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  • Deep and extensive meltwater system beneath the former Eurasian Ice Sheet in the Kara Sea
    Geology (IF 5.006) Pub Date : 2020-02-01
    Aleksandr Montelli, Julian A. Dowdeswell, Anastasiya Pirogova, Yana Terekhina, Mikhail Tokarev, Nikita Rybin, Anton Martyn, Vladislav Khoshtariya

    The Eurasian ice sheet extended across the Barents and Kara Seas during the late Quaternary, yet evidence on past ice dynamics and thermal structure across its huge eastern periphery remains largely unknown. Here we use three-dimensional seismic data sets covering ∼4500 km2 of the Kara Sea west of Yamal Peninsula, Siberia (71°–73°N), to identify, for the first time in the Russian Arctic seas, several

    更新日期:2020-04-23
  • Geochemical evidence for an orogenic plateau in the southern U.S. and northern Mexican Cordillera during the Laramide orogeny
    Geology (IF 5.006) Pub Date : 2020-02-01
    James B. Chapman, Roy Greig, Gordon B. Haxel

    Previous studies of the central United States Cordillera have indicated that a high-elevation orogenic plateau, the Nevadaplano, was present in Late Cretaceous to early Paleogene time. The southern United States Cordillera and northern Mexican Cordillera share a similar geologic history and many of the same tectonic features (e.g., metamorphic core complexes) as the central United States Cordillera

    更新日期:2020-04-23
  • Metasomatized lithospheric mantle for Mesozoic giant gold deposits in the North China craton
    Geology (IF 5.006) Pub Date : 2020-02-01
    Zaicong Wang, Huai Cheng, Keqing Zong, Xianlei Geng, Yongsheng Liu, Jinhui Yang, Fuyuan Wu, Harry Becker, Stephen Foley, Christina Yan Wang

    The origin of giant lode gold deposits of Mesozoic age in the North China craton (NCC) is enigmatic because high-grade metamorphic ancient crust would be highly depleted in gold. Instead, lithospheric mantle beneath the crust is the likely source of the gold, which may have been anomalously enriched by metasomatic processes. However, the role of gold enrichment and metasomatism in the lithospheric

    更新日期:2020-04-23
  • Coupled supercontinent–mantle plume events evidenced by oceanic plume record
    Geology (IF 5.006) Pub Date : 2020-02-01
    Luc S. Doucet, Zheng-Xiang Li, Richard E. Ernst, Uwe Kirscher, Hamed Gamal El Dien, Ross N. Mitchell

    The most dominant features in the present-day lower mantle are the two antipodal African and Pacific large low-shear-velocity provinces (LLSVPs). How and when these two structures formed, and whether they are fixed and long lived through Earth history or dynamic and linked to the supercontinent cycles, remain first-order geodynamic questions. Hotspots and large igneous provinces (LIPs) are mostly generated

    更新日期:2020-04-23
  • Regional and global signals in seawater δ 18 O records across the mid-Pleistocene transition
    Geology (IF 5.006) Pub Date : 2020-02-01
    Heather L. Ford, Maureen E. Raymo

    High-resolution seawater δ18O records, derived from coupled Mg/Ca and benthic δ18O analyses, can be used to evaluate how global ice volume changed during the mid-Pleistocene transition (MPT, ca. 1250–600 ka). However, such seawater δ18O records are also influenced by regional hydrographic signals (i.e., salinity) and changes in deep-ocean circulation across the MPT, making it difficult to isolate the

    更新日期:2020-04-23
  • Carbonate collapse and the late Paleozoic ice age marine biodiversity crisis
    Geology (IF 5.006) Pub Date : 2020-02-01
    Diego Balseiro, Matthew G. Powell

    The late Paleozoic ice age (LPIA) was characterized by persistently low diversity of marine invertebrates following a second-order mass extinction. Here, we used a data set of North American (paleotropical) fossil occurrences of brachiopod, bivalve, and coral genera from the Paleobiology Database, combined with lithologic data from Macrostrat, to demonstrate that low diversity was caused by the collapse

    更新日期:2020-04-23
  • X-ray computed tomography reveals that grain protrusion controls critical shear stress for entrainment of fluvial gravels
    Geology (IF 5.006) Pub Date : 2020-02-01
    Rebecca A. Hodge, Hal Voepel, Julian Leyland, David A. Sear, Sharif Ahmed

    The critical shear stress (τc) for grain entrainment is a poorly constrained control on bedload transport rates in rivers. Direct calculations of τc have been hindered by the inability to measure the geometry of in situ grains; i.e., the shape and location of each grain relative to surrounding grains and the bed surface. We present the first complete suite of three-dimensional (3-D) grain geometry

    更新日期:2020-04-23
  • Postglacial erosion of bedrock surfaces and deglaciation timing: New insights from the Mont Blanc massif (western Alps)
    Geology (IF 5.006) Pub Date : 2020-02-01
    Benjamin Lehmann, Frédéric Herman, Pierre G. Valla, Georgina E. King, Rabiul H. Biswas, Susan Ivy-Ochs, Olivia Steinemann, Marcus Christl

    Since the Last Glacial Maximum, ∼20 k.y. ago, Alpine glaciers have retreated and thinned. This transition exposed bare bedrock surfaces that could then be eroded by a combination of debuttressing or local frost cracking and weathering. Quantification of the respective contributions of these processes is necessary to understand the links between long-term climate and erosion in mountains. Here, we quantified

    更新日期:2020-04-23
  • Explosive interaction of impact melt and seawater following the Chicxulub impact event
    Geology (IF 5.006) Pub Date : 2020-02-01
    Gordon R. Osinski, Richard A.F. Grieve, Patrick J.A. Hill, Sarah L. Simpson, Charles Cockell, Gail L. Christeson, Matthias Ebert, Sean Gulick, H. Jay Melosh, Ulrich Riller, Sonia M. Tikoo, Axel Wittmann

    The impact of asteroids and comets with planetary surfaces is one of the most catastrophic, yet ubiquitous, geological processes in the solar system. The Chicxulub impact event, which has been linked to the Cretaceous-Paleogene (K-Pg) mass extinction marking the beginning of the Cenozoic Era, is arguably the most significant singular geological event in the past 100 million years of Earth’s history

    更新日期:2020-04-23
  • Recent inversion of the Tyrrhenian Basin
    Geology (IF 5.006) Pub Date : 2020-02-01
    Nevio Zitellini, César R. Ranero, M. Filomena Loreto, Marco Ligi, Marco Pastore, Filippo D’Oriano, Valenti Sallares, Ingo Grevemeyer, Stefan Moeller, Manel Prada

    The Tyrrhenian Basin is a region created by Neogene extensional tectonics related to slab rollback of the east-southeast–migrating Apennine subduction system, commonly believed to be actively underthrusting the Calabrian arc. A compilation of >12,000 km of multichannel seismic profiles, much of them recently collected or reprocessed, provided closer scrutiny and the mapping of previously undetected

    更新日期:2020-04-23
  • The role of impacts on Archaean tectonics
    Geology (IF 5.006) Pub Date : 2020-02-01
    C. O’Neill, S. Marchi, W. Bottke, R. Fu

    Field evidence from the Pilbara craton (Australia) and Kaapvaal craton (South Africa) indicate that modern tectonic processes may have been operating at ca. 3.2 Ga, a time also associated with a high density of preserved Archaean impact indicators. Recent work has suggested a causative association between large impacts and tectonic processes for the Hadean. However, impact flux estimates and spherule

    更新日期:2020-04-23
  • Plate-tectonic processes at ca. 2.0 Ga: Evidence from >600 km of plate convergence
    Geology (IF 5.006) Pub Date : 2020-02-01
    An Yin, Günther Brandl, Alfred Kröner

    We addressed when plate-tectonic processes first started on Earth by examining the ca. 2.0 Ga Limpopo orogenic belt in southern Africa. We show through palinspastic reconstruction that the Limpopo orogen originated from >600 km of west-directed thrusting, and the thrust sheet was subsequently folded by north-south compression. The common 2.7–2.6 Ga felsic plutons in the Limpopo thrust sheet and the

    更新日期:2020-04-23
  • Icequake streaks linked to potential mega-scale glacial lineations beneath an Antarctic ice stream
    Geology (IF 5.006) Pub Date : 2020-02-01
    C. Grace Barcheck, Susan Y. Schwartz, Slawek Tulaczyk

    Icequakes radiating from an ice-stream base provide insights into otherwise difficult to observe sub-kilometer-scale basal heterogeneity. We detect basal icequakes beneath an ∼3-km-wide seismic sensor network installed on the Whillans Ice Plain (WIP) in West Antarctica, and we use S-wave back-projection to detect and locate thousands of basal icequakes occurring over 14 and 21 days in January 2014

    更新日期:2020-04-23
  • Lithosphere thickness controls continental basalt compositions: An illustration using Cenozoic basalts from eastern China
    Geology (IF 5.006) Pub Date : 2020-02-01
    Pengyuan Guo, Yaoling Niu, Pu Sun, Hongmei Gong, Xiaohong Wang

    Recent studies demonstrate that lithosphere thickness variation exerts the primary control on global seafloor basalt compositions. If the mechanism of such control, i.e., the lid effect, is indeed at work, lithosphere thickness variation must also influence basaltic compositions in continental settings. To test this hypothesis, we chose to study Cenozoic basalts in eastern continental China over a

    更新日期:2020-02-01
  • ERRATUM: Why do large, deep rivers have low-angle dune beds?
    Geology (IF 5.006) Pub Date : 2020-02-01
    R.A. Kostaschuk, J.G. Venditti

    ORIGINAL ARTICLE: Geology, v. 47, p. 919–922, https://doi.org/10.1130/G46460.1 First published 20 August 2019.

    更新日期:2020-02-01
  • Do impacts impact global tectonics?
    Geology (IF 5.006) Pub Date : 2020-02-01
    Scott D. King

    Plate tectonics is the framework through which we understand the large-scale Phanerozoic history of Earth. The question of when and how plate tectonics began remains the subject of debate, in no small part because through subduction, plate tectonics destroys much of the evidence of its earlier activity. Estimates of the onset of plate tectonics vary from the Hadean (Hopkins et al., 2008), to the Archean

    更新日期:2020-02-01
  • Differences in channel and hillslope geometry record a migrating uplift wave at the Mendocino triple junction, California, USA
    Geology (IF 5.006) Pub Date : 2020-02-01
    Fiona J. Clubb, Simon M. Mudd, Martin D. Hurst, Stuart W.D. Grieve

    Tectonic plate motion, and the resulting change in land surface elevation, has been shown to have a fundamental impact on landscape morphology. Changes to uplift rates can drive a response in fluvial channels, which then drives changes to hillslopes. Because hillslopes respond on different time scales than fluvial channels, investigating the geometry of channels and hillslopes in concert provides novel

    更新日期:2020-02-01
  • Forming sulfate- and REE-rich fluids in the presence of quartz
    Geology (IF 5.006) Pub Date : 2020-02-01
    Hao Cui, Richen Zhong, Yuling Xie, Xueyin Yuan, Weihua Liu, Joël Brugger, Chang Yu

    The presence of sulfate-rich fluids in natural magmatic hydrothermal systems and some carbonatite-related rare earth element (REE) deposits is paradoxical, because sulfate salts are known for their retrograde solubility, implying that they should be insoluble in high-temperature geofluids. Here, we show that the presence of quartz can significantly change the dissolution behavior of Na2SO4, leading

    更新日期:2020-02-01
  • Sea level, carbonate mineralogy, and early diagenesis controlled δ 13 C records in Upper Ordovician carbonates
    Geology (IF 5.006) Pub Date : 2020-02-01
    David S. Jones, R. William Brothers, Anne-Sofie Crüger Ahm, Nicholas Slater, John A. Higgins, David A. Fike

    Stratigraphic variability in the geochemistry of sedimentary rocks provides critical data for interpreting paleoenvironmental change throughout Earth history. However, the vast majority of pre-Jurassic geochemical records derive from shallow-water carbonate platforms that may not reflect global ocean chemistry. Here, we used calcium isotope ratios (δ44Ca) in conjunction with minor-element geochemistry

    更新日期:2020-02-01
  • Dry sediment loading of headwater channels fuels post-wildfire debris flows in bedrock landscapes
    Geology (IF 5.006) Pub Date : 2020-02-01
    Roman A. DiBiase, Michael P. Lamb

    Landscapes following wildfire commonly have significant increases in sediment yield and debris flows that pose major hazards and are difficult to predict. Ultimately, post-wildfire sediment yield is governed by processes that deliver sediment from hillslopes to channels, but it is commonly unclear the degree to which hillslope sediment delivery is driven by wet versus dry processes, which limits the

    更新日期:2020-02-01
  • Foundered lithospheric segments dropped into the mantle transition zone beneath southern California, USA
    Geology (IF 5.006) Pub Date : 2020-02-01
    Youqiang Yu, Stephen S. Gao, Kelly H. Liu, Dapeng Zhao

    The diverse range of active tectonics occurring in southern California, USA, offers an opportunity to explore processes of continental deformation and modification in response to the instability of the Pacific and Farallon plates. Here, we present a high-resolution receiver-function image of the mantle transition zone (MTZ). Our result reveals significant lateral heterogeneities in the deep mantle

    更新日期:2020-02-01
  • How shear helps lava to flow
    Geology (IF 5.006) Pub Date : 2020-02-01
    A. Harris, S. Mannini, S. Thivet, M.O. Chevrel, L. Gurioli, N. Villeneuve, A. Di Muro, A. Peltier

    Understanding the thermo-rheological regime and physical character of lava while it is flowing is crucial if we are to adequately model lava flow emplacement dynamics. We present measurements from simultaneous sampling and thermal imaging across the full width of an active channel at Piton de la Fournaise (La Réunion, France). Our data set involves measurements of flow dynamics at three sites down-channel

    更新日期:2020-02-01
  • Salt tectonics in the Eastern Mediterranean Sea: Where a giant delta meets a salt giant
    Geology (IF 5.006) Pub Date : 2020-02-01
    Elchanan Zucker, Zohar Gvirtzman, Josh Steinberg, Yehouda Enzel

    The circum-Nile deformation belt (CNDB) demonstrates the interaction between a giant delta and a giant salt body. The semi-radial shape of the CNDB is commonly interpreted as the product of salt squeezing out from under the Nile Delta. We demonstrate, however, that this is not the dominant process, because the delta and its deep-sea fan do not reach the deep-basin salt. The distal part of the deep-sea

    更新日期:2020-02-01
  • Biomediation of submarine sediment gravity flow dynamics
    Geology (IF 5.006) Pub Date : 2020-01-01
    Melissa J. Craig, Jaco H. Baas, Kathryn J. Amos, Lorna J. Strachan, Andrew J. Manning, David M. Paterson, Julie A. Hope, Scott D. Nodder, Megan L. Baker

    Sediment gravity flows are the primary process by which sediment and organic carbon are transported from the continental margin to the deep ocean. Up to 40% of the total marine organic carbon pool is represented by cohesive extracellular polymeric substances (EPS) produced by microorganisms. The effect of these polymers on sediment gravity flows has not been investigated, despite the economic and societal

    更新日期:2019-12-19
  • Mechanism for enhanced eolian dust flux recorded in North Pacific Ocean sediments since 4.0 Ma: Aridity or humidity at dust source areas in the Asian interior?
    Geology (IF 5.006) Pub Date : 2020-01-01
    Qiang Zhang, Qingsong Liu, Andrew P. Roberts, Juan C. Larrasoaña, Xuefa Shi, Chunsheng Jin

    Eolian material within pelagic North Pacific Ocean (NPO) sediments contains considerable information about paleoclimate evolution in Asian dust source areas. Eolian signals preserved in NPO sediments have been used as indices for enhanced Asian interior aridity. We here report a detailed eolian dust record, with chemical index of alteration (CIA) and Rb/Sr variations, for NPO sediments from Ocean Drilling

    更新日期:2019-12-19
  • Operation of the boreal peatland methane cycle across the past 16 k.y.
    Geology (IF 5.006) Pub Date : 2020-01-01
    Yanhong Zheng, Zhengkun Fang, Tongyu Fan, Zhao Liu, Zhangzhang Wang, Qiyuan Li, Richard D. Pancost, B. David A. Naafs

    The role of boreal wetlands in driving variations in atmospheric methane (CH4) concentrations across the last deglaciation (20–10 ka) and the Holocene is debated. Most studies infer the sources of atmospheric methane via ice-core records of methane concentration and its light stable isotopic composition. However, direct evidence for variations in the methane cycle from the wetlands themselves is relatively

    更新日期:2019-12-18
  • Evolution of the melt source during protracted crustal anatexis: An example from the Bhutan Himalaya
    Geology (IF 5.006) Pub Date : 2020-01-01
    Thomas Hopkinson, Nigel Harris, Nick M.W. Roberts, Clare J. Warren, Sam Hammond, Christopher J. Spencer, Randall R. Parrish

    The chemical compositions of magmatic zircon growth zones provide powerful insight into evolving magma compositions due to their ability to record both time and the local chemical environment. In situ U-Pb and Hf isotope analyses of zircon rims from Oligocene–Miocene leucogranites of the Bhutan Himalaya reveal, for the first time, an evolution in melt composition between 32 and 12 Ma. The data indicate

    更新日期:2019-12-18
  • Phosphorus burial in ferruginous SiO 2 -rich Mesoproterozoic sediments
    Geology (IF 5.006) Pub Date : 2020-01-01
    Brooke R. Johnson, Rosalie Tostevin, Philip Gopon, Jon Wells, Stuart A. Robinson, Nicholas J. Tosca

    Persistently low atmospheric oxygen requires that net organic carbon burial was muted through much of Earth’s middle age. In order to achieve global mass balance with respect to O2, recent models have suggested that redox-dependent mechanisms, such as Fe(II)-phosphate precipitation, limited phosphate availability in dominantly anoxic and ferruginous oceans, in turn limiting net primary production,

    更新日期:2019-12-18
  • Revisiting groundwater carbon fluxes to the ocean with implications for the carbon cycle
    Geology (IF 5.006) Pub Date : 2020-01-01
    Shuang Zhang, Noah J. Planavsky

    Compared with riverine systems, the influence of groundwater on the global carbon cycle has remained underexplored. Here, we provide a new estimate of the bicarbonate fluxes from fresh groundwater to the ocean by coupling a statistical and hydrological analysis of groundwater and river samples across the contiguous United States with a study of global groundwater characteristics. We find that the mean

    更新日期:2019-12-18
  • Pedogenic siderites fossilizing Ediacaran soil microorganisms on the Baltica paleocontinent
    Geology (IF 5.006) Pub Date : 2020-01-01
    Maciej J. Bojanowski, Magdalena Goryl, Barbara Kremer, Beata Marciniak-Maliszewska, Leszek Marynowski, Jan Środoń

    Ediacaran siderite-bearing sedimentary rocks from the western part of the East European craton exhibit features typical of redoximorphic paleosols, including pedogenic siderite (e.g., sphaerosiderite) with uniform and negative δ18O and highly variable δ13C values. The siderite precipitated in water-logged soils in a hot and humid climate, and represents a rare example of pedogenic siderite formed before

    更新日期:2019-12-18
  • Calcium isotope evidence for environmental variability before and across the Cretaceous-Paleogene mass extinction
    Geology (IF 5.006) Pub Date : 2020-01-01
    Benjamin J. Linzmeier, Andrew D. Jacobson, Bradley B. Sageman, Matthew T. Hurtgen, Meagan E. Ankney, Sierra V. Petersen, Thomas S. Tobin, Gabriella D. Kitch, Jiuyuan Wang

    Carbon dioxide release during Deccan Traps volcanism and the Chicxulub impact likely contributed to the Cretaceous-Paleogene (K-Pg) mass extinction; however, the intensity and duration of CO2 input differed between the two events. Large and rapid addition of CO2 to seawater causes transient decreases in pH, [CO32–], and carbonate mineral saturation states. Compensating mechanisms, such as dissolution

    更新日期:2019-12-18
  • Fossil subduction recorded by quartz from the coesite stability field
    Geology (IF 5.006) Pub Date : 2020-01-01
    M. Alvaro, M.L. Mazzucchelli, R.J. Angel, M. Murri, N. Campomenosi, M. Scambelluri, F. Nestola, A. Korsakov, A.A. Tomilenko, F. Marone, M. Morana

    Metamorphic rocks are the records of plate tectonic processes whose reconstruction relies on correct estimates of the pressures and temperatures (P-T) experienced by these rocks through time. Unlike chemical geothermobarometry, elastic geobarometry does not rely on chemical equilibrium between minerals, so it has the potential to provide information on overstepping of reaction boundaries and to identify

    更新日期:2019-12-18
  • A 1.25 Ga depositional age for the “Paleoproterozoic” Mapedi red beds, Kalahari manganese field, South Africa: New constraints on the timing of oxidative weathering and hematite mineralization
    Geology (IF 5.006) Pub Date : 2020-01-01
    Birger Rasmussen, Janet R. Muhling, Jian-Wei Zi, Harilaos Tsikos, Woodward W. Fischer

    The Great Oxidation Event (GOE) is marked by the loss of readily oxidizable detrital minerals and the onset of oxidative weathering. One of the oldest post-GOE weathering surfaces, which extends for almost 350 km along strike, occurs in Griqualand West, South Africa. It is best preserved east of the Blackridge thrust, where oxidized paleoweathering profiles are developed below the unconformity at the

    更新日期:2019-12-18
  • Reef-flat and back-reef development in the Great Barrier Reef caused by rapid sea-level fall during the Last Glacial Maximum (30–17 ka)
    Geology (IF 5.006) Pub Date : 2020-01-01
    Kazuhiko Fujita, Noriko Yagioka, Choko Nakada, Hironobu Kan, Yosuke Miyairi, Yusuke Yokoyama, Jody M. Webster

    Reef growth patterns and the development of associated environments have been extensively studied from reef deposits from Holocene and previous interglacial highstands. However, reefs that grew during glacial lowstands are comparatively poorly understood. Here we show the formation of reef-flat and back-reef environments following rapid sea-level fall (15–20 mm yr−1 and 20–40 m in magnitude) during

    更新日期:2019-12-18
  • The preparatory phase of the M w 6.1 2009 L’Aquila (Italy) normal faulting earthquake traced by foreshock time-lapse tomography
    Geology (IF 5.006) Pub Date : 2020-01-01
    Paola Baccheschi, Pasquale De Gori, Fabio Villani, Fabio Trippetta, Claudio Chiarabba

    The Mw 6.1 (6 April 2009) L’Aquila (Italy) earthquake occurred in one of the most seismically active areas of central Italy and was preceded by a three-month-long foreshock period. Thanks to recordings by a regional permanent network, we derive for the first time P- and S-wave velocity tomographic models of a major fault prone to an imminent main shock. Close to the Mw 6.1 hypocenter, we observe high

    更新日期:2019-12-18
  • Focused fluid seepage related to variations in accretionary wedge structure, Hikurangi margin, New Zealand
    Geology (IF 5.006) Pub Date : 2020-01-01
    Sally J. Watson, Joshu J. Mountjoy, Philip M. Barnes, Gareth J. Crutchley, Geoffroy Lamarche, Ben Higgs, Jess Hillman, Alan R. Orpin, Aaron Micallef, Helen Neil, John Mitchell, Arne Pallentin, Tim Kane, Susi Woelz, David Bowden, Ashley A. Rowden, Ingo A. Pecher

    Hydrogeological processes influence the morphology, mechanical behavior, and evolution of subduction margins. Fluid supply, release, migration, and drainage control fluid pressure and collectively govern the stress state, which varies between accretionary and nonaccretionary systems. We compiled over a decade of published and unpublished acoustic data sets and seafloor observations to analyze the distribution

    更新日期:2019-12-18
  • Inherited terrane properties explain enigmatic post-collisional Himalayan-Tibetan evolution
    Geology (IF 5.006) Pub Date : 2020-01-01
    Sean Kelly, Christopher Beaumont, Jared P. Butler

    Observations highlight the complex tectonic, magmatic, and geodynamic phases of the Cenozoic post-collisional evolution of the Himalayan-Tibetan orogen and show that these phases migrate erratically among terranes accreted to Asia prior to the Indian collision. This behavior contrasts sharply with the expected evolution of large, hot orogens formed by collision of lithospheres with laterally uniform

    更新日期:2019-12-18
  • Land plant evolution decreased, rather than increased, weathering rates
    Geology (IF 5.006) Pub Date : 2020-01-01
    Michael P. D’Antonio, Daniel E. Ibarra, C. Kevin Boyce

    The repeated evolution of trees is widely thought to have enhanced the capacity of silicate weathering via the impact of deep rooting. However, land plants are also responsible for wetland assembly and organic carbon burial. The total burial output of carbon via both organic and inorganic deposition must balance input to the exogenic system from volcanic outgassing on million-year time scales. Increased

    更新日期:2019-12-18
  • Uranium isotopic constraints on the nature of the prehistoric flood at the Lajia site, China
    Geology (IF 5.006) Pub Date : 2020-01-01
    Le Li, Jun Chen, David William Hedding, Yuanhe Fu, Maolin Ye, Gaojun Li

    The catastrophic landslide-dam outburst flood, possibly caused by the same earthquake that destroyed the well-dated Lajia archaeological site, in the upper reaches of the Yellow River in China, may provide an accurate constraint on the age of the first Chinese dynasty (Xia Dynasty), which, according to Chinese ancient documents, has been associated with flood-control activities. The key link between

    更新日期:2019-12-18
  • Stable oxygen and carbon isotopes of carbonates in lake sediments as a paleoflood proxy
    Geology (IF 5.006) Pub Date : 2020-01-01
    Lucas Kämpf, Birgit Plessen, Stefan Lauterbach, Carla Nantke, Hanno Meyer, Bernhard Chapligin, Achim Brauer

    Lake sediments are increasingly explored as reliable paleoflood archives. In addition to established flood proxies including detrital layer thickness, chemical composition, and grain size, we explore stable oxygen and carbon isotope data as paleoflood proxies for lakes in catchments with carbonate bedrock geology. In a case study from Lake Mondsee (Austria), we integrate high-resolution sediment trapping

    更新日期:2019-12-18
  • Recrystallization and chemical changes in apatite in response to hypervelocity impact
    Geology (IF 5.006) Pub Date : 2020-01-01
    Gavin G. Kenny, Andreas Karlsson, Martin Schmieder, Martin J. Whitehouse, Alexander A. Nemchin, Jeremy J. Bellucci

    Despite the wide utility of apatite, Ca5(PO4)3(F,Cl,OH), in the geosciences, including tracing volatile abundances on the Moon and Mars, little is known about how the mineral responds to the extreme temperatures and pressures associated with hypervelocity impacts. To address this deficiency, we here present the first microstructural analysis and chemical mapping of shocked apatite from a terrestrial

    更新日期:2019-12-18
  • Lead pollution can be detected in North America for thousands of years
    Geology (IF 5.006) Pub Date : 2019-12-01
    David P. Pompeani

    Humans have contaminated environments across the world with lead (Pb). Clair Patterson was the first to realize that Pb in the 20th century environment was elevated above natural levels (Patterson, 1965). Lee and Tallis (1973) showed that this modern increase in Pb could be detected in lake sediments. Soon after, researchers compiled historical and archaeological evidence to estimate Pb production

    更新日期:2019-11-20
  • Statistical analysis of crystal populations and links to volcano deformation for more robust estimates of magma replenishment volumes
    Geology (IF 5.006) Pub Date : 2019-12-01
    Lilu Cheng, Fidel Costa

    Forecasting the timing and size of volcanic eruptions requires a proper interpretation of multiparametric monitoring signals. Studies of the erupted rocks can provide critical information on the processes and volcano plumbing system that is needed to decode the monitoring signals. Here we present the results of a petrological study of plagioclase phenocrysts using a new statistical approach that allows

    更新日期:2019-11-20
  • Fault reactivation and strain partitioning across the brittle-ductile transition
    Geology (IF 5.006) Pub Date : 2019-12-01
    Gabriel G. Meyer, Nicolas Brantut, Thomas M. Mitchell, Philip G. Meredith

    The so-called “brittle-ductile transition” is thought to be the strongest part of the lithosphere, and defines the lower limit of the seismogenic zone. It is characterized not only by a transition from localized to distributed (ductile) deformation, but also by a gradual change in microscale deformation mechanism, from microcracking to crystal plasticity. These two transitions can occur separately

    更新日期:2019-11-20
  • Nanoscale evidence for temperature-induced transient rheology and postseismic fault healing
    Geology (IF 5.006) Pub Date : 2019-12-01
    A.K. Ault, J.L. Jensen, R.G. McDermott, F.-A. Shen, B.R. Van Devener

    Friction-generated heat and the subsequent thermal evolution control fault material properties and thus strength during the earthquake cycle. We document evidence for transient, nanoscale fault rheology on a high-gloss, light-reflective hematite fault mirror (FM). The FM cuts specularite with minor quartz from the Pleistocene El Laco Fe-ore deposit, northern Chile. Scanning and transmission electron

    更新日期:2019-11-20
  • The origin of large gypsum crystals in the Geode of Pulpí (Almería, Spain)
    Geology (IF 5.006) Pub Date : 2019-12-01
    A. Canals, A.E.S. Van Driessche, F. Palero, J.M. García-Ruiz

    The Geode of Pulpí (Almería, Spain) is an ∼11 m3 ovoid cavity, the walls of which are covered with meter-sized idiomorphic and highly transparent gypsum (CaSO4●2H2O) crystals. We performed a thorough study based on field work, and petrographic and geochemical data collection, which aimed to reconstruct the geological history leading to the formation of this geode. The geode is hosted in mineralized

    更新日期:2019-11-20
  • The Bayan Obo (China) giant REE accumulation conundrum elucidated by intense magmatic differentiation of carbonatite
    Geology (IF 5.006) Pub Date : 2019-12-01
    Kuifeng Yang, Hongrui Fan, Franco Pirajno, Xiaochun Li

    The Bayan Obo deposit in China is endowed with the largest rare earth element (REE) resource in the world. The mechanism resulting in this REE enrichment has been the focus of many studies. Carbonatite is known globally as the most favorable carrier of REE ores. In the Bayan Obo deposit, REE ores are hosted in dolomites (including coarse-grained and fine-grained varieties), and many carbonatite dikes

    更新日期:2019-11-20
  • Pre-Columbian lead pollution from Native American galena processing and land use in the midcontinental United States
    Geology (IF 5.006) Pub Date : 2019-12-01
    Broxton W. Bird, Jeremy J. Wilson, Jaime Escobar, George D. Kamenov, Harvie J. Pollard, G. William Monaghn

    The presence and sources of pre-Columbian (before 1492 CE) lead (Pb) pollution in the midcontinental United States were investigated using geochemical and Pb isotope analyses on sediment cores recovered from Avery Lake, a floodplain lake located directly adjacent to the Kincaid Mounds archaeological site on the lower Ohio River, Illinois. Geochemical results indicate the presence of Pb pollution during

    更新日期:2019-11-20
  • Rapid clay precipitation in explosion-induced fractures
    Geology (IF 5.006) Pub Date : 2019-12-01
    Erika Swanson, Aviva Sussman, Jennifer Wilson

    Fractures within the earth control rock strength and fluid flow, but their dynamic nature is not well understood. As part of a series of underground chemical explosions in granite in Nevada, we collected and analyzed microfracture density data sets prior to, and following, individual explosions. Our work shows an ∼4-fold increase in both open and filled microfractures following the explosions. Based

    更新日期:2019-11-20
  • Discovery of a 400 km 2 honeycomb structure mimicking a regional unconformity on three-dimensional seismic data
    Geology (IF 5.006) Pub Date : 2019-12-01
    Rosine Riera, Julien Bourget, Victorien Paumard, Moyra E.J. Wilson, Jeffrey Shragge, Annette D. George, Jean Borgomano, Thomas Wilson

    Recognition of seismic unconformities is crucial for interpreting basin history from seismic reflection data sets in both siliciclastic and carbonate settings. While it is well established that non-erosional changes in sedimentary facies can create seismic reflections that mimic seismic unconformities (i.e., pseudo-unconformities), these features are generally considered to be localized and uncommon

    更新日期:2019-11-20
  • A true polar wander trigger for the Great Jurassic East Asian Aridification
    Geology (IF 5.006) Pub Date : 2019-12-01
    Zhiyu Yi, Yongqing Liu, Joseph G. Meert

    A drastic environmental change occurred during the Middle to Late Jurassic as much of East Asia transitioned from a wet seasonal to an extremely arid climate. The timing, scope, and especially mechanism for this aridification are contentious. In this study, we report paleomagnetic data and ages from Jurassic volcanic rocks in North China and for the first time reveal a large-scale southward displacement

    更新日期:2019-11-20
  • Mid-Holocene extinction of cold-water corals on the Namibian shelf steered by the Benguela oxygen minimum zone
    Geology (IF 5.006) Pub Date : 2019-12-01
    Leonardo Tamborrino, Claudia Wienberg, Jürgen Titschack, Paul Wintersteller, Furu Mienis, Andrea Schröder-Ritzrau, André Freiwald, Covadonga Orejas, Wolf-Christian Dullo, Julia Haberkern, Dierk Hebbeln

    An exceptionally large cold-water coral mound province (CMP) was recently discovered extending over 80 km along the Namibian shelf (offshore southwestern Africa) in water depths of 160–270 m. This hitherto unknown CMP comprises >2000 mounds with heights of up to 20 m and constitutes the largest CMP known from the southeastern Atlantic Ocean. Uranium-series dating revealed a short but intense pulse

    更新日期:2019-11-20
  • Detrital garnet geochronology: Application in tributaries of the French Broad River, Southern Appalachian Mountains, USA
    Geology (IF 5.006) Pub Date : 2019-12-01
    Kathryn A. Maneiro, Ethan F. Baxter, Scott D. Samson, Horst R. Marschall, Jack Hietpas

    Nineteen single-grain detrital garnet ages from a tributary to the French Broad River (North Carolina, USA) establish a novel approach to Sm-Nd detrital garnet geochronology wherein the equilibrium bulk-rock composition lost during weathering and transport is replaced with the composition of inclusions leached from within each garnet grain. Detrital garnet ages were compared to published detrital zircon

    更新日期:2019-11-20
  • Serra Sul diamictite of the Carajás Basin (Brazil): A Paleoproterozoic glaciation on the Amazonian craton
    Geology (IF 5.006) Pub Date : 2019-12-01
    Raphael Araújo, Afonso Nogueira

    This paper reports the discovery of glacial deposits of likely Siderian–Rhyacian age (2.58–2.06 Ga) in South America (Carajás Basin, Brazil), thereby expanding the potential reach of Paleoproterozoic glaciations to the Amazonian craton for the first time. Glacially derived diamictites are stacked within a hitherto unrecognized ∼600-m-thick siliciclastic succession, here named the Serra Sul Formation

    更新日期:2019-11-20
  • Oman corals suggest that a stronger winter shamal season caused the Akkadian Empire (Mesopotamia) collapse
    Geology (IF 5.006) Pub Date : 2019-12-01
    Takaaki K. Watanabe, Tsuyoshi Watanabe, Atsuko Yamazaki, Miriam Pfeiffer

    The Akkadian Empire was the first united empire in Mesopotamia and was established at 4.6 kyr B.P. (where present is A.D. 1950). The empire abruptly collapsed in 4.2 ± 0.2 kyr B.P. Seasonal-scale climatic dynamics behind this collapse have not yet been resolved. Here, we present monthly climatic parameters (temperature and hydrology) inferred from fossil Omani corals that lived between 4.5 and 2.9

    更新日期:2019-11-20
  • Progressive tilting of salt-bearing continental margins controls thin-skinned deformation
    Geology (IF 5.006) Pub Date : 2019-12-01
    Zhiyuan Ge, Michael Warsitzka, Matthias Rosenau, Rob L. Gawthorpe

    As a primary driving force, margin tilting is crucial for gravity-driven thin-skinned salt tectonics. We investigated how instant versus progressive margin tilting mechanisms influence salt tectonics using an analogue modeling setup where tilting rate could be controlled. Instant tilting resulted in initially high deformation rates, triggering widely distributed upslope extension and downslope contraction

    更新日期:2019-11-20
  • Differential bank migration and the maintenance of channel width in meandering river bends
    Geology (IF 5.006) Pub Date : 2019-12-01
    Jasmine Mason, David Mohrig

    Comparison of three bare-earth lidar data sets along 30 consecutive river bends on the Trinity River in Texas, USA, shows that differential migration of river banks in a channel bend counterbalances past bank migrations so that a statistically steady-state channel width is maintained. Two difference maps created from lidar flown in 2011, 2015, and 2017 capture this temporal variability in the relative

    更新日期:2019-11-20
  • Symbiont arrangement and metabolism can explain high δ 13 C in Eocene planktonic foraminifera
    Geology (IF 5.006) Pub Date : 2019-12-01
    Daniel E. Gaskell, Pincelli M. Hull

    An important question in climate modeling is whether carbon cycling is fundamentally different in warm versus cold climate states. A key line of evidence regarding this question comes from the unusually large difference in carbon-isotope values (δ13C) between shallow-dwelling muricate foraminifera and foraminifera living deeper in the water column in the Paleogene. This has been interpreted as evidence

    更新日期:2019-11-20
  • Coupled stratigraphic and U-Pb zircon age constraints on the late Paleozoic icehouse-to-greenhouse turnover in south-central Gondwana
    Geology (IF 5.006) Pub Date : 2019-12-01
    Neil Patrick Griffis, Isabel Patricia Montañez, Roland Mundil, Jon Richey, John Isbell, Nick Fedorchuk, Bastien Linol, Roberto Iannuzzi, Fernando Vesely, Thammy Mottin, Eduardo da Rosa, Brenhin Keller, Qing-Zhu Yin

    The demise of the Late Paleozoic Ice Age has been hypothesized as diachronous, occurring first in western South America and progressing eastward across Africa and culminating in Australia over an ∼60 m.y. period, suggesting tectonic forcing mechanisms that operate on time scales of 106 yr or longer. We test this diachronous deglaciation hypothesis for southwestern and south-central Gondwana with new

    更新日期:2019-11-20
  • Sea-level driven acceleration in coastal forest retreat
    Geology (IF 5.006) Pub Date : 2019-12-01
    Nathalie W. Schieder, Matthew L. Kirwan

    Ghost forests, consisting of dead trees adjacent to marshes, are a striking feature of low-lying coastal and estuarine landscapes, and they represent the migration of coastal ecosystems with relative sea-level rise (RSLR). Although ghost forests have been observed along many coastal margins, rates of ecosystem change and their dependence on RSLR remain poorly constrained. Here, we reconstructed forest

    更新日期:2019-11-20
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