CARBONIFEROUS BLACK-SHALES
and SHALE-GAS POTENTIAL
in SOUTHWESTERN PORTUGAL
Paulo FONSECA
Nuno PIMENTEL
Rui PENA DOS REIS
Gabriel BARBERES
AAPG – Europe Region
Annual Conference & Exhibition
Post-Conference Field-trip
20th -21st May 2015
Field Trip Guide
Carboniferous Black-Shales
and Shale-Gas Potential in Southwestern Portugal
Paulo Fonseca
Nuno Pimentel
Rui Pena dos Reis
Gabriel Barberes
ISBN : 978-989-20-5741-5
CARBONIFEROUS BLACK-SHALES and SHALE-GAS
POTENTIAL IN SOUTHWESTERN PORTUGAL
This field trip will address the characterization and shalegas potential of Carboniferous units in southern Portugal.
Most of the trip will be along wild coastal cliffs and
beaches of the Southwest Coast Natural Park (PNSACV).
We will look at deep marine turbiditic sequences,
containing black-shales, affected by the variscan orogeny
and low-grade metamorphism. Maturation and
deformation issues are therefore crucial and will be
discussed.
We will also look at the Mesozoic cover, namely the
impressive Carboniferous-Triassic unconformity (Telheiro
beach) and Jurassic limestones (Carrapateira beach)
which may eventually act as potential reservoir units for
the Paleozoic gas. The trip will end with a short stop at
Ponta da Piedade, with karstic cliffs, natural grottoes and
arches.
Main topics to be adressed:
 Carboniferous black-shales – lithostratigraphy, sourcerock potential, maturation and deformation.
 Mesozoic cover - reservoir potential of Triassic red-beds
and Jurassic dolomites.
LIST OF PARTICIPANTS
Paulo Bizarro , Partex Oil and Gas
Arkadiusz Buniak, ORLEN Upstream Ltd.
Bizhu He, Chinese Academy of Geological Sciences
Roger Higgs, Geoclastica Ltd.
Nuno Ines, Partex Oil and Gas
Fraser Keppie, Nova Scotia Department of Energy
Piotr Krzywiec, Institute of Geological Sciences, PAS
Carolina Libório, Galp Energia
Gil Machado, Galp Energia
Luca Mancinelli, Trinity College Dublin
Mariusz Paszkowski, University of Silesia
Magdalena Piatkowska, ORLEN Upstream Ltd.
Agnieszka Pisarzowska, Institute of Geological Sciences, PAS
Maciej Rybicki, University of Silesia
Justyna Smolarek, University of Silesia
Jaroslaw Zacharski, ORLEN Upstream Ltd.
 Hydrocarbon potential – unconventional and
conventional, onshore and offshore, Algarve and Alentejo
basins.
1
ITINERARY
DAY 1
DAY 2
Lisboa - Grândola (2 hours drive, mostly highway)
Breakfast at 8.00, Check-out at 8.30h
Hotel – Carrapateira (20 min drive)
STOP 1 – Serra de Grândola
Introduction - regional geology. Mértola Formation
STOP 2 - Cabo Sardão
Black-shales of the Mira formation
STOP 3 - Monte Clérigo
Black-shales of the Brejeira formation
LUNCH - Monte Clérigo beach
STOP 4 - Arrifana beach
Black-shales of the Brejeira formation
STOP 5 – Bordeira
Black-shales of the Brejeira Formation
STOP 6 – Castelejo
Black-shales of the Brejeira formation
Dinner & Overnight - Hotel Memo Baleeira (Sagres)
STOP 7- Carrapateira
Mesozoic cover of the Carboniferous basement
STOP 8 - Telheiro
Paleozoic – Mesozoic unconformity
LUNCH - Bag-lunch close to Sagres
STOP 9 – Sagres
Jurassic dolomites
STOP 10 – Lagos
Tertiary karstified cover
Lagos-Lisboa (3 hours drive, highway)
TIDES
LOW
HIGH
20th May – 10.40 (0.64) and 17.00 (3.50)
21st May – 11.10 (0.79) and 17.35 (3.35)
2
STRUCTURE OF THE FIELD-TRIP OBSERVATIONS
STOP 1
Grândola
- Sines
STOP 2
Cabo
Sardão
Coastal
Abrasion &
Sedim.Cover
(70m)
Coastal
Abrasion
Platform
(40m)
Mesozoic
Uplift and
erosion
Uplift and
erosion
Uplift and
erosion
Uplift and
erosion
Late
Carbonifer.
Gentle
folding
Tabular
& gentle
folding
Intense
Folding
Carbonifer.
Shales &
sedimentation
Moscovian
Greywackes
BlackShales
Mira
Fm
BlackShales
Brejeira
Fm
Tertiary
deformation
Serpukhovian
Mértola
Fm
STOP 3
Monte
Clérigo
--
STOP 4
Arrifana
STOP 6
Castelejo
STOP 7
Carrapateira
STOP 8
Telheiro
STOP 10
Lagos
Coastal
Abrasion
Platform
(80m)
Coastal
Abrasion
Platform
(20m)
Coastal
Abrasion
Platform
(80m)
Emersion
 Karstif.
 Infill
Uplift and
erosion
Uplift and
erosion
Uplift and
erosion
Trias-Jura
subsidence
Uplift
and
erosion
Tabular
& gentle
folding
Folding
and
Thrusting
Tabular
+ Intense
folding
Metamorf.
basement
Metamorf.
basement
--
BlackShales
Brejeira
Fm
BlackShales
Brejeira
Fm
BlackShales
Brejeira
Fm
Basement
Basement
--
Coastal
Abrasion
Platform
(100m)
STOP 5
Bordeira
--
3
FRANCE
PORTUGAL
LISBOA
SINES
SPAIN
CABO SARDÃO
MOROCCO
This field-trip will take
us from Lisbon to the
southern coast of
Portugal, mostly along
the Atlantic coast.
All the stops will be on
the seaside and inside
SW Coast National
Park (PNSACV), which
extends from Sines to
Sagres.
LAGOS
Monte CLÉRIGO
ARRIFANA
CARRAPATEIRA
CASTELEJO
SAGRES
Most of this atlantic coast corresponds to
vertical cliffs cut on Carboniferous blackshales, with the exception of some
Mesozoic cover outcrops.
Our overnight will be in Sagres, a former
fishermen village, now a place for
summer holidays and nature week-ends.
4
WEIL ET AL., 2009
http://jgs.lyellcollection.org/content/167/1/127/F1.large.jpg
This field-trip will be focused on
Carboniferous units of the
Southern Portuguese Zone (SPZ)
in SW Iberia. These units are part
of the External Thrust Belt of the
Ibero-Armorican
Arc.
Its
geodynamic equivalents may be
found in SW Ireland SW England
and Rhenish Massif. In SW Iberia
the Gondwana terranes are
represented by the Ossa-Morena
Zone, which contacts with the SPZ
by the subduction-related BejaAcebuches ophiolithc complex
(BAOC).
5
CARBONIFEROUS BLACK-SHALES
- THE BAIXO ALENTEJO FLYSH GROUP
The Mértola, Mira and Brejeira Fms and
its structures may be identified by its
Total Radioactivity (ng/h) variations (Aerial
Gamma Ray Spectrometry, collected
RioTintoZinc (1991), courtesy of LNEG).
by
Tertiary
The Baixo Alentejo Flysh Group (BAFG) is composed of three different
Formations, considered to be diachronic. They represent a few kms of
accumulated turbiditic deposits whih are considered to be SWwards
increasingly: i) younger; ii) more distal and finner-grained; iii) thicker.
The proportion of greywackes and shales varies accordingly and
therefore it may be considered that the Brejeira Formation is the most
promising in terms of black-shales accumulated thicknesses, although
organic-rich facies are present all along this Flysh sequence.
The BAFG covers the Volcano-Sedimentary Complex and the organicrich Paraíso Formation, part of the Iberian Pyrite belt.
6
LATE
PALEOZOIC
REGIONAL
GEODYNAMIC
EVOLUTION OF
SOUTWESTERN
IBERIA
N
LATE CARBONIFEROUS – EARLY PERMIAN
COLLISION AND INTENSE DEFORMATION
Iberia
Mauritania
?
Fonseca et al., 2015,
(unpublished)
Brejeira Fm
? ?
LATE CARBONIFEROUS
Mira Fm
Mértola Fm
?
VS
Early Carboniferous
VS – VolcanoSedimentary
Complex
PQ
S
Late Devonian
PQ – PhyllitoQuartzitic
Group
7
SW
Carrapateira
Aljezur
Brejeira
Mira
SW
NE
Aljustrel
Odemira
Mértola
PL
VS+PQ
PL – Pulo do Lobo Formation; VS – Volcano-Sedimentary Group; PQ – Phyllito-Quartzitic Group; SW – Southwest Group
24.7 % SHORTENING due to folding
DEFORMATION
AND
SHORTENING
in the SOUTHERN
PORTUGUESE
ZONE
(in BOLACHA, 2014)
18% SHORTENING due to thrusting
27 km
36.3 % SHORTENING due to folding
97 km
70 km
8
STRUCTURAL LEVELS AND DEFORMATION
The concept of structural level (as defined by Mattauer 1973) is based on the observation that the style of deformation
changes with depth due to a large number of constraints such as: changes in temperature, confining pressure (overburden),
geometry and vicinity of major accidents (thrusts), etc.
In a thin-skin deformation model as SPZ, with extreme plastic units (black-shales), the presence of very closed to major
thrusts changes dramatically the style of the structural levels. Near the thrusts, structures become more pervasive and subvertical, with a large number of advanced faults and fractures.
At SPZ this scenario generally occurs on top of isopach to slightly stretched (A style) folds. At the base of the section, far away
from the main thrusts, the bedding and early fabrics are always recognizable, locally with gentle folds or locally overturned
folds, with an axial planar schistosity present.
9
39%
36%
52%
DEFORMATION and SHORTENING
Compression and folding modeling indicates
regional shortening values around 35%. Major
Thrusts may be responsible for up to 18%
shortening.
Geometric reconstruction of foldings at
outcrop scale (photos) shows shortenings up
to 52 %.
10
CARBONIFEROUS BLACK-SHALES AND SHALE-GAS POTENTIAL
The potential of the Southern Portuguese Zone Carboniferous units for shale-gas is, at the moment, a line of scientific
research supporting a future exploration pathway.
There are clear lithological and faciological indicators of good source-rocks, allthough the present-day outcropping TOC
values are naturally low. Organic matter maturation attained gas-window and there are also clear indicators of
hydrocarbon generation, with pirobetumen in many samples.
Deeply buried gas accumulations have been identified in some mining exploration wells, aiming at the Iberian Pirite Belt
massive sulphides of the Sub-Culm.
Permian deformation may have disrupted the continuity and integrity of these accumulations, but it may also have
preserved some tectonic blocks from deeper overburdens, bringing them upwards along large-scale thrusts.
Carboniferous accumulation of a few
thousand meters of turbidites with some
organic-rich layers has been followed by
intense subsidence and overburden at the
end of the Carboniferous. Most probably
there has been abundant generation of
hydrocarbons. Terranes collision promoted
intense deformation, with folding and
thrusting to the SW, throughout the early
permian.
Permo-Triassic
times
have
witnessed mostly uplift and coeval erosion
of up to 5 km (?). Since the Late Triassic,
Pangea’s break-up and Atlantic opening,
promoted extension, subsidence and
development of Mesozoic basins on the
western and southern borders of the Iberian
Massif (Alentejo and Algarve basins).
UNCONVENTIONAL
HYDROCARBON
SYSTEM CHART
SEDIMENTATION
OM ACCUMULATION
COMPRESSION &
FOLDING
THRUSTS
HC GENERATION
UPLIFT &
EROSION
POST-OROGENIC
OVERBURDEN
11
Black – McCormack et al, 2007
Yellow – Fernandes et al., 2012
Green – Partex/Repsol, 2013
Red – Partex/Repsol, 2013
TOC data are scarce and do not seem to be very
promising. However, is must be noticed that these are
present-day outcrop values. This means that we are
dealing with residual values - generation attained the
Gas-window and most of the original Organic Matter
has allready been lost.
Over-maturation, related to greenshist metamorphic facies
has been the main obstacle to consider these units as
having some shale-gas potential. However, Vitrinite Ro%
data show some interesting heterogeneities and values
below 3.0 (dark blue) or 3.5 (light blue), partucularly in the
SW sectors between Arrifana and Castelejo.
12
SW IBERIA
Southern Portuguese Zone
2
Cabo Sardão
ALENTEJO
Mesozoic
Basin
MIRA Fm
(offshore)
3
Monchique intrusion
4
1
2
6
7
10
5
6
6
5
4
3
ALGARVE
Mesozoic
Basin
Lagos
8
9
BREJEIRA Fm
10
Sagres
BREJEIRA Fm
2 MIRA Fm
Pre-CULM
Oliveira et al., 1984
Geological Map 1:200.000
13
Mte CLÉRIGO
3
CARRAPATEIRA
4
ARRIFANA
5
7
6
8
Manupella et al., 1992
Geological Map 1:100.000
9
14
STOP 1 – SERRA DE GRÂNDOLA
Introduction to Carboniferous shales
This stop shows the characteristics of the Mértola
Formation, with a predominance of Greywackes and
minor intercalations of black-shales.
Stratification shows large-scale folding with inverted short
limbs and vergence towards SW. Thrusts to the SW may
also be seen, indicating an overall compression with that
orientation.
Deformation style
B
WSW
Further down the highway, towards West, the contact
with the Mesozoic is exposed, showing Late Triassic
redbeds, clays and CAMP-related volcanics, followed by a
Jurassic carbonate sequence, part of the Alentejo basin.
These units are mostly covered by Plio-quaternary coastal
sands.
WSW
ENE
15
STOP 2 – CABO SARDÃO
Carboniferous black-shales
These high cliffs show the main sedimentary
characteristics of the Carboniferous sequence of the Mira
Formation, with alternating greywackes and shales.
These rhytmic deposits correspond to median to distal
turbiditic facies.
Deformation
style
B
Deformation is moderate, with mainly ondulated layers
and some decametric folds, with a southwards vergence.
The clif is around 40 m high and is topped by a PlioQuaternary marine abrasion surface with rounded
pebbles.
White stork nests on sea cliffs are characteristic of this
place a and unique feature worldwide.
16
STOP 3 – MONTE CLÉRIGO
Carboniferous black-shales
The cliffs at Monte Clérigo show a
predominance of intensively folded
black-shales.
ATENTION – Wet rocks covered by
green algae are extremelly slippery !
Deformation style
B
Towards the base (closer to the beach)
deformation is less intense, whereas
towards the top (southwards and
upwards) some incipient thrusting may
be identified.
This outcrop shows that slightly
different deformation styles may occur
allmost side-by-side. This may be due
to depth-dependent factors, but also
due to major thrusting accidents.
These large accidents have been
identified along this coast, putting in
contact units with strikingly different
deformation
and
maturation
intensities, as well as units with
biostratigraphic gaps as long as 15 My.
This fact has strong implications to
thermal maturation,
sampling,
analysis and interpretation, within an
exploration framework.
17
STOP 4 – ARRIFANA
Carboniferous black-shales
This bay exposes deposits from the
Brejeira Formation, with black-shales and
fine-grained greywackes.
Deformation is moderate, with large-scale
ondulated folds, characteristic of deeper
structural layers.
The cliff goes up to 100 m high, with a
distinct abrasion surface. At the far-end
horizon it is possible to see a lower
surface, corresponding to the Mesozoic
Carrapateira outlier (Stop 6).
Deformation
style
A
18
STOP 5 – BORDEIRA
Carboniferous black-shales
This small outcrop shows rich organic
facies with apparently not very high
maturation.
A big thrust is exposed on the left side,
indicating that this deformation occured
mostly in upper structural levels, related
with the Late Paleozoic up-lift.
Deformation style
C
19
STOP 6 – CASTELEJO
Carboniferous black-shales
This long outcrops extends from the Castelejo
beach northwards, untill the Cordoama beach.
The Northern half exposes highly deformed
black-shales and fine-grained greywackes, with
complex folds and inverted polarities.
An important sub-vertical thrust, brings to
contact the previously described layers and
much less deformed tabular layers, exposed at
the Castelejo beach. Thermal maturation
seems to be lower in this southern sector.
C
A
20
STOP 7 - CARRAPATEIRA
Mesozoic cover
N
7A - BORDEIRA BEACH
On this western mostly Paleozoic coast, a Mesozoic outlier may be seen at the
Carrapateira promontory. It corresponds to a downthrown block, with a clear tectonic
eastern limit, preserving most of the Mesozoic sequence. This infill may be correlated
with Alentejo offshore basin as welll as with the Algarve basin (only 20 km away).
Carboniferous basement
U. Triassic
redbeds
Basin’s
tectonic
border
Middle
Jurassic (?)
dolomites
ALENTEJO
Basin
21
STOP 7 - CARRAPATEIRA
Mesozoic cover
N
7A
Along the Carrapateira promontory a Late Triassic to Late
Jurassic sequence can be seen. This Mesozoic cover may
eventually act as a conventional reservoir for Paleozoic
sourced hydrocarbons, a play which has been successfully
tested in other Portuguese basins (Upphoff, 2005)
Late Triassic redbeds are covered by Hettangian red clays
and dolomites, followed by Early and Middle Jurassic
carbonates with intense dolomitisation, ending with Late
Jurassic marls.
Magmatic intrusions may be observed, mainly related to the
Late Jurassic doleritic Alentejo-dyke.
7A – Bordeira beach
7B – Três Angras bay
7C – Amado beach
7A
7B
1 km
UPPER JURASSIC
Volcanic tuffs and breccias
Marly limestones (*dolom)
Limestones and Dolomites
Middle JURASSIC Dolomites
Lw JURASSIC Marls & dolomites
HETTANGIAN Red clays & marls
UPPER TRIASSIC Redbeds
7B
Ribeiro et al., 1987
Geological Map 1:50.000
7C
7C
22
7B - TRÊS ANGRAS BAY
Upper Jurassic interbedded limestones and
marls at Três Angras.
Calciclastic marls and bioclastic limestones pass
into interbedded grey marls and limestones,
with some potential as source-rock. The
uppermost limestone beds are rich in
macrofossils including well preserved corals.
Vitrinite Reflectance studies point to an uplift of
about 2 km, part of it from the Late Cretaceous
to the Paleogene (Fernandes et al., 2013).
STOP 6
CARRAPATEIRA
N
Kimmeridgian marls with
Source-rock potential
STOP 7
CARRAPATEIRA
23
7C - AMADO BEACH
S
The cliifs North of this beach expose
the Upper Triasic red-beds, with
alluvial-fan coarse lags and eolian-like
fine-grained sands, covered by sabkha
deposits. This pair of sands/clays may
act as a Reservour/Seal for Paleozoic
gas, as proven in the Lusitanian Basin.
Looking Northwards this sequence is
interrupted by a magmatic intrusion
related to the CAMP event.
Looking southwards, Carboniferous
units appear again.
N
Upper Triassic
aeolian like redbeds
STOP 7
CARRAPATEIRA
N
N
Hettangian red
clays & dolomites
24
STOP 8 – TELHEIRO
Unconformity Carboniferous
shales vs.
Mesozoic cover
This major unconformity between Carboniferous shales and Triassic redbeds resulted from a
long geological evolution:
i) deposition of marine clays and sands in a distal turbiditic environment, c. 320 My ago;
ii) intense orogenic subsidence, heating and ductile deformation (5km depth?), c.320-300 My:
iii) post-orogenic uplift and erosion of 4.5 km (?), until exposure and weathering, c.300-230 My;
iv) deposition of fluvio-aeolian sands (c.230 My) unconformably covering folded Carboniferous.
Pliocene marine abrasion surface
Carboniferous folded
metasedimentary
basement
Hettangian red
clays and marls
U.Triassic
redbeds
N
25
STOP 8
TELHEIRO
Pliocene abrasion surface
S. Vicente
Cape
Sinemurian
dolomites
Quaternary
consolidated
aeolian dunes
Hettangian red
clays and marls
N
Carboniferous
metasedimentary
basement
Hettangian red
clays and marls
S
Hettangian red
clays and marls
Carboniferous
metasedimentary
basement
U. Triassic
redbeds
U. Triassic
redbeds
26
Sagres is the “Promontorium Sacrum”, considered by the
Romans as “the western end of the inhabited world”. This is
a place with a tremendous historical importance. It was at
least as important during the Age of Discovery as Cape
Canaveral was during the early years of space exploration.
STOP 9 – SAGRES
Jurassic dolomites
1 km
N
TELHEIRO
It was to this place that Prince Henry the Navigator, came in
the 15th century to work on his obsession to push back the
frontiers of the known world, and opened the phase in
Portuguese history called The Discoveries.
These high vertical cliffs
correspond to Lower
Jurassic dolomites, which
may act as conventional
reservoir (both primary
and
fractured)
for
Paleozoic gas.
St. Vincent CAPE
SAGRES
Rocha et al., 1979
27
STOP 10 – PONTA da PIEDADE
This touristic spot shows well developed karstic erosion in Miocene
limestones. After the Mesozoic infill of the Algarve Basin, intense
inversion resulted in uplift and erosion during the Late Cretaceous
and Paleocene in the present day onshore areas. Sedimentation
resumed in Middle Miocene with deposition of rhythmic fossiliferous
limestones and marls in coastal environments.
This coastal landscape is also a result of the the post-Miocene uplift of
the Western Algarve during the Plio-Quaternary. Karstic features are
partially filled up by Pliocene red sands, which after collapse of the
karstic vertical wall give place to the present-day holes and arches.
Offshore, coeval formations may act as conventional reservoirs,
sealed by Plio-Quaternary clays.
28
29
Barberes, G.A.; Pena dos Reis, R.; Pimentel, N.L.; Fonseca, P.E.; Azevedo, M. (2014) - Hydrocarbon
anomalies in the Carboniferous units of the South Portuguese Zone using the ThoriumNormalized method (Gamma radiation). GEOSHALE 2014
Barberes, G.A.; Pena dos Reis, R.; Pimentel, N.L.; Fonseca, P.E.; Azevedo, M. (2014) - Shale gas
potential in Carboniferous units of the South Portuguese Zone: a preliminary assessment .
GEOSHALE 2014
Bolacha, Edite (2014) – Modelos de Dinâmica da Terra aplicados à Geologia de Portugal:
Relevância da Experimentação Análoga no Ensino e na divulgação da Geologia. PhD, FCUL,
Lisbon University (in Portuguese, not published).
Dias, R. (2007). Evolução, Portugal de Antes da História. Estremoz: Associação Centro Ciência Viva
de Estremoz.
Dias, R. & Basile, C. (2013). Estrutura dos Sectores Externos da Zona Sul Portuguesa; implicações
geodinâmicas. In R. Dias, A. Araújo, P. Terrinha & J. Kullberg (Eds.), Geologia de Portugal.
Lisboa: Livraria Escolar Editora.
Fernandes, P.; Borges, M.; Matos, V.; Clayton, G. (2013) – Organic maturation of the Algarve Basin
(Southern Portugal) and its bearing on thermal history and hydrocarbon exploration. Marine
and Petroleum Geology, 46, 210-233.
Fonseca, P.E.; Azevedo, M.; Pimentel, N.L.; Pena dos Reis, R.; Barberes , G.A. (2014) - Tectonic
deformation: good or bad for shale gas exploration? The case of the SW Iberian Variscan
Chain . GEOSHALE 2014
Mattauer Maurice (1973) - Les deformations des materiaux de l'ecorce terrestre (Collection
Methodes) (French Edition).
McCormack, N.; Clayton, G.; Fernandes, P. (2007) - The thermal history of the Upper Palaeozoic
rocks of southern Portugal. Marine and Petroleum Geology, 24 (3), 145-150.
Oliveira, J. T. (1983). The Marine Carboniferous of South Portugal: a Stratigraphic and
Sedimentological Approach. In Lemos de Sousa, J. & Oliveira, J. T. (Eds.) The Carboniferous of
Portugal. Memórias dos Serviços Geológicos de Portugal, No 29, pp. 3-37.
Oliveira, J. T. (1990). Stratigraphy and Synsedimentary Tectonism. In Dallmeyer, R. D. & Matínez
García (Eds.). Pre-Mesozoic Geology of Iberia. (pp. 334-347). Berlin:Springer-Verlag.
Ribeiro, A. (1983). Structure of Carrapateira Nappe in the Bordeira Area, SW Portugal. In Lemos de
Sousa, J. & Oliveira, J. T. (Eds.) The Carboniferous of Portugal (pp. 91-97). Memórias dos
Serviços Geológicos de Portugal, nº 29.
Ribeiro, A. & Silva, J. B. (1983). Structure of the South Portuguese Zone. In Lemos de Sousa, J. &
Oliveira, J. T. (Eds.) The Carboniferous of Portugal (pp. 83-89). Memórias dos Serviços
Geológicos de Portugal, No. 29.
Ribeiro, A.; Munhá, J.; Dias, R.; Mateus, A.; Pereira, E.; Ribeiro, L.; Fonseca, P.; Araújo, A.; Oliveira,
T.; Romão, J.; Chaminé, H.; Coke, C. & Pedro, J. (2007). Geodynamic evolution of the SW
Europe Variscides. Tectonics, vol. 26, TC6009.
Silva, J. B.; Oliveira, J. T. & Ribeiro, A. (1990). Structural Outline. In Dallmeyer, R. D. & Matínez
García (Eds.). Pre-Mesozoic Geology of Iberia (pp. 348- 362). Berlin:Springer-Verlag.
Simancas, J. F.; Carbonell, R.; González Lodeiro, F.; Pérez Estaún, A.; Juhlin, C.; Ayarza, P.; Kashubin,
A.; Azor, A.; Martinez Poyatos,D.; Almodóvar, G. R.; Pascual, E.; Sáez, R. & Expósito, I. (2003).
Crustal structure of the transpressional Variscan orogen of SW Iberia: SW Iberia deep
seismica reflection profile (IBERSEIS). Tectonics, vol. 22, No. 6, 1062, pp. 1-19.
Main References