Abstract
Geology
Stratigraphically, the facies of the permo-triassic deposits
of the Merano area is closely connected with
that of the Southern Dolomites.
Structurally, the Merano region belongs to the southern
flank of the east-alpine geanticline. The southern
part of the alpine geanticline is cut in the Merano region
by a major fault with a southwest-northeast
trend, called Judicaria fault
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(fig. 2, p. 15).
In former syntheses of the structure of the Eastern
Alps, the Judicaria fault has generally been considered
as a sinistral transcurrent or wrench fault. This
transcurrent fault was assumed to have displaced the
suture line between the northern or alpine branch
sensu stricto and the southern or dinaric branch of
the Alpine Mountain System (sensu largo). The net
slip between the Insubric or Tonale line in the west
and the Pusteria-Drau line in the east would then be
about 80 km.
However, the structure and the analysis of the minor
tectonic features in the Merano area do not confirm
this concept. On account of the outcrop of the Judicaria
fault its present character is that of a steep upthrust
with a northwestern dip (fig. 27, sections I,ll,
VI, VII and IX, p. 38). However, according to the
tectonic features encountered close to the Judicaria
fault, this fault was originally a normal fault with a
southeastern dip (fig. 28, subphase b, p. 41). The vertical
component of the displacement of the fault
amounts to 5-9 km near the town of Merano.
The formation of the fault facilitated the diapiric ascent
of tonalitic magma, causing the emplacement of
the massifs of Monte Croce, Ivigna, and Bressanone
(fig. 28, subphase c). These plutonic masses belong
to the peri-adriatic series of tonalites, which most
probably, intruded during the mid-tertiary or insubric
phase of the alpine orogenesis. During the intrusion
of the tonalitic bodies the upper part of the Judicaria
fault assumed a steep northwestern dip, probably
because of a magma-tectonic mass-circuit (fig.
28, subphase c).
The geological data of the Merano area fit in with
van Bemmelen's concept of the east-alpine structural
evolution (van Bemmelen, 1957, 1960-b, 1960-c).
Paleomagnetism
A study was made of the paleomagnetic properties of
the permian quartz-porphyries occurring at the northwestern
margin of the Bolzano volcanic province.
Progressive partial demagnetization experiments on
orientated samples, by means of alternating magnetic
fields indicate that the remanent magnetization of the
quartz-porphyries is composed of two components,
namely a relatively unstable component, and a stable
component. The stable component probably represents
the original permian magnetization acquired
upon cooling of the volcanics. The unstable component
probably resulted from the induction of postpermian
magnetic fields. These secondary components
can be removed by exposing the samples to alternating
magnetic fields. This procedure of magnetic
"cleaning" greatly reduces the scatter of the primary
directions of magnetization.
The permian magnetic south pole position deduced
from the average direction of magnetization (declination
164°, inclination -7,5°) is 1460 Wand 45° N.
Though the latitude of this pole position is in agreement
with that of the poles inferred from other permian
rocks from the european continent, its longitude
deviates appreciably from that of the average european
permian pole position, namely about 40° (fig.
42, p. 53).
The following two possibilities for the cause of the
above mentioned deviation may be suggested:
The divergence of the north italian permian magnetic
pole might be the result of secular variation; but also
a geotectonic cause might be possible, for instance a
counter-clockwise rotation of the Merano region around
a vertical axis.
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