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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∆47record 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 TΔ47record 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.

Moisture significantly affects the adsorption capability of gas shales for methane (CH4), the main component of shale gas. Primary moisture, i.e., the moisture that exists in in situ shale reservoirs, is therefore crucial to estimate and produce shale gas resource. Aiming to understand the influences of primary moisture on CH4 adsorption on shale samples, the occurrence of primary moisture in shales gathered from the Lower Silurian Longmaxi Formation located in southern Sichuan Basin of China was experimentally investigated. Additionally, the primary moisture dependence of CH4 adsorption equilibrium and thermodynamics of shales was investigated. Results indicate that the primary moisture contents of the four shale samples vary between 0.64 and 0.82% (mass percentage), positively correlated with the clay mineral content of shale samples. The adsorption equilibrium behavior regarding water vapor on shales well follows the modified Brunauer–Emmett–Teller (BET) equation. The water vapor is typically adsorbed onto the primary adsorption sites of shale samples, i.e., the oxygenic functional groups consisting of COOH, conjugated CO, and highly conjugated CO, and the secondary adsorption sites, i.e., the previously adsorbed water molecules and clay minerals. The pores with pore diameter less than 4 nm of shales are the main accommodation space for primary moisture. The adsorption equilibrium of CH4 on primary moisture-containing shales well obeys the Ono–Kondo lattice equation. On the basis of the modeling results, the primary moisture causes a remarkable reduction in maximum CH4 adsorption capacity of shale samples by 12.86–45.45%. Moreover, the primary moisture reduces the isosteric heat of CH4 adsorption on shale samples. In summary, the primary moisture in gas shales decreases the adsorption affinity between CH4 and shale samples. Therefore, focusing on the effects of primary moisture on CH4 adsorption on shales is vital to better estimate and produce shale gas resource.

Background: Metabolic remodeling precedes most alterations during cardiac hypertrophic growth under hemodynamic stress. The elevation of glucose utilization has been recognized as a hallmark of metabolic remodeling. However, its role in cardiac hypertrophic growth and heart failure in response to pressure overload remains to be fully illustrated. Here, we aimed to dissect the role of cardiac PKM1 (pyruvate kinase muscle isozyme 1) in glucose metabolic regulation and cardiac response under pressure overload. Methods: Cardiac specific deletion of PKM1 was achieved by crossing the floxed PKM1 mouse model with the cardiomyocyte-specific Cre transgenic mouse. PKM1 transgenic mice were generated under the control of tetracycline response elements, and cardiac specific overexpression of PKM1 was induced by doxycycline administration in adult mice. Pressure overload was triggered by transverse aortic constriction (TAC). Primary neonatal rat ventricular myocytes were used to dissect molecular mechanisms. Moreover, metabolomics and NMR spectroscopy analyses were conducted to determine cardiac metabolic flux in response to pressure overload. Results: We found that PKM1 expression is reduced in failing human and mouse hearts. Importantly, cardiomyocyte-specific deletion of PKM1 exacerbates cardiac dysfunction and fibrosis in response to pressure overload. Inducible overexpression of PKM1 in cardiomyocytes protects the heart against TAC-induced cardiomyopathy and heart failure. At the mechanistic level, PKM1 is required for the augmentation of glycolytic flux, mitochondrial respiration, and ATP production under pressure overload. Furthermore, deficiency of PKM1 causes a defect in cardiomyocyte growth and a decrease in pyruvate dehydrogenase complex activity at both in vitro and in vivo levels. Conclusions: These findings suggest that PKM1 plays an essential role in maintaining a homeostatic response in the heart under hemodynamic stress.

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Large datasets increasingly provide critical insights into crustal and surface processes on Earth. These data come in the form of published and contributed observations, which often include associated metadata. Even in the best-case scenario of a carefully curated dataset, it may be nontrivial to extract meaningful analyses from such compilations, and choices made with respect to filtering, resampling, and averaging can affect the resulting trends and any interpretation(s) thereof. As a result, a thorough understanding of how to digest, process, and analyze large data compilations is required. Here, we present a generalizable workflow developed using the Sedimentary Geochemistry and Paleoenvironments Project database. We demonstrate the effects of filtering and weighted resampling on Al 2 O 3 and U contents, two representative geochemical components of interest in sedimentary geochemistry (one major and one trace element, respectively). Through our analyses, we highlight several methodological challenges in a "bigger data" approach to Earth science. We suggest that, with slight modifications to our workflow, researchers can confidently use large collections of observations to gain new insights into processes that have shaped Earth's crustal and surface environments. 1 Supplemental Material: table of valid lithologies; map depicting sample locations; crossplot illustrating analytical uncertainty; flowchart of the proposed workflow; histograms showing the effects of progressive filtering, the distribution of spatial and age scales, and proximity and probability values; and results of sensitivity tests.

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The nanometer-scaled pore systems of gas shale reservoirs have a prominent contribution for gas storage. To obtain information about the characteristics of the nanopore structure within lacustrine organic-rich shales during their thermal evolution, artificial shale samples with different thermal maturities were obtained from a hydrous pyrolysis experiment. Nitrogen adsorption, field emission scanning electron microscopy, and porosity tests were used to investigate the characteristic pore structures of lacustrine shales with different thermal maturities from the Minhe Basin. The results show that the total organic carbon content decreased from 41.89% (unheated) to 27.7% (370 C) and that organic pores, intragranular pores of pyrite, and intergranular pores of clay minerals began to form with an increase in the simulated temperature and pressure. The porosity increased from 3.57% (unheated) to 26.09% (350 C) and then decreased to 20% (370 C) on the whole. The pore sizes were distributed from 1.7 to 500 nm, and the average pore diameter first showed a decreasing trend and then an increasing trend. The cumulative pore volume and cumulative specific surface area both presented a slowly increasing trend from an unheated status to 325 C, exhibited a rapid increase at 350 C, and then showed a slow increase at 370 C. This study could provide a reference for the exploration of shale gas in lacustrine shales with different thermal maturities.