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Muszyński A., Stankowski W., Szczuciński W., 2014. Field excursion to the “Morasko Meteorite” Reserve. MPSE 2014: Mars — Connecting Planetary Scientists in Europe. Field excursion guidebook The Morasko Meteorite Reserve. Poznan, 6 June 2014

Authors:
MPSE 2014
Mars — Connecting Planetary Scientists in Europe
Field excursion guidebook
The Morasko Meteorite Reserve
Poznan, 6 June 2014
Field excursion to the “Morasko Meteorite” Reserve
Andrzej MUSZYŃSKI, Wojciech STANKOWSKI, Witold SZCZUCIŃSKI
Institute of Geology, Adam Mickiewicz University, ul. Maków Polnych 16, 60-606 Poznań, Poland;
1. Introduction
The largest iron meteorite shower in Central Europe have taken place nearby contemporary
Morasko district of the city of Poznań, western Poland (Pilski, Walton 1999). The Morasko Meteorite
has already a 100 years long history of investigations. The first findings date back to 1914, when four
meteorite pieces were found by dr. Cobliner while digging of military trenches. The weights of these
meteorites were 77.5 kg, 4.2 kg and two pieces of 3.5 kg each. Up to now, more than 1500 kg of
extraterrestrial matter has been documented with particular pieces ranging in weight from a few grams
to more than 260 kg. Particularly successful were surveys in 2006, when several large lumps of
meteorite, including 164 kg heavy one, were found. So far, the largest meteorite was found in October
2012 (261.2 kg).
Another specific feature of the Morasko area are impact craters. The depressions up to 100 m in
diameter located nearby the site of the first meteorite pieces findings were for the first time suggested
to be the craters by Pokrzywnicki (1957). The presence of both, extraterrestrial metallic material and
the morphological effects of its fall, make the Morasko to be one from less than 20 documented sites
worldwide, where the remnants of the impacting body are found next to the craters.
During the field excursion, we will visit the site of the Morasko craters and discuss the problems of
the meteorite fall onto the soft glacigenic sediments which have been raised in several publications
(e.g., Hurinik 1976, Stankowski 2008, Muszyński et al. 2012). Also, interesting geomorphological
aspects and a gerelationships of the deposits in which the craters were formed will be presented.
2. Geological setting, distribution and morphology of the Morasko craters;
glacitectonics
Góra Moraska (Morasko hill) is built of deformed Neogene and Pleistocene deposits (the oldest >
0.5 Ma), and its palaeomorphological rise is older than the last glaciation (Stankowski 2001).
During the ice maximum extent of the last glaciation (Vistulian, ~20000 BP), shallow glacitectonic
deformation took place and morphological features similar to present day features were formed. The
degradation of permafrost in Moraska Góra and surroundings occurred between 14,000 and 10,000 yr
BP. Evorsive depressions and kettle-holes, predominantly longitudinal and irregular in shape, started
to fill with organic deposits before the Holocene (Tobolski 1976; Stankowski 2008). The age of the
deepest organic infill in the thermocarst depressions is documented palynologically (Tobolski 1976)
and by 14C dating (Stankowski 2001).
In a small area NE of the Góra Moraska summit, several regular oval depressions are found, with
circumferential ridges of different shape (Fig.1). The age of their organic infill is much younger than
that in cryogenic ones from pre-Holocene times.
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Fig. 1. Depression forms of evorsive and ice-melting origin (a) and meteorite craters (b)
in the neighbourhood of Moraska Góra (after Stankowski 2001)
The Moraska Góra hill has a glacitectonic structure developed not only during the last glaciation.
Complexity of the geologicical building was elaborated by Karczewski (1976) - see Fig. 2. Very
characteristic is high position (up to 150 m a.s.l) of Neogene Poznań clay.
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Fig. 2. Schematic cross-sections through depressions A (above) and F (below), (after Karczewski 1976). 1 soil,
2 Poznań variegated clay, 3 – sandy loam, 4 clayey sand, 5 organodetrital deposits
3. Timing of the meteorite fall
The age of the Morasko meteorite impact was assessed using several methods. They include
methods based on thermoluminescence (TL), optically stimulated luminescence (OSL), radiocarbon
dating (14C), as well as pollen analyses.
As a result of the meteorite passage through the atmosphere, its surface is heated and partly melted
and while reaching the ground often a thin crust layer of melt and sinter with some grains of impacted
sediments is formed. These sediment grains are characterised by impact-zeroed luminescence, thus
providing an excellent material for dating of the impact (Stankowski et al. in press). The TL datings of
the Morasko meteorite sinter layer revealed ages from 4700 to 6100 years. The same method used for
material obtained from the thin layer of melt gave ages of 4600 to 4900 years ago.
The insight into the age of the meteorite fall is provided not only from the surface crusts of the
meteorites but also through analyses of the material from the bottom and slopes of the impact craters.
The original sediments were of Neogene and Quaternary age (more than 10000 years old). The
measurements of 101 samples using OSL dosimetric technique provided age range from about 350
000 to about 4000 years ago. Among the results 43% revealed age younger than 10000 years, with
13% indicating age of about 5000 years ago. It suggests that at least a portion of the analysed
sediments were zeroed or partly zeroed during the impact (Stankowski, Bluszcz 2012). The results are
an important argument in favour of impact origin of the Morasko craters.
According to palynological analyses by Tobolski (1976) the beginning of sedentation (filling with
organic matter) in the craters have started not earlier than the middle of Atlantic period (Table 1). This
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results were conformed later by 14C data (see Table 1). Based on all the available data the Morasko
meteorite shower took place around 5000 years ago.
Years BP
Palynological
estimations
(Tobolski 1976;
Milecka, unpublished)
14C datings (Gliwice and Poznań laboratories)
Craters:
A B C E
0
5000-5500
260±80
690±95
640±90
690±150
990±160
610±75
650±110
1000
2000
2690±170
3000
3360±100
4000
4465±35
4495±35
4760±40
5000
6000
7000
8000
9000
10000
14C data for mineral/organic boundary in different boreholes, elaborated by Pazdur (Gliwice) and Goslar
(Poznań; in italics).
Table 1. Morasko meteorite craters - radiometric data and palynological
estimations (after Stankowski, Muszyński 2008).
4. Distribution of the meteorite finds
The great majority of finds of Morasko are confined to a relatively small area on the northern slope
of a terminal moraine from the last glaciation. No find has been reported north of the moraine, except
two doubtful irons which were reportedly found in the town of Oborniki, and lost before detailed
examination could be made (Pokrzywnicki 1964). Most meteorite fragments were found at a depth of
~50-80 cm. However, the latest findings indicate that the meteorites can occur deeper than 160 cm
(Pilski et al. 2012).
5. The Morasko strewn field
As accepted by many authors, the fall of the Morasko iron produced several craters, up to a few
tens of meters across, in soft glacial sedimentary deposits (Pilski, Walton 1999). The relief of the fall
site is typical of a glacitectonically deformed front moraine of the latest Vistulian stage (see details in
Stankowski 2001, 2008). Stankowski(2008) summarized the current state of knowledge on the
Morasko meteorite fall and gave an extended reference list.
The distribution of the Morasko iron finds is shown in Fig. 3a and 3b. The three iron falls,
Morasko, Przełazy and Jankowo Dolne, broadly lie along a WSW-ENE line, with the largest Morasko
fall situated approximately midway between Przełazy and Jankowo Dolne (Pilski et al. 2013).
Meteorite Morasko is known as the largest iron-meteorite shower in Europe (Pilski, Walton 1999).
Three well known iron meteorites (IAB-MG) from central-west Poland: Morasko, Seeläsgen
(Przełazy) and Jankowo Dolne, belong to the Morasko iron meteorite shower. The size of the strewn
field, including Seeläsgen and Jankowo Dolne, as well as hundreds of finds, suggest together that the
shower originated from a large meteoroid.
The first interpretation of the Morasko strewn field came from Pokrzywnicki (1964), who first
discovered that Morasko maybe an iron shower, and mapped Morasko finds. A next attempt to
determine the Morasko strewn field was made by Pilski (2003,), who added to the localities published
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by Pokrzywnicki several localities of recent finds submitted by private meteorite hunters. All new
finds were situated not far from the old ones known to Pokrzywnicki, mostly on the northern slope of
a terminal moraine.
Fig. 3a. The Morasko iron: distribution of meteorite finds (after Pilski et al. 2013)
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Fig. 3b. The Morasko iron: distribution of meteorite finds (after Pilski et al. 2013)
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6. Petrography, mineralogy and chemistry of the meteorites
The meteorites have been studied by many authors (including a few MSc students), e.g.
Pokrzywnicki (1964), Dominik (1976), Hurnik et al. (1976), Classen (1978), Czegka (1996), Pilski
and Walton (1999), Stankowski (2001), Muszyński et al. (2001), Karwowski (2004, 2005),
Karwowski and Muszyński (2006, 2007, 2008), Karwowski et al. (2009a, 2009b), Wojnarowska at al.
(2008), Jastrzębska (2009), Pilski et al. (2012) (for more references see Dworzyńska, Muszyński,
2012).
The three iron falls display many similarities in petrography, mineralogy and chemical features. All
three meteorites belong to the IABMG group. They are composed mainly of coarse-grained kamacite
and taenite, with accessory cohenite and schreibersite. A distinct feature of all three irons is the
presence of characteristic nodules, usually ca. 1-1.5cm in size, composed of graphite and troilite, with
minor silicates, sulphides, oxides and phosphates.
The large size of the body would explain the observed small differences in Ir contents, similar to
those reported from the Canyon Diablo iron. The similar chemical compositions of the irons studied,
in particular the Ir contents, indicate that the meteoroid was rather homogeneous and no important
fractional crystallization processes took place in it.
7. Micrometeorites and meteoritic dust in soil
Micrometeorites (0.115 mm in diameter) can be often found as magnetic particles in the soil of
the Morasko reserve area. In the Morasko micrometeorites, the original minerals are iron and nickel
alloys: kamacite, taenite and schreibersite. Goethite and lepidocrocite are the stable minerals of final
weathering, whilst micrometeorites in the intermediate stage of weathering contain magnetite,
maghemite and akaganeite (Karwowski, Gurdziel 2009). Chemical analysis of partly weathered
micrometeorites showed that nickel was present in numerous analyzed grains (for more details see:
Dworzyńska, Muszyński, 2012). The studied micrometeorites have the same mineralogical
composition as the Morasko iron and originated from the common meteorite shower.
Micrometeorites and meteoritic dust have been proven at many localities within the Morasko
strewn field (unpublished data). Marini et al. (2004) have shown that tiny fragments of meteorites can
form at various stages of impact. They can form from metal-rich vapour, melt or due to disintegration
of larger solid particles (Fig. 4).
Fig. 4. Various genetic types of “magnetic fines” (after Marini et al. 2004)
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8. Meteorite weathering
Iron meteorites show various degrees of weathering, depending on their location and local
conditions (Fig. 5). In the case of the Morasko iron, weakly weathered fragments are found at shallow
depth in loams, whereas those from sandy and clayey deposits at deeper levels are much more strongly
altered. The weathering products include Ni-rich iron hydroxides, and chlorides, sulphates, phosphates
and carbonates. Locally, microaggregates of a Ge-rich (up to 5at.%) metal phase are found within
secondary hydroxides (Karwowski, Gurdziel 2009).
Fig. 5. Scheme of weathering of iron meteorites (after Golden et al. 1995)
9. Morasko iron shower model
Summarizing the available observations, we may conclude that the three iron meteorite falls,
Morasko, Seeläsgen (Przełazy) and Jankowo Dolne, represent a single meteorite shower dated at ca
5000 Ma. They originated from a large and rather homogeneous meteoroid. A model showing the
geological and environmental circumstances preceding the impact of the Morasko iron shower, after
Stankowski (2001), is presented in Fig. 6.
10. Effects of meteorite impact in unconsolidated sediments - new research directions
So far, the studies in the region focused on the meteorites properties (Muszyński et al. 2012 and
references therein) and whether the depressions found in the area are related to the impact event. As
for a long time both glacigenic and impact origin of the craters has been considered (Stankowski 2008,
and references therein). The aim of the recently undertaken new research project is to extend the
previous investigations and to undertake field and laboratory investigations, as well as to perform
numerical modeling to reconstruct and assess the physical and environmental consequences of the
Morasko iron meteorite shower.
The extent of the effects of the impact (ejecta layer, wildfire etc.) is not known yet. To give an
approximated range of the size of the likely affected area one may compare the extent of forest fire
and taiga devastation in Tunguska 1908 (vide Veski et al. 2001) to illustrate the possible scale of
meteorite impact event. On the cover of the guide book is a map illustrating its possible range. This
area was also considered in the new project, which aims to address several issues:
- the precise age of the impact (dating of paleosoils and lake sediments nearby),
- assessment of the volume, dispersal pattern and properties of the sediments ejected from the
craters (field mapping supported by numerical modeling)
- estimation of the direction of the meteorite impact and the amount of released energy (geological
evidence, mineralogical impact features and the modeling)
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Fig. 6. Sketch showing the geological and environmental circumstances preceding the
impact of the Morasko iron shower (after Stankowski 2001, modified)
- quantification of the pressure/ temperature conditions during the impact (mineralogical impact
features and the modeling)
- identification of the sedimentological and geochemical signatures of the impact in distal region
(>few hundred meters from the craters) in geological archives (lake, peat sediments)
- assessment of the environmental consequences due to an atmospheric blast wave, thermal
radiation, ejecta and fallout (fires, changes in species composition, changes in surface waters
hydrochemistry based on lake and peat sedimentary record)
- assessment of the duration and the sustainability of the effects of the impact on the environment
- assessment of potential consequences on local human settlements (correlation to existing
archeological data)
- testing of various modeling approaches for impacts in unconsolidated sediments using the
Morasko impact site as an unique real world example (benchmark)
- provide interdisciplinary and quantitative data on the impact effects of small / medium scale
meteorite that may serve as a basis for the prediction of the consequences of similar future events.
The proposed project will involve a research collaboration between the Faculty of Geographical
and Geological Sciences at Adam Mickiewicz University in Poznań and the impact research team and
numerical modelling group from the Museum für Naturkunde, Leibniz Institute for Research on
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Evolution and Biodiversity (Germany). To investigate the wide range of effects due to meteorite
impact it is necessary to apply various approaches using different research methods: mineralogical,
geochemical, sedimentological, geophysical, micropaleontological, as well as numerical modeling.
The project provides a unique opportunity to perform an interdisciplinary study on recent, well-
preserved crater fields created by small/moderate size impact in unconsolidated sediments. The
presence of several sedimentary archives (lakes, peat bogs) nearby opens an excellent possibility to
reconstruct the magnitude, extent, duration, and sustainability of environmental effects. The relatively
large data set on the topography, meteorite findings, local geology, ejecta layer distribution provides
exceptional opportunities to test and improve existing numerical models, which on the other hand may
significantly improve our understanding of the impact and provide feedback for field studies (e.g.
expected from the model range of ejecta layer). The overall results may be of interest for natural
disaster management, as they will provide estimates of the expected effects in case of a similar-sized
future impact event. Moreover, Morasko - the region of the biggest known shower of iron meteorite in
Central Europe, is very attractive topic for the public and the obtained results may be of wider interest
and thus help in education on geo- and environmental sciences.
Acknowledgements. The research has been supported from Research grants N N307 33 3533 of the
Ministry of Science and Higher Education of Poland and 2013/09/B/ST10/01666by National Science
Centre, Poland
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Notes
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Notes
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Notes
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Article
Full-text available
Differences in texture and discovery location prompted us to analyze 16 irons from Morasko; one from Seeläsgen, known to have a similar composition; and a new mass found at Jankowo Dolne. These were analyzed in duplicate by instrumental neutron-activation analysis (INAA). The results show that all 18 samples have very similar compositions, distinct from all other IAB irons except Burgavli; we conclude that they are all from a single shower. Eight of the samples were from regions with large amounts of cohenite (but were largely free of inclusions) and six were from samples with very little cohenite; we could find no resolvable difference in composition between these sets, a fact that suggests that the C contents of the metal phases were similar in the two areas. Although Morasko has been classified into the IAB main group (IAB-MG), its Ir plots well outside the main group field on an Ir-Au diagram. We considered the possibility that the low Ir reflected contamination by a melt from a IAB region that ponded and experienced fractional crystallization; however, because Morasko has Pt, W, and Ga values that are the same as the highest values in IAB-MG, we rejected this model. We therefore conclude that Morasko formed from a different melt than the IAB-MG irons; the Morasko melt was produced by impact heating, but one or more of the main Ir carriers did not melt, leaving much of the Ir in the unmelted residue. Copper is the only element that shows resolvable differences among Morasko samples. Most (13 of 18) samples have 149 ± 4 μg g−1 Cu, but three have 213 ± 10 μg g−1; we interpret this to mean that the low-Cu samples have equilibrated with a Cu-rich phase, whereas there was none of the latter phase within a few diffusion lengths of the samples with high Cu contents.
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Article
The results of geological, geoelectrical and radiometric investigations of small depressions in the natural reserve “Meteoryt Morasko” are discussed. The interpretation of results suggests the impact origin of six hollows existing on the north-east slope of Morasko Hill (Moraska Góra near Poznań). The area of the reserve is unique in its combination of the occurrence of meteorites and the morphological effects of their fall.
Article
The Kaali crater field (1 sq. kilometre, 9 craters) offers a unique opportunity to recover large amounts of magnetic fines still partly preserved from late-stage weathering. SEM studies of these materials reveal an unusually wide spectrum of derivatives from the initial iron meteorite body, including minor amounts of marched metal fragments, and an abundance of more evolved products resulting from primary oxidation processes. Most of these products are sprays and splashes of liquid iron oxides, and some particles may be ascribed to oxide condensates from a vapor phase, as a result of both atmospheric ablation and vaporization upon impact. This wide range reflects varied impact conditions, due to variable masses and velocities of fragments after atmospheric disruption of the original meteoritic body. The large spectrum of magnetic fines from Kaali should provide an excellent probe into the chemical- and isotopic-fractionation of elements over a range of impact processes, from atmospheric entry to post-impact alteration. Magnetic fines from other sites of multiple impacts may have the same potential, and deserve more systematic attention.
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An oxide layer adjacent to the surface of the Hoba Ni-Fe meteorite was analyzed chemically and mineralogically. Maghemite, magnetite, goethite and lepidocrocite were the main Fe minerals found in the oxide layer surrounding Hoba. Most of the Ni from the unweathered original meteorite was distributed among the above minerals with spinel-type oxides (maghemite and magnetite) having the largest Ni fraction. Some Ni migrated to the limestone in which the meteorite is embedded. No evidence for zaratite or akaganeite was found in the oxide layer. Sulfate derived from the oxidation of troilite precipitated as gypsum. Phosphate accumulation in limestone in contact with the meteorite is probably due to phosphate adsorbed on Fe-oxides. Maghemite with some magnetite was the oxidation product immediately next to the meteorite metal surface, which accommodated most of the Ni and Fe from the meteorite into its structure. Upon oxidation, some of the Ni, which was incorporated into calcite, was released. Cobalt associated with the oxides stayed within the oxide structure regardless of the oxidation state and did not migrate to the limestone. This suggests that Co may be a good tracer for oxides of meteoritic origin.
Article
Abstract— A sequence of peat enriched with impact ejecta (allochthonous minerals and iridium) from Piila bog, 6 km away from the Kaali impact crater (island of Saaremaa, Estonia), was examined using pollen, radiocarbon, loss-on-ignition, and x-ray diffraction analyses to date and assess the environmental effect of the impact. The vegetation in the surroundings of the Piila bog before the Kaali impact was a fen surrounded by forest in natural conditions. Significant changes occur in pollen accumulation and composition of pollen in the depth interval 170–178 cm, which contains above background values of iridium (up to 0.53 ppb). Two samples from the basal silt layer inside the main crater at Kaali contain 0.8 ppb of iridium, showing that iridium was present in the impact ejecta. The impact explosion swept the surroundings clean of forest shown by the threefold decrease in the total pollen influx (especially tree pollen influx), increase in influx and diversity of herb taxa, and the relative dominance of pine. Increased input of mineral matter measured by loss-on-ignition and the composition mineral matter (increased input of allochthonous minerals) together with an extensive layer of charcoal and wood stumps in Piila bog at the same depth interval points to an ecological catastrophe, with local impact-induced wildfires reaching at least 6 km northwest of the epicenter. The disappearance of cereals in the pollen record suggests that farming, cultivation and possibly human habitation in the region ceased for a period of ∼100 years. The meteorite explosion at Kaali ranged between the effects of Hiroshima and Tunguska. The age of the Kaali impact event is placed between 800–100 B.C. based on radiocarbon dating of the peat enriched with impact ejecta in the Piila bog.
Micrometeorites: a part of iron meteorite shower of Morasko. Mineralogia Special Papers
  • M Dworzyńska
  • A Muszyński
Dworzyńska, M., Muszyński, A. (2012). Micrometeorites: a part of iron meteorite shower of Morasko. Mineralogia Special Papers, v.40, 15-17.