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Triassic strata of the Yangtze Platform at Guanling contain a dolomitized interior, undolomitized margin, and partially dolomitized slope to basin margin. Dolomitized microbial laminate caps of peritidal cycles and massive dolomite with associated evaporite nodules and solution collapse breccias are consistent with penecontemporaneous tidal flat and evaporative dolomitization in the platform interior. The preferential dolomitization of the slope and basin margin (up to 7 km basinward of the margin), dolomitization along fractures, and selective dolomitization of the matrix in slope breccia that diminishes toward the margin are interpreted to have resulted from the incursion of basin-derived fluids during burial. Integrated analysis of fluid-inclusion microthermometry, oxygen, carbon, and strontium isotopes, trace element geochemistry, U-Pb age dates of carbonate phases, and burial history support the recrystallization of interior dolomite and slope to basin-margin dolomitization by brines at high temperatures during burial. The Yangtze Platform at Guanling provides an excellent example of widespread stratiform dolomitization resulting from the superposition of multiple mechanisms, including penecontemporaneous dolomitization by evaporative seawater brines, high-temperature dolomitization of the slope and basin margin by basinal brines, and high-temperature recrystallization of dolomite by brines during burial. This study provides an example that suggests that widespread stratiform dolomite may result from superposed Earth surface and high-temperature burial dolomitization processes and provides a valuable analog for other carbonate platforms in which the margin remains undolomitized while the interior and basin margin are dolomitized. Similar mechanisms likely contributed to the widespread dolomitization of platforms across the Nanpanjiang and Sichuan basins. 

Landscape properties have a profound influence on the diversity and distribution of biota, with present-day biodiversity hot spots occurring in topographically complex regions globally. Complex topography is created by tectonic processes and further shaped by interactions between climate and land-surface processes. These processes enrich diversity at the regional scale by promoting speciation and accommodating increased species richness along strong environmental gradients. Synthesis of the mammalian fossil record and a geophysical model of topographic evolution of the Basin and Range Province in western North America enable us to directly quantify relationships between mammal diversity and landscape dynamics over the past 30 million years. We analyze the covariation between tectonic history (extensional strain rates, paleotopography, and ruggedness), global temperature, and diversity dynamics. Mammal species richness and turnover exhibit stronger responses to rates of change in landscape properties than to the specific properties themselves, with peaks in diversity coinciding with high tectonic strain rates and large changes in elevation across spatial scales. 

The Great Bank of Guizhou is a 2.5 km thick isolated carbonate platform deposited during the Triassic period. The rocks preserve evidence for multiple episodes of dolomitization, spread across a range of geologic time. Different styles of dolomitization and geochemical evidence support this interpretation. Early dolomitization includes both peritidal cycle cap dolomites and large regions of massively-bedded dolomite in the platform interior, along with isolated dolomitized and partially dolomitized clasts in slope breccias derived from the platform interior. Forms of later stage dolomite include a widespread overprint and modification of massively bedded platform interior dolomites during burial; zones of pervasively dolomitized slope sediments (10s of m thick), some of which are discordant at various scales (0.1 m to 100s of m); partial dolomitization along fractures, bedding planes, and stylolites; alternating stratiform laminae of limestone and dolostone (mm to cm scale) in slope sediments; and matrix-selective dolomitization in some slope breccias. Evidence for early dolomite includes isolated clasts of dolomite in Early Triassic slope breccias surrounded by lime mudstone, pervasive dolomite in platform interior sediments, Sr-isotopes and REE signatures consistent with Early Triassic seawater, and evidence for evaporites and solution collapse breccias in the platform interior. Textures and some geochemical indicators were modified during deep burial. Evidence for later stage dolomite (Late Triassic or later) includes zones of coarse massively dolomitized slope breccias surrounded by selectively dolomitized vertical and bedding plane fractures, stylolites, and alternating stratiform laminae of limestone and dolostone; fluid-inclusions containing brine (12-16 wt. %, NaCl equivalent) with homogenization temperatures of 100°C to 180°C, and some younger (post-burial) U-Pb age dates. Early evaporative-reflux dolomitization in the platform interior likely dominated the dolomite volumetrically before it was overprinted with burial signatures. Pervasively dolomitized slope breccias surrounded by selective dolomitized areas are interpreted to be the result of intrusion of late burial dolomitizing fluids into higher permeability units. 

Tectonic activity can drive speciation and sedimentation, potentially causing the fossil and rock records to share common patterns through time. The Basin and Range of western North America arose through widespread extension and collapse of topographic highlands in the Miocene, creating numerous basins with rich mammalian fossil records. We analyzed patterns of mammalian species richness from 36 to 0 million years ago in relation to the history of sediment accumulation to test whether intervals of high species richness corresponded with elevated sediment accumulation and fossil burial in response to tectonic deformation. We found that the sedimentary record of the Basin and Range tracks the tectonic evolution of landscapes, whereas species-richness trends reflect actual increased richness in the Miocene rather than increased fossil burial. The sedimentary record of the region broadly determines the preservation of the fossil record but does not drive the Miocene peak in mammalian species richness. 

Understanding the movement of fluids in the solid Earth system is crucial for answering a wide range of important questions in Earth science. Boron (B) is a perfect tracer for geofluids because of its high solubility and large isotopic fractionation that depends on both temperature and alkalinity. However, the high volatility of boron in acidic solutions at moderate temperatures presents a significant challenge for accurate measurements of the boron concentration and boron isotopic ratios for silicate rock samples. To circumvent this problem, most laboratories use low-temperature dissolution methods that involve concentrated hydrofluoric acid with or without mannitol. However, hydrofluoric acid is highly hazardous and the controlled temperature condition may be difficult to monitor. As a result, relatively few silicate samples have been analyzed for high precision B concentration and isotopic composition measurements, which hinders our understanding of the behavior of B in the solid earth system and the utility of this powerful tracer. Here we report B concentrations and isotopic compositions of the most commonly used geological reference standards dissolved through sodium peroxide sintering and purified using a rapid single-column exchange chromatographic procedure. This streamlined method effectively removes Na and Si from the sample matrix and generates accurate B concentration and isotopic data in as little as a day without the need for expensive lab equipment and reagents. Sintering is already routinely used to dissolve zircon-bearing silicate samples as it ensures complete dissolution. Besides the analysis of boron, other elemental and isotopic analyses can be performed using aliquots of the same dissolution, which greatly speeds up the chemical processing time and reduces uncertainties associated with sample heterogeneity. Using this method, large amounts of material can be processed for ion-exchange chromatography without the need of splitting each sample into separate beakers for dissolution as is often required for the HF + mannitol dissolution method. This new method can rapidly expand the available dataset of the boron concentration and boron isotopes of silicate materials which will certainly advance our understanding of many geologic problems involving fluids.