Unconformable contact between Hercynian Basement and Erillcastell Volcanics marked by abundant slate clasts in lower basltic andesitic lapilli tu� sheet
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Pont de Suert horst structure composed of a series of overturned wedges bounding a folded region of gypsiferous marl
Progressive overturning of Buntsandstein Formation to the south suggesting foreland rotation of oblique thrust sheets swinging during detachment on Triassic evaporites
Palaeohigh
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Alternation in dip direction and brecciation across road section suggest faulted contact
Large scale ductile deformation observed in evaporites - inferred association with ophitic intrusions
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El Pont de Suert
Syndepositional palaeotopographic half grabens. Greatest displacement in Upper Carbon�erous casuing signi�cant thinning of Erillcastell and Malpas Formations
Evidence for cross strati�ed meandering channel sands bounded by �ood plain silts
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Malachite veins and chert lenses - evidence for hydrothermal geyserite deposits
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o57
Legend
s
Overturned Bedding
¹
Pervasive S1 Cleavage
o
Right Way Bedding
³
Crenulation S2 Cleavage
á Slickensides
þ
³
S3 Kink Bands
P
S
Palaeocurrent
Rivers
Roads
Folds
), Synform
Boundaries
Inferred Geological Boundary
Observed Geological Boundary
Unconformity
Contours
Faults
* Inferred Backthrust
" Inferred Normal Fault
# Inferred Thrust Fault
Inferred Strike Slip fault
Observed Normal Fault
Observed Thrusted Contact
Thrust Bounded Unit
Lithologies
Hercynian Basement
Ophite
Peranera Formation
Pont de Suert Gypsum
Pont de Suert Limestone
Upper Bunter Formation
0 0.25 0.5 0.75 1Miles
SP
Structural Data
Infrastructure
Towns
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" "
Sedimentary
Erillcastell Volcanics
Metamorphic
IgneousP
S
P
S
66
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Section linesA A’
B B’
Main Cross Section
N-S Cross Section
49
Malpas Formation
Mesozoic Limestone
Lower Bunter Formation
Ventola
Gotarta
CLAY
SILT SA
ND
GRAN
ULE
PEBB
LE
COBB
LE
BOUL
DER
DEP
TH (m
)
LITH
OLO
GY
MAP
PIN
G LI
THO
LOGY
28
14
84
70
56
42
182
168
154
140
126
112
98
196
224
210
252
238
294
280
266
vf f m c vc
Schematic Sedimentary log1:1400 Scale
Based on unit thicknesses along Gotarta Road
Key
Shale
Silt
Sand
Matrix-supported conglomerate
Volcaniclastics
Volcanic breccia and tu�
Metamorphic basement
Reduction spots
Planar cross strati�cation
Trough cross strati�cation
Planar laminae
Coprolites
Skeletal fragments
Fossil fumaroles
Pillow structures
Preserved plant matter
Intermediate and silicic blocks and bombs
Accretionary lapilliVariable interbedded sequence of low grade greenschist facies phyllites, slates and marbles with marked di�erences in carbonate contents attributed to relict pelitic layers. Bioturbation and fossilised bioclasts are most strongly preserved in phyllites and calcareous slates. Overprinted pervasive, crenulated and kinked foliations as well as kiolmetre scale folds highlight a minimum of four deformation episodes corresponding to both Variscan and Alpine orogenesis.
Hercynian basement
Erillcastell VolcanicsComplex series of sub-lithological pyroclastic lapilli tu�s, mass �ow breccias and rhyolitic andbasaltic lava �ows underlain by a thick basaltic andesite lapilli tu� sheet marking the large scale unconformable contact with deformed basement metamorphics. Eroded normal graded ashfall deposits and sequences of poorly cemented strati�ed epiclastics exhibit strong lateral discontinuity. Evidence for fossilised and mineralised plant material and graphite bearing bedded tu�s highlight multiple eruption events and variable emplacement temperatures producing an upper welded ignimbrite succession comprised of basal silicic pillows, fossil fumaroles and �attened accretionary lapilli. The latter are commonly associated with malachite precipitation in areas of preserved cryptocrystalline quartz laminae representing hydrothermal �uid injection.
Stratigraphic Column1:1400 Scale
Malpas FormationA sequence of dark grey �ssile laminated silts and shales with evidence for preserved plant material interbedded with competent normal graded yellow to beige coarse silt to medium-grained sandstones exhibiting normal grading.
Peranera FormationConformable sequence of �ssile muds and silts exhibiting strong red colouration with variable concentrations of subrounded beige calcareous derbis �ow nodules subparallel to bedding. Evidence for vertebrae and abundant coprolites suggests the presence of tetrapods prevailing in a semi-arid environment. Interbedded sequences of andesitic tu�s concentrated towards the base of the succession.
Lower Bunter Formation
Upper Bunter Formation
Pont de Suert limestone
Pont de Suert Formation
This unit represents the incompetent Keuper marl series of the Triassic evaporite succession comprised of impure calcareous vividly-coloured beige, red and greenish-grey gypsiferous marl. Bedding is indistinct but may form contorted sub-horizontal isoclinal folds exhibiting boudinage. Interbedded dark grey to black gypsum laminae re�ect organic preservation with localised red crystalline manganese reduction zones. Marl dominated regions exhibit asymmetrical ripples up to 2 cm with evidence for fossilised tetrapods footprints and preserved raindops. The combination of brittle and ductile deformation forms an important detachment horizon along which thrusts have propagated.
Mesozoic Limestone
Calcareous nodules
Unconformity
CAR
BONI
FERO
USPE
RMIA
N
LOW
ERM
IDDL
E UP
PER
TRIA
SSIC
JURA
SSIC
Unconformable deposition marked by a poorly sorted clast supported basal conglomerate up to 2 m in thickness transitioning into weakly graded brown - maroon �ne to coarse-grained sands and minor interbedded sequences of micaceous mudstone and siltstones. Evidence for longitudinal and transverse bars and laterally discontinuous bank collapse pebble conglomerates are concentrated within regions of coarser sand fractions.
Overlying series of strongly red and maroon authigenic massive �ssile laminted silts and muds interbedded with sequences of �ne and medium-grained sands grading into a poorly exposed upper shale succession. Sedimentary structures are well developed dominated with preserved centimetre-scale asymmetrical ripples. Large scale trough cross strati�cation, groove casts and load structures are associated with meandering channel sands. Localised green reduction concretions are sparsely distributed throughout silt layers.
Dark to light grey silt grade calcareous imbricates forming projecting ridges bounded by the Pont de Suert Gypsum. Unit exhibits variable sparry and micritc natures with weakly developed cross strati�cation and laminae. Fossilsed material is sparse forming bioclastic shell fragments and burrowing trace fossils. Evidence for horizontal and poorly developed oblique styolites suggests subjection to both sedimentary loading and structural compression.
Massive light grey argillaceous calcareous unit exhibiting variable sparry and micritic natures conformably overlying the Triassic evaporites. Towards the base of the unit, dark grey medium to coarse grained dolomites dominate with a transition into interbedded sequences of sparryresistant beds and dark grey �ssile marls overlain by breccious intercalations. Semi-continuous calcite veins up to 2 cm in width occur throughout with sparse bioclasts present as fragmented bivalve shells concentrated in clusters.Observed Upper Bonansa and Prada sequences in the mapping area.
A A’
Backthrusted Mesozoic Limestone detaching on top of evaporites following reinversion of normal faults
Hercynian basement wedge marking the degree of overturning - isoclinal S1 faults are likely sub-horizontal following inversion Hercynian basement forming
core exposed due to erosion
Convergence of low angle �oor thrusts detaching on top of Triassic evaporites
SW NEForeland Hinterland
Inferred thrust shallowing towards Hinterland. Dominant basement forming eroded core of the Axial Zone Floor thrust propagating from
Axial Zone core along which thrust sheets have converged following detachment on Keuper marls
Cross Section along line of section A-A’1:10000 Scale
Regional Schematic Cross Section
IBERIA EUROPE
Sierra Marginales
FORELAND BASIN
AXIAL ZONE
Progressive deformation produced foreland rotation of thrust sheets - mapping area location
50 km
NS
Eroded Palaeozoic core
Backsteepening of ramp-�at series
Montsec BoixolsEBRO BASIN AQUATINE BASIN
Adapted form Saura & Teixell, 2006
NOGUERES ZONE
Geological Map of El Pont de SuertCharles Singer
Imperial College London
Ü
Thickening of Upper Carboniferous - Permian strata could be attributed to inversion of north verging sub-bedding parallel extensional faults
Pont de Suert Gypsum
UPPE
R
OphiteDark greenish grey to brown holocrystalline porphyritic tholeiitic dolerites characterised by an ophitic texture with tabular plagioclase enclosed within pyroxene phenocrysts.
Upper Palaeozoic strata exhibit signi�cant lateral thinning and restriction to localised extensional basins - Bunter represents more uniform deposition
LOW
ERLO
WER
1 km 1 km
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Elev
atio
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)
Foreland rotation of thrusts with progressive deformation to the SSW. Region marks boundary between axial zone and fold thrust belt with younging of faults towards the foreland
Faulted contact along weak evaporitic detachment horizon
Inverted bed dips shallow to the NE representing greater overturning towards the centre of imbricate stack
Detachment of Mesozoic Limestone capping foreland rotated thrusts producing duplex
Strongly deformed Herycnian Basement marking the transition of overturning. Unit comprised of discontinuous interbedded metasediments including slates marbles and phyllites. Evidence for multiple deformation episodes during Variscan orogeny and reactivation during Alpine.
Discontinuous imbricates of limestone in the Pont de Suert Formation forming thrusted wedges of a ramp �at structure representing a thrust bound duplex within a larger duplex structure
Weak, ductile Triassic evaporites provide detahcment horizon along which thrusts converge
Undulating contact provides evidence for unconformable deposition of Erillcastell volcanics in�ling palaeotopographic graben induced by basin ri�tng
3132454697190
3175004699471
Basic tholeiitic dolerite ophite intrusions in the Pont de Suert Formation - occur as intermittent outcrops through series of imbricates
Inclined non-overturned strata
A A’
Inferred repetition of Palaeozoiccover rocks
0
UPP
ER
PERM
IAN
Deposition of marine carbonates and pelite protoliths on the continental shelf of Laurussia subject to Hercynian orogeny.
TRIA
SSIC
Post-orogenic volcanism orginiating from crustal delamination and production of peraluminous calc-alkaline magmas.
Deposition of �uvial sediments within terrestrial half grabens associated with Pangaea ri�tng marked by basal angular unconformity with extensive erosion and relief rejuvination in Permian.
Underlying E-W trending half grabens likely controlled later fault orientations.
Syndepositional half grabens associated with thermal subsidence extending through Upper basement producing strong lateral discontinuity in sediments.
Interpreted Tectonostratigraphy
CARB
ON
IFER
OU
S
LOW
ERLO
WER
JURA
SSIC Extension associated with Atlantic and
Tethys rifting. Thermal uplift producing regression and Upper Jurassic unconformity (Vergés et al., 2002).
Alpine orogeny characterised by the foreland rotation of thrust sheets and inversion of pre-exisiting Cretaceous extensional faults.
CRET
ACEO
US
MID
DLE
UPP
ER Transgressional shallow marine limestones and sea-adjacent playa lakes.
Late Triassic tholeitiic dolerites associated with Pangaea rifting spreading laterally beneath poorly consolidated incompetent gypsiferous marls.
Second main phase of extension (Barremian to Albian) producing E-W trending extensional faults through substantial thinning of crust.
UPP
ER