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Paleomagnetic Evidence for a Paleo-Mesoproterozoic Supercontinent Columbia
Gondwana Research, V; 5, No. 1, p p . 207-215. 02002 International Association for Gondwana Research, Japan. ISSN: 1342-937X
Gondwana Research
Paleomagnetic Evidence for a Paleo-Mesoproterozoic Supercontinent Columbia Joseph G. Meert1t2 University of Florida, Department of Geological Sciences, 241 Williamson Hall, Gainesville, FL 32611, U S A Norwegian Geological Survey, Geodynamics Division, Leiv Eirikssons vei 39, 7491 Trondheim, Norway (Munuscript received May 1, 2002; accepted July 2,2002)
Abstract
...
Pre-Pangea supercontinents have been proposed for Neoproterozoic and earlier times. Most of the configurations are based on analyses of geologic and structural evidence, but the only quantitative method for testing the proposed configurations is paleomagnetism. Unfortunately, the current paleomagnetic database is of limited use in evaluating the notion of a Paleo-Mesoproterozoic supercontinent due to a lack of well-dated sequential poles from the various cratonic nuclei. This paper examines the available data and shows that Laurentia could not have been a part of a supercontinent at 1.77 Ga, but it may have formed the core of a pre-Rodinia continent at 1.5 Ga. The available data do not preclude the existence of a Paleo-Mesoproterozoic supercontinent, but they do suggest that it must be younger than 1.77 Ga.
Key words: Paleoproterozoic, Mesoproterozoic, paleomagnetism, Columbia, supercontinent.
Introduction The concept of a Paleo-Mesoproterozoicsupercontinent was first proposed by Piper (1976) who evaluated the (then) extant paleomagnetic database and argued that a common APWP could be constructed for most continental regions. Over the past 25 years, the paleomagnetic database has expanded and the quality of the data has improved. The supercontinental configuration envisioned by Piper (1976, 2000) is no longer supported by the paleomagnetic data (Symons, 1991; Meert et al., 1994; Torsvik and Meert, 1995; Gala et al., 1998). Nevertheless, a late Mesoproterozoic to early Neoproterozoic supercontinent (-1.1-1.0 Ga), most commonly referred to as Rodinia (Fig. l),is strongly supported by geological connections. Rogers (1996) suggested that Rodinia was a product of a collision between Ur (Kalahari, India, Australia and coastal East Antarctica), Nena (Baltica, Mawson Continent of Antarctica, Laurentia and Siberia) and Atlantica (South America, West Africa, Central Africa) during Grenvillian-Kibarantime the geologic evidence for the proposed Rodinia configuration is strong; paleomagnetic tests of the proppsed configuration have produced ambiguous results (Weil et al., 1998; Walderhaug et al., 1999; Torsvik et al., 2001;
Fig. 1. The late Meso to Neoproterozoic supercontinent of Rodinia as envisioned by Dalziel (1997).
Meert and Powell, in press). Despite a lack of paleomagnetic confirmation, the geologic considerations
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Fig. 2. The hypothetical supercontinent “Columbia” that is composed of the ancient nuclei of Ur, Nena and Atlantica (Rogers, 1996). Rotation parameters used in this reconstruction (Laurentia-fixed, negative represents a clockwise rotation): Amazonia/Sao Francisco/Rio Plata cratons: 9.1, 110.2, +129.6; Congo/WestAfrica: 9.5,137.0, +159.23; Kaapvaal: 29.6,117.2, -178.26; Madagascar: 27.94, 115.28, +170.66; India: 53.4, 133.6, +161.75; Antarctica: 9.7, 112.8, +139.63; Australia: 25.71, 117.60 + 132.80; Siberia: 50.1, 182.2, -28.26; Baltica: 68.3, 127.7, -22.35. Special note: These euler rotations are non-unique and represent one possible configuration for Columbia.
suggest that if the Rodinia configuration proposed by Dalziel (1997) is approximately correct, then elements of Rodinia may have their origins in an earlier amalgam of continental landmasses nominally called Columbia (Fig. 2) that existed from - 1.8-1.5 Ga. Paleomagnetic studies remain the only quantitative method of testing the relationships between continental fragments in the Proterozoic. Nevertheless, paleomagnetic studies of Paleo-Mesoproterozoic age rocks must distinguish primary from secondary magnetizations in order to be useful. In addition, the age of the paleomagnetic poles must be known with reasonable certainty if they are to be used for reliable paleoreconstructions (Van der Voo and Meert, 1991; Buchan et al., 2000). This paper examines the extant paleomagnetic database from the continents thought to comprise the forerunner of Rodinia in order to test the proposed relationships between continental elements.
Paleomagnetic Approach There are at least two paleomagnetic approaches in evaluating the proposed “supercontinent” configuration of Columbia. The first approach, after evaluating the quality of the paleomagnetic data, is to rotate the poles to a common reference frame (based on the hypothetical configuration) and construct apparent polar wander paths (APWP) for known segments. If similar age poles fall in identical locations following rotation, then the reconstruction is supported by the paleomagnetic data, especially if segments of their APWPs can be fit. The second approach uses individual poles to reconstruct the continents to their correct paleolatitudinal position and evaluate the relationships between the continents based on their “closest approach since paleornagnetism cannot provide longitudinal control. Neither approach is unique as paleomagnetists are dealing with a sparsely populated Gondwana Research, V. 5, No. 1,2002
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data set and a polarity ambiguity. No euler rotation parameters for this proposed supercontinent have been developed to date, but the relationship between the elements of Columbia is easily evaluated (see Fig. 2). The position of the Mawson continent (East Antarctica) alongside western Laurentia in the Nena configuration of Rogers (1996) is based on the same geological relationships proposed for the younger Rodinia supercontinent (Dalziel, 1997). That position, however, is not without controversy as discussed by Karlstrom et al. (1999) who favor an even more southerly position against North America in the so-called “AUSWUS” configuration. Unfortunately, there are no paleomagnetic data from Antarctica from which we can test this hypothesis (see Table 1). For simplicity, we adopt the euler parameters of Dalziel (1997) along with modifications given in the figure legend (Fig. 2). A further controversy arises with respect to the position (and coherence) of the East Antarctic craton as discussed by Fitzsimons (2000). He notes the existence of three distinct late Meso to early Neoproterozoic collisional belts along the margin of East Antarctica and suggested that East Gondwana could not have existed prior to the last of these collisions at around 1000 Ma. The name Ur was proposed for an Archean assembly of the cratonic elements from southern Africa (Kaapvaal craton); western Dharwar, Singhbum and Bhandara cratons (India); the Yilgarn and Pilbara cratons (Australia) and strips of coastal Antarctica that lie adjacent to the previously mentioned cratons in the traditional Gondwana fit. Rogers (1996) arbitrarily included part of Madagascar because the extent of Archean crust was not known. Recent work of Tucker et al. (1999), Kroner et al. (2000) and de Wit et al. (2001) point to a significant amount of late Archean crust, but it is still younger than the cratons of Ur; thus Madagascar was not originally part of Ur because it did not yet exist. Previous analyses of the Mesoproterozoic paleomagnetic database attempted to test the relationships between individual continental blocks. For example, Buchan et al. (2000) compared the drift of Baltica to Laurentia in the Proterozoic using a similar quality filter on the paleomagnetic data. Their conclusion was that a connection between Laurentia and Baltica at 1.8 Ga was untestable using the extant database, but they suggested that individual poles a t 1.265 Ga were consistent with Baltica adjacent to eastern Greenland. Halls et al. (2000) tested relationships between the North China craton and Laurentia/Siberia at 1.77 Ga and tentatively concluded that these cratons remained in more or less the same configuration for the past 1.77 Ga with a few intervals of dispersal during that same time span. Gondwana Research, V. 5, No. 1,2002
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Ernst et al. (2000) presented limited new paleomagnetic data from the Kuonamka dykes of Siberia and concluded that the Rodinia (and Columbia) configurations were fully compatible with the limited dataset from Laurentia and Siberia. Additional reviews of late Paleoproterozoic and Mesoproterozoic paleomagnetic data were aimed at examining the timing of amalgamation of cratonic elements within a sing!e continent (Australia: Li, 2000; Idnurm, 2000; Laurentia: Gala et al., 1998).
Paleomagnetic Database Paleomagnetic data from the continents thought to comprise Columbia are given in table 1. Each pole was evaluated according to the criteria set forth in Van der Voo (1990). In order to be considered for inclusion into the analysis, each pole was required to have its age constrained to within 100 million years. Despite these liberal age constraints, the paleomagnetic database is rather limited for testing supercontinental configurations. Idnurm (2000) developed an APWP for a united Australia beginning at 1.75 Ga. The conclusion that the cratonic elements of Australia were united by 1.75 Ga is supported by the recent work of Li (2000). Li (2000) examined the paleomagnetic data from the northern and western Australia cratons and considered that suturing of the north and west Australian cratons occurred in the 1.79-1.76 Ga interval. The lack of data from the south Australian craton preclude definitive statements regarding its position relative to the north and west Australian cratons. There are no well-constrained APWPs for the other continents in my analysis but there are clusters of individual poles. Figure 3 shows the available paleomagnetic poles from Baltica (Fig. 3a), Laurentia (Fig. 3b) and Australia (Fig. 3c). Individual poles are listed in table 1. As previously noted, paleomagnetic data allow limited tests of cratonic coherence during any particular time interval. The most rigorous test would involve comparing segments of well-determined APWPs, but this cannot be accomplished with the present dataset because the only continent with a reasonable, but sparse, APWP is Australia (Idnurm, 2000). An alternative test involves rotating data from the other continents into the Australian reference frame using the assumed configuration for Columbia. However, this approach is based on the assumption of the particular configuration shown in figure 2. The problem with such an approach is two-fold. First, a poor fit of paleomagnetic data to the Australian path would not negate the possible existence of a supercontinent, it would require adjustments in the configuration. Secondly, a good fit of single poles on a path is no guarantee that the configuration is correct as the fit may be fortuitous.
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Table 1. Paleomagneticpoles. 4
5
6
7 Sum Reference
X
-
-
x x x x
x x x x x x x x x x x x x x x x x x x x - -
3
Idnurm and Giddings (1995) Idnurm (2000) Li (2000) Idnurm (2000) Idnurm (2000) Idnurm (2000) Idnurm (2000) Tanaka and Idnurm (1994) Chamalaun and Dempsey (1978)
1790(1) 1659(1)
-
-
x - - 2 x - - 4
McElhinny et al. (1978) Radhaluishna and Joseph (1996)
215.0 E 338.0 E
1790 (S) 1770(I)
x - - - x - x x x x x x -
69.1 N
200.2 E
1770 (S)
-
4.0
36.0 N
247.0 E
1769(1)
x x x x -
Kuonamka dykes
28.0
6.0 N
234.0 E
1503 (I)
x -
Wathaman batholith Macoun Lake granite Davin Lake granite Reynad Lake pluton Wekach Lake gabbro Hanson Lake pluton Tower Island pluton
3.5 8.1 4.7 4.8 8.0 5.3 3.3
9.3 N 43.9 N 54.0 N 39.7 N 0.8 N 36.2 N 76.9 N
292.6 E 287.7 E 266.8 E 253.2 E 255.0 E 265.5 E 257.6 E
1854(1) 1854(1) 1850 (I) 1851 (1) 1849(1) 1844(I) 1796(1)
x x x x x x x - x x x - -
Deschambault pegmatite Jan Lake gabbro St. Francois mountains Spokane Formation* Michikamau intrusion Harp Lake intrusive
67.5 N 48.1 N 13.2 S 15.5 S 1.5 S 1.6 N
276.0 E 269.6 E 219.0 E 225.5 E 218.0 E 206.3 E
1768 1767(1) 1476(1) 1460 (S) 1460(I) 1450(I)
x x x x - -
7.7 6.8 5.1 6.5 4.4
Haukuesi intrusives Luantari granodiorite Repruchy sill combine:d Tarendo gabbro Sipoo dykes (Qtz) Sipoo dykes (mafic) !inland Qtz dykes Nand dolerite dykes Dundret basic rocks Hallefornas dyke
3.4 7.0 12.5 4.4 13.3 40.1 13.2 9 3 9.3
49.0 N 67.0 N 40.5 N 44.9 N 26.4 N 31.6 N 30.2 N 28.0 N 22.0 N 27.0 N
225.0 E 198.0 E 218.8 E 229.6 E 180.4 E 183.6 E 175.4 E 188.0 E 203.0 E 167.0 E
1838 (I) 1777 (I) 1770 (I) 1757 (I) 1633 (I) 1633 (I) 1626 (I) 1577 (I) 1530 (I) 1518 (I)
Plong
Age (SI)
1 2
17.9 S 26.0 S 4.4 s 15.9 S 66.5 S 66.1 S 52.0 S 79.0 S 60.4 S
218.2 E 221.0 E 210.0 E 200.5 E 178.4 E 177.5 E 176.1 E 110.6 E 080.0 E
1758(I) 1725(I) 1710(S,I) 1709 (I) 1614(1) 1611(1) 1589 (I) 1525 (I) 1525 (I)
x x x x
6.3 9.4
16.0 N 18.8 N
160.5 E 054.8 E
Waterberg sediments Mashonland dolerites
8.4 5.0
16.0 S 8.0 N
Roraima Group
9.7
Taihang swarm
Pole
Name
A95
Plat
Australia AU-1 AU-1 AU-2 AU-3 AU-4 AU-5 AU-6 AU-7 AU-8
Woolagong Formation Peters Creek volcanics Elgee SS West Branch volcanics Amos Formation L. Balbirini U. Balbirini Mt Isa Inlier Gawler Range volcanics
8.5 5.5 6.4 11.3 4.0 4.6 5.4 8.4 5.2
Gwalior traps Tiruvannamalai dykes
x
3
x x x - x - x
-
x x -
-
-
X
-
x -
-
-
4 6 5 5 4 4 4
4
India IN-1 IN-2
x
x x x
-
Kaapvaal Craton AF-1 AF-2
2 6
Morgan and Briden (1981) Bates and Jones (1996)
-
4
Castilloand CostanzeAlvarez(1993)
x
-
5
Halls et al. (2000)
-
-
2
Ernst et al. (2000)
x -
-
4 3 4 4 4 4 3
Symons (1991) Symons et al. (1994) Symons et al. (1996) Symons (1995) Symons (1995) Gala et al. (1994) Symons et al. (1999)
South America SA-1
x
x
-
x x
North China NC-1
Siberia SI-1
x -
-
Laurentia LA- 1 LA- 2 LA-3 LA-4 LA-5 LA-6 LA-7
x x x x
x x x x
x x x x x - x - -
x -
Laurentia LA-8 LA-9 LA-10 LA- 11 LA- 12 LA- 13
x x x x x x x x x x
x - x x x x
-
x
-
x -
-
x -
-
-
4 3 x 6 x 4 x 4 x 4
Symons et al. (2000) Gala et al. (1995) Meert and Stuckey (2001) Vitorello andVanderVoo (1977) Murthy et al. (1968) Irving et al. (1977)
Baltica BA- 1 BA-2 BA-3 BA-4 BA-5 BA-6 BA-7 BA-8 BA-9 BA-10
Neuvonen et al. (1978) Neuvonen et al. (1978) Fedotova et al. (1999) Elming (1985) Mertanen and Pesonen (1995) Mertanen and Pesonen (1995) Neovonen (1986) Pesonen and Neuvonen (1981) Piper (1980) Piper (1980)
*S =stratigraphically inferred age, I=isotopically determined age.
Therefore, the only test of the proposed configuration currently available to paleomagnetism is to reconstruct the continents for a specific time interval and examine their relationships using the method of closest approach. The database allows examination of the relative positions of several of the cratons at 1.77 Ga and 1.5 Ga.
The reconstruction shown in figure 4a is one possible closest approach fit for the paleomagnetic data given in table 1. In order to minimize dispersed situations of the continents because of the polarity ambiguity, all continents are positioned in the same hemisphere. Given the caveats outlined at the beginning of this paper, the relative Gondwana Reskarch, V. 5, No. 1,2002
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Fig. 3. (a) Paleomagnetic data from Baltica listed in table 1. Lighter shading indicates a group of poles t h a t were possibly remagnetized between 1.455 and 1.633 Ga, (b) Paleomagnetic data from Laurentia listed in table 1. Darker shading indicates paleomagnetic poles from the Slave-Rae-Hearne provinces older than the Trans-Hudson Orogen and (c) Paleomagnetic poles from Australia listed in table 1along with a possible APWP for the 1.76 to 1.50 Ga interval (after Idnurm, 2000).
latitudinal positions of the Australian, Indian and Kaapvaal cratons are more or less consistent with the proposed Columbia fit although India requires approximately 180 degrees of rotation in order to match the Ur configuration (compare to figure 2). From a paleomagnetic perspective, the existence of Columbia at 1.77 Ga is negated by the polar position of Laurentia at that time. Gala et al. (1998) discuss the Trans-Hudson Orogen and its relationship to the assembly of Laurentia at 1.85 Gondwana Research, V. 5, No. 1,2002
Ga. Excellent paleomagnetic data suggest that the collision of the Slave-Rae-Hearne province with the Superior craton resulted from the closure of a n approximately 4000 kilometer north-south ocean. The assembled Laurentian landmass occupied a polar position following this collision. Figure 4a shows Laurentia in a south polar position, but a north pole location is also acceptable due to the inherent polarity ambiguity. There are more than sixty degrees of separation between
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Gondwana Research, K 5,No. 1,2002
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Laurentia and Australia and more than thirty degrees between Baltica and Laurentia. Halls et al. (2000) discussed the relationship of Siberia and the North China block (NCB) throughout the Proterozoic and suggested that they remained in close proximity Unfortunately,there are no paleomagnetic data from Siberia for this time period, but if the NCB remained in close proximity to Siberia, then there is considerable latitudinal separation between Laurentia and Siberia/North China. The preliminary conclusion is that the paleomagnetic data provide little support for the existence of a Columbiatype supercontinent at 1.77 Ga. The paleomagnetic database does not allow tests of any other detailed reconstructions during the 1.77-1.5 Ga interval. At 1.5 Ga, there are paleomagnetic data for Laurentia, Australia, Baltica and Siberia. Figure 4b shows a “closest approach” reconstruction that provides some support for both Columbia and the younger Rodinia supercontinent. There are several important observations with regard to this reconstruction. The first is that Australia is positioned a bit further south than in either the Columbia or Rodinia configurations. The position is compatible with the AUSWUS configuration of Karlstrom et al. (1999). The position of Siberia is almost a perfect match with both the Rodinia and Columbia configurations; however, the error on this particular paleomagnetic pole is 28 degrees. Baltica occupies a slightly more southerly position than in either the Rodinia or Columbia configuration. Its orientation on the equator can be flipped 180degrees because of the polarity ambiguity and this particular polarity choice for Baltica results in an inverted (compared to “traditional” models) position adjacent to Laurentia. The conclusion at 1.5 Ga is that the paleomagnetic data for these continents cannot be used to reject the possible supercontinental configurations of Rodinia or Columbia.
Conclusions The notion of a late Paleoproterozoic to Mesoproterozoic (1.8-1.5 Ga) supercontinent is not well supported by the available paleomagnetic data. The data show considerable latitudinal separation between a polar Laurentia and the low to equatorial positions of other continents at 1.77 Ga. Paleomagnetic data at 1.5 Ga give limited support for both the Columbia and Rodinia configurations. Therefore paleomagnetic constraints on the Columbia supercontinent are poor, but suggest that if the supercontinent did form, it must have been sometime after 1.77 Ga. Additional data are needed in order to provide rigorous constraints on Proterozoic and earlier continental configurations. Gondwaia Research, V: 5, NO^, 2002
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Acknowledgments The author acknowledges the support of the USNorwegian Fulbright program and a visiting professorship at the University Paul Sabatier in Toulouse, France. The author also wishes to thank John J.W. Rogers for his patience while I completed this project and an anonymous reviewer for comments on the manuscript.
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magnetization of the quartz porphyry dykes in southeast Finland, Geol. Surv. Finland, Bull., v. 58, pp. 195-201. Pesonen, L.J. and Neuvonen, K.J. (1981) Paleomagnetism of the Baltic shield: implications for Precambrian tectonics. In: Kroner, A. (Ed.), Developments in Precambrian Geology, Elsevier, Amsterdam, pp. 623-648. Piper, J.D.A. (1976) Palaeomagnetic evidence for a Proterozoic supercontinent.Phil. Trans. R. SOC.Lond., v. A280, pp. 469-490. Piper, J.D.A. (1980) A paleomagnetic study of Svecofennian basic rocks: Middle Proterozoic configuration of the Fennoscandian, Laurentian and Siberian shields. Phys. Earth Planet. Int., v. 23, pp. 165-187. Piper, J.D.A. (2000) The Neoproterozoic supercontinent: Rodinia or Palaeopangea?, Earth Planet. Sci. Lett., v. 176, pp. 131-146. Priem, H.N.A., Mulder, EG., Boelrijk, N.A.I.M., Hebeda, E.H., Verschure, R.H. and Verdurem, E.A.Th. (1968) Geochronological and paleomagnetic reconnaissance survey in parts of central and southern Sweden. Phys. Earth Planet. Int., v. 1, pp. 373-380. Radhakrishna, T. and Joseph, M. (1996) Proterozoic paleomagnetism of the mafic dyke swarms in the high-grade region of southern India. Precamb. Res., v. 76, pp. 31-46. Rogers, J.J.W. (1996) A history of the continents in the past three billion years. J. Geol., v. 104, pp. 91-107. Symons, D.T.A. (1991) Paleomagnetism of the Proterozoic Wathaman batholith and the suturing of the TransHudson orogen of Sasketchewan Canada, deduced from paleomagnetism. Can. J. Earth Sci., v. 28, pp. 19311938. Symons, D.T.A., Lohnes, C.A. and Lewchuck, M.T. (1994) Geotectonic constraints on the Macoun Lake granodiorite. Lynn Lake-La Ronge domain, Trans Hudson orogen. In: summary of Investigations 1994 Sask Geol. Surv., Sask Energ. Min. Misc. Rep., 94-4, pp. 123-131. Symons, D.T.A. (1995) Paleomagnetism of the 1851 MaReynard Lake pluton, Flin Flon domain, Trans Hudson orogen. In: summary of Investigations 1995 Sask Geol. Sum, Sask Energ. Min. Misc. Rep., 95-4, pp. 137-144. Symons, D.T.A., Lewchuck, M.T., Harris, M.J., Gala, M. and Palmer, H.C. (1996) Paleomagnetic studies in the Trans-Hudson Orogen. In: lithoprobe; Trans-Hudson Orogen transect; report of Sixth transect meeting. v. 55, pp. 69-72. Symons, D.T.A., Symons, T.B. and Lewchuck, M.T. (2000) Paleomagnetism of the Deschambault pegmatites: stillstand and hairpin at the end of the Paleoproterozoic Trans-Hudson orogeny. Canada. Phys. Chem. Earth, v. 25, pp. 479-487. Tanaka, H. and Idnurm, M. (1994) Paleomagnetism of Proterozoic mafic intrusions and host rocks of the Mt. Isa inlier, Australia revisited. Precamb. Res., v. 69, pp. 241-258. Torsvik, T.H. and Meert, J.G. (1995) Early Proterozoic paleomagnetic data from the Pechenga zone (northwest Russia) and their bearing on early Proterozoic paleogeography. Geophys. J. Int., v. 122, pp. 520-536. Torsvik, T.H., Carter, L., Ashwal, L.D., Bhushan, S.K., Pandit, M.K. and Jamtveit, B. (2001) Rodinia refined or obscured: paleomagnetism of the Malani igneous suite (NW India). Precamb. Res., v. 108, pp. 319-333. Tucker, R.D., Ashwal, L.D., Handke, M.J., Hamilton, M.A., LeGrange, M. and Rambeloson, R.A. (1999) U-Pb Gondwana Research, K 5, No. 1,2002
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geochronology and isotope geochemistry of the Archean and Proterozoic of rocks of north-central Madagascar. J. Geol., V. 107, pp. 135-153. Van der Voo, R. (1990) The reliability of paleomagnetic data. Tectonophys., v. 184, pp. 1-9. Van der Voo, R. and Meert, J.G. (1991) Late Proterozoic paleomagnetism and tectonic models: a critical appraisal. Precamb. Res., v. 53, pp. 149-163. Vitorello, I. and Van der Voo, R. (1977) Late Hadrynian and Helikian pole positions from the Spokane Formation,
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Montana. Can. J. Earth Sci., v. 14, pp, 67-73. Walderhaug, H.J., Torsvik, T.H., Eide, E.A., Sundvoll, B. and Bingen, B. (1999) Geochronology and paleomagnetism of the Hunnedalen dykes, SW Norway: implications for the Sveconorwegian apparent polar wander path. Earth Planet. Sci. Lett., v. 169, pp. 71-83. Weil, A.B., Van der Voo, R., MacNiocall, C. and Meert, J.G. (1998) The Proterozoic supercontinent Rodinia: paleomagnetically derived reconstructions for 1100-800 Ma. Earth Planet. Sci. Lett., v. 154, pp. 13-24.
Gondwana Research
Paleomagnetic Evidence for a Paleo-Mesoproterozoic Supercontinent Columbia Joseph G. Meert1t2 University of Florida, Department of Geological Sciences, 241 Williamson Hall, Gainesville, FL 32611, U S A Norwegian Geological Survey, Geodynamics Division, Leiv Eirikssons vei 39, 7491 Trondheim, Norway (Munuscript received May 1, 2002; accepted July 2,2002)
Abstract
...
Pre-Pangea supercontinents have been proposed for Neoproterozoic and earlier times. Most of the configurations are based on analyses of geologic and structural evidence, but the only quantitative method for testing the proposed configurations is paleomagnetism. Unfortunately, the current paleomagnetic database is of limited use in evaluating the notion of a Paleo-Mesoproterozoic supercontinent due to a lack of well-dated sequential poles from the various cratonic nuclei. This paper examines the available data and shows that Laurentia could not have been a part of a supercontinent at 1.77 Ga, but it may have formed the core of a pre-Rodinia continent at 1.5 Ga. The available data do not preclude the existence of a Paleo-Mesoproterozoic supercontinent, but they do suggest that it must be younger than 1.77 Ga.
Key words: Paleoproterozoic, Mesoproterozoic, paleomagnetism, Columbia, supercontinent.
Introduction The concept of a Paleo-Mesoproterozoicsupercontinent was first proposed by Piper (1976) who evaluated the (then) extant paleomagnetic database and argued that a common APWP could be constructed for most continental regions. Over the past 25 years, the paleomagnetic database has expanded and the quality of the data has improved. The supercontinental configuration envisioned by Piper (1976, 2000) is no longer supported by the paleomagnetic data (Symons, 1991; Meert et al., 1994; Torsvik and Meert, 1995; Gala et al., 1998). Nevertheless, a late Mesoproterozoic to early Neoproterozoic supercontinent (-1.1-1.0 Ga), most commonly referred to as Rodinia (Fig. l),is strongly supported by geological connections. Rogers (1996) suggested that Rodinia was a product of a collision between Ur (Kalahari, India, Australia and coastal East Antarctica), Nena (Baltica, Mawson Continent of Antarctica, Laurentia and Siberia) and Atlantica (South America, West Africa, Central Africa) during Grenvillian-Kibarantime the geologic evidence for the proposed Rodinia configuration is strong; paleomagnetic tests of the proppsed configuration have produced ambiguous results (Weil et al., 1998; Walderhaug et al., 1999; Torsvik et al., 2001;
Fig. 1. The late Meso to Neoproterozoic supercontinent of Rodinia as envisioned by Dalziel (1997).
Meert and Powell, in press). Despite a lack of paleomagnetic confirmation, the geologic considerations
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Fig. 2. The hypothetical supercontinent “Columbia” that is composed of the ancient nuclei of Ur, Nena and Atlantica (Rogers, 1996). Rotation parameters used in this reconstruction (Laurentia-fixed, negative represents a clockwise rotation): Amazonia/Sao Francisco/Rio Plata cratons: 9.1, 110.2, +129.6; Congo/WestAfrica: 9.5,137.0, +159.23; Kaapvaal: 29.6,117.2, -178.26; Madagascar: 27.94, 115.28, +170.66; India: 53.4, 133.6, +161.75; Antarctica: 9.7, 112.8, +139.63; Australia: 25.71, 117.60 + 132.80; Siberia: 50.1, 182.2, -28.26; Baltica: 68.3, 127.7, -22.35. Special note: These euler rotations are non-unique and represent one possible configuration for Columbia.
suggest that if the Rodinia configuration proposed by Dalziel (1997) is approximately correct, then elements of Rodinia may have their origins in an earlier amalgam of continental landmasses nominally called Columbia (Fig. 2) that existed from - 1.8-1.5 Ga. Paleomagnetic studies remain the only quantitative method of testing the relationships between continental fragments in the Proterozoic. Nevertheless, paleomagnetic studies of Paleo-Mesoproterozoic age rocks must distinguish primary from secondary magnetizations in order to be useful. In addition, the age of the paleomagnetic poles must be known with reasonable certainty if they are to be used for reliable paleoreconstructions (Van der Voo and Meert, 1991; Buchan et al., 2000). This paper examines the extant paleomagnetic database from the continents thought to comprise the forerunner of Rodinia in order to test the proposed relationships between continental elements.
Paleomagnetic Approach There are at least two paleomagnetic approaches in evaluating the proposed “supercontinent” configuration of Columbia. The first approach, after evaluating the quality of the paleomagnetic data, is to rotate the poles to a common reference frame (based on the hypothetical configuration) and construct apparent polar wander paths (APWP) for known segments. If similar age poles fall in identical locations following rotation, then the reconstruction is supported by the paleomagnetic data, especially if segments of their APWPs can be fit. The second approach uses individual poles to reconstruct the continents to their correct paleolatitudinal position and evaluate the relationships between the continents based on their “closest approach since paleornagnetism cannot provide longitudinal control. Neither approach is unique as paleomagnetists are dealing with a sparsely populated Gondwana Research, V. 5, No. 1,2002
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data set and a polarity ambiguity. No euler rotation parameters for this proposed supercontinent have been developed to date, but the relationship between the elements of Columbia is easily evaluated (see Fig. 2). The position of the Mawson continent (East Antarctica) alongside western Laurentia in the Nena configuration of Rogers (1996) is based on the same geological relationships proposed for the younger Rodinia supercontinent (Dalziel, 1997). That position, however, is not without controversy as discussed by Karlstrom et al. (1999) who favor an even more southerly position against North America in the so-called “AUSWUS” configuration. Unfortunately, there are no paleomagnetic data from Antarctica from which we can test this hypothesis (see Table 1). For simplicity, we adopt the euler parameters of Dalziel (1997) along with modifications given in the figure legend (Fig. 2). A further controversy arises with respect to the position (and coherence) of the East Antarctic craton as discussed by Fitzsimons (2000). He notes the existence of three distinct late Meso to early Neoproterozoic collisional belts along the margin of East Antarctica and suggested that East Gondwana could not have existed prior to the last of these collisions at around 1000 Ma. The name Ur was proposed for an Archean assembly of the cratonic elements from southern Africa (Kaapvaal craton); western Dharwar, Singhbum and Bhandara cratons (India); the Yilgarn and Pilbara cratons (Australia) and strips of coastal Antarctica that lie adjacent to the previously mentioned cratons in the traditional Gondwana fit. Rogers (1996) arbitrarily included part of Madagascar because the extent of Archean crust was not known. Recent work of Tucker et al. (1999), Kroner et al. (2000) and de Wit et al. (2001) point to a significant amount of late Archean crust, but it is still younger than the cratons of Ur; thus Madagascar was not originally part of Ur because it did not yet exist. Previous analyses of the Mesoproterozoic paleomagnetic database attempted to test the relationships between individual continental blocks. For example, Buchan et al. (2000) compared the drift of Baltica to Laurentia in the Proterozoic using a similar quality filter on the paleomagnetic data. Their conclusion was that a connection between Laurentia and Baltica at 1.8 Ga was untestable using the extant database, but they suggested that individual poles a t 1.265 Ga were consistent with Baltica adjacent to eastern Greenland. Halls et al. (2000) tested relationships between the North China craton and Laurentia/Siberia at 1.77 Ga and tentatively concluded that these cratons remained in more or less the same configuration for the past 1.77 Ga with a few intervals of dispersal during that same time span. Gondwana Research, V. 5, No. 1,2002
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Ernst et al. (2000) presented limited new paleomagnetic data from the Kuonamka dykes of Siberia and concluded that the Rodinia (and Columbia) configurations were fully compatible with the limited dataset from Laurentia and Siberia. Additional reviews of late Paleoproterozoic and Mesoproterozoic paleomagnetic data were aimed at examining the timing of amalgamation of cratonic elements within a sing!e continent (Australia: Li, 2000; Idnurm, 2000; Laurentia: Gala et al., 1998).
Paleomagnetic Database Paleomagnetic data from the continents thought to comprise Columbia are given in table 1. Each pole was evaluated according to the criteria set forth in Van der Voo (1990). In order to be considered for inclusion into the analysis, each pole was required to have its age constrained to within 100 million years. Despite these liberal age constraints, the paleomagnetic database is rather limited for testing supercontinental configurations. Idnurm (2000) developed an APWP for a united Australia beginning at 1.75 Ga. The conclusion that the cratonic elements of Australia were united by 1.75 Ga is supported by the recent work of Li (2000). Li (2000) examined the paleomagnetic data from the northern and western Australia cratons and considered that suturing of the north and west Australian cratons occurred in the 1.79-1.76 Ga interval. The lack of data from the south Australian craton preclude definitive statements regarding its position relative to the north and west Australian cratons. There are no well-constrained APWPs for the other continents in my analysis but there are clusters of individual poles. Figure 3 shows the available paleomagnetic poles from Baltica (Fig. 3a), Laurentia (Fig. 3b) and Australia (Fig. 3c). Individual poles are listed in table 1. As previously noted, paleomagnetic data allow limited tests of cratonic coherence during any particular time interval. The most rigorous test would involve comparing segments of well-determined APWPs, but this cannot be accomplished with the present dataset because the only continent with a reasonable, but sparse, APWP is Australia (Idnurm, 2000). An alternative test involves rotating data from the other continents into the Australian reference frame using the assumed configuration for Columbia. However, this approach is based on the assumption of the particular configuration shown in figure 2. The problem with such an approach is two-fold. First, a poor fit of paleomagnetic data to the Australian path would not negate the possible existence of a supercontinent, it would require adjustments in the configuration. Secondly, a good fit of single poles on a path is no guarantee that the configuration is correct as the fit may be fortuitous.
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Table 1. Paleomagneticpoles. 4
5
6
7 Sum Reference
X
-
-
x x x x
x x x x x x x x x x x x x x x x x x x x - -
3
Idnurm and Giddings (1995) Idnurm (2000) Li (2000) Idnurm (2000) Idnurm (2000) Idnurm (2000) Idnurm (2000) Tanaka and Idnurm (1994) Chamalaun and Dempsey (1978)
1790(1) 1659(1)
-
-
x - - 2 x - - 4
McElhinny et al. (1978) Radhaluishna and Joseph (1996)
215.0 E 338.0 E
1790 (S) 1770(I)
x - - - x - x x x x x x -
69.1 N
200.2 E
1770 (S)
-
4.0
36.0 N
247.0 E
1769(1)
x x x x -
Kuonamka dykes
28.0
6.0 N
234.0 E
1503 (I)
x -
Wathaman batholith Macoun Lake granite Davin Lake granite Reynad Lake pluton Wekach Lake gabbro Hanson Lake pluton Tower Island pluton
3.5 8.1 4.7 4.8 8.0 5.3 3.3
9.3 N 43.9 N 54.0 N 39.7 N 0.8 N 36.2 N 76.9 N
292.6 E 287.7 E 266.8 E 253.2 E 255.0 E 265.5 E 257.6 E
1854(1) 1854(1) 1850 (I) 1851 (1) 1849(1) 1844(I) 1796(1)
x x x x x x x - x x x - -
Deschambault pegmatite Jan Lake gabbro St. Francois mountains Spokane Formation* Michikamau intrusion Harp Lake intrusive
67.5 N 48.1 N 13.2 S 15.5 S 1.5 S 1.6 N
276.0 E 269.6 E 219.0 E 225.5 E 218.0 E 206.3 E
1768 1767(1) 1476(1) 1460 (S) 1460(I) 1450(I)
x x x x - -
7.7 6.8 5.1 6.5 4.4
Haukuesi intrusives Luantari granodiorite Repruchy sill combine:d Tarendo gabbro Sipoo dykes (Qtz) Sipoo dykes (mafic) !inland Qtz dykes Nand dolerite dykes Dundret basic rocks Hallefornas dyke
3.4 7.0 12.5 4.4 13.3 40.1 13.2 9 3 9.3
49.0 N 67.0 N 40.5 N 44.9 N 26.4 N 31.6 N 30.2 N 28.0 N 22.0 N 27.0 N
225.0 E 198.0 E 218.8 E 229.6 E 180.4 E 183.6 E 175.4 E 188.0 E 203.0 E 167.0 E
1838 (I) 1777 (I) 1770 (I) 1757 (I) 1633 (I) 1633 (I) 1626 (I) 1577 (I) 1530 (I) 1518 (I)
Plong
Age (SI)
1 2
17.9 S 26.0 S 4.4 s 15.9 S 66.5 S 66.1 S 52.0 S 79.0 S 60.4 S
218.2 E 221.0 E 210.0 E 200.5 E 178.4 E 177.5 E 176.1 E 110.6 E 080.0 E
1758(I) 1725(I) 1710(S,I) 1709 (I) 1614(1) 1611(1) 1589 (I) 1525 (I) 1525 (I)
x x x x
6.3 9.4
16.0 N 18.8 N
160.5 E 054.8 E
Waterberg sediments Mashonland dolerites
8.4 5.0
16.0 S 8.0 N
Roraima Group
9.7
Taihang swarm
Pole
Name
A95
Plat
Australia AU-1 AU-1 AU-2 AU-3 AU-4 AU-5 AU-6 AU-7 AU-8
Woolagong Formation Peters Creek volcanics Elgee SS West Branch volcanics Amos Formation L. Balbirini U. Balbirini Mt Isa Inlier Gawler Range volcanics
8.5 5.5 6.4 11.3 4.0 4.6 5.4 8.4 5.2
Gwalior traps Tiruvannamalai dykes
x
3
x x x - x - x
-
x x -
-
-
X
-
x -
-
-
4 6 5 5 4 4 4
4
India IN-1 IN-2
x
x x x
-
Kaapvaal Craton AF-1 AF-2
2 6
Morgan and Briden (1981) Bates and Jones (1996)
-
4
Castilloand CostanzeAlvarez(1993)
x
-
5
Halls et al. (2000)
-
-
2
Ernst et al. (2000)
x -
-
4 3 4 4 4 4 3
Symons (1991) Symons et al. (1994) Symons et al. (1996) Symons (1995) Symons (1995) Gala et al. (1994) Symons et al. (1999)
South America SA-1
x
x
-
x x
North China NC-1
Siberia SI-1
x -
-
Laurentia LA- 1 LA- 2 LA-3 LA-4 LA-5 LA-6 LA-7
x x x x
x x x x
x x x x x - x - -
x -
Laurentia LA-8 LA-9 LA-10 LA- 11 LA- 12 LA- 13
x x x x x x x x x x
x - x x x x
-
x
-
x -
-
x -
-
-
4 3 x 6 x 4 x 4 x 4
Symons et al. (2000) Gala et al. (1995) Meert and Stuckey (2001) Vitorello andVanderVoo (1977) Murthy et al. (1968) Irving et al. (1977)
Baltica BA- 1 BA-2 BA-3 BA-4 BA-5 BA-6 BA-7 BA-8 BA-9 BA-10
Neuvonen et al. (1978) Neuvonen et al. (1978) Fedotova et al. (1999) Elming (1985) Mertanen and Pesonen (1995) Mertanen and Pesonen (1995) Neovonen (1986) Pesonen and Neuvonen (1981) Piper (1980) Piper (1980)
*S =stratigraphically inferred age, I=isotopically determined age.
Therefore, the only test of the proposed configuration currently available to paleomagnetism is to reconstruct the continents for a specific time interval and examine their relationships using the method of closest approach. The database allows examination of the relative positions of several of the cratons at 1.77 Ga and 1.5 Ga.
The reconstruction shown in figure 4a is one possible closest approach fit for the paleomagnetic data given in table 1. In order to minimize dispersed situations of the continents because of the polarity ambiguity, all continents are positioned in the same hemisphere. Given the caveats outlined at the beginning of this paper, the relative Gondwana Reskarch, V. 5, No. 1,2002
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211
Fig. 3. (a) Paleomagnetic data from Baltica listed in table 1. Lighter shading indicates a group of poles t h a t were possibly remagnetized between 1.455 and 1.633 Ga, (b) Paleomagnetic data from Laurentia listed in table 1. Darker shading indicates paleomagnetic poles from the Slave-Rae-Hearne provinces older than the Trans-Hudson Orogen and (c) Paleomagnetic poles from Australia listed in table 1along with a possible APWP for the 1.76 to 1.50 Ga interval (after Idnurm, 2000).
latitudinal positions of the Australian, Indian and Kaapvaal cratons are more or less consistent with the proposed Columbia fit although India requires approximately 180 degrees of rotation in order to match the Ur configuration (compare to figure 2). From a paleomagnetic perspective, the existence of Columbia at 1.77 Ga is negated by the polar position of Laurentia at that time. Gala et al. (1998) discuss the Trans-Hudson Orogen and its relationship to the assembly of Laurentia at 1.85 Gondwana Research, V. 5, No. 1,2002
Ga. Excellent paleomagnetic data suggest that the collision of the Slave-Rae-Hearne province with the Superior craton resulted from the closure of a n approximately 4000 kilometer north-south ocean. The assembled Laurentian landmass occupied a polar position following this collision. Figure 4a shows Laurentia in a south polar position, but a north pole location is also acceptable due to the inherent polarity ambiguity. There are more than sixty degrees of separation between
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EVIDENCE FOR PAJEO-MESOPROTEROZOIC SUPERCONTINENT
Laurentia and Australia and more than thirty degrees between Baltica and Laurentia. Halls et al. (2000) discussed the relationship of Siberia and the North China block (NCB) throughout the Proterozoic and suggested that they remained in close proximity Unfortunately,there are no paleomagnetic data from Siberia for this time period, but if the NCB remained in close proximity to Siberia, then there is considerable latitudinal separation between Laurentia and Siberia/North China. The preliminary conclusion is that the paleomagnetic data provide little support for the existence of a Columbiatype supercontinent at 1.77 Ga. The paleomagnetic database does not allow tests of any other detailed reconstructions during the 1.77-1.5 Ga interval. At 1.5 Ga, there are paleomagnetic data for Laurentia, Australia, Baltica and Siberia. Figure 4b shows a “closest approach” reconstruction that provides some support for both Columbia and the younger Rodinia supercontinent. There are several important observations with regard to this reconstruction. The first is that Australia is positioned a bit further south than in either the Columbia or Rodinia configurations. The position is compatible with the AUSWUS configuration of Karlstrom et al. (1999). The position of Siberia is almost a perfect match with both the Rodinia and Columbia configurations; however, the error on this particular paleomagnetic pole is 28 degrees. Baltica occupies a slightly more southerly position than in either the Rodinia or Columbia configuration. Its orientation on the equator can be flipped 180degrees because of the polarity ambiguity and this particular polarity choice for Baltica results in an inverted (compared to “traditional” models) position adjacent to Laurentia. The conclusion at 1.5 Ga is that the paleomagnetic data for these continents cannot be used to reject the possible supercontinental configurations of Rodinia or Columbia.
Conclusions The notion of a late Paleoproterozoic to Mesoproterozoic (1.8-1.5 Ga) supercontinent is not well supported by the available paleomagnetic data. The data show considerable latitudinal separation between a polar Laurentia and the low to equatorial positions of other continents at 1.77 Ga. Paleomagnetic data at 1.5 Ga give limited support for both the Columbia and Rodinia configurations. Therefore paleomagnetic constraints on the Columbia supercontinent are poor, but suggest that if the supercontinent did form, it must have been sometime after 1.77 Ga. Additional data are needed in order to provide rigorous constraints on Proterozoic and earlier continental configurations. Gondwaia Research, V: 5, NO^, 2002
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Acknowledgments The author acknowledges the support of the USNorwegian Fulbright program and a visiting professorship at the University Paul Sabatier in Toulouse, France. The author also wishes to thank John J.W. Rogers for his patience while I completed this project and an anonymous reviewer for comments on the manuscript.
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