Geological Setting

The Jeanne d’Arc Basin is a small failed-rift basin, which is one of several rift basins comprising The Grand Banks (Deptuck, 2003). 

The Grand Banks is an extensive continental shelf, which is located near the eastern coast of Newfoundland. It is partially underlain by complex series of fault-bounded rift basins including the Whale, Horseshoe, Jeanne D’Arc, and Carson Bonnition (Spila, 2005)(Fig. 1). 

The Grand Banks area is limited by the Bonavista Platform to the west, the Cumberland Belt Transfer Fault Zone to the north, the continent-ocean boundary (COB) to the east and the Newfoundland Transform Fault Zone (NFTZ) to the south.

Fig. 1 Grand Banks of Newfoundland. (from Enachescu and Fagan, 2004).

The Jeanne d’Arc Basin is the deepest of The Grand Banks basins. It has a funnel shape and contains more than 20 km of Mesozoic and Cenozoic sedimentary fill. The basin covers a huge area(10 000 km2) and extend 250 km in N-S direction and about 80 km in EW direction (Enachescu and Fagan, 2004).

 Basin evolution and litostratigraphy

 

The Jeanne d’Arc Basin and other basins comprising the Grand Banks were formed during the Early Mesozoic break-up of the Pangea and birth of the Atlantic Ocean.

The Jeanne d’Arc Basin is filled by Triassic to up Recent in age deposits. The studying of this deposits shows that there were two or probably three episodes of ocean opening (Spila, 2005).

Initial Rifting

The development of basin begun in the Late Triassic to Eraly Jurassic (Early Carnian-Mid Pliensbach). It started with the process of rifting. The North Atlantic didn’t open in every place in the same time but progressed sequentially from south to north. At this phase of rifting the main basins were created in the form of half-garbens. This newly created valleys was firstly filled with continental siliciclatics, conglomeraltes, mostly red beds (the Euridice Formation). They were deposited in the arid continental environment. 

Regions of low relief were inundated by the sea and the precipitation of evaporates was started (from the Upper Rhaethnian to the Lower Sinemurian). Evaporites have different thickness and they are rich in halite. This precipitates are represented by the Argo Formation. 

After episode of evaporation marine limestones of the lower Iroquois Formation were deposited. This limestones were turned into anhydritic dolomites intercalated in some place by thin evaporates layers in process of alteration, which occurred afterwards. 

At this phase the emplacement of igneous dykes also occurred. 

This episode was terminated before any oceanic crust was generated (Spila, 2005)(Fig.2a).

First Thermal Sag

This phase lasted from Mid-Pliensbachian to Kimmeridian time. This period is characterized by slow, thermal subsidence. This process was the cause of the formation of a broad epicontinental sea. Under this condition the thick succession of shales and limestiones were deposited (the Downing, Voyager and Rankian Formations). They were deposited in conditions ranging from marginal marine deltaic to deeper marine. Another deposits which deserve on a big attention are Early Kommeridgian organic-rich shales (the Egret Member). They were deposited in a basin with anoxic bottom waters and they are the important oils source in the basin. Between the stage of sag marks and reactivation of the rift system time is a gap in a rock sequence (hiatus). This unconformity characterize rebirth of extension and the begging of the development of Avalon Uplift (Spila, 2005)(Fig.2a). 

Fig. 2 a The most important princilpes of rift basin evolution in the North Atlantic Ocean. b Generalized cross-section between Newfoundland and Iberia c the Jeanne d'Arc structure and deposits based on interpretation of seismic datas. (from Einsele, 1992 after Tankard and Welsink, 1988).

Reactivation and Syn-rift Deposition

The second phase of rifting was started in the Late Jurassic (the Upper Kimmeridgian-Lower Tithonian). The wide extention of crust was accomplished along detachment faults. The Jeanne d’Arc basin was reactivated again along the Egret Fault, which forms the southern boundary of JDB now. The process of tectonically uplift occurred (The Avalon Uplift). This was a cause of widespread erosion, which started subsequently. Erosion of uplifted regions led to formation of large quantities of clastic debris, which were deposited in the rejunevated garbens (Spila, 2005).
During this time three of the four main reservoirs were developed: The Jeanne D’Arc, Hibernia and Catalina reservoirs. The Jeanne d’arc Formation is represented by coarse clastics which were deposited within fluvial-dominated incised valleys during Tithonian time. This unit is overlied by Fortune Bay Formation represented by shales and siltstones. They were deposited in a progradational marginal marine to neritic environment. The changing of conditions of sediment deposition is probably caused by long-term subsidence variations, combined with eustatic sea level change. The Hibernia Formation contains medium to coarse-grained sandstone, which are intercalated with shales and siltstones deposited in a northward prograding fluvial-deltaic system. This package of syn-rift strata is evidence of the development of syn-tectonic structures which are connected with the synchronous continuation of basement stretching, formation of salt diapirs and sedmentary faulting (Spila, 2005)(Einsele, 1992).

Second Thermal Sag

The B Marker Member is a unit representated by a limestone and indicates the beginning of a second period of basin stability. It lies above the Hibernia Formation and it is a great regional stratigraphic and seismic marker. The Catalina Unit lies above and is represented by fine-grained sandstones, siltstones, shales and limestones indicate a return to deposition in nearshore marine to probably paralic environments. The Whiterose Formation which contains silty shales, was deposited distally to, and above, the interbedded Catalina sandstones and shales. Another deposit, which is laterally continuous is limestone. It represents The “A” Marker member and it lies above the Whiterose Formation. In some parts of basin was deposited oolitic and bioclastic-rich sandstones, which belong to the Avalon Formation. This marine sandstones shows coarsening-upward trend, which indicates a regressive phase of basin infilling (Spila, 2005).

Fig. 3 Litostratigraphy of the Jeanne d'Arc Basin. (from Spilla, 2005, after Sinclair, 1988).

Final reactivation and syn-rift deposition

During the Baaremian or Aptian time took place a latest great-scale deformation in the Jeanne d'Arc Basin. This episode is recorded as series of normal fault dominated by NW-SE direction. Time of these deformation is considered as synchronic with final stage of rifting of continental crust on the northern Grand Banks.

Some of the formations contain plastics layers such as salts of the Argo Formation or shales of the Downing, Fortune Bay and Whiterose Formations, which were deformed by several folding during the Aptian-Albian time. Intrusions of diapirs were very common during this time .

In the course of this stage the folding had very important influence for distribution of individual stratigraphic units in the Jeanne d'Arc Basin. Their arrangement indicates a strong differentiation of rates of accomodation space creation.

Due to this processes the Avalon Formation deposition stopped and a long-term transgression has begun. This interval indicates the “Avalon” unconformity.

Above the “Avalon” unconformity under the transgressive conditions were deposited marginal to shallow marine sandstones representing the Ben Nevis Formation. The difference in deposition environment of this sandstones was a result of growing of accommodation space and of huge quantities of siliclastic sediment coming from the raised rift margins. At the same time in deeper zones of the basin were deposited shales. They are represented by the Nautilus Formation.

It is believed that these sediments indicates the transition between the final rifting event and the final thermal sag (Spila, 2005).

Final Thermal Sag

The fault-bonded margins of the Jeanne d’Arc Basin were inundated In the Cenomania time. The continued high-rate subsidence led to decrease of siliclasitc sediment supply (subsiding region become straved of clastics) and deposition of finning-upward sequences. Then, the outbuilding of shelf took place.  

Post break-up mature ocean phase in late Cretaceous and Tertiary is represented by shelf sediments such as pelagic carbonates and silty clays (Spila 2005)(Fig. 3). 

Fig.4 Geological cross-section A-A1 of Jeanne d'Arc Basin. (from Enachescu & Fagan, 2004, after Enachescu, 1994).

Bibliography

Deptuck M., 2003. Post-rift geology of The Jeanne d’Arc Basin, With a focus on the architecture and evolution of Early Paleogene submarine fans, and insights from modern deep-water system. – doctor thesis, Dalhousie University, Novia Scotia, 64-7.

Einsele G., 1992. Sedimentary Basins. Evolution, Facies, Budget and Sediment Budget, Springer-Verlag, 433-443.

Enachescu & Fagan, 2004. Newfoundland and Labrador Call for Bids NF04-01, Government of Newfoundland and Labrador, Department of Natural Resources, 35p, 14-18.

Spila M., 2005. Application of Ichnology in the Paleoenvironmental Reconstuction and Reservoir Characterization of the Avalon Ben Navis Formations, Hibernia Field, Jeanne d’Arc Basin, Grand Banks of Newfoundland, doctor thesis, University of Alberta, 7-18.

Suarez B., 2012. Evolution of the Jeanne d’Arc Basin, offshore Newfoundland, Canad: 3 D seismic evidence for>100 million years of rifting, master thesis, The State University of New Jersey, 1-3.