TY - JOUR
T1 - Testing Urey's carbonate–silicate cycle using the calcium isotopic composition of sedimentary carbonates
AU - Blättler, Clara L.
AU - Higgins, John Andrew
N1 - Funding Information:
This work was supported by a grant from the Simons Foundation ( SCOL 339006 to C.L.B.). Many samples were contributed generously to this study by: Kristin Bergmann and the members of the 2015 Agouron advanced geobiology field course, Tanja Bosak, Woody Fischer, Linda Kah, Jenn Kasbohm, Andy Knoll, Lee Kump, Francis Macdonald, Guillaume Paris, Noah Planavsky, Swapan Sahoo, Alcides da Nóbrega Sial, Erik Sperling, and Nick Swanson-Hysell. This research used samples and data provided by the International Ocean Discovery Program (IODP). Laboratory assistance was provided by Elizabeth Lundstrom and Danielle Santiago-Ramos. Appendix A
Publisher Copyright:
© 2017 Elsevier B.V.
PY - 2017/12/1
Y1 - 2017/12/1
N2 - Carbonate minerals constitute a major component of the sedimentary geological record and an archive of a fraction of the carbon and calcium cycled through the Earth's surface reservoirs for over three billion years. For calcium, carbonate minerals constitute the ultimate sink for almost all calcium liberated during continental and submarine weathering of silicate minerals. This study presents >500 stable isotope ratios of calcium in Precambrian carbonate sediments, both limestones and dolomites, in an attempt to characterize the isotope mass balance of the sedimentary carbonate reservoir through time. The mean of the dataset is indistinguishable from estimates of the calcium isotope ratio of bulk silicate Earth, consistent with the Urey cycle being the dominant mechanism exchanging calcium among surface reservoirs. The variability in bulk sediment calcium isotope ratios within each geological unit does not reflect changes in the global calcium cycle, but rather highlights the importance of local mineralogical and/or diagenetic effects in the carbonate record. This dataset demonstrates the potential for calcium isotope ratios to help assess these local effects, such as the former presence of aragonite, even in rocks with a history of neomorphism and recrystallization. Additionally, 29 calcium isotope measurements are presented from ODP (Ocean Drilling Program) Site 801 that contribute to the characterization of altered oceanic crust as an additional sink for calcium, and whose distinct isotopic signature places a limit on the importance of this subduction flux over Earth history.
AB - Carbonate minerals constitute a major component of the sedimentary geological record and an archive of a fraction of the carbon and calcium cycled through the Earth's surface reservoirs for over three billion years. For calcium, carbonate minerals constitute the ultimate sink for almost all calcium liberated during continental and submarine weathering of silicate minerals. This study presents >500 stable isotope ratios of calcium in Precambrian carbonate sediments, both limestones and dolomites, in an attempt to characterize the isotope mass balance of the sedimentary carbonate reservoir through time. The mean of the dataset is indistinguishable from estimates of the calcium isotope ratio of bulk silicate Earth, consistent with the Urey cycle being the dominant mechanism exchanging calcium among surface reservoirs. The variability in bulk sediment calcium isotope ratios within each geological unit does not reflect changes in the global calcium cycle, but rather highlights the importance of local mineralogical and/or diagenetic effects in the carbonate record. This dataset demonstrates the potential for calcium isotope ratios to help assess these local effects, such as the former presence of aragonite, even in rocks with a history of neomorphism and recrystallization. Additionally, 29 calcium isotope measurements are presented from ODP (Ocean Drilling Program) Site 801 that contribute to the characterization of altered oceanic crust as an additional sink for calcium, and whose distinct isotopic signature places a limit on the importance of this subduction flux over Earth history.
KW - Urey cycle
KW - calcium isotopes
KW - carbon cycle
KW - carbonate sediment
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U2 - 10.1016/j.epsl.2017.09.033
DO - 10.1016/j.epsl.2017.09.033
M3 - Article
AN - SCOPUS:85033666531
SN - 0012-821X
VL - 479
SP - 241
EP - 251
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
ER -