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Tytuł:
Nowy chondryt z Libii
New chondrite from Libya
Autorzy:
Abu Anbar, Mohamed
Kryza, Ryszard
Przylibski, Tadeusz A.
El Bahariya, Gaafar
Powiązania:
https://bibliotekanauki.pl/articles/1032649.pdf
Data publikacji:
2009
Wydawca:
Polskie Towarzystwo Meteorytowe
Tematy:
meteorite fall
meteorites
ordinary chondrite
Opis:
On Saturday, 21 of May, 2006, a fall was observed and the stony meteorite was found in a small crater on an apple farm at Werdama village, near Al Beda town in Libya. Based on preliminary examinations, the authors described the meteorite as an ordinary chondrite. Further research aiming at full characteristics, classification and registration of the meteorite is in progress.
Źródło:
Acta Societatis Metheoriticae Polonorum; 2009, 1; 9-12
2080-5497
Pojawia się w:
Acta Societatis Metheoriticae Polonorum
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Prawdopodobny spadek meteorytu w Gaju k. Wyszkowa
A possible meteorite fall in the willage of Gaj near Wyszków
Autorzy:
Kosiński, Janusz W.
Powiązania:
https://bibliotekanauki.pl/articles/1032674.pdf
Data publikacji:
2009
Wydawca:
Polskie Towarzystwo Meteorytowe
Tematy:
doubtful meteorite fall
meteorites
meteorites of Poland
searching for meteorites
the Gaj meteorite
Opis:
In the middle of June 1927 a few inhabitants of the village of Gaj (10 km from Wyszków; central Poland) witnessed a meteorite fall. The solid fell into a swamp, which made searching for it very difficult. Searching work was held in the years 1957-1958, 1981-1982, 1990 and 1996. Present searching, which was started in 2005, still has not led to the meteorite finding.
Źródło:
Acta Societatis Metheoriticae Polonorum; 2009, 1; 82-86
2080-5497
Pojawia się w:
Acta Societatis Metheoriticae Polonorum
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Account of circumstances surrounding the fall of a meteorite in Sołtmany village
Autorzy:
Woźniak, B.
Woźniak, M.
Powiązania:
https://bibliotekanauki.pl/articles/411484.pdf
Data publikacji:
2012
Wydawca:
Polskie Towarzystwo Meteorytowe
Tematy:
meteorite fall
Sołtmany village
Opis:
Report from the place of the event the fall of a meteorite in the village of Sołtmany
Źródło:
Meteorites; 2012, 2, No. 1-2; 9-14
2299-0313
2299-1220
Pojawia się w:
Meteorites
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Bulk chemical composition of Sołtmany chondrite
Autorzy:
Przylibski, T. A.
Łuszczek, K.
Powiązania:
https://bibliotekanauki.pl/articles/411498.pdf
Data publikacji:
2012
Wydawca:
Polskie Towarzystwo Meteorytowe
Tematy:
meteorite
ordinary chondrite
L-chondrite
bulk composition
meteorite fall
observed fall
Opis:
The authors examined the bulk chemical composition of the Sołtmany chondrite which fell on April 30th, 2011 in Northern Poland. Based on the analysis of 47 elements, it was concluded that Sołtmany is representative of L-type of ordinary chondrites. However, compared to the average values observed in other L-type ordinary chondrites, Sołtmany displays higher content of Ni, P, Cd, Pb, and As. The Ni and P content closely resembles typical values for H-type ordinary chondrites. Furthermore, Sołtmany displays other distinct properties including very low Zn content and lower contents of Mo and Zr than the average values found in other L-type ordinary chondrites. Consistent with other L-type ordinary chondrites, the absolute content of REE in Sołtmany is higher than that of CI-type carbonaceous chondrites while the REE trend lines for both Sołtmany and CI-chondrites are similar. Due to similar times of year of when both falls took place and the proximity of their strewn fields, the chemical composition of Sołtmany was compared with that of Jesenice, an L6 ordinary chondrite which fell on April 9th, 2009 in Europe. The analysis led to a conclusion that Sołtmany and Jesenice are not launch-paired. Nevertheless, even though they do not represent fragments of the same meteoroid, their origin on a common parent body (an asteroid – planetesimal) cannot be conclusively ruled out on the sole basis of their bulk chemical composition.
Źródło:
Meteorites; 2012, 2, No. 1-2; 31-37
2299-0313
2299-1220
Pojawia się w:
Meteorites
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Sołtmany meteorite
Autorzy:
Karwowski, Ł.
Powiązania:
https://bibliotekanauki.pl/articles/411492.pdf
Data publikacji:
2012
Wydawca:
Polskie Towarzystwo Meteorytowe
Tematy:
meteorite
ordinary chondrite
L6 chondrite
meteorite fall
hammer meteorite
Warmia-Masuria Province
Sołtmany village
Opis:
This paper presents the results of a mineralogical and petrological study of the Sołtmany meteorite, which fell on April 30, 2011 in northern Poland. The meteorite was found almost immediately after it fell and has been little altered by weathering. Sołtmany is not the only observed fall of an L6 chondrite over Europe in the past few years. The preceding fall of this type, Jesenice (Slovenia), was also witnessed in April of 2009. However, it was not until several weeks after the fall that the first specimen of Jesenice was found, whereas Sołtmany was collected after a few minutes and submitted for analysis within a couple of days. The author presents mineral and petrographic features and chemical characteristics of mineral phases in Sołtmany. The mineral components are represented by metallic phases (kamacite, taenite, tetrataenite, native copper), as well as chromite, olivine, low and high-calcium pyroxene, feldspar, chlorine-bearing apatite, and merrillite. This study also describes the texture of the meteorite and takes notice of a low number of preserved chondrules and the presence of oval chondrule like areas, which exhibit a metamorphosed, recrystallized texture. Sołtmany was classified as an L6 ordinary chondrite with a weathering grade of W0. A shock stage S2 was determined on the basis of undulose extinction and lack of planar fractures in olivine crystals.
Źródło:
Meteorites; 2012, 2, No. 1-2; 15-30
2299-0313
2299-1220
Pojawia się w:
Meteorites
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Kamień, który zniszczył wieżę więzienną
Stone, who destroyed the prison tower
Autorzy:
Woźniak, Beata
Woźniak, Marek
Powiązania:
https://bibliotekanauki.pl/articles/1032973.pdf
Data publikacji:
2013
Wydawca:
Polskie Towarzystwo Meteorytowe
Tematy:
Pierre Borel
Pierre de Noyers
Warsaw
doubtful fall
meteorite fall
meteorites
meteoritica
wiki.meteoritica.pl
Opis:
In his catalogue (Klein 1904) Klein described many events concerning meteorites, for example information about a fallen meteorite which destroyed a prison tower in Warsaw in 1600. He managed to find an original source of the information, specify the date and determine which tower had been hit by falling meteorite. The report of that event could be found in one source only and was copied by many searchers. The issue thus remains open whether we deal with a real description of the event.
Źródło:
Acta Societatis Metheoriticae Polonorum; 2013, 4; 120-128
2080-5497
Pojawia się w:
Acta Societatis Metheoriticae Polonorum
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Meteors and meteorite falls in Morocco
Autorzy:
Ibhi, A.
Powiązania:
https://bibliotekanauki.pl/articles/411969.pdf
Data publikacji:
2013
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
Meteor
meteorite
fall
bright bolide
Morocco
Opis:
During the last eighty years, thirteen meteorite falls were recorded in Morocco, which ten are well documented and named Douar Mghila, Oued el Hadjar, Itqiy, Zag, Bensour, Oum Dreyga, Benguerir, Tamdakht, Tissint and Aoussred. It represent only 0.011 % of the Moroccan declared meteorites.The authenticated observed falls represent three types of different meteorites, eight ordinary chondrites (Four of type LL, three of type H and one of type EH), one carbonaceous chondrite and one Shergottite basaltic achondrites. The Morocco meteorite fall recovery rate, during the past eighty years, is low 0.11 falls per year on average per 2.11 km2 (or approximately one fall recovery per 10 year time interval).
Źródło:
International Letters of Chemistry, Physics and Astronomy; 2013, 12; 28-35
2299-3843
Pojawia się w:
International Letters of Chemistry, Physics and Astronomy
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Sprawozdanie z poszukiwań meteorytów w Oslo
Search report of meteorites in Oslo
Autorzy:
Tymiński, Zbigniew
Stolarz, Marcin
Kubalczak, Tomasz
Burski, Maciej
Zaręba, Paweł
Holst, Martin
Bilet, Morten
Powiązania:
https://bibliotekanauki.pl/articles/1032969.pdf
Data publikacji:
2013
Wydawca:
Polskie Towarzystwo Meteorytowe
Tematy:
Oslo meteorite
chondrite
hammer
hunting for meteorites
meteorite fall
meteorite strewnfield
meteorites
Opis:
A piece of a meteorite that had crashed through the roof of a cottage house was find in the central Oslo quarter Rodelřkka at the beginning of March 2012. Some days later the second discovery in the melting snow of Ekebergsletta hilltop plateau triggered the hunting for meteorites in almost all sides of Oslo. The pieces of third meteorite broken by cars and spread out by snowplow was discovered on the asphalt road side by Maciek Burski, the member of Polish Meteoritical Society. Later on the missing fragments of the Maciek’s most east find was collected by Meteoritical Section members of Comet and Meteor Workshop (PKiM) with the help of local meteoritical authorities. The total mass of this unobserved fall is 6.22 kg in five pieces spread out in the eight km-long strewnfield with 200 g and 4.65 kg meteorites on the opposite ends. The Meteorite is not classified yet but unofficial information is “breccia H3-4”.
Źródło:
Acta Societatis Metheoriticae Polonorum; 2013, 4; 108-114
2080-5497
Pojawia się w:
Acta Societatis Metheoriticae Polonorum
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The meteorite fall near Boumdeid, Mauritania, from September 14, 2011
Autorzy:
Buhl, S.
Toueirjenne, C.
Hofmann, B.
Laubenstein, M.
Wimmer, K.
Powiązania:
https://bibliotekanauki.pl/articles/411504.pdf
Data publikacji:
2014
Wydawca:
Polskie Towarzystwo Meteorytowe
Tematy:
Boumdeid (2011)
meteorite fall
Mauritania
trajectory scenario
L6 chondrite
cosmogenic radionuclides
Opis:
On the evening of September 14, 2011 at 21:00 GMT a bright bolide was observed by hundreds of eyewitnesses in the area north and west of the town of Kiffa, in the department of Assaba, in south Mauritania. A terminal fragmentation and sound phenomena were observed near the end point of the trajectory. At least one mass of 3.5 kg was observed to impact and recovered the morning after the fall near Boumdeid (or Bou Mdeid), around 60 km north of Kiffa. Subsequently a large number of eyewitness accounts were recorded and mapped by GPS. The present paper provides a scenario for the trajectory of the Boumdeid (2011) meteorite based on the available parameters and wind data at the relevant altitudes. In addition the paper presents the results of the mineralogical and chemical analysis of the recovered meteorite which is consistent with a classification as ordinary chondrite of type L6, shock stage S2, and a weathering grade of W0. Following its analysis and classification, the meteorite was published under the official name Boumdeid (2011) in Meteoritical Bulletin, no. 100, MAPS 49(8), (2014). Gamma ray spectroscopy was conducted 84 days after the fall and the detection of short-lived radionuclides such as 56Co and 46Sc confirmed the recency of the event. Derived from the data of 60Co, 54Mn and 22Na the approximate preatmospheric radius of the meteorite body was 10–20cm. The report is also intended to serve as a case example for post-event data recovery and trajectory reconstruction in areas not covered by sky-camera networks and with limited scientific infrastructure.
Źródło:
Meteorites; 2014, 3, No. 1-2; 5-18
2299-0313
2299-1220
Pojawia się w:
Meteorites
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Chondryt Sołtmany
Sołtmany chondrite
Autorzy:
Przylibski, Tadeusz A.
Powiązania:
https://bibliotekanauki.pl/articles/1033061.pdf
Data publikacji:
2016
Wydawca:
Polskie Towarzystwo Meteorytowe
Tematy:
Gefion family
L6
asteroid
atomic weight
bulk chemistry
cosmic-ray exposure age
cosmogenic radionuclides
density
fusion crust
magnetic susceptibility
meteorite
meteorite age
meteorite fall
mössbauer spectroscopy
noble gas
ordinary chondrite
organic matter
parent body
porosity
primordial radionuclides
thermophysical properties
troilite thermometer
Opis:
The Sołtmany hammer meteorite is classified as an ordinary chondrite type L6, W0, S2. At present it is the most thoroughly and comprehensively examined Polish meteorite. A comprehensive petrological, mineralogical and geochemical analysis alongside the investigation of its physical and particularly thermophysical properties, and, most of all, analyses of cosmogenic radionuclides and noble gases isotopes content, as well as the use of a troilite thermometer has made it possible to draw interesting conclusions concerning the genesis and evolution of the parent body and the history of the parent meteoroid and, finally, the Sołtmany meteorite. The present report attempts at summing up the results of studies conducted at several European research centres in the last four years. The age of the the Sołtmany chondrite parent rock has been defined at 4.137 billion years. It was formed at a temperature of up to 440–450 K (about 170°C), probably at a depth of up to 3 to 7 km under the surface of the parent body, i.e. at a pressure of the order of 1–2.4 kbar. Such a low temperature during the accretion, diagenesis and metamorphism of the parent body may point to its complicated development, which may be in part due to collisions of partially melted planetesimals. Like with other type L ordinary chondrites, one can infer that the parent body could have been destroyed about 467 million years ago, at the time of a catastrophic collision which led to the formation of Gefion family of planetoids. Perhaps one of the bodies in this family was involved in another collision about 29.2 million years ago, which resulted in ejecting the parent meteoroid of the Sołtmany chondrite onto the Earth collision trajectory. Before entering the Earth’s atmosphere, this meteoroid had the mass of about 36 kg and the diameter of ca 13.5 cm. During its flight through the atmosphere, it rotated and somersaulted, which resulted in the formation of an uniform thin (0.5–0.7 mm) fusion crust, whose temperature reached 1000°C. In the last phase, the Sołtmany meteorite fell almost vertically and its mass was a mere 3% of the mass of the parent meteoroid – 1.066 kg. It hit the roof and then the concrete stairs of a farm building, which caused it to break into two bigger and many small pieces. It was found a few minutes after the fall, which occurred at 6:03 a.m. (CEST, UTC+2:00) on 30 April 2011, by Wydmińskie Lake in northern Poland (54°00,53’N, 22°00,30’E). The Sołtmany chondrite is one of just 14 meteorites in which the activity concentration of the cosmogenic 52Mn has been determined, and one of the few ordinary chondrites where the concentration of organic matter has been defined. As a result, it was found out that unlike in carbonaceous CI chondrites, the composition of organic particles is dominated by less complex compounds (CHO and CHOS) than CHNO and CHNOS compounds. This may indicate the decomposition of more complex organic compounds into particles with simple structures during magmatic and metamorphic processes related to formation of type L ordinary chondrites.
Źródło:
Acta Societatis Metheoriticae Polonorum; 2016, 7; 93-122
2080-5497
Pojawia się w:
Acta Societatis Metheoriticae Polonorum
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Jeszcze jedna dyskusja na temat daty spadku meteorytu Morasko
Another discussion about date of Morasko meteorite fall
Autorzy:
Walesiak, Tomasz
Powiązania:
https://bibliotekanauki.pl/articles/1033089.pdf
Data publikacji:
2017
Wydawca:
Polskie Towarzystwo Meteorytowe
Tematy:
Morasko meteorite
bright meteor
cosmic catastrophy
dating
history of Wielkopolska
observed fall
Opis:
It’s over 100 years after discovery of the first iron meteorite in the area of Morasko, but still we are not sure about date of the fall. Recent researches suggest that it happened about 5000 years ago, however there are some other facts proving, that event took place in the last millenium. Verification o 14C radio carbon dating results revealed, that it can give us only the maximum date (meaning: not older than). The main problem was that probes were taken from mixed types of sediments – some created before and some after the impact. Few years earlier there was another 14C examination of sediments lying beyond the floor of 2 small cavities and their age was estimated to be approximatelly 700 years BP. Similar results were received after verification of organic matter under charcoal in the weathering crust of the meteorite, which was found in the Morasko Restricted Area. Another proof was discovery of shrapnel in the root of old tree, which could not be older than 800–1000 years. At least 2 times it was discussed, if finding of Morasko iron meteorites couldn’t be matched with described observation A.D. 1301, mentioned in annales, hovever nobody was able to prove it. Analysis of historical documents lead to information of appearance of 3 suns, after sunrise, what happened in 14 Feb. 1271. Further investigation of other sources gave us even more facts. We can read in annales that in the same year, castles and cities were burned and destructed to the ground. There is also information that Poznan, the largest city in the area (approx 7.5 km South from the Morasko), was burned in (or shortly before) the year of 1274. What is more Annales from Poznan and from its parent town Wielkopolska were finished in A.D. 1271, just in the middle of the sentence. Finally, confirmation is given by archeological researches, which tell us that city walls and castle of Poznan were ruined shortly after they were constructed, but scientists found difficulty to answer, when exactly it could happen. The main problem was unknown weapon, able to leave such a large destruction, even when considered next centuries. As we can find in annales that Poznan in A.D. 1253 had castle and fortifications so only iron meteorite impact in 1271, producing craters in the area of Morasko and Umultowo, can explain the scale of the devastation discovered by archeologists.
Źródło:
Acta Societatis Metheoriticae Polonorum; 2017, 8; 123-148
2080-5497
Pojawia się w:
Acta Societatis Metheoriticae Polonorum
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spadki meteorytów w 2017 roku. Okoliczności i obserwacje
Meteorite falls in 2017. Circumstances and observations
Autorzy:
Żmija, Mateusz
Powiązania:
https://bibliotekanauki.pl/articles/1033123.pdf
Data publikacji:
2018
Wydawca:
Polskie Towarzystwo Meteorytowe
Tematy:
bolide
chondrite
eucrite
fireball
meteor
meteorite
meteorite fall
summary
Opis:
This scientific paper is a summary of the meteorite falls in 2017: Broek in Waterland (Holland), Tres Irmaos (Brazil), Serra Pelada (Brazil) and Kheneg Ljouâd (Morocco). The study also includes a section about unconfirmed falls, such as Puya Medio (Colombia), Mukundpura (India), Crawford Bay (Canada) and Sadiya (India). The vast majority of these specimens is ordinary chondrites of the L and LL groups. Only Serra Pelada meteorite turned out to be eucrite and Mukundpura is suspected to be carbonaceous chondrite. The author collects and organizes basic information about these findings and compares the latest data with statistics from previous years. The description of the circumstances of finding meteorites are brief and maintained in the popular-scientific tone. The text also includes a set of fireballs and bolides that could end with a meteorite fall. Among them is also a bolide that was visible from Poland. The thesis resembles the criteria for dividing meteors and notes the differences in their naming. It is extended by analogies and comparisons that make possible to look at the issues from different perspectives: from the statistical, through the media, to the historical one.
Źródło:
Acta Societatis Metheoriticae Polonorum; 2018, 9; 187-205
2080-5497
Pojawia się w:
Acta Societatis Metheoriticae Polonorum
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spadki meteorytów w 2018 roku. Okoliczności i obserwacje
Meteorite falls in 2018. Circumstances and observations
Autorzy:
Żmija, Mateusz
Powiązania:
https://bibliotekanauki.pl/articles/1033142.pdf
Data publikacji:
2019
Wydawca:
Polskie Towarzystwo Meteorytowe
Tematy:
achondrite
bolide
chondrite
fireball
meteorite
meteorite fall
summary
superbolide
Opis:
This scientific paper aims to systematize knowledge about the circumstances of meteorite falls in 2018. Eight of them were officially confirmed by The Meteoritical Society: Hamburg (USA), Ablaketka (Kazakhstan), Aba Pan (Nigeria), Mangui (China), Ozerki (Russia), Renchen (Germany), Gueltat Zemmour (Morocco), Komaki (Japan). Seven more have not yet been classified: Central Kalahari (Botswana), Glendale (USA), Benenitra (Madagascar), Bhakkar (Pakistan), Ghadamis (Libya), Elkouran (Morocco) and meteorite fall from the Sahara Desert. It turns out that the most numerous group of meteorite falls in 2018 were L6 chondrites. There were no iron or stony-iron falls. The author collected information from many different sources. He analyzed entries in the MetBull catalog, publications in social media and press reports in order to compare them with official data from previous years. In this way, he tries to prove that although the circumstances of each meteorite fall are different, coherent conclusions can be drawn from them, and these can help meteorite researchers, for example, in verifying eyewitness accounts.
Źródło:
Acta Societatis Metheoriticae Polonorum; 2019, 10; 199-221
2080-5497
Pojawia się w:
Acta Societatis Metheoriticae Polonorum
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spadki meteorytów w 2019 roku. Okoliczności i obserwacje
Meteorite falls in 2019. Circumstances and observations
Autorzy:
Żmija, Mateusz
Powiązania:
https://bibliotekanauki.pl/articles/1033169.pdf
Data publikacji:
2020
Wydawca:
Polskie Towarzystwo Meteorytowe
Tematy:
bolide
carbonaceous
chondrite
fireball
meteor
meteorite
meteorite fall
summary
Opis:
In 2019 two meteorite showers occurred on Earth, which ended with the fall of hundreds of fragments in Cuba and Costa Rica. Apart from them, meteorites with a total weight of probably less than 10 kg landed in Algeria, Morocco, Iran, India, and Germany. This work is another summary of the year in terms of meteorite falls. It includes information on the circumstances of these phenomena and their scientific consequences. The author collected information from many sources, especially the media and meteorite hunters, to describe in a brief form how the meteorites fell last year. The purpose of his work is to gather basic and proven knowledge, which can serve as an inspiration to further explore the history of meteorites, own meteorite hunting, and draw the attention of researchers to interesting falls in distant regions of the world.
Źródło:
Acta Societatis Metheoriticae Polonorum; 2020, 11; 141-157
2080-5497
Pojawia się w:
Acta Societatis Metheoriticae Polonorum
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Przegląd najważniejszych prac dotyczących próby ustalenia daty spadku meteorytów oraz wieku kraterów Morasko
Review of most important papers regarding attempts to determine the date of Morasko meteorite fall and age of the craters
Autorzy:
Walesiak, Tomasz
Powiązania:
https://bibliotekanauki.pl/articles/1830331.pdf
Data publikacji:
2021
Wydawca:
Polskie Towarzystwo Meteorytowe
Tematy:
age
craters
dating
fall
luminescence
meteorite Morasko
palynological
radiocarbon
Opis:
One of criteria suggesting impact origin may be recognition of extraterrestrial matter inside or around suspected cavities. In case of Morasko some dating results throw doubt on link between craters and meteorites. Conclusion of some past research papers was that cavities were formed about 5 ka BP (e.g. palynological investigation, luminescence dating), while more or less facts testify fall in the Middle Ages (e.g. “young” charcoal pieces in crust of meteorites or shrapnel stuck in the roots of old tree). In this paper we perform comprehensive analysis of each result and check if there exists alternative explanation. During past palynological investigation, there were examined two craters. It was concluded that beginning of accumulation of sediments in smaller cavity started 5500–5000 BP. However, pollen spectrum for largest basin was different suggesting younger age. The problem is that according to bathymetric maps, samples could be collected from inner uplift (similar feature was observed inside Porzadzie and Jaszczulty, unconfirmed impact structures yet). If we compare profiles from craters with recent research (palynological study supported by radiocarbon dating) on sediments in Lake Strzeszynskie (6 km SW from Morasko) pollen spectrum seems to be similar more to results dated to <1000 BP. Especially percentage of non-arboreal pollen for both examined Morasko craters is much higher (5 times greater than it was for layer dated to 5 ka BP in Lake Strzeszynskie). Possibility of short disturbance (related to impact) cannot be excluded, but in such case any time of event should be taken into account. For small lakes (like those filling the craters) also local conditions could play important role. Analysis of luminescence dating may also discuss past conclusions. OSL method applied for samples taken from the thin layer of sand in the bottom of largest structure (under 3,9 m of organic sediments filling the crater) suggested age 5–10 ka BP for 24 aliquots. Same number of samples (24) revealed age 0–5 ka BP (13 samples with age <3 ka BP including several younger than 1 ka BP). Older dates can be explained by partial or even no zeroing, but last contact with light (zeroing signal) of sand grains (excavated from depth of almost 4 meters under organic matter) seems that might occur only during (or shortly after) the impact. It is difficult to find convincing arguments, which can undermine initial radiocarbon dating giving age <1 ka BP for 7 of 9 samples taken from the bottom layer of organic sediments from three Morasko craters. Same issue may exist with small charcoal pieces with age <2 ka BP (and several dated to ~700 BP) discovered deep in sinter-weathering crust of meteorites. Study of charcoal particles excluded their origin during post-sedimentary processes (like forest fire) unless meteorite fragments were laying directly on the surface for period between impact and wildfire (surviving whole time inhospitable climate conditions). There are two other possible explanations of charcoals. Either they were present at location as a result of past forest fire or they were produced during impact. However, similar small charcoal pieces were discovered around many craters (Kaali, Ilumetsa, Campo del Cielo, Whitecourt) and they were successfully used to estimate maximum age of those structures. During second stage of 14C dating the age obtained from three samples (taken few centimeters above the mineral bottom) was estimated ~5 ka BP. Looking for answer why these results are so different from previous once there may be mentioned at least two options. Lake sediments is difficult matter for radiocarbon dating and results may be hundreds or even thousands years older than real age. Second explanation may be that older matter (remnant of trees, paleosoil etc.), distributed around craters during impact, could be displaced by wind, rain, erosion and trapped in the bottom of cavities. The argument, which may be also against hypothesis of impact ~5 ka BP is meteorite shrapnel stuck in the roots of old tree. Result of expertise showed, that there exists mechanical damage in the wood and the only possible explanation is that meteorite has hit living tree. Maximum age, that this type of wood may preserve (inside building) is 1,8 ka while in natural environment not more than 500 years. Anyway some further examinations should be performed. The age obtained during AMS 14C dating of 2 samples from thin layer of paleosoil, discovered under overturned flap around largest Morasko crater, was ~5 ka BP. Observation that preserved layer of paleosoil is approximately 3 times thinner than thickness of modern soil may lead to conclusion that during impact top (younger) layer of organic sediments was removed and only older part “survived” in few locations close to the rim. The conclusion of the research was that dating provides maximum age of the impact (which does not exclude much younger impact <1 ka BP) so could be considered as right explanation of past discrepancies.
Źródło:
Acta Societatis Metheoriticae Polonorum; 2021, 12; 129-148
2080-5497
Pojawia się w:
Acta Societatis Metheoriticae Polonorum
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 22

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