Cenozoic relative movements of Greenland and North America by the closure of the North Atlantic – Arctic plate circuit: The Labrador Sea, Davis Strait & Baffin Bay

Annabel Causer 1 Graeme Eagles 2, Lucía Pérez-Díaz 3, Jürgen Adam1 1. Royal Holloway, University of London, Egham, UK 2. Alfred Wegener Institute, Bremerhaven, Germany 3. Oxford University, Oxford, UK

Aims:

Investigate the relative kinematic evolution of the Greenland and North America plate pair in terms of opening of the Labrador Sea, evolution of the Davis Strait and Baffin Bay regions from the Paleocene to the Eocene-Oligocene boundary.

By using seafloor spreading data (magnetic anomaly isochrons of undisputed oceanic origin and fracture zone traces) from the North Atlantic and Arctic Ocean.

To do this… Present day configuration of the Greenland, North America and Eurasian Plates. Black and white lines are spreading centres. Black dashed lines are fracture zones and black solid lines are transform faults. The red dashed line marks the plate boundary between Greenland and North America along the Canadian Arctic. Abbreviations as follows: AR; Aegir Ridge, BB; Baffin Bay, DS; Davis Strait EUR; Eurasia, GRN; Greenland, JM; Jan Mayen Microcontinent, KR; Kolbeinsey Ridge, LS; Labrador Sea, NAM; North America, SFS; Seafloor Spreading.

Cenozoic relative movements of Greenland and North America by closure of the North Atlantic – Arctic plate circuit: The Labrador Sea, Davis Strait & Baffin Bay 2 Method:

We produce two independent models describing:

1 Eurasian – North American (EUR-NAM) plate divergence from the Late Cretaceous to present day.

2 Greenland – Eurasian (GRN-EUR). divergence according to the Iceland – Irminger Basins from Paleocene to Eocene – Oligocene Boundary (GES* - C13, 56-54 to 33 Ma).

3 Generate a new Greenland – North America (GRN-NAM) plate model which depicts the opening of the Labrador Sea by adding our new GRN-EUR rotations to those Present day configuration of the Greenland, North America and Eurasian Plates. Black and white lines are spreading of EUR-NAM. centres. Black dashed lines are fracture zones and black solid lines are transform faults. The red dashed line marks the plate boundary between Greenland and North America along the Canadian Arctic. Abbreviations as follows: AR; Aegir Ridge, BB; Baffin Bay, DS; Davis Strait EUR; Eurasia, GRN; Greenland, JM; Jan Mayen Microcontinent, KR; Kolbeinsey Ridge, LS; Labrador Sea, NAM; North America, SFS; Seafloor Spreading.

Cenozoic relative movements of Greenland and North America by closure of the North Atlantic – Arctic plate circuit: The Labrador Sea, Davis Strait & Baffin Bay 3 GRN-EUR + NAM-EUR = GRN-NAM

3 Finite rotation poles for the Greenland and North American plate model. Coloured confidence ellipses are generated by combining 95% confidence estimates from the North American and Eurasian, and 1 2 the Greenland and Eurasian plate models. GES; Greenland – Eurasia Shale Edge. Red line and black points represent finite rotation poles from Roest & Srivastava, (1989). Blue line and black points EUR-NAM finite rotation poles with associated 95% GRN-EUR finite rotation poles with associated 95% represent finite rotation poles from Oakey & Chalmers, (2012), C21/C24* shows two rotation poles in confidence ellipses. Grey poles are from the study confidence ellipses. GES; Greenland – Eurasian Shelf edge. the same location. by Gaina et al., (2009). Grey poles are from the study by Gaina et al., (2009). Cenozoic relative movements of Greenland and North America by closure of the North Atlantic – Arctic plate circuit: The Labrador Sea, Davis Strait & Baffin Bay 4 Labrador Sea Our Model Shows:

 Strong obliquity in the earliest Eocene (C24 – C22).

 Circuit-based flowpoints return LS isochrons C21-C24 within 95% uncertainty.

 GES flowpoints do not fall inside circuit 95% uncertainty; GRNEUR breakup in I-I basins likely post-dated C25 slightly.

 Seafloor spreading in the Labrador Sea ceased sometime between C20 and C13; 42 – 33 Ma.

 Resolvable relative motion after C13, but too small to be accommodated by spreading. Ridge crest flowlines from the Greenland and North America plate model, with their respective 95% confidence ellipses. Synthetic ridge- crest flowlines both originate at a common along the extinct spreading centre in the Labrador Sea. Magnetic anomalies C21, C24 and C25 according to Klitgord & Shouten, (1986) and C22 Gaina et al., (2002). Cenozoic relative movements of Greenland and North America by closure of the North Atlantic – Arctic plate circuit: The Labrador Sea, Davis Strait & Baffin Bay 5 Davis Strait

Our Model Predicts:

 A period of N-S to NNW-SSE transpression from the early to mid Eocene (GES - C22; 57 – 49 Ma), consistent with the formation of the Davis Strait High.

 From Mid-Eocene (C22; 49 Ma) the Davis Strait is predominately strike slip.

 Renewed oblique compression until the Eocene- Oligocene boundary (C13; 33 Ma)

 Post-C13 orthogonal (NW-SE) extension of the DS High.

Whole plate flowlines from the Greenland and North America plate model, with their respective 95% confidence ellipses. North America is stationary. Synthetic whole plate flowlines originate at a point along the Davis Strait High. Crustal interpretation of Oakey & Chalmers, (2012) courtesy of Tabea Altenbernd. Cenozoic relative movements of Greenland and North America by closure of the North Atlantic – Arctic plate circuit: The Labrador Sea, Davis Strait & Baffin Bay 6 Baffin Bay

Our Model Predicts:

 A period of N-S to NNW-SSE extension from the early to mid Eocene (GES - C21; 57 – 46 Ma), consistent with orientation of transform faults.

 Baffin Bay is subject to mid to late Eocene (C21- C13; 46 – 33 Ma) compression.

Does our predicted period of compression explain inversion structures along the margins of Baffin Bay?

Synthetic ridge-crest flowlines from the Greenland and North America plate model, with their respective 95% confidence ellipses. Generated from two seed points along the Eocene spreading axis. Crustal interpretation of Oakey & Chalmers, (2012) courtesy of Tabea Altenbernd. Cenozoic relative movements of Greenland and North America by closure of the North Atlantic – Arctic plate circuit: The Labrador Sea, Davis Strait & Baffin Bay 7