Statistical Analysis of Directional Features - Geomathematics: Theoretical Foundations, Applications and Future Developments - page 293

Fig. 8.16 Complex structures of superimposed folding in Pusteria tectonites, northern Italy (After
Agterberg 1961 ). Pattern of mean azimuth and dip of minor fold axes were constructed by
averaging for domains and manual contouring. Frame of Fig. 8.17 is outlined (Source: Agterberg
1974 , Fig. 113)

regional average orientation change. The major D2-deformation occurred in the late
Carboniferous and was connected to mainly subhorizontal Hercynian tectonic
movements associated with greenschist facies metamorphism ( cf . Ring and Richter
1994 , p. 765). During Alpine orogeny, S2 assumed its current predominantly
southward dip In the Brixen area.

8.2.4 Pustertal Tectonites Example

Figure 8.16 (after Agterberg 1961 , 1974 ; also see Whitten 1966 ) shows mean
azimuth lines and average dips of B-axes for measurement samples similar to
those shown in Fig. 8.12 in the Pustertal East of Bruneck. As in the immediate
vicinity of Bruneck, the quartzphyllites ( cf . Fig. 8.5 ) are rather strongly folded in
many places. Although B-axis orientations could be measured in about 1,700
outcrops, representative schistosity-plane readings were obtained in 257 outcrops
only. In nearly half of these outcrops, s -plane attitude is subvertical (dips between
75 northwards and 75 southwards; Agterberg 1961 , Fig. 58) although lesser
northern dips ( 75 ). Thus,

the mean azimuth lines in Fig. 8.16 approximately represent mean schistosity-plane
strikes. On the whole, the mean azimuth lines converge eastward. Relatively strong
local convergence occurs on the Eggerberg East of Welsberg (Fig. 8.16 ). Measure-
ments taken along the south slope of the East-West elongated Eggerberg show
SW-NE strikes and mean azimuths on the average but on its less exposed north
slope NW-SE strikes prevail. Figure 8.17 (after Agterberg 1974 ) shows best-fitting
two-dimensional quadratic and cubic polynomial unit vector fields for the
Eggerberg and its immediate surroundings. Strong eastward convergence of azi-
muth lines (Eggerberg structure) in Fig. 8.17 indicates existence of neo-Alpine
anticlinal lineament or zone along which material moved upwards with consider-
able mobility but with preservation of mean attitudes of subvertical s -planes and
B-axes (after Agterberg 1974 , Fig. 115). The cubic solution is probably more

75 ) are slightly more prevalent than southern dips ( < <