U/Th systematics of authigenic carbonates and δ¹⁸O records from Hydrate Ridge, off the coast of Oregon, USA

Uranium (U) concentrations and activity ratios (d234U) of authigenic carbonates are sensitive recorders of different fluid compositions at submarine seeps of hydrocarbon-rich fluids ("cold seeps") at Hydrate Ridge, off the coast of Oregon, USA. The low U concentrations (mean: 1.3 ± 0.4 µg/g) and high 234U values (165-317 per mil) of gas hydrate carbonates reflect the influence of sedimentary pore water indicating that these carbonates were formed under reducing conditions below or at the seafloor. Their 230Th/234U ages span a time interval from 0.8 to 6.4 ka and cluster around 1.2 and 4.7 ka. In contrast, chemoherm carbonates precipitate from marine bottom water marked by relatively high U concentrations (mean: 5.2 ± 0.8 µg/g) and a mean d234U ratio of 166 ± 3 per mil. Their U isotopes reflect the d234U ratios of the bottom water being enriched in 234U relative to normal seawater. Simple mass balance calculations based on U concentrations and their corresponding d234U ratios reveal a contribution of about 11% of sedimentary pore water to the bottom water. From the U pore water flux and the reconstructed U pore water concentration a mean flow rate of about 147 ± 68 cm/a can be estimated. 230Th/234U ages of chemoherm carbonates range from 7.3 to 267.6 ka. 230Th/234U ages of two chemoherms (Alvin and SE-Knoll chemoherm) correspond to time intervals of low sealevel stands in marine isotope stages (MIS) 2, 4, 5, 6, 7 and 8. This observation indicates that fluid flow at cold seep sites sensitively reflects pressure changes of the hydraulic head in the sediments. The d18OPDB ratios of the chemoherm carbonates support the hypothesis of precipitation during glacial times. Deviations of the chemoherm d18O values from the marine d18O record can be interpreted as to reflect temporally and spatially varying bottom water and/or vent fluid temperatures during carbonate precipitation between 2.6 and 8.6°C.

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Teichert, Barbara M A, Eisenhauer, Anton, Bohrmann, Gerhard, Haase-Schramm, Alexandra, Bock, Barbara, Linke, Peter (2003). Dataset: U/Th systematics of authigenic carbonates and δ¹⁸O records from Hydrate Ridge, off the coast of Oregon, USA. https://doi.org/10.1594/PANGAEA.769953

DOI retrieved: 2003

Additional Info

Field Value
Imported on November 30, 2024
Last update November 30, 2024
License CC-BY-3.0
Source https://doi.org/10.1594/PANGAEA.769953
Author Teichert, Barbara M A
Given Name Barbara M A
Family Name Teichert
More Authors
Eisenhauer, Anton
Bohrmann, Gerhard
Haase-Schramm, Alexandra
Bock, Barbara
Linke, Peter
Source Creation 2003
Publication Year 2003
Resource Type application/zip - filename: Teichert_2003
Subject Areas
Name: Chemistry

Name: Lithosphere

Related Identifiers
Title: U/Th systematics and ages of authigenic carbonates from Hydrate Ridge, Cascadia Margin: Recorders of fluid flow variations
Identifier: https://doi.org/10.1016/S0016-7037(03)00128-5
Type: DOI
Relation: IsSupplementTo
Year: 2003
Source: Geochimica et Cosmochimica Acta
Authors: Teichert Barbara M A , Eisenhauer Anton , Bohrmann Gerhard , Haase-Schramm Alexandra , Bock Barbara , Linke Peter .

Title: Erratum to "U/Th Systematics and ages of authigenic carbonates from Hydrate Ridge, Cascadia Margin: Recorders of fluid flow variations" [Geochimica et Cosmochimica Acta 67(20), 3845-3857]
Identifier: https://doi.org/10.1016/j.gca.2004.01.001
Type: DOI
Relation: References
Year: 2004
Source: Geochimica et Cosmochimica Acta
Authors: Teichert Barbara M A , Eisenhauer Anton , Bohrmann Gerhard , Haase-Schramm Alexandra , Bock Barbara , Linke Peter .