Astronomy and Astrophysics – Astronomy
Scientific paper
May 1998
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998geoji.133..245e&link_type=abstract
Geophysical Journal International, Volume 133, Issue 2, pp. 245-259.
Astronomy and Astrophysics
Astronomy
8
Crust, Saxonian Granulites, Seismic Modelling, Seismic Refraction, Variscan Orogeny
Scientific paper
In this paper we present newly acquired high-quality wide-angle seismic data of the GRANU95 project and first models of the crustal structure along two profiles (95-A and 95-B) beneath the Saxonian Granulites, a major ellipse-shaped exposure of lower-crustal material within the mid-European Variscan belt in southeastern Germany (Saxony). The crust is subdivided into four layers. The crystalline basement with velocities higher than 6.0kms-1 is generally reached at shallow depths, with three major sedimentary structures as prominent exceptions where velocities considerably lower than 6.0kms-1 (as low as 5.1kms-1 ) reach as deep as 4km. The highest upper-crustal velocities (up to 6.5kms-1 ) are not seen below the exposed granulites themselves, but at shallow depths (4km) SW of the exposure. These shallow high velocities correlate well in depth with highly reflective zones observed on three seismic-reflection lines of DEKORP (85-4N, 95-01, 95-02) at their intersection with the seismic-refraction line 95-B, where they appear as a set of NW-SE-trending dome-shaped reflections. On profile 95-A this high-velocity upper-crustal layer (6.3kms-1 ) dips from 5 to 9km beneath the SE margin of the exposed granulites. These results suggest that the granulite dome and its western continuation are widely underlain by a NE-trending antiformal structure (probably a sheet of metabasic rocks) where the exposed felsic granulites form just a local cap on top. Below the upper-crustal high velocities, a layer with decreased velocity (6.2-6.25kms-1 ) extends down to an average depth of 15km along the Variscan strike (95-B) and to 11-16km depth (slightly dipping towards the SE) perpendicular to the terrane boundaries (95-A). At mid-crustal levels a weak reflection from a layer with a velocity of 6.4-6.6kms-1 may indicate the classical Conrad discontinuity. At the depth range 22-24km the velocity jumps to an average value of 7.0kms-1, thus defining a prominent high-velocity layer in the lower crust, which may be viewed as the well-known laminated lower crust typical of Variscan structures, but with higher average velocity than usually detected. The crust-mantle boundary at about 30-31km is typical for western Europe and confirms the extensional signature of the West European crust. Below the Moho, poorly constrained upper-mantle velocities of about 7.9-8.0kms-1 are derived. The high velocities observed in the lower-crustal layer would not exclude the possibility of mantle-derived intrusions, but the lack of any sign of an updoming Moho favours the interpretation of a more passively driven extension.
Bribach J.
Enderle U.
Prodehl Claus
Schulze Achim
Schuster Cosima
No associations
LandOfFree
The refraction seismic experiment GRANU95 in the Saxothuringian belt, southeastern Germany does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The refraction seismic experiment GRANU95 in the Saxothuringian belt, southeastern Germany, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The refraction seismic experiment GRANU95 in the Saxothuringian belt, southeastern Germany will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1369115