Massive formation of early diagenetic dolomite in the Ediacaran ocean : Constraints on the "dolomite problem"

Paleozoic and Precambrian sedimentary successions frequently contain massive dolomicrite [CaMg(CO3)2] units despite kinetic inhibitions to nucleation and precipitation of dolomite at Earth surface temperatures (<60 °C). This paradoxical observation is known as the "dolomite problem." Accordingly, the genesis of these dolostones is usually attributed to burial-hydrothermal dolomitization of primary limestones (CaCO3) at temperatures of >100 °C, thus raising doubt about the validity of these deposits as archives of Earth surface environments. We present a high-resolution, >63-My-long clumped-isotope temperature (TΔ47) record of shallow-marine dolomicrites from two drillcores of the Ediacaran (635 to 541 Ma) Doushantuo Formation in South China. Our T∆47 record indicates that a majority (87%) of these dolostones formed at temperatures of <100 °C. When considering the regional thermal history, modeling of the influence of solid-state reordering on our TΔ47 record further suggests that most of the studied dolostones formed at temperatures of <60 °C, providing direct evidence of a low-temperature origin of these dolostones. Furthermore, calculated δ18O values of diagenetic fluids, rare earth element plus yttrium compositions, and petrographic observations of these dolostones are consistent with an early diagenetic origin in a rock-buffered environment. We thus propose that a precursor precipitate from seawater was subsequently dolomitized during early diagenesis in a near-surface setting to produce the large volume of dolostones in the Doushantuo Formation. Our findings suggest that the preponderance of dolomite in Paleozoic and Precambrian deposits likely reflects oceanic conditions specific to those eras and that dolostones can be faithful recorders of environmental conditions in the early oceans.

Medienart:

E-Artikel

Erscheinungsjahr:

2020

Erschienen:

2020

Enthalten in:

Zur Gesamtaufnahme - volume:117

Enthalten in:

Proceedings of the National Academy of Sciences of the United States of America - 117(2020), 25 vom: 23. Juni, Seite 14005-14014

Sprache:

Englisch

Beteiligte Personen:

Chang, Biao [VerfasserIn]
Li, Chao [VerfasserIn]
Liu, Deng [VerfasserIn]
Foster, Ian [VerfasserIn]
Tripati, Aradhna [VerfasserIn]
Lloyd, Max K [VerfasserIn]
Maradiaga, Ingrid [VerfasserIn]
Luo, Genming [VerfasserIn]
An, Zhihui [VerfasserIn]
She, Zhenbing [VerfasserIn]
Xie, Shucheng [VerfasserIn]
Tong, Jinnan [VerfasserIn]
Huang, Junhua [VerfasserIn]
Algeo, Thomas J [VerfasserIn]
Lyons, Timothy W [VerfasserIn]
Immenhauser, Adrian [VerfasserIn]

Links:

Volltext

Themen:

Carbonate geochemistry
Clumped isotope
Doushantuo Formation
Early diagenesis
Early oceans
Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

Anmerkungen:

Date Completed 19.08.2020

Date Revised 08.12.2020

published: Print-Electronic

Citation Status PubMed-not-MEDLINE

doi:

10.1073/pnas.1916673117

funding:

Förderinstitution / Projekttitel:

PPN (Katalog-ID):

NLM310932009