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GeoBioScience: Red Wood Ants as Bioindicators for Active Tectonic Fault Systems in the West Eifel (Germany).

Berberich G, Schreiber U - Animals (Basel) (2013)

Bottom Line: The results showed linear alignments and clusters of approx. 3,000 RWA mounds.A possible cause can be found in occasionally occurring H₂S in the fault systems, which is toxic at miniscule concentrations to the ants.Viewed overall, there is a strong relationship between RWA mounds and active tectonics in the West Eifel.

View Article: PubMed Central - PubMed

Affiliation: Department of Geology, Faculty of Biology, University of Duisburg-Essen, Universitätsstr. 5, 45141 Essen, Germany. gabriele.berberich@uni-due.de.

ABSTRACT
In a 1.140 km² study area of the volcanic West Eifel, a comprehensive investigation established the correlation between red wood ant mound (RWA; Formica rufa-group) sites and active tectonic faults. The current stress field with a NW-SE-trending main stress direction opens pathways for geogenic gases and potential magmas following the same orientation. At the same time, Variscan and Mesozoic fault zones are reactivated. The results showed linear alignments and clusters of approx. 3,000 RWA mounds. While linear mound distribution correlate with strike-slip fault systems documented by quartz and ore veins and fault planes with slickensides, the clusters represent crosscut zones of dominant fault systems. Latter can be correlated with voids caused by crustal block rotation. Gas analyses from soil air, mineral springs and mofettes (CO₂, Helium, Radon and H₂S) reveal limiting concentrations for the spatial distribution of mounds and colonization. Striking is further the almost complete absence of RWA mounds in the core area of the Quaternary volcanic field. A possible cause can be found in occasionally occurring H₂S in the fault systems, which is toxic at miniscule concentrations to the ants. Viewed overall, there is a strong relationship between RWA mounds and active tectonics in the West Eifel.

No MeSH data available.


Related in: MedlinePlus

Spatial distributions of RWA (red dots) (a), manually inferred RWA Lineaments (grey lines) (b) combined with published tectonic features like faults (red lines), eruption fissures (blue lines) and mineral springs (blue dots) and results of the modified Hough Transform (c) for the Oberehe site. For the RWA cluster at the Dockweiler Wald area (d), manually inferred RWA lineaments (grey lines) and mineral springs (blue dots) (e) and results of the modified Hough Transform (f) are presented.
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animals-03-00475-f010: Spatial distributions of RWA (red dots) (a), manually inferred RWA Lineaments (grey lines) (b) combined with published tectonic features like faults (red lines), eruption fissures (blue lines) and mineral springs (blue dots) and results of the modified Hough Transform (c) for the Oberehe site. For the RWA cluster at the Dockweiler Wald area (d), manually inferred RWA lineaments (grey lines) and mineral springs (blue dots) (e) and results of the modified Hough Transform (f) are presented.

Mentions: At the Oberehe site (cf.Figure 10(a)), the most preferential alignment directions of RWA Lineaments (cf.Figure 10(b)) manually inferred from the tectonic history, geological field work and experiences, and soil gas sampling are the reactivated Variscan fault systems NNE-SSW (approx. 20°) and NE-SW (40°–50°) and the opening direction of the Quaternary volcanic field in NW-SE (approx. 145°) direction. This result correlates well with a modified Hough transform method [74] applied on the RWA mound distribution (cf.Figure 10(c)). In two consecutive steps, all possible directions were extracted from the RWA mound positions first. For each mound pair a corresponding line was constructed. Then the distance of all mounds from the line was computed. Hereafter, the orientation of the extracted directions were binned in a histogram. The most preferential alignment directions are NNE-SSW (18°), NW-SE (171°) and strikingly NE-SW (39°–63°). The NE-SW direction might be caused by small-scale rotation of the stress field due to block rotation. Clusters of RWA mounds typically represent crosscut zones of different fault systems. An example is given by the RWA cluster within the Dockweiler Wald (cf.Figure 10(d)), where 150 RWA mounds occurred on 1 km² only. Compared to the Oberehe site, the Dockweiler Wald RWA cluster showed manually inferred RWA Lineaments in NNE-SSW (approx. 20°), NE-SW (approx. 50–60°), WNW-ESE (approx. 110°), NW-SE (approx. 125°) and N-S (approx. 175°) direction (cf.Figure 10(e)). The results of the Hough transform showed similar directions: N-S (0°), NNE-SSW (39°), NE-SW (48°–63°), WNW-ESE (99°), NW-SE (126°) and NNW-SSE (165°–175°) (cf.Figure 10(f)).


GeoBioScience: Red Wood Ants as Bioindicators for Active Tectonic Fault Systems in the West Eifel (Germany).

Berberich G, Schreiber U - Animals (Basel) (2013)

Spatial distributions of RWA (red dots) (a), manually inferred RWA Lineaments (grey lines) (b) combined with published tectonic features like faults (red lines), eruption fissures (blue lines) and mineral springs (blue dots) and results of the modified Hough Transform (c) for the Oberehe site. For the RWA cluster at the Dockweiler Wald area (d), manually inferred RWA lineaments (grey lines) and mineral springs (blue dots) (e) and results of the modified Hough Transform (f) are presented.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4494391&req=5

animals-03-00475-f010: Spatial distributions of RWA (red dots) (a), manually inferred RWA Lineaments (grey lines) (b) combined with published tectonic features like faults (red lines), eruption fissures (blue lines) and mineral springs (blue dots) and results of the modified Hough Transform (c) for the Oberehe site. For the RWA cluster at the Dockweiler Wald area (d), manually inferred RWA lineaments (grey lines) and mineral springs (blue dots) (e) and results of the modified Hough Transform (f) are presented.
Mentions: At the Oberehe site (cf.Figure 10(a)), the most preferential alignment directions of RWA Lineaments (cf.Figure 10(b)) manually inferred from the tectonic history, geological field work and experiences, and soil gas sampling are the reactivated Variscan fault systems NNE-SSW (approx. 20°) and NE-SW (40°–50°) and the opening direction of the Quaternary volcanic field in NW-SE (approx. 145°) direction. This result correlates well with a modified Hough transform method [74] applied on the RWA mound distribution (cf.Figure 10(c)). In two consecutive steps, all possible directions were extracted from the RWA mound positions first. For each mound pair a corresponding line was constructed. Then the distance of all mounds from the line was computed. Hereafter, the orientation of the extracted directions were binned in a histogram. The most preferential alignment directions are NNE-SSW (18°), NW-SE (171°) and strikingly NE-SW (39°–63°). The NE-SW direction might be caused by small-scale rotation of the stress field due to block rotation. Clusters of RWA mounds typically represent crosscut zones of different fault systems. An example is given by the RWA cluster within the Dockweiler Wald (cf.Figure 10(d)), where 150 RWA mounds occurred on 1 km² only. Compared to the Oberehe site, the Dockweiler Wald RWA cluster showed manually inferred RWA Lineaments in NNE-SSW (approx. 20°), NE-SW (approx. 50–60°), WNW-ESE (approx. 110°), NW-SE (approx. 125°) and N-S (approx. 175°) direction (cf.Figure 10(e)). The results of the Hough transform showed similar directions: N-S (0°), NNE-SSW (39°), NE-SW (48°–63°), WNW-ESE (99°), NW-SE (126°) and NNW-SSE (165°–175°) (cf.Figure 10(f)).

Bottom Line: The results showed linear alignments and clusters of approx. 3,000 RWA mounds.A possible cause can be found in occasionally occurring H₂S in the fault systems, which is toxic at miniscule concentrations to the ants.Viewed overall, there is a strong relationship between RWA mounds and active tectonics in the West Eifel.

View Article: PubMed Central - PubMed

Affiliation: Department of Geology, Faculty of Biology, University of Duisburg-Essen, Universitätsstr. 5, 45141 Essen, Germany. gabriele.berberich@uni-due.de.

ABSTRACT
In a 1.140 km² study area of the volcanic West Eifel, a comprehensive investigation established the correlation between red wood ant mound (RWA; Formica rufa-group) sites and active tectonic faults. The current stress field with a NW-SE-trending main stress direction opens pathways for geogenic gases and potential magmas following the same orientation. At the same time, Variscan and Mesozoic fault zones are reactivated. The results showed linear alignments and clusters of approx. 3,000 RWA mounds. While linear mound distribution correlate with strike-slip fault systems documented by quartz and ore veins and fault planes with slickensides, the clusters represent crosscut zones of dominant fault systems. Latter can be correlated with voids caused by crustal block rotation. Gas analyses from soil air, mineral springs and mofettes (CO₂, Helium, Radon and H₂S) reveal limiting concentrations for the spatial distribution of mounds and colonization. Striking is further the almost complete absence of RWA mounds in the core area of the Quaternary volcanic field. A possible cause can be found in occasionally occurring H₂S in the fault systems, which is toxic at miniscule concentrations to the ants. Viewed overall, there is a strong relationship between RWA mounds and active tectonics in the West Eifel.

No MeSH data available.


Related in: MedlinePlus