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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

RWA Lineaments (grey lines) (a) combined with published tectonic features like Quaternary eruption fissures (blue lines) (b), lineament analyses of tectonically active faults (green lines) (c) and fault systems (red lines) (d) without any differentiation between inactive and active fault systems, for the entire study area.
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animals-03-00475-f012: RWA Lineaments (grey lines) (a) combined with published tectonic features like Quaternary eruption fissures (blue lines) (b), lineament analyses of tectonically active faults (green lines) (c) and fault systems (red lines) (d) without any differentiation between inactive and active fault systems, for the entire study area.

Mentions: For the Oberehe site, the maximum Helium concentration [ppb] (cf.Figure 11) for a given distance x from the closest fault clearly shows a decreasing trend with increasing value of x. High He concentrations only occur in close proximity to the faults. The comparison of both the spatial RWA mound distribution with the significantly increased geogenic gas anomalies that are controlled by macro- and micro-scale brittle deformation confirms that the RWA colony is situated in a tectonically sheared region. Their preferential linear alignment directions directly match tectonically active, gaspermeable strike-slip faults (cf.Figure 12(a)). Although the Oberehe reference site is surrounded by various forest stands, no further RWA mounds were found in those forest stands during the area-wide mapping. Clusters of RWA mounds typically represent crosscut zones of different fault systems. Analysis of their internal structures will similarly lead to linear alignments that depict a more complex tectonic situation, i.e., voids or a transtensional/transpressional regime at that site. Another prominent example are the three large clusters of the F. rufa supercolony at the Bodanrück (South-West Germany), where within the clusters diffuse degassing of geogenic tracer gases occurs [65,66]. Solitary RWA mounds can be found mostly at unusual locations with spotty degassing and are links between linear alignments and cluster structures. For myrmecologists, the causes and stringency of such a linkage are paramount, since linear patterns have been mostly associated with edge effects of forest stands and/or roads [48,49]. But [40] already stated in 1929 that there are no preferred locations of RWA mounds within a forest stand. This is strengthened by statistical analyses, which show that spatial distribution of RWA map tectonically active, gaspermeable strike-slip faults [31].


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

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

RWA Lineaments (grey lines) (a) combined with published tectonic features like Quaternary eruption fissures (blue lines) (b), lineament analyses of tectonically active faults (green lines) (c) and fault systems (red lines) (d) without any differentiation between inactive and active fault systems, for the entire study area.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

animals-03-00475-f012: RWA Lineaments (grey lines) (a) combined with published tectonic features like Quaternary eruption fissures (blue lines) (b), lineament analyses of tectonically active faults (green lines) (c) and fault systems (red lines) (d) without any differentiation between inactive and active fault systems, for the entire study area.
Mentions: For the Oberehe site, the maximum Helium concentration [ppb] (cf.Figure 11) for a given distance x from the closest fault clearly shows a decreasing trend with increasing value of x. High He concentrations only occur in close proximity to the faults. The comparison of both the spatial RWA mound distribution with the significantly increased geogenic gas anomalies that are controlled by macro- and micro-scale brittle deformation confirms that the RWA colony is situated in a tectonically sheared region. Their preferential linear alignment directions directly match tectonically active, gaspermeable strike-slip faults (cf.Figure 12(a)). Although the Oberehe reference site is surrounded by various forest stands, no further RWA mounds were found in those forest stands during the area-wide mapping. Clusters of RWA mounds typically represent crosscut zones of different fault systems. Analysis of their internal structures will similarly lead to linear alignments that depict a more complex tectonic situation, i.e., voids or a transtensional/transpressional regime at that site. Another prominent example are the three large clusters of the F. rufa supercolony at the Bodanrück (South-West Germany), where within the clusters diffuse degassing of geogenic tracer gases occurs [65,66]. Solitary RWA mounds can be found mostly at unusual locations with spotty degassing and are links between linear alignments and cluster structures. For myrmecologists, the causes and stringency of such a linkage are paramount, since linear patterns have been mostly associated with edge effects of forest stands and/or roads [48,49]. But [40] already stated in 1929 that there are no preferred locations of RWA mounds within a forest stand. This is strengthened by statistical analyses, which show that spatial distribution of RWA map tectonically active, gaspermeable strike-slip faults [31].

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