Vestige of a subaerial rock avalanche deposit in an upper Cretaceous synorogenic wedge-top succession (Gosau Group, Eastern Alps)

Sanders, Diethard; Gruber, Alfred

doi:10.1016/j.sedgeo.2023.106378

Cited by 3 publications

(4 citation statements)

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“…4a and 4b, it can be seen that the density of the jigsaw structure in S4 is greater than that in S5. The jigsaw structures in S4 mostly display crackle or jigsaw fabric 35 , indicating very limited dilation and relative displacement after fragmentation, which is mainly characterized by shearing (Fig. 4c and e-f).…”

Section: Observations Of the Microstructuresmentioning

confidence: 99%

“…4c and e-f). Conversely, there are relatively few jigsaw structures in S5, with most displaying mosaic fabric 35 (Fig. 4d and g-i), indicating obvious dilation after fragmentation.…”

Section: Observations Of the Microstructuresmentioning

confidence: 99%

“…It can be seen that the sizes of most clasts in S2 are obviously larger than those in S6, which indicates that the fragmentation degree of S6 should be greater than that of S2. Moreover, the fragmented grains in S2 are still densely distributed, displaying a cracked or jigsaw fabric 35 , such as the fragmented grains near the left edge (Extended Data Fig. A5a).…”

Section: Declarationsmentioning

confidence: 99%

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Geological evidence: New insights into rock avalanche dynamics

Wang,

Chen,

Liu

et al. 2024

Preprint

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Rock avalanches (RAs) are among the most enigmatic geological processes on Earth and other planets, characterized by extremely high mobility1-7. Although great work has been conducted with many hypotheses being proposed8-19, the mechanism for its high mobility remains a challenging issue due to a lack of geological evidence20-21. Microscope observations and mineral analysis of the basal and body facies of the Nyixoi Chongco RA on the Tibetan Plateau, China, revealed that grains in the RA deform by brittle fracturing with the frictional temperatures ranging from 270 ~ 300 ℃. The basal facies features a dilated regime with a high fragmentation degree, but the body facies displays a dense regime with relatively low fragmentation, although their temperatures are similar. A jigsaw structure characterized by intense collision is observed in the basal facies but is lacking in the body facies. With these geological evidences, we propose that the frictional temperature of most RAs characterized by brittle fracturing should be low that cannot cause thermal decomposition or melt. A mechanism similar to the Leidenfrost effect should occur in the basal facies, which is related to landquakes and dominates the high mobility of RAs by the generation of a relatively dilated regime with the main mass propagating as a cataclastic flow.

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Section: Observations Of the Microstructuresmentioning

confidence: 99%

“…4c and e-f). Conversely, there are relatively few jigsaw structures in S5, with most displaying mosaic fabric 35 (Fig. 4d and g-i), indicating obvious dilation after fragmentation.…”

Section: Observations Of the Microstructuresmentioning

confidence: 99%

Section: Declarationsmentioning

confidence: 99%

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Geological evidence: New insights into rock avalanche dynamics

Wang,

Chen,

Liu

et al. 2024

Preprint

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“…Since the 19th century, the 'Gosau deposits' or the Gosau Group (middle Turonian to Ypresian; Wagreich and Faupl 1994) is known as the synorogenic wedge-top succession of the Eastern Alps. In consequence of a geohistory including stacking of thrust nappes, uplift and subaerial erosion, repeated transgressions over a differentiated morphological relief and, nally, deepening to bathyal to abyssal depths, the Gosau Group comprises an exceptionally wide spectrum of facies (e.g., Wagreich and Faupl 1994 Sanders and Gruber 2023). The lowermost portions of the onlapping Gosau successions, however, are only rarely well-exposed because they are commonly covered by scree, vegetation or glacigenic sediments.…”

Section: Introductionmentioning

confidence: 99%

Onlap of Upper Cretaceous synorogenic wedge-top deposits (Eastern Alps): Fragmentites, event beds, and coseismic deformation.

Sanders

2024

Preprint

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In synorogenic wedge-top basins of the Alps, the basal strata are rarely exposed. Herein, a late Turonian to early Coniacian succession above an older rock substrate is described that comprises: (a) proto-/cataclasites, (b) slope breccias, (c) fluvial conglomerates, and (d) low-energy lagoonal limestones with event beds. The proto-/cataclasites are a vestige of a fault damage zone. The distribution of the other facies records a hilly vegetated terrain drained by a stream and that, upon sea-level rise, became encroached by a lagoon. A section of 'lagoonal' limestones contains a thick event bed of angular dolostone pebbles to cobbles derived from the local substrate, and embedded in hybrid arenite. Bioclasts (rudists, corals, red algae) are from open-marine environments. Angular shape and a corrugated surface of lithoclasts suggest that they stem from slope mantles of subaerially exposed areas. The bed records an event of exceptional coastal flooding and is tentatively interpreted as a tsunami deposit. In the slope breccias, the fluvial conglomerates, and in the event beds, many lithoclasts became fractured in situinto crackle, jigsaw, and mosaic subclast fabrics; fractures are filled with the same material (lime mud to arenite) as that comprising the primary matrix. In-situ clast fracture was produced by coseismic shaking, i.e., these fabrics record syndepositional earthquakes. In the Meso-Cenozoic wedge-top succession of the Eastern Alps, features related to seismic activity and coastal inundation expectably are widespread, but to date were overgone or not identified as such.

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Geological evidences: New insights into rock avalanche dynamics

Wang,

Chen,

Liu

et al. 2024

Preprint

View full text Add to dashboard Cite

Rock avalanche (RA) is one of the most enigmatic geological processes on Earth and other planets featured by extremely high mobility1-7. Although great work has been conducted with many hypotheses being proposed8-19, the mechanism for its high mobility remains a challenging issue due to lacking geological evidence20-21. Microscope observations and mineral analysis of the basal and body facies of the Nyixoi Chongco RA on the Tibetan Plateau, China show that grains in the RA deform by brittle fracturing with a frictional temperature being 270 ~ 300 ℃. The basal facies is featured by a dilated regime with a high fragmentation degree, but the body facies displays a dense regime with a relatively low fragmentation although their temperatures are near. Jigsaw structure featured by intensive collision is observed in the basal facies but lacking in the body facies. With these geological evidences, it is reached that the frictional temperature of most RAs featured by brittle fracturing should be low that can not cause the occurrence of thermal decomposition or melt. A mechanism liking a leidenfrost effect should occur in the basal facies, which is related to landquake and dominates the high mobility of RAs by the generation of a relatively dilated regime with the main mass propagated as a cataclastic flow.

show abstract

Vestige of a subaerial rock avalanche deposit in an upper Cretaceous synorogenic wedge-top succession (Gosau Group, Eastern Alps)

Cited by 3 publications

References 94 publications

Geological evidence: New insights into rock avalanche dynamics

Geological evidence: New insights into rock avalanche dynamics

Onlap of Upper Cretaceous synorogenic wedge-top deposits (Eastern Alps): Fragmentites, event beds, and coseismic deformation.

Geological evidences: New insights into rock avalanche dynamics

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