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

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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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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

"

" "

Sedimentary

Erillcastell Volcanics

Metamorphic

IgneousP

S

P

S

66

#

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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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