Geomorphic and hydrological controls on groundwater dolocrete formation in the semi-arid Hamersley Basin, northwest Australia

Caroline C. Mather, David J. Nash, Shawan Dogramaci, Pauline F. Grierson, Grzegorz Skrzypek

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Abstract

Groundwater dolocretes may exert an important geomorphic control on landscape evolution within sub-humid to arid regions. However, the geomorphic and hydrogeological settings of dolocrete remain poorly described. The hydrochemical conditions of dolomite precipitation in groundwater environments are also not well known. Classic models of dolocrete formation explain dolomite precipitation from highly evolved groundwaters at the terminus of major drainage but do not explain dolocrete distributed in regionally elevated landscapes, upgradient of major drainage. This study investigated the mineralogy, micromorphology and stable carbon and oxygen isotope compositions of three dolocrete profiles within a regionally elevated sub-basin of the Hamersley Ranges in the Pilbara region of northwest Australia. We sought to establish the environmental and hydrochemical conditions and present a model for dolocrete formation. We found that dolocrete formed within zones of emerging groundwater under saline-evaporitic conditions within internally draining sub-basins, most likely during the Late Miocene and Pliocene. Saline-evaporitic conditions were indicated by: (i) the mineralogy, dominated by dolomite, palygorskite and smectite; (ii) desiccation features and the presence of phreatic and vadose cements, indicative of a shallow fluctuating water table, and; (iii) dolomite delta O-18 values (median = -5.88 parts per thousand). Dolomite precipitation was promoted by evaporation and carbon dioxide degassing from shallow magnesium (Mg)-rich groundwater. These factors appear to have been the major drivers of dolocrete development without a requirement for significant down-dip hydrochemical modification. Primary dolomite precipitation was possible due to the presence of microbial extracellular polymeric substances (EPS). EPS provided negatively charged nucleation sites, which bound Mg2+, overcoming kinetic effects. High microbial activity within groundwater systems suggest these processes may be important for dolocrete formation worldwide and that groundwater dolocretes may be more pervasive in landscapes than currently recognized. (c) 2019 John Wiley & Sons, Ltd.

Original languageEnglish
Number of pages19
JournalEarth Surface Processes and Landforms
DOIs
Publication statusPublished - 14 Aug 2019

Cite this

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title = "Geomorphic and hydrological controls on groundwater dolocrete formation in the semi-arid Hamersley Basin, northwest Australia",
abstract = "Groundwater dolocretes may exert an important geomorphic control on landscape evolution within sub-humid to arid regions. However, the geomorphic and hydrogeological settings of dolocrete remain poorly described. The hydrochemical conditions of dolomite precipitation in groundwater environments are also not well known. Classic models of dolocrete formation explain dolomite precipitation from highly evolved groundwaters at the terminus of major drainage but do not explain dolocrete distributed in regionally elevated landscapes, upgradient of major drainage. This study investigated the mineralogy, micromorphology and stable carbon and oxygen isotope compositions of three dolocrete profiles within a regionally elevated sub-basin of the Hamersley Ranges in the Pilbara region of northwest Australia. We sought to establish the environmental and hydrochemical conditions and present a model for dolocrete formation. We found that dolocrete formed within zones of emerging groundwater under saline-evaporitic conditions within internally draining sub-basins, most likely during the Late Miocene and Pliocene. Saline-evaporitic conditions were indicated by: (i) the mineralogy, dominated by dolomite, palygorskite and smectite; (ii) desiccation features and the presence of phreatic and vadose cements, indicative of a shallow fluctuating water table, and; (iii) dolomite delta O-18 values (median = -5.88 parts per thousand). Dolomite precipitation was promoted by evaporation and carbon dioxide degassing from shallow magnesium (Mg)-rich groundwater. These factors appear to have been the major drivers of dolocrete development without a requirement for significant down-dip hydrochemical modification. Primary dolomite precipitation was possible due to the presence of microbial extracellular polymeric substances (EPS). EPS provided negatively charged nucleation sites, which bound Mg2+, overcoming kinetic effects. High microbial activity within groundwater systems suggest these processes may be important for dolocrete formation worldwide and that groundwater dolocretes may be more pervasive in landscapes than currently recognized. (c) 2019 John Wiley & Sons, Ltd.",
keywords = "dolomite, stable isotopes, chemical sediments, microbial EPS, landform evolution, CHANNEL IRON DEPOSITS, DOLOMITE FORMATION, STABLE-ISOTOPE, MICROBIAL MEDIATION, CARBONATE DEPOSITS, PROVENCE BASIN, LAGOA-VERMELHA, EBRO BASIN, PRECIPITATION, CALCRETE",
author = "Mather, {Caroline C.} and Nash, {David J.} and Shawan Dogramaci and Grierson, {Pauline F.} and Grzegorz Skrzypek",
year = "2019",
month = "8",
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doi = "10.1002/esp.4704",
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TY - JOUR

T1 - Geomorphic and hydrological controls on groundwater dolocrete formation in the semi-arid Hamersley Basin, northwest Australia

AU - Mather, Caroline C.

AU - Nash, David J.

AU - Dogramaci, Shawan

AU - Grierson, Pauline F.

AU - Skrzypek, Grzegorz

PY - 2019/8/14

Y1 - 2019/8/14

N2 - Groundwater dolocretes may exert an important geomorphic control on landscape evolution within sub-humid to arid regions. However, the geomorphic and hydrogeological settings of dolocrete remain poorly described. The hydrochemical conditions of dolomite precipitation in groundwater environments are also not well known. Classic models of dolocrete formation explain dolomite precipitation from highly evolved groundwaters at the terminus of major drainage but do not explain dolocrete distributed in regionally elevated landscapes, upgradient of major drainage. This study investigated the mineralogy, micromorphology and stable carbon and oxygen isotope compositions of three dolocrete profiles within a regionally elevated sub-basin of the Hamersley Ranges in the Pilbara region of northwest Australia. We sought to establish the environmental and hydrochemical conditions and present a model for dolocrete formation. We found that dolocrete formed within zones of emerging groundwater under saline-evaporitic conditions within internally draining sub-basins, most likely during the Late Miocene and Pliocene. Saline-evaporitic conditions were indicated by: (i) the mineralogy, dominated by dolomite, palygorskite and smectite; (ii) desiccation features and the presence of phreatic and vadose cements, indicative of a shallow fluctuating water table, and; (iii) dolomite delta O-18 values (median = -5.88 parts per thousand). Dolomite precipitation was promoted by evaporation and carbon dioxide degassing from shallow magnesium (Mg)-rich groundwater. These factors appear to have been the major drivers of dolocrete development without a requirement for significant down-dip hydrochemical modification. Primary dolomite precipitation was possible due to the presence of microbial extracellular polymeric substances (EPS). EPS provided negatively charged nucleation sites, which bound Mg2+, overcoming kinetic effects. High microbial activity within groundwater systems suggest these processes may be important for dolocrete formation worldwide and that groundwater dolocretes may be more pervasive in landscapes than currently recognized. (c) 2019 John Wiley & Sons, Ltd.

AB - Groundwater dolocretes may exert an important geomorphic control on landscape evolution within sub-humid to arid regions. However, the geomorphic and hydrogeological settings of dolocrete remain poorly described. The hydrochemical conditions of dolomite precipitation in groundwater environments are also not well known. Classic models of dolocrete formation explain dolomite precipitation from highly evolved groundwaters at the terminus of major drainage but do not explain dolocrete distributed in regionally elevated landscapes, upgradient of major drainage. This study investigated the mineralogy, micromorphology and stable carbon and oxygen isotope compositions of three dolocrete profiles within a regionally elevated sub-basin of the Hamersley Ranges in the Pilbara region of northwest Australia. We sought to establish the environmental and hydrochemical conditions and present a model for dolocrete formation. We found that dolocrete formed within zones of emerging groundwater under saline-evaporitic conditions within internally draining sub-basins, most likely during the Late Miocene and Pliocene. Saline-evaporitic conditions were indicated by: (i) the mineralogy, dominated by dolomite, palygorskite and smectite; (ii) desiccation features and the presence of phreatic and vadose cements, indicative of a shallow fluctuating water table, and; (iii) dolomite delta O-18 values (median = -5.88 parts per thousand). Dolomite precipitation was promoted by evaporation and carbon dioxide degassing from shallow magnesium (Mg)-rich groundwater. These factors appear to have been the major drivers of dolocrete development without a requirement for significant down-dip hydrochemical modification. Primary dolomite precipitation was possible due to the presence of microbial extracellular polymeric substances (EPS). EPS provided negatively charged nucleation sites, which bound Mg2+, overcoming kinetic effects. High microbial activity within groundwater systems suggest these processes may be important for dolocrete formation worldwide and that groundwater dolocretes may be more pervasive in landscapes than currently recognized. (c) 2019 John Wiley & Sons, Ltd.

KW - dolomite

KW - stable isotopes

KW - chemical sediments

KW - microbial EPS

KW - landform evolution

KW - CHANNEL IRON DEPOSITS

KW - DOLOMITE FORMATION

KW - STABLE-ISOTOPE

KW - MICROBIAL MEDIATION

KW - CARBONATE DEPOSITS

KW - PROVENCE BASIN

KW - LAGOA-VERMELHA

KW - EBRO BASIN

KW - PRECIPITATION

KW - CALCRETE

U2 - 10.1002/esp.4704

DO - 10.1002/esp.4704

M3 - Article

JO - Earth Surface Processes and Landforms

JF - Earth Surface Processes and Landforms

SN - 0197-9337

ER -