TY - JOUR

T1 - Uranium isotopes in marine carbonates as a global ocean paleoredox proxy

T2 - A critical review

AU - Zhang, Feifei

AU - Lenton, Timothy M.

AU - del Rey, Álvaro

AU - Romaniello, Stephen J.

AU - Chen, Xinming

AU - Planavsky, Noah J.

AU - Clarkson, Matthew O.

AU - Dahl, Tais W.

AU - Lau, Kimberly V.

AU - Wang, Wenqian

AU - Li, Ziheng

AU - Zhao, Mingyu

AU - Isson, Terry

AU - Algeo, Thomas J.

AU - Anbar, Ariel D.

PY - 2020

Y1 - 2020

N2 - The protracted oxygenation of the ocean-atmosphere system is one of the most fundamental changes to the Earth system through its history. The uranium isotopic composition (238U/235U, denoted as δ238U) of marine carbonates has been developed as a proxy to quantitatively track the timing, duration, and extent of global marine redox chemistry changes. This proxy has been applied to many critical evolutionary intervals in the last decade, significantly advancing our understanding of how life on Earth and its environment have co-evolved through geological history. Successful application of the uranium isotope paleoredox proxy requires a thorough understanding of the marine uranium budget, the processes by which seawater U-isotope signatures are recorded in marine carbonates, and the potential for alteration of these primary signatures by syn- and post-depositional diagenetic processes. Here, we provide a critical review of the U isotope proxy in marine carbonates with a focus on the current problems and areas where future work is needed to further develop this proxy. We also use a recently developed global C-P-U cycle model to illustrate that when the carbon cycle is perturbed by volcanic carbon injections, the ensuing transient relationship between seafloor anoxic area and δ238U can be complex and sometimes counter-intuitive.

AB - The protracted oxygenation of the ocean-atmosphere system is one of the most fundamental changes to the Earth system through its history. The uranium isotopic composition (238U/235U, denoted as δ238U) of marine carbonates has been developed as a proxy to quantitatively track the timing, duration, and extent of global marine redox chemistry changes. This proxy has been applied to many critical evolutionary intervals in the last decade, significantly advancing our understanding of how life on Earth and its environment have co-evolved through geological history. Successful application of the uranium isotope paleoredox proxy requires a thorough understanding of the marine uranium budget, the processes by which seawater U-isotope signatures are recorded in marine carbonates, and the potential for alteration of these primary signatures by syn- and post-depositional diagenetic processes. Here, we provide a critical review of the U isotope proxy in marine carbonates with a focus on the current problems and areas where future work is needed to further develop this proxy. We also use a recently developed global C-P-U cycle model to illustrate that when the carbon cycle is perturbed by volcanic carbon injections, the ensuing transient relationship between seafloor anoxic area and δ238U can be complex and sometimes counter-intuitive.

KW - Diagenesis

KW - OAE

KW - Oceanic anoxia

KW - Paleoenvironments

KW - Redox conditions

KW - Uranium cycle

U2 - 10.1016/j.gca.2020.05.011

DO - 10.1016/j.gca.2020.05.011

M3 - Journal article

AN - SCOPUS:85086446981

VL - 287

SP - 27

EP - 49

JO - Geochimica et Cosmochimica Acta

JF - Geochimica et Cosmochimica Acta

SN - 0016-7037

ER -