Publications by authors named "Paul R Renne"

20 Publications

  • Page 1 of 1

Reconciling early Deccan Traps CO outgassing and pre-KPB global climate.

Proc Natl Acad Sci U S A 2021 Apr;118(14)

Department of Biodiversity, Earth and Environmental Science, Drexel University, Philadelphia, PA 19104.

A 2 to 4 °C warming episode, known as the Latest Maastrichtian warming event (LMWE), preceded the Cretaceous-Paleogene boundary (KPB) mass extinction at 66.05 ± 0.08 Ma and has been linked with the onset of voluminous Deccan Traps volcanism. Here, we use direct measurements of melt-inclusion CO concentrations and trace-element proxies for CO to test the hypothesis that early Deccan magmatism triggered this warming interval. We report CO concentrations from NanoSIMS and Raman spectroscopic analyses of melt-inclusion glass and vapor bubbles hosted in magnesian olivines from pre-KPB Deccan primitive basalts. Reconstructed melt-inclusion CO concentrations range up to 0.23 to 1.2 wt% CO for lavas from the Saurashtra Peninsula and the Thakurvadi Formation in the Western Ghats region. Trace-element proxies for CO concentration (Ba and Nb) yield estimates of initial melt concentrations of 0.4 to 1.3 wt% CO prior to degassing. Our data imply carbon saturation and degassing of Deccan magmas initiated at high pressures near the Moho or in the lower crust. Furthermore, we find that the earliest Deccan magmas were more CO rich, which we hypothesize facilitated more efficient flushing and outgassing from intrusive magmas. Based on carbon cycle modeling and estimates of preserved lava volumes for pre-KPB lavas, we find that volcanic CO outgassing alone remains insufficient to account for the magnitude of the observed latest Maastrichtian warming. However, accounting for intrusive outgassing can reconcile early carbon-rich Deccan Traps outgassing with observed changes in climate and atmospheric pCO.
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http://dx.doi.org/10.1073/pnas.2007797118DOI Listing
April 2021

Boutique neutrons advance Ar/Ar geochronology.

Sci Adv 2019 Sep 11;5(9):eaaw5526. Epub 2019 Sep 11.

Department of Nuclear Engineering, University of California, Berkeley, Berkeley, CA 94720, USA.

We designed and tested a compact deuteron-deuteron fusion neutron generator for application to Ar/Ar geochronology. The nearly monoenergetic neutrons produced for sample irradiation are anticipated to provide several advantages compared with conventional fission spectrum neutrons: Reduction of collateral nuclear reactions increases age accuracy and precision. Irradiation parameters within the neutron generator are more controllable compared with fission reactors. Confidence in the prediction of recoil energies is improved, and their likely reduction potentially broadens applicability of the dating method to fine-grained materials without vacuum encapsulation. Resolution of variation in the K(n,p)Ar neutron capture cross section at 1.3 to 3.2 MeV and discovery of a strong resonance at ~2.4 MeV illuminate future pathways to improve the technique for Ar/Ar dating.
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http://dx.doi.org/10.1126/sciadv.aaw5526DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6739110PMC
September 2019

The eruptive tempo of Deccan volcanism in relation to the Cretaceous-Paleogene boundary.

Science 2019 02;363(6429):866-870

Department of Earth and Planetary Science, University of California, Berkeley, 307 McCone Hall, Berkeley, CA 94720-4767, USA.

Late Cretaceous records of environmental change suggest that Deccan Traps (DT) volcanism contributed to the Cretaceous-Paleogene boundary (KPB) ecosystem crisis. However, testing this hypothesis requires identification of the KPB in the DT. We constrain the location of the KPB with high-precision argon-40/argon-39 data to be coincident with changes in the magmatic plumbing system. We also found that the DT did not erupt in three discrete large pulses and that >90% of DT volume erupted in <1 million years, with ~75% emplaced post-KPB. Late Cretaceous records of climate change coincide temporally with the eruption of the smallest DT phases, suggesting that either the release of climate-modifying gases is not directly related to eruptive volume or DT volcanism was not the source of Late Cretaceous climate change.
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http://dx.doi.org/10.1126/science.aav1446DOI Listing
February 2019

State shift in Deccan volcanism at the Cretaceous-Paleogene boundary, possibly induced by impact.

Science 2015 Oct;350(6256):76-8

Department of Earth Sciences, Indian Institute of Technology Bombay, Powai, Mumbai 400 076, India.

Bolide impact and flood volcanism compete as leading candidates for the cause of terminal-Cretaceous mass extinctions. High-precision (40)Ar/(39)Ar data indicate that these two mechanisms may be genetically related, and neither can be considered in isolation. The existing Deccan Traps magmatic system underwent a state shift approximately coincident with the Chicxulub impact and the terminal-Cretaceous mass extinctions, after which ~70% of the Traps' total volume was extruded in more massive and more episodic eruptions. Initiation of this new regime occurred within ~50,000 years of the impact, which is consistent with transient effects of impact-induced seismic energy. Postextinction recovery of marine ecosystems was probably suppressed until after the accelerated volcanism waned.
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http://dx.doi.org/10.1126/science.aac7549DOI Listing
October 2015

Time scales of critical events around the Cretaceous-Paleogene boundary.

Science 2013 Feb;339(6120):684-7

Berkeley Geochronology Center, 2455 Ridge Road, Berkeley, CA 94709, USA.

Mass extinctions manifest in Earth's geologic record were turning points in biotic evolution. We present (40)Ar/(39)Ar data that establish synchrony between the Cretaceous-Paleogene boundary and associated mass extinctions with the Chicxulub bolide impact to within 32,000 years. Perturbation of the atmospheric carbon cycle at the boundary likely lasted less than 5000 years, exhibiting a recovery time scale two to three orders of magnitude shorter than that of the major ocean basins. Low-diversity mammalian fauna in the western Williston Basin persisted for as little as 20,000 years after the impact. The Chicxulub impact likely triggered a state shift of ecosystems already under near-critical stress.
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http://dx.doi.org/10.1126/science.1230492DOI Listing
February 2013

The characteristics and chronology of the earliest Acheulean at Konso, Ethiopia.

Proc Natl Acad Sci U S A 2013 Jan 28;110(5):1584-91. Epub 2013 Jan 28.

Association for Research and Conservation of Culture (A.R.C.C.), Awassa, Ethiopia.

The Acheulean technological tradition, characterized by a large (>10 cm) flake-based component, represents a significant technological advance over the Oldowan. Although stone tool assemblages attributed to the Acheulean have been reported from as early as circa 1.6-1.75 Ma, the characteristics of these earliest occurrences and comparisons with later assemblages have not been reported in detail. Here, we provide a newly established chronometric calibration for the Acheulean assemblages of the Konso Formation, southern Ethiopia, which span the time period ∼1.75 to <1.0 Ma. The earliest Konso Acheulean is chronologically indistinguishable from the assemblage recently published as the world's earliest with an age of ∼1.75 Ma at Kokiselei, west of Lake Turkana, Kenya. This Konso assemblage is characterized by a combination of large picks and crude bifaces/unifaces made predominantly on large flake blanks. An increase in the number of flake scars was observed within the Konso Formation handaxe assemblages through time, but this was less so with picks. The Konso evidence suggests that both picks and handaxes were essential components of the Acheulean from its initial stages and that the two probably differed in function. The temporal refinement seen, especially in the handaxe forms at Konso, implies enhanced function through time, perhaps in processing carcasses with long and stable cutting edges. The documentation of the earliest Acheulean at ∼1.75 Ma in both northern Kenya and southern Ethiopia suggests that behavioral novelties were being established in a regional scale at that time, paralleling the emergence of Homo erectus-like hominid morphology.
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http://dx.doi.org/10.1073/pnas.1221285110DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3562807PMC
January 2013

Geoscience: Fossil raindrops and ancient air.

Nature 2012 Mar 28;484(7394):322-4. Epub 2012 Mar 28.

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http://dx.doi.org/10.1038/nature11036DOI Listing
March 2012

A chronological framework for a long and persistent archaeological record: Melka Kunture, Ethiopia.

J Hum Evol 2012 Jan 15;62(1):104-15. Epub 2011 Dec 15.

Department of Earth & Planetary Science, University of California, Berkeley, CA 94720, USA.

New (40)Ar/(39)Ar geochronological data for several volcanic ash horizons from Melka Kunture, Ethiopia, allow for significantly more precise age constraints to be placed upon the lithostratigraphy, archaeology and paleontology from this long record. Ashes from the Melka Kunture Formation at Gombore yielded the most reliable age constraints, from 1.393 ± 0.162 Ma(2) (millions of years ago) near the base of the section to 0.709 ± 0.013 Ma near the top. Dating the Garba section proved more problematic, but the base of the section, which contains numerous Oldowan obsidian artifacts, may be >1.719 ± 0.199 Ma, while the top is securely dated to 0.869 ± 0.020 Ma. The large ignimbrite from the Kella Formation at Kella and Melka Garba is dated to 1.262 ± 0.034 Ma and pre-dates Acheulean artifacts in the area. The Gombore II site, which has yielded two Homo skull fragments, 'twisted bifaces,' and a preserved butchery site, is now constrained between 0.875 ± 0.010 Ma and 0.709 ± 0.013 Ma. Additional ashes from these and other sites further constrain the timing of deposition throughout the section. Integration with previously published magnetostratigraphy has allowed for the first time a relatively complete, reliable timeline for the deposition of sediments, environmental changes, archaeology, and paleontology at Melka Kunture.
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http://dx.doi.org/10.1016/j.jhevol.2011.10.007DOI Listing
January 2012

A basal dinosaur from the dawn of the dinosaur era in southwestern Pangaea.

Science 2011 Jan;331(6014):206-10

Instituto y Museo de Ciencias Naturales, Universidad Nacional de San Juan, San Juan 5400, Argentina.

Upper Triassic rocks in northwestern Argentina preserve the most complete record of dinosaurs before their rise to dominance in the Early Jurassic. Here, we describe a previously unidentified basal theropod, reassess its contemporary Eoraptor as a basal sauropodomorph, divide the faunal record of the Ischigualasto Formation with biozones, and bracket the formation with (40)Ar/(39)Ar ages. Some 230 million years ago in the Late Triassic (mid Carnian), the earliest dinosaurs were the dominant terrestrial carnivores and small herbivores in southwestern Pangaea. The extinction of nondinosaurian herbivores is sequential and is not linked to an increase in dinosaurian diversity, which weakens the predominant scenario for dinosaurian ascendancy as opportunistic replacement.
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http://dx.doi.org/10.1126/science.1198467DOI Listing
January 2011

The geological, isotopic, botanical, invertebrate, and lower vertebrate surroundings of Ardipithecus ramidus.

Science 2009 Oct;326(5949):65e1-5

Earth Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.

Sediments containing Ardipithecus ramidus were deposited 4.4 million years ago on an alluvial floodplain in Ethiopia's western Afar rift. The Lower Aramis Member hominid-bearing unit, now exposed across a > 9-kilometer structural arc, is sandwiched between two volcanic tuffs that have nearly identical 40Ar/39Ar ages. Geological data presented here, along with floral, invertebrate, and vertebrate paleontological and taphonomic evidence associated with the hominids, suggest that they occupied a wooded biotope over the western three-fourths of the paleotransect. Phytoliths and oxygen and carbon stable isotopes of pedogenic carbonates provide evidence of humid cool woodlands with a grassy substrate.
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http://dx.doi.org/10.1126/science.1175817DOI Listing
October 2009

Asa Issie, Aramis and the origin of Australopithecus.

Nature 2006 Apr;440(7086):883-9

Human Evolution Research Center, Museum of Vertebrate Zoology, 3101 Valley Life Sciences Building, University of California at Berkeley, Berkeley, California 94720, USA.

The origin of Australopithecus, the genus widely interpreted as ancestral to Homo, is a central problem in human evolutionary studies. Australopithecus species differ markedly from extant African apes and candidate ancestral hominids such as Ardipithecus, Orrorin and Sahelanthropus. The earliest described Australopithecus species is Au. anamensis, the probable chronospecies ancestor of Au. afarensis. Here we describe newly discovered fossils from the Middle Awash study area that extend the known Au. anamensis range into northeastern Ethiopia. The new fossils are from chronometrically controlled stratigraphic sequences and date to about 4.1-4.2 million years ago. They include diagnostic craniodental remains, the largest hominid canine yet recovered, and the earliest Australopithecus femur. These new fossils are sampled from a woodland context. Temporal and anatomical intermediacy between Ar. ramidus and Au. afarensis suggest a relatively rapid shift from Ardipithecus to Australopithecus in this region of Africa, involving either replacement or accelerated phyletic evolution.
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http://dx.doi.org/10.1038/nature04629DOI Listing
April 2006

Geochronology: age of Mexican ash with alleged 'footprints'.

Nature 2005 Dec;438(7068):E7-8

Berkeley Geochronology Center, Berkeley, California 94709, USA.

A report of human footprints preserved in 40,000-year-old volcanic ash near Puebla, Mexico (http://www.royalsoc.ac.uk/exhibit.asp?id=3616&tip=1), was the subject of a press conference that stirred international media attention. If the claims (http://www.mexicanfootprints.co.uk) of Gonzalez et al. are valid, prevailing theories about the timing of human migration into the Americas would need significant revision. Here we show by 40Ar/39Ar dating and corroborating palaeomagnetic data that the basaltic tuff on which the purported footprints are found is 1.30+/-0.03 million years old. We conclude that either hominid migration into the Americas occurred very much earlier than previously believed, or that the features in question were not made by humans on recently erupted ash.
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http://dx.doi.org/10.1038/nature04425DOI Listing
December 2005

Early Pliocene hominids from Gona, Ethiopia.

Nature 2005 Jan;433(7023):301-5

CRAFT Stone Age Institute, Indiana University, 1392 West Dittemore Road, Gosport, Indiana, 47433-9531, USA.

Comparative biomolecular studies suggest that the last common ancestor of humans and chimpanzees, our closest living relatives, lived during the Late Miocene-Early Pliocene. Fossil evidence of Late Miocene-Early Pliocene hominid evolution is rare and limited to a few sites in Ethiopia, Kenya and Chad. Here we report new Early Pliocene hominid discoveries and their palaeoenvironmental context from the fossiliferous deposits of As Duma, Gona Western Margin (GWM), Afar, Ethiopia. The hominid dental anatomy (occlusal enamel thickness, absolute and relative size of the first and second lower molar crowns, and premolar crown and radicular anatomy) indicates attribution to Ardipithecus ramidus. The combined radioisotopic and palaeomagnetic data suggest an age of between 4.51 and 4.32 million years for the hominid finds at As Duma. Diverse sources of data (sedimentology, faunal composition, ecomorphological variables and stable carbon isotopic evidence from the palaeosols and fossil tooth enamel) indicate that the Early Pliocene As Duma sediments sample a moderate rainfall woodland and woodland/grassland.
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http://dx.doi.org/10.1038/nature03177DOI Listing
January 2005

Application of deuteron-deuteron (D-D) fusion neutrons to 40Ar/39Ar geochronology.

Appl Radiat Isot 2005 Jan;62(1):25-32

Berkeley Geochronology Center, 2455 Ridge Road, Berkeley, CA 94709, USA.

Neutron irradiation of samples for 40Ar/39Ar dating in a 235U fission reactor requires error-producing corrections for the argon isotopes created from Ca, K, and, to a lesser extent, Cl. The fission spectrum includes neutrons with energies above 2-3 MeV, which are not optimal for the 39K(n,p)39Ar reaction. These higher-energy neutrons are responsible for the largest recoil displacements, which may introduce age artifacts in the case of fine-grained samples. Both interference corrections and recoil displacements would be significantly reduced by irradiation with 2.45 MeV neutrons, which are produced by the deuteron-deuteron (D-D) fusion reaction 2H(d,n)3He. A new generation of D-D reactors should yield sufficiently high neutron fluxes (>10(12) n cm(-2)s(-1)) to be useful for 40Ar/39Ar dating. Modeling indicates that irradiation with D-D neutrons would result in scientific benefits of improved accuracy and broader applicability to fine-grained materials. In addition, radiological safety would be improved, while both maintenance and operational costs would be reduced. Thus, development of high-flux D-D fusion reactors is a worthy goal for 40Ar/39Ar geochronology.
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http://dx.doi.org/10.1016/j.apradiso.2004.06.004DOI Listing
January 2005

Age and timing of the Permian mass extinctions: U/Pb dating of closed-system zircons.

Science 2004 Sep;305(5691):1760-3

Berkeley Geochronology Center, 2455 Ridge Road, Berkeley, CA 94709, USA.

The age and timing of the Permian-Triassic mass extinction have been difficult to determine because zircon populations from the type sections are typically affected by pervasive lead loss and contamination by indistinguishable older xenocrysts. Zircons from nine ash beds within the Shangsi and Meishan sections (China), pretreated by annealing followed by partial attack with hydrofluoric acid, result in suites of consistent and concordant uranium/lead (U/Pb) ages, eliminating the effects of lead loss. The U/Pb age of the main pulse of the extinction is 252.6 +/- 0.2 million years, synchronous with the Siberian flood volcanism, and it occurred within the quoted uncertainty.
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http://dx.doi.org/10.1126/science.1101012DOI Listing
September 2004

Stratigraphic, chronological and behavioural contexts of Pleistocene Homo sapiens from Middle Awash, Ethiopia.

Nature 2003 Jun;423(6941):747-52

Department of Anthropology, The University of California, Berkeley, California 94720, USA.

Clarifying the geographic, environmental and behavioural contexts in which the emergence of anatomically modern Homo sapiens occurred has proved difficult, particularly because Africa lacked adequate geochronological, palaeontological and archaeological evidence. The discovery of anatomically modern Homo sapiens fossils at Herto, Ethiopia, changes this. Here we report on stratigraphically associated Late Middle Pleistocene artefacts and fossils from fluvial and lake margin sandstones of the Upper Herto Member of the Bouri Formation, Middle Awash, Afar Rift, Ethiopia. The fossils and artefacts are dated between 160,000 and 154,000 years ago by precise age determinations using the 40Ar/39Ar method. The archaeological assemblages contain elements of both Acheulean and Middle Stone Age technocomplexes. Associated faunal remains indicate repeated, systematic butchery of hippopotamus carcasses. Contemporary adult and juvenile Homo sapiens fossil crania manifest bone modifications indicative of deliberate mortuary practices.
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http://dx.doi.org/10.1038/nature01670DOI Listing
June 2003

Geology. Flood basalts--bigger and badder.

Authors:
Paul R Renne

Science 2002 Jun;296(5574):1812-3

Berkeley Geochronology Center, Berkeley, CA 94709, USA.

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http://dx.doi.org/10.1126/science.1073209DOI Listing
June 2002

Remains of Homo erectus from Bouri, Middle Awash, Ethiopia.

Nature 2002 Mar;416(6878):317-20

Rift Valley Research Service, P.O. Box 5717, Addis Ababa, Ethiopia.

The genesis, evolution and fate of Homo erectus have been explored palaeontologically since the taxon's recognition in the late nineteenth century. Current debate is focused on whether early representatives from Kenya and Georgia should be classified as a separate ancestral species ('H. ergaster'), and whether H. erectus was an exclusively Asian species lineage that went extinct. Lack of resolution of these issues has obscured the place of H. erectus in human evolution. A hominid calvaria and postcranial remains recently recovered from the Dakanihylo Member of the Bouri Formation, Middle Awash, Ethiopia, bear directly on these issues. These approximately 1.0-million-year (Myr)-old Pleistocene sediments contain abundant early Acheulean stone tools and a diverse vertebrate fauna that indicates a predominantly savannah environment. Here we report that the 'Daka' calvaria's metric and morphological attributes centre it firmly within H. erectus. Daka's resemblance to Asian counterparts indicates that the early African and Eurasian fossil hominids represent demes of a widespread palaeospecies. Daka's anatomical intermediacy between earlier and later African fossils provides evidence of evolutionary change. Its temporal and geographic position indicates that African H. erectus was the ancestor of Homo sapiens.
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http://dx.doi.org/10.1038/416317aDOI Listing
March 2002