Tectonophysics, 172 (1990) 303-322 303 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands Reconstructions of the Arctic: Mesozoic to Present * H. RUTH JACKSON ‘* * and KARL GUNNARSSON ’ Department of Geology, University of Oslo, Oslo (Norway) 2 National Energy Authority, Reykjavik (Iceland) (Received September 8, 1988; revised version accepted July 11, 1989) Abstract Jackson, H.R. Gunnarsson, K., 1990. Reconstructions of the Arctic: Mesozoic to Present. Tectonophysics, 172: 303-322. Plate r~ns~ct~ons using both geological and geophysi~l data are reviewed and examined. The Arctic Ocean opened in three stages: anomaly 24/25 time to the present when documented seafloor spreading occurred in the Eurasia Basin. The middle event occurred from anomalies 34 to 25 when interaction of the North American and Eurasian plates caused crustal shortening or strike-slip motion in the Arctic. The first event occurred from prior to anomaly 34 time when the Amerasia Basin opened by a rotation with some translation about a pole near the Beaufort-Mackenzie Basin. Crustal shortening caused by this rotation may have been accommodated in the Brooks Range and in the South Anyui Suture Zone. The Alpha Ridge was formed during the opening of the ocean but was not the spreading centre. It is a feature similar to the Iceland-Faeroe Ridge. Prior to the onset of seafloor spreading in the Amerasia Basin the circum-Arctic sedimentary basins formed during a long period of rifting. Introduction in the Arctic just prior to anomaly 24/25 occurred in the Amerasia Basin, probably involved com- pression and/or strike-slip motion that is not as The Arctic Ocean can be divided into the well constrained as the most recent stage. The lack Eurasia and the Amerasia basins, where the of clearly defined seafloor spreading anomalies in Amerasia Basin includes the Canada and the the Amerasia Basin has prevented detailed recon- Makarov subbasins (Fig. 1). The Cenozoic plate structions and has led to many and varied hy- motions in the Arctic were focused in the Eurasia potheses for its opening. Basin. Since marine magnetic anomalies 24/25 There is a consensus that the Eurasia Basin seafloor spreading has been taking place in the opened by seafloor spreading about the Arctic Eurasia Basin contemporaneous with the seafloor Mid-Ocean Ridge (Pitman and Talwani, 1972; spreading in the North Atlantic and in the Nor- Herron et al., 1974; LePichon et al., 1977; Kris- wegian-Greenland Sea. The plate reconst~ctions toffersen and Talwani, 1977; Srivastava, 1978, developed for this area and time are well con- 1985; Burke, 1984; Vink, 1984; Reksnes and strained and changes to existing models will con- Vagnes, 1985; Srivastava and Tapscott, 1986; cern details only. In contrast, interaction of plates Smith, in press). However, many suggestions have been made for the development of the Amerasia Basin. Three groups of workers support the idea that the Amerasia Basin was created by in-situ seafloor spreading but disagree on the location * Geological Survey of Canada Contribution 2234. ** On leave from Atlantic Geoscience Centre, Geological and direction of the spreading. Group one advoc- Survey of Canada, Dartmouth, N.S., Canada). ates that the Amerasia Basin (Fig. 1) opened by ~~1951/~/$03.50 Q 1990 Elsevier Science Publishers B.V. H.R. JACKSON AND K. GUNNARSSON ACTIVE ACTIVE FOSSIL TRANSFORM SPREADING a - SUBDUCTION + CENTRE FAULT ZONE FOSSIL = f2 - %?~'OING -$ - TRANSFORM v- CENTRE FAULT Fig. 1. General location chart of the major bathymetric features in the Arctic Ocean. The plate boundaries are illustrated. the rotation of Alaska away from the Canadian spreading, is that the oceanic crust in the Amerasia polar margin (Carey, 1958; Tailleur, 1969; Basin was formed in the Pacific Ocean and trapped Rickwood, 1970; Grantz et al., 1979, 1981; Har- in its present location (Churkin and Trexler, 1980). land et al; 1984). A second possibility is that the A fifth theory, the oldest, is that the crust was basin opened when Alaska sheared along the formed by oceanization (Beloussov, 1970; Pogre- Canadian polar margin (Christie, 1979; Kerr, 1980; bitskkiy, 1976). Jones, 1980, 1982). A third idea is that the ocean The objectives of this paper are to review and crust in the basin may have been formed by evaluate the plate tectonic models suggested for complex spreading patterns by the motion of two the evolution of the Arctic Ocean based on data or more small plates (Vogt et al., 1982). A fourth available up to 1988. This was done in three stages theory, that is not based on in-situ seafloor (Fig. 2). In stage III (from the present to anomaly RECONSTRUCTIONS OF THE ARCTIC: MESOZOIC TO PRESENT 305 DEVELOPMENT Amerasia Basin (Sweeney, 1985). These recon- M.Y. ANOMALY OF THE ARCTIC OCEAN structions are based on poles that are suggested in the literature, which we tested by actually doing the rotations. The continent-ocean transition was F - 20 chosen as the 2000 m bathymetric contour along the polar margins. Lack of data prevented a more : 4 -30 KSRFA OPENS u-F _ 13 accurate boundary definition. This contour in- k - 40 cluded the Alpha Ridge on the NA plate. It is 2 drawn in not because it is considered as continen- 5 -50 _ 24 tal crust but to provide a reference for the reader. - 60 On the AA plate the 2000 m contour includes the ~O~H;FlESSION - 70 Chukchi Borderland whose crust is of uncertain ARCTIC? p -90 -33 origin and the Mendeleev Ridge which is consid- 4 34 OPENING ered to be part of the Alpha Ridge in most but not 2 - 90 OF THE AMERASIA all of the reconstructions. The plates are rotated to 0 POSITIVE BASIN W-_ where the 2000 m contours, excluding the ridges 0 100 L r%~” 2 k! - 110 and borderland, overlap and the geological conse- quences of closing the ocean in adjacent regions o> 2 - 120 MO are noted and discussed. z5 - 130 PM10 Geophysical data from the Eurasia Basin in stage III, such as magnetic anomalies, provide DEVELOPMENT OF THE strong constraints for the plate reconstructions; CIRCUM-ARCTIC SEDIMENTARY BASINS geophysical constraints from the interaction of the NA and EU plates in the middle stage are used to predict plate motions in the Arctic; in contrast, geological data from the sedimentary basins adjac- I ent to the Amerasia Basin in the first stage are used to constrain the sparse geophysical data pre- sently available. As we progressed from last to the Fig. 2. Development of the Arctic Ocean first stage increasing reliance is put on the geo- logical controls. 24/25; Reksnes and Vagnes, 1985; Srivastava and Stage III Cenozoic evolution: anomaly O-24/25 Tapscott, 1986) the Eurasia Basin opened. For this stage published poles are used that relied on Since the time of magnetic anomaly 24/25, the matching magnetic anomalies and the trends of Eurasia Basin has been opening along the Arctic fracture zones in the North Atlantic, the Mid-Ocean Ridge, the northernmost extension of Norwegian-Greenland Sea, Eurasia Basin and the spreading axis between the North American Labrador Sea. During stage II (from anomaly plate and the Eurasian plate (Kristoffersen and 25-34) compression may have occurred between Talwani, 1977; Srivastava, 1978,1985; Vink, 1982; the North American (NA) and Eurasian (EU) Srivastava and Tapscott, 1986). The fit of the plates (Srivastava and Tapscott, 1986). In this magnetic anomalies from 50”N to and including interval the matching of magnetic anomalies and the Eurasia Basin is shown in Fig. 3. trends in the North Atlantic are used to predict However, when the magnetic anomalies from the motion of the NA and EU plates in the Arctic. the opposite sides of the spreading axis are super- During the period before anomaly 34 (84 m.y.) imposed there are some complications and dis- back to approximately the beginning of Aptian crepancies that occur on the landmasses and in time (118 m.y.), stage I, seafloor was created in the the oceans. For example, overlap occurs between 306 H.R. JACKSON AND K. GUNNARSSON Fig. 3. Plate-tectonic reconstructions for the North Atlantic, Norwegian-Greenland seas and the Eurasia Basin, Arctic Ocean, for the period between anomaly 13 and 25 from Srivastava (1985). The superimposed circles and squares represent the magnetic anomalies from adjacent plates. The dashed and solid lines are the continent-ocean boundaries of the plates. RECONSTRUCTIONS OF THE ARCTIC: MESOZOIC TO PRESENT 307 the continental shelves of Greenland and Svalbard Rise and the magnetic anomalies indicate this (Vink, 1982; Smith, in press). It is unclear whether feature is oceanic. On the Yermak Plateau refrac- the plates in this area behaved in a non-rigid tion and magnetic data are consistent with the manner or whether better definition of the conti- northern section being of oceanic origin (Fig. 4) nent-ocean boundary will resolve the problem. and only the southern being of continental origin. Srivastava and Tapscott (1986) explain the overlap Thus, these plateaus are not impediments to the with a combination of strike-slip motion and plate reconstructions. crustal stretching and thinning. A third problem is that no single pole satisfies A second problem occurs in the reconstructions the anomalies in the No~e~an-Greenland Sea north of Greenland for anomalies 13 and 24 time and the Labrador Sea (Kristoffersen and Talwani, with the overlap in the Morris Jesup and Yermak 1977; Talwani and Eldholm, 1977; Srivastava, plateaus (Fig. 1). A triple junction existed in the 1978); however, these three discrepancies are not area during this interval (Feden et al., 1979). The large and do not indicate first order non-rigidity oceanic or continental origin of these features has in the plates.