Annual Review of Earth and Planetary Sciences - Volume 50, 2022
Volume 50, 2022
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Civilization-Saving Science for the Twenty-First Century
Vol. 50 (2022), pp. 1–12More LessGeoscientists have generally been at the leading edge of predicting the challenges society faces from hazards both natural and anthropomorphic. As geoscientists, we have been less successful in devising the solutions to those problems to ensure a habitable planet for ourselves and future generations because often the solutions lie in creating novel partnerships with other researchers, including engineers, biologists, and social scientists. These sorts of transdisciplinary partnerships have been leading to radical advances in human health, under the banner of convergence science. Application of these principles of convergence science offers significant promise for addressing challenges such as climate change mitigation and adaptation, environmental health, protecting ecosystem services, and advancing sustainability science. To apply this approach rigorously, however, will involve a culture change in the geosciences in terms of how students are educated, how researchers are rewarded, and how projects are funded.
- ▪ Geoscientists need to work collaboratively with life, physical, and social scientists, as well as engineers, to solve the problems of our time.
- ▪ Universities need to address financial, procedural, educational, and cultural impediments to the conduct of convergence research.
- ▪ Adopting a solutions orientation to major environmental issues could help attract a more diverse geoscience workforce.
- ▪ Climate change mitigation would benefit from partnerships between geoscientists and social scientists to make the right behavior easy.
- ▪ The current course of Earth science education, research, and partnerships is inadequate to address sustainability.
- ▪ Ensuring environmental health requires collaboration between experts in health, environment, infrastructure, and economics.
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Application of Light Hydrocarbons in Natural Gas Geochemistry of Gas Fields in China
Vol. 50 (2022), pp. 13–53More LessLight hydrocarbons (LHs) are an important component of natural gas whose chemical and isotopic compositions play a vital role in identifying gas genetic type, thermal maturity, gas–gas correlation, gas–source correlation, migration direction and phase, and secondary alterations (such as evaporative fractionation, biodegradation, and thermochemical sulfate reduction) experienced by the gas pool. Through review of geochemical research into LHs over recent decades, and analysis of chemical and isotopic compositions of LHs of gases and condensates from more than 40 gas fields in China, we present an overview of the genetic mechanisms of LHs and the impacts of various factors on their geochemical compositions. The primary objectives of this review are to demonstrate the application of LH chemical and isotopic composition characteristics to gas geochemistry research and to assess the applicability and reliability of geochemical identification diagrams and parameters for determining gas genetic types, maturity, source, secondary alteration, and migration direction and phase.
- ▪ Three main genetic mechanisms are proposed for the formation of light hydrocarbons: thermal decomposition, catalytic decomposition of organic matter, and microbial action.
- ▪ Chemical and isotopic compositions of light hydrocarbons with different carbon numbers and/or structures can be used to identify the genetic types and maturity of natural gas.
- ▪ Content ratios and carbon isotopes of characteristic light hydrocarbons are good indicators for gas–gas and gas–source correlations.
- ▪ Secondary alterations (evaporative fractionation, biodegradation, thermochemical sulfate reduction) and migration of gas can be indicated by chemical and isotopic compositions of light hydrocarbons.
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Where Has All the Carbon Gone?
Vol. 50 (2022), pp. 55–78More LessCarbon is among the most abundant substances in the universe; although severely depleted on Earth, it is the primary structural element in biochemistry. Complex interactions between carbon and climate have stabilized the Earth system over geologic time. Since the modern instrumental CO2 record began in the 1950s, about half of fossil fuel emissions have been sequestered in the oceans and land ecosystems. Ocean uptake of fossil CO2 is governed by chemistry and circulation. Net land uptake is surprising because it implies a persistent worldwide excess of growth over decay. Land carbon sinks include (a) CO2 fertilization, (b) nitrogen fertilization, (c) forest regrowth following agricultural abandonment, and (d) boreal warming. Carbon sinks in both land and oceans are threatened by warming and are likely to weaken or even reverse as emissions fall with the potential for amplification of climate change due to the release of previously stored carbon. Fossil CO2 will persist for centuries and perhaps many millennia after emissions cease.
- ▪ About half the carbon from fossil fuel combustion is removed from the atmosphere by sink processes in the land and oceans, slowing the increase of CO2 and global warming. These sinks may weaken or even reverse as climate warms and emissions fall.
- ▪ The net land sink for CO2 requires that plants have been growing faster than they decay for many decades, causing carbon to build up in the biosphere over and above the carbon lost to deforestation, fire, and other disturbances.
- ▪ CO2 uptake by the oceans is slow because only the surface water is in chemical contact with the air. Cold water at depth is physically isolated by its density. Deep water mixes with the surface in about 1,000 years. The deep water does not know we are here yet!
- ▪ After fossil fuel emissions cease, much of the extra CO2 will remain in the atmosphere for many centuries or even millennia. The lifetime of excess CO2 depends on total historical emissions; 10% to 40% could last until the year 40,000 AD.
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Volcanic Outgassing of Volatile Trace Metals
Vol. 50 (2022), pp. 79–98More LessVolcanoes play a key role in the cycling of volatile metals (e.g., chalcophile elements such as Tl, Pb, and Cu and metalloids such as As, Te, and Se) on our planet. Volatile metals and metalloids are outgassed by active volcanoes, forming particulate volcanic plumes that deliver them in reactive form to the environment, where they may be nutrients (e.g., Cu and Zn) or pollutants (e.g., Hg, As, Pb). Volcanic outgassing rates of these elements compare to those associated with building ore deposits in the crust and to anthropogenic emission rates. There are distinct compositional differences between volcanic plumes in different tectonic settings, related to the enrichment of arc magmas in metals transported in slab fluids, metal speciation, and partitioning between silicate melt, vapor, and magmatic sulfide. Volcanic gases have compositions similar to those of quartz-hosted fluid inclusions found in mineralized granites, albeit with a lower density and salinity. Volatile volcanic metals are transported as soluble aerosols in volcanic plumes and may persist for hundreds of kilometers in the troposphere. Volcanic metal chloride aerosols in tropospheric volcanic plumes at high latitudes are recorded in ice cores.
- ▪ Volcanoes emit significant fluxes of volatile trace metals such as Cu, Tl, and Pb, as gases and particulates, to the surface environment.
- ▪ There is a distinct metal compositional fingerprint in volcanic and hydrothermal plumes at subduction and hotspot volcanoes and mid-ocean ridges, controlled by magma and fluid chemistry.
- ▪ Volcanic gases are the less saline equivalent of the fluids forming economic porphyry deposits of chalcophile metals (e.g., Cu) in the crust.
- ▪ The metals in tropospheric volcanic plumes may be rained out near the vent, but in dry environments they may persist for thousands of kilometers and be deposited in ice cores.
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Dynamos in the Inner Solar System
Vol. 50 (2022), pp. 99–122More LessDynamo magnetic fields are primarily generated by thermochemical convection of electrically conductive liquid metal within planetary cores. Convection can be sustained by secular cooling and may be bolstered by compositional buoyancy associated with core solidification. Additionally, mechanical stirring of core fluids and external perturbations by large impact events, tidal effects, and orbital precession can also contribute to sustaining dynamo fields. Convective dynamos cease when the core-mantle heat flux becomes subadiabatic or if specific crystallization regimes inhibit core fluid flows. Therefore, exploring the histories of magnetic fields across the Solar System provides a window into the thermal and chemical evolution of planetary interiors. Here we review how recent spacecraft-based studies of remanent crustal magnetism, paleomagnetic studies of rock samples, and planetary interior models have revealed the magnetic and evolutionary histories of Mercury, Earth, Mars, the Moon, and several planetesimals, as well as discuss avenues for future exploration and discovery.
- ▪ Paleomagnetism and remanent crustal magnetism studies elucidate the magnetic histories of rocky planetary bodies.
- ▪ Records of ancient dynamo fields have been obtained from 3 out of 4 terrestrial planets, the Moon, and several planetesimals.
- ▪ The geometries, intensities, and longevities of dynamo fields can provide information on core processes and planetary thermal evolution.
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Deciphering Temperature Seasonality in Earth's Ancient Oceans
Vol. 50 (2022), pp. 123–152More LessOngoing global warming due to anthropogenic climate change has long been recognized, yet uncertainties regarding how seasonal extremes will change in the future persist. Paleoseasonal proxy data from intervals when global climate differed from today can help constrain how and why the annual temperature cycle has varied through space and time. Records of past seasonal variation in marine temperatures are available in the oxygen isotope values of serially sampled accretionary organisms. The most useful data sets come from carefully designed and computationally robust studies that enable characterization of paleoseasonal parameters and seamless integration with mean annual temperature data sets and climate models. Seasonal data sharpen interpretations of—and quantify overlooked or unconstrained seasonal biases in—the more voluminous mean temperature data and aid in the evaluation of climate model performance. Methodologies to rigorously analyze seasonal data are now available, and the promise of paleoseasonal proxy data for the next generation of paleoclimate research is significant.
- ▪ The seasonal cycle defines climate and its constraints on biology, both today and in the deep past.
- ▪ Paleoseasonal data improve proxy-based estimates of mean annual temperature and validate Earth System Model simulations.
- ▪ Large, internally consistent data sets can reveal robust spatiotemporal climate patterns on the ancient Earth and how they change with pCO2.
- ▪ Computational tools enable rigorous numerical analysis of paleoseasonal data for comparison with other paleoclimate data and model output.
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Shear Properties of Earth's Inner Core
Vol. 50 (2022), pp. 153–181More LessUnderstanding how Earth's inner core (IC) develops and evolves, including fine details of its structure and energy exchange across the boundary with the liquid outer core, helps us constrain its age, relationship with the planetary differentiation, and other significant global events throughout Earth's history, as well as the changing magnetic field. Since its discovery in 1936 and the solidity hypothesis in 1940, Earth's IC has never ceased to inspire geoscientists. However, while there are many seismological observations of compressional waves and normal modes sensitive to the IC's compressional and shear structure, the shear waves that provide direct evidence for the IC's solidity have remained elusive and have been reported in only a few publications. Further advances in the emerging correlation-wavefield paradigm, which explores waveform similarities, may hold the keys to refined measurements of all IC shear properties, informing dynamical models and strengthening interpretations of the IC's anisotropic structure and viscosity.
- ▪ What are the shear properties of the IC, such as the shear-wave speed, shear modulus, shear attenuation, and shear-wave anisotropy?
- ▪ Can the shear properties be measured seismologically and confirmed experimentally?
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Seismic Advances in Process Geomorphology
Vol. 50 (2022), pp. 183–204More LessOne of the pillars of geomorphology is the study of geomorphic processes and their drivers, dynamics, and impacts. Like all activity that transfers energy to Earth's surface, a wide range of geomorphic process types create seismic waves that can be measured with standard seismic instruments. Seismic signals provide continuous high-resolution coverage with a spatial footprint that can vary from local to global, and in recent years, efforts to exploit these signals for information about surface processes have increased dramatically, coalescing into the emerging field of environmental seismology. The application of seismic methods has the potential to drive advances in our understanding of the occurrence, timing, and triggering of geomorphic events, the dynamics of geomorphic processes, fluvial bedload transport, and integrative geomorphic system monitoring. As new seismic applications move from development to proof of concept to routine application, integration between geomorphologists and seismologists is key for continued progress.
- ▪ Geomorphic activity on Earth's surface produces seismic signals that can be measured with standard seismic instruments.
- ▪ Seismic methods are driving advances in our understanding of the occurrence, triggering, and internal dynamics of a range of geomorphic processes.
- ▪ Dedicated seismic-based observatories offer the potential to comprehensively characterize geomorphic activity and its impacts across a landscape.
- ▪ Collaboration between seismologists and geomorphologists is fostering the development of new applications, models, and analysis techniques for geomorphic seismology.
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Molar-Tooth Structure as a Window into the Deposition and Diagenesis of Precambrian Carbonate
Vol. 50 (2022), pp. 205–230More LessMolar-tooth structure (MTS) is an unusual carbonate fabric that is composed of variously shaped cracks and voids filled with calcite microspar. Despite a century of study, MTS remains enigmatic because it juxtaposes void formation within a cohesive yet unlithified substrate with the penecontemporaneous precipitation and lithification of void-filling carbonate microspar. MTS is broadly restricted to shallow marine carbonate strata of the Mesoproterozoic and Neoproterozoic, suggesting a fundamental link between the formation of MTS and the biogeochemical evolution of marine environments. Despite uncertainties in the origin of MTS, molar-tooth (MT) microspar remains a popular target for geochemical analysis and the reconstruction of Precambrian marine chemistry. Here we review models for the formation of MTS and show how detailed petrographic analysis of MT microspar permits identification of a complex process of precipitation and diagenesis that must be considered when the microspar phase is used as a geochemical proxy.
- ▪ Molar-tooth fabric is an enigmatic structure in Precambrian sedimentary rocks that is composed of variously shaped cracks and voids filled with carbonate microspar.
- ▪ Time restriction of this fabric suggests a link between this unusual structure and the biogeochemical evolution of marine environments.
- ▪ Petrographic analysis of molar-tooth fabric provides insight into fundamental processes of crystallization.
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Determining the State of Activity of Transcrustal Magmatic Systems and Their Volcanoes
G. Giordano, and L. CaricchiVol. 50 (2022), pp. 231–259More LessPolygenetic volcanoes and calderas produce eruptions of a wide variety of magnitudes, chemistries, and recurrence times. Understanding the interplay between long- and short-term and deep and shallow processes associated with accumulation and transfer of eruptible magma is essential for assessing the potential for future eruptions to occur and estimating their magnitude, which remains one of the foremost challenges in the Earth sciences. We review literature and use existing data for emblematic volcanic systems to identify the essential data sets required to define the state of activity of volcanoes and their plumbing systems. We explore global eruptive records in combination with heat flux and other geological and geophysical data to determine the evolutionary stage of plumbing systems. We define a Volcanic Activity Index applicable to any volcano that provides an estimate of the potential of a system to erupt in the future, which is especially important for long-quiescent volcanoes.
- ▪ Magmatic plumbing systems that feed volcanic activity extend across Earth's crust and are long-lived at depth and ephemeral in their shallowest portions.
- ▪ We revise and update the definitions of active, quiescent, and extinct volcanoes based on physical proxies for the architecture, longevity, amount, and distribution of eruptible magma in the crust.
- ▪ We propose a Volcanic Activity Index, which provides a relative measure of the state of activity of a volcano with respect to all other volcanoes in the world.
- ▪ New imaging and monitoring strategies are required to improve our ability to detect lower and middle crust magmatic processes and forecast eruptions and their potential size.
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Carbonatites: Classification, Sources, Evolution, and Emplacement
Vol. 50 (2022), pp. 261–293More LessCarbonatites are igneous rocks formed in the crust by fractional crystallization of carbonate-rich parental melts that are mostly mantle derived. They dominantly consist of carbonate minerals such as calcite, dolomite, and ankerite, as well as minor phosphates, oxides, and silicates. They are emplaced in continental intraplate settings such as cratonic interiors and margins, as well as rift zones, and rarely on oceanic islands. Carbonatites are cumulate rocks, which are formed by physical separation and accumulation of crystals that crystallize from a melt, and their parental melts form by either (a) direct partial melting of carbonate-bearing, metasomatized, lithospheric mantle producing alkali-bearing calciodolomitic melts or (b) silicate-carbonate liquid immiscibility following fractional crystallization of carbonate-bearing, silica-undersaturated magmas such as nephelinites, melilitites, or lamprophyres. Their emplacement into the crust is usually accompanied by fenitization, alkali metasomatism of wallrock caused by fluids expelled from the crystallizing carbonatite.Carbonatites are major hosts of deposits of the rare earth elements and niobium, and the vast majority of the global production of these commodities is from carbonatites.
- ▪ Carbonatites are igneous rocks formed from carbonate-rich magmas, which ultimately formed in Earth's upper mantle.
- ▪ Carbonatites are associated with economic deposits of metals such as the rare earth elements and niobium, which are essential in high-tech applications.
- ▪ There are more than 600 carbonatites in the geological record but only one currently active carbonatite volcano, Oldoinyo Lengai in Tanzania.
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Tectonics of the Colorado Plateau and Its Margins
Vol. 50 (2022), pp. 295–322More LessThe Cenozoic Colorado Plateau physiographic province overlies multiple Precambrian provinces. Its ∼2-km elevation rim surrounds an ∼1.6-km elevation core that is underlain by thicker crust and lithospheric mantle, with a sharp structural transition ∼100 km concentrically inboard of the physiographic boundary on all but its northeastern margin. The region was uplifted in three episodes: ∼70–50 Ma uplift above sea level driven by flat-slab subduction; ∼38–23 Ma uplift associated with voluminous regional magmatism and slab removal, and less than 20 Ma uplift associated with inboard propagation of basaltic magmatism that tracked convective erosion of the lithospheric core. Neogene uplift helped integrate the Colorado River from the Rockies at 11 Ma to the Gulf of California by ∼5 Ma. The sharp rim-to-core transition defined by geological and geophysical data sets suggests a young transient plateau that is uplifting as it shrinks to merge with surrounding regions of postorogenic extension.
- ▪ The Colorado Plateau's iconic landscapes were shaped during its 70-million-year, still-enigmatic, tectonic evolution characterized by uplift and erosion.
- ▪ Uplift of the Colorado Plateau from sea level took place in three episodes, the youngest of which has been ongoing for the past 20 million years.
- ▪ Tectonism across the Colorado Plateau's nearest plate margin (the base of the plate!) is driving uplift and volcanism and enhancing its rugged landscapes.
- ▪ The bowl-shaped Colorado Plateau province is defined by ongoing uplift and an inboard sweep of magmatism around its margins.
- ▪ The keel of the Colorado Plateau is being thinned as the North American plate moves southwest through the underlying asthenosphere.
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Fracture, Friction, and Permeability of Ice
Vol. 50 (2022), pp. 323–343More LessWater ice Ih exhibits brittle behavior when rapidly loaded. Under tension, it fails via crack nucleation and propagation. Compressive failure is more complicated. Under low confinement, cracks slide and interact to form a frictional (Coulombic) fault. Under high confinement, frictional sliding is suppressed and adiabatic heating through crystallographic slip leads to the formation of a plastic fault. The coefficient of static friction increases with time under load, owing to creep of asperities in contact. The coefficient of kinetic (dynamic) friction, set by the ratio of asperity shear strength to hardness, increases with velocity at lower speeds and decreases at higher speeds as contacts melt through frictional heating. Microcracks, upon reaching a critical number density (which near the ductile-to-brittle transition is nearly constant above a certain strain rate), form a pathway for percolation. Additional work is needed on the effects of porosity and crack healing.
- ▪ An understanding of brittle failure is essential to better predict the integrity of the Arctic and Antarctic sea ice covers and the tectonic evolution of the icy crusts of Enceladus, Europa, and other extraterrestrial satellites.
- ▪ Fundamental to the brittle failure of ice is the initiation and propagation of microcracks, frictional sliding across crack faces, and localization of strain through both crack interaction and adiabatic heating.
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Geodetic and Geological Deformation of the Island Arc in Northeast Japan Revealed by the 2011 Tohoku Earthquake
Vol. 50 (2022), pp. 345–368More LessNortheast Japan is a typical island arc related to the Pacific plate subduction. The 2011 Mw 9.0 Tohoku-oki earthquake provided a unique opportunity to analyze crustal deformation with different boundary conditions, similar to a gigantic rock deformation experiment. We review findings obtained through various observations and data analyses in Northeast Japan, focusing on the crustal deformation in different timescales. The occurrence of the M9 earthquake solved the ongoing paradox that the geodetic strain rate is an order of magnitude larger than the geologic estimate, showing that the centennial geodetic observation had mainly captured the elastic strain accumulation. Along the localized contraction zone along the Japan Sea coast, a comparison of postseismic and interseismic deformation patterns revealed a significant contribution of inelastic deformation, which plays an essential role in long-term deformation. Along the Pacific coast, rapid interseismic subsidence and unexpected coseismic subsidence were followed by a rapid postseismic uplift, indicating that viscous relaxation in the mantle is of essential importance. These findings advance our understanding of plate interactions and the tectonic evolution of the island arc.
- ▪ The 2011 Tohoku-oki earthquake provided the most complete crustal deformation data set ever for interseismic, coseismic, and postseismic periods.
- ▪ The discrepancy between the geologic and geodetic deformation rates in Northeast Japan is attributed to an elastic strain due to interplate locking.
- ▪ A significant contribution of inelastic deformation in the island arc crust is identified through a comparison of interseismic and postseismic deformations.
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Biomarker Approaches for Reconstructing Terrestrial Environmental Change
Vol. 50 (2022), pp. 369–394More LessThe response of the terrestrial biosphere to warming remains one of the most poorly understood and quantified aspects of the climate system. One way to test the behavior of the Earth system in warm climate states is to examine the geological record. The abundance, distribution, and/or isotopic composition of source-specific organic molecules (biomarkers) have been used to reconstruct terrestrial paleoenvironmental change over a range of geological timescales. Here, we review new or recently improved biomarker approaches for reconstructing (a) physical climate variables (land temperature, rainfall), (b) ecosystem state variables (vegetation, fire regime), and (c) biogeochemical variables (soil residence time, methane cycling). This review encompasses a range of key compound classes (e.g., lipids, lignin, and carbohydrates). In each section, we explore the concept behind key biomarker approaches and discuss their successesas paleoenvironmental indicators. We emphasize that analyzing several biomarkers in tandem can provide unique insights into the Earth system.
- ▪ Biomarkers can be used to reconstruct terrestrial environmental change over a range of geological timescales.
- ▪ A multi-proxy biomarker approach provides novel insights into climate and the environment.
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The Isotopic Ecology of the Mammoth Steppe
Vol. 50 (2022), pp. 395–418More LessThe Mammoth Steppe was the dominant terrestrial biome of the Northern Hemisphere during the late Pleistocene. It encompassed a nonanalog community of animals living in a cold and treeless steppe-tundra landscape. The high diversity of species, including megafauna, could be supported by a productive environment. The carbon-13 and nitrogen-15 abundances in bone collagen confirmed that the coexistence of the large herbivores was facilitated by a pronounced dietary niche partitioning, with some species relatively flexible in the exploitation of browse and graze, while others were more specialized. The isotopic abundances of carbon and nitrogen in carnivores confirm a dietary partitioning, probably based on the size of prey, with an increasingly generalist behavior emerging after the Last Glacial Maximum with notable exceptions. Isotopic investigation reveals dynamic processes of ecological displacement and replacement, shedding new light on the potential niche spectrum of extant species that are now present as relic populations.
- ▪ The Mammoth Steppe is an extinct nonanalog ecosystem with high productivity and biodiversity despite the cold and dry conditions of the Last Glacial Period.
- ▪ Stable isotopes reveal that niche partitioning among herbivores and carnivores is a dominant trait of the Mammoth Steppe.
- ▪ Switches in preferred prey and ecological replacement are observed among carnivores over time, with the few highly specialized predators going extinct.
- ▪ Warmer and more humid conditions preceding the Holocene impacted large herbivores in most regions of the Mammoth Steppe, driving some of the largest ones to extinction.
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Macrostratigraphy: Insights into Cyclic and Secular Evolution of the Earth-Life System
Vol. 50 (2022), pp. 419–449More LessRocks in Earth's crust are formed, modified, and destroyed in response to myriad interactions between the solid Earth (tectonics, geodynamics), the fluid Earth (ocean-atmosphere, cryosphere), and the living Earth (evolution, biochemistry). As such, the geological record is an integrator of geological, biological, and climatological processes and their histories. Here we review contrasting perceptions of the processes that govern the formation and destruction of the geological record, beginning with the relationship between macroevolutionary patterns in the fossil and sedimentary rock records and culminating with contrasting models of rock cycling. Using the approach of macrostratigraphy, we present an integrated summary of the quantity-age properties of rocks in continental and oceanic crust. The predominant process signal in the rock quantity-age distribution in continental crust is one of episodic growth, whereas in oceanic crust it is one of continual destruction. Relatively abrupt shifts in the dominant locus of sediment deposition, from fast-cycling oceanic crust to long-term continental reservoirs, and attendant expansions and contractions in the area of crust that is emergent, are correlated in timing and magnitude with shifts in the concentration of oxygen in the atmosphere and major macroevolutionary transitions in the biosphere. The most recent of possibly two such first-ordertransitions occurred at the start of the Phanerozoic and is marked by a prominent preserved geomorphic surface known as the Great Unconformity.
- ▪ Macrostratigraphy uses the bulk characteristics of the rock record to probe the evolution of the Earth system.
- ▪ Quantifying the creation and destruction of rock units can illuminate the long-term evolution of continents and the life that inhabits them.
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Reconstructing the Environmental Context of Human Origins in Eastern Africa Through Scientific Drilling
Andrew S. Cohen, Christopher J. Campisano, J. Ramón Arrowsmith, Asfawossen Asrat, Catherine C. Beck, Anna K. Behrensmeyer, Alan L. Deino, Craig S. Feibel, Verena Foerster, John D. Kingston, Henry F. Lamb, Tim K. Lowenstein, Rachel L. Lupien, Veronica Muiruri, Daniel O. Olago, R. Bernhart Owen, Richard Potts, James M. Russell, Frank Schaebitz, Jeffery R. Stone, Martin H. Trauth, and Chad L. YostVol. 50 (2022), pp. 451–476More LessPaleoanthropologists have long speculated about the role of environmental change in shaping human evolution in Africa. In recent years, drill cores of late Neogene lacustrine sedimentary rocks have yielded valuable high-resolution records of climatic and ecosystem change. Eastern African Rift sediments (primarily lake beds) provide an extraordinary range of data in close proximity to important fossil hominin and archaeological sites, allowing critical study of hypotheses that connect environmental history and hominin evolution. We review recent drill-core studies spanning the Plio–Pleistocene boundary (an interval of hominin diversification, including the earliest members of our genus Homo and the oldest stone tools), and the Mid–Upper Pleistocene (spanning the origin of Homo sapiens in Africa and our early technological and dispersal history). Proposed drilling of Africa's oldest lakes promises to extend such records back to the late Miocene.
- ▪ High-resolution paleoenvironmental records are critical for understanding external drivers of human evolution.
- ▪ African lake basin drill cores play a critical role in enhancing hominin paleoenvironmental records given their continuity and proximity to key paleoanthropological sites.
- ▪ The oldest African lakes have the potential to reveal a comprehensive paleoenvironmental context for the entire late Neogene history of hominin evolution.
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Toward Understanding Deccan Volcanism
Vol. 50 (2022), pp. 477–506More LessLarge igneous provinces (LIPs) represent some of the greatest volcanic events in Earth history with significant impacts on ecosystems, including mass extinctions. However, some fundamental questions related to the eruption rate, eruption style, and vent locations for LIP lava flows remain unanswered. In this review, we use the Cretaceous–Paleogene Deccan Traps as an archetype to address these questions because they are one of the best-preserved large continental flood basalt provinces. We describe the volcanological features of the Deccan flows and the potential temporal and regional variations as well as the spatial characteristics of potential feeder dikes. Along with estimates of mean long-term eruption rates for individual Deccan lavas from paleomagnetism and Hg proxy records of ∼50–250 km3/year (erupting for tens to hundreds of years), the Deccan volcanic characteristics suggest a unified conceptual model for eruption of voluminous (>1,000 km3) LIP lavas with large spatial extent (>40,000 km2). We conclude by highlighting a few key open questions and challenges that can help improve our understanding of how the Deccan flows, as well as LIP flows in general, erupted and the mechanisms by which the lavas may have flowed over distances up to 1,000 km.
- ▪ The Deccan Traps are an archetype for addressing fundamental volcanological questions related to eruption rate, eruption style, and vent locations for large igneous province lava flows.
- ▪ Deccan subprovinces likely evolved as separate volcanic systems; thus, long-distance/interprovince flow correlations must be carefully assessed.
- ▪ The earliest eruptions came through the Narmada-Tapi rift zone followed by the establishment of a separate magmatic plumbing system by mantle plume–associated magmas.
- ▪ Typical Deccan eruption rates were ∼50–250 km3/year of lava. Individual eruptions lasted for a few hundred to 1,000 years and were separated by hiatuses of 3,000–6,000 years.
- ▪ The conspicuous absence of dikes in the Central Deccan region strongly implies long-distance surface transport of lavas in the form of flows hundreds of kilometers long.
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Previous Volumes
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Volume 52 (2024)
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Volume 51 (2023)
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Volume 50 (2022)
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Volume 49 (2021)
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Volume 48 (2020)
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Volume 47 (2019)
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Volume 46 (2018)
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Volume 45 (2017)
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Volume 44 (2016)
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Volume 43 (2015)
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Volume 42 (2014)
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Volume 41 (2013)
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Volume 40 (2012)
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Volume 39 (2011)
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Volume 38 (2010)
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Volume 37 (2009)
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Volume 36 (2008)
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Volume 35 (2007)
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Volume 34 (2006)
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Volume 33 (2005)
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Volume 32 (2004)
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Volume 31 (2003)
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Volume 30 (2002)
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Volume 29 (2001)
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Volume 28 (2000)
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Volume 27 (1999)
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Volume 26 (1998)
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Volume 25 (1997)
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Volume 24 (1996)
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Volume 23 (1995)
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Volume 22 (1994)
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Volume 21 (1993)
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Volume 20 (1992)
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Volume 19 (1991)
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Volume 18 (1990)
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Volume 17 (1989)
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Volume 16 (1988)
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Volume 15 (1987)
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Volume 14 (1986)
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Volume 13 (1985)
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Volume 12 (1984)
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Volume 11 (1983)
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Volume 10 (1982)
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Volume 9 (1981)
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Volume 8 (1980)
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Volume 7 (1979)
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Volume 6 (1978)
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Volume 5 (1977)
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Volume 4 (1976)
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Volume 3 (1975)
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Volume 2 (1974)
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Volume 1 (1973)
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Volume 0 (1932)