3D characterisation and quantification of an offshore freshened groundwater system in the Canterbury Bight.

Micallef, Aaron , Person, Mark, Haroon, Amir , Weymer, Bradley A. , Jegen, Marion , Schwalenberg, Katrin, Faghih, Zahra, Duan, Shuangmin, Cohen, Denis, Mountjoy, Joshu J., Woelz, Susanne, Gable, Carl W., Averes, Tanita and Kumar Tiwari, Ashwani (2020) 3D characterisation and quantification of an offshore freshened groundwater system in the Canterbury Bight. Open Access Nature Communications, 11 (Article number 1372). DOI 10.1038/s41467-020-14770-7.

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Supplementary data:

Abstract

Although offshore freshened groundwater (OFG) systems have been documented in numerous continental margins worldwide, their geometry, controls and emplacement dynamics remain poorly constrained. Here we integrate controlled-source electromagnetic, seismic reflection and borehole data with hydrological modelling to quantitatively characterise a previously unknown OFG system near Canterbury, New Zealand. The OFG system consists of one main, and two smaller, low salinity groundwater bodies. The main body extends up to 60 km from the coast and a seawater depth of 110 m. We attribute along-shelf variability in salinity to permeability heterogeneity due to permeable conduits and normal faults, and to recharge from rivers during sea level lowstands. A meteoric origin of the OFG and active groundwater migration from onshore are inferred. However, modelling results suggest that the majority of the OFG was emplaced via topographically-driven flow during sea level lowstands in the last 300 ka. Global volumetric estimates of OFG will be significantly revised if active margins, with steep coastal topographies like the Canterbury margin, are considered.

Document Type: Article
Funder compliance: info:eu-repo/grantAgreement/EC/H2020/677898
Additional Information: Access to the RIFT2D code is available from Prof. Mark Person (mark.person@nmt.edu) upon reasonable request.
Keywords: ATLANTIC CONTINENTAL-SHELF; ELECTROMAGNETIC DATA; MARINE-SEDIMENTS; PASSIVE MARGIN; SOUTH ISLAND; FLOW; BASIN; WATER; ARCHITECTURE; PATTERNS
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Kiel University
Refereed: Yes
Open Access Journal?: Yes
Publisher: Nature Research
Projects: MARCAN
Date Deposited: 16 Mar 2020 12:00
Last Modified: 08 Feb 2023 09:45
URI: https://oceanrep.geomar.de/id/eprint/49261

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