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Geometric and Kinematic Reconstruction of the Chaleurs Bay Synclinorium (Gaspé Belt) through the Integration of Geological and Geophysical Data.

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M ic ta w G r. N Neecckkww iicckk M M RR MM Dubuc A Arrsseennaauulltt G Gaarriinn C CBB++MMCC P Paabbooss C Cll ee mm vvii ll ll ee N NOOMM A Annssee CCaassccoonn A

Annssee àà PPiieerrrree--LLooiisseellllee

L Laa VViieellllee Gascons W Weesstt PPooiinntt Indian Point ? W Whhiittee HHeeaadd B Boonnaavveennttuurree L Laa CCoouullééee ? W Weeiirr Viséan Tournaisian Lochkovian PragianEmsian Eifelian Givetian Frasnian Famenian Pridolian Ludlow Wenlock Ll an do ve ry Rhuddanian Aeronian Telychian Cambrian Tremadoc Arenig Darriwillian Caradoc Ashgill Neo-Proterozoic O rd ov ic ia n S ilu ria n D ev on ia n CCaa rrbb oonn iiffee rroo uuss Namurian M is si ss ip pi an SEISMICMARKER 10 9 1 11 6 7 4 3 2 5 8 s s Ta Ta Ar?/Ne Ac+We SEISMOSTRATIGRAPHY

Proterozoic basement: discontinuous, parallel to undulating, medium amplitude, and low frequency reflections. MaquereauGroup: parallel, locally continuous, high amplitude, and high frequency reflections .

Non metamorphosed Ordovician: chaotic, locally parallel, discontinuous, low amplitude, and high frequency

reflec-tions, characterized by erosive truncation.

ArsenaultFormation(?): regular, parallel, continuous, high amplitude, and high frequency reflections characterized

by onlap on older Cambro-Ordovician units.

NeckwickFormation: sigmoid, discontinuous, low amplitude and high frequency reflections, characterized by toplap

and downlap.

Du Milieu River Mélange: uneven, parallel to sub-parallel, not continuous to chaotic, low amplitude and high

frequen-cy reflections.

DubucFormation: sigmoid to parallel, non-continuous, high amplitude, and high frequency reflections .

GarinFormation: chaotic reflections.

Matapedia Group (Pabos + White Head formations) and Clemville Formation: diverging, discontinuous, very low

amplitude, and high frequency reflections, up to the local absence of reflections.

Lower Siliciclastic Assembly (Weir + Anse Cascon formations): parallel, locally continuous to chaotic reflections,

characterized by a very high amplitude and low frequency.

Intermediate Calcareous Assembly (Anse à Pierre-Loiselle + La Vieille formations): sigmoidal to parallel, continuous,

low amplitude and low frequency reflections.

UpperSiliciclastic Assembly (Gascons, West Point, and Indian Point formations): chaotic reflections.

PBasement? R ES ER VO IR SO U R C E R O C K M Maaqquueerreeaauu PPoorrtt--DDaanniieell RRiivveerr M Mééllaannggee ? Proterozoic basement 0 10 km Mq 4 3 2 1 Proterozoic basement 10 km 0 Maquereau rise erosion Mictaw Arseanult 0 10 km subsidence 2 3 1 Mictaw / Arsenault Maquereau C-O Proterozoic basement 0 10 km erosion Ma Ga Ar 0 10 km Mi

Honorat (Garin) + Matapédia

DA RA GRF GPF 0 10 km Ch SJSF 0 10 km Mi Mq Ga Ar 1 2 3 4 5 7 6

Lower Chaleurs + Upper Chaleurs

DA RA GRF GPF SJSF CBS APA CVGS SSE NNW

TA

C

O

N

IC

O

R

O

G

E

N

Y

T re m a d o ci a n -A re n ig ia n

Q

U

IE

SC

EN

C

E

D ar riw illi an -C ar ad oc ia n AC AD IA N SH O RT EN IN G M id dl e to La te De vo ni an A C A D IA N ST R IK E-SL IP M id dl e to La te D ev on ia n

EX

TE

N

SI

O

N

C ar ad oc ia n-R hu dd an ia n

Q

U

IE

SC

EN

C

E

R hu dd an ia n -P rid ol ia n

1.

2.

3.

4.

5.

6.

7.

8.

Density contrast (g cm-3) -0.100 -0.090 -0.080 -0.070 -0.060 -0.050 -0.040 -0.030 -0.020 -0.010 0.000 0.010 0.020 0.030 0.040 0.050 0.060 0.070 0.080 0.090 0.100 -0.058 Schu -0.035 Omi/Oar -0.024 Schl -0.010 OSma -0.006 C-O 0.004 Ogn 0.040 pC bsmnt 0.078 pCMq 2001-MRN-14A 2001-MRN-14B NNNNWW S SSSEE D uv al A nt ic lin e G ra nd P ab os Fa ul t Ob se rv ed C a l c u l a t e d S ai nt -J og ue s S ud Fa ul t G a ri n R iv e r F a u lt 80 90 100 110 Proterozoic basement p pCCMMqq OOaarr O Oggnn O OSSmmaa S Scchhll S Scchhuu C C--OO C C--OO O Oaarr O Oggnn p pCCMMqq O Ommii C C--OO 3 2 1 0 -1 -2 -3 ∆ g (m G al ) 0 2 4 6 8 10 De pt h (k m )

?

?

M MLLEEFF

In the model, the positive (southern)

anomaly is reproduced mainly through

tectonic stacking the high-density

greenschist facies Maquereau Group.

The negative anomaly is reproduced

mostly by the total absence of the

Maquereau Group and infilling by the

relatively low-density Upper Ordovician

Pabos Formation of the Matapedia Group.

The calculated residual gravity anomaly

curve, computed from the density

distri-bution derived from the geological

i n t erp ret at i o n , n i cel y m i m i cs t h e

observed anomaly curve. The gravity

modeling suggests: (1) the position of the

Proterozoic basement at a depth of about

10 km, (2) the presence of a tectonic

stacking of Cambrian-Ordovician units,

already suggested by the seismic

inter-pretation, and (3) the presence of a thick

succession of relatively low-density

syn-rift sedimentary rocks (Pabos Formation)

deposited during a post-Taconic

exten-sion episode.

Upper rollover and crestal collapse zone

Upper crestal collapse graben

Lower roll-over and crestal collapse zone

Syn-rift Pre-rift Unfolded ramp syncline reverse faults Ramp zone Lower crestal collapse graben A B

6. Analog Model

Figure 11. (a) Geometry and seismic velocity model of a

ramp-flat listric extensional fault system. Pre-extension

strata are shaded grey and syn-extension strata are unshaded.

(b) Migrated synthetic seismic section (with noise)

pro-duced by the Stable Beam Method (modified from McClay,

1995).

0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5 5,0 5,5 6,0

Mictaw Gr. Garin Fm. Matapedia Gr. Lower Chaleurs Gr. Upper Chaleurs Gr.

Pirate Cove/Escuminac Fms. Bonaventure Fm. e st im a te d vi tr in ite re fle ct a n ce (% ) Lithostratigraphic unit S SEE NNWW Immature Oil window Condensate Dry gas po st-Tacon ic buria l

M

LE

F

7. Correlations with existing

thermal maturity data

Figure 12. Variations in the average estimated vitrinite

equivalent-reflectance values in different lithostratigraphic

units of the Chaleurs Bay Synclinorium (Eastern area) and

the Aroostook-Percé Anticlinorium (modified from Roy,

2008).

0 1000 2000 3000 Shot 200 300 400 500 600 700 800 900 1000 1100 1200 1300 T W T (m s) 2001-MRN-14A 2001-MRN-14B S SEE NNWW 0 1000 2000 3000 Shot 200 300 400 500 600 700 SJSF SHCA LMASwp DA GRF GPF Sga_silt Sga_lime Slv Slp Sac PASPÉBIAC - 1 (projeté 4,5 km) A Acc++WWee T Taa TTaa T Taa N Nee N Nee T Taa?? b bssmmnntt ???? b bssmmnntt ???? 0 5 10 km O Oaarr?? 0 1000 2000 3000 Shot CMP 200 300 400 500 600 700 800 900 1000 1100 1200 1300 T W T (m s) 2001-MRN-14A 2001-MRN-14B S SEE NNWW 0 1000 2000 3000 Shot CMP 200 300 400 500 600 700 10 8 3 10 8 7 3 4 11 6 4 11 3 10 8 11 1 3

O

Om

mii

O

Om

mii

4 5

O

OS

Sm

maa

O

Oaarr

O

Oggnn

O

Oggnn

O

Oaarr

C

C--O

O

ppC

CM

Mqq

SSE

E--ddiirreecctteedd T

Taaccoonniicc tthhrruussttss

U

Uppppeerr ccrreessttaall

ccoollllaappssee ggrraabbeenn

Swp Sga_silt Sga_lime Slv Slp Sac PASPÉBIAC - 1 (projected 4.5 km) 0 5 10 km SJSF SHCA MLA DA RRAA GRF GPF Proterozoic basement 2

rreevveerrssee

ffaauulltt

zzoonnee

7 9 Clemville Fm. bottom 8 Garin Fm. top 6 Pabos Fm. top Neckwick/Arsenault Fm. top 4 Taconic unconformity 3 Maquereau Gr. top 2

Rivière du Milieu Mélange top?

5

1 Proterozoic basement ? La Vieille Fm. top

10

Anse-Cascon Fm. top

Dextral strike-slip fault

LEGEND -40 -30 -20 -10 0 10 20 0 50 100 150 200 250 m G al km

A

A'

S hi ck sh oc ks G ro up B at hu rs t

observed gravity anomaly visually fitted regional field

2001-MRN-14A 2001-MRN-14B

Figure 9. Observed gravity profile (total anomaly) extracted from the Bouguer anomaly map and

visual estimation of the regional field.

Comparison with analog models

Decomposition Residual Bouguer anomaly modelling Seismic re-interpretation Profile B Boouugguueerr A Annoommaallyy M Maapp G

Geeoollooggiiccaall M Maapp Final model W Weellll D Daattaa P

Prroocceesssseedd 22DD sseeiissmmiicc ddaattaa

d

daa ttaa qquuaa ll ii ttyy ii ss ggoooodd

False

Additional processing

Preliminary Seismic interpretation

true

Time to depth conversion

iinntteerrpprreettaattiioonn iiss v

viiaabbllee

False True

3. Method

Figure 5. Working method used to produce the structural model of

the study area. The seismic interpretation was constrained by the geo-logical map and formation tops penetrated by well Paspébiac No. 1. The seismic interpretation was converted into depth by using interval velocities derived from velocity analysis of prestack seismic data so it could be used as a constraint for the gravity modeling. An anomaly profile was extracted from the Bouguer anomaly map and was later decomposed into a regional and a residual component by the visual adjustment method. The gravity model was constrained by measured densities of the units. Through an iterative process, the results of the gravity modeling were used to modify the seismic interpretation and this new seismic interpretation was used to build a new geological model. The cross-section resulting from surface data analysis, seis-mic interpretation and gravity modeling was compared with pub-lished analog models in order to better understand the geometry and kinematic implications. P PAASSPPÉÉBBIIAACC -- 11 48,00 ° 48,00 ° 48,50 ° 48,50 ° -66,00 ° -66,00 ° -65,50 ° -65,50 ° -65,00 ° -65,00 ° -64,50 ° -64,50 °

0

10 km

Mictaw Gr. and Arsenault Fm. Maquereau Group

Neoproterozoic to Lower Cambrian

Garin Formation (Honorat Gr.)

Ordovician

Lower Chaleurs Group Upper Chaleurs Group Fortin Group

Bonaventure Formation

Carboniferous

Ordovician to Lower Silurian Matapédia Group

Silurian Devonian

Basalt and sediments

Chaleurs Bay

R RAA D DAA SSJJSSFF

The integration of 2D seismic interpretation, gravity

model-ing, and thermal maturity data reveals the superposition of

four different deformation styles, developed over four

deformation phases in the Chaleurs Bay area, Quebec,

Can-ada. The first deformation phase, the

Tremadocian-Arenigian Taconic Orogeny, is characterized by a

south-east-directed hinterland dipping duplex mostly involving

the Hadrynian-Lower Cambrian Maquereau Group. The

second deformation phase, the Late Ordovician

post-Taconic extension, is marked by the development of a

ramp-flat listric extensional fault system which controlled

the deposition of the Upper Ordovician Honorat and

Matapédia Groups. During the third deformation phase, the

Middle Devonian early stage of the Acadian Orogeny,

thrusts faults inherited from the Taconic Orogeny are

reacti-vated and normal faults inherited from the post-Taconic

extensional phase are inverted. Strike-slip faulting along

the Grand-Pabos and Garin River faults occurred during the

fourth deformation phase, the Middle to Late Devonian late

stage of the Acadian Orogeny.

45,0 ° 45,0 ° 50,0 ° 50,0 ° -75,0 ° -75,0 ° -70,0 ° -70,0 ° -65,0 ° -65,0 ° -60,0 ° -60,0 ° -55,0 ° -55,0 ° -50,0 ° -50,0 ° 0 200 km 0 50 100 km Devonian intrusives Carboniferous clastics

Gaspé Sandstones (Lower-Middle Devonian) Upper Gaspé Limestones (Lower Devonian) Chaleurs Group (Lower Silurian-Lower Devonian)

Honorat and Matapédia groups (Upper Ordovician-Lower Silurian) Taconic-deformed units (Cambrian-Upper Ordovician)

D Duunnnnaaggee Atlantic Ocean C CVVGGSS C CVVGGSS C CVVGGSS A APPAA A APPAA C CBBSS C CBBSS 47 ° 47 ° 48 ° 48 ° 49 ° 49 ° -71 ° -71 ° -70 ° -70 ° -69 ° -69 ° -68 ° -68 ° -67 ° -67 ° -66 ° -66 ° -65 ° -65 ° -64 ° -64 ° -63 ° -63 ° -62 ° -62 ° New Brunswick Maine Saint L awrenc e River H Huummbbeerr ++ D Duunnnnaaggee

SSTTU

UD

DYY AAR

REEAA

Figure 2. Main tectonostratigraphic domains of the Gaspé Belt

(modified from Lavoie, 2008). The Gaspé Belt has been subdi-vided into three tectonostratigraphic areas, which are from north to south: (1) the Connecticut Valley-Gaspé Synclinorium (CVGS), (2) the Aroostook-Percé Anticlinorium (APA), and (3) the Chaleurs Bay Synclinorium (CBS) (Brisebois and Brun, 1994; Bourque et al., 2001; Malo et al., 2008).

Figure 1. The Gaspé Belt and Taconic tectonostratigraphic

domains of the Canadian Appalachians (modified from Lavoie, 2008). The Gaspé Belt is the largest post-Taconic Successor

Basin of the Middle Paleozoic of Canadian Appalachians

(Williams, 1995). It includes a succession of Upper Ordovician to Upper Devonian sedimentary and volcanic rocks that overlies unconformably or are in fault contact with Cambro-Ordovician units belonging to the Humber, Dunnage and Gander (Lower Paleozoic) Zones (Brisebois and Brun, 1994; Bourque et al., 2001; Malo, 2001; Malo et al., 2008).

2. Introduction

Regional Stratigraphy and Seismostratigraphy

4. 2D Seismic

5. Gravity Data Modeling

20 01 -M R N -1 4A & B

A’

A

The Gaspé Belt

Figure 3. Geologic map showing location of

seis-mic lines 2001-MRN-14A and 2001-MRN-14B

and well Paspébiac-1, north of Chaleurs Bay. DA:

Duval Anticline; RA: Robidoux Anticline; SJSF:

Saint-Jogues Sud Fault (modified from: Pinet,

2013). The Chaleurs Bay Synclinorium contains

an assemblage of regional NE-SW-trending folds

and major E-W and NE-SW-trending faults,

most-ly involving rocks of the Upper Ordovician

Matapedia Group and the Silurian Chaleurs Group.

Figure 4. Lithostratigraphy and seismostratigraphy of the Chaleurs

Bay Synclinorium and the Aroostook-Percé Anticlinorium. CB +

MC: Corner of the Beach and Murphy Creek formations; NOM:

Nadeau ophiolitic Mélange; MRM: Milieu River Mélange (modified from: Bourque et al., 2001; Jutras and Prichonet, 2002; Malo, 2004, De Souza et al., 2012; Marcil et al., 2005.)

Figure 8. Location of the gravity profile and the seismic lines MNR-14A and

2001-MRN-14B in the Bouguer anomaly map of the Gaspé Peninsula (modified from: Pinet et al.,

2005).

Figure 7. Structural interpretation of seismic lines

2001-MRN-14A and 2001-MNR-14B. DA: Duval Anticline; LMA: Lake

Ménard Anticline; RA: Robidoux Anticline; SHCA:

St-Hélène-de-la-Croix Anticline; SJSF: St-Jogues South Fault; GPF:

Grand Pabos Fault; RGF: Garin River Fault; Oar: Arsenault

Formation; Ogn: Garin Formation; Omi: Mictaw Group;

OSma Matapedia Group. pCMq: Maquereau Group. For

loca-tion, see figure 3.

Figure 6. Envelope representation of pre-stack

migrated 2001-MNR-14A and 2001-MNR-14B

seis-mic lines. Ac-We: Anse-Cascon and Weir Fms; Ar:

Arsenault Fm; Ne: Neckwick Fm. top; Ta: Taconic

unconformity. For location, see figure 3.

In our interpretation, the faults that cut across the

Silurian rocks at the surface also affect the

under-lying Cambrian-Lower Ordovician rocks. As for

the Grand Pabos and the Garin River strike-slip

faults, the interpretation suggests subvertical dips,

with a connection of both faults at depth. Low

amplitude, short wavelength folds and reverse

faults with a small throw involving

Cambro-Ordovician (sub-Taconic unconformity) units have

been interpreted as a system of partially inverted

normal listric faults (Gibbs, 1984). Reflections of

the Upper Ordovician Garin Formation (Honorat

Group) onlapping on the Taconic unconformity

mimic the syn-rift units onlap at the crest of the

roll-over anticline, illustrated by scaled analog

models of ramp-flat listric extensional fault

sys-tems (McClay, 1995). Divergent reflections

attributed to syn-rift units of the Matapedia

Group, south of the Garin River Fault, are

com-patible with an episode of post-Taconic extension.

Based on the comparison to a scaled analog

mod-el, major Acadian folds of the Chaleurs Bay

Synclinorium are interpreted as the result of

tectonic inversion of a post-Taconic upper

crestal collapse graben (McClay, 1995).

mm

aaiinn

ll

iisstt

rr

iicc

ee

xxttee

nn

ssii

oo

nnaall

ff

aa

uulltt

22 00 00 11 --MM RR NN --1144 BB 2200 0011 --MM RR NN --11 44AA

G

Grr

aa

nn

dd PPaabbooss FF

aa

uulltt

G

G

aa

rrii

nn

R

R

ii

vv

ee

rr

FFaa

uull

tt

Amplitude 0 10 0 0 0 2 0 0 0 0

Figure 10. Gravity data modeling. C-O: non-metamorphosed Ordovician. MLEF: Main Listric

Exten-sional Fault. pCMq: Maquereau Group. Oar: Arsenault Formation. Ogn: Garin Formation. Omi: Mictaw Group. OSma: Matapedia Group. Schi: Lower Chaleurs Group. Schu: Upper Chaleurs Group.

Diego Tovar

1

, Michel Malo

1

, Mathieu J. Duchesne

2

, and Nicolas Pinet

2

1

Institut national de la recherche scientifique, Centre Eau Terre Environnement

2

Geological Survey of Canada

Geometric and Kinematic Reconstruction of the Chaleurs Bay Synclinorium (Gaspé Belt)

through the Integration of Geological and Geophysical Data

9. Conclusions

The integration of geological data, 2D seismic reflection, gravity modeling, and thermal maturity data from the Chaleurs Bay Syn-clinorium, reveals the superposition of four different deformation styles, developed over four distinct deformation episodes. Our study lead to several new findings that bear significant implica-tions on the geological evolution model and petroleum potential of the area : (1) the existence of Taconic thrust sheets with the southeast tectonic transport suggests that the Taconic orogen in the Gaspé Peninsula is a doubly vergent orogen; (2) major Acadian folds of the Chaleurs Bay Synclinorium are interpreted as the result of tectonic inversion of a post-Taconic upper crestal collapse graben (McClay, 1995); (3) the coexistence of rock units with contrasting burial histories is interpreted as the result of post-Taconian extension normal motions along a major, previous-ly poorprevious-ly documented, fault; (4) the high organic content shales of the Mictaw Group, located in the footwall of the post-Taconian normal fault, experienced less burial than correlative rocks found in the hanging wall and preserved a significant hydrocarbon potential.

Acknowledgements

The first author acknowledges the Institut national de la

recher-che scientifique (INRS) for the financial support and Junex Inc.

for providing the reprocessed version of the seismic line 2001-MNR-14A.

Bêche, M., Kirkwood, D., Jardin, A., Desaulniers. E., Saucier, D., and Roure, F., 2007. 2D depth seismic imaging in the Gaspé Belt, a structurally complex fold and thrust belt in the Northern Appalachians, Québec, Canada. In: Thrust Belts and Foreland Basins: From Kinematics to Hydrocarbon Systems. Lacombe, O., Lavé, J., Roure, F.M., Vergés, J. (Eds.), Springer, p. 75-80.

Bourque, P.-A., Gosselin, C., Kirkwood, D., Malo, M., and St-Julien, P., 1993. Le Silurien du segment appalachien Gaspésie-Matapédia- Témiscouata: stratigraphie, géologie structurale et paléogéographie. Ministère de l’Énergie et des Ressources du Québec, MB 93-25, 115 pp.

Brisebois, D., Lachambre, G., and Piché, G., 1991. Carte géologique Péninsule de la Gaspésie. Carte 2146 - DV 91-21, Ministère de l’Énergie et des Ressources, Québec. Échelle 1:250 000.

Brisebois, D. and Brun, J., 1994. La plate-forme du Saint-Laurent et les Appalaches. In: Hocq, M. and Dubé, C. (Eds.), 1994, Géologie du Québec, Les Publications du Québec, Ministère des Ressources Naturelles, MM 94-01, 154 pp.

De Broucker, G., 1987. Stratigraphie, pétrographie et structure de la boutonnière de Maquereau - Mictaw (Région de Port-Daniel, Gaspésie). Ministère de l’Énergie et des Ressources du Québec, MM 86-03.

Gibbs, A.D., 1984. Structural evolution of extensional basin margins. Journal of the Geological Society, v. 141, p. 609-620.

Junex Inc., 2008. Junex Paspébiac #1 (C-133). Rapport de fin de forage. Projet : 3014-017. Permis : 2001PG589. Québec (Québec), 31 pp + annexes.

Kirkwood, D., 1999. Palinspastic restoration of a post-Taconian successor basin deformed within a transpressive regime, northern Appalachians. Tectonics, v. 18, p. 1027-1040.

Kirkwood, D., Lavoie, M., and Marcil, J., 2004. Structural style and hydrocar-bon potential in the Acadian foreland thrust and fold belt, Gaspé Appalachians, Canada. Dans: R. Swennen, Roure, F. and Granath, J. (Eds.), Deformation, fluid flow, and reservoir appraisal in foreland fold and thrust belts, AAPG Hedberg Series, no. 1, p. 412- 430.

Lachambre, G. and Brisebois, D., 1990. Géologie de la Gaspésie / compilé par G. Lachambre et D. Brisebois à partir des travaux inédits de D. Brisebois et A. Slivitzky. Gouvernement du Québec, Ministère des Ressources naturelles, Secteur des mines. Échelle 1:50,000.

McClay, K.R., 1995. 2D and 3D analogue modelling of extensional fault struc-tures: templates for seismic interpretation. Petroleum Geoscience, v. 1, p. 163-178.

Pinet, N., Lavoie, D., Brouillette, P., Dion, D.-J., Keating, P., Brisebois, D., Malo, M., and Castonguay, S., 2005. Gravimetric and aeromagnetic atlas of the Gaspé Peninsula. Geological Survey of Canada, Open File 5020, 68 pp.

Pinet. N., Keating, P., Brouillette, P., Dion, D.-J., and Lavoie, D., 2006. Produc-tion of a residual gravity anomaly map for Gaspésie (northern Appalachian Mountains), Quebec, by a graphical method. Geological Survey of Canada, Current Research 2006 -D 1, 8 pp.

Pinet, N., 2013. Gaspé Belt subsurface geometry in the northern Québec Appa-lachians as revealed by an integrated geophysical and geological study: 2 - Seis-mic interpretation and potential field modelling results. Tectonophysics, v. 588, p. 100-117.

Roy, S., 2008. Maturation thermique et potentiel pétroligène de la ceinture de Gaspé, Gaspésie, Québec, Canada. Thèse. Québec, Université du Québec, Institut national de la recherche scientifique, 459 pp.

St-Julien, P. et Hubert, C., 1975. Evolution of the Taconian Orogen in the Québec Appalachians. American Journal of Science, v. 275A, p. 337-362.

References

8. Kinematics and Timing of Deformation

Figure 13. Structural evolution of the Chaleurs Bay Synclinorium and the Aroostook-Percé

Anti-clinorium. APA: Aroostook-Percé Anticlinorium; Ar: Arsenault Formation; CBS: Chaleurs Bay Synclinorium; Ch: Chaleurs Group; C-O: non-metamorphosed Cambro-Ordovician; CVGS: Con-necticut Valley-Gaspe Synclinorium. DA: Duval Anticline; Ga: Garin Formation; GPF: Grand Pabos Fault; GRF: Garin River Fault; Mi: Mictaw Group. Mq: Maquereau Group; Mt: Matapedia Group; RA: Robidoux Anticline; SJSF: Saint-Jogues Sud Fault.

1. Summary

In t h e C h a l e u r s B a y S yn c l i n o r i u m , m o s t o f

outcropping rock units are in the condensate to dry gas

windows and exhibits a constant decrease in the

aver-age estimated vitrinite equivalent-reflectance values

from the base to the top of the stratigraphic column. A

notable exception corresponds to the Mictaw Group, at

the base of the stratigraphic succession, which is still

in the oil-window (Roy, 2008). This contrasting history

is compatible with the development of a major

unmapped post-Taconic listric extensional fault,

locat-ed between the Mictaw Group (Port-Daniel area) and

the Matapédia Group (Duval Anticline). According to

our model, rocks of the Mictaw Group, in the footwall

(southeast) of this fault, were preserved from

signifi-cant post-Taconic burial, while syn-extension strata

were deposited during the post-Taconic extension

phase, in the hanging wall (northwest) of this fault. For

the CBS, the Ordovician Mictaw Group (Dubuc

Formation) is a potential source rock of hydrocarbons,

reaching TOC values higher than 3.0% with organic

matter type II (Malo et al., 2008; Roy, 2008).

A Acc++WWee

C

C--O

O

? ? 9 Ophiolite

High-grade metamorphics Nearshore sandstones

Terrestrial conglomerate Mélange

Deep water limestones

Platformal limestones Fine-grained siliciclastics Volcanics

Deep water mudstones and sandstones

M at ap éd ia G r. Lo w er C ha le ur s G r. U .C ha le ur s G r.

The Taconic orogeny (Tremadocian-Arenigian,

figs 13.1 - 13.3

) is characterized by the

emplacement of a SE-directed hinterland dipping duplex involving the Maquereau

Group.

Time correlative Arsenault Formation and Mictaw Group are deposited during a relatively

quiescent interval (Darriwillian-Caradocian,

fig 13.4

).

The post-Taconic extension (Caradocian-Rhuddanian,

fig 13.5

) is characterized by the

deposition of the Honorat and Matapedia Groups during the development of a ramp-flat

listric extensional fault system (Gibbs, 1984) involving the Proterozoic basement.

The occurrence of a relatively quiescent period (Rhuddanian - Pridolian,

fig 13.6

) is

sup-ported by the relatively constant thickness and the absence of documented

syn-sedimentary faults in the Chaleurs Group.

The Acadian Orogeny (Middle to Late Devonian) can be divided into two distinct

phas-es: an early phase of shortening

(fig 13.7)

, followed by a late phase of dextral strike-slip

faulting

(fig 13.8)

. In our interpretation, folds are generated by reactivation of old

Taconic thrusts and inversion of post-Taconic normal faults with tectonic transport to

the southeast. The late dextral strike-slip faulting is represented by the Grand Pabos fault

system which displaced the early Acadian regional folds.

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