Seismogenic slump folds formed by gravity-driven tectonics down a negligible subaqueous slope

G. Ian Alsop, Shmuel Marco

Research output: Contribution to journalArticle

54 Citations (Scopus)

Abstract

The Late Pleistocene Lisan Formation contains superb examples of soft-sediment deformation generated during gravity-driven slumping and failure down extremely gentle (< 1°) slopes towards the palaeo-Dead Sea Basin. Following a previously established framework, portions of individual slumps are broadly categorised into coherent, semi-coherent, and incoherent domains, reflecting increasing deformation and disarticulation of sediment. We present new structural data collected from each of these (overlapping) domains that demonstrate how the orientation of fold hinges and axial planes becomes more dispersed as slumps become increasingly incoherent. Such patterns are the reverse to that typically encountered in lithified rocks where increasing deformation results in clustering of linear elements towards the flow direction, and may reflect greater heterogeneity and disarticulation within slumps. Use of folds to determine palaeoslopes should therefore be limited to those from coherent slumps, where the opportunity for hinge dislocation and rotation is more limited. Within coherent and semi-coherent slumps, folds are reworked to create classic Type 1, 2 and 3 refold patterns during a single progressive deformation perhaps lasting just a matter of minutes. It is noteworthy that slump folds are typically lacking in smaller parasitic folds, implying that instantaneous development and/or limited viscosity contrasts have hindered the formation of second order folds. As deformation intensifies within semi-coherent to incoherent slumps, some fold hinges rotate towards the flow direction to create sheath folds. However, many fold hinges do not rotate into the flow direction, but rather roll downslope to form a new category of spiral folds. Extreme deformation may also generate semi-detached fold trains in which the short limbs of verging fold pairs are relatively thickened resulting in en-echelon X folds. The hinges of the sheared fold pair are reduced to apophyses, although these can still be used to infer original fold vergence. As observations are from a thin slumped system over a relatively small area, the variation in structural style from coherent to incoherent is attributed to increasing deformation.
Original languageEnglish
Pages (from-to)48-69
Number of pages22
JournalTectonophysics
Volume605
Early online date10 Apr 2013
DOIs
Publication statusPublished - 11 Oct 2013

Fingerprint

tectonics
hinges
gravity
gravitation
slopes
fold
sediments
slumping
limbs
sheaths
rocks
viscosity
dislocation
sediment
train
limb
Pleistocene

Keywords

  • slope failure
  • slump fold
  • sheath fold
  • soft sediment deformation
  • MTC
  • Dead Sea

Cite this

Seismogenic slump folds formed by gravity-driven tectonics down a negligible subaqueous slope. / Alsop, G. Ian; Marco, Shmuel.

In: Tectonophysics, Vol. 605, 11.10.2013, p. 48-69.

Research output: Contribution to journalArticle

@article{83bccd453ccf47e3a7c94cec5e7f087e,
title = "Seismogenic slump folds formed by gravity-driven tectonics down a negligible subaqueous slope",
abstract = "The Late Pleistocene Lisan Formation contains superb examples of soft-sediment deformation generated during gravity-driven slumping and failure down extremely gentle (< 1°) slopes towards the palaeo-Dead Sea Basin. Following a previously established framework, portions of individual slumps are broadly categorised into coherent, semi-coherent, and incoherent domains, reflecting increasing deformation and disarticulation of sediment. We present new structural data collected from each of these (overlapping) domains that demonstrate how the orientation of fold hinges and axial planes becomes more dispersed as slumps become increasingly incoherent. Such patterns are the reverse to that typically encountered in lithified rocks where increasing deformation results in clustering of linear elements towards the flow direction, and may reflect greater heterogeneity and disarticulation within slumps. Use of folds to determine palaeoslopes should therefore be limited to those from coherent slumps, where the opportunity for hinge dislocation and rotation is more limited. Within coherent and semi-coherent slumps, folds are reworked to create classic Type 1, 2 and 3 refold patterns during a single progressive deformation perhaps lasting just a matter of minutes. It is noteworthy that slump folds are typically lacking in smaller parasitic folds, implying that instantaneous development and/or limited viscosity contrasts have hindered the formation of second order folds. As deformation intensifies within semi-coherent to incoherent slumps, some fold hinges rotate towards the flow direction to create sheath folds. However, many fold hinges do not rotate into the flow direction, but rather roll downslope to form a new category of spiral folds. Extreme deformation may also generate semi-detached fold trains in which the short limbs of verging fold pairs are relatively thickened resulting in en-echelon X folds. The hinges of the sheared fold pair are reduced to apophyses, although these can still be used to infer original fold vergence. As observations are from a thin slumped system over a relatively small area, the variation in structural style from coherent to incoherent is attributed to increasing deformation.",
keywords = "slope failure, slump fold, sheath fold, soft sediment deformation, MTC , Dead Sea",
author = "Alsop, {G. Ian} and Shmuel Marco",
note = "We thank Mr. John Levy, together with the Carnegie Trust and the Royal Society of Edinburgh for travel grants to IA, and the Israel Science Foundation for grant 1539/08 to SM. SM also thanks the Department of Earth Sciences at Durham University for hosting a visit. Finally we thank Hugo Ortner, an anonymous referee, and Ivo Baron for providing detailed comments that helped clarify this paper.",
year = "2013",
month = "10",
day = "11",
doi = "10.1016/j.tecto.2013.04.004",
language = "English",
volume = "605",
pages = "48--69",
journal = "Tectonophysics",
issn = "0040-1951",
publisher = "Elsevier",

}

TY - JOUR

T1 - Seismogenic slump folds formed by gravity-driven tectonics down a negligible subaqueous slope

AU - Alsop, G. Ian

AU - Marco, Shmuel

N1 - We thank Mr. John Levy, together with the Carnegie Trust and the Royal Society of Edinburgh for travel grants to IA, and the Israel Science Foundation for grant 1539/08 to SM. SM also thanks the Department of Earth Sciences at Durham University for hosting a visit. Finally we thank Hugo Ortner, an anonymous referee, and Ivo Baron for providing detailed comments that helped clarify this paper.

PY - 2013/10/11

Y1 - 2013/10/11

N2 - The Late Pleistocene Lisan Formation contains superb examples of soft-sediment deformation generated during gravity-driven slumping and failure down extremely gentle (< 1°) slopes towards the palaeo-Dead Sea Basin. Following a previously established framework, portions of individual slumps are broadly categorised into coherent, semi-coherent, and incoherent domains, reflecting increasing deformation and disarticulation of sediment. We present new structural data collected from each of these (overlapping) domains that demonstrate how the orientation of fold hinges and axial planes becomes more dispersed as slumps become increasingly incoherent. Such patterns are the reverse to that typically encountered in lithified rocks where increasing deformation results in clustering of linear elements towards the flow direction, and may reflect greater heterogeneity and disarticulation within slumps. Use of folds to determine palaeoslopes should therefore be limited to those from coherent slumps, where the opportunity for hinge dislocation and rotation is more limited. Within coherent and semi-coherent slumps, folds are reworked to create classic Type 1, 2 and 3 refold patterns during a single progressive deformation perhaps lasting just a matter of minutes. It is noteworthy that slump folds are typically lacking in smaller parasitic folds, implying that instantaneous development and/or limited viscosity contrasts have hindered the formation of second order folds. As deformation intensifies within semi-coherent to incoherent slumps, some fold hinges rotate towards the flow direction to create sheath folds. However, many fold hinges do not rotate into the flow direction, but rather roll downslope to form a new category of spiral folds. Extreme deformation may also generate semi-detached fold trains in which the short limbs of verging fold pairs are relatively thickened resulting in en-echelon X folds. The hinges of the sheared fold pair are reduced to apophyses, although these can still be used to infer original fold vergence. As observations are from a thin slumped system over a relatively small area, the variation in structural style from coherent to incoherent is attributed to increasing deformation.

AB - The Late Pleistocene Lisan Formation contains superb examples of soft-sediment deformation generated during gravity-driven slumping and failure down extremely gentle (< 1°) slopes towards the palaeo-Dead Sea Basin. Following a previously established framework, portions of individual slumps are broadly categorised into coherent, semi-coherent, and incoherent domains, reflecting increasing deformation and disarticulation of sediment. We present new structural data collected from each of these (overlapping) domains that demonstrate how the orientation of fold hinges and axial planes becomes more dispersed as slumps become increasingly incoherent. Such patterns are the reverse to that typically encountered in lithified rocks where increasing deformation results in clustering of linear elements towards the flow direction, and may reflect greater heterogeneity and disarticulation within slumps. Use of folds to determine palaeoslopes should therefore be limited to those from coherent slumps, where the opportunity for hinge dislocation and rotation is more limited. Within coherent and semi-coherent slumps, folds are reworked to create classic Type 1, 2 and 3 refold patterns during a single progressive deformation perhaps lasting just a matter of minutes. It is noteworthy that slump folds are typically lacking in smaller parasitic folds, implying that instantaneous development and/or limited viscosity contrasts have hindered the formation of second order folds. As deformation intensifies within semi-coherent to incoherent slumps, some fold hinges rotate towards the flow direction to create sheath folds. However, many fold hinges do not rotate into the flow direction, but rather roll downslope to form a new category of spiral folds. Extreme deformation may also generate semi-detached fold trains in which the short limbs of verging fold pairs are relatively thickened resulting in en-echelon X folds. The hinges of the sheared fold pair are reduced to apophyses, although these can still be used to infer original fold vergence. As observations are from a thin slumped system over a relatively small area, the variation in structural style from coherent to incoherent is attributed to increasing deformation.

KW - slope failure

KW - slump fold

KW - sheath fold

KW - soft sediment deformation

KW - MTC

KW - Dead Sea

U2 - 10.1016/j.tecto.2013.04.004

DO - 10.1016/j.tecto.2013.04.004

M3 - Article

VL - 605

SP - 48

EP - 69

JO - Tectonophysics

JF - Tectonophysics

SN - 0040-1951

ER -