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The Influence of Syndepositional Macropores on the Hydraulic Integrity of Thick Alluvial Clay Aquitards

Timms, W.A.; Acworth, R.I.; Crane, Richard A.; Arns, Christoph; Arns, Ji-Youn; McGeeney, Dayne E.; Rau, G.C.; Cuthbert, Mark O.

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Clay‐rich deposits are commonly assumed to be aquitards which act as natural hydraulic barriers due to their low hydraulic connectivity. Postdepositional weathering processes are known to increase the permeability of aquitards in the near surface but not impact on deeper parts of relatively thick formations. However, syndepositional processes affecting the hydraulic properties of aquitards have previously received little attention in the literature. Here, we analyze a 31 m deep sediment core...[Show more]

dc.contributor.authorTimms, W.A.
dc.contributor.authorAcworth, R.I.
dc.contributor.authorCrane, Richard A.
dc.contributor.authorArns, Christoph
dc.contributor.authorArns, Ji-Youn
dc.contributor.authorMcGeeney, Dayne E.
dc.contributor.authorRau, G.C.
dc.contributor.authorCuthbert, Mark O.
dc.date.accessioned2020-10-14T01:01:14Z
dc.date.available2020-10-14T01:01:14Z
dc.identifier.issn0043-1397
dc.identifier.urihttp://hdl.handle.net/1885/212485
dc.description.abstractClay‐rich deposits are commonly assumed to be aquitards which act as natural hydraulic barriers due to their low hydraulic connectivity. Postdepositional weathering processes are known to increase the permeability of aquitards in the near surface but not impact on deeper parts of relatively thick formations. However, syndepositional processes affecting the hydraulic properties of aquitards have previously received little attention in the literature. Here, we analyze a 31 m deep sediment core recovered from an inland clay‐rich sedimentary sequence using a combination of techniques including particle size distribution and microscopy, centrifuge dye tracer testing and micro X‐ray CT imaging. Subaerial deposition of soils within these fine grained alluvial deposits has led to the preservation of considerable macropores (root channels or animal burrows). Connected pores and macropores thus account for vertical hydraulic conductivity (K) of urn:x-wiley:00431397:media:wrcr23221:wrcr23221-math-0001 m/s (geometric mean of 13 samples) throughout the thick aquitard, compared to a matrix K that is likely < urn:x-wiley:00431397:media:wrcr23221:wrcr23221-math-0002 m/s, the minimum K value that was measured. Our testing demonstrates that such syndepositional features may compromise the hydraulic integrity of what otherwise appears to have the characteristics of a much lower permeability aquitard. Heterogeneity within a clay‐rich matrix could also enhance vertical connectivity, as indicated by digital analysis of pore morphology in CT images. We highlight that the paleo‐environment under which the sediment was deposited must be considered when aquitards are investigated as potential natural hydraulic barriers and illustrate the value of combining multiple investigation techniques for characterizing clay‐rich deposits.
dc.description.sponsorshipThe work was financially supported by the National Centre for Groundwater Research and Training, supported by the Australian Research Council and the National Water Commission. Mark Cuthbert was financially supported by the European Community Seventh Framework Programme (FP7/2007–2013) under grant agreement 299091. C.H.A. acknowledges funding by the Australian Research Council through an ARC Future Fellowship (FT120100216).
dc.format.mimetypeapplication/pdf
dc.language.isoen_AU
dc.publisherAmerican Geophysical Union
dc.rights© 2018. The Authors
dc.rights.urihttps://creativecommons.org/licenses/by-nc-nd/4.0/
dc.sourceWater Resources Research
dc.titleThe Influence of Syndepositional Macropores on the Hydraulic Integrity of Thick Alluvial Clay Aquitards
dc.typeJournal article
local.description.notesImported from ARIES
local.identifier.citationvolume54
dc.date.issued2018
local.identifier.absfor040603 - Hydrogeology
local.identifier.absfor050305 - Soil Physics
local.identifier.absfor040499 - Geophysics not elsewhere classified
local.identifier.ariespublicationa383154xPUB9999
local.publisher.urlhttp://www.agu.org/journals/wr/
local.type.statusPublished Version
local.contributor.affiliationTimms, W.A., The University of New South Wales
local.contributor.affiliationAcworth, R.I., The University of New South Wales
local.contributor.affiliationCrane, Richard A. , School of Mining Engineering
local.contributor.affiliationArns, Christoph, University of New South Wales
local.contributor.affiliationArns, Ji-Youn, College of Science, ANU
local.contributor.affiliationMcGeeney, Dayne E. , Connected Waters Initiative Research Centre
local.contributor.affiliationRau, G.C., The University of New South Wales
local.contributor.affiliationCuthbert, Mark O., School of Earth and Ocean Sciences
dc.relationhttp://purl.org/au-research/grants/arc/FT120100216
local.bibliographicCitation.issue4
local.bibliographicCitation.startpage3122
local.bibliographicCitation.lastpage3138
local.identifier.doi10.1029/2017WR021681
local.identifier.absseo970104 - Expanding Knowledge in the Earth Sciences
local.identifier.absseo850203 - Oil and Gas Extraction
dc.date.updated2020-07-06T08:18:32Z
local.identifier.scopusID2-s2.0-85046008612
dcterms.accessRightsOpen Access
dc.provenance© 2018. The Authors. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
dc.rights.licenseCreative Commons Attribution-NonCommercial-NoDerivs License
CollectionsANU Research Publications

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