Lockne-9 c...

show abstract

Fabric evolution at basement–cover interfaces in a fold-and-thrust belt and implications for décollement tectonics (Autochthon, Lower Allochthon, central Scandinavian Caledonides)

Cited by 7 publications

References 92 publications

Restoration of the external Scandinavian Caledonides

Restoration of the external Scandinavian Caledonides

An early Cambrian post-rift basin within the Baltica–Iapetus passive margin (north-central Scandinavian Caledonides)

A rock magnetic profile through the ejecta flap of the Lockne impact crater (central Sweden) and implications for the impact excavation process

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