TY - JOUR

T1 - Ikaite Abundance Controlled by Porewater Phosphorus Level: Potential Links to Dust and Productivity

AU - Zhou, Xiaoli

AU - Lu, Zunli

AU - Rickaby, Rosalind E.M.

AU - Domack, Eugene W.

AU - Wellner, Julia S.

AU - Kennedy, Hilary

PY - 2015/5

Y1 - 2015/5

N2 - Glendonites are pseudomorphs of the mineral ikaite (CaCO3·6H2O) after loss of hydration water and occur in distinctiveeuhedral crystalline forms, sometimes clustered as rosettes of up to tens of centimeters in diameter. While itis generally accepted that organic-rich environments, methane seeps, and high phosphate levels are important forikaite formation, glendonite occurrences in ancient sedimentary sequences are widely considered to reflect nearfreezingtemperatures, even at high latitudes during periods of greenhouse climates. To fully understand the paleoenvironmentalsignificance of glendonites, a comprehensive examination of the modern ikaite setting is necessary.Temperature is the most important parameter that has been quantitatively constrained for the presence of ikaite. Lowbottom-water temperature, while a required condition for formation of the mineral, is not adequate for its growth;other controls are necessary to explain the absence of ikaite in many cold environments. In this study, we discuss thecontrol of carbonate chemistry on ikaite formation. Our compilation of geochemical data from sediment cores withwell-preserved ikaite provide further evidence for the importance of phosphate. A phosphate concentration above∼400 mM in shallow and cold porewater may be the requisite parameter for extensive ikaite precipitation. Thus,abundant glendonites in ancient successions mark past periods and regions of elevated porewater phosphorus concentrations,which may also be related to high surface productivity and/or iron fertilization

AB - Glendonites are pseudomorphs of the mineral ikaite (CaCO3·6H2O) after loss of hydration water and occur in distinctiveeuhedral crystalline forms, sometimes clustered as rosettes of up to tens of centimeters in diameter. While itis generally accepted that organic-rich environments, methane seeps, and high phosphate levels are important forikaite formation, glendonite occurrences in ancient sedimentary sequences are widely considered to reflect nearfreezingtemperatures, even at high latitudes during periods of greenhouse climates. To fully understand the paleoenvironmentalsignificance of glendonites, a comprehensive examination of the modern ikaite setting is necessary.Temperature is the most important parameter that has been quantitatively constrained for the presence of ikaite. Lowbottom-water temperature, while a required condition for formation of the mineral, is not adequate for its growth;other controls are necessary to explain the absence of ikaite in many cold environments. In this study, we discuss thecontrol of carbonate chemistry on ikaite formation. Our compilation of geochemical data from sediment cores withwell-preserved ikaite provide further evidence for the importance of phosphate. A phosphate concentration above∼400 mM in shallow and cold porewater may be the requisite parameter for extensive ikaite precipitation. Thus,abundant glendonites in ancient successions mark past periods and regions of elevated porewater phosphorus concentrations,which may also be related to high surface productivity and/or iron fertilization

U2 - 10.1086/681918

DO - 10.1086/681918

M3 - Article

VL - 123

SP - 269

EP - 281

JO - Journal of Geology

JF - Journal of Geology

SN - 0022-1376

IS - 3

ER -