THE SAARLOUIS SEMI CRATER STRUCTURE: NOTABLE INSIGHT INTO THE SAARLAND (GERMANY) METEORITE IMPACT EVENT ACHIEVED
Kord Ernstson1, Werner Müller2, Andreas Gawlik-Wagner3
1Faculty of Philosophy I, University of Wurzburg, Germany ̈ 266809 Nalbach, Germany , 366763 Dillingen, Germany
Berlin
Köln
München
100 km
Saarlouis
Saarland impact
France
Dillingen
Nalbach
Saarlouis
Wallerfangen
Altforweiler
A 8
A 8
A 6201 km
semi crater
impact field
Nalbach crater
The Nalbach impactite strewn field and crater
Shock metamorphism, melt rocks and glasses in
the Nalbach impactite strewn fieldthin sections, photomicrographs; crossed polarizers (XX) and plane light (II).
Quartzite cobble completely transferred to diaplectic glass; XX and II.
Diaplectic sanidine crystals in diaplectic quartzite glass; XX and II.
Ballen structures in silica; XX and II.
Ballen structures merging in cristobalite and tridymite; XX and II.
Multiple sets of planar fractures (PF) and spots of diaplectic glass in quartz; XX.
Planar deformatiom features (PDF) in quartz; XX.
Strongly kinked mica (XX) and "toasted" quartz (II).
Multiple sets (white) of planar features in mica.
Strong shock meta-morphism as in proof of meteorite impact.
50 µm
50 µm
200 µm
electron images
CFe
Fe, O
C
500 µm
layeredimageLocation map for the Saarland meteorite impact event (to the
left): the Nalbach impactite strewn field established a few years ago and the recently discovered Saarlouis semi impact crater (to
the right).
Impact glasses in the Nalbach strewn field
Impact melt rocks in the Nalbach strewn field
The Saarlouis semi crater
Archeological excavation and find of impactites below foundations of a Romanesque church.
Digital Terrain Model (DGM 1): The 200 m-diameter (rim crest) Nalbach crater.
Ti Mn Fe
Suevite, SEM-EDS: iron-metallic spherules in basaltic-andesitic melt rock clasts.
S KCa
C OMg
Al SiP
mostly anorthite, also orthoclase, Mn-Mg pyroxene, andalusite?
Suevite breccia from the crater rim.
clast size grading and alignmentindicate flow texture
shock PDF in feldspar and quartz
500 µm
native iron spherule with carbon filaments
native iron spherules and andalusite re-crystallization(?)
vesicular iron - meltrock clast
Impact melt rock excavated during gas pipeline burying.
Melt rock matrix with moderately shocked quartz grains (q; and photomicrographs to the right) having obviously survived impact shock melting. Thin section photomicrographs, crossed polarizers.
1 mm
q
q
q
qcut face
1 cm
2 cm
Most larger quartz grains show multiple sets of planar fractures (PF) and fainter planar deformation features (PDF).Thin section
photomicrographs, crossed polarizers; field widths 150 µm.
2 cm
open spallation fissures filled with glass
2 cm
bone splinters in glass2 cm
mmscale
1 cm
1 cm
1 cm
Two quartz grains with open tensile, glass-filled spallation fractures
100 µm
200 µm
100 µm
100 µm
100 µm
100 µm
100 µm
400 µm
150 µm150 µm
fractured quartz grainsalmost pulverized
quartz, glass-filled open fractures
200 µm
1 cm
1 cm
after Google Earth
The Saarlouis semi crater: The rim wall crest (+) is forming a segment of a nearly perfect 2.3 km-diameter circle (to the left).
Geological map; simplified from Geoportal.saarland.de (to the right).
Map of shaded relief of the Digital Terrain Model (DTM) and profiles across the rim wall. For comparison other typical crater profiles are
shown. DTM data from LVGL Saarland.
The Saarland impact event - discussion and conclusions
The Saarlouis semi crater - meteorite impact evidence
-- The strong and widely distributed shock metamorphism, the impact glasses, the impact melt rocks and a suevite polymictic breccia establish a proven meteorite impact event near the German-French frontier. The discovery goes back to field observations and sampling by the coauthors W. M. and A. G.
-- So far two impact craters with diameters of 200 m (Nalbach) and 2.3 km (Saarlouis) and a classically countoured rim wall have been identified. Both are in part eroded to feature rather semi craters.
-- The widely distributed near-surface strongly shocked impactites are considered ejected material or/and restored by fluvial transport.
-- Impactites at 2 m depth excavated together with human bones from below the foundations of a Romanesque church in Nalbach exclude any anthropogenic/industrial products.
-- SEM-EDS analyses of suevite composition and formation remain puzzling and require more detailed studies of the in part igneous impact target not exposed in the investigated area.
-- According to the Lower Terrace sediments at the bottom of the Saarlouis semi crater the age of the impact event is Pleistocene or older.
Reference: Buchner, E. et al. (2011) 74th Ann. Meteoritical Soc. Meeting, Abstract #5048. Schmieder, M. et al. (2011). 74th Ann. Meteoritical Soc. Meeting. Abstract #5059. Ernstson, K. et al. (2013) Meteoritics & Planet. Sci., 48, s1, Abstract #5058. Berger, N. (2014) Diploma thesis, University of Trier. Berger, N. et al. (2015) 46th LPSC, Abstract #1255.