Abstract paper: THE ENIGMATIC NIEDERRHEIN (GERMANY) DEPOSIT: EVIDENCE OF A MIDDLE-PLEISTOCENE METEORITE IMPACT STREWN FIELD

Full text

THE ENIGMATIC NIEDERRHEIN (GERMANY) DEPOSIT: EVIDENCE OF A MIDDLE-
PLEISTOCENE METEORITE IMPACT STREWN FIELD G. Waldmann1, F. Herten2, M. Hiltl3, K. Ernstson4,
1Haus der Natur, Kloster Knechtsteden, 51540 Dormagen, Germany (georg.waldmann@gmx.net), 2ENERKO
INFORMATIK GmbH, Markt 45-47, 52062 Aachen, Germany (friedel.herten@enerko-informatik.de), 3Carl Zeiss
Microscopy GmbH, D-73447 Oberkochen, Germany (mhiltl@online.de) 4Faculty of Philosophy I, University of
Würzburg, 97074 Würzburg, Germany (kernstson@ernstson.de).
Introduction: In the last years during intense
geologic field work on the Pleistocene in the
Niederrhein district (Fig. 1) author G.W. regularly
picked up conspicuous rocks of quite different form,
material and facies, which appeared to belong to a
common incidence but which however had never
before been given consideration by local and regional
geologists, not to mention any reference in the
literature. Together with author F.H. and over time the
sampled rock mass as well as the affected sample area
increased. Likewise, with regard to the established
geology in the Niederrhein district, the conviction of a
strange geologic process and origin arose. Here we
report on a provisional model for the origin of this
enigmatic deposit that far from having clarified all
observations and understanding the complete context
focuses on an extraterrestrial component in the form of
a probable meteorite impact event.
Fig. 1. Location map. Fig. 2. Typical find in the field.
Geologic setting and sample conditions: The
finds of the sharp-edged rocks under discussion
concentrate on pit mines of fossil river terraces about
30 m below the present landscape and contrast
markedly with the exploited well-rounded gravel
material. Surface finds (Fig. 2) in more than 40
localities in the open landscape on eroded slopes are
meanwhile completing the occurrence.
In the beginning the rocks attracted attention
because of their basically basaltic and frequently
observed melt rock character. The sharp-edged basalts
on the one hand were puzzling because the nearest
basalt natural occurrences were about 100 km distant,
and fluvial and glacial transport because of the
sharpness of the fractured basalts could reasonably be
questioned. More startling was the observation of
abundant native iron in the basalts in the form of both
metallic spherules and irregularly shaped inclusions.
Native iron in basalt is well known from Greenland
deposits [1] but otherwise is extremely rare on Earth.
One of these rare occurrences (Bühl) was exploited
until the early 20th century near the city of Kassel, but
the distance to the Niederrhein location is roughly 200
km practically excluding a direct connection. Further
preoccupation with the enigmatic rocks featured more
and more surprising observations, which reminded of a
meteoritic context and which is described in more
detail below.
The peculiar rocks - form and material: Apart
from heavy chunks of pure iron the basic group of
rocks and in the field most noticeable are basaltic
cobbles and boulders weighting up to 10 kg with in
most cases a contrasting fusion crust of variable
appearance (Fig. 3, 4). The basaltic core may be
widely untouched (Fig. 3) or has changed to an in part
strongly vesicular melt rock (Fig. 4). The fusion crust
is monomictic basaltic, polymictic brecciated or pure
glass (Fig. 5). The black fusion crust in Fig. 4 is a
polymictic melt rock containing various vesicular glass
fragments in a vesicular glass matrix (Fig. 4A, B). The
thickness of the fusion crust varies between the order
of a millimeter (Fig. 3F, 3A) and a few centimeters
(Fig. 3C, E). Fig. 3C shows continuously decreasing
vesicle size changing into a dense glass crust with
Mohs scale 7. Special forms are polymictic melt rocks
with flow texture (Fig. 4C, D) or glass-bearing
sedimentary rocks (e.g. quartzites) enwrapped with a
polymictic, mostly basaltic fusion crust (Fig. 4E).
Frequently sedimentary matter containing calcite and
quartz is attached to the fusion crust (Fig. 6).
Conspicuously paired combinations of basically
different rock types are shown in Fig. 5. In relation to
common meteoritic texture but for now genetically
irrelevant we define "chondritic" and "achondritic"
breccias in contact with basaltic rock. The polymictic
"chondritic breccia" (Fig. 5B, C) forms the crust of a
slightly vesicular basalt while conversely the
polymictic, metal-rich "achondritic breccia" has a
vesicular basaltic crust (Fig. 5A). Resembling the
"achondritic breccia" a distinct group of pebbles
abundantly found in the field has a regmaglyptic
1610.pdf49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083)

sculpture, varying metal content and brazen yellow
granulous patina (Fig. 6C). Eye-catching are sharp-
edged basalt samples with fusion crust that must have
formed after fracturing (Fig. 6A), and samples with
regmaglyptic sculpture (Fig 6B).
Fig. 4. Special types of melt rock from the Niederrhein
deposit (see text).
Fig. 5. "Chondritic" and "achondritic" breccias in
contact with basaltic rock (see text).
Fig. 6. A: Fusion crust coating sharp-edged fractured
basaltic rock. B: Regmaglyptic sculpture. C:
"Achondritic" pebbles (see text).
Fig. 7. Various formations of native iron in basalt. sed
= sedimentary breccia material contacting and
intruding a basaltic cobble.
The native iron in the form of spherules and
irregularly shaped particles shows a broad spectrum of
size (micrometers up to centimeters) and distribution
within the sampled rocks (basaltic matrix and fusion
crust, Fig. 7, 3E).
Looking into the samples - SEM-EDS and
petrographic slides: Preliminary results of SEM
analyses of a basaltic melt rock (Fig. 8) with metallic
inclusions show an extremely complex composition,
and it is not always conclusive for now whether we are
dealing with original basaltic matter or recrystallized
melt rock. In a small segment of the sample the EDS
Mapping Image (Fig. 8) basically distinguishes three
different fields: metallic inclusions composed of Fe,
Ni, Cr and Mn (a), mineral grains belonging to the
spinel group (b, mostly Cr-Mn spinel), and mineral
grains near the pyroxene group (c). Spectra from other
spots in the samples may reveal considerably different
composition. Likewise, studies of thin sections of other
samples from the deposit show strong variations of the
mineralogical composition.
Fig. 8. EDS analysis of a basaltic melt rock (see text).
In the basaltic matter typical shock-metamorphic
effects are frequently observed in feldspars in the form
of diaplectic glass (maskelynite) and planar
deformation features (PDF) (Fig. 9B, C). Diaplectic
silica glass from former quartz grains as a strong shock
indicator is found in the sedimentary matter contacting
basaltic samples (Fig. 9A).
Fig. 9. Photomicrographs of shock metamorphism.
Quartz (A) and feldspar (B) grains completely
transferred to diaplectic glass, plane light and crossed
polarizers. C: Multiple sets of planar deformation
features (PDF) in feldspar, plane light.
Conclusions: The presented material suggests a
hitherto unseen major geologic alien element in the
Niederrhein region primarily based on the ample
occurrence of native iron-bearing basaltic melt rocks
completely detached from any known basalt deposit up
to a distance of 100 km. An origin as basaltic
meteorites and achondrites with few attached
chondritic matter from Moon, Mars or an asteroid
(e.g., Vesta with a basaltic crust) appears reasonable
[2] if we assume that the samples were originally
launched from the Moon or other cosmic bodies by
impacts, which explains the melt and breccia texture
and the shock effects in the samples [3]. Details of this
proposed event remain enigmatic because a simple
meteorite fall does not match some observations.
These are, e.g., the often intertwined sedimentary and,
hence, probably terrestrial rock components (Fig. 4, 7)
with in part strong shock effects suggesting a related
terrestrial impact event that from the local geologic
stratigraphy should have happened in the Middle-
Pleistocene (Cromer) about 600 ka BP. The search for
a related morphological impact signature is at the
beginning, and the forthcoming fieldwork will also
include possible industrial and archeological aspects of
the finds. An Ar-Ar dating has been initiated which
could significantly substantiate our hypothesis.
References: [1] Bird, J.M. et al. (1981) J. Geophys.
Res., 86, 11787-805. [2] https://curator.jsc.nasa.gov/
antmet/lmc/lmc.cfm, accessed 1/6/18. [3] Martin et al.
(2017) Meteoritics Planet. Sci., 52, 1103-1124.
1610.pdf49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083)