Morphometric analysis of plunge pools and sediment wave fields along western Great Bahama Bank

Jara S.D. Schnyder, Gregor P Eberli, Christian Betzler, Marco Wunsch, Sebastian Lindhorst, Linda Schiebel, Thierry Mulder, Emmanuelle Ducassou

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

A systematic assessment of morphometric parameters of over 200 plunge pools along the steep escarpment base of western Great Bahama Bank and ~ 2000km2 of sediment wave fields of upslope migrating cyclic steps documents the importance of cascading density currents for sedimentation on the slope. The abrupt downslope termination of the Holocene mud wedge with the cyclic steps shows that strike parallel bottom currents interacting with the off-bank currents are responsible for slope sediment distribution. The plunge pools and sediment waves were generated by density-cascading and both are related to a hydraulic jump caused by two gradient changes along the slope profile. The bedforms highlight both the erosional and depositional nature of this current regime, which is controlled by slope gradient and the directional confinement by either grooves on the steep escarpment or gullies on the middle to lower slope. The > 20 m deep plunge pools are ellipsoidal, with an average width of 211 m and length of 283 m, but variations between 80–360 m and 100–650 m for width and length occur. They are caused by an average gradient break of 16° on the cemented upper slope. Gradient breaks of as low as 2° are reported to be sufficient to scour a plunge pool like the ones in the study area, but higher gradient breaks between 10 and 20° are quite common for consistent plunge pool development. A second gradient break further down slope changes flow conditions for the generation of cyclic steps, with asymmetric waveforms of 4 m high (average) in large wave fields in the entire the study area. Orientation is mainly orthogonal to the main slope direction but wave lengths and sinuosity vary, depending on the morphologic location of the wave field. The comparison with sediment wave fields with similar geometries or in similar environments shows that flow reconstruction based on the wave height and wave length alone along with a characterization of sediment grain size, however, yields non-unique results and is site specific.

Original languageEnglish (US)
Pages (from-to)15-28
Number of pages14
JournalMarine Geology
Volume397
DOIs
StatePublished - Mar 1 2018

Fingerprint

sediment wave
wave field
Sediments
escarpment
Hydraulic jump
Wavelength
Scour
wavelength
Sedimentation
analysis
bottom current
bedform
Current density
wave height
gully
scour
density current
sediment
mud
grain size

Keywords

  • Carbonate slope
  • Cyclic steps
  • Density current
  • Great Bahama Bank
  • Multibeam bathymetry
  • Plunge pool
  • Sediment waves
  • Slope morphology
  • Supercritical flow conditions
  • Waveform

ASJC Scopus subject areas

  • Oceanography
  • Geology
  • Geochemistry and Petrology

Cite this

Schnyder, J. S. D., Eberli, G. P., Betzler, C., Wunsch, M., Lindhorst, S., Schiebel, L., ... Ducassou, E. (2018). Morphometric analysis of plunge pools and sediment wave fields along western Great Bahama Bank. Marine Geology, 397, 15-28. https://doi.org/10.1016/j.margeo.2017.11.020

Morphometric analysis of plunge pools and sediment wave fields along western Great Bahama Bank. / Schnyder, Jara S.D.; Eberli, Gregor P; Betzler, Christian; Wunsch, Marco; Lindhorst, Sebastian; Schiebel, Linda; Mulder, Thierry; Ducassou, Emmanuelle.

In: Marine Geology, Vol. 397, 01.03.2018, p. 15-28.

Research output: Contribution to journalArticle

Schnyder, JSD, Eberli, GP, Betzler, C, Wunsch, M, Lindhorst, S, Schiebel, L, Mulder, T & Ducassou, E 2018, 'Morphometric analysis of plunge pools and sediment wave fields along western Great Bahama Bank', Marine Geology, vol. 397, pp. 15-28. https://doi.org/10.1016/j.margeo.2017.11.020
Schnyder, Jara S.D. ; Eberli, Gregor P ; Betzler, Christian ; Wunsch, Marco ; Lindhorst, Sebastian ; Schiebel, Linda ; Mulder, Thierry ; Ducassou, Emmanuelle. / Morphometric analysis of plunge pools and sediment wave fields along western Great Bahama Bank. In: Marine Geology. 2018 ; Vol. 397. pp. 15-28.
@article{47971c3fd86c4cf480aa6d463552fda1,
title = "Morphometric analysis of plunge pools and sediment wave fields along western Great Bahama Bank",
abstract = "A systematic assessment of morphometric parameters of over 200 plunge pools along the steep escarpment base of western Great Bahama Bank and ~ 2000km2 of sediment wave fields of upslope migrating cyclic steps documents the importance of cascading density currents for sedimentation on the slope. The abrupt downslope termination of the Holocene mud wedge with the cyclic steps shows that strike parallel bottom currents interacting with the off-bank currents are responsible for slope sediment distribution. The plunge pools and sediment waves were generated by density-cascading and both are related to a hydraulic jump caused by two gradient changes along the slope profile. The bedforms highlight both the erosional and depositional nature of this current regime, which is controlled by slope gradient and the directional confinement by either grooves on the steep escarpment or gullies on the middle to lower slope. The > 20 m deep plunge pools are ellipsoidal, with an average width of 211 m and length of 283 m, but variations between 80–360 m and 100–650 m for width and length occur. They are caused by an average gradient break of 16° on the cemented upper slope. Gradient breaks of as low as 2° are reported to be sufficient to scour a plunge pool like the ones in the study area, but higher gradient breaks between 10 and 20° are quite common for consistent plunge pool development. A second gradient break further down slope changes flow conditions for the generation of cyclic steps, with asymmetric waveforms of 4 m high (average) in large wave fields in the entire the study area. Orientation is mainly orthogonal to the main slope direction but wave lengths and sinuosity vary, depending on the morphologic location of the wave field. The comparison with sediment wave fields with similar geometries or in similar environments shows that flow reconstruction based on the wave height and wave length alone along with a characterization of sediment grain size, however, yields non-unique results and is site specific.",
keywords = "Carbonate slope, Cyclic steps, Density current, Great Bahama Bank, Multibeam bathymetry, Plunge pool, Sediment waves, Slope morphology, Supercritical flow conditions, Waveform",
author = "Schnyder, {Jara S.D.} and Eberli, {Gregor P} and Christian Betzler and Marco Wunsch and Sebastian Lindhorst and Linda Schiebel and Thierry Mulder and Emmanuelle Ducassou",
year = "2018",
month = "3",
day = "1",
doi = "10.1016/j.margeo.2017.11.020",
language = "English (US)",
volume = "397",
pages = "15--28",
journal = "Marine Geology",
issn = "0025-3227",
publisher = "Elsevier",

}

TY - JOUR

T1 - Morphometric analysis of plunge pools and sediment wave fields along western Great Bahama Bank

AU - Schnyder, Jara S.D.

AU - Eberli, Gregor P

AU - Betzler, Christian

AU - Wunsch, Marco

AU - Lindhorst, Sebastian

AU - Schiebel, Linda

AU - Mulder, Thierry

AU - Ducassou, Emmanuelle

PY - 2018/3/1

Y1 - 2018/3/1

N2 - A systematic assessment of morphometric parameters of over 200 plunge pools along the steep escarpment base of western Great Bahama Bank and ~ 2000km2 of sediment wave fields of upslope migrating cyclic steps documents the importance of cascading density currents for sedimentation on the slope. The abrupt downslope termination of the Holocene mud wedge with the cyclic steps shows that strike parallel bottom currents interacting with the off-bank currents are responsible for slope sediment distribution. The plunge pools and sediment waves were generated by density-cascading and both are related to a hydraulic jump caused by two gradient changes along the slope profile. The bedforms highlight both the erosional and depositional nature of this current regime, which is controlled by slope gradient and the directional confinement by either grooves on the steep escarpment or gullies on the middle to lower slope. The > 20 m deep plunge pools are ellipsoidal, with an average width of 211 m and length of 283 m, but variations between 80–360 m and 100–650 m for width and length occur. They are caused by an average gradient break of 16° on the cemented upper slope. Gradient breaks of as low as 2° are reported to be sufficient to scour a plunge pool like the ones in the study area, but higher gradient breaks between 10 and 20° are quite common for consistent plunge pool development. A second gradient break further down slope changes flow conditions for the generation of cyclic steps, with asymmetric waveforms of 4 m high (average) in large wave fields in the entire the study area. Orientation is mainly orthogonal to the main slope direction but wave lengths and sinuosity vary, depending on the morphologic location of the wave field. The comparison with sediment wave fields with similar geometries or in similar environments shows that flow reconstruction based on the wave height and wave length alone along with a characterization of sediment grain size, however, yields non-unique results and is site specific.

AB - A systematic assessment of morphometric parameters of over 200 plunge pools along the steep escarpment base of western Great Bahama Bank and ~ 2000km2 of sediment wave fields of upslope migrating cyclic steps documents the importance of cascading density currents for sedimentation on the slope. The abrupt downslope termination of the Holocene mud wedge with the cyclic steps shows that strike parallel bottom currents interacting with the off-bank currents are responsible for slope sediment distribution. The plunge pools and sediment waves were generated by density-cascading and both are related to a hydraulic jump caused by two gradient changes along the slope profile. The bedforms highlight both the erosional and depositional nature of this current regime, which is controlled by slope gradient and the directional confinement by either grooves on the steep escarpment or gullies on the middle to lower slope. The > 20 m deep plunge pools are ellipsoidal, with an average width of 211 m and length of 283 m, but variations between 80–360 m and 100–650 m for width and length occur. They are caused by an average gradient break of 16° on the cemented upper slope. Gradient breaks of as low as 2° are reported to be sufficient to scour a plunge pool like the ones in the study area, but higher gradient breaks between 10 and 20° are quite common for consistent plunge pool development. A second gradient break further down slope changes flow conditions for the generation of cyclic steps, with asymmetric waveforms of 4 m high (average) in large wave fields in the entire the study area. Orientation is mainly orthogonal to the main slope direction but wave lengths and sinuosity vary, depending on the morphologic location of the wave field. The comparison with sediment wave fields with similar geometries or in similar environments shows that flow reconstruction based on the wave height and wave length alone along with a characterization of sediment grain size, however, yields non-unique results and is site specific.

KW - Carbonate slope

KW - Cyclic steps

KW - Density current

KW - Great Bahama Bank

KW - Multibeam bathymetry

KW - Plunge pool

KW - Sediment waves

KW - Slope morphology

KW - Supercritical flow conditions

KW - Waveform

UR - http://www.scopus.com/inward/record.url?scp=85036646283&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85036646283&partnerID=8YFLogxK

U2 - 10.1016/j.margeo.2017.11.020

DO - 10.1016/j.margeo.2017.11.020

M3 - Article

VL - 397

SP - 15

EP - 28

JO - Marine Geology

JF - Marine Geology

SN - 0025-3227

ER -