Determining the Diagenetic Conditions of Concretion Formation: Assessing Temperatures and Pore Waters Using Clumped Isotopes

• DOI: 10.2110/jsr.2012.85
• Publication Date: 2012-12-17T23:57:23Z
• Authors: S. J. Loyd; F. A. Corsetti; J. M. Eiler; A. K. Tripati
• Keywords: Concretion

Carbonate-d 18 O paleothermometry is used in many diagenetic studies to unravel the thermal history of basins.However, this approach generally requires an assumed pore-water d (d pw ) value, a parameter that difficult quantify past regimes.In addition, processes can change original isotopic composition pore water, which further complicates assignment initial and lead erroneous temperature estimates.Here, we use clumped-isotope thermometry, proxy based on 13 C-18 bond abundance carbonate minerals, evaluate temperatures concretion formation Miocene Monterey Formation Cretaceous Holz Shale, California.These are combined with established carbonate-water fractionation factors calculate associated .Results demonstrate modify ancient confounding attempts estimate using standard approaches.Clumped-isotope-based estimates for concretions range from , 17 35uC, up 12uC higher than traditional when values equal seawater values.Calculated +0.3 +2.5% (VSMOW)-higher coeval seawater, likely due modification accompanying diagenesis sedimentary siliceous phases.Clumped-isotope Shale 33 44uC, about 15 30uC lower derived method.Calculated 25.0 22.9% reflect influx meteoric fluids.We conclude clumped isotopes both improves accuracy reconstructions provides insight into evolution during diagenesis, addressing longstanding conundrum basin-evolution research.