| 1. |
- Burman, Johan, 1966, et al.
(författare)
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A simplified method of preparing phosphoric acid for stable isotope analyses of carbonates
- 2005
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Ingår i: Rapid Communications in Mass Spectrometry. - : Wiley. - 0951-4198 .- 1097-0231. ; 19:21, s. 3086-3088
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Tidskriftsartikel (refereegranskat)abstract
- In order to produce CO2 for stable isotope analyses (delta(18)O and delta(13)C), carbonate samples are commonly digested in phosphoric acid. The acid recipe here presented is based on phase shifting crystalline orthophosphoric acid of pro-analysis quality to a liquid state through heating, followed by pre-vacuum treatment during a start-up procedure before mass analyses for common acid bath preparation, or adding a small amount of phosphoric pentoxide for single drop equipments, respectively. This methodology results in a final acid concentration of 104%. Copyright (C) 2005 John Wiley & Sons, Ltd.
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| 2. |
- Burman, Johan, 1966, et al.
(författare)
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Periwinkle (Littorina littorea) intrashell delta O-18 and delta C-13 records from the mid-Holocene Limfjord region, Denmark: a new high-resolution palaeoenvironmental proxy approach
- 2005
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Ingår i: Holocene. - : SAGE Publications. - 0959-6836 .- 1477-0911. ; 15:4, s. 567-575
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Tidskriftsartikel (refereegranskat)abstract
- Shells of the common intertidal gastropod Littorina littorea both of recent and mid-Holocene origin were analysed along their growth spirals for seasonally induced variations in stable oxygen and carbon isotope compositions. The subfossil specimens are from the Stone Age kitchen midden in Ertebolle, northern Denmark, dated between 5970 +/- 95 and 5070 +/- 90 BP The recent specimens were collected along a west-east salinity gradient within the Limfjord. A Limfjord mixing line of 0.25 parts per thousand. change in delta(18)O (V-SMOW) for each salinity unit was determined. The recent Littorina periwinkles display a calcite relationship of - 0.22 parts per thousand change in shell delta(18)O per degrees C change in temperature, as derived from the Littorina equilibrium equation (versus V-PDB): delta(18)O((Littorina)) - delta(18)O((water)) = 5.250 - 0.224T (degrees C). By using this linearity together with maximum ('winter') isotopic results, we extracted a Littorina growth stop isotherm equivalent to a temperature of 3.7 +/- 1 degrees C. In order to constrain the climate and salinity in the Limfjord region during the mid-Holocene, we used this regression-derived growth stop isotherm as a boundary condition. The subfossil shells indicate a summer surface-water temperature close to 22 +/- 1 degrees C together with a salinity of 31 +/- 1 PSU. These results suggest a more pronounced water exchange between the central Limfjord and the North Sea during the late Atlantic time, and in terms of temperature they indicate 2-4 degrees C warmer conditions than today.
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| 3. |
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| 4. |
- Schmitz, Birger, et al.
(författare)
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Extraterrestrial chromite in Middle Ordovician marine limestone at Kinnekulle, southern Sweden - Traces of a major asteroid breakup event
- 2006
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Ingår i: Meteoritics & Planetary Science. - 1086-9379. ; 41:3, s. 455-466
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Tidskriftsartikel (refereegranskat)abstract
- The distribution of sediment-dispersed extraterrestrial chromite grains and other Cr-rich spinels (> 63 mu m) has been studied in Middle Ordovician Orthoceratite Limestone from two quarries at Kinnekulle, southern Sweden. In the Thorsberg quarry, all similar to 3.2 m thick sequence of beds previously shown to be rich in fossil meteorites is also rich in sediment-dispersed extraterrestrial chromite grains. Typically, 1-3 grains are found per kilogram of limestone. In the nearby Hallekis quarry, the same beds show similarly high concentrations of extraterrestrial chromite grains, but in samples representing the 9 m downward continuation of the section exposed at this site, only 5 such grains were found in a total of 379 kg of limestone. The extraterrestrial (equilibrated ordinary chondritic) chromite grains call be readily distinguished by a homogeneous and characteristic major element chemistry, including 2.0-3.5 wt% TiO2 and stable V2O3 concentrations close to 0.7 wt%. Terrestrial Cr-rich spinels have a wide compositional range and co-exist with extraterrestrial chromite in some beds. These grains may be derived, for example, from mafic dykes exposed and weathered at the sea floor. Considering lithologic and stratigraphic aspects variations in sedimentation rate cannot explain the dramatic increase in extraterrestrial chromite seen in the upper part of the composite section studied. Instead, the difference may be primarily related to all increase in the ancient flux or extraterrestrial matter to Earth in connection with the disruption of the L chondrite parent body in the asteroid belt at about this time. The coexistence in some beds of high concentrations of chondritic chromite and terrestrial Cr-rich spinels, however, indicates that redistribution of heavy minerals on the sea floor, related to changes in sea level and sea-floor erosion and currents, must also be considered.
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| 5. |
- Boschi, Samuele, et al.
(författare)
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Late Eocene 3He and Ir anomalies associated with ordinary chondritic spinels
- 2017
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Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037. ; 204, s. 205-218
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Tidskriftsartikel (refereegranskat)abstract
- During the late Eocene there was an enigmatic enhancement in the flux of extraterrestrial material to Earth. Evidence comes from sedimentary 3He records indicating an increased flux of interplanetary dust during ca. 2 Myr, as well as two very large impact structures, Popigai (100 km diameter) and Chesapeake Bay (40–85 km), that formed within 10–20 kyr at the peak of the 3He delivery. The Massignano section in Italy has one of the best sedimentary records of these events, including a well-defined 3He record, an Ir-rich ejecta bed related to the Popigai impact event, and two smaller Ir anomalies. Recently we showed that the Popigai ejecta is associated with a significant enrichment of chromite grains (>63 μm) with an H-chondritic elemental composition (17 grains in 100 kg of rock). Most likely these grains are unmelted fragments from the impactor. Slightly higher up (ca. 20 cm) in the section, where a small Ir anomaly possibly related to the Chesapeake Bay impact has been measured, we found a weak enrichment in L-chondritic grains (8 grains in 208 kg of rock). Here we report an extended data set increasing the total amount of sediment dissolved in acid and searched for extraterrestrial chromite grains from 658 to 1168 kg. In altogether 760 kg of background sediment from 17 levels over 14 m of strata outside the interval corresponding to the Popigai and Chesapeake Bay impacts, we only found 2 extraterrestrial chromite grains. Both grains have L-chondritic compositions and were found in a 100 kg sample from the ca. 10.25 m level in the section where the second of the smaller Ir anomalies has been reported. A correlation appears to exist between Ir, 3He and chromite from ordinary chondrites. We also report oxygen three-isotope measurements of the extraterrestrial chromite grains associated with the Popigai ejecta and confirm an H-chondritic composition. The new results strengthen our scenario that the upper Eocene 3He and Ir enrichments originate from the asteroid belt rather than the Oort cloud as originally proposed when the 3He anomaly was discovered. The generally low background concentrations of extraterrestrial chromite through the section speak against any major single asteroid breakup event such as in the mid-Ordovician after the break-up of the L-chondrite parent body. Instead the data reconcile with a small, possibly a factor of 2–3, increase in the flux of extraterrestrial material to Earth, but of both H- and L-chondritic composition. We also report the composition of all the 2310 terrestrial chrome spinel grains recovered, and show that their chemical composition indicates a dominantly regional ophiolitic source. Four anomalous chrome spinel grains with high Ti and V concentrations were found in the Popigai ejecta. These grains originate from Siberian Traps basalts in the Popigai crater at the time of impact.
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| 6. |
- Schmitz, Birger, et al.
(författare)
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The micrometeorite flux to Earth during the Frasnian–Famennian transition reconstructed in the Coumiac GSSP section, France
- 2019
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Ingår i: Earth and Planetary Science Letters. - : Elsevier BV. - 0012-821X. ; 522, s. 234-243
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Tidskriftsartikel (refereegranskat)abstract
- We have reconstructed the distribution of extraterrestrial chrome spinels in a marine limestone section across the Frasnian–Famennian stratotype section at Coumiac in southern France, providing the first insights on the types of micrometeorites and meteorites that fell on Earth at this time. The data can test whether the small cluster of roughly coeval, large impact structures is related to an asteroid breakup and shower with possible bearings also on the late Devonian biodiversity crisis. A total of ∼180 extraterrestrial spinel grains (>32 μm) were recovered from 957 kg of rock. Noble-gas measurements of individual grains show high solar-wind content, implying an origin from decomposed micrometeorites. Element analyses indicate a marked dominance of ordinary chondritic over achondritic grains, similar to the recent flux. The relation between H, L and LL meteorites is ∼29–58–13%, similar to the late Silurian flux, ∼31–63–6%, but different from the distribution, ∼45–45–10%, in the recent and the Cretaceous flux. Our data show no indication of a generally enhanced late Devonian micrometeorite flux that would accompany an asteroid shower. However, in a single limestone bed that formed immediately before the Upper Kellwasser horizon, that represents the main end-Frasnian species-turnover event, we found an enrichment of ∼10 ordinary chondritic grains (>63 μm) per 100 kg of rock, compared to the ∼1–3 grains per 100 kg that characterise background. The anomalously abundant grains are of mixed H, L and LL types and may be related to an enhanced flux of extraterrestrial dust during postulated minima in both the 405 ka and 2.4 Ma Earth-orbit eccentricity cycles at the onset of the Upper Kellwasser event. In the present solar system the dust accretion at Earth is the highest at eccentricity minima because of the spatial distribution of dust bands of the zodiacal cloud. Besides this small grain anomaly the data here and in previous studies support a stable meteorite flux through the late Silurian and Devonian, in contrast to the mid-Ordovician, when achondritic meteorites that are rare on Earth today were common, followed by the influx of a flood of debris related to the breakup of the L-chondrite parent body. Our accumulated data for six time windows through the Phanerozoic indicate that the ordinary chondrites make up a major fraction in the meteorite flux since at least the mid-Ordovician. We note that the sources in the asteroid belt of the H and L meteorites, the two most common types of meteorites today and through much of the Phanerozoic, remain elusive.
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| 7. |
- Lee, Natuschka N, et al.
(författare)
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The extreme biology of meteorites : their role in understanding the origin and distribution of life on earth and in the Universe
- 2017. - 2
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Ingår i: Adaption of microbial life to environmental extremes. - Cham : Springer Publishing Company. - 9783319483252 - 9783319483276 ; , s. 283-325
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Bokkapitel (refereegranskat)abstract
- Meteorites have captured our fascination since our early history – they have evoked awe, fear, an irresistible curiosity, and numerous lively debates. Former historians have indicated that many of the ancient cultures and civilizations in Europe, Africa, Asia, the Inuit, and the native Indians in America regarded both the meteorite and the location of their fall as sacred. Thus, they used the meteorites as religious objects or for craft design like jewelry, weapons, or even practical things like tools and horse shoes. Today, meteorites continue to capture our fascination through popular cultural formats such as science fiction and also as a scientific window that reveals the secrets of the Solar System formation. Within academia, meteorites have always fomented keen scientific debate. It was not until the early nineteenth century that the cosmic origin of meteorites, i.e., being truly not tellurian, was approved by the scientific community after the late eighteenth-century work of Ernst F. Chladni (1794). This implied for the first time that there are other smaller bodies in the sky besides the Moon. After this, several other lively debates followed on controversial findings and hypotheses around the role of meteorites in the universe and for the evolutionary course of life on Earth, often in connection with the profound difficulties to approach this subject in an adequate scientific way. Principally the different types of meteorites (asteroids, meteors, etc.) can be viewed as a most extreme or exotic substrate, habitat, and transport mode of chemicals and possibly even of cell-based life forms for several reasons:(i)They have experienced a remarkable history since their origin as condensates from the Solar Nebula, more or less metamorphosed or molten fragments of asteroids, or rocks from Mars or our Moon.(ii)The meteorites have been exposed to multiple extreme conditions ranging from milliseconds to billions of years duration when traveling through the interplanetary space, until they fell down on an astronomical body like Earth.(iii)Once on Earth, the meteorites get exposed to different weathering conditions, which often makes it a challenge to retrieve their former history in an unambiguous way.
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| 8. |
- Rout, Surya S., et al.
(författare)
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Shock history of the fossil ungrouped achondrite Österplana 065 : Raman spectroscopy and TEM of relict chrome-spinel grains
- 2018
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Ingår i: Meteoritics and Planetary Science. - : Wiley. - 1086-9379. ; 53:5, s. 973-983
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Tidskriftsartikel (refereegranskat)abstract
- Chrome-spinel grains from the fossil ungrouped achondrite Österplana 065 (Öst 065) recovered from Middle Ordovician limestone in Sweden were studied using Raman spectroscopy and TEM. All the studied chrome-spinel grains have a high density of planar fractures and planar features, not seen in chromites from the other L chondritic Ordovician fossil meteorites. Raman spectra of the host chrome-spinel grain and its planar features are similar and no signatures of high-pressure phases of chromite were found. The planar features occur along planar fractures, are enriched in ZnO, and are most probably produced due to enhanced leaching during terrestrial weathering in the marine sediment. Dislocation densities within two FIB sections prepared from two chrome-spinel grains from Öst 065 are similar to the dislocation densities found within chromite grains from the matrix of Tenham L6 chondrite. Using this observation and taking into account the presence of significant fracturing in all the grains, we conclude that the Öst 065 chrome-spinel grains were subjected to moderate to very strong shock corresponding to shock stages of S4-S6. This makes Öst 065 fossil achondrite the highest shocked fossil meteorite studied so far. This is consistent with the hypothesis that Öst 065 is a piece of the impactor that led to the L chondrite parent body breakup.
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| 9. |
- Terfelt, Fredrik, et al.
(författare)
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Asteroid break-ups and meteorite delivery to Earth the past 500 million years
- 2021
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 118:24
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Tidskriftsartikel (refereegranskat)abstract
- The meteoritic material falling on Earth is believed to derive from large break-up or cratering events in the asteroid belt. The flux of extraterrestrial material would then vary in accordance with the timing of such asteroid family-forming events. In order to validate this, we investigated marine sediments representing 15 time-windows in the Phanerozoic for content of micrometeoritic relict chrome-spinel grains (>32 μm). We compare these data with the timing of the 15 largest break-up events involving chrome-spinel–bearing asteroids (S- and V-types). Unexpectedly, our Phanerozoic time windows show a stable flux dominated by ordinary chondrites similar to today’s flux. Only in the mid-Ordovician, in connection with the breakup of the L-chondrite parent body, do we observe an anomalous micrometeorite regime with a two to three orders-of-magnitude increase in the flux of L-chondritic chrome-spinel grains to Earth. This corresponds to a one order-of-magnitude excess in the number of impact craters in the mid-Ordovician following the L-chondrite break-up, the only resolvable peak in Phanerozoic cratering rates indicative of an asteroid shower. We argue that meteorites and small (<1-km-sized) asteroids impacting Earth mainly sample a very small region of orbital space in the asteroid belt. This selectiveness has been remarkably stable over the past 500 Ma.
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| 10. |
- Aguirre-Palafox, Erick Luis, et al.
(författare)
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Zircon provenance analysis from Lower Paleocene pelagic limestones of the Bottaccione section at Gubbio (Umbria-Marche basin, Italy)
- 2019
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Ingår i: Geological Society of America. Special Papers. - : Geological Society of America. - 0072-1077. ; 542
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Tidskriftsartikel (refereegranskat)abstract
- Dating detrital zircon grains from sands and sandstones has become an important geological technique for determining sediment provenance and dispersal patterns. Here, we report what we believe to be the first provenance study of zircon grains extracted by dissolving large samples of pelagic limestone. Our samples come from the Paleocene section of the Umbria-Marche Apennines, Italy. Recovery of these zircon grains was a fortunate by-product of a study on chromite grains aimed to determine the kinds of meteorites that have fallen on Earth through time. The zircons we recovered included both euhedral crystals interpreted as airborne ash from volcanic eruptions of the same age as the sediment in which they were found, and rounded grains interpreted as windblown detrital material with a history of sediment transport, probably derived from desert regions. This study focuses on the rounded grains, to provide constraints on the source region from which they came.Samples from five levels in the 12 m immediately above the Cretaceous-Paleogene boundary at Gubbio, Italy, yielded detrital zircon grains with ages clustered in eight bands extending back to the Neoarchean. A previous study of this outcrop using proxies for the noncarbonate detrital content had suggested a source region for this dust either in North Africa or in Central Asia. A comparison of our dates from the actual dust grains to geochronological studies from the literature suggests source regions in North Africa and/or the Iberian Peninsula, rather than in Central Asia. In reaching this conclusion, we considered the orogenic events that may have produced each of the eight age bands, the specific source regions that may have supplied zircons from each age group, and the implications for paleoclimate (especially aridity) and paleowind conditions for the few million years just after the Cretaceous-Paleogene boundary.
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