Submerged shoreline preservation and ravinement during rapid postglacial sea-level rise and subsequent "slowstand"

Lauren Pretorius, Andrew Green, Andrew Cooper

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

Submerged shorelines hold much potential for examining the interplay between the
rate of sea-level rise and geomorphic setting, and informing the development of models of
contemporary shoreline behavior. This paper describes the sedimentary architecture of a
submerged barrier shoreline complex off Durban, South Africa. The complex consists of
several barriers that have survived the postglacial transgression and associated erosive
ravinement processes. The main shoreline sequence (–60 m) dates to 11,690 ± 90 calibrated
(cal) yr B.P. and rests on a Pleistocene lagoonal deposit (35,395 ± 592 cal yr B.P.). The entire
barrier shoreline complex is truncated by a strongly diachronous wave ravinement surface.
The ravinement surface seaward of the main –60 m shoreline is steep, but the gradient
declines across and landward of the subordinate landward shoreline complexes. The steep
ravinement surface is attributed to fast sea-level rise (possibly associated with meltwater
pulse 1B), while the gentle ravinement surface is associated with a subsequent slowing of the
rate of sea-level rise (to 0.15 mm yr–1). Preservation of the main barrier and backbarrier
deposits through overstepping is associated namely with rapid transgression and increased
back-barrier accommodation. The smaller barriers landward of the main barrier were
preserved through overstepping related to gentle antecedent gradients, despite more intense ravinement during a very slow rise in sea level (slowstand). This process was assisted by a
sediment deficit. The resulting post-transgressive drape is also influenced by antecedent
topography created by the barriers themselves; damming along the landward sides of
overstepped barriers thickens the drape and creates a temporal disconnect between the
migration of the shoreface and more landward elements of the littoral system. In examining
the rates of shoreline migration associated with the overstepped barrier system, these are far
greater than those calculated for the predicted rates of shoreline change on similarly steep
coastal profiles. Future rates of shoreline migration appear to be insufficient to cause
overstepping, and rollover or erosional responses are more likely.
LanguageEnglish
Pages1059-1069
JournalGeological Society of America Bulletin
Volume128
Issue number7-8
Early online date1 Feb 2016
DOIs
Publication statusPublished - 1 Jul 2016

Fingerprint

Postglacial
shoreline
transgression
sea level rise
shoreline change
surface wave
sea level
Pleistocene

Keywords

  • Transgressive stratigraphy
  • sea-level rise
  • meltwater pulse

Cite this

@article{5f694238f3e04f409b3915e72d8de7d7,
title = "Submerged shoreline preservation and ravinement during rapid postglacial sea-level rise and subsequent {"}slowstand{"}",
abstract = "Submerged shorelines hold much potential for examining the interplay between therate of sea-level rise and geomorphic setting, and informing the development of models ofcontemporary shoreline behavior. This paper describes the sedimentary architecture of asubmerged barrier shoreline complex off Durban, South Africa. The complex consists ofseveral barriers that have survived the postglacial transgression and associated erosiveravinement processes. The main shoreline sequence (–60 m) dates to 11,690 ± 90 calibrated(cal) yr B.P. and rests on a Pleistocene lagoonal deposit (35,395 ± 592 cal yr B.P.). The entirebarrier shoreline complex is truncated by a strongly diachronous wave ravinement surface.The ravinement surface seaward of the main –60 m shoreline is steep, but the gradientdeclines across and landward of the subordinate landward shoreline complexes. The steepravinement surface is attributed to fast sea-level rise (possibly associated with meltwaterpulse 1B), while the gentle ravinement surface is associated with a subsequent slowing of therate of sea-level rise (to 0.15 mm yr–1). Preservation of the main barrier and backbarrierdeposits through overstepping is associated namely with rapid transgression and increasedback-barrier accommodation. The smaller barriers landward of the main barrier werepreserved through overstepping related to gentle antecedent gradients, despite more intense ravinement during a very slow rise in sea level (slowstand). This process was assisted by asediment deficit. The resulting post-transgressive drape is also influenced by antecedenttopography created by the barriers themselves; damming along the landward sides ofoverstepped barriers thickens the drape and creates a temporal disconnect between themigration of the shoreface and more landward elements of the littoral system. In examiningthe rates of shoreline migration associated with the overstepped barrier system, these are fargreater than those calculated for the predicted rates of shoreline change on similarly steepcoastal profiles. Future rates of shoreline migration appear to be insufficient to causeoverstepping, and rollover or erosional responses are more likely.",
keywords = "Transgressive stratigraphy, sea-level rise, meltwater pulse",
author = "Lauren Pretorius and Andrew Green and Andrew Cooper",
year = "2016",
month = "7",
day = "1",
doi = "10.1130/B31381.1",
language = "English",
volume = "128",
pages = "1059--1069",
journal = "Geological Society of America Bulletin",
issn = "0016-7606",
number = "7-8",

}

Submerged shoreline preservation and ravinement during rapid postglacial sea-level rise and subsequent "slowstand". / Pretorius, Lauren; Green, Andrew; Cooper, Andrew.

In: Geological Society of America Bulletin, Vol. 128, No. 7-8, 01.07.2016, p. 1059-1069.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Submerged shoreline preservation and ravinement during rapid postglacial sea-level rise and subsequent "slowstand"

AU - Pretorius, Lauren

AU - Green, Andrew

AU - Cooper, Andrew

PY - 2016/7/1

Y1 - 2016/7/1

N2 - Submerged shorelines hold much potential for examining the interplay between therate of sea-level rise and geomorphic setting, and informing the development of models ofcontemporary shoreline behavior. This paper describes the sedimentary architecture of asubmerged barrier shoreline complex off Durban, South Africa. The complex consists ofseveral barriers that have survived the postglacial transgression and associated erosiveravinement processes. The main shoreline sequence (–60 m) dates to 11,690 ± 90 calibrated(cal) yr B.P. and rests on a Pleistocene lagoonal deposit (35,395 ± 592 cal yr B.P.). The entirebarrier shoreline complex is truncated by a strongly diachronous wave ravinement surface.The ravinement surface seaward of the main –60 m shoreline is steep, but the gradientdeclines across and landward of the subordinate landward shoreline complexes. The steepravinement surface is attributed to fast sea-level rise (possibly associated with meltwaterpulse 1B), while the gentle ravinement surface is associated with a subsequent slowing of therate of sea-level rise (to 0.15 mm yr–1). Preservation of the main barrier and backbarrierdeposits through overstepping is associated namely with rapid transgression and increasedback-barrier accommodation. The smaller barriers landward of the main barrier werepreserved through overstepping related to gentle antecedent gradients, despite more intense ravinement during a very slow rise in sea level (slowstand). This process was assisted by asediment deficit. The resulting post-transgressive drape is also influenced by antecedenttopography created by the barriers themselves; damming along the landward sides ofoverstepped barriers thickens the drape and creates a temporal disconnect between themigration of the shoreface and more landward elements of the littoral system. In examiningthe rates of shoreline migration associated with the overstepped barrier system, these are fargreater than those calculated for the predicted rates of shoreline change on similarly steepcoastal profiles. Future rates of shoreline migration appear to be insufficient to causeoverstepping, and rollover or erosional responses are more likely.

AB - Submerged shorelines hold much potential for examining the interplay between therate of sea-level rise and geomorphic setting, and informing the development of models ofcontemporary shoreline behavior. This paper describes the sedimentary architecture of asubmerged barrier shoreline complex off Durban, South Africa. The complex consists ofseveral barriers that have survived the postglacial transgression and associated erosiveravinement processes. The main shoreline sequence (–60 m) dates to 11,690 ± 90 calibrated(cal) yr B.P. and rests on a Pleistocene lagoonal deposit (35,395 ± 592 cal yr B.P.). The entirebarrier shoreline complex is truncated by a strongly diachronous wave ravinement surface.The ravinement surface seaward of the main –60 m shoreline is steep, but the gradientdeclines across and landward of the subordinate landward shoreline complexes. The steepravinement surface is attributed to fast sea-level rise (possibly associated with meltwaterpulse 1B), while the gentle ravinement surface is associated with a subsequent slowing of therate of sea-level rise (to 0.15 mm yr–1). Preservation of the main barrier and backbarrierdeposits through overstepping is associated namely with rapid transgression and increasedback-barrier accommodation. The smaller barriers landward of the main barrier werepreserved through overstepping related to gentle antecedent gradients, despite more intense ravinement during a very slow rise in sea level (slowstand). This process was assisted by asediment deficit. The resulting post-transgressive drape is also influenced by antecedenttopography created by the barriers themselves; damming along the landward sides ofoverstepped barriers thickens the drape and creates a temporal disconnect between themigration of the shoreface and more landward elements of the littoral system. In examiningthe rates of shoreline migration associated with the overstepped barrier system, these are fargreater than those calculated for the predicted rates of shoreline change on similarly steepcoastal profiles. Future rates of shoreline migration appear to be insufficient to causeoverstepping, and rollover or erosional responses are more likely.

KW - Transgressive stratigraphy

KW - sea-level rise

KW - meltwater pulse

U2 - 10.1130/B31381.1

DO - 10.1130/B31381.1

M3 - Article

VL - 128

SP - 1059

EP - 1069

JO - Geological Society of America Bulletin

T2 - Geological Society of America Bulletin

JF - Geological Society of America Bulletin

SN - 0016-7606

IS - 7-8

ER -