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Anatomy of a crustal-scale accretionary complex: Insights from deep seismic sounding of the onshore western Makran subduction zone, Iran Geology (IF 4.768) Pub Date : 2021-01-01 Christian Haberland, Mohammad Mokhtari, Hassan Ali Babaei, Trond Ryberg, Mehdi Masoodi, Abdolreza Partabian, Jörn Lauterjung
The Makran subduction zone has produced M 8+ earthquakes and subsequent tsunamis in historic times, hence indicating high risk for the coastal regions of southern Iran, Pakistan, and neighboring countries. Besides this, the Makran subduction zone is an end-member subduction zone featuring extreme properties, with one of the largest sediment inputs and the widest accretionary wedge on Earth. While surface
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Rapid expansion of meso-megathermal rain forests into the southern high latitudes at the onset of the Paleocene-Eocene Thermal Maximum Geology (IF 4.768) Pub Date : 2021-01-01 E.P. Huurdeman, J. Frieling, T. Reichgelt, P.K. Bijl, S.M. Bohaty, G.R. Holdgate, S.J. Gallagher, F. Peterse, D.R. Greenwood, J. Pross
Current knowledge of terrestrial ecosystem response to the Paleocene-Eocene Thermal Maximum (PETM; ca. 56 Ma) is largely based on the midlatitudes of the Northern Hemisphere. To more fully reconstruct global terrestrial ecosystem response to the PETM, we generated vegetation and biomarker proxy records from an outcrop section on the southern coast of Australia (∼60°S paleolatitude). We documented a
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Impact of fault damage on eastern Tibet topography Geology (IF 4.768) Pub Date : 2021-01-01 Heather M. Kirkpatrick, Seulgi Moon, An Yin, T. Mark Harrison
Tectonic deformation can influence spatiotemporal patterns of erosion by changing both base level and the mechanical state of bedrock. Although base-level change and the resulting erosion are well understood, the impact of tectonic damage on bedrock erodibility has rarely been quantified. Eastern Tibet, a tectonically active region with diverse lithologies and multiple active fault zones, provides
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Gulf of Nuna: Astrochronologic correlation of a Mesoproterozoic oceanic euxinic event Geology (IF 4.768) Pub Date : 2021-01-01 Ross N. Mitchell, Uwe Kirscher, Marcus Kunzmann, Yebo Liu, Grant M. Cox
The ca. 1.4 Ga Velkerri and Xiamaling Formations, in Australia and the north China craton, respectively, are both carbonaceous shale deposits that record a prominent euxinic interval and were intruded by ca. 1.3 Ga dolerite sills. These similarities raise the possibility that these two units correlate, which would suggest the occurrence of widespread euxinia, organic carbon burial, and source rock
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Stagnant slab front within the mantle transition zone controls the formation of Cenozoic intracontinental high-Mg andesites in northeast Asia Geology (IF 4.768) Pub Date : 2021-01-01 Wen-Liang Xu, Jia-Hui Chen, Ai-Hua Weng, Jie Tang, Feng Wang, Chun-Guang Wang, Peng Guo, Yi-Ni Wang, Hao Yang, Andrey A. Sorokin
The geochemistry of Cenozoic intracontinental high-Mg andesites (HMAs) in northeast Asia, together with regional geophysical data, offers an opportunity to explore the genetic relationship between the formation of intracontinental HMAs and subduction of the Pacific plate. Compared with primary HMAs in arcs, Cenozoic intracontinental HMAs in northeast Asia have lower Mg# [100 × Mg/(Mg + Fe2+)] values
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Formation of the First Bend in the late Eocene gave birth to the modern Yangtze River, China Geology (IF 4.768) Pub Date : 2021-01-01 Hongbo Zheng, Peter D. Clift, Mengying He, Zixuan Bian, Gaozheng Liu, Xiaochun Liu, Lei Xia, Qing Yang, Fred Jourdan
The First Bend on the Yangtze River (China), the point where the river ceases flowing toward the south and heads toward the northeast, has been one of the most strongly debated geomorphic features in Asia because it holds the key to understanding the history of the Yangtze River and is linked to the tectonically driven surface uplift of the southeastern Tibetan Plateau. Mid- to upper Eocene sedimentary
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Negligible surface uplift following foundering of thickened central Tibetan lower crust Geology (IF 4.768) Pub Date : 2021-01-01 Yunchuan Zeng, Mihai N. Ducea, Jifeng Xu, Jianlin Chen, Yan-Hui Dong
This study used clinopyroxene (cpx) compositions and zircon Hf-O isotopes of Eocene adakitic rocks (EARs) from the Qiangtang block to resolve the mechanism(s) responsible for the formation of the central Tibetan Plateau. The two leading and opposing hypotheses for the origin of these rocks are (1) partially molten foundered lower crust, and (2) partial melting of continentally subducted upper crust
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Methanogen microfossils and methanogenesis in Permian lake deposits Geology (IF 4.768) Pub Date : 2021-01-01 Funing Sun, Wenxuan Hu, Xiaolin Wang, Jian Cao, Bin Fu, Haiguang Wu, Shengchao Yang
Methanogens are methane-producing archaea (some of the most primitive organisms on Earth), which possess great phylogenetic and ecological diversity in modern ecosystems. However, cellular fossil evidence of methanogens remains extremely scarce throughout the geological record. Here, we report a new population of spheroidal microstructures composed of dolomite observed in Permian lake deposits in northwestern
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Seismic anisotropy in southern Costa Rica confirms upper mantle flow from the Pacific to the Caribbean Geology (IF 4.768) Pub Date : 2021-01-01 Vadim Levin, Stephen Elkington, James Bourke, Ivonne Arroyo, Lepolt Linkimer
Surrounded by subducting slabs and continental keels, the upper mantle of the Pacific is largely prevented from mixing with surrounding areas. One possible outlet is beneath the southern part of the Central American isthmus, where regional observations of seismic anisotropy, temporal changes in isotopic composition of volcanic eruptions, and considerations of dynamic topography all suggest upper mantle
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Taking time to twist a continent—Multistage origin of the New Zealand orocline Geology (IF 4.768) Pub Date : 2021-01-01 S. Lamb, N. Mortimer
In New Zealand, a giant coherent “Z” shape is defined by several curvilinear pre-Cenozoic basement terranes that extend across Zealandia for >1500 km along strike. It is widely assumed that this curvature was the result of bending during the Neogene, which together with ∼450 km of dextral displacement on the Alpine fault accommodated a total of ∼750 km of dextral shear through the New Zealand plate
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Venus tesserae feature layered, folded, and eroded rocks Geology (IF 4.768) Pub Date : 2021-01-01 Paul K. Byrne, Richard C. Ghail, Martha S. Gilmore, A.M. Celâl Şengör, Christian Klimczak, David A. Senske, Jennifer L. Whitten, Sara Khawja, Richard E. Ernst, Sean C. Solomon
Tesserae on Venus are locally the stratigraphically oldest units preserved on the planet. These regions are characterized by pervasive tectonic deformation including normal faults, grabens, thrust faults, and folds. In multiple tesserae, sets of (often highly) curved, parallel linear features are also present. These features strongly resemble terracing in layered volcanic or sedimentary sequences on
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Immiscibility and the origin of ladder structures, mafic layering, and schlieren in plutons Geology (IF 4.768) Pub Date : 2021-01-01 Allen F. Glazner, John M. Bartley, Bryan S. Law
Granitic plutons worldwide contain ladder structures (LSs) that consist of nested trough-shaped layers alternating between mafic and felsic compositions. LSs and other forms of modal layering have been attributed to crystal accumulation, but their chemical trends differ greatly from those of cumulates and are discordant with chemical variations of their granitic hosts. Mafic layers reach extreme enrichments
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Experimental evidence supports early silica cementation of the Ediacara Biota Geology (IF 4.768) Pub Date : 2021-01-01 Silvina Slagter, Lidya G. Tarhan, Weiduo Hao, Noah J. Planavsky, Kurt O. Konhauser
Casts and molds of soft-bodied organisms in Ediacaran sandstones (“Ediacara-style” fossilization) have played an important role in reconstruction of the emergence and radiation of early complex macroscopic life. However, the preservational processes responsible for the Ediacara fossil record are still vigorously debated. Whereas classic studies proposed fossilization via rapid sulfide mineralization
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Reconstructing crustal thickness evolution from europium anomalies in detrital zircons Geology (IF 4.768) Pub Date : 2021-01-01 Ming Tang, Wei-Qiang Ji, Xu Chu, Anbin Wu, Chen Chen
A new data compilation shows that in intermediate to felsic rocks, zircon Eu/Eu* [chondrite normalized Eu/ ] correlates with whole rock La/Yb, which has been be used to infer crustal thickness. The resultant positive correlation between zircon Eu/Eu* and crustal thickness can be explained by two processes favored during high-pressure differentiation: (1) supression of plagioclase and (2) endogenic
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Slip rate determined from cosmogenic nuclides on normal-fault facets Geology (IF 4.768) Pub Date : 2021-01-01 Jim Tesson, Lucilla Benedetti, Vincent Godard, Catherine Novaes, Jules Fleury, the ASTER Team
Facets are major topographic features built over several 100 k.y. above active normal faults. Their development integrates cumulative displacements over a longer time frame than many other geomorphological markers, and they are widespread in diverse extensional settings. We have determined the 36Cl cosmogenic nuclide concentration on limestone faceted spurs at four sites in the Central Apennines (Italy)
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Temperature change in subtropical southeastern Africa during the past 790,000 yr Geology (IF 4.768) Pub Date : 2021-01-01 Manuel Chevalier, Brian M. Chase, Lynne J. Quick, Lydie M. Dupont, Thomas C. Johnson
Across the glacial-interglacial cycles of the late Pleistocene (∼700 k.y.), temperature variability at low latitudes is often considered to have been negligible compared to changes in precipitation. However, a paucity of quantified temperature records makes this difficult to reliably assess. In this study, we used the Bayesian method CREST (Climate REconstruction SofTware) to produce a 790,000 yr quantified
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Quaternary influx of proximal coarse-grained dust altered circum-Mediterranean soil productivity and impacted early human culture Geology (IF 4.768) Pub Date : 2021-01-01 Rivka Amit, Yehouda Enzel, Onn Crouvi
The carbonate mountainous landscape around most of the Mediterranean is karstic, is almost barren, and has thin soils. Erosion of preexisting thicker soils is a common hypothesis used to explain this bare terrain. An alternative hypothesis is that in the Mediterranean region, thin soils are attributed to long-distance transport of very fine, silty clay dust, resulting in low mass accumulation rates
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Permian plume-strengthened Tarim lithosphere controls the Cenozoic deformation pattern of the Himalayan-Tibetan orogen Geology (IF 4.768) Pub Date : 2021-01-01 Xi Xu, Andrew V. Zuza, An Yin, Xiubin Lin, Hanlin Chen, Shufeng Yang
The high strength of the Tarim Basin (northwestern China) lithosphere, widely regarded as a Precambrian craton, is evidenced by its resistance to Cenozoic deformation in the Himalayan-Tibetan orogen. However, Neoproterozoic suturing and early Paleozoic shortening within the Tarim Basin suggest that its rigidity is a relatively recent phenomenon with unknown cause. We reprocessed high-resolution magnetic
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Exposure-age data from across Antarctica reveal mid-Miocene establishment of polar desert climate Geology (IF 4.768) Pub Date : 2021-01-01 Perry Spector, Greg Balco
High-elevation rock surfaces in Antarctica have some of the oldest cosmogenic-nuclide exposure ages on Earth, dating back to the Miocene. A compilation of all available 3He, 10Be, and 21Ne exposure-age data from the Antarctic continent shows that exposure histories recorded by these surfaces extend back to, but not before, the mid-Miocene cooling at 14–15 Ma. At high elevation, this cooling entailed
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High-precision geochronology requires that ultrafast mantle-derived magmatic fluxes built the transcrustal Bear Valley Intrusive Suite, Sierra Nevada, California, USA Geology (IF 4.768) Pub Date : 2021-01-01 Benjamin Z. Klein, Oliver Jagoutz, Jahandar Ramezani
The Bear Valley Intrusive Suite (BVIS), located in the southernmost Sierra Nevada Batholith (SNB; California, USA) exposes a transcrustal magma system consisting of lower-crustal gabbros and volumetrically extensive middle- and upper-crustal tonalites. New chemical abrasion–isotope dilution–thermal ionization mass spectrometry U-Pb geochronology shows that the bulk of this ca. 100 Ma magmatic system
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Nailed to the craton: Stratigraphic continuity across the southeastern Canadian Cordillera with tectonic implications for ribbon continent models Geology (IF 4.768) Pub Date : 2021-01-01 M.E. McMechan, K.G. Root, P.S. Simony, D.R.M. Pattison
Cambrian and Upper Devonian to Mississippian strata can be confidently traced westward, without strike-slip offset, from the autochthonous section above North American basement into the southeastern Canadian Cordillera, and are thus “nailed” to the craton. These strata are in turn stratigraphically pinned to older (Mesoproterozoic Belt-Purcell Supergroup, Neoproterozoic Windermere Supergroup, and Ediacaran)
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Recognizing tide- and wave-dominated compound deltaic clinothems in the rock record Geology (IF 4.768) Pub Date : 2020-12-01 Yang Peng, Cornel Olariu, Ronald J. Steel
Many modern deltas exhibit a compound geometry that consists of a shoreline clinoform and a larger subaqueous clinoform connected through a subaqueous platform. Despite the ubiquity of compound clinoforms in modern deltas, very few examples have been documented from the ancient sedimentary record. We present recognition criteria for shelf compound-clinoform systems in both tide- and wave-dominated
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The life cycle of subcontinental peridotites: From rifted continental margins to mountains via subduction processes Geology (IF 4.768) Pub Date : 2020-12-01 Paola Vannucchi, Jason P. Morgan, Alina Polonia, Giancarlo Molli
Serpentinization greatly affects the physical and chemical properties of lithospheric mantle. Here we address the fate of serpentinized peridotites and their influence over an entire Wilson cycle. We document the near-surface journey of serpentinized subcontinental peridotites exhumed during rifting and continental breakup, reactivated as buoyant material during subduction, and ultimately emplaced
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Stress in the tropics? Impact of a latitudinal seawater δ 18 O gradient on Middle Jurassic temperature reconstructions at low latitudes Geology (IF 4.768) Pub Date : 2020-12-01 Matthias Alberti, Yael Leshno, Franz T. Fürsich, Yael Edelman-Furstenberg, Nils Andersen, Dieter Garbe-Schönberg
Previous stable oxygen isotope records of calcitic fossils (δ18Oshell) from Europe have been interpreted to reflect strong climatic perturbations throughout the Jurassic, but it is unknown whether they reflect global trends because data from other regions are sparse. Here, we use bivalve and brachiopod shells from western Asia and northern Africa to examine seawater temperatures at low latitudes as
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Geothermal energy and ore-forming potential of 600 °C mid-ocean-ridge hydrothermal fluids Geology (IF 4.768) Pub Date : 2020-12-01 Enikő Bali, László E. Aradi, Robert Zierenberg, Larryn W. Diamond, Thomas Pettke, Ábel Szabó, Guðmundur H. Guðfinnsson, Guðmundur Ó. Friðleifsson, Csaba Szabó
The ∼4500-m-deep Iceland Deep Drilling Project (IDDP) borehole IDDP-2 in Iceland penetrated the root of an active seawater-recharged hydrothermal system below the Mid-Atlantic Ridge. As direct sampling of pristine free fluid was impossible, we used fluid inclusions to constrain the in situ conditions and fluid composition at the bottom of the hydrothermal convection cell. The fluid temperature is ∼600
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Dune-scale cross-strata across the fluvial-deltaic backwater regime: Preservation potential of an autogenic stratigraphic signature Geology (IF 4.768) Pub Date : 2020-12-01 Chenliang Wu, Jeffrey A. Nittrouer, Travis Swanson, Hongbo Ma, Eric Barefoot, Jim Best, Mead Allison
Dune-scale cross-beds are a fundamental building block of fluvial-deltaic stratigraphy and have been recognized on Earth and other terrestrial planets. The architecture of these stratal elements reflects bed-form dynamics that are dependent on river hydrodynamic conditions, and previous work has documented a multitude of scaling relationships to describe the morphodynamic interactions between dunes
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Early onset and late acceleration of rapid exhumation in the Namche Barwa syntaxis, eastern Himalaya Geology (IF 4.768) Pub Date : 2020-12-01 Gwladys Govin, Peter van der Beek, Yani Najman, Ian Millar, Lorenzo Gemignani, Pascale Huyghe, Guillaume Dupont-Nivet, Matthias Bernet, Chris Mark, Jan Wijbrans
The Himalayan syntaxes, characterized by extreme rates of rock exhumation co-located with major trans-orogenic rivers, figure prominently in the debate on tectonic versus erosional forcing of exhumation. Both the mechanism and timing of rapid exhumation of the Namche Barwa massif in the eastern syntaxis remain controversial. It has been argued that coupling between crustal rock advection and surface
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Cold feet: Trackways and burrows in ice-marginal strata of the end-Ordovician glaciation (Table Mountain Group, South Africa) Geology (IF 4.768) Pub Date : 2020-12-01 Neil S. Davies, Anthony P. Shillito, Cameron R. Penn-Clarke
New observations from an outcrop of Upper Ordovician Table Mountain Group strata (Matjiesgoedkloof, Western Cape Province, South Africa) have revealed an unexpected ichnofauna that is hosted within diamictites and sandstones that were deposited by a retreating low-latitude (∼30°S) ice sheet during the Hirnantian glaciation. The locality provides a rare window onto animal-sediment interactions in an
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Rapid eruption of silicic magmas from the Paraná magmatic province (Brazil) did not trigger the Valanginian event Geology (IF 4.768) Pub Date : 2020-12-01 Brenda C. Rocha, Joshua H.F.L. Davies, Valdecir A. Janasi, Urs Schaltegger, Antônio J.R. Nardy, Nicolas D. Greber, Ana Carolina F. Lucchetti, Liza A. Polo
The Valanginian Stage is marked by a period of global positive δ13C carbon cycle perturbation and biotic crises, which are collectively referred to as the Valanginian event (VE). Many attempts have been made to link the Paraná-Etendeka large igneous province volcanism with the VE. However, currently there is no conclusive proof to support this hypothesis, since the timing and duration of the volcanic
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Indo-Atlantic plate accelerations around the Cretaceous-Paleogene boundary: A time-scale error, not a plume-push signal Geology (IF 4.768) Pub Date : 2020-12-01 L. Pérez-Díaz, G. Eagles, K. Sigloch
It has been suggested that plume arrival at the base of the lithosphere introduces a push force that overwhelms the balance of torques driving plate circuits, leading to plate-tectonic reorganizations. Among the most compelling evidence in support of a “plume-push” mechanism is the apparent coincidence between eruption of the Deccan flood basalts around 67–64 Ma and a short-lived increase in Indian
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Oxidative conditions can lead to exceptional preservation through phosphatization Geology (IF 4.768) Pub Date : 2020-12-01 Pierre Gueriau, Sylvain Bernard, François Farges, Cristian Mocuta, Didier B. Dutheil, Thierry Adatte, Brahimsamba Bomou, Marie Godet, Dominique Thiaudière, Sylvain Charbonnier, Loïc Bertrand
Exceptional preservation through phosphatization is primarily controlled by a reduction in pH, favoring the precipitation of apatite over that of calcite. Laboratory experiments have suggested that phosphatization results from anoxic decay. Here we report results of the fine-scale mineralogical characterization of Cretaceous phosphatized fossils of teleost fishes and crustaceans from the Jebel oum
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Precipitation and aridity constraints from paleolakes on early Mars Geology (IF 4.768) Pub Date : 2020-12-01 Gaia Stucky de Quay, Timothy A. Goudge, Caleb I. Fassett
The ancient climate of Mars remains an enigma despite the abundance of in situ and remote-sensing data revealing hydrological activity in the past. The crux of this debate—informed by geomorphic studies, chemical alteration observations, and numerical climate models—is the amount, distribution, and nature of surface water and precipitation (i.e., rain vs. snow). Here, we combined measurements of 96
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Late Miocene contourite channel system reveals intermittent overflow behavior Geology (IF 4.768) Pub Date : 2020-12-01 Wouter de Weger, F. Javier Hernández-Molina, Rachel Flecker, Francisco J. Sierro, Domenico Chiarella, Wout Krijgsman, M. Amine Manar
Paleoceanographic information from submarine overflows in the vicinity of oceanic gateways is of major importance for resolving the role of ocean circulation in modulating Earth’s climate. Earth system models are currently the favored way to study the impact of gateways on global-scale processes, but studies on overflow-related deposits are more suitable to understand the detailed changes. Such deposits
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Ocean acidification during the early Toarcian extinction event: Evidence from boron isotopes in brachiopods Geology (IF 4.768) Pub Date : 2020-12-01 Tamás Müller, Hana Jurikova, Marcus Gutjahr, Adam Tomašových, Jan Schlögl, Volker Liebetrau, Luís v. Duarte, Rastislav Milovský, Guillaume Suan, Emanuela Mattioli, Bernard Pittet, Anton Eisenhauer
The loss of carbonate production during the Toarcian Oceanic Anoxic Event (T-OAE, ca. 183 Ma) is hypothesized to have been at least partly triggered by ocean acidification linked to magmatism from the Karoo-Ferrar large igneous province (southern Africa and Antarctica). However, the dynamics of acidification have never been directly quantified across the T-OAE. Here, we present the first record of
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Breadcrust bubbles: Ash particles recording post-fragmentation brittle-ductile deformation Geology (IF 4.768) Pub Date : 2020-12-01 Steven L. Quane, Benjamin J. Andrews
Breadcrust bubbles are a previously undescribed pyroclast providing unique insights into post-fragmentation conduit dynamics. We describe these particles from the ca. 7 Ma Rattlesnake Tuff deposits (Oregon, USA) and ca. 15 ka deposits at Laguna del Maule (Chile). The clasts comprise discrete, ∼1-mm-diameter, fully intact hollow spheroids composed of high-silica rhyolite glass with a series of cross-cutting
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Simultaneous Middle Pleistocene eruption of three widespread tholeiitic basalts in northern California (USA): Insights into crustal magma transport in an actively extending back arc Geology (IF 4.768) Pub Date : 2020-12-01 Drew T. Downs, Duane E. Champion, Patrick Muffler, Robert L. Christiansen, Michael A. Clynne, Andrew T. Calvert
Mapping and chronology are central to understanding spatiotemporal volcanic trends in diverse tectonic settings. The Cascades back arc in northern California (USA) hosts abundant lava flows and normal faults, but tholeiitic basalts older than 200 ka are difficult to discriminate by classic mapping methods. Paleomagnetism and chemistry offer independent means of correlating basalts, including the Tennant
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Fossilized reproductive modes reveal a protistan affinity of Chitinozoa Geology (IF 4.768) Pub Date : 2020-12-01 Yan Liang, Olle Hints, Peng Tang, Chenyang Cai, Daniel Goldman, Jaak Nõlvak, Erik Tihelka, Ke Pang, Joseph Bernardo, Wenhui Wang
Reproduction is a key aspect of evolution, but the process is rarely preserved in the fossil record. Organisms fortuitously preserved undergoing reproduction provide an exceptional window illuminating the biology of extinct taxa, especially those with unknown phylogenetic position. Here we report exceptional specimens of chitinozoans (enigmatic Paleozoic organic-walled microfossils) preserved as “test-in-test”
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Syncing fault rock clocks: Direct comparison of U-Pb carbonate and K-Ar illite fault dating methods Geology (IF 4.768) Pub Date : 2020-12-01 C.M. Mottram, D.A. Kellett, T. Barresi, H. Zwingmann, M. Friend, A. Todd, J.B. Percival
The timing of slip on brittle faults in Earth’s upper crust is difficult to constrain, and direct radiometric dating of fault-generated materials is the most explicit approach. Here we make a direct comparison between K-Ar dating of fault gouge clay (authigenic illite) and U-Pb dating of carbonate slickenfibers and veins from the same fault. We have dated fault generated materials from the Big Creek
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Deep and extensive meltwater system beneath the former Eurasian Ice Sheet in the Kara Sea Geology (IF 4.768) 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
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Geochemical evidence for an orogenic plateau in the southern U.S. and northern Mexican Cordillera during the Laramide orogeny Geology (IF 4.768) 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
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Metasomatized lithospheric mantle for Mesozoic giant gold deposits in the North China craton Geology (IF 4.768) 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
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Coupled supercontinent–mantle plume events evidenced by oceanic plume record Geology (IF 4.768) 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
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Regional and global signals in seawater δ 18 O records across the mid-Pleistocene transition Geology (IF 4.768) 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
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Carbonate collapse and the late Paleozoic ice age marine biodiversity crisis Geology (IF 4.768) 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
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X-ray computed tomography reveals that grain protrusion controls critical shear stress for entrainment of fluvial gravels Geology (IF 4.768) 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
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Postglacial erosion of bedrock surfaces and deglaciation timing: New insights from the Mont Blanc massif (western Alps) Geology (IF 4.768) 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
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Explosive interaction of impact melt and seawater following the Chicxulub impact event Geology (IF 4.768) 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
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Recent inversion of the Tyrrhenian Basin Geology (IF 4.768) 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
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The role of impacts on Archaean tectonics Geology (IF 4.768) 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
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Plate-tectonic processes at ca. 2.0 Ga: Evidence from >600 km of plate convergence Geology (IF 4.768) 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
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Icequake streaks linked to potential mega-scale glacial lineations beneath an Antarctic ice stream Geology (IF 4.768) 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
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Lithosphere thickness controls continental basalt compositions: An illustration using Cenozoic basalts from eastern China Geology (IF 4.768) 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
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ERRATUM: Why do large, deep rivers have low-angle dune beds? Geology (IF 4.768) 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.
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Do impacts impact global tectonics? Geology (IF 4.768) 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
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Differences in channel and hillslope geometry record a migrating uplift wave at the Mendocino triple junction, California, USA Geology (IF 4.768) 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
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Forming sulfate- and REE-rich fluids in the presence of quartz Geology (IF 4.768) 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
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Sea level, carbonate mineralogy, and early diagenesis controlled δ 13 C records in Upper Ordovician carbonates Geology (IF 4.768) 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
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Dry sediment loading of headwater channels fuels post-wildfire debris flows in bedrock landscapes Geology (IF 4.768) 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
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Foundered lithospheric segments dropped into the mantle transition zone beneath southern California, USA Geology (IF 4.768) 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
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How shear helps lava to flow Geology (IF 4.768) 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
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