Showing papers in "The Journal of Geology in 2018"
TL;DR: In this article, the authors investigated evidence of biomass burning in global ice records, and here they continue to test the hypothesis that an impact event at the Younger Dryas boundary (YDB) caused an anomalously intense episode of burning at ∼12.8 ka on a multicontinental scale.
Abstract: Part 1 of this study investigated evidence of biomass burning in global ice records, and here we continue to test the hypothesis that an impact event at the Younger Dryas boundary (YDB) caused an anomalously intense episode of biomass burning at ∼12.8 ka on a multicontinental scale (North and South America, Europe, and Asia). Quantitative analyses of charcoal and soot records from 152 lakes, marine cores, and terrestrial sequences reveal a major peak in biomass burning at the Younger Dryas (YD) onset that appears to be the highest during the latest Quaternary. For the Cretaceous-Tertiary boundary (K-Pg) impact event, concentrations of soot were previously utilized to estimate the global amount of biomass burned, and similar measurements suggest that wildfires at the YD onset rapidly consumed ∼10 million km2 of Earth’s surface, or ∼9% of Earth’s biomass, considerably more than for the K-Pg impact. Bayesian analyses and age regressions demonstrate that ages for YDB peaks in charcoal and soot across ...
51 citations
TL;DR: The Younger Dryas boundary (YDB) cosmic-impact hypothesis is based on considerable evidence that Earth collided with fragments of a disintegrating ≥100-km-diameter comet, the remnants of which persist within the inner solar system ∼12,800 y later.
Abstract: The Younger Dryas boundary (YDB) cosmic-impact hypothesis is based on considerable evidence that Earth collided with fragments of a disintegrating ≥100-km-diameter comet, the remnants of which persist within the inner solar system ∼12,800 y later Evidence suggests that the YDB cosmic impact triggered an “impact winter” and the subsequent Younger Dryas (YD) climate episode, biomass burning, late Pleistocene megafaunal extinctions, and human cultural shifts and population declines The cosmic impact deposited anomalously high concentrations of platinum over much of the Northern Hemisphere, as recorded at 26 YDB sites at the YD onset, including the Greenland Ice Sheet Project 2 ice core, in which platinum deposition spans ∼21 y (∼12,836–12,815 cal BP) The YD onset also exhibits increased dust concentrations, synchronous with the onset of a remarkably high peak in ammonium, a biomass-burning aerosol In four ice-core sequences from Greenland, Antarctica, and Russia, similar anomalous peaks in other
49 citations
TL;DR: The Singhbhum craton is one of five Archean cratons constituting the Indian subcontinent and consists of four major lithotectonic units with broadly defined ages from Eoarchean to Neoarchea as discussed by the authors.
Abstract: The Singhbhum craton is one of five Archean cratons constituting the Indian subcontinent. It consists of four major lithotectonic units with broadly defined ages from Eoarchean to Neoarchea...
43 citations
TL;DR: The Yagan and Zhusileng-Hangwula arcs (YZHAs) in western Inner Mongolia in China occupy the position between the South Tianshan suture zone to the west and the Solonker Suture Zone to the east as mentioned in this paper.
Abstract: Situated between the South Tianshan suture zone to the west and the Solonker suture zone to the east, the Yagan and Zhusileng-Hangwula arcs (YZHAs) in western Inner Mongolia in China occupy...
35 citations
TL;DR: The northwestern margin of the Hetao Graben, North China, is bounded by a pronounced 160 km-long Langshan Piedmont fault (LPF) as mentioned in this paper.
Abstract: The northwestern margin of the Hetao Graben, North China, is bounded by a pronounced 160-km-long Langshan Piedmont fault (LPF). The kinematics and recent tectonic activity of this rift-bord...
28 citations
TL;DR: In this article, the authors proposed a method for pH measurement on soils, which requires friable material, thereby making it difficult to obtain pH measurements on soils with high friability.
Abstract: Soil pH is essential for understanding weathering, nutrient availability, and biological-edaphic relationships. However, standard pH measurement on soils requires friable material, thereby ...
24 citations
TL;DR: The monsoonal paleoclimate of India has been critical for understanding the tectonic history of Himalayan and Tibetan uplift over the past 60 My as mentioned in this paper, which has been shown to be the case in the past 20 My.
Abstract: The monsoonal paleoclimate of India has been critical for understanding the tectonic history of Himalayan and Tibetan uplift over the past 60 My. Monsoonal circulation in deep time has been...
22 citations
TL;DR: The Younger Dryas (YD) climate episode (∼12,850-11,650 calendar years before present [cal BP]) is an event recorded widely across the Northern Hemisphere as mentioned in this paper.
Abstract: The Younger Dryas (YD) climate episode (∼12,850–11,650 calendar years before present [cal BP]) is an event recorded widely across the Northern Hemisphere. We conducted multiple analyses at ...
21 citations
TL;DR: In this paper, the authors propose that the litharenite is correlative with the Middle Run Formation in Ohio and was deposited in an evolving late Grenville rift/foreland basin adjacent to the exhuming Grenville orogen.
Abstract: Basement cores from two wells drilled west and east of the Grenville front consist of feldspathic litharenite and granitic orthogneiss, respectively. Detrital zircon U-Pb ages for the litharenite define a broad dominant U-Pb age mode at ca. 1115 Ma. The dominant mode matches that for the type locality of the Middle Run Formation in the Ohio subsurface and is interpreted to consist of detrital zircons sourced from East Continent Rift volcanic sources (ca. 1100 Ma) and Grenville Shawinigan granites/gneisses (1120–1180 Ma). The youngest detrital zircon ages (ca. 1020 Ma) require a maximum depositional age that is at least 70 My younger than the time of Midcontinent and East Continent rifting and magmatism. We propose that the litharenite is correlative with the Middle Run Formation in Ohio and was deposited in an evolving late Grenville rift/foreland basin adjacent to the exhuming Grenville orogen. Zircon U-Pb secondary-ion mass spectrometry ages from orthogneiss define a discordant array with interc...
21 citations
TL;DR: A newly determined age (1647±18 Ma) for a rare magmatic zircon extracted from a very fine-grained felsic ash bed in the type area of the Porcellanite Formation, Vindhyan Supergrou... as discussed by the authors.
Abstract: We report a newly determined age (1647±18 Ma) for a rare magmatic zircon extracted from a very fine-grained felsic ash bed in the type area of the Porcellanite Formation, Vindhyan Supergrou...
21 citations
TL;DR: In this paper, detrital zircons from the Sibao and Danzhou groups have generally similar age populations, with three major peaks at 2000-1550, 1000-880, and 850-830 (760) Ma and one minor at 2600-2400 Ma.
Abstract: The Jiangnan Orogen, located at the southeastern margin of the Yangtze Block, South China, records the complete history of assembly and evolution between the Yangtze and Cathaysia blocks. Neoproterozoic sedimentary sequences are widespread in the Jiangnan Orogen, with a regional angular unconformity separating the Sibao and Danzhou groups. U-Pb geochronology and Lu-Hf isotope analyses were carried out on detrital zircons across this unconformity and also the associated granites in the western Jiangnan Orogen in this study. Our new results, combined with previous data, indicate that the Sibao and Danzhou groups were deposited at 860–832 and 803–764 Ma, respectively. Thus, this unconformity was constrained to be 832–803 Ma. Detrital zircons from the Sibao and Danzhou groups have generally similar age populations, with three major peaks at 2000–1550, 1000–880, and 850–830 (760) Ma and one minor at 2600–2400 Ma. The most important generation of juvenile crust appears to have occurred at 2600–2400 Ma. ...
TL;DR: The Qinling orogenic belt in central China resulted from the final collision of the North China and South China blocks in the Triassic. Early Mesozoic granitoids are widespread in the Qinli...
Abstract: The Qinling orogenic belt in central China resulted from the final collision of the North China and South China blocks in the Triassic. Early Mesozoic granitoids are widespread in the Qinli...
TL;DR: In this article, new geochronological and whole-rock geochemical data for the Dongqiao intrusive rocks were presented, and six samples yielded zircon U-Pb ages of 111-115 Ma.
Abstract: We present here new geochronological and whole-rock geochemical data for the Dongqiao intrusive rocks. Six samples yield zircon U-Pb ages of 111–115 Ma, indicating that the Dongqiao graniti...
TL;DR: The Gypsum Spring and Sundance Formations in Wyoming and South Dakota, United States, preserve seven thi... well-exposed Middle to Upper Jurassic (Bajocian to Oxfordian; ∼170-155 Ma) strata.
Abstract: Well-exposed Middle to Upper Jurassic (Bajocian to Oxfordian; ∼170–155 Ma) strata of the Gypsum Spring and Sundance Formations in Wyoming and South Dakota, United States, preserve seven thi...
TL;DR: A paleosol beneath the Upper Cambrian Mount Simon Sandstone in Wisconsin provides an opportunity to evaluate the characteristics of Cambrian weathering in a subtropical climate as discussed by the authors.
Abstract: A paleosol beneath the Upper Cambrian Mount Simon Sandstone in Wisconsin provides an opportunity to evaluate the characteristics of Cambrian weathering in a subtropical climate, having been...
TL;DR: In this article, microscopic investigations of horizons in a surface paleosol, part of a pedostratigraphic stack of tills at New Mountain, Antarctica, dated to the middle Miocene climatic optimum were performed.
Abstract: Detailed microscopic investigations of horizons in a surface paleosol, part of a pedostratigraphic stack of tills at New Mountain, Antarctica, dated to the middle Miocene climatic optimum e...
TL;DR: The origin and distribution of mudstone clast breccia bed deposits of the middle McMurray Formation responded to a range of current flow conditions associated with down-channel migrations by kilometers-long point bars, which accumulated as reservoirs of the Cretaceous Athabasca oil sands in northern Alberta as discussed by the authors.
Abstract: The origin and distribution of mudstone clast breccia bed deposits of the middle McMurray Formation responded to a range of current flow conditions associated with downchannel migrations by kilometers-long point bars, which accumulated as reservoirs of the Cretaceous Athabasca oil sands in northern Alberta. Fabrics consisting of dispersed clast entrainments within centimeters- to decimeters-thick stratified sand beds accumulated as grain flows and small-scale debris flows that filled shallow, flat-bottomed troughs during bed erosion on the point bar. Most low-density clast dispersals were sourced by eroded mudstone beds exposed along the bar bed surfaces. Clast-laden debris flows, 1–2 m thick, filled deeper troughs on the point bar, often as overlying flow-surge deposits, resulting in internal erosional surfaces within the breccia bed. Elsewhere, voluminous debris flows were sourced by undercut older channel walls that eroded mud-dominated counter point bar beds or exhumed lower McMurray floodplai...
TL;DR: The mid-Paleozoic alkalic plutons and associated volcanic rocks in a northeast-trending belt transecting the southeastern New England segment of “West” Avalonia are well known for their anoroge as discussed by the authors.
Abstract: Mid-Paleozoic alkalic plutons and associated volcanic rocks in a northeast-trending belt transecting the southeastern New England segment of “West” Avalonia are well known for their anoroge...
TL;DR: Two new chemical abrasion thermal ionization mass spectrometry U/Pb dates established the age of the top of the Brushy Basin Member, Morrison Formation, at Flat Top.
Abstract: Two new chemical abrasion thermal ionization mass spectrometry U/Pb dates establish the age of the top of the Brushy Basin Member, Morrison Formation, at Flat Top (also known as Terrace Hil...
TL;DR: The present metamorphic crystalline basement of the South China Block was formed largely as a result of the early Paleozoic orogeny, which affected large areas of this contine...
Abstract: The present metamorphic crystalline basement of the South China Block was formed largely as a result of the early Paleozoic (∼460–410 Ma) orogeny, which affected large areas of this contine...
TL;DR: The recognition of the power of rivers to carve landscapes transformed geology and geomorphology in the late nineteenth century and wide acceptance of this concept was then known as "fluvialism" as mentioned in this paper.
Abstract: Recognition of the power of rivers to carve landscapes transformed geology and geomorphology in the late nineteenth century Wide acceptance of this concept—then known as “fluvialism”—owes
TL;DR: The history of exhumation and denudation of the Cenozoic St Elias orogen is stored in the sediments of the Miocene to Holocene Surveyor Fan, Gulf of Alaska as mentioned in this paper.
Abstract: The history of exhumation and denudation of the Cenozoic St Elias orogen is stored in the sediments of the Miocene to Holocene Surveyor Fan, Gulf of Alaska The orogeny of the mountain bel
TL;DR: The authors presented new zircon U-Pb isotopic data for volcanic rocks from deformed metavolcanic-sedimentary successions of the widespread Ross Supergroup in the Queen Maud Mountains, Antarctica.
Abstract: We present new zircon U-Pb isotopic data for volcanic rocks from deformed metavolcanic-sedimentary successions of the widespread Ross Supergroup in the Queen Maud Mountains, Antarctica. Zir...
TL;DR: In this paper, the many new occurrences reported in the literature of ultramafic rocks that have phlogopite as a major constituent and do not fall into the categories of kimberlites, lamp...
Abstract: In recent years, the many new occurrences reported in the literature of ultramafic rocks that have phlogopite as a major constituent and do not fall into the categories of kimberlites, lamp...
TL;DR: The tonalite-trondhjemite-granodiorite (TTG) suite of plutonic rocks that is the backbone of the TTG suite as mentioned in this paper.
Abstract: Dehydration (fluid-absent) melting of garnetiferous amphibolite is now widely believed to have given rise to the tonalite-trondhjemite-granodiorite (TTG) suite of plutonic rocks that is the...
TL;DR: In this article, a refinements in nomenclature with an emphasis on member-level organization of Hirnantian strata from Norway's Oslo region provide a useful way to grasp depositional processes recorded in the records.
Abstract: Recent refinements in nomenclature with an emphasis on member-level organization of Hirnantian strata from Norway’s Oslo region provide a useful way to grasp depositional processes recorded...
TL;DR: In this article, the distribution of densely packed brachiopod deposits tends to be determined by physical processes that operate within the timescale of deposition of a single lithofacies, producing skeletal concentrations that are mostly associated with beddin.
Abstract: Nondepositional hiatuses tend to favor the dense accumulation of skeletal material because they are associated with minimal sedimentary dilution of bioclast input. However, bioclast durability or production must be sufficient to counterbalance the rigors of delayed burial and especially the repeated events of seafloor exposure and reworking that bioclasts can experience during sedimentary bypass or starvation associated with the formation of hiatuses. Detailed field investigations of skeletal concentrations in Middle–Upper Devonian brachiopod-rich carbonate stratigraphic records from the continental margin of Nevada and the cratonic interior of Iowa reveal a surprising lack of abundant skeletal material mantling major stratigraphic discontinuities. Rather, the distribution of densely packed brachiopod deposits tends to be determined by physical processes that operate within the timescale of deposition of a single lithofacies, producing skeletal concentrations that are mostly associated with beddin...
TL;DR: In this article, the occurrence of both magnesian (149−131 Ma) and ferroan (1.1 Ma) was investigated in the northwest Zhejiang Province (NWZJ).
Abstract: Northwest Zhejiang Province (NWZJ) is located in the southeastern Lower Yangtze River Belt, southeastern China. Here we document the occurrence of both magnesian (149–131 Ma) and ferroan (1...
TL;DR: The western margin of the Yangtze block is characterized by numerous felsic intrusions and many mafic-ultramafic plutons that record the lithospheric thermal state of South China during the...
Abstract: The western margin of the Yangtze Block is characterized by numerous felsic intrusions and many mafic-ultramafic plutons that record the lithospheric thermal state of South China during the...
TL;DR: The Egrigoz and Koyunoba monzogranites in western Turkey contain igneous enclaves that provide important information concerning the magma-forming processes and their petrogenetic origin in...
Abstract: The Egrigoz and Koyunoba monzogranites in western Turkey contain igneous enclaves that provide important information concerning the magma-forming processes and their petrogenetic origin in ...