622
12.7 Collision-Related Basins
12.7.1 General Characteristics
12.7.2 Intramontane basins
12.7.3 Basins Resulting from Continental Extrusion
12.7.4 Pannonian-Type Basins
General Aspects
The Pannonian basin
Structural Evolution
Sediment Successions
The Aegean Sea
12.7.5 Summary (Collision-Related Basins)
12.7.1 General Characteristics
Continental eollision ereates several types of basins
whieh may be relative1y eomplex and variable. The
most important types have been mentioned in Seet.
1.2 (cf. Fig. 1.3). Theyare:
- Foreland basins (cf. Seet. 12.6.2).
- Intramontane basins.
- Basins resulting from eontinental extrusion.
- Pannonian-type basins.
A c1ear separation of these groups is not possible
beeause all of them are related to eontinental eollision. Furthermore, there are transitions from these
groups to retroare basins and pull-apart basins. Continental eseape (or extrusion) ean lead to both
transpression and transtension (cf. Seet. 12.8) and
thus to pull-apart or wreneh basins as well as rift basins.
12.7.2 Intramontane basins
These basins oeeur in all orogenie fold and thrust
belts and mark a late stage in mountain building. The
basins primarily evolve by extension as narrow
troughs within and behind thrust belts on top of the
overriding plate. Some basins develop on the top of
overthust belts (wedge top basins, piggy-baek basins;
cf. Fig. l2.34d and Seet. 12.6.2). Most of these
graben-like struetures run parallel to the strike of the
orogenie belt, others develop as grabens oblique or
normal to strike due to orogenie eollapse and eontinental eseape. Many of these basins are also affeeted
Chapter 12 Basin Evolution and Sediments
by syn- and post-depositional eompression, overthrusting, and strike-slip.
The sedimentary fills of intramontane basins ean
be coastal to shallow-marine in an early phase when
the sea intrudes along the topographie depressions.
Then the marine sediments tend to pass upward into
fluvial and alluvial deposits. More frequently, the
entire basin fills are non-marine and may reeord an
extensional (basin opening) phase by a fining-upward megasequenee, followed by a eoarsening-upward megasequenee assoeiated with a eompressional
phase and partial basin c1osing. High-relief sediment
sources nearby ean deliver large amounts of grave1and sand-size material and thus rapidly fill the basins. In some basins, eoal seams are present whieh
formed during times of temperate wet c1imate and
redueed sediment supply. Various voleanie rocks and
voleanielasties eontribute to the sediment fills of
these basins.
Intramontane basins have been deseribed, e.g.,
from the Alps, the Himalayas, the Andes, and other
Alpidie and older mountain belts. In the following,
some young examples from South Ameriea and
Permo-Carboniferous representatives of the European Varisean belt are introdueed.
Andes of Ecuador, Peru, and Bolivia. Intramontane basins have evolved between the Eastern and Western Cordillera, in the so-called inter-Andean Valley, High Plateau or
Altiplano (Marocco et al. 1995). These basins were initiated by the reactivated Andean tectonism in the late
Oligocene and reflect a change in the overall stress fie1d
from NNE-SSW (causing transtension) to E-W (compression, synsedimentary deformation, reverse faulting and
uplift, Fig. 12.39c). This is indicated by fining- and
coarsening-upwan.l megasequences and the occurrence of
unconformities. Volcaniclastics playa major part in the
basin fillings, but lacustrine deposits mayaiso be present.
Oligocene to Miocene wedge-top basins of the Eastern
Cordillera in southern Bolivia have been described by Horton (1998). Backthrusting, fault propagation and folds isolated individual basins, which originally developed above
the toe of the orogenie wedge (Fig. 12.39d,e). Now, the
basins are located far west of the active thrust front.
Some present-day lake basins, such as the large Lake
Titicaca in Peru/Bolivia and the sediment-filled and
fluvially dissected Lauca basin of northern Chile (Kött et
al. 1995; Gaupp et al. 1999) belong to this basin type.
Lauca basin, Chile. This is a half-graben and contains a
Miocene-Pliocene section which records several extra- and
intra-basinal volcanic events and climate changes from less
arid to markedly arid conditions. The alluvial-fluvial-Iacus-
12.7 Collision-Related Basins
12.7.1 General Characteristics
12.7.2 Intramontane basins
12.7.3 Basins Resulting from Continental Extrusion
12.7.4 Pannonian-Type Basins
General Aspects
The Pannonian basin
Structural Evolution
Sediment Successions
The Aegean Sea
12.7.5 Summary (Collision-Related Basins)
12.7.1 General Characteristics
Continental eollision ereates several types of basins
whieh may be relative1y eomplex and variable. The
most important types have been mentioned in Seet.
1.2 (cf. Fig. 1.3). Theyare:
- Foreland basins (cf. Seet. 12.6.2).
- Intramontane basins.
- Basins resulting from eontinental extrusion.
- Pannonian-type basins.
A c1ear separation of these groups is not possible
beeause all of them are related to eontinental eollision. Furthermore, there are transitions from these
groups to retroare basins and pull-apart basins. Continental eseape (or extrusion) ean lead to both
transpression and transtension (cf. Seet. 12.8) and
thus to pull-apart or wreneh basins as well as rift basins.
12.7.2 Intramontane basins
These basins oeeur in all orogenie fold and thrust
belts and mark a late stage in mountain building. The
basins primarily evolve by extension as narrow
troughs within and behind thrust belts on top of the
overriding plate. Some basins develop on the top of
overthust belts (wedge top basins, piggy-baek basins;
cf. Fig. l2.34d and Seet. 12.6.2). Most of these
graben-like struetures run parallel to the strike of the
orogenie belt, others develop as grabens oblique or
normal to strike due to orogenie eollapse and eontinental eseape. Many of these basins are also affeeted
Chapter 12 Basin Evolution and Sediments
by syn- and post-depositional eompression, overthrusting, and strike-slip.
The sedimentary fills of intramontane basins ean
be coastal to shallow-marine in an early phase when
the sea intrudes along the topographie depressions.
Then the marine sediments tend to pass upward into
fluvial and alluvial deposits. More frequently, the
entire basin fills are non-marine and may reeord an
extensional (basin opening) phase by a fining-upward megasequenee, followed by a eoarsening-upward megasequenee assoeiated with a eompressional
phase and partial basin c1osing. High-relief sediment
sources nearby ean deliver large amounts of grave1and sand-size material and thus rapidly fill the basins. In some basins, eoal seams are present whieh
formed during times of temperate wet c1imate and
redueed sediment supply. Various voleanie rocks and
voleanielasties eontribute to the sediment fills of
these basins.
Intramontane basins have been deseribed, e.g.,
from the Alps, the Himalayas, the Andes, and other
Alpidie and older mountain belts. In the following,
some young examples from South Ameriea and
Permo-Carboniferous representatives of the European Varisean belt are introdueed.
Andes of Ecuador, Peru, and Bolivia. Intramontane basins have evolved between the Eastern and Western Cordillera, in the so-called inter-Andean Valley, High Plateau or
Altiplano (Marocco et al. 1995). These basins were initiated by the reactivated Andean tectonism in the late
Oligocene and reflect a change in the overall stress fie1d
from NNE-SSW (causing transtension) to E-W (compression, synsedimentary deformation, reverse faulting and
uplift, Fig. 12.39c). This is indicated by fining- and
coarsening-upwan.l megasequences and the occurrence of
unconformities. Volcaniclastics playa major part in the
basin fillings, but lacustrine deposits mayaiso be present.
Oligocene to Miocene wedge-top basins of the Eastern
Cordillera in southern Bolivia have been described by Horton (1998). Backthrusting, fault propagation and folds isolated individual basins, which originally developed above
the toe of the orogenie wedge (Fig. 12.39d,e). Now, the
basins are located far west of the active thrust front.
Some present-day lake basins, such as the large Lake
Titicaca in Peru/Bolivia and the sediment-filled and
fluvially dissected Lauca basin of northern Chile (Kött et
al. 1995; Gaupp et al. 1999) belong to this basin type.
Lauca basin, Chile. This is a half-graben and contains a
Miocene-Pliocene section which records several extra- and
intra-basinal volcanic events and climate changes from less
arid to markedly arid conditions. The alluvial-fluvial-Iacus-