Transtensional flanking structures

Mayrhofer, Franziska; Schöpfer, Martin; Adamuszek, Marta; Dąbrowski, Marcin; Grasemann, Bernhard

doi:10.1016/j.jsg.2022.104659

Cited by 4 publications

(4 citation statements)

References 73 publications

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“…Such a pattern contrasts with that in present day examples of the Zagros (Závada et al, 2021) in which transport is directed purely away from the feeder and stretching is parallel to the shearing direction. The origin of this cross-directed flow in the Wurzeralm could relate to the lateral spreading of evaporite along its leading edge and transition from transpressional to transtensional flow (similar to that reported in velocity fields in glaciers; Mayrhofer et al, 2022) Notably, the orientation of structures measured in the units overlying the salt sheet are not aligned with shear directions in the evaporites but it is still likely that roof units were involved in deformation with the evaporites. As discussed above, the presence of a NE-SW fold trend in the Ruhpolding Fm that is absent in younger and older units possibly indicates the synsedimentary nature of deformation, potentially linked to instability atop the diapir and incipient salt sheet.…”

Section: Discussionmentioning

confidence: 54%

Emplacement and associated sedimentary record of the Jurassic submarine salt allochthon of the Wurzeralm (Eastern Alps, Austria)

Kurz,

Fernandez,

Eggerth

et al. 2023

Preprint

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A fossil salt sheet emplaced in the Jurassic in submarine conditions is described in the Eastern Alps of Austria, providing unique insights into the emplacement of similar submarine structures and their potential control on depositional systems. The salt sheet is a plug-fed extrusion emplaced due to squeezing of a salt diapir under compression. The preserved mylonitic shear fabric in the evaporites indicates radial, south-directed emplacement of the salt sheet. Tectono-sedimentary relationships record the evolution of the salt structure, from initial diapiric growth, to salt sheet extrusion and posterior collapse. Syn-extrusion sediments record the variable bathymetry of the extruding salt sheet, with reefal carbonates building up on the crestal bulge while their deeper water equivalents accumulated on the extruding salt lobe. This is the first description of a salt allochthon still linked to its source diapir in the Eastern Alps.

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Section: Discussionmentioning

confidence: 54%

Emplacement and associated sedimentary record of the Jurassic submarine salt allochthon of the Wurzeralm (Eastern Alps, Austria)

Kurz,

Fernandez,

Eggerth

et al. 2023

Preprint

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“…Multiple lines of evidence suggest that the Pasterze Glacier can be characterised as a dying glacier. This evidence includes (i) disconnections of two of the three ice falls feeding the glacier from the ice field, (ii) rapid surface elevation loss of the snout as measured using LiDAR in previous studies (Avian et al, 2018), (iii) flow stagnation (Mayrhofer et al, 2022) and (iv) development of extensive lakes on top of the glacier tongue that could easily be mistaken for a proglacial lake (Kellerer-Pirklbauer et al, 2021). Accordingly, it is no exaggeration to refer to the sediment-landform assemblage of the present day Pasterze as its sedimentary deathmask.…”

Section: Discussionmentioning

confidence: 78%

“…In the following, a very simple overview of glacier surface structure is provided in terms of its influence on sediment-landform generation and as a repository for supraglacial sediment. Detailed structural glaciological analyses of the Pasterze Glacier, which are the subject of recently completed (Mayrhofer et al, 2022) and ongoing study, are beyond the scope of the present paper. Each of the following features can be observed on the geomorphological-sedimentological map shown in Figure 1.…”

Section: Geological Setting Glaciological Setting and Glacier Structurementioning

confidence: 99%

The sedimentological death mask of a dying glacier

Heron

Kettler

Wawra

et al. 2022

The Depositional Record

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The Pasterze is Austria's largest glacier, and it is experiencing rapid downwasting and retreat. A mosaic of complex sedimentary deposits has been produced in recent years which have not hitherto been studied, yet provide excellent lessons into the facies distribution expected from a dying valley glacier. In this paper, a new glaciological-geomorphological-geological map is presented for the glacier in July 2021. Freshly exposed (since 2018) tills and flutes constitute a subglacial sediment-landform assemblage. An ice-marginal sediment-landform assemblage comprises meltwater streams, a delta system and proglacial lake terrace deposits. The supraglacial assemblage, meanwhile, includes fossil englacial channel deposits revealed by ablation, together with debris bands, rockfall deposits and supraglacial channel deposits. Collectively, these sediment-landform assemblages constitute the building blocks of a dying glacier landsystem.

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“…foliation). Once rotated into the foliation flanking‐structures are no longer detectable (Mayrhofer et al., 2022). Such ‘leftover’ veins are often rather thin which is consistent with stretching during vein rotation ((1) in Figure 2g).…”

Section: Discussionmentioning

confidence: 99%

Eclogite dehydration and melt‐induced embrittlement at high‐pressure conditions

Rogowitz,

Schorn,

Huet

2024

Terra Nova

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We document the complex interaction between metamorphic reactions and deformation behaviour at high‐pressure conditions by combining (micro‐) structural, petrographical and geochemical data from an eclogite body. The well‐equilibrated eclogite fabric is crosscut by mineral veins. Precipitated veins host the eclogitic high‐pressure assemblage with variation in modal composition, indicating that fracturing occurred at eclogite facies conditions. Deflection of the eclogite fabric adjacent to the veins implies ductile reactivation of the veins as flanking structures and strain localization under continuous aseismic shearing. In consequence, the reactivated veins are characterized by undulatory extinction and subgrain formation in quartz indicating crystal plasticity. We show that prograde post‐eclogitization metamorphism resulted in progressive dehydration and melting of the eclogite. Subsequent increase in pore‐pressure‐induced rock failure. The mesoscopic to microscopic characteristics of eclogite‐facies veins indicate a cyclic behaviour of fracturing, vein formation and crystal‐plasticity which demonstrates the strong interaction of chemical and mechanical processes operating at depth.

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Transtensional flanking structures

Cited by 4 publications

References 73 publications

Emplacement and associated sedimentary record of the Jurassic submarine salt allochthon of the Wurzeralm (Eastern Alps, Austria)

Emplacement and associated sedimentary record of the Jurassic submarine salt allochthon of the Wurzeralm (Eastern Alps, Austria)

The sedimentological death mask of a dying glacier

Eclogite dehydration and melt‐induced embrittlement at high‐pressure conditions

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