Mg isotope evidence for restriction events within the Paleotethys ocean around the Permian-Triassic transition

Hu, Zhongya; Li, Weiqiang; Zhang, Hua; Krainer, Karl; Zheng, Qi; Xia, Zhiguang; Hu, Wenxuan; Shen, Shu-zhong

doi:10.1016/j.epsl.2020.116704

Cited by 20 publications

(8 citation statements)

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“…Isotopic evolution of Mg in dolomitization fluids can occur along a diffusion/advection profile on a scale of meters to hundreds of meters ( 17 , 25 , 26 ) or across a carbonate platform on a scale of hundreds of kilometers (Supplementary Materials and figs. S4 and S5) or even within an enclosed basin on the continental scale ( 19 , 27 ). Nonetheless, dolomitization invariably removes light Mg isotopes from the fluid, elevating the δ 26 Mg value of the remaining fluid and the δ 26 Mg values of dolomite precipitated from that fluid ( 23 , 24 ).…”

Section: Resultsmentioning

confidence: 99%

The evolution of Earth’s surficial Mg cycle over the past 2 billion years

Xia,

Li,

et al. 2024

Sci. Adv.

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The surficial cycling of Mg is coupled with the global carbon cycle, a predominant control of Earth’s climate. However, how Earth’s surficial Mg cycle evolved with time has been elusive. Magnesium isotope signatures of seawater (δ 26 Mg sw ) track the surficial Mg cycle, which could provide crucial information on the carbon cycle in Earth’s history. Here, we present a reconstruction of δ 26 Mg sw evolution over the past 2 billion years using marine halite fluid inclusions and sedimentary dolostones. The data show that δ 26 Mg sw decreased, with fluctuations, by about 1.4‰ from the Paleoproterozoic to the present time. Mass balance calculations based on this δ 26 Mg sw record reveal a long-term decline in net dolostone burial (NDB) over the past 2 billion years, due to the decrease in dolomitization in the oceans and the increase in dolostone weathering on the continents. This underlines a previously underappreciated connection between the weathering-burial cycle of dolostone and the Earth’s climate on geologic timescales.

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Section: Resultsmentioning

confidence: 99%

The evolution of Earth’s surficial Mg cycle over the past 2 billion years

Xia,

Li,

et al. 2024

Sci. Adv.

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“…First, basin restriction may create locally elevated saturation states in surface seawater. A recent Mg‐isotope study indicates transient ocean restriction in the Palaeotethys (Hu et al ., 2021) that may have enhanced the development of extremely warm seawater temperatures (Sun et al ., 2012). Second, a favourable depositional environment for giant ooids to grow may also play a role.…”

Section: Discussionmentioning

confidence: 99%

Quantitative evaluation of the roles of ocean chemistry and climate on ooid size across the Phanerozoic: Global versus local controls

Koeshidayatullah

Trower

et al. 2022

Sedimentology

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Ooid size in natural systems can be predicted based on the expected equilibrium between precipitation and abrasion rates. Therefore, ooid size distributions may enable quantitative inferences about past ocean and climate conditions from sedimentology that complement insights from geochemistry. A few previous attempts have been made to compile information on ooid sizes across the Phanerozoic, but no systematic ooid size dataset is available and equilibrium models of ooid growth have not been explored comprehensively. In this study, convolutional neural network-based segmentation was used to automate ooid size measurement and provide a systematic sampling of ooid sizes spanning the Phanerozoic. This data set is coupled with Monte Carlo simulations to quantitatively explore the interplay between three testable physicochemical parameters (long-term average carbonate saturation state, bed shear velocity and intermittency of transport) in determining equilibrium ooid size. The numerical model shows that a typical-sized ooid (≤1000 µm) can grow under a wide range of parameter combinations whereas giant ooids (>2000 µm) can only form under a more restricted set of circumstances. Furthermore, the model predicts that the formation of giant ooids is common when conditions favourable for rapid CaCO 3 precipitation are achieved. This finding is consistent with the naturally rare occurrences of giant ooids, which developed under exceptional environmental conditions and are primarily associated with intervals of bimineralic seas and elevated sea-surface temperature (greenhouse or transitional climate). Whereas global controls could help explain secular trends in ooid size, significant spatial variability of ooid size in several time intervals further demonstrates the importance of local environmental parameters in the growth of ooids.

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“…There is a negative correlation between Mg-K concentrations and δ 26 Mg values for the dissolved bulk halite samples (Supplementary Materials, Fig. S6), suggestive of Mg-and K-bearing salt enriched in 24 Mg.…”

Section: Reconstructing Mg Isotope History Of Seawater In the Past 2 ...mentioning

confidence: 98%

“…Isotopic evolution of Mg in dolomitization uids can occur along a diffusion/advection pro le on a scale of meters to hundreds of meters 19,23 , or across a carbonate platform on a scale of hundreds of kilometers (Supplementary Text, Fig. S4, S5), or even within an enclosed basin on the continental scale 24 . Nonetheless, dolomitization invariably removes light Mg isotopes from the uid, elevating the δ 26 Mg value of the remaining uid and the δ 26 Mg values of dolomite precipitated from that uid.…”

Section: Reconstructing Mg Isotope History Of Seawater In the Past 2 ...mentioning

confidence: 99%

“…the oceans is supplied from weathering of silicates and Mg-bearing carbonates (mainly dolomite), which have a large difference in Mg isotope ratios (expressed in delta notation: δ 26 Mg = (R sample /R standard -1)×1000, R = 26 Mg/ 24 Mg, the standard is DSM3). The majority of igneous silicate rocks have similar δ 26 Mg values that cluster around − 0.25 ± 0.07‰, whereas carbonates have much lower values of δ 26 Mg, commonly between − 1‰ and − 5‰ 14 .…”

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The evolution of Earth’s surficial Mg cycle over the past 2 billion years

Xia

et al. 2022

Preprint

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The surficial cycling of Mg is directly coupled with the global carbon cycle, a predominant control of Earth’s climate. However, how Earth’s surficial Mg cycle evolved with time had been elusive. Magnesium isotope signatures of seawater (δ26Mgsw) track the surficial Mg cycle, which could provide crucial information on the carbon cycle in Earth’s history. Here, we present a reconstruction of δ26Mgsw evolution over the last 2 billion years using marine halite fluid inclusions and sedimentary dolostones. The two independent archives yield consistent evolutionary trends of δ26Mgsw for the past 430 million years, and the dolostone records extend the δ26Mgsw curve to 2 billion years ago. Modeling results of the net CO2 sequestration efficiency (EMg−CO2) by the surficial Mg cycle based on the δ26Mgsw record reveal a secular decline EMg−CO2 during the past 2 billion years, with the periods of low EMg−CO2 coinciding with ice ages in the Phanerozoic. Our work underlines a previously under-appreciated, but indispensable role of dolostones in regulating Earth’s climate on geologic time scales.

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Mg isotope evidence for restriction events within the Paleotethys ocean around the Permian-Triassic transition

Cited by 20 publications

References 47 publications

The evolution of Earth’s surficial Mg cycle over the past 2 billion years

The evolution of Earth’s surficial Mg cycle over the past 2 billion years

Quantitative evaluation of the roles of ocean chemistry and climate on ooid size across the Phanerozoic: Global versus local controls

The evolution of Earth’s surficial Mg cycle over the past 2 billion years

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