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Cyclostratigraphic studies of sedimentary rocks traditionally sample assuming that one sample per sedimentary horizon is sufficient. But is one sample enough? This is important to address because if two or more measurements per horizon improve data quality, then sampling schemes should strike a balance between sampling resolution (stratigraphically) and bedding variation (laterally). This study aims to address this fundamental question by statistically comparing the results from data sets based on individual versus multiple measurements per stratigraphic horizon. Using magnetic susceptibility as our proxy, which can be readily measured in situ for such a study, we evaluate both field‐based (KT‐10R) and laboratory‐based (MFK2‐FA Kappabridge) susceptibility data and compare their results. For the Guanmenshan Formation, a Paleoproterozoic (ca. 2.16 Ga) platform carbonate of North China craton, we find broad agreement between the two means of measurement. But the KT‐10R field meter, with multiple measurements per bed, shows increased statistical significance in identifying Milankovitch cycles. This dual comparison between lab‐ and field‐based methods and single versus multiple measurements per bed demonstrates that measuring one sample per bed reduces accuracy in determining the true average proxy value of a bed. Thus, averaging the natural variation in composition along a stratigraphic layer (spatial resolution)—typically ignored when only one sample is taken—may be as important as the precision of measurement or the sampling interval. Our results suggest that n = 2 samples/measurements per bed are better than just n = 1, and results are best for n = 3 per layer.

The geologic record exhibits periods of active and quiescent geologic processes, including magmatism, metamorphism and mineralization. This apparent episodicity has been ascribed either to bias in the geologic record or fundamental changes in geodynamic processes. An appraisal of the global geologic record from about 2.3 to 2.2 billion years ago demonstrates a Palaeoproterozoic tectono-magmatic lull. During this lull, global-scale continental magmatism (plume and arc magmatism) and orogenic activity decreased. There was also a lack of passive margin sedimentation and relative plate motions were subdued. A global compilation of mafic igneous rocks demonstrates that this episode of magmatic quiescence was terminated about 2.2 billion years ago by a flare-up of juvenile magmatism. This post-lull magmatic flare-up is distinct from earlier such events, in that the material extracted from the mantle during the flare-up yielded significant amounts of continental material that amalgamated to form Nuna — Earth’s first hemispheric supercontinent. We posit that the juvenile magmatic flare-up was caused by the release of significant thermal energy that had accumulated over some time. This flux of mantle-derived energy could have provided a mechanism for dramatic growth of continental crust, as well as the increase in relative plate motions required to complete the transition to modern plate tectonics and the supercontinent cycle. These events may also be linked to Palaeoproterozoic atmospheric oxygenation and equilibration of the carbon cycle.

Earth’s earliest continental crust is dominated by tonalite–trondhjemite–granodiorite (TTG) suites, making these rocks key to unlocking the global geodynamic regime operating during the Archaean (4.0–2.5 billion years ago [Ga]). The tectonic setting of TTG magmatism is controversial, with hypotheses arguing both for and against subduction. Here we conduct petrological modeling over a range of pressure–temperature conditions relevant to the Archaean geothermal gradient. Using an average enriched Archaean basaltic source composition, we predict Ba concentrations in TTG suites, which is difficult to increase after magma generated in the source. The results indicate only low geothermal gradients corresponding to hot subduction zones produce Ba-rich TTG, thus Ba represents a proxy for the onset of subduction. We then identify statistically significant increases in the Ba contents of TTG suites worldwide as recording the diachronous onset of subduction from regional at 4 Ga to globally complete sometime after 2.7 Ga. Only subduction zone can produce Ba-rich TTG, representing a proxy for the onset of subduction. Statistical increases in Ba contents of Archaean TTGs reveal the diachronous onset of subduction from regional at 4 Ga to globally complete after 2.7 Ga

The left‐lateral Altyn Tagh Fault (ATF) system is the northern boundary of the Tibetan Plateau resulted from the India–Eurasia continental collision. How intracontinental deformation across the central ATF responds to the distal collision remains elusive, primarily due to unclear crustal structure. We obtained detailed crustal structure across the central ATF using receiver functions recorded by ∼NW–SE oriented linear dense array. The images reveal the Tarim lower crust is underthrusting beneath the Tibetan Plateau and reaches to a maximum depth of ∼75 km and undergoing partial eclogitization. The two south‐dipping interfaces imaged beneath the Altyn Tagh Range (ATR) represent the thrusting Northern Altyn Fault and its branch fault. Oblique convergent forces extruded upper crustal materials along the thrust faults, creating the pop‐up structure of ATR, supported by low Vp/Vs ratios. Our balanced cross‐section for the Moho suggests intracontinental deformation in the ATR has accelerated since the late Miocene. Plain Language Summary The Altyn Tagh Fault (ATF), serving as the northern boundary of the Tibetan Plateau, demarcates the Tarim Basin from the Qaidam Basin. Understanding how intracontinental deformation across the boundary region would better inform the uplift and expansion of the plateau. This study reveals the fine crustal structure by analyzing seismic data from a ∼NW–SE oriented linear dense array across the central ATF. Combined with fault slip rates, we propose that the Tarim lower crust is underthrusting beneath the Tibetan Plateau, leading to the extrusion of upper crustal materials and the rapid uplift of the Altyn Tagh Range since the late Miocene, which provides insight into the lateral growth of the plateau. Key Points Detailed crustal structure beneath the central Altyn Tagh Fault was imaged by receiver functions of a dense 2‐D seismic array The Tarim lower crust is underthrusting to ∼75 km depth beneath the Tibetan Plateau The Altyn Tagh range was uplifted rapidly since late Miocene through the thickening of the upper crust

The Ordovician–Silurian transition experienced severe, but enigmatic, glaciation, as well as a paradoxical combination of mass extinction and species origination. Here we report a large and fast true polar wander (TPW) event that occurred 450–440 million years ago based on palaeomagnetic data from South China and compiled reliable palaeopoles from all major continents. Collectively, a ~50˚ wholesale rotation with maximum continental speeds of ~55 cm yr −1 is demonstrated. Multiple isolated continents moving rapidly, synchronously, and unidirectionally is less consistent with and plausible for relative plate motions than TPW. Palaeogeographic reconstructions constrained by TPW controlling for palaeolongitude explain the timing and migration of glacial centers across Gondwana, as well as the protracted end-Ordovician mass extinction. The global quadrature pattern of latitude change during TPW further explains why the extinction was accompanied by elevated levels of origination as some continents migrated into or remained in the amenable tropics. Palaeomagnetic data from South China and compiled reliable palaeopoles from 4 other continents reveals a ~50˚ true polar wander (TPW) event occurring 450–440 million years ago. Sweeping Gondwana across the South Pole, this TPW event induced the Ordovician glaciation and mass extinction.

The geodynamic processes that formed Earth’s earliest continents are intensely debated. Particularly, the transformation from ancient crustal nuclei into mature Archaean cratons is unclear, primarily owing to the paucity of well-preserved Eoarchaean–Palaeoarchaean ‘protocrust’. Here, we report a newly identified Palaeoarchaean continental fragment—the Baishanhu nucleus—in northeastern North China Craton. U–Pb geochronology shows that this nucleus preserves five major magmatic events during 3.6–2.5 Ga. Geochemistry and zircon Lu–Hf isotopes reveal ancient 4.2–3.8 Ga mantle extraction ages, as well as later intraplate crustal reworking. Crustal architecture and zircon Hf–O isotopes indicate that proto-North China first formed in a stagnant/squishy lid geodynamic regime characterised by plume-related magmatic underplating. Such cratonic growth and maturation were prerequisites for the emergence of plate tectonics. Finally, these data suggest that North China was part of the Sclavia supercraton and that the Archaean onset of subduction occurred asynchronously worldwide. Multi-stage Archaean magmatic underplating events are reported from the Baishan continental nucleus, North China Craton. Such underplating processes occurred in a stagnant lid geodynamic regime and led to the growth and maturation of the craton.

Earth's core should contain light elements to account for the density deficit relative to pure iron as inferred from seismic observations. Of particular interest is hydrogen, as planetary accretion models predict the delivery of water possibly sequestered in the core. In this study, we investigate the partitioning of hydrogen across the inner‐core boundary using extensive atomistic simulations with machine learning potentials. While showing the tendency of hydrogen to dominantly remain in the liquid phase during inner core solidification, we find that the presence of oxygen would drive more hydrogen into the inner core, where 7 mol% oxygen even reverses the partitioning of hydrogen. By considering such mutual influences of partitioning among light elements in the core, we propose that the inner core can be an important reservoir of primordial hydrogen along with its growth. Plain Language Summary It is well known that Earth's core is composed of iron and nickel along with appreciable light elements such as silicon, oxygen, sulfur, carbon, and hydrogen. Among these candidates, hydrogen stands out given recent evidence for primordial H2O/H in Earth's core. In this study, by using extensive first principles simulations, we systematically investigate the thermodynamics of Fe–H–O systems. The partition coefficient of hydrogen across the inner‐core boundary has been quantified for different amounts of oxygen. It is found that the presence of oxygen in the outer core tends to drive more hydrogen into the inner core and even reverse the partitioning of hydrogen. This study thus demonstrates the importance of accounting for the mutual influences among light elements for unraveling the still enigmatic composition of Earth's core as well as how inner core solidification over time may have caused compositional changes that affect the evolution of the core, its seismic properties, and its ability to power the magnetic field. Key Points Oxygen exhibits a strong influence on hydrogen partitioning, driving more hydrogen into the solid inner core Partitioning of hydrogen across the ICB can be reversed from liquid to solid with 7 mol% oxygen in the core Mutual influences of partitioning among light elements are essential for understanding the composition and evolution of Earth's core

The history of mare volcanism critically informs the thermal evolution of the Moon. However, young volcanic eruptions are poorly constrained by remote observations and limited samples, hindering an understanding of mare eruption flux over time. The Chang’e-5 mission returned the youngest lunar basalts thus far, offering a window into the Moon’s late-stage evolution. Here, we investigate the mineralogy and geochemistry of 42 olivine and pyroxene crystals from the Chang’e-5 basalts. We find that almost all of them are normally zoned, suggesting limited magma recharge or shallow-level assimilation. Most olivine grains record a short timescale of cooling. Thermal modeling used to estimate the thickness and volume of the volcanism sampled by Chang’e-5 reveals enhanced magmatic flux ~2 billion years ago, suggesting that while overall lunar volcanic activity may decrease over time, episodic eruptions at the final stage could exhibit above average eruptive fluxes, thus revising models of lunar thermal evolution. This work estimates the eruption volume of the young Chang’e-5 lunar samples using diffusion chronology and thermodynamic simulations, and finds that there was an increase in volcanic eruption flux about 2.0 billion years ago.

The African large low shearwave-velocity province (LLSVP) advected plumes manifest as large igneous provinces (LIPs) during Pangea breakup. The existence of such basal mantle structures during earlier supercontinents is unknown. Here we analyze samples from China and Brazil to demonstrate with literature data a series of seven LIPs of supercontinent Rodinia from 940–720 million years ago. Multi-proxy reconstruction results in a coherent ring of LIPs comparable with the size of Rodinia that resembles the product of an ancient LLSVP whose edges advected LIP-producing plumes. Oceanic lithosphere recycling following supercontinental assembly is evident in Nd isotopes as evolving LIP-sources. There is a same secular variational pattern of LIP sources with a replenished depleted component advected by plumes as well as a similar manner yet contrasting paleogeographic configurations corresponding to supercontinental breakup between Rodinian and Pangean LLSVPs. This evolving pattern of LLSVPs suggests their partial regeneration (replenishment and migration) between supercontinents. Reconstruction of seven sequential Rodinia large igneous provinces defines a basal mantle structure similar but different from that of Pangea, which implies partial regeneration of large low shearwave-velocity provinces through supercontinent cycles.

Large low shear-wave velocity provinces (LLSVPs) in the lowermost mantle are the largest geological structures on Earth, but their origin and age remain highly enigmatic. Geological constraints suggest the stability of the LLSVPs since at least 200 million years ago. Here, we conduct numerical modeling of mantle convection with plate-like behavior that yields a Pacific-like girdle of mantle downwelling which successfully forms two antipodal basal mantle structures similar to the LLSVPs. Our parameterized results optimized to reflect LLSVP features exhibit velocities for the basal mantle structures that are ~ 4 times slower than the ambient mantle if they are thermochemical, while the velocity is similar to the ambient mantle if purely thermal. The sluggish motion of the thermochemical basal mantle structures in our models permits the notion that geological data from hundreds of millions of years ago are related to modern LLSVPs as they are essentially stationary over such time scales. Geodynamic modeling shows that large thermochemical basal mantle structures, known as LLSVPs, move much slower than the surrounding mantle, supporting their long-term stability comparable to the geological time scale of several hundred million years.