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Seismically-induced down-sagging structures in tephra layers (tephra-seismites) preserved in lakes since 17.5 cal ka, Hamilton lowlands, New Zealand

Max O. Kluger, David J. Lowe, Vicki G. Moon, Jordanka Chaneva, Richard Johnston Orcid Logo, Pilar Villamor, Tehnuka Ilanko, Richard A. Melchert, Rolando P. Orense, Remedy C. Loame, Nic Ross

Sedimentary Geology, Volume: 445, Start page: 106327

Swansea University Author: Richard Johnston Orcid Logo

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Abstract

We analysed numerous soft-sediment deformation structures (SSDS) identified in seven unconsolidated, up to 8-cm thick, siliceous tephra layers that had been deposited in ~35 riverine-phytogenic lakes within the Hamilton lowlands, northern North Island, New Zealand, since 17.5 calendar (cal) ka BP. B...

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Published in: Sedimentary Geology
ISSN: 0037-0738
Published: Elsevier BV 2023
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URI: https://cronfa.swan.ac.uk/Record/cronfa62278
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Based on sediment/tephra descriptions and X-ray computed tomography scanning of cores taken from ten lakes, we classified these SSDS into elongated load structures (i.e., down-sagging structures) of different dimensions, ranging from millimetre- to decimetre-scale, and centimetre-long dykes. Down-sagging structures were commonly manifested as intrusions of internal tephra beds of very fine to medium sand into underlying organic lake sediments. The tephra layers commonly exhibited an upper silt bed, which was not directly affected by deformation. Dry bulk density and grain size distribution analyses of both the organic lake sediment and the internal tephra beds provided evidence for the deformation mechanism of down-sagging structures and their driving force: the organic lake sediment and the upper silt bed are less liquefiable, whereas the very fine to medium sand internal tephra beds are liquefiable. The tephra layers and encapsulating organic lake sediments formed three-layer (a-b-a) density systems, where &#x2018;a&#x2019; denotes the sediment unit of lower density. We infer that downward-directed deformation was favoured by the a-b-a density system with the upper, less-liquefiable, silt bed within the tephra layer preventing upward intrusion during the liquefaction process. The spatial distribution and ages of SSDS within the lakes provided some evidence that liquefaction of the older tephra layers, i.e., Rerewhakaaitu, Rotorua, and Waiohau tephras, deposited 17.5, 15.6, and 14&#x202F;cal&#x202F;ka BP, respectively, was triggered by a seismic source to the northeast of the Hamilton lowlands (i.e., Kerepehi and/or Te Puninga faults). 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spelling 2023-01-30T15:55:24.8771165 v2 62278 2023-01-09 Seismically-induced down-sagging structures in tephra layers (tephra-seismites) preserved in lakes since 17.5 cal ka, Hamilton lowlands, New Zealand 23282e7acce87dd926b8a62ae410a393 0000-0003-1977-6418 Richard Johnston Richard Johnston true false 2023-01-09 MTLS We analysed numerous soft-sediment deformation structures (SSDS) identified in seven unconsolidated, up to 8-cm thick, siliceous tephra layers that had been deposited in ~35 riverine-phytogenic lakes within the Hamilton lowlands, northern North Island, New Zealand, since 17.5 calendar (cal) ka BP. Based on sediment/tephra descriptions and X-ray computed tomography scanning of cores taken from ten lakes, we classified these SSDS into elongated load structures (i.e., down-sagging structures) of different dimensions, ranging from millimetre- to decimetre-scale, and centimetre-long dykes. Down-sagging structures were commonly manifested as intrusions of internal tephra beds of very fine to medium sand into underlying organic lake sediments. The tephra layers commonly exhibited an upper silt bed, which was not directly affected by deformation. Dry bulk density and grain size distribution analyses of both the organic lake sediment and the internal tephra beds provided evidence for the deformation mechanism of down-sagging structures and their driving force: the organic lake sediment and the upper silt bed are less liquefiable, whereas the very fine to medium sand internal tephra beds are liquefiable. The tephra layers and encapsulating organic lake sediments formed three-layer (a-b-a) density systems, where ‘a’ denotes the sediment unit of lower density. We infer that downward-directed deformation was favoured by the a-b-a density system with the upper, less-liquefiable, silt bed within the tephra layer preventing upward intrusion during the liquefaction process. The spatial distribution and ages of SSDS within the lakes provided some evidence that liquefaction of the older tephra layers, i.e., Rerewhakaaitu, Rotorua, and Waiohau tephras, deposited 17.5, 15.6, and 14 cal ka BP, respectively, was triggered by a seismic source to the northeast of the Hamilton lowlands (i.e., Kerepehi and/or Te Puninga faults). In contrast, the liquefaction of the younger tephra layers, i.e., Opepe, Mamaku, and Tuhua tephras, deposited 10.0, 8.0, and 7.6 cal ka BP, respectively, may have been triggered by movement on local faults within the Hamilton lowlands, namely the Hamilton Basin faults, or by distant faulting at the Hikurangi subduction margin east of North Island. Journal Article Sedimentary Geology 445 106327 Elsevier BV 0037-0738 Soft-sediment deformation structures (SSDS), Tephra, Liquefaction, Paleoearthquakes, Kerepehi Fault, Te Puninga Fault 1 3 2023 2023-03-01 10.1016/j.sedgeo.2022.106327 COLLEGE NANME Materials Science and Engineering COLLEGE CODE MTLS Swansea University RJ was supported by an AIM Facility fund in part from the UK's Engineering and Physical Sciences Research Council (EP/M028267/1). 2023-01-30T15:55:24.8771165 2023-01-09T10:16:59.7684692 Faculty of Science and Engineering School of Engineering and Applied Sciences - Materials Science and Engineering Max O. Kluger 1 David J. Lowe 2 Vicki G. Moon 3 Jordanka Chaneva 4 Richard Johnston 0000-0003-1977-6418 5 Pilar Villamor 6 Tehnuka Ilanko 7 Richard A. Melchert 8 Rolando P. Orense 9 Remedy C. Loame 10 Nic Ross 11 Under embargo Under embargo 2023-01-09T10:37:46.2847812 Output 12007997 application/pdf Accepted Manuscript true 2024-01-05T00:00:00.0000000 ©2023 All rights reserved. All article content, except where otherwise noted, is licensed under a Creative Commons Attribution Non-Commercial No Derivatives License (CC-BY-NC-ND) true eng https://creativecommons.org/licenses/by-nc-nd/4.0/
title Seismically-induced down-sagging structures in tephra layers (tephra-seismites) preserved in lakes since 17.5 cal ka, Hamilton lowlands, New Zealand
spellingShingle Seismically-induced down-sagging structures in tephra layers (tephra-seismites) preserved in lakes since 17.5 cal ka, Hamilton lowlands, New Zealand
Richard Johnston
title_short Seismically-induced down-sagging structures in tephra layers (tephra-seismites) preserved in lakes since 17.5 cal ka, Hamilton lowlands, New Zealand
title_full Seismically-induced down-sagging structures in tephra layers (tephra-seismites) preserved in lakes since 17.5 cal ka, Hamilton lowlands, New Zealand
title_fullStr Seismically-induced down-sagging structures in tephra layers (tephra-seismites) preserved in lakes since 17.5 cal ka, Hamilton lowlands, New Zealand
title_full_unstemmed Seismically-induced down-sagging structures in tephra layers (tephra-seismites) preserved in lakes since 17.5 cal ka, Hamilton lowlands, New Zealand
title_sort Seismically-induced down-sagging structures in tephra layers (tephra-seismites) preserved in lakes since 17.5 cal ka, Hamilton lowlands, New Zealand
author_id_str_mv 23282e7acce87dd926b8a62ae410a393
author_id_fullname_str_mv 23282e7acce87dd926b8a62ae410a393_***_Richard Johnston
author Richard Johnston
author2 Max O. Kluger
David J. Lowe
Vicki G. Moon
Jordanka Chaneva
Richard Johnston
Pilar Villamor
Tehnuka Ilanko
Richard A. Melchert
Rolando P. Orense
Remedy C. Loame
Nic Ross
format Journal article
container_title Sedimentary Geology
container_volume 445
container_start_page 106327
publishDate 2023
institution Swansea University
issn 0037-0738
doi_str_mv 10.1016/j.sedgeo.2022.106327
publisher Elsevier BV
college_str Faculty of Science and Engineering
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hierarchy_top_id facultyofscienceandengineering
hierarchy_top_title Faculty of Science and Engineering
hierarchy_parent_id facultyofscienceandengineering
hierarchy_parent_title Faculty of Science and Engineering
department_str School of Engineering and Applied Sciences - Materials Science and Engineering{{{_:::_}}}Faculty of Science and Engineering{{{_:::_}}}School of Engineering and Applied Sciences - Materials Science and Engineering
document_store_str 0
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description We analysed numerous soft-sediment deformation structures (SSDS) identified in seven unconsolidated, up to 8-cm thick, siliceous tephra layers that had been deposited in ~35 riverine-phytogenic lakes within the Hamilton lowlands, northern North Island, New Zealand, since 17.5 calendar (cal) ka BP. Based on sediment/tephra descriptions and X-ray computed tomography scanning of cores taken from ten lakes, we classified these SSDS into elongated load structures (i.e., down-sagging structures) of different dimensions, ranging from millimetre- to decimetre-scale, and centimetre-long dykes. Down-sagging structures were commonly manifested as intrusions of internal tephra beds of very fine to medium sand into underlying organic lake sediments. The tephra layers commonly exhibited an upper silt bed, which was not directly affected by deformation. Dry bulk density and grain size distribution analyses of both the organic lake sediment and the internal tephra beds provided evidence for the deformation mechanism of down-sagging structures and their driving force: the organic lake sediment and the upper silt bed are less liquefiable, whereas the very fine to medium sand internal tephra beds are liquefiable. The tephra layers and encapsulating organic lake sediments formed three-layer (a-b-a) density systems, where ‘a’ denotes the sediment unit of lower density. We infer that downward-directed deformation was favoured by the a-b-a density system with the upper, less-liquefiable, silt bed within the tephra layer preventing upward intrusion during the liquefaction process. The spatial distribution and ages of SSDS within the lakes provided some evidence that liquefaction of the older tephra layers, i.e., Rerewhakaaitu, Rotorua, and Waiohau tephras, deposited 17.5, 15.6, and 14 cal ka BP, respectively, was triggered by a seismic source to the northeast of the Hamilton lowlands (i.e., Kerepehi and/or Te Puninga faults). In contrast, the liquefaction of the younger tephra layers, i.e., Opepe, Mamaku, and Tuhua tephras, deposited 10.0, 8.0, and 7.6 cal ka BP, respectively, may have been triggered by movement on local faults within the Hamilton lowlands, namely the Hamilton Basin faults, or by distant faulting at the Hikurangi subduction margin east of North Island.
published_date 2023-03-01T04:21:46Z
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