A lithium-isotope perspective on the evolution of carbon and silicon cycles

Marine sulphate captures a Paleozoic transition to a modern terrestrial weathering environment

The triple oxygen isotope composition of sulphate minerals has been used to constrain the evolution of Earth's surface environment (e.g., pO2, pCO2 and gross primary productivity) throughout the Proterozoic Eon. This approach presumes the incorporation of atmospheric O2 atoms into riverine sulphate via the oxidative weathering of pyrite. However, this is not borne out in recent geological or modern sulphate records, where an atmospheric signal is imperceptible and where terrestrial pyrite weathering occurs predominantly in bedrock fractures that are physically more removed from atmospheric O2. To better define the transition from a Proterozoic to a modern-like weathering regime, here we present new measurements from twelve marine evaporite basins spanning the Phanerozoic. These data display a step-like transition in the triple oxygen isotope composition of evaporite sulphate during the mid-Paleozoic (420 to 387.7 million years ago). We propose that the evolution of early root systems deepened the locus of pyrite oxidation and reduced the incorporation of O2 into sulphate. Further, the early Devonian proliferation of land plants increased terrestrial organic carbon burial, releasing free oxygen that fueled increased redox recycling of soil-bound iron and resulted in the final rise in pO2 to modern-like levels.

Hydrogeochemical mechanism of Li-Cs-rich thermal springs in the Karakoram Fault, Qinghai-Xizang Plateau: New insights from multiple stable isotopes

High lithium (Li) and cesium (Cs) concentrations in the Qinghai-Xizang Plateau thermal springs pose environmental and health challenges, but their origins and enrichment mechanisms remain unclear. This study focuses on the Sogdoi geothermal field, located along the southern Karakoram Fault, to investigate these processes. Multi-isotope analyses (H, O, Li, Sr) reveal that Li and Cs predominantly originate from the host rocks, especially granitoids and meta-sedimentary rocks, rather than from magmatic fluids. We propose a two-stage enrichment process mechanism that includes water-rock interactions and steam loss (~22 %) as water ascends. The geothermal field contains three distinct spring groups, all sourced from a common parent geothermal fluid at ~7 km depth with temperatures around 200 °C. Geochemical variations across groups reflect different degrees of conductive cooling, steam loss, and cold water dilution. Group I (Li: 45.21-51.93 mg/L, Cs: 27.37-29.39 mg/L, 87Sr/86Sr: 0.717-0.725, δ7Li: 1.45-1.74 ‰) represents deep fluids with minor dilution. Group II (Li: 32.16-39.98 mg/L, Cs: 28.72-33.91 mg/L, 87Sr/86Sr: 0.710-0.712, δ7Li: 1.64-1.79 ‰) and Group III (Li: 21.49-22.37 mg/L, Cs: 6.56-6.79 mg/L, 87Sr/86Sr: ~0.709, δ7Li: 4.22 ‰) show increasing dilution effects. Our findings indicate that Sr isotopes are highly sensitive to cold water mixing, while Li isotopes demonstrate greater resistance but are more susceptible to mineral adsorption. The binary Li-Sr isotope mixing model is more effective than single-isotope models in discerning mixing effects. It is crucial to select samples that are minimally affected by cold water intrusion to accurately trace fluid sources and their evolution. The anomalous Cs concentrations across groups are likely due to adsorption processes, as evidenced by decreasing Cs/Na ratios. We propose that deep faults are crucial in forming Li-Cs-rich thermal springs by enabling the deep circulation of water. This study provides insights into the hydrogeochemical mechanisms of Li and Cs in geothermal fluids, contributing to resource exploitation and environmental management.

Low-Consumption and High-Efficiency Isotope Analysis by Microultrasonic Single-Droplet Nebulization Sampling Multicollector Inductively Coupled Plasma Mass Spectrometry

Metal stable isotopes are increasingly applied in various fields, including planetary science and medical research, highlighting the need for isotope analysis methods capable of handling precious and microvolume samples. This study introduces a novel, low-consumption, high-efficiency isotope analysis method using MC-ICP-MS based on microultrasonic single-droplet nebulization (MUSDN). The proposed MUSDN enables the complete nebulization of microliter-sized droplets, delivering high-sensitivity transient analytical signals with a duration of several seconds. Under optimized conditions, MUSDN exhibited significantly enhanced sensitivity compared to conventional pneumatic nebulization, achieving 17-fold and 12-fold improvements for 7Li and 63Cu, respectively. The achieved external precisions (2SD) for δ7Li and δ65Cu were 0.3 and 0.08‰, with single analysis consuming only 1 ng of Li and 2 ng of Cu, respectively. This represents a reduction in sample consumption by 1-2 orders of magnitude compared to conventional PN-MC-ICP-MS while also improving the analysis speed by at least 10-fold due to rapid residual washout. Furthermore, our method demonstrated superior δ65Cu analytical precision compared to other high-sensitivity transient analysis methods (0.19‰ with a laser ablation system) with similar sample consumption. Finally, the accuracy of the proposed method was validated through the analysis of geological CRMs, serum CRMs, in-house standard samples, and a series of real serum samples. This novel isotope analysis method provides a promising approach for isotope applications involving precious and microvolume samples.

Gill B, Nolan M, Kaufman AJ, Luo T, Xiao S. Lithium isotope evidence for a plumeworld ocean in the aftermath of the Marinoan snowball Earth

The snowball Earth hypothesis predicts that continental chemical weathering diminished substantially during, but rebounded strongly after, the Marinoan ice age some 635 Mya. Defrosting the planet would result in a plume of fresh glacial meltwater with a different chemical composition from underlying hypersaline seawater, generating both vertical and lateral salinity gradients. Here, we test the plumeworld hypothesis using lithium isotope compositions in the Ediacaran Doushantuo cap dolostone that accumulated in the aftermath of the Marinoan snowball Earth along a proximal-distal (nearshore-offshore) transect in South China. Our data show an overall decreasing δ7Li trend with distance from the shoreline, consistent with the variable mixing of a meltwater plume with high δ7Li (due to incongruent silicate weathering on the continent) and hypersaline seawater with low δ7Li (due to synglacial distillation). The evolution of low δ7Li of synglacial seawater, as opposed to the modern oceans with high δ7Li, was likely driven by weak continental chemical weathering coupled with strong reverse weathering on the seafloor underneath silica-rich oceans. The spatial pattern of δ7Li is also consistent with the development and then collapse of the meltwater plume that occurred at the time scale of cap dolostone accumulation. Therefore, the δ7Li data are consistent with the plumeworld hypothesis, considerably reduced chemical weathering on the continent during the Marinoan snowball Earth, and enhanced reverse weathering on the seafloor of Precambrian oceans.

Utica/Point Pleasant brine isotopic compositions (δ7Li, δ11B, δ138Ba) elucidate mechanisms of lithium enrichment in the Appalachian Basin

Global Li production will require a ∼500 % increase to meet 2050 projected energy storage demands. One potential source is oil and gas wastewater (i.e., produced water or brine), which naturally has high total dissolved solids (TDS) concentrations, that can also be enriched in Li (>100 mg/L). Understanding the sources and mechanisms responsible for high naturally-occurring Li concentrations can aid in efficient targeting of these brines. The isotopic composition (δ7Li, δ11B, δ138Ba) of produced water and core samples from the Utica Shale and Point Pleasant Formation (UPP) in the Appalachian Basin, USA indicates that depth-dependent thermal maturity and water-rock interaction, including diagenetic clay mineral transformations, likely control Li concentrations. A survey of Li content in produced waters throughout the USA indicates that Appalachian Basin brines from the Marcellus Shale to the UPP have the potential for economic resource recovery.

Controls on authigenic mineralization in experimental Ediacara-style preservation

The earliest evidence of complex macroscopic life on Earth is preserved in Ediacaran-aged siliciclastic deposits as three-dimensional casts and molds, known as Ediacara-style preservation. The mechanisms that led to this extraordinary preservation of soft-bodied organisms in fine- to medium-grained sandstones have been extensively debated. Ediacara-style fossilization is recorded in a variety of sedimentary facies characterized by clean quartzose sandstones (as in the eponymous Ediacara Member) as well as less compositionally mature, clay-rich sandstones and heterolithic siliciclastic deposits. To investigate this preservational process, we conducted experiments using different mineral substrates (quartzose sand, kaolinite, and iron oxides), a variety of soft-bodied organisms (microalgae, cyanobacteria, marine invertebrates), and a range of estimates for Ediacaran seawater dissolved silica (DSi) levels (0.5-2.0 mM). These experiments collectively yielded extensive amorphous silica and authigenic clay coatings on the surfaces of organisms and in intergranular pore spaces surrounding organic substrates. This was accompanied by a progressive drawdown of the DSi concentration of the experimental solutions. These results provide evidence that soft tissues can be rapidly preserved by silicate minerals precipitated under variable substrate compositions and a wide range of predicted scenarios for Ediacaran seawater DSi concentrations. These observations suggest plausible mechanisms explaining how interactions between sediments, organic substrates, and seawater DSi played a significant role in the fossilization of the first complex ecosystems on Earth.

Lithium isotopic constraints on the evolution of continental clay mineral factory and marine oxygenation in the earliest Paleozoic Era

The evolution of oxygen cycles on Earth's surface has been regulated by the balance between molecular oxygen production and consumption. The Neoproterozoic-Paleozoic transition likely marks the second rise in atmospheric and oceanic oxygen levels, widely attributed to enhanced burial of organic carbon. However, it remains disputed how marine organic carbon production and burial respond to global environmental changes and whether these feedbacks trigger global oxygenation during this interval. Here, we report a large lithium isotopic and elemental dataset from marine mudstones spanning the upper Neoproterozoic to middle Cambrian [~660 million years ago (Ma) to 500 Ma]. These data indicate a dramatic increase in continental clay formation after ~525 Ma, likely linked to secular changes in global climate and compositions of the continental crust. Using a global biogeochemical model, we suggest that intensified continental weathering and clay delivery to the oceans could have notably increased the burial efficiency of organic carbon and facilitated greater oxygen accumulation in the earliest Paleozoic oceans.

Distinctive volcanic ash-rich lacustrine shale deposition related to chemical weathering intensity during the Late Triassic: Evidence from lithium contents and isotopes

The Late Triassic Carnian Pluvial Episode (CPE) witnessed enormous climate change closely associated with volcanic activity. However, the coupling relationship between volcanic activity and climate change, which may be linked to chemical weathering, has not yet been fully uncovered. We used lithium contents and isotopes of volcanic ash (VA)-bearing lacustrine shale to constrain their deposition pathways and response to climate changes, i.e., weathering intensity, during the Late Triassic era. Elevated δ7Li (i.e., >2.5‰) and low Li contents (i.e., <65 microgram per gram) in shale likely document the direct depositing of volcanic lithium from airborne VA, which mainly inherited Earth's interior δ7Li signal. By contrast, shale yields markedly high lithium contents (i.e., >135 microgram per gram), alongside relatively low δ7Li (i.e., <0‰), likely implying waterborne VA dominated by intensified weathering under a super humidity climate. Hence, this study provides evidence for the differential VA-rich shale deposition model related to chemical weathering states synchronous with climate changes during the CPE period.

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

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 (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 past 2 billion years using marine halite fluid inclusions and sedimentary dolostones. The data show that δ26Mgsw decreased, with fluctuations, by about 1.4‰ from the Paleoproterozoic to the present time. Mass balance calculations based on this δ26Mgsw 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.

Oxygen isotope ensemble reveals Earth's seawater, temperature, and carbon cycle history

Earth's persistent habitability since the Archean remains poorly understood. Using an oxygen isotope ensemble approach-comprising shale, iron oxide, carbonate, silica, and phosphate records-we reconcile a multibillion-year history of seawater δ18O, temperature, and marine and terrestrial clay abundance. Our results reveal a rise in seawater δ18O and a temperate Proterozoic climate distinct to interpretations of a hot early Earth, indicating a strongly buffered climate system. Precambrian sediments are enriched in marine authigenic clay, with prominent reductions occurring in concert with Paleozoic and Cenozoic cooling, the expansion of siliceous life, and the radiation of land plants. These findings support the notion that shifts in the locus and extent of clay formation contributed to seawater 18O enrichment, clement early Earth conditions, major climate transitions, and climate stability through the reverse weathering feedback.

High precision measurements of lithium isotopic composition at sub-nanogram by MC-ICP-MS with membrane desolvation

The geochemistry of Li and Li isotopes is a promising tracer of chemical weathering processes for both modern and ancient times. Therefore, accurate and precise determination of the isotopic composition of Li is required for a large variety of complex geological samples with different Li concentrations and matrix/Li ratios. Especially, geochemical studies of precious geological samples with ultra-low lithium content and high matrix. In this study, the accuracy and the precision corresponding to Li isotopic measurements of low-level samples using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) with membrane desolvation introduction system was evaluated. The method of MC-ICP-MS with membrane desolvation and a high-sensitivity X-skimmer cone, together with a simple one-step column separation enabled the high-precision isotopic analysis of Li quantities as small as 2 ng. The long-term instrumental external reproducibility of δ7Li values for the L-SVEC and SPEX-Li were 0.0 ± 0.1‰ (n = 20) and 12.1 ± 0.4‰ (n = 20), respectively. Based on the measurements on a series of international reference materials over the last two years. The measured δ7Li values for the standards with a variety of matrices, including BHVO-2, AGV-2 and seawater (NASS-6). The δ7Li values of BHVO-2 (4.58 ± 0.35‰), AGV-2 (6.85 ± 0.40‰) and NASS-6 (30.88 ± 0.20‰) are in agreement with the published data within the uncertainty. We also present analytical results for South China Sea surface seawater water, meteorite, limestones and rain water. These results demonstrate the validity of the method for obtaining highly precise and accurate outcomes.

Enhanced clay formation key in sustaining the Middle Eocene Climatic Optimum

The Middle Eocene Climatic Optimum (around 40 million years ago) was a roughly 400,000-year-long global warming phase associated with an increase in atmospheric CO2 concentrations and deep-ocean acidification that interrupted the Eocene's long-term cooling trend. The unusually long duration, compared with early Eocene global warming phases, is puzzling as temperature-dependent silicate weathering should have provided a negative feedback, drawing down CO2 over this timescale. Here we investigate silicate weathering during this climate warming event by measuring lithium isotope ratios (reported as δ7Li), which are a tracer for silicate weathering processes, from a suite of open-ocean carbonate-rich sediments. We find a positive δ7Li excursion-the only one identified for a warming event so far -of ~3‰. Box model simulations support this signal to reflect a global shift from congruent weathering, with secondary mineral dissolution, to incongruent weathering, with secondary mineral formation. We surmise that, before the climatic optimum, there was considerable soil shielding of the continents. An increase in continental volcanism initiated the warming event, but it was sustained by an increase in clay formation, which sequestered carbonate-forming cations, short-circuiting the carbonate-silicate cycle. Clay mineral dynamics may play an important role in the carbon cycle for climatic events occurring over intermediate (i.e., 100,000 year) timeframes.

Revisiting marine redox conditions during the Ediacaran Shuram carbon isotope excursion

The Neoproterozoic carbonate record contains multiple carbon isotope anomalies, which are the subject of intense debate. The largest of these anomalies, the Shuram excursion (SE), occurred in the mid-Ediacaran (~574-567 Ma). Accurately reconstructing marine redox landscape is a clear path toward making sense of the mechanism that drives this δ¹³ C anomaly. Here, we report new uranium isotopic data from the shallow-marine carbonates of the Wonoka Formation, Flinders Ranges, South Australia, where the SE is well preserved. Our data indicate that the δ²³⁸ U trend during the SE is highly reproducible across globally disparate sections from different depositional settings. Previously, it was proposed that the positive shift of δ²³⁸ U values during the SE suggests an extensive, near-modern level of marine oxygenation. However, recent publications suggest that the fractionation of uranium isotopes in ferruginous and anoxic conditions is comparable, opening up the possibility of non-unique interpretations of the carbonate uranium isotopic record. Here, we build on this idea by investigating the SE in conjunction with additional geochemical proxies. Using a revised uranium isotope mass balance model and an inverse stochastic carbon cycle model, we reevaluate models for δ¹³ C and δ²³⁸ U trends during the SE. We suggest that global seawater δ²³⁸ U values during the SE could be explained by an expansion of ferruginous conditions and do not require a near-modern level of oxygenation during the mid-Ediacaran.

Biological fractionation of lithium isotopes by cellular Na+/H+ exchangers unravels fundamental transport mechanisms

Lithium (Li) has a wide range of uses in science, medicine, and industry, but its isotopy is underexplored, except in nuclear science and in geoscience. ⁶Li and ⁷Li isotopic ratio exhibits the second largest variation on earth's surface and constitutes a widely used tool for reconstructing past oceans and climates. As large variations have been measured in mammalian organs, plants or marine species, and as ⁶Li elicits stronger effects than natural Li (∼95% ⁷Li), a central issue is the identification and quantification of biological influence of Li isotopes distribution. We show that membrane ion channels and Na⁺-Li⁺/H⁺ exchangers (NHEs) fractionate Li isotopes. This systematic ⁶Li enrichment is driven by membrane potential for channels, and by intracellular pH for NHEs, where it displays cooperativity, a hallmark of dimeric transport. Evidencing that transport proteins discriminate between isotopes differing by one neutron opens new avenues for transport mechanisms, Li physiology, and paleoenvironments.

Li isotopic seasonality in a small catchment at the northeastern Tibetan Plateau: Roles of hydrology and temperature dependency

Silicate weathering is critical to sustain our habitable planet. Lithium (Li) isotopes enable us to investigate the nature of silicate weathering. A number of riverine Li isotope (δ⁷Li_rw) investigations have been made from polar to equatorial terrains, but there remains no consensus about the controlling mechanisms of both weathering and δ⁷Li_rw. Here we investigated δ⁷Li_rw response to climate by collecting weekly river water samples in a small catchment (the Buha River within the Lake Qinghai basin) on the northeastern Tibetan Plateau, with stable tectonic, lithology, and topography. In the hydrology year of 2007 of the Buha River, we find that during the dry seasons, δ⁷Li_rw ratios show temperature dependency typically, when the groundwater fed the river. During the monsoon seasons, δ⁷Li_rw were obviously lower than the temperature dependency predicted values, when abundant rock dissolved and thereby fresh Li release into rivers. We propose that the hydrology and temperature dependency together play important roles in regulating δ⁷Li_rw ratios in such an alpine small catchment. The mechanism is that long residence time facilitates the equilibrium chemical and Li isotopic fractionation during the dry seasons, so a temperature dependency of δ⁷Li_rw is achieved. In contrast, rapid erosion and weathering contribution of fresh rock-like δ⁷Li to river water would significantly decrease δ⁷Li_rw ratios during the monsoon seasons. This hypothesis can better interpret previously reported data of seasonal δ⁷Li_rw variation, as a superposition between temperature dependency and hydrology regulation on silicates weathering in the small catchments besides tectonics.

The evolution of the marine carbonate factory

Calcium carbonate formation is the primary pathway by which carbon is returned from the ocean-atmosphere system to the solid Earth^1,2. The removal of dissolved inorganic carbon from seawater by precipitation of carbonate minerals-the marine carbonate factory-plays a critical role in shaping marine biogeochemical cycling^1,2. A paucity of empirical constraints has led to widely divergent views on how the marine carbonate factory has changed over time^3-5. Here we use geochemical insights from stable strontium isotopes to provide a new perspective on the evolution of the marine carbonate factory and carbonate mineral saturation states. Although the production of carbonates in the surface ocean and in shallow seafloor settings have been widely considered the predominant carbonate sinks for most of the history of the Earth⁶, we propose that alternative processes-such as porewater production of authigenic carbonates-may have represented a major carbonate sink throughout the Precambrian. Our results also suggest that the rise of the skeletal carbonate factory decreased seawater carbonate saturation states.

Hydrological control of river and seawater lithium isotopes

Seawater lithium isotopes (δ7Li) record changes over Earth history, including a ∼9‰ increase during the Cenozoic interpreted as reflecting either a change in continental silicate weathering rate or weathering feedback strength, associated with tectonic uplift. However, mechanisms controlling the dissolved δ7Li remain debated. Here we report time-series δ7Li measurements from Tibetan and Pamir rivers, and combine them with published seasonal data, covering small (<102  km2) to large rivers (>106 km2). We find seasonal changes in δ7Li across all latitudes: dry seasons consistently have higher δ7Li than wet seasons, by -0.3‰ to 16.4‰ (mean 5.0 ± 2.5‰). A globally negative correlation between δ7Li and annual runoff reflects the hydrological intensity operating in catchments, regulating water residence time and δ7Li values. This hydrological control on δ7Li is consistent across climate events back to ~445 Ma. We propose that hydrological changes result in shifts in river δ7Li and urge reconsideration of its use to examine past weathering intensity and flux, opening a new window to reconstruct hydrological conditions.

The Invasion of the Land in Deep Time: Integrating Paleozoic Records of Paleobiology, Ichnology, Sedimentology, and Geomorphology

The invasion of the land was a complex, protracted process, punctuated by mass extinctions, that involved multiple routes from marine environments. We integrate paleobiology, ichnology, sedimentology, and geomorphology to reconstruct Paleozoic terrestrialization. Cambrian landscapes were dominated by laterally mobile rivers with unstable banks in the absence of significant vegetation. Temporary incursions by arthropods and worm-like organisms into coastal environments apparently did not result in establishment of continental communities. Contemporaneous lacustrine faunas may have been inhibited by limited nutrient delivery and high sediment loads. The Ordovician appearance of early land plants triggered a shift in the primary locus of the global clay mineral factory, increasing the amount of mudrock on the continents. The Silurian-Devonian rise of vascular land plants, including the first forests and extensive root systems, was instrumental in further retaining fine sediment on alluvial plains. These innovations led to increased architectural complexity of braided and meandering rivers. Landscape changes were synchronous with establishment of freshwater and terrestrial arthropod faunas in overbank areas, abandoned fluvial channels, lake margins, ephemeral lakes, and inland deserts. Silurian-Devonian lakes experienced improved nutrient availability, due to increased phosphate weathering and terrestrial humic matter. All these changes favoured frequent invasions to permament establishment of jawless and jawed fishes in freshwater habitats and the subsequent tetrapod colonization of the land. The Carboniferous saw rapid diversification of tetrapods, mostly linked to aquatic reproduction, and land plants, including gymnosperms. Deeper root systems promoted further riverbank stabilization, contributing to the rise of anabranching rivers and braided systems with vegetated islands. New lineages of aquatic insects developed and expanded novel feeding modes, including herbivory. Late Paleozoic soils commonly contain pervasive root and millipede traces. Lacustrine animal communities diversified, accompanied by increased food-web complexity and improved food delivery which may have favored permanent colonization of offshore and deep-water lake environments. These trends continued in the Permian, but progressive aridification favored formation of hypersaline lakes, which were stressful for colonization. The Capitanian and end-Permian extinctions affected lacustrine and fluvial biotas, particularly the invertebrate infauna, although burrowing may have allowed some tetrapods to survive associated global warming and increased aridification.

Impact of green clay authigenesis on element sequestration in marine settings

Retrograde clay mineral reactions (reverse weathering), including glauconite formation, are first-order controls on element sequestration in marine sediments. Here, we report substantial element sequestration by glauconite formation in shallow marine settings from the Triassic to the Holocene, averaging 3 ± 2 mmol·cm⁻²·kyr⁻¹ for K, Mg and Al, 16 ± 9 mmol·cm⁻²·kyr⁻¹ for Si and 6 ± 3 mmol·cm⁻²·kyr⁻¹ for Fe, which is ~2 orders of magnitude higher than estimates for deep-sea settings. Upscaling of glauconite abundances in shallow-water (0–200 m) environments predicts a present-day global uptake of ~≤ 0.1 Tmol·yr⁻¹ of K, Mg and Al, and ~0.1–0.4 Tmol·yr⁻¹ of Fe and Si, which is ~half of the estimated Mesozoic elemental flux. Clay mineral authigenesis had a large impact on the global marine element cycles throughout Earth’s history, in particular during ‘greenhouse’ periods with sea level highstand, and is key for better understanding past and present geochemical cycling in marine sediments.

Here the authors show that reverse weathering reactions, such as the formation of glauconite minerals, are first-order controls on element sequestration in shallow marine sediments throughout Earth history, in particular during greenhouse periods with sea level highstand.