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Earthquake induced soft sediment deformation (seismites): new data from the Early Triassic Guryul Ravine section (Kashmir)


Leu, Marc; Baud, Aymon; Brosse, Morgane; Goudemand, Nicolas; Vennemann, Torsten; Meier, Maximiliano; Bhat, Ghulam; Bucher, Hugo (2014). Earthquake induced soft sediment deformation (seismites): new data from the Early Triassic Guryul Ravine section (Kashmir). Geophysical Research Abstracts:1.

Abstract

At the classical Guryul ravine section of Kashmir, the Permo-Triassic (P-T) boundary is located about 3 m above the base of the Khunamuh Formation. Brookfield et al. (2013) proposed that the deposits straddling the boundary between the Khunamuh Formation and the underlying, Permian Zewan Formation are Siberian Traps-induced seismites overlain by tsunamites. These deposits have been subject to a divergent re-interpretation by Krystyn et al. (2014), who rejected a Siberian-Traps origin.
Here, we report the discovery of highly contorted beds at the top of a 7 m. thick, thin-bedded, light beige nodular lime mudstone, a new lithological unit recorded in the Early Triassic Khunamuh Formation, 120 m above the top of the Zewan Formation. These contorted beds, about 1 m thick, are showing typical earthquake induced soft sediment deformations, similar to the latest Permian in the lower part of the section. This new nodular limestone is of early Spathian age as indicated by our conodont sampling and crops out at the base of a cliff-forming limestone interval named Niti Limestone throughout the Tethys Himalaya area since the 19th century.
It is interesting to note that both latest Permian and early Spathian seismites occur at a marked lithological change, i.e. a shift in the depositional settings. The latest Permian seismite occurs on a delta ramp with mixed quartzose sand, silt and shelly carbonate lenses, storm influenced deposits, followed by an abrupt contact with the overlying deeper, thin- bedded and siliceous clay mud turbidite deposits and rare lime mud lenses. The early Spathian one is intercalated at the top of a distal ramp nodular limestone deposits, just at the change to the shallower thick-bedded Niti limestone.
The latest Permian seismic activity coincides with a platform drowning during a transgressive phase and the early Spathian one occurred during a platform uplift, also during a transgressive phase. Both may conceivably have been driven by recurrent phases of syn-sedimentary block faulting of the northern Indian passive margin. In this, we agree with the conclusions of Krystyn et al. (2014) that any relation between the local occurrences of seismites-tsunamites and the eruption of the Siberian traps is unlikely.
Yet, we must keep in mind that both coincide also with global shifts in the geochemical, sedimentological, paleontological and climate records.

Abstract

At the classical Guryul ravine section of Kashmir, the Permo-Triassic (P-T) boundary is located about 3 m above the base of the Khunamuh Formation. Brookfield et al. (2013) proposed that the deposits straddling the boundary between the Khunamuh Formation and the underlying, Permian Zewan Formation are Siberian Traps-induced seismites overlain by tsunamites. These deposits have been subject to a divergent re-interpretation by Krystyn et al. (2014), who rejected a Siberian-Traps origin.
Here, we report the discovery of highly contorted beds at the top of a 7 m. thick, thin-bedded, light beige nodular lime mudstone, a new lithological unit recorded in the Early Triassic Khunamuh Formation, 120 m above the top of the Zewan Formation. These contorted beds, about 1 m thick, are showing typical earthquake induced soft sediment deformations, similar to the latest Permian in the lower part of the section. This new nodular limestone is of early Spathian age as indicated by our conodont sampling and crops out at the base of a cliff-forming limestone interval named Niti Limestone throughout the Tethys Himalaya area since the 19th century.
It is interesting to note that both latest Permian and early Spathian seismites occur at a marked lithological change, i.e. a shift in the depositional settings. The latest Permian seismite occurs on a delta ramp with mixed quartzose sand, silt and shelly carbonate lenses, storm influenced deposits, followed by an abrupt contact with the overlying deeper, thin- bedded and siliceous clay mud turbidite deposits and rare lime mud lenses. The early Spathian one is intercalated at the top of a distal ramp nodular limestone deposits, just at the change to the shallower thick-bedded Niti limestone.
The latest Permian seismic activity coincides with a platform drowning during a transgressive phase and the early Spathian one occurred during a platform uplift, also during a transgressive phase. Both may conceivably have been driven by recurrent phases of syn-sedimentary block faulting of the northern Indian passive margin. In this, we agree with the conclusions of Krystyn et al. (2014) that any relation between the local occurrences of seismites-tsunamites and the eruption of the Siberian traps is unlikely.
Yet, we must keep in mind that both coincide also with global shifts in the geochemical, sedimentological, paleontological and climate records.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Paleontological Institute and Museum
Dewey Decimal Classification:560 Fossils & prehistoric life
Date:August 2014
Deposited On:29 Jan 2015 10:11
Last Modified:08 Dec 2017 10:22
Publisher:Copernicus Publications
ISSN:1029-7006
Publisher DOI:https://doi.org/10.13140/2.1.2848.9600

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