Guidebook - Ispra

Volume n° 1 - from PR01 to B15
B12
B12 -
Leader: M. Sandulescu
morphism in prehnite-pumpellyite facies. Other secondary
minerals of the sheared rocks include chlorite,
epidote, albite, calcite and zeolites. The structural
elements of the ophiolites consist of slickensides and
S-C fabrics, with a penetrative scaly-cleavage. Flat
lying banded mylonites develop on basalt protoliths
along the western border of the nappe. Sheared green
rocks are traversed by epidote-quartz-albite veins (A.
Seghedi, in Berza et al., 1994).
The road continues across Neogene formations till
Drobeta -Turnu Severin. This town was built at the
emplacement of Trajan’s bridge over the Danube (105
A.D.), one pillar of which can still be seen. Medieval
ruins can also be visited.
DAY 7
Turnu Severin - Timișoara
Stop 7.1:
3.5 km west of Gura Văii, km 352, between the
Scarpia (Padina Mică) and Ungureanu viaducts.
Pre-Alpine polymetamorphic basement of the
Getic Nappe: Lotru Group.
The road crosses the Iron Gate outlier of the Getic
Nappe, on which the Iron Gate Dam is built. The
Lotru Group consists of metaterrigeneous micaceous
paragneisses and micaschists associated with
amphibolites, quartz-feldspar gneisses and scarce
marble lenses. The outcrops display up to three fold
generations, S 1 layering, S 2 dominanat transposition
foliation and a S 3 crenulation cleavage, mineral and
intersection lineations.
Relict mineral assemblages (biotite, garnet, staurolite,
kyanite) characterizing a first barrovian metamorphism
M1 are overprinted by a sillimanite + biotite +
muscovite association M2 of intermediate low-pressure
type. The dominant S2 foliation has a general
NE-SW attitude, while the mineral (stretching) lineations
lie between ENE and ESE.
The Iron Gates outlier of the Getic Nappe crosses the
Danube southwards into Serbia (Sip) (V. Iancu, in:
Pop et al., 1997).
Stop 7.2:
Slătinicu Mare viaduct (km 354) and Oreva
viaduct (1.3 km westwards). Tectonic contact at
the sole of the Getic Nappe (Bahna outlier ) with
Lower Cretaceous turbidites (Sinaia Beds) of the
underlying Severin Nappe.
Metamorphites of the previously examined Lotru
Group, with small bodies of sheared diatexitic gran-
ites, overlie the Sinaia Beds, lying in the core of a
large scale open antiformal fold. On the eastern end of
the viaduct, the outcrop consists of crystalline schists
of the Lotru Group, while on its western end the Sinaia
Beds are exposed.
The Sinaia Beds include mostly distal turbidites;
thicker sandstone beds up to 40-50 cm occur in the
vicinity of the Slă˘tinicu Mare viaduct. Grey pelagic
limestones form thin interbeds. Chondritid ichnofauna
is often preserved in siltstones and mudstones. The
age of the sequence is ascribed to the Upper Tithonian-
Lower Valanginian, according to Calpionellids.
The structural style of the Sinaia Beds consists of tight
to isoclinal recumbent folds (B 1) strongly refolded
by steeply dipping normal folds (B 2). The recumbent
folds are strongly disrupted by normal folding and
they are often preserved as isolated dismembered fold
hinges. Various types of kink- and chevron-folds with
axial planes steeply dipping E or W are common.
Slaty cleavages are seldom visible in the pelitic interbeds.
Sandstone beds may show fracture cleavages
fanning in fold hinges. Younger structures are high
angle normal faults.
The relationships between the Lotru Group of the
Getic Nappe and the Sinaia Beds are exposed on
the right-hand bank of the Slătinic valley, where the
metamorphic rocks show pervasive brittle deformation.
The tectonic contact can be followed uphill,
where the metamorphic rocks of the Lotru Group
build up the top of the hills, while the road is cut
across sedimentary deposits. 300 m east of the Oreva
viaduct, strongly sheared and brecciated metamorphites
reappear in the core of a tight synformal fold;
a steeply dipping shear band foliation occurs in both
formations, several meters away from the contact (A.
Seghedi,V. Iancu, in : Berza et al., 1994; Pop et al.,
1997).
Stop 7.3:
Km 357, Vodiţa viaduct - Vârciorova viaduct. Tectonic
contact between the Severin Nappe and the
Danubian Domain.
At the confluence with the Vodiţa valley, the Lotru
Group is exposed.
The oldest sedimentary deposits exposed eastwards
are massive grey limestones strongly jointed and
crossed by numerous calcite veinlets, exhibiting in
places a pseudobreccia aspect. Their age is ascribed
to the Upper Jurassic-Lower Cretaceous, by comparison
with the Cerna-Coșuștea zone. These deposits
represent a huge olistolith embedded into a paratypi-