author's personal copy the great oxidation and a siderian snowball earth: mif-s based...

Author's personal copy

The Great Oxidation and a Siderian snowball Earth: MIF-S based correlation ofPaleoproterozoic glacial epochs

Paul F. Hoffman ⁎Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138, USASchool of Earth and Ocean Sciences, University of Victoria, Victoria, BC V8P 5C2, Canada

a b s t r a c ta r t i c l e i n f o

Article history:Accepted 27 April 2013Available online 7 May 2013

Keywords:OxygenAtmosphereGreat oxidationGlaciationSnowball EarthPaleoproterozoic

Existing correlation schemes between early Paleoproterozoic successions divorce the low-latitudeMakganyene glaciation in southern Africa from the Great Oxidation (GO), as recorded by the disap-pearance of mass-independent fractionation of S-isotopes (MIF-S) in sedimentary sulfide and sulfateminerals. They also suggest a younger age for the GO in southern Africa (~2.3 Ga) compared with NorthAmerica (~2.4 Ga), which is physically implausible. A new correlation scheme is proposed in which theMakganyene glaciation is temporally linked to the GO and to the second of three Huronian glaciations inNorth America, the one with postglacial cap-carbonate. In the new scheme, only three glacial epochs are neededglobally, all three are represented in southern Africa, and the second was a circa 2.40 Ga snowball Earthcoincident with the GO.

© 2013 Elsevier B.V. All rights reserved.

1. Introduction

No colleague at Harvard visited my office as often as Dick Holland.Sometimes he sought information, sometimes a sounding board forhis ideas. Like Charles Darwin, Dick was not reticent to use the phrase,“my theory”. He was the third of my colleagues to espouse an irrevers-ible and transformative rise in atmospheric oxygen at the start of theProterozoic Eon (Holland, 1962, 1984, 1994, 2006). The first (in orderof my acquaintance) was economic geologist and float-plane pilot StuRoscoe at the Geological Survey of Canada (Roscoe, 1969, 1973, 1981).The second was geologist and geobiologist Pres Cloud at the Universityof California — Santa Barbara (Cloud, 1968, 1972, 1973, 1988). Now allthree are gone, but their theory of a Great Oxidation (GO) appearsdestined to last as long as science itself.

Causal links between the GO and global refrigeration, through thedestruction of reduced greenhouse gases (CH4, H2S, H2 etc.), havebeen postulated (Pavlov et al., 2000; Catling and Claire, 2005; Koppet al., 2005; Kasting and Ono, 2006; Zahnle et al., 2006; Kirschvinkand Kopp, 2008). However, standard stratigraphic correlations (Fig. 1)

suggest that the most severe climatic disturbance, the low-latitudeMakganyene glaciation of southern Africa (Gevers and Beetz,1940; Visser, 1971; De Villiers and Visser, 1977; Evans et al., 1997;Kirschvink et al., 2000; Polteau et al., 2006), occurred 100–200 millionyears after the GO, defined here as the irreversible rise of atmo-spheric oxygen above 10−5 PAL (2 ppm) indicated by the disap-pearance of mass-independent fractionation (MIF) of S-isotopes(Δ33S ≥ 0.3‰ or ≤−0.3‰ VCDT, Vienna Canyon Diablo Troilite)in sedimentary sulfide and sulfate minerals (Farquhar et al., 2000;Pavlov and Kasting, 2002; Farquhar and Wing, 2003). Moreover,the GO itself (Fig. 1) appears to have occurred 50–100 million yearslater on the Kaapvaal craton of southern Africa (Bekker et al., 2001,2010; Hannah et al., 2004; Guo et al., 2009) than on the Superior cratonof North America (Papineau et al., 2007). This is physically implausiblegiven a well-mixed troposphere and rapid transfer of atmosphericsulfur into sediments in an anoxic surface environment in which thereservoir of mobile sulfur was small (Ono et al., 2003; Farquhar et al.,2013; Halevy, 2013).

Here, the stratigraphic, chronometric and isotopic constraints onearly Paleoproterozoic glacial epochs and atmospheric oxygenationin North America, southern Africa, Western Australia and ArcticEurope are briefly reviewed. Contested correlations between thetwo major Paleoproterozoic basins in southern Africa, the GriqualandWest and Eastern Transvaal basins, are highlighted. A new correlationscheme is suggested for southern Africa and the other cratons basedon two assumptions: that the GO (disappearance of MIF-S) was a sin-gular event and that it was connected in time with a severe glaciation.

Chemical Geology 362 (2013) 143–156

⁎ 1216 Montrose Ave., Victoria, BC V8T2K4, Canada.E-mail address: [email protected].

0009-2541/$ – see front matter © 2013 Elsevier B.V. All rights reserved.http://dx.doi.org/10.1016/j.chemgeo.2013.04.018

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In the new scheme, only three discrete glacial epochs (the minimum)are needed globally and the second one, ~2.40 Ga, was a snowballEarth (Kirschvink et al., 2000) associated with the GO. All three glaci-ations were Siderian (2.50–2.30 Ga) in age (Gradstein et al., 2012).The new scheme combines elements proposed earlier by Moore etal. (2001, 2012) and Williford et al. (2011).

2. North America

2.1. Huronian Supergroup, Superior craton

The Huronian Supergroup (Fig. 2) is a southward-thickening wedgeof northerly-derived clastic sedimentary rocks up to 13 km thick,

2.22 Ga1------

2.32 Ga3------

2.31 Ga2------ 2.31 Ga

2------

2.22 Ga4------

2.45 Ga5------

MooidraiHotazel

Makganyene ‘Boshoek’= Rietfontein)

Timeball Hill

Duitschland

Griqualand West(Postmasburg Group)

Eastern Transvaal(lower Pretoria Group)

Bar RiverGordon Lake

Lorrain

Gowganda

Serpent

Mississagi

McKim

MatinendaThessalon

Livingstone Ck

PecorsRamsay Lake

EspanolaBruce

Superior craton(Huronian Supergroup)

Elli

ott

Hou

ghQ

uirk

eC

obal

t

v v v v v v v v v v v v

v v v v v v

Ongeluk Hekpoort

v v v v v v

Fe-Mn formation

carbonate

volcanics

glacial diamictite

sandstone, conglomerate

siltstone, shale

hematite-rich horizon

MIF disappearance

SNOWBALL EARTH

LEGEND

Nipissing Diabase

SOUTHERN AFRICA NORTH AMERICA

Age(Ga)

2.25

2.30

2.35

2.40

2.45

drift

rift

Fig. 1. Correlation chart (time on y-axis) of early Paleoproterozoic glaciations on the Kaapvaal (Griqualand West and Eastern Transvaal basins) and Superior cratons, assumingsynchrony of the 2.22-Ga Hekpoort and Ongeluk volcanics, and parallel correlation of the Makganyene and ‘Boshoek’ (Rietfontein Member) diamictites (modified after Koppet al., 2005). In this standard correlation, the low-latitude Makganyene glaciation (Evans et al., 1997), purportedly a snowball Earth (Kirschvink et al., 2000; Kopp et al., 2005),must be younger than the Great Oxidation (GO)—defined here as the disappearance of mass-independent fractionation of sulfur isotopes (MIF-S) in sedimentary sulfate and sulfideminerals—and all three Huronian glaciations. Note the apparent asynchroneity of MIF-S-disappearance. The asynchrony would be greater if Huronian accumulation rate declinedover time (e.g. thermal subsidence), not held constant as assumed here. Geochronological data: 1Dorland (2004); 2Bekker et al. (2010); 3Hannah et al. (2004); 4Corfu and Andrews(1986), Noble and Lightfoot (1992); 5Krogh et al. (1984).

5.0

4.0

3.0

2.0

1.0

0.0

km

2.45 Ga

2.31 Ga

2.22 Ga

Elliott Lake

Group

Hough Lake

Group

Quirke Lake Group

Cobalt

Group

Bar River FmGordon Lake Fm

Lorrain Fm

Gowganda Fm

Matinenda FmMcKim Fm

Pecors FmMississagi Fm

Serpent FmEspanola Fm

Thessalon Fm

Ramsay Lake Fm

Livingstone Creek Fm

Bruce Fm

South 250 km North

quartzite, arkose

pebbly arkose

conglomerate

argillite, siltstone

argillite, greywacke

argillite

boulder diamictite

bimodal volcanics

Archean basement

limestone, marlstone

LEGEND

Paleosols

oxic

anoxic

no MIF

MIF

Δ33S

Flack LakeFault

Agnew LakeFault

Espanola LakeFault

Detrital FeS2, UO2

Fig. 2. Restoration (stratigraphic thickness on y-axis) of the early Paleoproterozoic Huronian Supergroup on the southern margin of the Superior craton in the southern CanadianShield (modified after Zolnai et al., 1984). As constrained by atmospheric redox proxy data (MIF-S, detrital minerals and paleosol geochemistry), the GO (Great Oxidation) couldonly have been associated with the second of three Huronian glaciations, represented by the Bruce Formation.

144 P.F. Hoffman / Chemical Geology 362 (2013) 143–156


preserved on the south-facingmargin of the Superior craton in an east–west trending belt of large scale, basement-involved folds of Penokean(~1.85 Ga) and, in the east, Grenvillian (~1.05 Ga) age (Roscoe, 1969;Card et al., 1972; Zolnai et al., 1984; Bennett et al., 1991). The foldingprovides tight stratigraphic control, while Quaternary glaciationbequeathed semicontinuous outcrops of unweathered bedrock, lessobscured by drift than by lakes. The depositional age of the HuronianSupergroup is bracketed by zircon U–Pb dates of 2.49–2.44 Ga (Kroghet al., 1984) from volcanic and comagmatic intrusive rocks associatedwith the basal clastics in the south, and concordant baddeleyite andrutile U–Pb dates of 2.22 Ga (Corfu and Andrews, 1986; Noble andLightfoot, 1992) from mafic dykes (Nipissing Diabase) that intrude theentire Huronian succession. The Huronian Supergroup is interpreted asa passive-margin prism >340 Myr older than the Penokean collisionalforedeep (Zolnai et al., 1984; Schulz and Cannon, 2007).

There is disagreement over when passive-margin subsidence began,the timing of the rift-to-drift transition. Bennett et al. (1991) place it atthe base of the Matinenda Formation (Fig. 2), after which fluvial sedi-ment transport was consistently southward directed, toward the basinaxis (Card et al., 1972; Fralick and Miall, 1989; Bennett et al., 1991).Active rift valleys (e.g. Mid-Ocean Rift, East African Rift, Rio GrandeRift, Rhine Graben) are flanked by broad uplifts that slope gently awayfrom the elevated rim of the valley, causing regional drainage to bedirected away from the axial valley, which is commonly floored bysalt. Nevertheless, some geologists view most of the Huronian as asynrift succession, placing the rift-to-drift transition at the base of theCobalt Group (Young and Nesbitt, 1985; Young et al., 2001). This isbased in part on the presence of high-angle reverse faults thatare inferred to be inverted, south-side-down, normal faults thatwere overstepped by the Cobalt Group, but which cut all older units(e.g. Flack Lake Fault in Fig. 2). Such amagmatic normal faults couldalternatively have resulted from lithospheric flexure, due to sedimentloading, during thermal (passive-margin) subsidence. They could alsobe far-field effects of active tectonics on other margins of the Superiorcraton, which was only 2250 km in diameter. The broader patternsof subsidence and sediment transport favor the earlier rift-to-drift tran-sition, coincident with the cessation of igneous activity ~2.44 Ga(Bennett et al., 1991). If thermal relaxation was the driving mechanismfor Huronian subsidence following a rift-to-drift transition ~2.44 Ga,then most if not all of the succession should be older than ~2.30 Ga.This is consistent with a preliminary in situ U–Pb zircon date of~2.31 Ga for a microtuff in the Gordon Lake Formation (upper CobaltGroup) near the top of the Huronian succession (Bekker et al., 2010).

The Huronian Supergroup (Fig. 2) comprises four, disconformity-bounded, depositional sequences—the Elliott Lake, Hough Lake,Quirke Lake and Cobalt groups—that progressively onlap the Archeanbasement from south to north (Zolnai et al., 1984). Each of the upperthree sequences begins with a glacial–periglacial unit, the RamsayLake, Bruce and Gowganda formations in order of decreasing age.The Gowganda Formation is the most extensive and the RamsayLake Formation the most restricted, reflecting the extent of the hostsequence, not the extent of glaciation. Coarse debris is exclusivelybasement-derived in all three glacigenic formations, alternativelybecause the ice sheets were not grounded within the sedimentarybasin, they were grounded but not erosive, or because the sedimentarybeds were unlithified at the time of glaciation.

The thickest and most variable glacigenic unit is the GowgandaFormation, which ranges from predominantly terrestrial with apostglacial marine transgression in the north, to exclusively glacial ma-rine in the south. It has been subject to many sedimentological studies(Coleman, 1907, 1908; Wilson, 1913; Lindsey, 1969, 1971; Miall, 1985;Young and Nesbitt, 1985; Mustard and Donaldson, 1987; Rainbrid andDonaldson, 1988; Harker and Giegengack, 1989; Hughes et al., 2003).Outliers of diamictite (Chibougamau Group) near Lake Mistassini,500 km to the northeast of the contiguous Huronian rocks, are probablecorrelatives (Roscoe, 1969). The Bruce Formation, the middle glacigenic

unit, is unique in having a well-developed postglacial cap-carbonate,the lower Espanola Formation (Young, 1973a; Bernstein and Young,1990; Bekker et al., 2005). In addition to being the only carbonate-bearing unit in theHuronian succession, the Espanola Formation is asso-ciatedwithwidespread clastic dykes and intrusive sedimentary breccias(Eisbacher, 1970; Young, 1972; Chandler, 1973). The oldest glacial–periglacial unit, the Ramsay Lake Formation, has complex internal faciesrelations (Fralick and Miall, 1989)—glacial processes both create anddestroy local topography and the resulting glacial deposits are thereforehideously complex in detail.

It has long been recognized that the Huronian Supergroup records amajor change in the O2 content of the ancient atmosphere. Detrital py-rite (FeS2) and uraninite (UO2) in alluvial conglomerate and sandstoneof the Matinenda Formation (Roscoe, 1969), and the geochemistryof paleosols developed on basalt and granite beneath the MatinendaFormation (Prasad and Roscoe, 1996; Murakami et al., 2001, 2011;Utsunomiya et al., 2003) point to an anoxic atmosphere ~2.45 Ga. Incontrast, Mn-enrichment in redbeds associated with the marine inun-dation following the Gowganda glaciation (Sekine et al., 2011b)and evaporative nodular anhydrite (CaSO4) in redbeds of the GordonLake Formation (Chandler, 1988) indicate strongly oxidizing conditionsof upper Huronian age. While Δ33S variability in authigenic sulfide andsulfate minerals from the Huronian is muted, compared to lateNeoarchean (2.7–2.5 Ga) values of −2.0 to +11‰ (Farquhar et al.,2010; Halevy et al., 2010; Kurzweil et al., 2013), values in the lowerHuronian (Elliott Lake and Hough Lake groups) range as high as+0.78‰ (McKim Formation) and +0.88‰ (Pecors Formation), whilethose in the upperHuronian (Espanola, Lorrain andGordon Lake forma-tions) are ≤+0.21‰ (Papineau et al., 2007). Within the limits of strati-graphic resolution (no data for the Mississagi Formation), thedisappearance of MIF-S correlates broadly with the Bruce glaciation,the only Huronian glaciation directly followed by extensive carbonatedeposition (Bekker et al., 2005).

More precise synchroneity between a rise in atmospheric oxygenand the Bruce glaciation comes from redox-sensitive trace metals.Sharp increases in Os, Re and Mo concentrations, coincident with aspike in radiogenic Os (187Os/188Os ≥ 1.0 compared to background≤0.2), occur in a thin (1.5 m) sandstone–siltstone unit lying conform-ably above diamictite of the Bruce Formation and conformably belowlimestone (cap carbonate) of the Espanola Formation (Sekine et al.,2011a). The radiogenic spike shows that the Os was derived from theweathering of continental rocks, requiring O2 ≥ 10−4 PAL to mobilizecrustal Os, and the return to less radiogenic values is thought to resultfrom increasing contribution of non-radiogenic Os (i.e. mantle or extra-terrestrial Os) from seawater, relative to radiogenic Os in runoff, asdeglaciation and concomitant sea-level rise progressed (Sekine et al.,2011a). These data indicate a rise in atmospheric O2 at the time ofBruce deglaciation, as proposed for the aftermath of a Paleoproterozoicsnowball Earth (Kirschvink et al., 2000; Kopp et al., 2005; Liang et al.,2006). They neither support nor deny a prior rise in O2 above 10−5

PAL at the onset of the Bruce glaciation.

2.2. Snowy Pass Supergroup, Wyoming craton

The Snowy Pass Supergroup (Blackwelder, 1926; Karlstrom et al.,1983) in the Medicine Bow Mountains of Wyoming mimics theHuronian Supergroup stratigraphy formation-by-formation (Young,1973b; Roscoe and Card, 1993; Bekker et al., 2003, 2005). There arethree glacial horizons, the second of which has a cap-carbonate. Thesecond diamictite and its cap-carbonate comprise the lower andmiddleVagner Formation (Deep Lake Group). Beneath the oldest diamictite(Campbell Lake Formation) are uraniferous quartz-pebble conglomer-ates; above the youngest diamictite (lower Headquarters Formation)are aluminous (diaspore- or kyanite-bearing) quartzites. The strati-graphic homology with the Huronian Supergroup is so striking thatmost geologists follow Roscoe and Card (1993) in assuming that the

145P.F. Hoffman / Chemical Geology 362 (2013) 143–156


Wyoming craton is a fragment of the Superior craton that separatedafter 2.23 Ga and was later lodged in its present position withinproto-Laurentia by ~1.77 Ga (e.g. Ernst and Bleeker, 2010).

2.3. Hurwitz Group, Hearne craton

Within an early Paleoproterozoic (2.45–2.11 Ga) cratonic basinwest of Hudson Bay, the Padlei Formation (Hurwitz Group) containsmassive and stratified diamictite, conglomerate and sandstone,rhythmite with dropstones, and possible glendonite pseudomorphs,suggesting a glacial marine origin (Aspler and Chiarenzelli, 1997).The basin rests on Neoarchean basement of the Hearne craton,which collided first with the Rae craton to the northwest, formingthe 1.92-Ga Snowbird geosuture (Berman et al., 2007; Martel et al.,2008), and then with the Superior craton to the southeast, formingthe 1.83-Ga Trans-Hudson orogen (St-Onge et al., 2006). The stratigra-phy of the Hurwitz Group does not parallel the Huronian or SnowyPass supergroups, and the Kaminak dykes of the Hearne craton, longcompared with the 2.45-Ga Matachewan dykes of the Superior craton(e.g. Ernst and Bleeker, 2010), are now known to be older (2.50 Ga)and petrochemically distinct (Sandeman et al., in press). The Hearnecraton, unlike the Wyoming craton, had no apparent affiliation withthe Superior craton in early Paleoproterozoic time. The age of the Padleiglaciation relative to the three Huronian glaciations is unknown.

3. Southern Africa

3.1. Transvaal Supergroup, Kaapvaal craton

On the Mesoarchean Kaapvaal craton of southern Africa, theTransvaal Supergroup (Fig. 3) forms an extensive sedimentaryand minor volcanic cover succession of late Neoarchean–earlyPaleoproterozoic age up to 15 km thick (Eriksson et al., 1993;Cheney and Winter, 1995; Tinker et al., 2002). The succession is pre-served in two large structural and depositional basins. The GriqualandWest basin is situated on the western margin of the Kaapvaal cratonand is bordered by the ~1.2 Ga Kheis orogenic belt (van Niekerk,2006; Knoll and Beukes, 2009). The Eastern Transvaal basin is anintracratonic basin divided by younger rocks (Reczko et al., 1995).The basins are separated by the northwest-plunging Vryburg arch,where Ventersdorp (2.71 Ga) volcanic cover is exposed and a 2.9-Gageosuture lurks in the underlying basement (Schmitz et al., 2004).Down the plunge of the arch, the Transvaal Supergroup ismostly buriedbeneath Cenozoic (Kalahari Group) cover of the Kanye basin in south-eastern Botswana (Moore et al., 2012). Correlation between theGriqualand West and Eastern Transvaal basins (Fig. 3) relies criticallyon subsurface information from this area. In the far east, theVentersdorp volcanics are absent and the Transvaal Supergroupdirectlyoverlies Paleo-Mesoarchean greenstone belts (e.g. Barberton) and asso-ciated granitoids. Excepting the western limit of the Transvaal

Bushveld Intrusion Steenkamps.Lakenvlei

Magaliesberg

DaspoortDwaalheuwel

HekpoortBoshoek

Timeball Hill

Penge

Malmani Subgroup

Black Reef

Duitschland

Pre

toria

Gro

upC

huni

espo

ort G

p

Tran

svaa

l Sup

ergr

oup

Hartley

LucknowGamahara

Ongeluk

Makganyene

Hotazel Mooidraai

KoegasSubgroup

Asbestos HillsSubgroup

Campbell-rand Sbgp

Schmidtsdrif

Olif

ants

hoek

Sup

ergr

oup

Postmasburg Group

Gha

ap G

roup

Tran

svaa

l Sup

ergr

oup

GRIQUALAND WEST EASTERN TRANSVAAL

VRYBURG ARCH

Hekpoort

Bushveld Complex

MD

20oE 30oE

30oS

Outcropping Transvaal Supergroup

A

B C

N

Griqualand West

Eastern Transvaal

500 km

SOUTH AFRICA

BOTSWANA

NAM.

AB

C

sandstone, conglomerate

siltstone or argillite

Fe-oxideformation

basinalcarbonate

platformal carbonate

glacigenicdiamictite

subaqueousmafic volcanics

terrestrialmafic volcanics

layered maficintrusive complex

unconformity

Δ33SMIF absent

MIF present

Paleosolsoxic

anoxic

100 km

1.0 km

Vryburg arch

KurumanGriquatown

Fe/Mn carbonates, oxides and silicates

Fig. 3. Restoration (stratigraphic thickness on y-axis) of the late Neoarchean–early Paleoproterozoic Transvaal and Olifantshoek supergroups in southern Africa (modified afterEvans et al., 2002), showing atmospheric redox proxy indications (see text). Two glacial horizons occur in the Eastern Transvaal but only one in Griqualand West (unless a localdiamictite in the basal Koegas Subgroup is glacigenic). Correlations between the two areas rely on subsurface information from the downward plunge of the Vryburg arch inBotswana (location B). In the ‘standard’ correlation (shown here), Hekpoort and Ongeluk volcanics are correlated, and the low-latitude Makganyene glaciation is equated with theRietfontein (formerly ‘Boshoek’) diamictite, which more recent work places below the unconformity beneath the Boshoek–Hekpoort sequence (Coetzee et al., 2006). Alternatively,Ongeluk volcanism (b2.41 Ga) is inferred to be much older than Hekpoort volcanism (2.22–2.24 Ga, Dorland, 2004), and the Makganyene glaciation is correlated with either the basalDuitschland diamictite (Moore et al., 2001), a pre-Duitschland glaciation (Moore et al., 2012), or the unconformity (MD) in the middle Duitschland Formation (Fig. 4), across whichthe GO appears to occur based on MIF-S proxy data (Guo et al., 2009).



Supergroup, bordering the Kheis belt (Beukes and Smit, 1987), shallowdips combined with subdued topography and 290 million years ofpostglacial weathering engender a strong reliance on boreholes.

3.1.1. Ghaap and Chuniespoort groupsThe lower part of the Transvaal Supergroup (~2.60-2.50 Ga) is

dominated by a thick shallow-water carbonate platform (Fig. 3), theMalmani–Campbellrand platform, the western margin of which andcoeval deepwater basinal facies are preserved in the far southwest ofthe Griqualand West basin (Beukes, 1987; Sumner and Beukes, 2006;Fischer et al., 2009). In both basins, the carbonate platform is conform-ably overlain by iron-formation—the banded Kuruman and granularGriquatown iron-formations of the Asbestos Hills (Asbesheuwels)Subgroup in the west (Beukes, 1984), dated at 2460 ± 5 (Pickard,2003) and 2431 ± 31 Ma (Trendall et al., 1990) respectively, and thePenge Formation in the east dated at 2480 ± 6 Ma (Nelson et al.,1999). In the west, the conformable sequence continues through theKoegas Subgroup, in which iron-formation is interleaved with fine-grained siliclastics and minor carbonate (Beukes, 1983; Beukes andGutzmer, 2008; Schröder et al., 2011). An isolated lens of diamictite ofpossible glacial origin occurs within the Doradale iron-formation atthe base of the Koegas Subgroup (Polteau et al., 2006).

An erosion surface of undoubted glacial origin truncates the Koegasand upper Asbestos Hills subgroups progressively northeastwardonto the Campbellrand platform area (Fig. 3)(Coetzee et al., 2006).Basinward, this unconformity continues to cut up-section, revealingyounger units (Klipput lutite and Nelani iron-formation) on thehanging-wall of the Blackridge thrust fault, which are not present onthe footwall (Beukes and Smit, 1987; Schröder et al., 2011). Interleavingof iron-formation and diamictite is reported in the deep basin (Polteauet al., 2006), but this could be the result of tectonic imbrication relatedto amajor thrust fault (middle Koegas over lower Olifantshoek) locateda few meters below the basal diamictite (Fig. 3 in Polteau et al., 2006).Iron-formation of the Rooinekke Formation of the middle KoegasSubgroup has reportedly been dated at 2415 ± 6 Ma (Kirschvinket al., 2000; see also Beukes and Gutzmer, 2008, p. 40), which wouldbe a maximum age constraint on the Makganyene glaciation. In theEastern Transvaal basin, iron-formation of the Penge Formation and fer-ruginous dolomite rhythmite of the conformably overlying TongwaneFormation are beveled by a widespread erosion surface overlain by adistinctive chert-breccia/conglomerate (Bevetts conglomerate), whichmarks the base of the Duitschland Formation and the stratigraphicallyhomologous Rooihoogte Formation at the base of the Pretoria Group(Coetzee, 2001). The chert-breccia/conglomerate is draped by mud-stone with rafted granules and a polymictic diamictite carrying intra-and extrabasinal debris, including striated and bullet-shaped clasts ofglacial origin (Coetzee, 2001; Bekker et al., 2001, 2004). Remarkably,the lower Transvaal Supergroup ends at a glacial erosion surface inboth areas, yet correlation of the directly overlying glacial deposits—the Makganyene Formation in the west and the basal DuitschlandFormation in the east—has very few advocates (Moore et al., 2001).

The amplitude of the unconformities at the base of the Postmasburgand Pretoria groups with respect to underlying stratigraphy (Fig. 3)might lead one to infer a long hiatus. However, depth of erosion is astronger function of uplift than of time. The density of iron-formation,which after diagenesis and burial equals or even exceeds that ofasthenospheric mantle, means that basin-scale lateral variation iniron-formation thickness, as for example in the Asbestos Hills Subgroupacross the Campbellrand platform-to-basin transition, would haveinduced significant lithospheric flexure through differential sedimentloading (Cisne, 1984). This would have caused deepening of the areaswhere iron-formation was thickest and uplift of intervening arches(e.g. Vryburg arch). The timing of iron-formation induced flexurewould have reflected the densification of iron-formation duringdewatering, diagenesis and burial, processes that would have beenactive on the 108 year timescale of iron-formation deposition in the

Asbestos Hills and Koegas subgroups (Fig. 4). In this scenario, no longhiatus and no externally imposed tectonic flexure were required to ac-count for the toplap relations observed at the base of the Postmasburgand Pretoria groups (Fig. 3). The sub-Makganyene unconformity inthe basin attests to the magnitude of base-level fall associated withlow-latitude glaciation.

3.1.2. Postmasburg GroupThere is disagreement over correlations between the mega-

sequences above the respective glacial surfaces—the PostmasburgGroup in the west and the lower Pretoria Group (Hekpoort Formationand below) in the east (Fig. 3). The Postmasburg Group comprisesfour conformable formations—the glacigenic Makganyene Formation,comprising 3–70 m (b500 m locally) of massive and subordinate strat-ified diamictite of northeasterly derivation, locally containing facetedandmultiply-striated clasts, poorly-sorted sandstone and conglomerate,andMn-rich carbonate stromatolites (Visser, 1971, 1981; De Villiers andVisser, 1977; Evans et al., 1997; Polteau et al., 2006); the subaqueousvolcanic Ongeluk Formation, 500–1000 m of basaltic andesite pillowlava, hyaloclastite (pillow-breccia), tuff and jaspilite (Grobler and Botha,1976; Cornell et al., 1996; Evans et al., 1997; Gutzmer et al., 2001); theeconomic Hotazel Formation, 100–250 m of alternating iron and manga-nese carbonates, oxides and silicates (Tsikos and Moore, 1997, 1998;Kirschvink et al., 2000; Tsikos et al., 2003, 2010; Schneiderhan et al.,2006); and the erosionally-truncated Mooidraai Formation, b222 m ofisotopically-unremarkable (δ13C = −2 to −1‰ VPDB, Vienna PeedeeBelemnite) Fe-rich limestone and dolomite (Tsikos et al., 2001).

Makganyene glaciation and Ongeluk volcanism are inferred tohave overlapped in time because diamictite/lava contacts appear con-formable and lack paleosols in borehole cores (de Villiers and Visser,1977; Evans et al., 1997), because volcanic shards and fragments areabundant in the upper part of the Makganyene Formation (de Villiersand Visser, 1977; Evans et al., 1997), and because diamictite and lavainterfinger (Kirschvink et al., 2000; Polteau et al., 2006). During thelast Quaternary deglaciation, global volcanic activity increased two tosix times above background due to mantle decompression (Huybersand Langmuir, 2009), so the coincidence of Ongeluk volcanism andMakganyene deglaciation might not be fortuitous. Accordingly, thetilt-corrected paleomagnetic pole for the Ongeluk Formation (charac-teristic remanent magnetization component with high-coercivity andhigh-unblocking temperature, supported by a positive volcanic brecciatest and a reversely directed site), implying a depositional paleolatitudeof 11 ± 5°, provides strong evidence for low-latitude glaciation in amaritime setting (Evans et al., 1997; Kirschvink et al., 2000). The sub-aqueous nature of Ongeluk volcanism is not surprising, consideringthe massive rise in global mean sea-level that would accompany low-latitude deglaciation. In the basal Hotazel Formation, dropstones anddiamictite bodies have been cited as evidence for glaciation after volca-nism waned (Kirschvink et al., 2000; Kopp et al., 2005; Polteau et al.,2006), but could alternatively be products of late-stage volcanic activityitself (e.g. dropstones as volcanic ejecta, diamictites as lahars).

A Pb/Pb isochron date of 2394 ± 26 Ma for carbonate-bound Pb indolomitized Mooidraai Formation is interpreted as an age of dolomi-tization (Bau et al., 1999). This is incompatible with the interpretationof a whole-rock Pb–Pb isochron date of 2222 ± 12 Ma from theOngeluk volcanics as the age of sub-seafloor alteration (Cornell et al.,1996). The age of Ongeluk volcanism, coeval withMakganyene deglaci-ation, is considered further toward the end of this section.

Atmospheric pO2 b10−5 PAL is indicated by large Δ33S anomaliesin sulfide (b+8.0‰) and sulfate minerals from the 2.60–2.52-GaCampbellrand carbonate platform (Sumner and Bowring, 1996;Farquhar et al., 2000; Guo et al., 2009; Ono et al., 2009a, b). Redox-sensitive trace metal abundances in coeval strata indicate the presenceof some dissolved O2 in seawater (Wille et al., 2007; Kendall et al.,2010). In fact, the evolution of oxygenic photosynthesis and the resul-tant rise in atmospheric O2 from b10−11 to 10−7 PAL could have caused



the observed maximum in MIF-S between ~2.72 and ~2.50 Ga, by low-ering the fraction of S8 in the exit channel of reduced aerosol species andthereby increasing (to maintain mass balance) the magnitude its MIF(Kurzweil et al., 2013). MIF of reduced magnitude (Δ33S ≤ 1.9‰) inthe younger Koegas Subgroup (Fig. 3) could reflect a further rise inatmospheric O2 from 10−7 to 10−5 PAL before the GO, causing theloss of S8 in the exit channel (Kurzweil et al., 2013). Following theMakganyene glaciation, strongly oxidizing conditions are implied byMn4+-rich intervals b50 m thick in the Hotazel Formation, one of theworld's largest Mn ore-deposits (Laznicka, 1992; Tsikos and Moore,1998; Kirschvink et al., 2000; Kopp et al., 2005), as well as by extremelylight Fe-isotope compositions in the associated iron-formation (Tsikoset al., 2010) and miniscule Δ33S anomalies (b0.05‰) in sulfate andsulfide from the Mooidraai Formation (Guo et al., 2009).

3.1.3. Lower Pretoria GroupThe gradational nature of contacts between formations within the

Postmasburg Group contrasts with the multiple unconformity-bounded sequences (Fig. 3) in the lower Pretoria Group of the EasternTransvaal basin (Bekker et al., 2001, 2004; Coetzee, 2001; Hannahet al., 2004; Coetzee et al., 2006; Frauenstein et al., 2009; Guo et al.,2009). Another difference is the existence of at least two discreteglacial horizons in the Eastern Transvaal, one near the base of theDuitschland/Rooihoogte Formation (Bekker et al., 2001; Coetzee, 2001)and another at the top of the Timeball Hill Formation, named theRietfontein Member (Coetzee et al., 2006). The Duitschland Formation

referred to here includes the stratigraphically equivalent RooihoogteFormation from the opposite (southwestern) side of the basin(Coetzee, 2001; Hannah et al., 2004; Coetzee et al., 2006). The basalDuitschland diamictite extends basinwide and carries extrabasinal aswell as local debris, including multiply-striated, bullet-shaped clasts(Coetzee, 2001; Bekker et al., 2001). The diamictite is directly overlainby a thick shale containing the maximum flooding zone of the first ofthree (Bekker et al., 2001) to six (Guo et al., 2009) shale–carbonate–siliciclastic depositional sequences within the 1.0-km-thick DuitschlandFormation. A major sequence boundary occurs ~410 m above the baseof the formation (Bekker et al., 2001; Guo et al., 2009). The sequencebelow it is truncated and the surface is overlain by conglomerate. Inthe sequences above this surface, carbonate rocks are strongly enrichedin 13C and 34S relative to those below it (Bekker et al., 2001, 2004).More-over, MIF in carbonate-hosted sulfate and sulfide from above thesequence boundary is small (average Δ33S = 0.11‰, n = 28), whilebelow that surface it is large (average Δ33S = 0.82‰, n = 13) (Bekkeret al., 2004; Guo et al., 2009). The correlation scheme proposedin Section 6 hinges on the significance of this sequence boundary inthe middle Duitschland Formation, referred to hereafter as the MDdisconformity.

The Timeball Hill Formation overlies a well-developed sequenceboundary at the top of the Duitschland Formation and comprises twocoarsening-upward siliciclastic sequences of northerly provenance,each ~250 m thick, separated by a compound marine flooding surface(Coetzee, 2001; Coetzee et al., 2006). Both sequences begin with

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Fig. 4. Correlation chart (time on y-axis) of sedimentary and volcanic cover between 3.0 and 2.0 Ga in age on the Kaapvaal craton of southern Africa. Glacial horizons are indicatedby inverted black triangles, while the GO is shown by the row of open stars. The ranking code for stratigraphic names is shown in lower left. Radiometric dates (see text for sources,methods and analytical uncertainties) include only inferred depositional ages. The Postmasburg Group is not correlated with the lower Pretoria Group (Moore et al., 2001, 2012).The low-latitude Makganyene glaciation is equated with the middle Duitschland (MD) sequence boundary, across which the GO (Fig. 3) occurs (Guo et al., 2009).Three Paleoproterozoic glaciations are inferred, all older than ~2.30 Ga. The ‘standard’ correlation (Fig. 1) is radically different, equating the Makganyene and Rietfontein (upperTimeball Hill) glaciations and raising both closer in age to the Hekpoort volcanics ~2.25 Ga. Such a young age leaves the low-latitude Makganyene glaciation with no known glacialcorrelative in the world outside southern Africa.



organic-rich black shale holding abundant framboidal pyrite. MIF-S isvirtually absent in both units (Bekker et al., 2004). Three pyrites (onea replicate) from the base of the older sequence and four pyrites fromthe uppermost Rooihoogte Formation in the same drill cores define aseven-point Re/Os isochron with an age of 2316 ± 7 Ma and a chon-dritic initial 187Os/188Os ratio (Hannah et al., 2004). The older TimeballHill sequence culminates in a complex of deltaic sandstone bodies andoolitic ironstones, whereas the younger sequence grades at the topinto polymictic diamictite and conglomerate of the RietfonteinMember,the glacial origin of which is inferred from abundant faceted andbullet-shaped, multiply-striated pebbles (Coetzee et al., 2006). Soft-sediment deformation is conspicuous in the transition zone beneaththe diamictite and the gradational nature of the contact refers theRietfontein glaciation to the upper Timeball Hill sequence (Coetzeeet al., 2006). In situ U–Pb zircon dating of microtuff horizons in theTimeball Hill Formation below the diamictite gives a preliminary ageof ~2.31 Ga (Bekker et al., 2010). The Rietfontein Member is sharplyoverlain by poorly-sorted chert-pebble conglomerate of the basalBoshoek Formation, which grades upward through mixed volcaniclasticgreywackes and lava flows into ~600 m of subaerial, basaltic-andesite,lava flows, pyroclastic breccia, lapilli-tuff and derived volcaniclasticsrocks of the Hekpoort Formation (Oberholzer and Eriksson, 2000;Coetzee, 2001). The youngest concordant detrital zircon grains fromvolcaniclastic beds within the middle Hekpoort Formation have U–Pbdates of 2243 ± 11 Ma (SHRIMP) and 2225 ± 3 Ma (TIMS), presum-ably reflecting the age of Hekpoort volcanism (Dorland, 2004). Abovethe Hekpoort Formation, the upper Pretoria Group (Coetzee, 2001)can be readily correlated with the lower Olifantshoek Supergroup inGriqualand West (Fig. 3). Basal redbeds overlie a tropical lateriticpaleosol in both areas (Gutzmer and Beukes, 1998; Beukes et al.,2002; Evans et al., 2002; Dorland, 2004; Yamaguchi et al., 2007), andmatching carbonate units have highly-enriched δ13C values (~10‰VPDB) and minor associated Ca-sulfate evaporite (Schröder et al., 2008;Frauenstein et al., 2009).

3.2. Problems in correlation

Having laid out the basic stratigraphic framework, we must nowconfront alternative correlations between the Postmasburg Group inthe west and the lower Pretoria Group in the east. Much is at stake be-cause the GO and the Paleoproterozoic glacial record are encompassedby these rocks.

In the standard interpretation (Figs. 1, 3), the Ongeluk andHekpoortvolcanics are correlated and, by association, the Makganyene andRietfontein glaciations are equated (Eriksson et al., 1993; Cheney andWinter, 1995; Evans et al., 1997, 2002; Kirschvink et al., 2000; Bekkeret al., 2001, 2004, 2010; Hannah et al., 2004; Kopp et al., 2005;Coetzee et al., 2006; Frauenstein et al., 2009; Guo et al., 2009). Compat-ibility of the whole-rock Pb/Pb isochron age of 2222 ± 12 Ma for alter-ation of the Ongeluk volcanics (Cornell et al., 1996) with dates of 2.24–2.22 Ga for the youngest population of concordant zircons grains involcaniclastic rocks of the Hekpoort Formation (Dorland, 2004) sup-ports this interpretation, assuming that the age of alteration of theOngeluk volcanics was close to the time of their eruption. Most adher-ents to the standard model place the Rietfontein diamictite at the baseof the Boshoek–Hekpoort depositional sequence, not in the upperTimeball Hill sequence as interpreted by Coetzee et al. (2006). It followsfrom the standard model that the low-latitude Makganyene glaciationoccurred well after the GO (Fig. 1), ~100 Myr or more afterwards ifwe take the Re–Os isochron age of 2316 ± 7 Ma for deposition acrossthe Rooihoogte (=Duitschland)-Timeball Hill transition (Hannahet al., 2004) as aminimum constraint on the age of the GO in themiddleDuitschland Formation (Guo et al., 2009).

An iconoclastic interpretation rejects the Ongeluk–Hekpoort corre-lation and considers the Postmasburg Group to be entirely older thanthe lower Pretoria Group, with the possible exception of the lower

Duitschland/Rooihoogte Formation, which would then be placedbelow the Pretoria Group (Moore et al., 2001). In this interpretation,erosion beneath the sequence boundary at the base of the PretoriaGroup erased the record of Postmasburg Group deposition in theEastern Transvaal, and erosion beneath the sequence boundary at thebase of the Olifantshoek Supergroup destroyed the record of lowerPretoria Group deposition in Griqualand West (Moore et al., 2001).The interpretation is supported by the lithological affiliation of thenonglacial Postmasburg sedimentary strata, mostly chemical, to theChuniespoort Group rather than the siliciclastic-dominated lowerPretoria Group. It is conditionally supported by the 2394 ± 26 MaPb–Pb isochron date from the Mooidraai Formation, assuming it to bea reliable age of dolomitization and therefore a minimum constrainton the Makganyene glaciation (Bau et al., 1999). However, mobilityof carbonate-hosted U and Pb makes the Mooidraai isochron ageunreliable. Correlation between the Ongeluk and Hekpoort volcanicson geochemical grounds is problematic because trace element signa-tures are broadly uniform for 13 different basaltic volcanic sequenceserupted onto the Kaapvaal craton between 3.0 and 2.1 Ga, pointing torepeated melting of a uniformly metasomatized tectosphere (Myerset al., 1987). Rb–Sr and Pb–Pb whole-rock isochron ages ~2.2 Ga forboth the Ongeluk and Hekpoort volcanics (Burger and Coertze, 1973;Cornell et al., 1996) may date low-temperature groundwater flowdriven by orogenic topography in the Limpopo belt, a likely source forPretoria Group clastics. Broadly similar isochron ages were obtainedfrom volcanics of the Ventersdorp Supergroup, which later gave U–Pbzircon dates of ~2.71 Ga (Armstrong et al., 1991).

Recent U–Pb dating of detrital zircon suites underscores the con-trast in provenance and probable age between the Postmasburg andlower Pretoria groups (Moore et al., 2012). The youngest concordantgrains fromgraded sandstone beds associatedwith diamictite at the topof the Makganyene Formation and from ice-rafted debris at the base ofthe Hotazel Formation are 2436 ± 7 Ma (4% discordant) and 2460 ±21 Ma (3% discordant), respectively (Moore et al., 2012). These datescompare with the youngest concordant grain (0% discordant) in alarge detrital suite from high in the upper Duitschland Formationdated at 2424 ± 12 Ma (Dorland, 2004). In contrast, the youngest con-cordant grains in deltaic sandstone beds from the lower Timeball Hillsequence and volcaniclastic beds from the middle Hekpoort Formationare 2324 ± 17 Ma (−3% discordant) and 2225 ± 3 Ma (0% discor-dant), respectively (Dorland, 2004). The youngest concordant grainfrom sandstone identified as basal Ditojana Formation in the Kanyeinlier on the Vryburg arch is 2240 ± 12 Ma (2% discordant), suggestingthat the basal Segwagwa (=Pretoria) Group in this area, whichlies unconformably on iron-formation correlative with the upperChuniespoort Group (Taupone Group), is significantly younger thanthe Timeball Hill Formation, with which it is usually correlated(Mapeo et al., 2006). However, the sample coordinates given suggestthat the sandstone may instead belong to the Daspoort Formation,above the Hekpoort volcanics (Fig. 3), in which case it does not bearon the age of the lower Pretoria Group (N. Beukes, pers. comm.). Collec-tively, these observations (excluding the last) make it plausible that theMakganyene glaciation and Ongeluk volcanism were ~2.40 Ga in age,possibly coeval with the Duitschland Formation, and that the TimeballHill Formation (~2.31 Ga) and Boshoek–Hekpoort (~2.24-2.22 Ga)formations are distinctly younger than the Postmasburg Group (Fig. 4)(Moore et al., 2001, 2012). Opposite to the standard interpretation, cor-relation with the basal Duitschland glaciation makes the low-latitudeMakganyene glaciation older than the GO (Guo et al., 2009).

4. Western Australia

4.1. Turee Creek Group, Pilbara craton

The Hamersley Ranges of Western Australia are underlain by abroadly-folded late Neoarchean–early Paleoproterozoic platformal



succession whose chronometrically-calibrated sequence stratigraphy isso remarkably similar to the Ventersdorp and Transvaal supergroups ofsouthern Africa (Cheney, 1996;Martin et al., 1998) that geologists haveinferred a former conjunction of the Pilbara and Kaapvaal Archeancratons, called Vaalbara (Zegers et al., 1998; de Kock et al., 2009;Smirnov et al., 2013). In Western Australia, a single glacial marineunit, the Meteorite Bore Member (Trendall, 1976; Martin, 1999), occurswithin a thick siltstone and shale-dominated sequence, the KungarraFormation (lower Turee Creek Group), which has been correlated withthe Duitschland Formation (Cheney, 1996). The Kungarra Formationconformably overlies the Hamersley Group, a succession dominatedby iron formation that contains numerous tuff horizons yielding U–Pbzircon dates ranging from ~2630 Ma at the base of the group to2445 ± 5 Ma near the top (Trendall et al., 2004). The younger date istherefore a maximum for the Meteorite Bore glaciation, which mustbe significantly older than 2208 ± 10 Ma, the U–Pb baddeleyite age ofmafic sills that intrude the entire Turee Creek Group (Müller et al.,2005). The Meteorite Bore Member tapers northwestward from~450 m of mainly massive diamictite with faceted and striated stonesand siltstone interbeds in Hardey Syncline, to b5 m of laminatedsiltstone and sandstone with IRD in Duck Creek Syncline (Martin,1999). The Meteorite Bore glaciation has been correlated with thebasal Duitschland (Cheney, 1996) and Makganyene (Martin, 1999)diamictites. Large MIF anomalies (Δ33S = −1.93 to +8.99‰) occurin authigenic pyrite of the ~2.50-Ga Mount McRae Formation (Onoet al., 2003; Kaufman et al., 2007) and smaller ones (Δ33S = −0.8 to+1.0‰) appear throughout the Meteorite Bore Member in the moredistal section (Duck Creek Syncline), despite a wide range in mass-dependent fractionation (δ34S = −45 to +46‰ VCDT), implyingmicrobial sulfate reduction under non-sulfate limiting conditions(Williford et al., 2011). These findings are consistent with a model inwhich rising seawater sulfate levels led to the collapse of atmosphericCH4, triggering a severe glaciation and the concomitant rise of O2

(Zahnle et al., 2006). The Meteorite Bore glaciation was therefore corre-lated with the “lower glacial units” (Ramsay Lake and Bruce formations)in theHuronian Supergroupand the “lower part of theUpperDuitschlandFormation” in the Transvaal Supergroup (Williford et al., 2011).

5. Arctic Europe

5.1. Sariolian Group, Kola–Karelia craton

Glacialmarine deposits arewidespreadwithin the SariolianGroup, adeformed andmetamorphosed conglomeratic cover succession of earlyPalaeoproterozoic age on the Archean Kola–Karelia craton (Marmo andOjakangas, 1984; Ojakangas et al., 2001;Melezhik, 2006, 2013). At leasttwo glacial advances are inferred in central Finland (Melezhik, 2013),but it is not clear if these represent discrete glacial epochs like thosein North America (Ojakangas, 1988). The Sariolian Group unconform-ably overlies a major flood-basalt (and minor sedimentary) sequence,the Sumi group, the youngest (intrusive) components of which haveU–Pb zircon dates of 2441 ± 1.6 and 2432 ± 6 Ma (Melezhik, 2006).A minimum age for Sariolian glaciation is tentatively provided by aRb–Sr isochron date of 2330 ± 38 Ma for basaltic volcanics overlyingSariolian conglomerate in the northern Kola Peninsula (Melezhik,2006). Reliable paleomagnetic poles place the Kola–Karelia craton at~35° paleolatitude at 2.45 Ga and ~15° at 2.06 Ga, but no reliablepoles exist between those dates (Mertanen et al., 2006; Evans andPisarevsky, 2008; Bindeman et al., 2010). Extreme depletions of 18Oin high-grade metamorphic minerals are found throughout theBelamorian Belt of northern Karelia (Bindeman et al., 2010; Bindemanand Serebryakov, 2011). Their protoliths are inferred to have beenhydrothermally-altered by meteoric waters derived from Sariolianice-sheet meltwater. The timing of the GO is weakly constrained(Papineau et al., 2005; Melezhik, 2013), pending final results from theFennoscandia Arctic Russia–Drilling Early Earth Project (FARDEEP).

6. Toward a MIF-S based correlation scheme

Attempts to correlate early Paleoproterozoic glacial epochs globallyface a fundamental limitation. A minimum of three discrete glacialepisodes are represented by a total of 13 formations on six cratons. Incomparison, three Neoproterozoic glaciations are represented by over90 formations on 22 cratons (Hoffman and Li, 2009; Evans and Raub,2011).

Whether despite or because of this limitation, most previously sug-gested correlation schemes share a ‘common link’: correlation betweenthe older glaciation in the Eastern Transvaal (basal Duitschland/Rooihoogte) and the second Huronian glaciation (Bruce/Vagner) inNorth America (Bekker et al., 2001, 2004; Williford et al., 2011; Mooreet al., 2012). Moore et al. (2012) equate the Makganyene with thefirst Huronian (Ramsay Lake) glaciation, while the other authors equatethe Makganyene (and Rietfontein) glaciation with the third Huronian(Gowganda) glaciation. The ‘common link’ among these suggestionsis incompatible with existing atmospheric redox proxy data in theabsence of a MIF-S reversal. The absence MIF-S in the Espanola Forma-tion (Fig. 2), including the postglacial cap-carbonate at its base(Papineau et al., 2007), and the radiogenic Os spike indicating oxidativeweathering during Bruce deglaciation (Sekine et al., 2011a) conflictwith the presence of MIF-S between 300 and 400 m stratigraphicallyabove the basal Duitschland/Rooihoogte diamictite (Guo et al.,2009). For the ‘common link’ to be correct, oxygen levels musthave risen sharply during deglaciation and its aftermath in North Amer-ica, only to fall below 10−5 PAL for a significant time in South Africa be-fore rising once again above 10−5 PAL in upper Duitschland time, wellbefore the Rietfontein glaciation. This has not been observed in anyone region.

Correlating the older glaciation in the Eastern Transvaal with thethird Huronian glaciation (Kopp et al., 2005) creates, in addition tothe miscorrelation in MIF-S disappearance (Fig. 1), a conflict betweenthe existence of MIF-S in the lower Duitschland Formation (Guo et al.,2009) and Mn-enrichment in redbeds associated with the thirdHuronian postglacial marine inundation (Sekine et al., 2011b).

More problematic for the standard model in southern Africa is thefact that if the low-latitude (11 ± 5°) Makganyene glaciation actuallyoccurred ~2.22 Ga (Figs. 1, 3), then the Padlei Formation (Aspler andChiarenzelli, 1997) is its only other potential representative anywhereelse in the world.

In the alternative correlation scheme proposed here (Figs. 4–5), theGO (i.e. disappearance of MIF-S) is the primary basis for correlation. Inan anoxic atmosphere, MIF is produced by photochemical reactionsinvolving volcanogenic sulfur species (mainly SO2 and H2S), resultingin 33S excess (positive Δ33S) in reduced aerosols, mainly elemental S8,and 33S deficiency (negative Δ33S) in oxidized aerosols, mainly H2SO4.When O2 exists in the atmosphere in concentrations >10−5 PAL,back-reactions between reduced and oxidized sulfur species efficientlyerase the MIF signal in the atmosphere (Farquhar et al., 2000; Pavlovand Kasting, 2002). The mixing time of the troposphere is geologicallyinstantaneous, ~1 year (Bolin, 1976), so the transfer of the MIF signalfrom sulfur aerosols into sedimentaryminerals would have determinedthe speedwithwhich the sedimentary record responded to atmospher-ic change (Farquhar andWing, 2003). Under a low-O2 atmosphere, thisresponse time would have been relatively fast because the surface res-ervoir of mobile sulfur was small compared with the present, which isdominated by seawater sulfate (Ono et al., 2003; Farquhar et al., 2013;Halevy, 2013). However, care must be taken to avoid sampling detritalpyrite, which might carry MIF-S from older source rocks.

Oscillation between oxic and anoxic atmospheres during a finiteGO has been modeled (Claire et al., 2006) but is not observed in theexisting MIF-S record (Farquhar et al., 2010). The greater lifetime ofO2 in a troposphere with >10−5 PAL O2, due to stratospheric ozoneshielding, may have stabilized tropospheric O2 above that level(Goldblatt et al., 2006). The proposed correlation (Fig. 5) assumes



that the GO was irreversible at the resolution of the existing MIF-Srecord.

The new scheme (Fig. 5) also assumes that the GO was closelyassociated with a global cooling episode, possibly a snowball Earth,because of rapid destruction of reduced greenhouse gases (Pavlovet al., 2000; Catling and Claire, 2005; Kopp et al., 2005; Kasting andOno, 2006; Liang et al., 2006; Zahnle et al., 2006; Kirschvink and Kopp,2008). The MIF-S record is as yet too coarse to test such a connectionempirically with stratigraphic precision (Farquhar et al., 2000; Bekkeret al., 2001, 2004; Papineau et al., 2007; Guo et al., 2009; Willifordet al., 2011; Melezhik, 2013). In the Eastern Transvaal basin (Figs. 3–4),for example, the disappearance of MIF-S is stratigraphically constrainedto occur in a 300-m data gap in the middle of the km-thick DuitschlandFormation, above theMD sequence boundary, which is overlain by con-glomerate (Bekker et al., 2004; Guo et al., 2009). No glacial deposit isknown at this horizon, which lies >400 m stratigraphically above thebasal Duitschland diamictite (Guo et al., 2009) and nearly 1000 mbelow the Rietfontein diamictite (Coetzee et al., 2006). In Fig. 4, theMD sequence boundary is assumed to be a cryptic glacial erosionsurface across which the MIF-S disappears. The only reason to makethese assumptions is that they lead to a simpler global correlationscheme (Fig. 5). A glacial erosion surface lacking mappable glacialdeposits is not unusual: the younger Cryogenian (Marinoan) glaciation,for example, left a continuous ice grounding-zone sedimentary wedgeon the former continental slope of northern Namibia, but the adjacentcarbonate shelf was swept nearly free of glacial deposits (Domack andHoffman, 2011). Large areas of the Canadian Shield are all but devoidof Pleistocene deposits, despite having spent most of the past 2.6 Mabeneath the Laurentide Ice Sheet. The action of such an ice sheetleaves debris around its margins, but only locally in its interior. Never-theless, subtle evidence for glaciation should exist at or above theMD disconformity if the new scheme (Fig. 5) is correct (e.g. striatedpavement, lodgement facies, hydrofractured block field, polygonalsand wedges, extreme 18O depletion, erratic dropstones in overlyingshale).

In GriqualandWest (Figs. 3–4), the GO is constrained by the absenceof MIF-S in the Mooidraai Formation (Guo et al., 2009), by verylow δ57Fe values in the Hotazel Formation, especially in Mn-richsamples (Tsikos et al., 2010), and by deposition of the MnO2-ore itself

(Kirschvink et al., 2000; Kopp et al., 2005), all of which imply atmo-spheric O2 > 10−5 PAL, likely ≫10−5 PAL, following the Makganyeneglaciation. This appears to rule out a pre-Duitschland age for theMakganyene glaciation (Moore et al., 2012), and also its correlationwith the basal Duitschland diamictite (Moore et al., 2001), which isoverlain by 400 m of lower Duitschland strata with significant MIF(Δ33S > 0.5‰)(Guo et al., 2009). The existence of MIF-S within theKoegas Subgroup (Ono et al., 2008) suggests that the basal Koegas(Doradale) diamictite (Polteau et al., 2006), if glacigenic, would repre-sent a pre-GO event like the basal Duitschland/Rooihoogte glaciation(Fig. 5).

The standard correlation (Makganyene = Rietfontein) is notfollowed here (Fig. 5) because of arguments advanced by Moore et al.(2001, 2012). The age of the youngest concordant detrital zircons inthe Makganyene diamictite and the upper Duitschland Formation isindistinguishable, 2436 ± 7 Ma (n = 67) and 2424 ± 12 Ma (n =72) respectively (Dorland, 2004; Moore et al., 2012). In contrast, theyoungest concordant ages in detrital zircon suites bracketing theRietfontein diamictite are 100–200 Myr younger, 2324 ± 17 Ma fromthe Timeball Hill Formation and 2225 ± 3 Ma from the HekpoortFormation (Dorland, 2004). An age ~2.40 Ga for the Makganyeneglaciation is consistent with a minimum age (for dolomitization) of2394 ± 6 Ma from the Mooidraai Formation (Bau et al., 1999). Adistinctly younger age for the Rietfontein glaciation follows from theRe–Os isochron date of 2316 ± 7 Ma from the basal Timeball HillFormation (Hannah et al., 2004) and from a preliminary U–Pb zircondate of ~2.31 Ga from a microtuff in the lower part of the same forma-tion (Bekker et al., 2010). Although not definitive, this evidence favorsan older (pre-Rietfontein) age for the Makganyene glaciation (Mooreet al., 2001, 2012).

Assuming the Rietfontein glaciation is younger than theMakganyene, its record in Griqualand West must have been destroyedby erosion beneath the Olifantshoek Supergroup (Fig. 4). Similarly, therecord of the basal Duitschland glaciation in Griqualand West couldhave been destroyed by erosion during the subsequent Magkanyeneglaciation. Alternatively, the basal Duitschland glaciation could berepresented by the lens of Makganyene-like diamictite in the DoradaleFormation at the base of the Koegas Subgroup (Polteau et al., 2006),which would constrain its age (Fig. 5) between 2431 ± 31 Ma

Headquarters Gowganda Rietfontein

Vagner Bruce Makganyene Meteorite Bore?

Ramsay LakeCampbell Lake Duitschland

WYOMING HURONIAN GRIQUALAND WEST

EASTERN TRANSVAAL

PILBARA

MD disconformity

G1

G2

G3

TIM

E

Doradale?

2225 + 3 Ma6-

2316 + 7 Ma5-

2415 + 6 Ma4-

2431 + 31 Ma2-2444

+ 8 Ma1

- 42445 + 5 Ma3

-

Meteorite Bore?

Fig. 5. Proposed correlation of early Paleoproterozoic glacial epochs (G1–3) in North America, southern Africa and Western Australia. Heavy box indicates low-latitude glaciationand cap carbonates are shown above the Bruce and Vagner diamictites. Dark shaded boxes indicate atmospheric anoxia (MIF-S, detrital FeS2 and UO2, reduced paleosols) betweenglaciations; light shaded boxes indicate oxic atmosphere (MIF-S absent, no unstable derital minerals, oxic paleosols); unshaded boxes have no atmospheric redox proxy data.Depositional age constraints are U–Pb dates for zircon from rhyolite lava1 and tuffs2−4, a Re–Os isochron from organic-rich black shale5, and a U–Pb (TIMS) date for detrital zirconinferentially derived from contemporaneous Hekpoort volcanics6: 1Krogh et al. (1984); 2Trendall et al. (1990); 3Trendall et al. (2004); 4Kirschvink et al. (2000), Beukes andGutzmer (2008); 5Hannah et al. (2004); 6Dorland (2004). In this correlation, only three glaciations are needed globally, all are represented in southern Africa, and the second(G2) was a snowball Earth associated with the Great Oxidation (GO).



(Trendall et al., 1990) and 2415 ± 6 Ma (Kirschvink et al., 2000). Theinferred contrast in epeirogenic history between the Griqualand Westand Eastern Transvaal basins, and the apparent abrupt (~100 km) tran-sition, might relate to the contrasting crustal blocks on which they re-side, which collided ~2.9 Ga along a geosuture in the sub-Ventersdorpbasement beneath the Vryburg arch (Schmitz et al., 2004).

In the Huronian Supergroup (Fig. 2), MIF-S disappears between thetop of the Pecors and the base of the Espanola formations (Papineauet al., 2007). As MIF-S data are lacking from the fluviatile MississagiQuartzite and glacigenic Bruce diamictite, the GO is assumed to beconnected with the Bruce glaciation, as indicated by redox-sensitivetrace metals (Sekine et al., 2011a). The Bruce is the only Huronianglacial formation overlain by a ‘cap-carbonate’, the only mappable car-bonate unit in the Huronian Supergroup (Young, 1973a; Bernsteinand Young, 1990; Bekker et al., 2005). Postglacial cap-carbonates arecharacteristic and arguably diagnostic features of the proposed snow-ball Earth glaciations of Cryogenian age (Hoffman and Schrag, 2002;Higgins and Schrag, 2003; Bao et al., 2008; Evans and Raub, 2011).As the second of three Huronian glaciations, the Bruce is correlatedwith the lower Vagner Formation diamictite of the Wyoming craton,which is also overlain by a cap-carbonate (middle Vagner Formation),the only postglacial cap-carbonate in the Snowy Pass Supergroup(Karlstrom et al., 1983; Bekker et al., 2003, 2005). Moderately depletedδ13C values (−2 to −4‰ VPDB) of these North American cap-carbonates (Bekker et al., 2005) donot necessarily conflictwith stronglyenriched values (+2 to +7‰ VPDB) in the upper Duitschland Forma-tion (Guo et al., 2009). The enriched values come from carbonatelocated >280 m above the MD disconformity, in the second postglacialdepositional sequence (Guo et al., 2009). Depleted δ13C values inNeoproterozoic cap-carbonates typically rise to strongly enrichedvalues rapidly up-section (e.g. Yoshioka et al., 2003; Halverson et al.,2010; Jiang et al., 2011).

If we accept the proposed correlations in southern Africa (Fig. 4), oreven if we only accept that the GO is associated with an MD sequenceboundary of glacial origin in the Eastern Transvaal, correlations withNorth America are greatly simplified (Fig. 5). The GO-associated glacia-tion in southern Africa is correlated with those in North America. Onlythree glacial epochs (the minimum allowable) are needed globally,and all are represented in southern Africa. The basal Duitschlanddiamictite is correlated with the Ramsay Lake and Campbell Lake glaci-ations, the Magkanyene diamictite with the Bruce and lower Vagnerglaciations, and the Rietfontein diamictite with the Gowganda andlower Headquarters glaciations. The correlations are consistent withexisting U–Pb and Re–Os geochronology (Fig. 5).

InWestern Australia, S-isotope evidence (MIF-S and δ34S) tentativelysuggests that the Meteorite Bore glaciation was linked to the GO,and consequently correlative with the middle Duitschland Formation(Williford et al., 2011). Stratigraphic, paleomagnetic and structuralevidences suggest that the Pilbara and Kaapvaal cratonswere connected(Vaalbara hypothesis) between 2.78 and ~2.1 Ga, the former rotatedclockwise 90° and positioned to the northwest of the Kaapvaal cratonin present coordinates (de Kock et al., 2009). Accordingly, thesynvolcanic paleomagnetic pole (located in present Ecuador) obtainedfrom the Ongeluk lavas (Evans et al., 1997) implies that the Pilbaracraton was also located in the tropics during the Makganyene low-latitude glaciation. If the Makganyene and Meteorite Bore glaciationsare correlative by association with the GO (Fig. 5), then the MeteoriteBore glaciation also occurred at low latitude. In the Vaalbara hypothesis(de Kock et al., 2009), it represents a glacial marine facies adjacent to theMakganyene ice sheet. This would make the Meteorite Bore Member ofparticular interest—the only unbroken stratigraphic records of a glacialepoch lie seaward of the maximum ice grounding-lines.

In the absence of direct geochronological, paleomagnetic or atmo-spheric proxy data, the Sariolian glaciation of the Kola–Karelia cratonand the Padlei glaciation of the Hearne craton are not included in theproposed MIF-S-based correlation scheme (Fig. 5).

7. Conclusions

Existing stratigraphic, geochronologic, paleomagnetic and atmo-spheric proxy data are compatible with an alternative global correlationschemewhich unites the GO (Great Oxidation) with a Paleoproterozoicsnowball Earth. The alternative scheme uses the GO, defined here as thedisappearance of MIF-S (mass-independent fractionation of S-isotopesin sulfate and authigenic sulfide minerals), as the primary basis forcorrelation.

In the Eastern Transvaal basin of the Kaapvaal craton (southernAfrica), the GO is associated with a major sequence boundary (MD dis-conformity) in themiddle of the 1.0-km-thick Duitschland/Rooihoogte-Formation. Two glacial horizons occur in the same basin, ~400 m belowthe MD disconformity (basal Duitschland Formation diamictite) and~1000 m above it (Rietfontein diamictite, uppermost Timeball HillFormation). Elsewhere on the Kaapvaal craton, a single glacial sequenceis preserved in the Griqualand West basin. The Makganyene diamictiteis inferred to be the product of a low-latitude (11 ± 5°) ice sheet, basedon a very reliable paleomagnetic pole from the coeval Ongeluk volca-nics. The Makganyene glaciation has been correlated with either theRietfontein or basal Duitschland diamictites, but the latter correlationwould require the GO to be reversed. An alternative interpretation isthat the Makganyene glaciation is expressed in the Eastern Transvaalbasin by the MD disconformity. This correlation potentially unites theGO and low-latitude glaciation, and greatly facilitates correlation withearly Paleoproterozoic successions in North America.

In the Huronian Supergroup of the Superior craton, the GO is mostclosely associated with the second of three discrete glacial intervals,the Bruce Formation. Therefore, the Makganyene-middle Duitschlandglaciation is correlated with the Bruce Formation, allowing the basalDuitschland diamictite to be correlated with the older Huronianglaciation (Ramsay Lake Formation) and the Rietfontein diamictitewith the younger Huronian glaciation (Gowganda Formation). Thethree Huronian glaciations have long been correlated with three in theSnowy Pass Supergroup of the Wyoming craton. In both areas, onlythe second glacial sequence is overlain by a cap-carbonate formation,analagous to those widely found above Cryogenian (Neoproterozoic)panglacial deposits and equivalent surfaces.

In the Turee Creek Group of the Pilbara craton (Western Australia),S-isotope data (MIF-S and δ34S) suggest that the Meteorite Borediamictite was closely associated with the GO, possibly as a glacialmarine facies related to the Makganyene ice sheet in a Vaalbara recon-struction. There is insufficient basis as yet for correlation with theSariolian glaciation(s) on the Kola–Karelia craton (Arctic Europe) orthe Padlei glaciation on the Hearne craton (North America).

The proposed scheme (Fig. 5) needs only three glacial epochs glob-ally, the minimum allowable. All three are represented in southernAfrica. The second was a low-latitude glaciation closely connectedwith the GO. The principal basis for the scheme would be invalidatedif the reappearance of MIF-S is discovered in any basin. The schemecan be falsified by new stratigraphic, geochronological, paleomagneticor atmospheric proxy data. It predicts that the MD disconformity is acryptic glacial erosion surface, subtle evidence of which should exist.The correlation scheme alone provides no explicit reason for glaciationsbefore and after the GO, or for the absence of postglacial cap-carbonateoutside North America. Ongeluk volcanism would have masked anycap-carbonate on the Makganyene diamictite. The proposed correla-tions depart from views informed by decades of universally admiredfield research. They may fail in ways that would not negate the use ofMIF-S as the first criterion for correlating early Paleoproterozoic glacialepochs.

Acknowledgments

The author thanks David Johnston for news of the special issueand Jim Kasting for inviting the article. Nic Beukes and Joe Kirschvink



are thanked for leading memorable field trips to the Makganyene andHotazel formations, and Dawn Sumner for one to the Campbellrandcarbonate platform. David Evans updated the status of Karelianpaleopoles. The University of Johannesburg library is thanked formaking their theses available internationally on-line. Jens Gutzmer,Marcus Kunzmann and Justin Strauss commented on the manuscript,while Nic Beukes and Andrey Bekker provided detailed criticalreviews, for which the author is grateful. None of the above should beheld to account for errors and omissions by a non-partisan neophytein Siderian geology. Support from the Earth System Evolution Projectof the Canadian Institute for Advanced Research (CIFAR) is gratefullyacknowledged.

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