Final Year Dissertation

Richard Jones, C1232683

CARDIFF UNIVERSITY, CARDIFF, WALES, CF10 3AT, UK

GEOLOGY MAPPING PROJECT PYRÉNÉES-ORIENTALES

AREA D, LATOUR-DE-FRANCE 2015

RICHARD JONES, C1232683 1

Table of Contents

Abstract ...................................................................................................................................... 2

Chapter 1: Introduction ............................................................................................................. 3

Chapter 2: Stratigraphy .............................................................................................................. 6

2.1 Introduction.................................................................................................................. 6

2.2 Planèzes Pegmatite Formation .................................................................................... 7

2.3 La Touréze White Marble Formation ......................................................................... 10

2.4 L’ Arboussa Blue Bivalve Limestone Formation ......................................................... 12

2.5 La Peyrousse Muddy Limestone Formation ............................................................... 14

2.6 Bila Marble Formation ............................................................................................... 16

2.7 Latour-de-France Phyllite Formation ......................................................................... 19

2.8 Mas Chiffre-Rnes Sedimentary Gneiss Formation ..................................................... 22

2.9 St Martin Granitic Gneiss Formation .......................................................................... 24

Chapter 3: Structure ................................................................................................................ 27

Chapter 4: Geological History .................................................................................................. 30

Chapter 5: The age relationship of Area D within the Agly Massif, and the Variscan Orogeny,

based on the Intrusive Planèzes Pegmatite Formation on a regional scale. ....................................... 32

Chapter 6: Discussions/Conclusions ........................................................................................ 35

Appendices ............................................................................................................................... 36

Table of Figures ........................................................................................................................ 39

References ............................................................................................................................... 41


Abstract

This mapping project was undertaken as part of the Geology BSc Degree scheme at cardiff

university. During this project 6 weeks of field work was conducted to collect all the data needed to

produce an accurate geology map of Area D (Latour-de-France) whilst camping nearby. The data

was recorded both as a map and in field note books, to be used to create a digital copy back in the

UK.

The rock units discovered in this mapping area were;

The Planèzes Pegmatite Formation

The La Touréze White Marble Formation

The L’ Arboussa Blue Bivalve Limestone Formation

The La Peyrousse Muddy Limestone Formation

The Bila Marble Formation

The Latour-de-France Phyllite Formation

The Mas Chiffre-Rnes Sedimentary Gneiss Formation

The St Martin Granitic Gneiss Formation

Along with these rock lithologies, structural data was recorded to interperate the events

that happened in the past to produce the current subsurface geology and topography of the area.

These findings revealed the events included both the Variscan Orogeny and the Alpine

Orogeny, causing metamorphism and deformation throughout the area. And have also led to a

greater understanding of the techniqes used to understand the geological context of an area.


Chapter 1: Introduction

The aim of this project is to create a map of the bedrock geology, around the small town of

Latour-de-France. This forms the 30 credit module (EA3104 - Geological Mapping Project) and

consists of 6 weeks in the field along with 3 months of follow-up work on return to the UK.

Work conducted independently consists of this write up, as well as many other techniques

such as using Corel Draw to create a digital cross section and using ArcMap to create a digital fair

copy of the map. To comply with health and safety guidelines, the fieldwork element of this project

was completed alongside Katie Ellen Phillips and Sarah Louise Richards and supervised by Dr Lesley

Cherns of Cardiff University.

Whilst on location, the main objective is creating an accurate bedrock geology map based

on observations made when mapping outcrops between 29th June 2015 and 12th August 2015. The

working day starts at sunrise (6:30am CET) leaving the campsite on foot to cover all accessible

routes within the mapping area, this will continue until it is not viable, due to the Mediterranean

summer temperatures, at the height of day (2:30pm CET). If required mapping will also

recommence in the evening, when temperatures drop (7:30PM CET).

During field work the aim is to produce field slips containing all data collected at outcrops,

these are based on a 1:10,000 map of the area produced on ArcMap and printed on A4 card for

ease of use in the field

While mapping the outcrops, samples are be collected for use as a fresh surface in the field

and for further analysis on return to Cardiff. All data from each outcrop, is recorded in a field

notebook as a reference to coincide with the field slips produced, data will include GPS locations

(from a Garmin eTrex 10), descriptions of minerals within the rock, using a hand lens, to distinguish

the different rock units, sketches where applicable, and finally structural data, using a compass

clinometer.

This project is situated in southern France, within the Pyrénées-Orientales department. The

small commune Latour-de-France, as seen in figure 25, 21km North West of Perpignan, is where

this project is mapped, as seen in figure 1.


FIGURE 1 MAPPING AREA LOCATION MARKED ON A MAP OF FRANCE.

The coordinates (using WGS 1984 UTM Zone 31N) for the corners of the mapping area, as

seen in figure 2, are;

North West: X 469000 Y 4737000 North East: X 472350 Y 4737000

South West: X 469000 Y 4733000 South East: X 472350 Y 4733000

The total area that was covered by this mapping project equates to 17 square kilometres

with a relief range from 86 metres above sea level at the ford on the north side of Latour-de-France

to 424 metres above sea level at the highest point along the northern ridge. The area is made up of

a large ridge in the north with an eroded flood plain valley in the middle and another ridge in the

south.

Access within the area was easy due to the roads created by the land owners to access their

vineyards, only the top 2 square kilometres in the east were inaccessible due to harsh vegetation

and near vertical cliffs. As previously mentioned, the area consisted of vineyards where ever the

topography was suitable, for this reason, exposures were distributed along road cuttings and

surrounding the L’Agly river.


The area mapped belongs to the North Eastern Pyrénées, within the Variscan fold belt of the

Agly Massif.

FIGURE 2 EXTENT OF THE MAPPING AREA MARKED ON A LOCAL MAP.


Chapter 2: Stratigraphy

2.1 Introduction

This chapter will describe each formation in detail out the origin of each name, where each

type-locality is found, a lithological description, the distribution of each formation with use of data

in figure 3, where each formation makes contact with other formations, the age of each formation,

and finally the depositional environment that led the creation of each formation.

FIGURE 3 LITHOSTRATIGRAPHICAL COLUMN OF LITHOLOGIES IN AREA D.


2.2 Planèzes Pegmatite Formation

This formation is named after the village of Planèzes which appears on the western most

boundary of the mapping area, it is named this for 2 reasons;

The only exposed outcrop of this formation is found at the type locality, number 44, 400

metres north east of the village.

50 metres outside of the western boundary of the area, this formation is seen

protruding out of the side of a house in the village suggesting that this formation is also

found beneath Planèzes.

The type locality for this formation is number 44 at X: 469062, Y: 4735145, this exposure is

found protruding out of the ground, as seen in figure 4, 400 m north east of the village of Planèzes,

near the western edge of the mapping area.

FIGURE 4 PHOTOGRAPH OF PLANÈZES PEGMATITE FORMATION AT LOCALITY 44, DR CHERNS FOR SCALE.

This formation is an intrusive igneous rock consisting of 60% Quartz, 20% Plagioclase

Feldspar and 20% Muscovite Mica. On a fresh surface it appears mainly white due to large (up to

6cm) plagioclase crystals that displayed carlsbad twinning with grey glassy Quartz crystals along

with large (up to 15 mm) grey sheeted Mica crystals, as seen in figure 5. On a weathered surface


however this rock lacks the sheeted mica crystals as they are easily weathered away, this leaves the

weathered surface look blockier as only the Plagioclase and Quartz Crystals remain.

FIGURE 5 PHOTOGRAPH OF THE LARGE MUSCOVITE MICA CRYSTALS WITHIN THE PLANÈZES PEGMATITE FORMATION AT

LOCALITY 167, 72MM LENS CAP FOR SCALE.

This formation forms part of a linear system of intrusions that are believed to be the

foundations of most villages in the area. This formation appears at both locality 44 and beneath the

village of Latour-de-France giving it the raised relief over the surrounding landscape. There are also

observed outcrops outside of the mapping area to the south that also intrude in a linear fashion.

This formation has 1 observed contact, the locality number where this contact was observed

is 44. This contact displays melting of the Latour-de-France Phyllite Formation to form Hornfels, this

is due to the Pegmatite intruding the Phyllite at a much higher temperature and creating a baked

margin on the edge of the Phyllite and a cooling margin on the edge of the Pegmatite during the

process of contact metamorphism.

This formation is of Cretaceous age and dates back to 117.5 million years ago (Windley

1981; Boulvais et al. 2007). This is the youngest formation in the stratigraphy of this mapping area.


This formation was created during the last stages of the Variscan Orogeny, during this time,

any magma chambers that had formed beneath the surface at the start of the Variscan had

crystalized out by fractionation leaving the an unfertile melt, this lead to the remaining crystalizing

out as a Pegmatite (Course Crystalline Igneous Rock)

FIGURE 6 PHOTOGRAPH OF A METAMORPHOSED CONTACT BETWEEN THE PLANÈZES PEGMATITE FORMATION

AND THE LATOUR-DE-FRANCE PHYLLITE FORMATION, LOCALITY 44, KATIE PHILLIPS AND SARAH RICHARDS FOR SCALE.


2.3 La Touréze White Marble Formation

This formation is named after La Touréze which appears on the map in the middle of the

northern ridge of the mapping area, the ridge almost entirely consists of this lithology. The reason

for being named a white marble is due to its radiant white colour when sunlight reflects off a fresh

surface.

FIGURE 7 PHOTOGRAPH OF THE HIGH RELIEF RIDGE (358 METRES AT THIS POINT) COMPRISING OF THE LA

TOURÉZE WHITE MARBLE FORMATION TAKEN AT LOCALITY 156 (PHILLIPS 2015).

The type locality for this formation is number 137 located at coordinates X: 472322 and Y:

4737271, this exposure is seen as a Road cutting, and is found along the Utilities access road, in the

north eastern quarter the map, near the eastern boundary of the mapping area.


This formation is a massive marble, on a fresh surface it appears white with a very coarse

(1.5 mm), saccharoidal, and crystalline texture comprising entirely of Calcium Carbonate. On a

weathered surface however this rock appears dark blue, very similar to that of the fresh surface of

the L’ Arboussa Blue Bivalve Limestone Formation.

This formation forms for the northern ridge (raised topography) both within the mapping

area and north of the mapping area, as seen in figure 26, it is 98.5 metres thick (on the line of cross

section) and appears from the northern extent of the mapping and ends at a southerly extent of Y:

473590 depending on the contours of valleys in the ridge. This formation also appears at the

eastern boundary of the mapping area and continues across to the western boundary of the area.

The observed contact of this formation is at the southerly extent of the unit where is

alongside the L’ Arboussa Blue Bivalve Limestone Formation, the locality number for where this

sharp contact was observed is 126 at coordinates X: 472323 and Y: 4737754. There is no observed

contact at the northern extent of this formation, although, is does have a contact with the L’

Arboussa Blue Bivalve Limestone Formation in the north as there is a synclinal fold running east-

west through this formation.

This formation is of Mid-Cretaceous age, formed due to extension at the end of the Variscan

Orogeny (Bouhallier et al. 1991; Olivier et al. 2004; Boulvais et al. 2007) , and is the second

youngest formation in the stratigraphy of this mapping area.

This formation would have been deposited in a warm shallow marine environment, above

the CCD (Carbonate compensation depth) allowing the calcium carbonate particles to settle on the

sea floor as a calcareous ooze. This ooze then went through digenetic processes to form a

limestone, over time this limestone was then buried beneath overlying sediment until it was at an

optimal depth with the correct temperature and pressure to metamorphose into the marble seen

today.


2.4 L’ Arboussa Blue Bivalve Limestone Formation

This formation is named after L’ Arboussa which appears on the map, 250 metres north of

the mapping area, it is named this because the type locality for this formation is located in the same

place as this name appears on the map. It is named a blue bivalve limestone because there are

carbonate bivalve fossils (figure 8) found throughout this formation and blue due to the colour it

presents on both a weathered and a fresh surface.

The type locality for this formation is number 156

located at coordinates X: 469671 and Y: 4738213, this

exposure is found at the base of the northern extent of the La

Touréze White Marble Formation ridge. This locality is found

250 metres north of the mapping area central northern extent.

This formation is a massive Marble, 90% calcium

carbonate nd 10% clay minerals, on both a fresh surface and

the outer weathered surface this formation is dark blue as

seen in figure 9, with a medium (0.5 mm), saccharoidal,

crystalline texture. There are carbonate bivalve fossils, sparsely

distributed throughout this formation.

This formation forms part at both the northern and

southern extent of the northern ridge within the mapping

area, it is 11.5 metres thick and appears at the northern extent of the mapping area and as well as

between Y: 4736350 and Y: 473575 depending on the contours of valleys in the ridge. This

formation also appears at the eastern boundary of the mapping area and continues across to the

western boundary of the area with patches of it found in the north east and north west corners of

the mapping area.

This formation has 2 observed contacts both northerly and southerly contacts, the locality

numbers for where these contacts were observed are 126 in the north and 187 in the south.

Locality 126 is the contact mentioned above in 2.2.5 where this formation is alongside the La

Touréze White Marble Formation. The sharp contact observed at locality 187 is found at

coordinates X: 470228 and Y: 4736457, where this formation is seen alongside the La Peyrousse

Muddy Limestone Formation.

FIGURE 8 PHOTOGRAPH OF A BIVALVE

FOSSIL FROM THE L’ ARBOUSSA BLUE

BIVALVE LIMESTONE FORMATION, 2.5

CM SD CARD FOR SCALE.



Orogeny (Bouhallier et al. 1991; Olivier et al. 2004; Boulvais et al. 2007), and is the third youngest

formation in the stratigraphy of this mapping area.

This formation would have been deposited and metamorphosed in a similar environment as

the La Touréze White Marble Formation in a warm shallow marine environment rich in bivalves and

organic material to form the fossils and the dark blue colour seen today.

FIGURE 9 PHOTOGRAPH SHOWING THE BLUE COLOURING OF A WEATHERED SURFACE OF THE L’ ARBOUSSA BLUE

BIVALVE LIMESTONE FORMATION AT LOCALITY 151, LG NEXUS 5 FOR SCALE.


2.5 La Peyrousse Muddy Limestone Formation

This formation is named after La Peyrousse which appears on the map at the 213 metres

above sea level marker, 600 metres north of Latour-de-France. It is named this because it is near to

the locality where this formation was first observed in the field. It is named a muddy limestone

because it consists of a mud like sediment, softer than the other carbonate formations in this area,

yet still reacts with HCL proving it contains CaCO3.


found near the base of the southern extent of the La Touréze White Marble Formation ridge, below

Rock Neger. This locality is found 300 metres west of the electricity cables in the centre of the

mapping area.

This formation is a low grade metamorphosed limestone with more resistant features

distributed within (70% calcium carbonate and 30% clay minerals). On a fresh surface it appears

brown with a fine grain (0.2 mm) sediment that has been through low grade metamorphism to

form some crystalline grains, the outer surface shows signs of iron weathering as there is a mild

orange colouration.

This formation forms part at both the northern and southern extent of the northern ridge

within the mapping area, it is 7.5 metres thick and appears in the north eastern extent of the

mapping area and as well as between Y: 4736300 and Y: 4735700 depending on the contours of

valleys in the ridge. This formation appears at the eastern boundary of the mapping area and

continues across to the western boundary of the area.


numbers for where these contacts were observed are 80 in the north and 79 in the south. Locality

80 is a sharp contact where this formation is alongside the L’ Arboussa Blue Bivalve Limestone

Formation and is found at coordinates X: 471994 and Y: 4735832. The sharp contact observed at

locality 79 is found at coordinates X: 472050 and Y: 473, where this formation is seen alongside the

Bila Marble Formation.


Orogeny (Bouhallier et al. 1991; Olivier et al. 2004; Boulvais et al. 2007), and is the fourth youngest




the La Touréze White Marble Formation in a warm shallow marine environment, there would also

have been an additional sediment input which was releasing siliciclastic material in the system

resulting in the brown mud like texture of this formation.

FIGURE 10 PHOTOGRAPH OF AN EXPOSURE DISPLAYING A MORE RESISTANT FEATURE OF THE LA PEYROUSSE MUDDY

LIMESTONE FORMATION AT LOCALITY 150, 72MM LENS CAP FOR SCALE.


2.6 Bila Marble Formation

This formation is named after Bila which appears on the eastern boundary of the mapping

area, 200 metres north east of the type locality for this formation.


found at the base of the southern extent of the La Touréze White Marble Formation ridge, as seen

in figure 11. This locality is found 50 metres north of the river crossing, at the north of the village of

Latour-de-France, the exposure is found on the north side of the D9 road from Estagel.

FIGURE 11 PHOTOGRAPH OF CALCITE VEINING WITHIN THE BILA MARBLE FORMATION AT LOCALITY 18, AUTHORS HAND

FOR SCALE (PHILLIPS 2015).

This formation is a massive marble, 100% calcium carbonate, on a fresh surface it appears

grey with a very coarse (1.5 mm), saccharoidal, crystalline texture. On a weathered surface


however this rock is pink, as is appears to be dolomitised due to the visible surface being a fault

plane. The fault plane consists of a brecciated section of cliff that extends for 30 metres from

locality 18 to locality 19 (Figure 12).

FIGURE 12 PHOTOGRAPH OF AN EXPOSED SURFACE OF FAULT BRECCIA WITHIN THE BILA MARBLE FORMATION AT

LOCALITY 19, GARMIN ETREX 10 FOR SCALE (PHILLIPS 2015).

This formation forms part of the southern extent of the northern ridge within the mapping

area, it is 31 metres thick and appears in the northern half of the mapping area and as well as

between Y: 4736200 and Y: 4735400 depending on the contours of valleys in the ridge. This

formation appears at the eastern boundary of the mapping area and continues across to the

western boundary of the area. There is also an outcrop that has been cut off by the western

boundary of the mapping area, from field observations this appears to link up with the rest of the

formation in a small valley just over the western extent of the mapping area.


numbers for where these contacts were observed are 79 in the north and 18 in the south. Locality

79 is the contact mentioned above in 2.4.5 where this formation is alongside the La Peyrousse

Muddy Limestone Formation. The contact observed at locality 18 is found at coordinates X: 472050


and Y: 473, where this formation ends as a fault plane and on the floor it is seen alongside the

Latour-de-France Phyllite Formation.

This formation is of Mid-Cretaceous, formed due to extension at the end of the Variscan

Orogeny (Bouhallier et al. 1991; Olivier et al. 2004; Boulvais et al. 2007), and is the third youngest



the La Touréze White Marble Formation in a warm shallow marine environment, although this

would have formed close to the CCD (Carbonate compensation depth) as it contains slightly less

CaCO3 than the White Marble resulting in a grey colouration of this formation.


2.7 Latour-de-France Phyllite Formation

This formation is named after the large village of Latour-de-France which appears 150

metres from the eastern boundary of the mapping area, this is also where the type locality is found.


found at the eastern side of the bridge over the Agly river, on the western side of Latour-de-France.

At this locality there is evidence for contact metamorphism in the form of Hornfels as well as

suitable surfaces to view the crystalline structure of the lithology, as seen in figure 13.

FIGURE 13 PHOTOGRAPH OF AN EXPOSURE OF THE LATOUR-DE-FRANCE PHYLLITE FORMATION DISPLAYING CONTACT

METAMORPHISM AT LOCALITY 107, ESTWING HAMMER (419 MM LONG) FOR SCALE.

This formation is a fine grained metamorphic Phyllite, the minerals present are, 60% Quartz

and 40% Biotite Mica. On a fresh surface it appears grey with an almost metallic lustre due to the

alignment of the minerals within the structure of the rock. On a weathered surface however this

rock appears brown and almost blocky, this is due to the accessory iron oxide minerals present

within the rock along with being broken down during physical weathering processes to form the

blocky surface. This lithology is easily eroded forming the areas of land with the lowest relief in this


mapping area. There is noticeable crenulation within the laminations of this lithology throughout

the mapping area, along with 35 cm wide quartz veining at locality 108, as seen in figure 14.

This formation forms the middle low relief belt of the mapping area that appears to form a

flood plain, it is approximately 81 metres thick and appears between Y: 4736180 and Y: 4733600

depending on the contours of valleys in the ridge at the north. This formation appears at the

eastern boundary of the mapping area and continues across to the western boundary of the area.

This formation has multiple observed contacts both at the northerly and southerly extents

of this formation. To the north there is a fault that connects this lithology to the Bila Marble

Formation, and to the south there is an unconformity between this lithology and the Mas Chiffre-

Rnes Sedimentary Gneiss Formation as seen on the cross section (figure 20).

This formation is of Cambro-Ordovician age (Zwart and De Sitter 1979), and is the fifth

youngest formation in the stratigraphy of this mapping area.

This formation would have been deposited in a deep marine environment, this would have

been a low energy environment allowing for siliceous sediment, this was then metamorphosed due

to constant burial, subjecting the sediment to high pressure and high temperatures to create the

crystalline structure of Phyllite.


FIGURE 14 PHOTOGRAPH OF QUARTZ VEIN AT LOCALITY 108 WITHIN THE LATOUR-DE-FRANCE PHYLLITE

FORMATION, ESTWING HAMMER (419 MM LONG) FOR SCALE.


2.8 Mas Chiffre-Rnes Sedimentary Gneiss Formation

This formation is named after Mas Chiffre-Rnes which appears within the lithological unit on

the map, this appears 100 metres from the western boundary of the mapping area. It is named a

Sedimentary Gneiss as it is the first of two Gneiss formations in the area and this lithology contains

minerals of sedimentary origin.


found 200 metres south of the Latour-de-France cemetery, on the northern side of the D17

mountain road (figure 15). This locality best displays the crystal alignment within the rock,

therefore allowing for easy identification of each mineral visible through a hand lens.

FIGURE 15 PHOTOGRAPH OF THE MAS CHIFFRE-RNES SEDIMENTARY GNEISS FORMATION AT LOCALITY 26, KATIE

PHILLIPS' SIZE 6 FOOT FOR SCALE

This formation is a coarse crystalline metamorphic Gneiss, the minerals present are, 50%

Quartz, 20% Muscovite Mica, and 30% Plagioclase Feldspar. On a fresh surface it appears presents a

brown/grey colour with a glassy lustre due. On a weathered surface however this rock appears

brown and almost crumbly, this is due to the weathering of the feldspar crystals, breaking them

down into clay minerals and leaving the rock with the quartz and Mica crystals remaining.


This formation forms part of the southern high relief sections of the mapping area and

forms the cliff of the southern ridge, it is 28 metres thick and appears between Y: 4735750 and Y:

4733450. This formation appears as a small patch at the eastern boundary of the mapping area

along with appearing from at the western extent and continues eastward to X: 471400.

This formation has multiple observed contacts both at the northerly and southerly extents

of this formation. To the north there is an unconformity between this lithology and the Latour-de-

France Phyllite Formation, and to the south there are sharp contacts against St Martin Granitic

Gneiss Formation.

This formation is of Lower Cambrian age (535-570 million years ago) (Zwart and De Sitter

1979), and is the second oldest formation in the stratigraphy of this mapping area.

This formation would have been deposited in a deep marine environment, this would have

been a low energy environment allowing for siliceous, silt sized, sediment to build up, and this was

then metamorphosed due to constant burial, subjecting the sediment to high pressure and high

temperature, to the point of almost melting, over a long period of time. These processes are the

reason behind the gneissic banding and large felsic crystals that form the crystalline structure of the

Gneiss.


2.9 St Martin Granitic Gneiss Formation

This formation is named after St Martin which appears within the lithological unit on the

map, this appears 500 metres north east of the type locality of this unit. It is named an Igneous

Gneiss as it is the second of two Gneiss formations in the area and this lithology contains minerals

of igneous origin.


found 200 metres from the western extent of the mapping area and 600 metres from the southern

extent, at the edge of a vineyard overlooked by Chapel St Martin 75 metres to the south. This

locality best displays the crystalline texture with large 3cm plagioclase feldspar crystals present and

easily visible with the naked eye, also seen at locality 34 (figure 16).

FIGURE 16 PHOTOGRAPH OF AN EXPOSURE OF THE ST MARTIN GRANITIC GNEISS FORMATION AT LOCALITY 34,

COMPASS CLINOMETER FOR SCALE.

This formation is an intrusive igneous rock that has been subjected to high grade

metamorphism, consisting of 40% Quartz, 30% Plagioclase Feldspar, 30% Muscovite Mica, and in

some places, can consist of up to 15% Garnet. On a fresh surface it appears mainly white due to

large (up to 6cm) plagioclase crystals, as seen in figures 16 and 18, that displayed carlsbad twinning


with grey glassy Quartz crystals along with grey sheeted Mica crystals. On a weathered surface

however this rock lacks the sheeted mica crystals as they are easily weathered away, this leaves the

weathered surface look blockier as only the Plagioclase and Quartz Crystals remain.

FIGURE 17 PHOTOGRAPH OF A SAMPLE OF THE ST MARTIN GRANITIC GNEISS FORMATION DISPLAYING GNEISSIC

BANDING AND GARNET CRYSTALS, SAMPLE IS 10 CM LONG (PHILLIPS 2015).

This formation forms part of the southern high relief sections of the mapping, it is

approximately 154 metres thick and appears between Y: 4735500 and the southern extent of the

mapping area. This formation can be seen from the eastern extent across to the western extent of

the area.

This formation has multiple observed contacts to the north, both with the Mas Chiffre-Rnes

Sedimentary Gneiss Formation and the Latour-de-France Phyllite Formation.

This formation is of Lower Cambrian age (535-570 million years ago) (Zwart and De Sitter

1979), and is the second oldest formation in the stratigraphy of this mapping area.


This formation would have started as a plutonic granite, this would have been emplaced as

a large plutonic igneous body. It is apparent from the large plagioclase crystals within the unit that

it would have originally cooled over a period of time in the millions of years. This granite was then

metamorphosed due to constant burial, subjecting the crystalline structure of the rock to high

pressure and high temperature, to the point of almost melting, over a long period of time. These

processes are the reason behind the gneissic banding and large felsic crystals that form the

crystalline structure of the Gneiss, as seen in figure 17.

FIGURE 18 PHOTOGRAPH DISPLAYING THE LARGE PLAGIOCLASE FELDSPAR CRYSTALS AT AN ROAD CUTTING EXPOSURE OF

THE ST MARTIN GRANITIC GNEISS FORMATION , TAKEN AT THE BARAGE DE L’AGLY, 6.7 KM SOUTH WEST OF AREA D,

72MM LENS CAP FOR SCALE.


Chapter 3: Structure

This chapter will list and explain in detail, each structural element in the mapping area

based on the cross section (figure 20) and described using the book, The Mapping of Geological

Structures (McClay 1987). There are two synclinal folds in the area at both the north and the south

of the area, there is also a normal fault dividing the Mesozoic rocks in the north from the Palaeozoic

rocks in the south.

The central normal fault divides the Cretaceous carbonate rocks in the north from the Silica

rich basement rocks in the south. There is evidence of this from the brecciated marble that forms

the base of the Bila Marble Formation, within the mapping area. This fault plane has been

measured as dipping 62° to the north and striking at 292° (east-west), this trend is also seen on the

map (figure 23). As the rock units north of the fault are higher up in the stratigraphy compared to

the rock units in the south this would suggest that the fault plane measured is the hanging wall of a

normal fault. As this fault occurred after the Alpine folding of the carbonate rocks to the north, this

feature therefore have formed during the later stages of the Alpine Orogeny (Zwart and De Sitter

1979).

The northern synclinal fold is found within the high relief carbonate section on the map

(figure 23), this feature is of Alpine age (Olivier et al. 2004). The rock units that are included in this

feature are all Cretaceous in age due to being formed during the Variscan Orogeny, these were

then deformed during the Alpine Orogeny as part of a regional fold belt of the Pyrénées. As seen in

the cross section this is a close, this is due to an interlimb angle of 65°. This fold axial plane has an

overall orientation of east-west, although this fold is also deformed perpendicular to the limbs, this

is visible on the map.

The southern synclinal fold is found within the high relief gneiss section on the map (figure

23), this feature is of Variscan age and was deformed during tectonic activity that lead to the

formation of Pangea (Olivier et al. 2004). As seen in the cross section and the stereo net (Figure 19)

this is an inclined, plunging, close fold, this is due to an interlimb angle of 63° and the orientation of

the fold axis. This fold axial plane has an overall orientation of 64° north east to east-west, there is

also evidence of plunging seen on the stereo net, from this it is seen to plunge 11° towards 126°

south east.


FIGURE 19 STEREO PLOT OF S0 MEASUREMENTS FOR THE SOUTHERN SYNCLINAL FOLD IN AREA D.

No. of Data = 37

Mean Principal Orientation = 21/064 NW

Mean Resultant Direction = 12-061

Mean Resultant length = 0.63

Calculated Profile Plane: 79/306 NE

= Calculated Fold Axis: 11-126

N

E

S

W


FIG

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OSS

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Chapter 4: Geological History

This chapter will outline the sequence of events that have led to the current geology of the

mapping area, spanning from the oldest formation in the sequence to the current day.

The oldest formation in the area is the St Martin Granitic Gneiss, this would have been

emplaced below the surface as a large intermediate volcanic rock (Wickham and Taylor Jr 1987),

over time, the strata above would have been eroded away leaving this lithology exposed at the

surface. The second oldest formation is the Mas Chiffre-Rnes Sedimentary Gneiss, this was

originally deposited directly onto the intermediate volcanic rock, as a fine siliceous silt. Over time

these two rock units were buried beneath further sediment until they were at a depth where the

pressure and temperature were suitable for high grade metamorphism and in turn creating the

Igneous and Sedimentary granites found today. The third oldest formation in the Latour-de-France

Phyllite, this was also deposited as a fine siliceous silt, this however was deposited after the gneiss

formations had resurfaced and been eroded creating an unconformity, as seen in the cross section

(figure…). This strata was again buried but to a more shallow depth than before resulting in a lower

grade of metamorphism and forming the Phyllite. As the tectonic activity of the Variscan Orogeny

began, all three formations above, were deformed, due to compression, creating the syncline seen

in the south of the mapping area. This orogeny also led on the formation, during the cretaceous, of

the fourth oldest formation in the stratigraphy, the Bila Marble along with the other carbonate

formations seen in the north.

The Bila Marble would have been deposited during the as part of a carbonate ramp

sequence, this rock unit would have formed in the winnowed edge sands facies belt of the ramp, as

described by (Wilson 1975; Tucker and Wright 1990). Here the sediment being deposited would

have been calcarenitic oolite sands, this would have formed a well sorted grain stone that very poor

in organic life along with some dolomitised sections. The next formation in the sequence is the La

Peyrousse Muddy Limestone Formation, this would have formed in the deep shelf margin facies

belt. This is clear to see as the formation contains some shale like beds along with fine grained

calcareous siltstone and no fossil evidence, this this environment would have been below the storm

base to allow for the deposition of fine sediment. The L’ Arboussa Blue Bivalve Limestone


Formation continues the sequence down the ramp being deposited in the open sea shelf facies

belt. Evidence for this lies with its darker colour and the inclusion of whole bivalve fossils.

Directly above the L’ Arboussa Blue Bivalve Limestone, is the La Touréze White Marble

Formation, this is a crystalline, massive white marble, this does not conform to the ramp model, as

at this point there should be a very dark coloured formation. This lithology does however conform

to the winnowed edge sands facies belt as it is comprises entirely of calcium carbonate, it would be

possible if it had formed as an Oolitic grain stone with no other sediment input. A theory for this

could be a change in sea level at this location during deposition, this would have forced a retreat of

the carbonate ramp facies away from land. These sedimentary processes continued, the carbonate

rocks would have been buried to a shallow depth, causing low grade metamorphism to form the

marbles and more resistant elements of these formations.

As the Variscan orogeny came to an end, an igneous body upwelled below the Agly Massif,

over time the magma crystalized, fractionating out the early forming minerals. The final melt

continued to upwell and intruded in a linear fashion along both the Salvezines and the Agly massifs.

This intrusive rock is recorded in the mapping area as the youngest lithology, the Planèzes

Pegmatite Formation, it is clear that this formed from a late malt as there are large plagioclase

feldspar and muscovite mica crystals found within every exposure observed in the field.

The final event to affect the mapping area was the Alpine orogeny, this led to deformation

of the carbonate lithologies in the north to create the northern syncline and high relief areas.

During this period the lithosphere fractured and faulted, causing the middle dividing fault, this

normal fault formed when the northern lithosphere slipped down due to gravity and resting where

it is found today.


Chapter 5: The age relationship of Area D within the Agly Massif,

and the Variscan Orogeny, based on the Intrusive Planèzes

Pegmatite Formation on a regional scale.

During the mapping project, it became clear that there was a linear trend amongst the

intrusive bodies in and around the mapping area. These intrusive bodies were easily identified over

a distance of up to 2 km, as they have a distinctive shape and colour on the surface. It is believed

that the village, Latour-de-France is situated above a raised relief igneous intrusion, for strategical

purposes, this is very likely as at locality 14, there are signs of contact metamorphism from beneath

the village. 3 km west of Latour-de-France is the smaller village of Planèzes, where an igneous

intrusion can be seen protruding from the side of a house, this leads to the belief that during

colonisation in this area, early settlers noticed the strategic importance of the high relief and solid

foundations of the Pegmatite, and colonised each one they found. These higher relief areas are less

prominent the further east from the mapping area they area observed, being less common would

suggest that Area D displays the last remnants of hydrothermal veining from this time.

This linear distribution of intrusions is also seen to the south of the mapping area, one such

intrusion is seen at locality 167 (figure 22), whilst standing on top of this outcrop, there are 3

separate outcrops visible west of the locality, whereas there are no visible outcrops to the east.

These outcrops were also visible whilst driving west to the Barage de L’Agly, this reiterated that

there was a change in number of outcrops within Area D as they were common sighting to the west

and not obvious to the east.

Previously described by Philippe Boulvais Gilles Ruffet, Jean Cornichet, and Maxime Mermet

in the paper “Cretaceous albitization and dequartzification of Hercynian peraluminous granite in

the Salvezines Massif (French Pyrénées)”(Boulvais et al. 2007), this distribution of intrusive igneous

rocks is also a prominent feature of the Salvezines Massif (figure 21), 10 km west of the Agly Massif.

The outcrops appear to be equally distributed in a north east - south west orientation.

The paper describes the large igneous body beneath the Pyrenees, which formed during the

Variscan Orogeny, it then talks about how the granites crystalized out first leaving a mineral rich

fluid that intruded joints within the stratigraphy above to form the Pegmatite (Albitite). These

linear distributions conform to the orientation of compressional deformation in the region at this


time suggesting strong links between late Variscan fracturing and the infilling with hydrothermal

fluids. To prove this the authors used the 39Ar–40Ar dating method, which produced a result of

117.5 million years ago for the time of formation. This paper therefore suggests that the intrusions

within the mapping area are the eastern extent of crystallization at the end of the Variscan

Orogeny.

FIGURE 21 SIMPLIFIED GEOLOGICAL MAP OF THE SALVEZINES MASSIF, ALBITITES REFER TO THE PEGMATITE

INTRUSIONS, ADAPTED FROM (BOULVAIS ET AL. 2007)


FIGURE 22 PHOTOGRAPH OF AN EXPOSED OUTCROP OF THE PLANÈZES PEGMATITE FORMATION AT LOCALITY 167,

SARAH RICHARDS FOR SCALE.


Chapter 6: Discussions/Conclusions

Since starting this mapping project there have been many realisations about the area, at the

start there was the task of collecting the data with little context to the areas around or past events.

During the field work many trends and relationships were discovered within the geology of the

area, the linear distribution of the Pegmatites and the fault dividing the Mesozoic from the

Palaeozoic, to name two.

This has led to a greater understanding of the processes and hard work both in the field and

at the desk to create a geological map and interoperate data to realise the geological events of the

past and give an understanding of the relationship an area has with the rest of the continent at

each time in history.

Whilst mapping on the last day, a small adit became visible over the ridge, this was the first

and last time, any sign of extraction of economic rocks was observed. After speaking with locals

about the history of this region, it became evident that small scale Iron mining had been common

practice up until the 20th century, this explained the naming of Rock Neger in the middle of the

mapping area, that had been a matter of debate throughout the project.

Finally, Area D, has seen many events in its past, from the Cambrian basement rocks being

buried to depth, through to the Variscan and Alpine Orogenic events which have created the

landscape and subsurface geology present today.


Appendices

FIGURE 23 FINISHED GEOLOGICAL MAP OF AREA D, PRODUCED USING ARCMAP 10.2.2


FIGURE 24 LEGEND FOR THE GEOLOGICAL MAP (FIGURE 23)

LegendÜ

Lineation

á

Bedding

Approximate Contact

Contact Approximate

Contact Inferred

Contact Observed

Fault Observed

Inferred Contact

Line of Cross Section

Normal Fault

Normal Fault Inferred

Normal Fault Observed

Observed Contact

Observed Fault

M Syncline

MMMMMMMMMM Syncline Fold Hinge

Lithology

La Touréze White marble Formation

L’ Arboussa Blue Bivalve Limestone Formation

La Peyrousse Muddy Limestone Formation

Bila Marble Formation

Planèzes Pegmatite Formation

Latour-de-France Phyllite Formation

Mas Chiffre-Rnes Sedimentary Gneiss Formation

St Martin Granitic Gneiss Formation


Figure 25 photograph looking down on Latour-De-France to the south, taken at locality 80.

FIGURE 26 PHOTOGRAPH SHOWING THE LA TOURÉZE WHITE MARBLE FORMATION FORMING A HIGH RELIEF RIDGE, OF

728 METRES, 2 KM NORTH OF AREA D.


Table of Figures

Figure 1 mapping area location marked on a map of France. ................................................... 4

Figure 2 extent of the mapping area marked on a local map. .................................................. 5

Figure 3 Lithostratigraphical column of lithologies in area D. ................................................... 6

Figure 4 Photograph of Planèzes Pegmatite Formation at locality 44, Dr Cherns for scale...... 7

Figure 5 photograph of the large Muscovite Mica crystals within the Planèzes Pegmatite

Formation at locality 167, 72mm lens cap for scale. ............................................................................. 8

Figure 6 photograph of a metamorphosed contact between the Planèzes Pegmatite

Formation and the Latour-de-France Phyllite Formation, locality 44, Katie Phillips and Sarah

Richards for scale. .................................................................................................................................. 9

Figure 7 photograph of the high relief ridge (358 metres at this point) comprising of the La

Touréze White Marble Formation taken at locality 156 (Phillips 2015).............................................. 10

Figure 8 photograph of a bivalve fossil from the L’ Arboussa Blue Bivalve Limestone

Formation, 2.5 cm SD card for scale. ................................................................................................... 12

Figure 9 photograph showing the blue colouring of a weathered surface of the L’ Arboussa

Blue Bivalve Limestone Formation at locality 151, LG nexus 5 for scale............................................. 13

Figure 10 photograph of an exposure displaying a more resistant feature of the La Peyrousse

Muddy Limestone Formation at locality 150, 72mm lens cap for scale. ............................................. 15

Figure 11 photograph of calcite veining within the Bila Marble Formation at locality 18,

Authors hand for scale (Phillips 2015). ................................................................................................ 16

Figure 12 Photograph of an exposed surface of fault breccia within the Bila Marble

Formation at locality 19, Garmin eTrex 10 for scale (Phillips 2015). ................................................... 17

Figure 13 photograph of an exposure of the Latour-de-France Phyllite Formation displaying

contact metamorphism at locality 107, Estwing hammer (419 mm long) for scale. .......................... 19

Figure 14 photograph of quartz vein at locality 108 within the Latour-de-France Phyllite

Formation, Estwing hammer (419 mm long) for scale. ....................................................................... 21


Figure 15 photograph of the Mas Chiffre-Rnes Sedimentary Gneiss Formation at locality 26,

Katie Phillips' size 6 foot for scale ........................................................................................................ 22

Figure 16 photograph of an exposure of the St Martin Granitic Gneiss Formation at locality

34, compass clinometer for scale. ....................................................................................................... 24

Figure 17 photograph of a sample of the St Martin Granitic Gneiss Formation displaying

gneissic banding and garnet crystals, sample is 10 cm long (Phillips 2015). ....................................... 25

Figure 18 photograph displaying the large Plagioclase Feldspar crystals at an road cutting

exposure of the St Martin Granitic Gneiss Formation , taken at the Barage de L’Agly, 6.7 km south

west of area D, 72mm lens cap for scale. ............................................................................................ 26

Figure 19 Stereo plot of S0 measurements for the southern synclinal fold in Area D. ........... 28

Figure 20 cross section of area D from points A to B marked on the Map. ............................ 29

Figure 21 Simplified geological map of the Salvezines Massif, Albitites refer to the Pegmatite

Intrusions, adapted from (Boulvais et al. 2007) .................................................................................. 33

Figure 22 photograph of an exposed outcrop of the Planèzes Pegmatite FORMATION AT

locality 167, Sarah Richards for scale. ................................................................................................. 34

Figure 23 finished geological map of area D, produced using ArcMap 10.2.2 ........................ 36

Figure 24 legend for the geological map (Figure 23) ............................................................... 37

Figure 25 photograph looking down on Latour-De-France to the south, taken at locality 80.

.............................................................................................................................................................. 38

Figure 26 photograph showing the La Touréze White Marble Formation forming a high relief

ridge, of 728 metres, 2 km north of area D. ........................................................................................ 38


References

Bouhallier, H. et al. 1991. Evolution structurale de la croute profonde hercynienne; exemple du massif de

l’Agly (Pyrénées orientales, France). CR Acad. Sci. Paris Ser. II 312, pp. 647-654.

Boulvais, P. et al. 2007. Cretaceous albitization and dequartzification of Hercynian peraluminous granite in

the Salvezines Massif (French Pyrénées). Lithos 93(1), pp. 89-106.

McClay, K. R. 1987. The mapping of geological structures. Chichester: Wiley, pp. vi, 161 p.

Olivier, P. et al. 2004. Gneiss domes and granite emplacement in an obliquely convergent regime: new

interpretation of the Variscan Agly Massif (Eastern Pyrenees, France). Geological Society of America Special

Papers 380, pp. 229-242.

Phillips, K. 2015.

Tucker, M. E. and Wright, V. P. 1990. Diagenetic processes, products and environments. Carbonate

sedimentology, pp. 314-364.

Wickham, S. M. and Taylor Jr, H. P. 1987. Stable isotope constraints on the origin and depth of penetration of

hydrothermal fluids associated with Hercynian regional metamorphism and crustal anatexis in the Pyrenees.

Contributions to mineralogy and petrology 95(3), pp. 255-268.

Wilson, J. 1975. The Stratigraphy of Carbonate Deposits.Carbonate Facies in Geologic History. Springer New

York, pp. 20-55.

Windley, B. 1981. Phanerozoic granulites. Journal of the Geological Society 138(6), pp. 745-751.

Zwart, H. J. and De Sitter, L. 1979. The geology of the Central Pyrenees.

Final Year Dissertation

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