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Mesoproterozoic Supercontinent Nuna

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Mesoproterozoic Supercontinent Nuna Assembly and breakup of the core of Paleoproterozoic– Mesoproterozoic supercontinent Nuna David A.D. Evans* and Ross N. Mitchell Department of Geology & Geophysics, Yale University, 210 Whitney Avenue, New Haven, Connecticut 06520-8109, USA ABSTRACT from Evans and Pisarevsky (2008), but notably Idealized conceptual models of supercontinent cyclicity must be tested against the geologic including the combined Zig-Zag Dal–Midsom- record using pre-Pangean reconstructions. We integrate tectonostratigraphic records and mersø–Victoria Fjord results from Greenland paleomagnetic data from Siberia, Laurentia, and Baltica to produce a quantitative recon- (Table DR1) that imply a Laurentian apparent struction of the core of the Nuna supercontinent at 1.9–1.3 Ga. In our model, the present polar wander (APW) loop at 1.38 Ga (Fig. 1). southern and eastern margins of Siberia juxtapose directly adjacent to, respectively, the arc- The older Siberian poles superimpose, upon tic margin of Laurentia and the Uralian margin of Baltica. Consistent tectonostratigraphic the same rotation, atop the most central poles records of the three cratons collectively indicate the history of Nuna’s assembly and breakup. within a swath of similarly aged results from According to this reconstruction, the late Mesoproterozoic transition from Nuna to Rodinia the Slave craton (Mitchell et al., 2010) and sup- appears to have been much less dramatic than the subsequent late Neoproterozoic transition port a direct, long-lived connection between from Rodinia to Gondwana. those blocks. Also shown in Figure 1 are Bal- tica in the 1.8–1.2 Ga NENA (northern Europe INTRODUCTION nents to an absolute paleogeographic reference and North America) confi guration (Gower Various styles of supercontinental transitions frame. Broad-scale concordance of paleomag- et al., 1990; Buchan et al., 2000; Evans and are conjectured (Murphy and Nance, 2005) netic latitude estimates with paleoclimatic Pisarevsky, 2008), and more speculative juxta- but not known with certainty due to a lack of indicators such as evaporite basins for the past positions such as proto-SWEAT (southwestern precise knowledge of pre-Pangean continental two billion years (Evans, 2006) implies that a United States and East Antarctica) of Australian confi gurations. Global peaks in isotopic ages of paleomagnetic reconstruction of Nuna should cratons against western Laurentia (Betts et al., igneous rocks appear to indicate the existence be tractable. Quantitative tests of hypothesized 2008; Payne et al., 2009), north China adjacent of at least two Precambrian supercontinents: Rodinia reconstructions have been made pos- to Siberia (Wu et al., 2005), and SAMBA (South Rodinia, which formed ca. 1.0 Ga, and Nuna, sible due to a well-represented paleomagnetic America–Baltica) linking the basement terrains which amalgamated ca. 1.9–1.8 Ga (Hawkes- data set for Laurentia near its center (e.g., Li et of Baltica, Amazon, and West Africa (Johans- worth et al., 2009). The existence of an earlier al., 2008), but in contrast, paleomagnetic data son, 2009; see also Bispo-Santos et al., 2008). supercontinent, Kenorland, is questionable, as from Siberia for the Nuna time interval have Additional Mesoproterozoic data from Sibe- reviewed by Bleeker (2003), and Reddy and been entirely lacking. Recently published, high- ria, namely from the Kuonamka dikes in the Evans (2009). The confi guration of Rodinia quality data from Siberia (Wingate et al., 2009; Anabar block (Ernst et al., 2000), although remains debatable after nearly two decades of Didenko et al., 2009), however, provide a new widely used in previous paleomagnetic synthe- intense investigation (Hoffman, 1991; Dalziel, starting point for reconstructing cratons around ses (e.g., Meert, 2002; Pesonen et al., 2003), are 1997; Pisarevsky et al., 2003; Meert and Tors- the core of Nuna. problematic upon close inspection. The dated vik, 2003; Li et al., 2008; Evans, 2009); none- Kuonamka dike (ca. 1.50 Ga) bears a paleo- theless, initial speculations on the paleogeogra- NUNA RECONSTRUCTION magnetic remanence direction that is distinct phy of Nuna are beginning to take form (e.g., Quality-fi ltered paleomagnetic poles from from others correlated into the same swarm by Zhao et al., 2002). Siberia, along with coeval results from Lau- azimuthal trend. The large discrepancy between How can we begin reconstructing a vanished rentia and Baltica, are listed in Table DR1 of that lone direction and the more reliable pole supercontinent? In the frontispiece to his classic the GSA Data Repository.1 For ages older than from the nearly coeval (1.47 Ga) Olenëk intru- book, Du Toit (1937) noted that “Africa forms 1.8 Ga, we only compare paleomagnetic data sions (Wingate et al., 2009) suggests that addi- the key” of Pangea due to its central position from the closest reconstructed cratonic neigh- tional study of the Kuonamka dikes, and related surrounded by rifted passive margins devel- bors, for example Siberia and Slave, rather than intrusions, is warranted. The next younger Sibe- oped during breakup. Similarly, recognition of distant and likely unconnected cratons, such as rian paleomagnetic poles form an APW swath Neoproterozoic rifted margins around Lauren- Siberia and Superior (cf. Didenko et al., 2009). that diverges from the Laurentian APW path tia has led to the widespread consensus that it The highest-quality results from Siberia are ca. 1.1 Ga (Fig. 1A; for further illustration, see was near the center of Pangea’s predecessor from the 1.88–1.86 Ga Akitkan volcanic and the Data Repository), implying separation of Rodinia (Bond et al., 1984; McMenamin and sedimentary rocks (Didenko et al., 2009) and Siberia prior to that time. Although reliable pre– McMenamin, 1990). Nuna’s formation at 1.9– the 1.47 Ga Olenëk intrusions (Wingate et al., 1.88 Ga poles from Siberia are not available, 1.8 Ga should have been followed by breakup 2009), both representing the Anabar-Angara data from Slave craton and Fennoscandia for in the 1.7–1.3 Ga interval (Hoffman, 1989). The subregion of Siberia. The younger poles and vir- 2.1–1.9 Ga are not compatible with our Nuna Siberian craton is nearly surrounded by Paleo- tual geomagnetic poles are rotated to superim- reconstruction (Fig. 1A; for further illustration, proterozoic–Mesoproterozoic passive margins pose atop coeval Laurentian data, largely taken see the Data Repository), implying that the core (Pisarevsky and Natapov, 2003), and thus likely of the supercontinent assembled ca. 1.9 Ga. forms the key of the Nuna landmass. 1GSA Data Repository item 2011145, paleomag- Such a result is consistent with the independent Paleomagnetism remains the only quantita- netic poles and discussion of Euler rotations, is avail- evidence from dated orogenic events in Siberia, able online at www.geosociety.org/pubs/ft2011.htm, tive method to reconstruct pre-Pangean conti- or on request from [email protected] or Docu- northern Canada, and Fennoscandia (Lahtinen ments Secretary, GSA, P.O. Box 9140, Boulder, CO et al., 2008; Pisarevsky et al., 2008; Corrigan et *E-mail: [email protected]. 80301, USA. al., 2009; St-Onge et al., 2009). © 2011 Geological Society of America. For permission to copy, contact Copyright Permissions, GSA, or [email protected]. GEOLOGY,Geology, May May 2011; 2011 v. 39; no. 5; p. 443–446; doi:10.1130/G31654.1; 1 fi gure; Data Repository item 2011145. 443 Baltica Our paleomagnetic analysis is the fi rst to Siberia extend putative links between Siberia and present northern Laurentia, back to the more N ° 0 ancient connections between Siberia and only A Laurentia / 6 the Slave and Rae Provinces prior to Lauren- Slave tia’s large-scale assembly ca. 1.8 Ga (St-Onge et al., 2006). It allows a tight fi t of these terrains ~1100 N in a compact Nuna confi guration, not requiring ° 0 3 identifi cation of an additional craton to fi ll an ~1100 ~1100 ~1000 km gap as in previous reconstructions Kuon (Pisarevsky et al., 2008). It challenges the alternative Proterozoic placement of Siberia along the western margin of Laurentia (Sears 1267 ? and Price, 2003), as well as the hypothesis of 1380 1740 Ma (no data) PJot Chier W ~2000 Congo–São Francisco along the arctic Lauren- Mac AP na Cleav Nu r tian margin from 1.6 to 0.7 Ga (Evans, 2009). Zig to LadLad ua Shok Eq SvecSvec ASSEMBLY AND BREAKUP OF NUNA StSt 14701 0 1880–18601880–1860 4 uAkuAA The direct juxtaposition of Siberia and StFr lAk SetSet northern Laurentia shown in Figure 1 is almost Toch Kah ~2000 identical to that hypothesized on regional geo- Olen Doug logical grounds by Rainbird et al. (1998); in Pear that synthesis, the Slave craton was postulated E °S ° 30 E 0 ° to continue into Siberia as the Tungus block, 1 E 0 ° 2 E 3 0 ° and the Thelon orogen to continue as the Akit- 3 4 0 2 0 3 kan fold belt. Such correlations are permitted 270°E in our reconstruction, but it is also possible that 1270 Ma the sedimentary cover of the Canadian archi- Reconstructed with Mackenzie pole pelago conceals a 1.9 Ga suture between Slave and Tungus (Donskaya et al., 2009). The Aldan n shield is a collage of Archean blocks assembled B by 1.9 Ga (Rosen et al., 1994; Pisarevsky et al., N u n a Proto-Australia 2008), via orogenic events that by our recon- 30°N struction appear to continue into the Inglefi eld Pre-2.3 Ga 6 l mobile belt of the northern Baffi n Bay region a craton z yo- T t W a l 4 a i ts z (Nutman et al., 2008). Craton amalgamation a ming o W a n o p pma 2.3–1.8 Ga M a y v Tran a s-H T of similar age occurred in the proposed adja- ud H H Y s o e E ngara orogen n 1 L A a O S r la Su n N v cent areas of Baltica (Bogdanova et al., 2008; pe R e T - rior e ungus North no an a 1.8–1.1 Ga Pe ke e 3 A China Fig.
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