Variations in downslope activity and bottom current dynamics in a land‐detached submarine channel system since the Last Glacial Maximum

Lotte Verweirder; Aggeliki Georgiopoulou; Kobus Langedock; Fred Fourie; Martin White; Sara Benetti; Fabio Sacchetti; Wieter Boone; David Van Rooij

doi:10.1111/sed.70077

Variations in downslope activity and bottom current dynamics in a land‐detached submarine channel system since the Last Glacial Maximum

Lotte Verweirder
, Aggeliki Georgiopoulou
, Kobus Langedock
, Fred Fourie
, Martin White
, Sara Benetti
, Fabio Sacchetti
, Wieter Boone
, David Van Rooij

Research output: Contribution to journal › Article › peer-review

Abstract

The Gollum Channel System is a land‐detached large‐scale canyon‐channel system situated offshore southwest Ireland on the Northeast Atlantic margin. The system has been considered inactive with downslope gravity flows since the last glacial period, but geophysical data in some of its branches do suggest Holocene activity. Here, the hypothesis of (in)activity under Holocene highstand conditions is tested. High‐resolution side‐scan sonar, photography and bathymetry data were collected using an autonomous underwater vehicle (AUV) in the upper slope (350 to 1000 m water depth) section of two channels in the system, Bilbo Channel and Frodo Channel. The AUV results are quantified and validated by current meter data from a mooring station in Bilbo Channel. Additionally, two sediment cores are used to build a record of channel floor processes since the Last Glacial Maximum and detect any temporal variability in channel activity. Turbidites in the sediment cores indicate that downslope sediment transport was happening well after deglaciation of the continental shelf, revealing that the channels were active under modern climatic and oceanographic conditions in the early Holocene. Crescentic bedforms in one of the channel head gullies suggest present‐day activity, but their limited spatial extent indicates present‐day downslope flows are minimal in frequency and volume. As a whole, the Gollum Channel System can be considered inactive today. Rather, tidally modulated bottom currents oriented along the channel axes are the main mechanism currently transporting and redistributing sediments, forming fields of megaripples and superimposed ripples. This dynamic channel floor environment has allowed the development of cold‐water coral mini‐mounds since the early Holocene. This study highlights that specific environmental conditions are necessary to allow frequent downslope activity in a land‐detached canyon‐channel system and these may vary even in systems draining the same shelf, and that inactivity may have important consequences for deep‐sea habitats, by allowing or promoting their development.

Original language	English
Pages (from-to)	1-25
Number of pages	25
Journal	Sedimentology
Early online date	3 Feb 2026
DOIs	https://doi.org/10.1111/sed.70077
Publication status	Published online - 3 Feb 2026

Bibliographical note

© 2026 The Author(s). Sedimentology published by John Wiley & Sons Ltd on behalf of International Association of Sedimentologists.

This manuscript contains Irish Public Sector Data (Geological Survey Ireland & Marine Institute) licensed under a Creative Commons Attribution 4.0 International (CC BY 4.0) licence. We would like to thank the captains and crews of the Irish and UK research vessels for assisting with the collection of the INFOMAR datasets, as well as the captains and crews of RV Celtic Explorer campaign CE21015 and RV Belgica campaigns 2022-18 and 2023-12. We are grateful to A. Ramisch, H. Braun and L. Schley at the Austrian Core Scanning Facility of the University of Innsbruck for their help with XRF core scanning. A. Matossian and P. Reyniers are thanked for constructive discussions that helped improve this manuscript. We are grateful to K. Verweirder for his help with compiling the AUV images into video clips. The authors wish to thank the four reviewers for their feedback that improved this manuscript.

Data Access Statement

INFOMAR data are available from the INFOMAR Marine Data Download Portal at https://www.infomar.ie/data (Geological Survey Ireland & Marine Institute, 2024). The RV Celtic Explorer and RV Belgica bathymetry data, sediment core data and AUV data of this study are available from the corresponding author upon reasonable request.

Funding

Author LV is funded by the Research Foundation-Flanders (FWO grant 1114521N) and the Special Research Fund (BOF) of Ghent University. XRF analyses were partly funded by a Postgraduate Research Grant from the International Association of Sedimentologists.

Keywords

Autonomous underwater vehicle
Porcupine Seabight
cold‐water corals
Gollum Channel System
bottom currents
turbidity currents

Access to Document

10.1111/sed.70077

sed.70077.pdfFinal published version, 63.2 MBLicence: CC BY

Cite this

@article{411f9a7e995b44479dc2bf2b85eda03a,

title = "Variations in downslope activity and bottom current dynamics in a land‐detached submarine channel system since the Last Glacial Maximum",

abstract = "The Gollum Channel System is a land‐detached large‐scale canyon‐channel system situated offshore southwest Ireland on the Northeast Atlantic margin. The system has been considered inactive with downslope gravity flows since the last glacial period, but geophysical data in some of its branches do suggest Holocene activity. Here, the hypothesis of (in)activity under Holocene highstand conditions is tested. High‐resolution side‐scan sonar, photography and bathymetry data were collected using an autonomous underwater vehicle (AUV) in the upper slope (350 to 1000 m water depth) section of two channels in the system, Bilbo Channel and Frodo Channel. The AUV results are quantified and validated by current meter data from a mooring station in Bilbo Channel. Additionally, two sediment cores are used to build a record of channel floor processes since the Last Glacial Maximum and detect any temporal variability in channel activity. Turbidites in the sediment cores indicate that downslope sediment transport was happening well after deglaciation of the continental shelf, revealing that the channels were active under modern climatic and oceanographic conditions in the early Holocene. Crescentic bedforms in one of the channel head gullies suggest present‐day activity, but their limited spatial extent indicates present‐day downslope flows are minimal in frequency and volume. As a whole, the Gollum Channel System can be considered inactive today. Rather, tidally modulated bottom currents oriented along the channel axes are the main mechanism currently transporting and redistributing sediments, forming fields of megaripples and superimposed ripples. This dynamic channel floor environment has allowed the development of cold‐water coral mini‐mounds since the early Holocene. This study highlights that specific environmental conditions are necessary to allow frequent downslope activity in a land‐detached canyon‐channel system and these may vary even in systems draining the same shelf, and that inactivity may have important consequences for deep‐sea habitats, by allowing or promoting their development.",

keywords = "Autonomous underwater vehicle, Porcupine Seabight, cold‐water corals, Gollum Channel System, bottom currents, turbidity currents",

author = "Lotte Verweirder and Aggeliki Georgiopoulou and Kobus Langedock and Fred Fourie and Martin White and Sara Benetti and Fabio Sacchetti and Wieter Boone and \{Van Rooij\}, David",

note = "{\textcopyright} 2026 The Author(s). Sedimentology published by John Wiley \& Sons Ltd on behalf of International Association of Sedimentologists. This manuscript contains Irish Public Sector Data (Geological Survey Ireland \& Marine Institute) licensed under a Creative Commons Attribution 4.0 International (CC BY 4.0) licence. We would like to thank the captains and crews of the Irish and UK research vessels for assisting with the collection of the INFOMAR datasets, as well as the captains and crews of RV Celtic Explorer campaign CE21015 and RV Belgica campaigns 2022-18 and 2023-12. We are grateful to A. Ramisch, H. Braun and L. Schley at the Austrian Core Scanning Facility of the University of Innsbruck for their help with XRF core scanning. A. Matossian and P. Reyniers are thanked for constructive discussions that helped improve this manuscript. We are grateful to K. Verweirder for his help with compiling the AUV images into video clips. The authors wish to thank the four reviewers for their feedback that improved this manuscript.",

year = "2026",

month = feb,

day = "3",

doi = "10.1111/sed.70077",

language = "English",

pages = "1--25",

journal = "Sedimentology",

issn = "0037-0746",

publisher = "John Wiley and Sons Inc.",

}

TY - JOUR

T1 - Variations in downslope activity and bottom current dynamics in a land‐detached submarine channel system since the Last Glacial Maximum

AU - Verweirder, Lotte

AU - Georgiopoulou, Aggeliki

AU - Langedock, Kobus

AU - Fourie, Fred

AU - White, Martin

AU - Benetti, Sara

AU - Sacchetti, Fabio

AU - Boone, Wieter

AU - Van Rooij, David

N1 - © 2026 The Author(s). Sedimentology published by John Wiley & Sons Ltd on behalf of International Association of Sedimentologists. This manuscript contains Irish Public Sector Data (Geological Survey Ireland & Marine Institute) licensed under a Creative Commons Attribution 4.0 International (CC BY 4.0) licence. We would like to thank the captains and crews of the Irish and UK research vessels for assisting with the collection of the INFOMAR datasets, as well as the captains and crews of RV Celtic Explorer campaign CE21015 and RV Belgica campaigns 2022-18 and 2023-12. We are grateful to A. Ramisch, H. Braun and L. Schley at the Austrian Core Scanning Facility of the University of Innsbruck for their help with XRF core scanning. A. Matossian and P. Reyniers are thanked for constructive discussions that helped improve this manuscript. We are grateful to K. Verweirder for his help with compiling the AUV images into video clips. The authors wish to thank the four reviewers for their feedback that improved this manuscript.

PY - 2026/2/3

Y1 - 2026/2/3

N2 - The Gollum Channel System is a land‐detached large‐scale canyon‐channel system situated offshore southwest Ireland on the Northeast Atlantic margin. The system has been considered inactive with downslope gravity flows since the last glacial period, but geophysical data in some of its branches do suggest Holocene activity. Here, the hypothesis of (in)activity under Holocene highstand conditions is tested. High‐resolution side‐scan sonar, photography and bathymetry data were collected using an autonomous underwater vehicle (AUV) in the upper slope (350 to 1000 m water depth) section of two channels in the system, Bilbo Channel and Frodo Channel. The AUV results are quantified and validated by current meter data from a mooring station in Bilbo Channel. Additionally, two sediment cores are used to build a record of channel floor processes since the Last Glacial Maximum and detect any temporal variability in channel activity. Turbidites in the sediment cores indicate that downslope sediment transport was happening well after deglaciation of the continental shelf, revealing that the channels were active under modern climatic and oceanographic conditions in the early Holocene. Crescentic bedforms in one of the channel head gullies suggest present‐day activity, but their limited spatial extent indicates present‐day downslope flows are minimal in frequency and volume. As a whole, the Gollum Channel System can be considered inactive today. Rather, tidally modulated bottom currents oriented along the channel axes are the main mechanism currently transporting and redistributing sediments, forming fields of megaripples and superimposed ripples. This dynamic channel floor environment has allowed the development of cold‐water coral mini‐mounds since the early Holocene. This study highlights that specific environmental conditions are necessary to allow frequent downslope activity in a land‐detached canyon‐channel system and these may vary even in systems draining the same shelf, and that inactivity may have important consequences for deep‐sea habitats, by allowing or promoting their development.

AB - The Gollum Channel System is a land‐detached large‐scale canyon‐channel system situated offshore southwest Ireland on the Northeast Atlantic margin. The system has been considered inactive with downslope gravity flows since the last glacial period, but geophysical data in some of its branches do suggest Holocene activity. Here, the hypothesis of (in)activity under Holocene highstand conditions is tested. High‐resolution side‐scan sonar, photography and bathymetry data were collected using an autonomous underwater vehicle (AUV) in the upper slope (350 to 1000 m water depth) section of two channels in the system, Bilbo Channel and Frodo Channel. The AUV results are quantified and validated by current meter data from a mooring station in Bilbo Channel. Additionally, two sediment cores are used to build a record of channel floor processes since the Last Glacial Maximum and detect any temporal variability in channel activity. Turbidites in the sediment cores indicate that downslope sediment transport was happening well after deglaciation of the continental shelf, revealing that the channels were active under modern climatic and oceanographic conditions in the early Holocene. Crescentic bedforms in one of the channel head gullies suggest present‐day activity, but their limited spatial extent indicates present‐day downslope flows are minimal in frequency and volume. As a whole, the Gollum Channel System can be considered inactive today. Rather, tidally modulated bottom currents oriented along the channel axes are the main mechanism currently transporting and redistributing sediments, forming fields of megaripples and superimposed ripples. This dynamic channel floor environment has allowed the development of cold‐water coral mini‐mounds since the early Holocene. This study highlights that specific environmental conditions are necessary to allow frequent downslope activity in a land‐detached canyon‐channel system and these may vary even in systems draining the same shelf, and that inactivity may have important consequences for deep‐sea habitats, by allowing or promoting their development.

KW - Autonomous underwater vehicle

KW - Porcupine Seabight

KW - cold‐water corals

KW - Gollum Channel System

KW - bottom currents

KW - turbidity currents

U2 - 10.1111/sed.70077

DO - 10.1111/sed.70077

M3 - Article

SN - 0037-0746

SP - 1

EP - 25

JO - Sedimentology

JF - Sedimentology

ER -

Variations in downslope activity and bottom current dynamics in a land‐detached submarine channel system since the Last Glacial Maximum

Abstract

Bibliographical note

Data Access Statement

Funding

Keywords

Access to Document

Fingerprint

Cite this