P.F. HOFFMAN
On the kinematics and timing of Rodinia breakup: a possible rift−transform junction of Cryogenian age at the southwest cape of Congo Craton (northwest Namibia)
P.F. Hoffman University of Victoria, School of Earth and Ocean Sciences, Victoria, British Columbia V8P 5C2, Canada Harvard University, Department of Earth and Planetary Sciences, Cambridge, Massachusetts 02138, USA e-mail: [email protected]
© 2021 Geological Society of South Africa. All rights reserved.
Abstract
After tilt correction for Ediacaran thick-skinned folding, a pair of Cryogenian half grabens at the autochthonous southwest cape of Congo Craton (CC) in northwest Namibia restore to different orientations. Toekoms sub-basin trended east-northeast, parallel to Northern Zone (NZ) of Damara belt, and was bounded by a normal-sense growth fault (2 290 m throw) dipping 57° toward CC. Soutput sub-basin trended northwest, oblique to NZ and to north- northwest-trending Kaoko Belt. It was bounded by a growth fault (750 m down-dip throw) dipping steeply (~75°) toward CC. Soutput growth fault could be an oblique (splay) fault connecting a Cryogenian rift zone in NZ with a sinistral transform zone in Kaoko Belt. A transform origin for the Kaoko margin accords with its magma-poor abrupt shelf-to-basin change implying mechanical strength, unlike the magma-rich southern margin where a gradual shelf- to-basin change implies a mechanically weak extended margin. A rift−transform junction is kinematically compatible with observed north-northwest−south-southeast Cryogenian crustal stretching within CC. Post-rift subsidence of the CC carbonate platform varies strongly across the south-facing but not the west-facing shelf. A sheared western CC margin differs from existing Kaoko Belt models that posit orthogonal opening with hyper-extended continental crust. Carbonate-dominated sedimentation over southwest CC implies palaeolatitudes ≤35° between 770 and 600 Ma.
Introduction
There is little consensus on where Congo Craton (CC) was et al., 2003, 2005, 2018, 2020; Poidevin, 2007; Caron, 2010; Monié positioned within Rodinia, or even if it belonged to that et al., 2012; Affaton et al., 2016; Passchier et al., 2016; Oriolo supercontinent at all (Dalziel, 1997; Hoffman, 1997; Pisarevsky et al., 2017; Cailteux and De Putter, 2019; Hoffman et al., 2021). et al., 2003, 2008; Trindade and Macouin, 2007; Li et al., 2008; This implies that surrounding oceanic basins opened and Evans, 2009, 2013; Scotese, 2009; Ernst et al., 2013; Merdith et al., closed, concurrent with the Rodinia-to-Gondwana geotectonic 2017a, b, 2019, 2021; Salminen et al., 2018; Zhou et al., 2018; reorganization. This is easier to account for if CC was part of de Wit et al., 2020; Jing et al., 2020; Wen et al., 2020). Nonetheless, Rodinia than if it was not. CC (Figure 1a) is ringed by late Neoproterozoic ‘miogeoclines’ One reason for CC’s poorly-defined palaeogeographic role (former continental terrace wedges, Dietz and Holden, 1966) is a dearth of palaeomagnetic poles between ca. 748 and 570 Ma that were deformed during Pan-African/Brasiliano aggregation (Meert et al., 1995; Wingate et al., 2004; Moloto-A-Kenguemba of Gondwana (Stanton et al., 1963; Cahen and Lepersonne, 1967; et al., 2008). On this front, I am sad to report the absence of Porada, 1979, 1989; Miller, 1983, 2008b, 2014; Cahen et al., 1984; detectable primary remanence (Shihong Zhang, 2017, personal Stanistreet et al., 1991; Trompette, 1994; Prave, 1996; Goscombe communication) in the 747 ± 2-Ma Upper Naauwpoort
SOUTH AFRICAN JOURNAL OF GEOLOGY 2021 • VOLUME 124.2 PAGE 401-420 • doi:10.25131/sajg.124.0038 401 ON THE KINEMATICS AND TIMING OF RODINIA BREAKUP: A POSSIBLE RIFT−TRANSFORM JUNCTION OF CRYOGENIAN AGE AT THE SOUTHWEST CAPE OF CONGO CRATON (NORTHWEST NAMIBIA)
Formation trachydacite lavas in northwest Namibia (Miller, 1974, The Damara Belt has two branches (Martin, 1983; Miller, 1980b, 2008b; Hoffman et al., 1996). 1983, 2008b), the Northern (NZ) and Southern (SZ) basinal Another reason for CC’s ill-defined role is under-utilization of zones, separated by a Central (CZ) ‘ribbon’ continent aka the epi-cratonic stratigraphic record to infer timing and kinematics Swakop terrane (Figure 1b). In the standard model for Damara of Neoproterozoic rifting and break-up at the margins of the Belt, CZ is an extension of CC and crustal thickening in NZ was craton. Carbonate-dominated epicratonic sedimentation across a consequence of collision with Kalahari Craton in SZ (Barnes southwest CC implies low palaeolatitudes from 770 until 600 Ma and Sawyer, 1980; Kasch, 1983; Stanistreet et al., 1991; Miller, (Halverson et al., 2005), consistent with palaeomagnetic poles for 2008b, Figure 13.291; Goscombe et al., 2018). However, 765 ± 5 Ma (Wingate et al., 2004), 748 ± 6 Ma (Meert et al., 1995; structure−metamorphic geochronology indicates that crustal Mbede et al., 2004) and 571 ± 6 Ma (Moloto-A-Kenguemba et al., thickening in NZ began ≤50 Myr before the collision in SZ 2008). Not all palaeogeographic models adopt the carbonate- (Lehmann et al., 2016). This finding bears out an earlier facies constraint at 600 Ma, although early Ediacaran (Narbonne inference that synorogenic deposits (Mulden Group) on the CC et al., 2012) is the most carbonate-dominated interval across foreland are older than those (Nama Group) on the Kalahari southwest CC (Hedberg, 1979; Miller, 2008b, 2014; Delpomdor foreland (Germs, 1974). If crustal thickening in NZ is not et al., 2016; Cailteux and De Putter, 2019). One model that does attributable to Kalahari collision, then CZ−CC convergence could honour this constraint is de Wit et al. (2020). have been driven by southward subduction in NZ, or back-arc This paper is an attempt to structurally restore sedimentary shortening associated with northward subduction beneath CZ, half grabens, bounded by growth faults of known stratigraphic age, provided it had begun when thickening of NZ occurred. at the southwest corner of CC in northwest Namibia (Figure 1). Radiometric age constraints on crustal thickening can be ‘Growth faults’ are synsedimentary faults on which the throw obtained by dating foredeep deposits and synkinematic increases with depth. Strata of the downthrown side are thicker metamorphism of underthrust epicontinental rocks including than correlative strata on the upthrown side. Downthrown strata stretched continental crust. The onset of such metamorphism generally thicken toward the fault. Orogenic shortening at this gives a minimum age constraint on when continental crust first corner of the craton has previously been discussed (Coward, passed beneath the leading edge of an overthrust plate (e.g., 1981; Maloof, 2000; Clifford, 2008; Lehmann et al., 2016; trench inner wall). Existing radiometric constraints on the onset Passchier et al., 2016; Goscombe et al., 2017, 2018, 2020; of crustal thickening in each basinal zone–NZ, CKZ and SZ Hoffman, 2021), as have aspects of initial rifting (Miller, 1983, (Figure 1b)–are as follows. In widely spaced areas of NZ, 2008b; Porada, 1983; Henry et al., 1990, 1992/93; Stanistreet phengite growth synkinematic with early south-southeast−north- et al., 1991; Stanistreet and Charlesworth, 1999). The goal here northwest shortening yields 40Ar/39Ar laser-ablation plateau ages is to constrain the kinematics and timing of break-up in this of 598 ± 4, 594 ± 7 and 584 ± 4 Ma (Lehmann et al., 2016). From sector of CC. these ages it is inferred that crustal thickening in NZ was The specific area of the growth faults described here was underway by 595 to 600 Ma. In western NZ, D2 folds and systematically mapped and studied by Frets (1969) and lies foliations related to west-southwest−east-northeast crustal within the 1:250,000-scale Fransfontein Sheet 2014 (Schreiber, thickening in Kaoko Belt clearly postdate D1 structures (Coward, 2006). It is situated within the Northern Margin Zone (NMZ) of 1981; Maloof, 2000; Lehmann et al., 2016). the Damara belt, as defined by Miller (2008b), and corresponds In Kaoko Belt itself, metamorphic U-Pb and Sm-Nd mineral to the distal foreslope zone (Hoffman et al., 2021) of the ages east of the Coastal Terrane (CT) range 580 to 540 Ma, with Otavi/Swakop Group, the ca. 770 to 600 Ma carbonate platform 40Ar/39Ar cooling ages down to 520 Ma (Goscombe et al., 2003, covering the southwest CC (Hedberg, 1979; Miller, 1997, 2008b). 2005). The Cambrian ages are broadly coeval with final closure of the Clymene palaeocean bordering Amazonia (Figure 1a) (Tohver Regional tectonic setting et al., 2012; McGee et al., 2015a, b). In CKZ (Figure 1b), metamorphic garnet in pelitic schist of CC affinity (Swakop Group) Southwest CC is bounded to the west and south by the Kaoko has a Sm-Nd isochron age of 574.3 ± 9.7 Ma (Goscombe et al., and Damara belts, respectively (Figure 1). Kaoko Belt is an 2003), while a SHRIMP 207Pb/206Pb zircon mean age of 580 ± 3 Ma oblique sinistral collision zone between western CC and the (Seth et al., 1998) was obtained from an anatectic orthogneiss in Coastal Terrane (CT, Figure 1b) (Guj, 1970; Dürr and Dingeldey, westernmost CKZ (Hoarusib Domain of the Orogen Core of 1996; Goscombe et al., 2003, 2005, 2018; Will et al., 2004; Goscombe and Gray, 2008). These ages imply that crustal Konopásek et al., 2005; Goscombe and Gray, 2007, 2008), which thickening of the western CC margin was underway by 575 to represents the leading edge of the Dom Feliciano−Ribeira 580 Ma, closely following that of the southern (NZ) margin. composite magmatic arc (Figure 1a) (Oyhantçabal et al., 2011; Collision in Southern Zone (SZ, Figure 1b) between Kalahari Chemale et al., 2012; Alves et al., 2013; Konopásek et al., 2016; Craton (lower plate) and Greater Congo (upper plate: CC + CZ Basei et al., 2018; Hueck et al., 2018; Percival et al., 2021). and Dom Feliciano-CT-Ribeira terranes) is radiometrically Whether the basin that lay between CC and CT was a forearc or constrained by foredeep subsidence at 548.8 ± 1 Ma (Grotzinger backarc basin is not agreed upon. The author (Hoffman, 2021) et al., 1995) in the northern (Zaris Sub-basin) Nama Group favours a forearc basin because no record of indigenous arc (Germs and Gresse, 1991; Blanco et al., 2009). As a minimum magmatism (e.g., ‘remnant’ arc, Karig, 1974) is known on the age constraint on collision in SZ, the foredeep age is consistent western CC margin. with pre-collisional arc magmatism at 563 ± 4 Ma (Jacob et al.,
402 SOUTH AFRICAN JOURNAL OF GEOLOGY P.F. HOFFMAN
Kalahari basement and Damara Supergroup cover. Post-orogenic cover includes sedimentary and volcanic rocks (KE) of Karoo Supergroup (Carboniferous−Jurassic) and Etendeka Group (Early Cretaceous), and latest Cretaceous−Cenozoic sediments of Namib and Kalahari Groups (NK). White rectangle at the ‘heel’ of Kamanjab Inlier (CBk) shows the area of Figure 3a.
2000) and 558 ± 5 Ma (de Kock et al., 2000) in Swakop terrane (CZ), and statistically compatible with post-collisional granite emplacement in SZ at 549 ± 11 Ma (Johnson et al., 2006). Accordingly, terminal SZ collision at 550 Ma (D3 hereafter) postdated CC-CT collision in Kaoko belt (D2) by ≥25 to 30 Ma and crustal shortening in NZ (D1) by ≥45 to 50 Ma. D1 shortening in NZ was not simply an intraplate response to D3 collision as conceived in existing Damara Belt models (e.g., Stanistreet et al., 1991; Miller, 2008b; Goscombe et al., 2018). The foregoing does not deny D3 shortening in NZ or southern CC. Both D1 and D3 shortenings likely occurred in southern CC but the D3 deformation is more apparent in the adjacent Kaoko Belt, where D2 structures are orthogonal to D3 (Guj, 1970; Coward, 1981, 1983; Miller, 1983; Hälbich and Freyer, 1985; Maloof, 2000; Passchier et al., 2002; Lehmann et al., 2016; Goscombe et al., 2017). In Epupa Inlier (CBe, Figure 1b), the Figure 1. (a) Southwest Gondwana reconstruction (modified after eastward-plunging cuspate Ombazu syncline (Damara de Wit et al., 2008) relative to Africa, showing Rodinian (pre-900 Ma) Supergroup) is a postulated D3 structure 300 km north of NZ cratons and Pan-African−Brasiliano orogenic belts. The southwest ‘cape’ and 600 km north of the Kalahari margin. Northward subduction of Congo Craton underlay the Otavi Group carbonate platform (770 to of SZ oceanic lithosphere (Barnes and Sawyer, 1980; Sawyer, 600 Ma) and is flanked to the west and south by the 600 to 520 Ma Kaoko 1981; Kasch, 1983; Hoffmann, 1991; de Kock, 1992; Meneghini and Damara orogenic belts, respectively. Abbrevation: São Fr.=São et al., 2014) and consequent high heat-flow under CC (e.g., Francisco Craton; PP=Paranapanema Block. (b) Tectonic elements of Hyndman et al., 2005; Blackwell, 2005) likely accounts for the northwest Namibia (modified after Miller, 2008b). Congo Craton consists wide extent of thick-skinned D3 shortening and associated low- of Rodinian basement inliers (e.g. CBe=Epupa Inlier; CBk=Kamanjab grade (anchizonal) metamorphism of the entire Mulden Group Inlier), folded cover (Cc) of the Damara Supergroup (Figure 2b), and CC foredeep sequence (Figure 2) 400 km from the Kalahari a Northern Margin Zone (NMZ) where the post-rift upper Swakop margin (Clauer and Kröner, 1979). Group (Figure 2c) is a bathyal foreslope facies. Kaoko Belt consists of The extreme southwest corner of CC is occupied by a Coastal terrane (CT) that is the preserved leading edge of a Kamanjab Inlier (CBk, Figure 1b), an antiformal structural Cryogenian−Ediacaran magmatic arc−forearc related to Ribeira and culmination exposing Orosirian CC basement. Except where it Dom Feliciano magmatic arcs (Figure 1a); a central zone (CKZ) of is onlapped by Early Cretaceous basalt (KE, Figure 1b), the inlier middle-late Ediacaran crustal transpression, metamorphism and is bordered by outward-dipping Neoproterozoic cover of the anatexis involving Congo basement and Damara Supergroup cover; and Damara Supergroup (Figure 2). The antiform evolved from a a southern zone (SKZ) in which a folded Cryogenian−Ediacaran pinched forebulge (Hoffman, 2021) into a composite D1−3 deep-sea fan (Zerrissene Group) is intruded by discordant late structure shaped like a human foot (Figure 1b). The ‘shin’ Ediacaran−Cambrian granite bodies. Damara Belt consists of a Northern parallels Kaoko Belt, the ‘forefoot’ parallels NZ and the ‘heel’ Zone (NZ) of northwest-vergent thrusts and folds involving Damara is where the two belts meet. The basement of Kamanjab Supergroup (post-rift basin facies) and little-exposed Congo basement, Inlier includes steeply-plunging folds of metavolcanic and intruded by late Ediacaran−Cambrian syenogranite; a Central Zone (CZ) metasedimentary rocks (Khoabendus Group), intruded by of folded Orosirian and Stenian basement, Damara Supergroup cover, variably deformed intermediate and high-silica granitoids (Frets, a late Ediacaran arc-type diorite-granodiorite suite and Cambrian 1969; Porada, 1974; Miller, 2008a). A flow-banded rhyolite lava syenogranite; and a Southern Zone (SZ) in which a southeast-facing (Smalruggens Formation, Miller, 2008a) at −19.4002°, 14.2910° accretionary prism composed of semipelitic schist with a band of (5.1 km northwest of Kamdescha gate), yielded a zircon amphibolite is thrust onto the SMZ and is intruded by Cambrian 207Pb/206Pb evaporation age of 1987 ± 4 Ma (Seth et al., 1998), syenogranite. Kalahari Craton includes the Rehoboth basement inlier and granitoid emplacement occurred widely at 1.86 to 1.83 Ga (KB, Orosirian−Stratherian and Ectasian−Stenian, Miller, 2012); folded (Kleinhanns et al., 2015). Extensive retrograde metamorphism cover (Kc) of Witvlei Group (Tonian−middle Ediacaran) and Nama of basement rocks is consistent with reheating into the Group (late Ediacaran−Cambrian foredeep); and a Southern Margin quartz-dislocation creep regime during the thick-skinned Zone (SMZ) where southeast-vergent thick-skinned thrust nappes involve Ediacaran deformations.
SOUTH AFRICAN JOURNAL OF GEOLOGY 403 ON THE KINEMATICS AND TIMING OF RODINIA BREAKUP: A POSSIBLE RIFT−TRANSFORM JUNCTION OF CRYOGENIAN AGE AT THE SOUTHWEST CAPE OF CONGO CRATON (NORTHWEST NAMIBIA)
Figure 2. Summary stratigraphic charts for Damara Supergroup of southwest Congo Craton. (a) Timescale in 106 years before present (Ma) with base of Cryogenian Period at 717 Ma (Sturtian snowball onset) and top at 635 Ma (Marinoan snowball termination). Early and late Cryogenian epochs were the Sturtian and Marinoan snowballs, respectively. Grey shading between middle and late Cryogenian reflects age uncertainty of Marinoan onset (646 ± 5 Ma). (b) Platform zone groups (gp), subgroups and formations (Miller, 2008b). Rift-to-drift transition was ca. 650 Ma (base Ombaatjie Formation). Colours are coded by gross lithology (legend at base). Y-axis is time, not thickness. Star 1 is upper Devede Formation tuff dated 760 ± 1 Ma (Halverson et al., 2005, U−Pb zircon ID-TIMS). (c) Southern foreslope zone, or NMZ (Figure 1b) and northern NZ. Rift-to-drift transition was late Cryogenian. Star 2 is Austerlitz Formation ash-flow tuff dated 757 ± 5 Ma (Nascimento et al., 2016, U-Pb zircon SHRIMP) and star 3 is Upper Naauwpoort Formation rhyolite dated 747 ± 2 Ma (Hoffman et al., 1996, U-Pb zircon ID-TIMS). Note prolonged rifting (120 to 130 Myr) and brief drifting (40 to 50 Myr) stages. Synglacial strata are thin relative to snowball durations: average 4.0 m Myr−1 for each (n = 110 Sturtian, n = 157 Marinoan), excluding zero-thickness sections (Partin and Sadler, 2016; Hoffman et al., 2021). During non-snowball times, marine sediment was dominantly carbonate between ca. 770 and ca. 600 Ma.
The large oblate basement-involved D1−3 folding caused dominated Otavi/Swakop Group accumulated during prolonged the older rift-related faults and fault-bounded basins to be north-south crustal stretching (ca. 770 to 640 Ma) and subsequent rotated around subhorizontal axes. The basement structure passive-margin subsidence (640 to 600 Ma). Otavi Group refers (Frets, 1969; Schreiber, 2006) indicates that no large-scale to the 1.5 to 3.5 km thick neritic platform facies and Swakop transcurrent shear or vertical-axis rotations of Ediacaran age Group the distally-tapered southward-facing bathyal foreslope occurred in the area of this study. The Cryogenian rift structures facies in NMZ and the attenuated basin facies in NZ and CKZ were therefore tilt-corrected by rotation round the average strike (Figure 1b) (Frets, 1969; Guj, 1970; Hedberg, 1979; SACS, 1980; of bedding in their immediate area, as described below case by Miller, 1997, 2008b; Clifford, 2008). The Otavi/Swakop Group is case. The fault surfaces, although inferred to be listric at depth, disconformably overlain by synorogenic terrigenous clastic were treated as planes over the limited depth of the rift basins deposits, broadly divisible into older, fully-marine, flysch- (Soutput, 830 m; Toekoms, 2 300 m). like semi-pelite (Kuiseb, Okaua and Sesfontein formations), and younger, coastal to fluvial, molasse-like lithic-arenites Neoproterozoic (Damara Supergroup) stratigraphy (Renosterberg and Tschudi formations). The latter were sourced from the northwest (Hoffman and Halverson, 2008), possibly from Damara Supergroup of CC comprises three groups: Nosib, a southward-younging Kaoko Belt or the Central African Belt on Otavi/Swakop and Mulden in ascending order (Figure 2). Nosib the northern CC margin (Kamguia Kamani et al., 2021). Group is a southeastward-tapered sheet-like body of basement- The flysch-like Kuiseb Formation has long been included in derived conglomerate and pebbly subarkose (Kröner and Correia, Swakop Group (Figure 2c) (SACS, 1980), but in terms of age 1980), deposited by southward-flowing rivers in an unknown (Halverson et al., 2005), lithology (terrigenous vs carbonate) and tectonic regime. It is not preserved in the NMZ. The carbonate- tectonic setting (trench/foredeep versus passive margin) it has
404 SOUTH AFRICAN JOURNAL OF GEOLOGY P.F. HOFFMAN
more in common with the Mulden Group. Kuiseb Formation was Karoo Supergroup and the sub-Karoo (Carboniferous) glacial grouped with underlying strata because an angular unconformity surface (Wanke et al., 2000). To the east, the Swakop Group (Frets, 1969) separates it from Welkom Subgroup (Figure 2c), panel is erosionally truncated by Damaran foredeep clastics of whereas its contact with Karibib Formation is a parallel Mulden Group (Frets, 1969; Hoffman, 2021). The panel is disconformity. This is in the nature of dynamic foredeeps, which divided into western and eastern segments by a 7 km long gap are asymmetric troughs at convergent collisional plate boundaries where only slivers of Swakop Group are preserved between that migrate with time toward the subducting continental plate allochthonous and autochthonous basement rocks. The focus of (e.g., Persian Gulf, Taiwan Strait, Timor Sea). On their outer slopes, this paper is the segment east of the gap, on farms Toekoms foredeep strata paraconformably overlie passive-margin strata, 508, Bethanis 514 and Austerlitz 515 (Figure 4). separated by a short-lived disconformity related to forebulge The eastern segment of the Swakop Group panel features migration. On their actively deforming inner slopes, unconformities three sub-basins (Figure 3) of successively younger age from east develop continuously once the accretionary prism is emergent and to west. Toekoms sub-basin is mainly early Cryogenian, Soutput subject to subaerial erosion. Foredeep migration dictates that outer sub-basin is mainly middle Cryogenian and Bethanis sub-basin slopes become inner slopes over time, with the result that angular is late Cryogenian (Figure 3b). Toekoms and Soutput sub-basins unconformities appear well after initial foredeep subsidence and are half grabens (aka hangingwall basins) that deepen toward sedimentation at any given location. Detrital zircon age spectra bounding growth faults. Bethanis sub-basin has similar wedge- from Kuiseb Formation are systematically different from older shape geometry, but if a growth fault existed it was carried away Swakop Group detritus (Nascimento et al., 2017; Hoffman and by the NZ boundary thrust (Bethanis thrust, Figure 4). Halverson, 2018). To which group Kuiseb Formation nominally The Soutput and Toekoms growth faults are discordant with belongs is not for me to decide. respect to the gneissic basement structure (Frets, 1969; Schreiber, Two global Cryogenian glaciations (Rooney et al., 2015; Zhou 2006). Their orientations do not appear to be inherited from et al., 2019) and/or their postglacial cap-carbonate sequences basement structure. The two growth faults map out differently (Kennedy et al., 1998; Hoffman and Schrag, 2002) are in the low-relief (≤90 m) topography. Soutput fault is relatively recognizable in all facies zones and enable the Otavi/Swakop straight and its strike is 345°. Just 2 km to the east, Toekoms Group to be divided into three subgroups and five epochs fault has a highly sinuous trace and its overall strike is 300° (Figure 2) (Hoffmann and Prave, 1996; Hoffman and Halverson, (Figure 4). The basement is more resistant to erosion than the 2008; Hoffman et al., 2021). Early Cryogenian (‘Sturtian’) glacial- sedimentary cover, so where they are juxtaposed the fault trace periglacial deposits belong to Chuos Formation and late controls the topography rather than the other way around. The Cryogenian (‘Marinoan’) glacial-periglacial deposits to Ghaub simplest explanation of the map pattern is that both faults are Formation. Chuos Formation diamictites are polymictic, reflecting gently warped but Soutput fault is subvertical and Toekoms fault heterogeneous source rocks in a synglacial crustal-stretching has a shallow dip. A strongly folded Toekoms fault can be ruled regime having ‘basin-and-range’ palaeotopography (Hoffman out because such folding is not observed in the adjacent Swakop et al., 2017). Ghaub Formation diamictites are oligomictic, derived Group or Soutput fault (Figure 4). from immediately preglacial carbonate source rocks in a broadly- subsiding passive-margin regime (Domack and Hoffman, 2011; Toekoms sub-basin Hoffman, 2011). Post-snowball cap-carbonate sequences are the Sturtian Berg Aukas/Rasthof Formation (Yoshioka et al., 2003; Toekoms sub-basin (Figure 5) has been described previously Pruss et al., 2010; Dalton et al., 2013; Le Ber et al., 2013; Le Heron (McGee et al., 2012; Hoffman et al., 2017, 2021) and the details et al., 2020) and Marinoan lower Karibib/Maieberg Formation need not be repeated here. Differential subsidence of the (Higgins and Schrag, 2003; Hurtgen et al., 2006; Hoffman et al., hangingwall of Toekoms growth fault began in late Tonian 2007; Hoffman and Halverson, 2008; Kasemann et al., 2010; time and ended before the Sturtian deglaciation. Minimum Hoffman, 2011; Ahm et al., 2019; Hoffman and Lamothe, 2019). subsidence (no upthrown strata preserved) before and during Global synchroneity of Cryogenian glacial onsets and terminations Sturtian glaciation was 650 and 1 640 m, respectively. In the allows the Chuos Formation to be bracketed between 717 basin, wedges of conglomerate and redeposited diamictite and 661 Ma, and the Ghaub Formation between 646 ± 5 and thicken toward the growth fault. More distal deposits are 635.5 ± 0.5 Ma (Rooney et al., 2015, 2020; Macdonald et al., dominated by flat-laminated argillite with turbidites of siltstone 2018; MacLennan et al., 2018; Zhou et al., 2019; Lan et al., 2020; or sandstone. Ice-rafted lonestones of basement and Tonian Nelson et al., 2020). sedimentary rocks occur sparingly in fine-grained host rocks throughout the basinal sequence (noted at 73 horizons in A sub-basin relay sections 28 to 34 combined, Figure 5). Within the sub-basin, diamictite is subordinate to siltstone + argillite in Chuos The ‘heel’ of Kamanjab Inlier (Figure 3) is rimmed by an Formation, 24% to 44%, whereas outside the sub-basin diamictite outward-dipping arcuate panel of autochthonous foreslope- is more abundant, 74% to 15%. In the surrounding area, the facies Swakop Group. The panel has an exposed strike length Chuos Formation appears to be mainly of terrestrial facies. of 40 km. To the northwest it disappears beneath flat-lying Massive diamictite makes up 52% of its aggregate thickness aeolianite and volcanic rocks of the Early Cretaceous Etendeka (23.2 km) in 94 measured sections–stratified diamictite totals less Group (Jerram et al., 1999, 2000; Miller, 2008c), which onlap than 3% (Hoffman et al., 2021). In Toekoms sub-basin,
SOUTH AFRICAN JOURNAL OF GEOLOGY 405 ON THE KINEMATICS AND TIMING OF RODINIA BREAKUP: A POSSIBLE RIFT−TRANSFORM JUNCTION OF CRYOGENIAN AGE AT THE SOUTHWEST CAPE OF CONGO CRATON (NORTHWEST NAMIBIA)
Figure 3. (a) Geological map of the southwest cape of Congo Craton (white rectangle in Figure 1b) highlighting the Neoproterozoic Damara Supergroup (Figure 2c). Abbreviations: NMZ, Northern Margin Zone; NZ, Northern Zone of Damara Belt (Miller, 2008b); TF, Toekoms growth fault. (b) Generalized stratigraphic section of the autochthonous (NMZ) Damara Supergroup panel in (a) showing the westward-younging Toekoms, Soutput and Bethanis sub-basins and associated growth faults. Vertical bars are measured sections numbered as in Figures 4 to 6. Numbered divisions in Toekoms sub-basin are stratigraphic divisions as in Figure 5. Inset gives allochthonous sections in thrust sheet B (Figure 4) at the same scale.
traction-current structures are conspicuously absent, prompting Soutput sub-basin speculation in view of the surrounding terrestrial glacial facies that it was a subglacial lake or fjord (Hoffman et al., 2017). Differential subsidence (hangingwall minus footwall thickness) Unit 4 in Toekoms sub-basin (Figure 5) is enriched in hematite on Souput growth fault (Figure 6) began in Sturtian time (138 m cement, as are other Chuos Formation sub-basins in CC (Martin, in ≤56 Myr), peaked during the inter-snowball epoch (520 m in 1965a, b; Le Heron et al., 2013; Lechte et al., 2018, 2019). It is 10 to 20 Myr), and ended in Marinoan time (90 m in ≤6 to 16 Myr) uncertain if the source of iron in Toekoms sub-basin was the before the major upper Ghaub Formation diamictite was ferruginous snowball ocean (Lechte et al., 2018, 2019) or deposited. Principal beneficiaries of the local accommodation ferruginous subglacial meltwater (e.g., Mikucki et al., 2009; Gao were nonglacial limestone turbidites of Okonguarri Formation and et al., 2019). silt-laminated argillite of Narachaams Formation. The eo-Marinoan falling-stand wedge (Frannis-aus Formation) does not thicken toward Soutput growth fault, consistent with rapid deposition,
406 SOUTH AFRICAN JOURNAL OF GEOLOGY P.F. HOFFMAN
and slow and/or intermittent slip on the fault. The history of section, 15 (Figure 6), which is 30% greater than its maximum differential subsidence indicates that displacement on Soutput thickness in Soutput sub-basin. It is 5.5 times thicker than the growth fault overlapped in time with Toekoms and Bethanis sub- Ghaub Formation average thickness (n = 25) in the panel as a basins, but was fastest when the other basins were inactive. whole, and 100 m thicker than the underlying early and middle Cryogenian section of ≥4 times longer duration (Figure 3b). Bethanis sub-basin Tilt-correcting Toekoms and Soutput sub-basins Differential subsidence of Bethanis sub-basin began in Marinoan time (Figure 6) but when it ended is uncertain because of The autochthonous basement surface dips southeast under progressive top-down erosion due to the eastward plunge of Toekoms sub-basin and south-southwest under Soutput basin the syncline in which the sub-basin is preserved (Figure 4). The (Figure 4). The average strike/dip (right-hand rule) of bedding Ghaub Formation is 230 m thick in the westernmost complete in Toekoms sub-basin (Figure 8) is 040/46° (n = 46, pole pTB(f)
Figure 4. Simplified geology on parts of Bethanis, Toekoms and Austerlitz farms, showing locations of measured sections 13−34 (Figures 3b, 5 and 6). Structural units: A, Orosirian basement (Kamanjab Inlier) and autochthonous cover; B, thrust sheet carrying basement and Swakop Group similar to unit A; C, thrust sheet carrying Karibib and Kuiseb formations similar to unit A (Hoffman and Halverson, 2018); D, Bethanis thrust sheet (leading edge of NZ) carrying basement and Swakop Group stratigraphically distinct from units A−C (e.g. Tonian is expanded and late Cryogenian−early Ediacaran strata are missing). Alternatively, ‘Kuiseb Fm’ schist in unit D is middle Cryogenian (Nascimento et al., 2016, 2017), which is problematic if Kuiseb Formation depositionally overlies Karibib Formation in Vrede domes (Figure 3a) (Hoffman et al., 2017).
SOUTH AFRICAN JOURNAL OF GEOLOGY 407 ON THE KINEMATICS AND TIMING OF RODINIA BREAKUP: A POSSIBLE RIFT−TRANSFORM JUNCTION OF CRYOGENIAN AGE AT THE SOUTHWEST CAPE OF CONGO CRATON (NORTHWEST NAMIBIA)
shown on inset map (lower right)shown and Figure 4. Unit 1 (blue number) to distal (unit 4) wrt Toekoms growth fault is characteristic of Mesozoic rift is characteristic growth fault to distal (unit 4) wrt Toekoms ted lonestones and turbidites of silt- and sandstone. Wave and traction-current ted lonestones and turbidites of silt- sandstone. Wave
fjord. Unit 1 and proximal unit 3 are dominated by basement-derived conglomerate. lip on Toekoms growth fault ceased before deposition of middle Cryogenian growth fault limestone lip on Toekoms , 1995). Late Tonian(?)−early Cryogenian columnar sections in Toekoms sub-basin (modified after Hoffman et al., 2017). Section locations sub-basin (modified Cryogenian columnar sections in Toekoms Late Tonian(?)−early
5. Figure is provisionally pre-Sturtian in a Sturtian and units 2−5 belong to Chuos Formation, deposited subaqueously subglacial lake or Units 2 and 5 are dominated by resedimented diamictite. Unit 4 and distal units 2 3 are dominated by argillite with ice-raf bedforms are absent in units 2−5. Lateral persistence of thin unit 5 diamictite implies a non-erosive top of Chuos Formation. S turbidites of Berg Aukas and/or Okonguarri Secular shift in maximum accumulation from formations (green). proximal (units 1−2) Northbasins formed on the above listric Atlantic continental margins growth faults (e.g., Petrie et al., 1989; Driscoll et al.
408 SOUTH AFRICAN JOURNAL OF GEOLOGY P.F. HOFFMAN
in Figure 7a). The sub-basin was tilt-corrected by restoring the basement strike of 110° would restore the fault plane to an initial dipping strata to horizontal (pole pTB(i)) by rotation around steep westerly dip. This would imply that Soutput sub-basin was their average strike of 040° (Figure 7a). a footwall basin beneath an eastward-directed Cryogenian thrust Toekoms growth fault has a highly sinuous map trace fault. The dimensions of the basin, 2.3 km wide by 600 m deep (Figure 8) implying a shallow dip beneath the sub-basin. Its (sections 22 to 24, Figure 6), require a 15° kink in the basement overall strike is 300°. If we assume the fault plane dips 30° under surface, for which the only stratigraphic expression other than the sub-basin at present (pole pTF(f) in Figure 7a), tilt correction stratal thickening is the apparent removal of the 4.4 m thick Berg as above restores the fault plane to an original strike/dip of Aukas Formation in sections 23 to 34 (Figures 5 and 6). In the 255/57° (pole pTF(i)), and a dip direction of 345°. This tilt- absence of other evidence for Cryogenian compressional corrected fault plane is consistent with a cratonward-dipping tectonics in western CC (Figure 1b), the preferred restoration of normal fault striking parallel to NZ (Figure 1b), compatible with Soutput fault involves tilt correction for the broader average an earlier NZ ‘detachment’ model (Henry et al., 1990; Bosworth, strike/dip of the basement surface. As inferred from the Berg 1985). In northern NZ (southeast Summas Mountains dome), a Aukas Formation (Figure 6), the basement surface in sections late Cryogenian rift-related structural rotation documented 14 to 19 and 27 to 34 (Figure 4) has an average strike/dip of stratigraphically (Hoffman et al., 2018, 2021) implies a southward 062/48° (n = 10). This is the tilt correction, pSB(f) to pSB(i), dipping fault plane (Macaria sub-basin, Figure 9). used in Figure 7b. If we assume a final strike/dip for Soutput The basement dips south-southwest under Soutput sub- fault (pSF(f)) of 345/80°, then its initial strike/dip was 333/74° basin (Figure 4), but this is a local trend that deviates from the (pSF(i), Figure 7b). This fault-plane restoration is not very regional strike of the basement surface between sections 14 to sensitive to the assumed final dip so long as it is steep (≥60°), 34. Tilt-correcting Soutput fault by rotation around the local as implied by its map trace (Figure 4).
Figure 6. Cryogenian columnar sections from the autochthonous panel of Bethanis and Soutput sub-basins (Hoffman et al., 2021). See Figure 4 for section locations. Note thickening of Chuos (Ac), Berg Aukas (Aa), Okonguarri (Ao), Narachaams (An) and lower Ghaub (Tg) formations toward Soutput growth fault, indicating fault displacement from late Sturtian through early Marinoan time. Displacement apparently ceased before deposition of upper Ghaub Formation massive carbonate diamictite. Not shown is the early Ediacaran Karibib Formation (328 m in section 1-19, Figure 3b) consisting of post-rift foreslope dolomite turbidites and debrites.
SOUTH AFRICAN JOURNAL OF GEOLOGY 409 ON THE KINEMATICS AND TIMING OF RODINIA BREAKUP: A POSSIBLE RIFT−TRANSFORM JUNCTION OF CRYOGENIAN AGE AT THE SOUTHWEST CAPE OF CONGO CRATON (NORTHWEST NAMIBIA)
Figure 7. Lower hemisphere stereonets illustrating tilt-corrections of growth faults for thick-skinned rotation of the basement surface and cover during orogenic crustal shortening. Fault planes are assumed to be planar for simplicity. (a) Tilt-correction for Toekoms sub-basin through back-rotation of average pole to bedding (pTB(f), strike/dip with right-hand rule, 040/46°, n = 46) to the horizontal (pTB(i)), and co-rotation of Toekoms growth fault (pTF(f)) to its inferred original orientation (pTF(i)) of 255/57° (strike/dip). Because final (f) growth-fault dip is uncertain, dips of 10, 20, 30, 40 and 50° are shown (purple dots) with preferred dip (30°) indicated by blue back-rotation arrow. Purple circles are respective back-rotated poles. Restored growth fault (pTF(i)) strikes parallel to NZ and dips toward CC at a reasonable failure angle of 57° (i.e. 28.5° wrt vertical). (b) Tilt correction for Soutput sub- basin through back-rotation of the average pole (pSB(f), 062/48°, n = 10) to the basement surface in sections 1-15−19 and 1-27−34 (Figure 4). Co-rotation of poles to Soutput growth fault (pSF(f)) restores fault plane to strike/dip of 333/74° (pSF(i)), assuming preferred final dip of 80° toward east-northeast (blue arrow). Poles for final fault dips of 90, 80 and 70° to east-northeast and west-southwest also shown (purple dots), along with their respective back- rotated poles (purple circles). Preferred growth-fault restoration (pSF(i)) strikes 333°, oblique to CKZ (Figure 1b) and dips steeply (74°) toward CC.
Figure 8. Geological map around Toekoms growth fault (TF), illustrating its sinuous trace and inferred warped shallow dip (Hoffman et al., 2021). Sedimentary strata are buttressed by the footwall basement (Huab Gneiss). Toekoms growth fault is overstepped (lower right) by Okonguarri Formation limestone turbidites and possibly by Chuos Formation unit 5 diamictite. Location of 56-m-wide basement olistolith (glacial erratic?) in section 1-28 (Figure 5) is indicated in drainage (green) near base of Chuos Formation unit 2. Area is accessible from the N through Boesmanspan and Toekoms pos (Figure 3a).
410 SOUTH AFRICAN JOURNAL OF GEOLOGY P.F. HOFFMAN
Figure 9. Schematic cross-section of crust and uppermost mantle at south-southeast-facing margin of CC in early Ediacaran time, showing buried seaward-dipping Huab and Makalani growth faults under the outer platform, and landward-dipping Toekoms growth fault under the distal foreslope (NMZ). Rift-to-drift transition migrate seaward from middle Cryogenian under the outer platform to late Cryogenian in NZ (Hoffman et al., 2018). Antithetic (continentward-dipping) seaward-younging growth faults occur also on the Mesozoic offshore margin of southwest Africa (Aizawa et al., 2000; McDermott et al., 2015; Clerc et al., 2018; Sapin et al., 2021).
Discussion faults (‘horsetail’ splays) during fault propagation (e.g., Perrin et al., 2016). Such faults can develop into curvilinear forms The tilt-corrected 255° strike of Toekoms growth fault that mechanically couple rift and transform displacement (Figure 7a) is parallel to NZ (Figure 1), and its cratonward dip (Figure 10b). Rift faults of this type should steepen and undergo of 57° is consistent with Coulomb failure for a normal fault. It is more oblique slip as their strike curves toward the transform antithetic to the basinward-dipping Huab and Makalani growth (small circle) orientation. In this model, the oblique orientation faults under the outer (southern) part of the Otavi Group and steep dip of Soutput growth fault are mutually consistent. carbonate platform (Hoffman and Halverson, 2008; Hoffman Connecting splay faults at rift-transform junctions are et al., 2021). The change from basinward-dipping normal faults observed in analogue models and in active fault systems such under the shelf to cratonward-dipping normal faults under the as the Theistareykir Rift Zone in northern Iceland (Figure 10a) foreslope (Figure 9) is analogous to fault patterns observed by (Tibaldi et al., 2016; Khodayar et al., 2018; Rust and Whitworth, seismic reflection on the South Atlantic rifted margins of volcanic 2019). The Icelandic example is instructive because of the northern Namibia and non-volcanic southern Angola (Aizawa relatively isotropic nature of the basaltic country rock. Oblique et al., 2000; McDermott et al., 2015; Clerc et al., 2018; see also faults are also observed at former rift−transform junctions Bosworth, 1985). A return to seaward-dipping faults beyond the preserved on continental margins, such a Galicia Bank in foreslope (Macaria subbasin, Figure 9) has been observed in northwest Spain (Roberts and Kidd, 1984; Boillot et al., 1989) Lüderitz Basin of offshore Namibia but not Walvis Basin and at both ends of the Agulhus−Malvinas transform fault zone (McDermott et al., 2015). in the southern South Atlantic (Figure 10c). In these cases, The tilt-corrected 333° strike of Soutput growth fault is however, the mechanical significance of fault orientation is oblique to Kaoko Belt and to NZ. Its dip of 74° (Figure 7b) is compromised by structural inheritance from anisostropic upper steeper than Coulomb failure angles (~60°) for normal faults. crust. Oblique (west−east) Mesozoic faults at the Cape of South Oblique faults occur on continental margins that opened by Africa (McMillan et al., 1997) are largely inherited from older oblique rifting, as in the Gulf of Aden (Fantozzi and Sgavetti, Cape Fold Belt structures (de Wit and Ransome, 1992; Paton and 1998). However, the west-northwest−east-southeast rift faults Underhill, 2004). Oblique (west-northwest−east-southeast) rift observed on the Gulf of Aden margins are parallel to those in basins of Cretaceous age on Malvinas (Falkland) Plateau may the Red Sea Rift. On average, both are oriented normal to the be inherited from older Mesozoic Andean backarc basins (Uliana Africa–Arabia plate motion vector. This is inconsistent with the et al., 1989). Oblique faults on Galicia Bank may be reactivated cape of Congo Craton where the initial strikes of Soutput and late Hercynian basement faults (Arthaud and Matte, 1975; Toekoms faults differ by 78° (333 to 255°). Oblique opening of Maestro et al., 2018). Moreover, each of the fault systems referred southwest Congo Craton is not supported by this disparity, but to in Iceland, Namibia, Spain and South Africa is larger in scale neither is it denied given the zig-zag fault plans of oblique rift by a factor of ten in the order given. basins (e.g., Morley, 2017). Oblique opening (Fantozzi and Is a rift-transform junction at the southwest cape of CC Sgavetti, 1998) is not consistent with the NZ-parallel strike of consistent with other differences between the south-facing and Toekoms growth fault. west-facing CC margins? Pre-Sturtian rift-related volcanic centres If, however, the western CC margin originated as a sinistral are prodigious along the southern but not the western margin. transform fault system, kinematically linked to a nascent On the southern margin, 760 to 746 Ma volcanic centres occur NZ orthogonal rift system (Figure 10d), then oblique from west to east on the farms Austerlitz 515 (Nascimento et al., northwest−southeast faults would be predicted as splay 2016), Naauwpoort 511 (Frets, 1969) and Oas 486 (Hoffman et al.,
SOUTH AFRICAN JOURNAL OF GEOLOGY 411 ON THE KINEMATICS AND TIMING OF RODINIA BREAKUP: A POSSIBLE RIFT−TRANSFORM JUNCTION OF CRYOGENIAN AGE AT THE SOUTHWEST CAPE OF CONGO CRATON (NORTHWEST NAMIBIA)
1996); in the structural inliers of Ais Dome, Mitten Fold and Huab and Makalani rift-shoulder geometry (Figure 9) (Hoffman Summas Mountains (Miller, 1974, 1980, 2008b; Hoffman et al., and Halverson, 2008; Hoffman et al., 2021). No post-rift Swakop 1996), and in the ranges south of Otavi Syncline (Kombat Suid Group foreslope analogous to that of the NMZ (Figure 9) has Formation of Smit, 1962; Askevold Formation of SACS, 1980). been documented on the western margin. The early Ediacaran Some of these centres erupted enormous volumes (≥103 km3) of Tsumeb Subgroup (Figure 2b) is still in a cyclic peritidal felsic magma (Miller, 2008b). In contrast, rift-related igneous rocks carbonate facies in the footwall of the CKZ boundary thrust are rare on the western margin (Schermerhorn, 1961; Guj, 1970, (Sesfontein thrust) at latitude −18.5° (Hoffman et al., 2018). Yet 1974), limited to amphibolite bodies near the base of the Swakop the correlative strata in CKZ are described as ‘metagreywacke’ Group and in the youngest pre-Sturtian formation (Okovikuti (Konopásek et al., 2017) and in SKZ (Figure 1b) the correlative Formation) of Tsonguari syncline in Central Kaoko zone (Henry carbonate−greywacke turbidite unit of equal duration (Gemsbok et al., 1992/93; Stanistreet and Charlesworth, 1999). Amphibolites River Formation) is decimated in thickness (233 versus 2050 m) near the base yielded zircons having 206Pb/207Pb LA-ICP-MS compared with westernmost CC (Hoffman and Lamothe, 2019). concordia ages of 730 to 740 Ma (Konopásek et al., 2014). If a post-rift western shelf-break and upper foreslope existed, it A transform origin for the western CC margin is was either cut-out by the Sesfontein thrust or eroded from the kinematically consistent with north-northwest−south-southeast eastern CKZ, which mainly exposes deeper stratigraphic levels crustal-stretching inferred from stratigraphic offlap-onlap (Guj, 1970; Konopásek et al., 2017). relations, clastic wedges and palaeocurrent directions related to
Figure 10. (a) Detailed fault map, based on surface ruptures, at a rift−transform junction in the north of Iceland (Tibaldi et al., 2016). Heavy and light lines are traces of major and minor faults, with ticks indicating down-dropped side. Blue and green colours denote rift- and transform-parallel faults, respectively. Magenta colour identifies a set of oblique faults interpreted as extensional splay faults (Figure 10b), as are observed in scaled analogue models at the tips of transcurrent faults (green). (b) Schematic model of an extensional imbricate fan at a rift−transform junction (Tibaldi et al., 2016). Fault plane dipping north-northwest (note southward-looking perspective) at location T (Toekoms sub-basin) bends through steep northeast dips at location S (Soutput sub-basin) into a north-northwest-trending sinistral transform at location K (CKZ, Figure 1b). (c) Mesozoic rift basins (chartreuse) and growth faults on the southwest cape of South Africa (McMillan et al., 1997; Wildman et al., 2015), associated with junction of South Atlantic rift and Falkland−Agulhas Fracture Zone. Faults are colour-coded as in Figure 10a, with magenta faults forming a set oblique to the rift (blue) and transform (green) faults. Abbreviations: AB=Algoa Basin; BB=Bredasdorp Basin; CT=Cape Town; OB=Oudtshorn Basin (de Wit et al., 2020). Oblique normal faults are compatible with a resolved component of dextral shear parallel Agulhas transform (inset strain ellipse, upper right). Note difference in scale compared with area in Figure 10a. (d) Schematic map of southwest Congo Craton (CC) as a Cryogenian rift−transform junction, with Makalani, Huab, Toekoms and Macaria rift faults parallel to Northern Zone (NZ), and steeply-dipping Soutput fault as an oblique splay fault from a sinistral transform fault system in Central Kaoko Zone (CKZ). Toekoms growth fault dips cratonward, while Makalani, Huab and Macaria growth faults dip seaward.
412 SOUTH AFRICAN JOURNAL OF GEOLOGY P.F. HOFFMAN
The post-rift carbonate succession on the platform (Figure 2b) undergoes large changes in thickness normal to the south-southeast-facing rifted margin (Figure 11a), but more muted changes normal to the west-southwest-facing margin (Figure 11b). The arched pattern of subsidence in the NZ-normal section (Figure 11a), cresting 90 to 100 km inboard from the shelf break (Figure 1b), suggests a flexural component of passive-margin subsidence (Watts et al., 1982), perhaps related to volcanic loading in NZ. The section normal to Kaoko Belt (Figure 11b) is limited to the east by Cenozoic cover (Figure 1b), but the muted gradient in thickness is consistent with a transform margin that underwent little stretching, but ephemeral heating, diffused from a migrating spreading-ridge tip (Figure 10c). A transform origin for the western margin of CC is a departure from earlier kinematic models that invoke orthogonal rifting (e.g., Porada et al., 1983; Porada, 1989; Stanistreet et al., 1991; Konopásek et al., 2018). If the Adamastor palaeocean (Hartnady et al., 1985) was floored by hyper-extended Figure 11. Lateral variation in stratigraphic thickness of post-rift Otavi continental crust (Konopásek et al., 2020), the extension Group formations (Figure 2b) in directions (a) normal to NZ and the direction would have been parallel to Kaoko Belt in the south-southeast-facing rifted margin of CC (Figure 9), and (b) normal transform model, rather than orthogonal as previously inferred. to CKZ (Figure 1b) and the west-southwest-facing CC margin. The transform model predicts large southward translations Abbreviations: Ab=Ombaatjie Formation; Tm=Maieberg Formation; Te= of crustal blocks within the Kaoko Belt. The Southern Kaoko Elandshoek Formation; Th=Hüttenberg Formation. Coordinates are Zone (SKZ, Figure 1b) is a potential example. The Zerrissene approximate section locations (see Figure 1b). The arched subsidence Group (Swart, 1992a, 1992b) is a Damara-age deep-sea fan with pattern in (a) suggests a flexural component of passive-margin a remarkably uniform detrital zircon age frequency distribution subsidence (Watts et al., 1982), possibly related to volcanic loading in (Nieminski et al., 2018) that is most similar to that found in NZ (Figure 9). Weak and reversing lateral subsidence variability in (b) correlative strata on the western CC margin 1 900 km to the is consistent with a strong, non-volcanic (transform) type margin north, in the equatorial West Congo Belt (Frimmel et al., 2006). (Sapin et al., 2021). The shearing off of Madagascar from Somalia (Sapin et al., 2021) is a Mesozoic analogue of comparable (1 500 km) scale. Whatever rifted off the southern CC margin should not have After CZ collided with CC around 600 Ma (NZ D1 deformation travelled far, given only 40 Myr between breakup (640 Ma) and of Lehmann et al., 2016), subduction polarity flipped and SZ closure (600 Ma) on the southern CC margin (Figure 2c) and contracted via northward subduction leading to terminal 90 Myr (640 to 550 Ma) for the Damara ocean as a whole. The NZ collision with Kalahari Craton around 550 Ma (Figure 12e basin was evidently wide enough to host a gyre by the end of and f). Meanwhile, subduction-accretion in the Ribeira-Dom the Cryogenian (635 Ma) because westward-directed contourites Feliciano forearc resulted in diachronous southward younging occur in Marinoan syndeglacial marine drifts (Bethanis Member collision in Kaoko and Gariep belts (Figures 12e and f). Coeval of Ghaub Formation) on the foreslope (NMZ) south of westward and southward subduction at the southwest cape of Kamanjab Inlier (Figure 1b) (Hoffman, 2011). A central Atlantic- Congo Craton is postulated to account for amplified forebulge type spreading rate of 5 cm/yr would allow a 1 000 km wide uplift in ‘Huab cusp’ (Figure 12e) (Hoffman, 2021). basin to open and close again in 40 Myr. The most conservative candidate as the rifted conjugate to CC is CZ (Figure 1b) (e.g. Conclusions Henry et al., 1990). Given evidence from the 1.1-Ga Umkondo large igneous province for a Congo-Kalahari connection before Tilt correcting for thick-skinned folding restores adjacent early Damaran breakup (Ernst et al., 2013; Salminen et al., 2018), the and middle Cryogenian half grabens at the southwest cape of simplest way to remove CZ from CC is as part of the Kalahari Congo Craton to different pre-fold orientations. Toekoms growth plate (Figure 12a and b). During the brief window of fault (2290 m throw) paralleled Northern Zone of Damara Belt opportunity for subduction initiation at a rifted continental and dipped north-northwest ~57° toward the craton. Soutput margin–when the oceanic lithosphere is sufficiently old to sink growth fault (750 m down-dip throw) had an oblique northwest but sufficiently young to be ruptured–subduction began at the strike and dipped ~74° toward the craton. The oblique (333°) trailing edge of CZ, leading to backarc separation from Kalahari strike and steep dip of Soutput fault are consistent with a splay Craton (Figure 12c and d). In this ‘micro-Tethyan’ model fault connecting an orthogonal rift zone in Northern Zone with (Hoffman et al., 2021), southward-directed subduction beneath a sinistral transcurrent fault system in Central Kaoko Zone. CZ led to its return to CC by subduction roll-back, with SZ A transform origin for the western margin of Congo Craton is opening between CZ and Kalahari Craton (Figure 12d and e). consistent with a paucity of rift-related volcanism in Kaoko and
SOUTH AFRICAN JOURNAL OF GEOLOGY 413 ON THE KINEMATICS AND TIMING OF RODINIA BREAKUP: A POSSIBLE RIFT−TRANSFORM JUNCTION OF CRYOGENIAN AGE AT THE SOUTHWEST CAPE OF CONGO CRATON (NORTHWEST NAMIBIA)
Figure 12. Plate-scale cartoon of Pan-African tectonics in the Damara and Kaoko−Gariep belts of southwest Gondwana (Figure 1), assuming a Cryogenian rift−transform junction at the southwest corner of Congo Craton. Abbreviations (Figure 1b): A=Adamastor ocean; CC=Congo Craton; CZ= Central Zone; G=Gariep Belt; K=Kaoko Belt; KC=Kalahari Craton; NZ=Northern Zone; SZ=Southern Zone. (a) Incipient breakup along two rift zones (dashed) connected by a shear zone (solid). (b) Orthogonal opening of NZ (Outjo) basin and shear opening of the western Cc margin by sinistral transform (small circle) motion. (c) Subduction initiation at the southern margin of NZ basin. (d) Subduction rollback pulls CZ (Swakop terrane) away from Kalahari Craton, opening SZ (Khomas) as a backarc basin. (e) Collision of CZ forearc with southern Congo rifted margin, broadly coeval with oblique collision of Ribeira−Coastal−Dom Feliciano forearc with the western Congo transform margin. Constriction of the subduction cusp produced an amplified forebulge in ‘Huab cusp’ (Hoffman, 2021). (f) Closure of SZ basin and collision of Kalahari Craton with the amalgamated CZ, Congo Craton and Kaoko Belt. Closure of Adamaster ocean progresses southward along the western Kalahari sheared margin forming the Gariep Belt (e.g., Hälbich and Alchin, 1995; Gresse, 1995).
West Congo belts, and abrupt post-rift shelf-to-basin transitions 2020; Percival et al., 2021), the stretching direction was parallel suggesting a mechanically strong margin (Sapin et al., 2021). to Kaoko Belt if the transform model is upheld. In contrast, the southern Congo margin hosts numerous syn-rift Carbonate-dominated (non-skeletal) sediment production in (760 to 746 Ma) large-volume volcanic centres, and rift basins of the Otavi Group implies a low-latitude location for southwest opposing polarities followed by a broad post-rift shelf-to-basin Congo Craton from 770 until ~600 Ma (Lehmann et al., 2016), transition imply a mechanically weak and extended margin. when the carbonate platform was destroyed by abortive A rift-transform junction at the cape of Congo Craton is subduction and collisional orogeny. The palaeolatitude constraint kinematically compatible with existing evidence for north- arises from the synoptic temperature-dependence of carbonate northwest−south-southeast crustal stretching under the nascent saturation in surface seawater (Millero, 1979; Opdyke and Otavi Group carbonate platform. Stretching under the platform Wilkinson, 1990; Jiang et al., 2015). This evidence is not reflected is manifested by stratigraphic offlap−onlap relations and in palaeogeographic models that place Congo Craton in mid- associated clastic wedges related to Huab and Makalani crustal- latitudes (30 to 60°) at 600 Ma (e.g., Scotese, 2009; Merdith et al., scale rift-shoulder uplifts (Hoffman and Halverson, 2008; 2017a, b, 2019, 2021). Hoffman et al., 2021). A transform margin is consistent with only a 23% increase Acknowledgements in post-rift sediment thickness across the westward-facing shelf, compared with a 104% increase over the same distance across Field work was supported by the Natural Science and the southward-facing shelf. A prominent minimum in post-rift Engineering Research Council of Canada, the Geological Survey subsidence rate 90 to 100 km inboard from the southern shelf of Namibia, Harvard University, the United States National break implies an element of flexure, possibly in response to Science Foundation, and the Canadian Institute for Advanced volcanic loading in Northern Zone. Research. I am grateful to residents and farm holders in the A transform origin for the western Congo margin differs Kunene Region for access to their land. Comments by Francis from previous tectonic models that infer orthogonal rifting (e.g., Macdonald and constructive reviews by Stephen T. Johnston and Porada et al., 1983; Porada, 1989; Stanistreet et al., 1991; Jeremie Lehmann significantly improved the paper. Konopásek et al., 2018). If hyper-extended continental crust existed in northern Adamastor palaeocean (Konopásek et al.,
414 SOUTH AFRICAN JOURNAL OF GEOLOGY P.F. HOFFMAN
References Clerc, C., Ringenbach, J.-C., Jolivet, L. and Ballard, J.-F., 2018. Rifted margins: Ductile deformation, boudinage, continentward-dipping normal faults and the role of the weak lower crust. Gondwana Research, 53, 20-40. Affaton, P., Kalsbeek, F., Boudzoumou, F., Trompette, R., Thrane, K. and Frei, Clifford, T.N., 2008. The geology of the Neoproterozoic Swakop−Otavi R., 2016. The Pan-African West Congo Belt in the Republic of Congo transition zone in the Outjo District, northern Damara Orogen, Namibia. (Congo Brazzaville): Stratigraphy of the Mayumbe and West Congo South African Journal of Geology, 111, 117-140, 3 geological maps (in Supergroups studied by detrital zircon geochronology. Precambrian pocket) scale 1:40,000. Research, 272, 185-202. Collier, J.S., McDermott, C., Warner, G., Gyori, N., Schnabel, M., McDermott, Ahm, A.-S.C., Maloof, A.C., Macdonald, F.A., Hoffman, P.F., Bjerrum, C.J., Bold, K. and Horn, B.W., 2017. New constraints on the age and style of U., Rose, C.V., Strauss, J.V. and Higgins, J.A., 2019. An early diagenetic contiinental breakup in the South Atlantic from magnetic anomaly data. deglacial origin for basal Ediacaran “cap dolostones”. Earth and Planetary Earth and Planetary Science Letters, 477, 27-40. Science Letters, 506, 292-307. Coward, M.P., 1981. The junction between Pan-African mobile belts in Aizawa, M., Bluck, B., Cartwight, J., Milner, S., Swart, R. and Ward, J., 2000. Namibia: its structural history. Tectonophysics, 76, 59-73. Constraints on the geomorphological evolution of Namibia from the Coward, M.P., 1983. The tectonic history of the Damaran belt. In: R.McG. Miller offshore stratigraphic record. In: R.McG. Miller (Editor), Special Issue: (Editor), Evolution of the Damara Orogen of South West Africa/Namibia. Henno Martin Commemorative Issue. Communications of the Geological Special Publication 11, Geological Society of South Africa, 409-421. Survey of Namibia, 12, 337-346. Dalton, L.A. Bodak, T., Macdonald, F.A., Lahr, D.L.G. and Pruss, S.B., 2013. Alves, A., Janasi, V.A., Neto, M.C.C., Heaman, L. and Simonetti, A., 2013. U-Pb Preservational and morphological variability of assemblages of agglutinated geochronology of the granite magmatism in the Embu Terrane: Implications eukaryotes in Cryogenian cap carbonates of northern Namibia. Palaios, for the evolution of the Central Ribeira Belt, SE Brazil. Precambrian 28, 67-79. Research, 230, 1-12. Dalziel, I.W.D., 1997. Neoproterozoic−Paleozoic paleogeography and Arthaud, F. and Matte, P., 1975. Les décrochements tardihercynien du sudouest tectonics: Review, hypothesis, environmental speculation. Geological de l‘Europe. Geéometrie et essay de réconstituition des conditions de la Society of America Bulletin, 109, 16-42. deformation. Tectonophysics, 25, 139-171. Delpomdor, F., Eyles, N., Tack, L. and Préat, A., 2016. Pre- and post-Marinoan Barnes, S.-J. and Sawyer, E.W., 1980. An alternative model for the Damara carbonate facies of the Democratic Republic of the Congo: Glacially - mobile belt: ocean crust subduction and continental convergence. or tectonically-infl;uenced deep-water sediments? Paleogeography, Precambrian Research, 13, 297-336. Paleoclimatology, Paleoecology, 457, 144-157. Basei, M.A.S., Frimmel, D.E., Neto, M.C.C., Araujo, C.E.G., Castro, N.A. and de Kock, G.S., 1992. Forearc basin evolution in the Pan-African Damara Belt, Passarelli, C.R., 2018. The tectonic history of the southern Adamastor ocean central Namibia: the Hureb Formation of the Khomas Zone. Precambrian based on a correlation of the Kaoko and Dom Feliciano belts. In: Research, 57, 169-194. S. Siegesmund, M.A.S. Basei, P. Oyhantçabal and S. Oriolo (Editors), de Kock, G.S., 2001. A reappraisal of the Namibian Damara stratigraphy in Geology of Southwest Gondwana. Springer International, Berlin, 63-85. part of the Southern Swakop Terrane and its implications to basin Blackwell, D.D., 2005. Subduction zone backarcs, mobile belts and orogenic evolution. South African Journal of Geology, 104, 115-136. heat: comment. GSA Today, https://doi:10.1130/1052−5173(2005) de Kock, G.S., Eglington, B., Armstrong, R.A., Harmer, R.E. and Walraven, F., 015
SOUTH AFRICAN JOURNAL OF GEOLOGY 415 ON THE KINEMATICS AND TIMING OF RODINIA BREAKUP: A POSSIBLE RIFT−TRANSFORM JUNCTION OF CRYOGENIAN AGE AT THE SOUTHWEST CAPE OF CONGO CRATON (NORTHWEST NAMIBIA)
Ernst, R.E., Pereira, E., Hamilton, M.A., Pisarevsky, S.A., Rodriques, J., Tassinari, Town, 168 pp, cross-sections and 3 geological maps (in pocket) scale C.C.G., Teixeira W. and Van-Dunem, V., 2013. Mesoproterozoic intraplate 1:125,000 scale. magmatic ‘barcode’ record of the Angola portion of the Congo craton: Guj, P., 1974. A revision of the Damara stratigraphy along the southern margin Newly dated magmatic events at 1505 and 1110 Ma and implications for of Kamanjab inlier, South West Africa. In: A. Kröner (Editor), Contributions Nuna (Columbia) supercontinent reconstructions. Precambrian Research, to the Precambrian Geology of Southern Africa: A volume in Honour of 230, 103-118. John de Villiers. Bulletin 15, Precambrian Research Unit, University of Cape Evans, D.A.D., 2009. The paleomagnetically viable, long-lived and all-inclusive Town, 167-176. Rodinia supercontinent reconstruction. In: J.B. Murphy, J.D. Keppie, and Hälbich, I.W. and Alchin, D.J., 1995. The Gariep belt: stratigraphic−structural A.J. Hynes (Editors), Ancient Orogens and Modern Analogues. Special evidence for obliquely transformed grabens and back-folded thrust stacks Publication 327, Geological Society, London, 371-404. in a combined thick-skin thin-skin structural setting. Journal of African Earth Evans, D.A.D., 2013. Reconstructing pre-Pangean supercontinents. Geological Sciences, 21, 9-33. Society of America Bulletin, 125, 1735-1751. Hälbich, I.W. and Freyer, E.E., 1985. Structure and metamorphism of Damaran Fantozzi, P.L. and Sgavetti, M., 1998. Tectonic and sedimentary evolution of rocks in the Ugab profile. Communications of the Geological Survey of the eastern Gulf of Aden continental margins: new structural and South West Africa/Namibia, 1, 97. stratigraphic data from Somalia and Yemen. In: B.H. Purser and D.W.J. Halverson, G.P., Hoffman, P.F., Schrag, D.P., Maloof, A.C. and Rice, A.H.N., Bosence (Editors), Sedimentation and Tectonics of Rift Basins: Red 2005. Toward a Neoproterozoic composite carbon-isotope record. Sea−Gulf of Aden. Chapman and Hall, London, 56-76. Geological Society of America Bulletin, 117, 1181-1207. Frets, D.C., 1969. Geology and structure of the Huab−Welwitschia area, South Hartnady, C.J.H., Joubert, P. and Stowe, C., 1985. Proterozoic crustal evolution West Africa. Bulletin 5, Precambrian Research Unit, University of Cape in southwestern Africa. Episodes, 8, 236-244. Town, 235pp, geological map (in pocket) scale 1:150,000. Hedberg, R.M., 1979. Stratigraphy of the Ovamboland Basin, South West Frimmel, H.E., Tack, L., Basei, M.S., Nutman, A.P. and Boven, A., 2006. Africa. Bulletin 24, Precambrian Research Unit, University of Cape Town, Provenance and chemostratigraphy of the Neoproterozoic West Congolian 325pp, 6 geological maps (in pocket) scale 1:250,000. Group in the Democratic Republic of Congo. Journal of African Earth Henry, G., Clendenin, C.W., Stanistreet, I.G. and Maiden, K.J., 1990. Multiple Sciences, 46, 221-239. detachment model for the early rifting stage of the Late Proterozoic Damara Gao, B.F., Wu, C.Z., Yang, T., Santosh, M., Dong, L.H., Zhao, T.Y., Ye, H., orogen in Namibia. Geology, 18, 67-71. Lei, R.X. and Li, W., 2019. The Neoproterozoic “Blood Falls” in Tarim Henry, G., Osborne, M.A. and Schmerold, R.K., 1992/93. Note: Proposed craton and their possible connection with snowball Earth. Journal of lithostratigraphic subdivision of the Ugab Subgroup (Damara Sequence) in Geophysical Research: Earth Surface, 124, 229-244. the Kaokland, Namibia. Communications of the Geological Survey of Germs, G.J.B., 1974. The Nama Group in South West Africa and its relationship Namibia, 8, 143-145. to the Pan-African geosyncline. Journal of Geology, 82, 301-317. Higgins, J.A. and Schrag, D.P., 2003. Aftermath of a snowball Earth. Germs, G.J.B. and Gresse, P.G., 1991. The foreland basin of the Damara and Geochemistry, Geophysics, Geosystems, 4, 1028, doi:10.1029/ Gariep orogens in Namaqualand and southern Namibia: stratigraphic 2002GC000403 correlations and basin dynamics. South African Journal of Geology, 94, Hoffman, P.F., 1997. Tectonic genealogy of North America. In: B.A. van der 159-169. Pluijm and S. Marshak, Earth Structure: An Introduction to Structural Goscombe, B. and Gray, D.R., 2007. The Coastal Terrane of the Kaoko Belt, Geology and Tectonics. McGraw-Hill, New York, 459-464. Namibia: Outboard arc-terrane and tectonic significance. Precambrian Hoffman, P.F., 2011. Strange bedfellows: glacial diamictite and cap carbonate Research, 155, 139-158. from the Marinoan (635 Ma) glaciation in Namibia. Sedimentology, 58, Goscombe, B. and Gray, D., 2008. Structure and strain variation at mid-crustal 57-119. levels in a transpressional orogen: A review of Kaoko Belt structure and Hoffman, P.F., 2021. Cusp tectonics: an Ediacaran megakarst landscape and the character of West Gondwana amalgamation and dispersal. Gondwana bidirectional mass slides in a Pan-African syntaxis (northwest Namibia). Research, 13, 45-85. In: J.B. Murphy, R.A. Strachan and Q.C. Quesada (Editors), Pannotia to Goscombe, B., Foster, D.A., Gray, D. and Wade, B., 2018. The evolution of Pangea: Neoproterozoic and Paleozoic Orogenic Cycles in the Circum- the Damara orogenic system: A record of West Gondwana assembly and Atlantic Region. Special Publication 503, Geological Society, London, crustal response. In: S. Siegesmund, M.A.S. Basei, P. Oyhantçabal and https://doi.org/10.1144/SP503-2019-253 S. Oriolo (Editors), Geology of Southwest Gondwana. Springer Hoffman, P.F. and Halverson, G.P., 2008. Otavi Group of the western Northern International, Berlin, 303-352. Platform, the Eastern Kaoko Zone and the western Northern Margin Zone. Goscombe, B., Foster, D.A., Gray, D. and Wade, B., 2020. Assembly of central In: R.McG. Miller (Editor), The Geology of Namibia, Volume 2. Geological Gondwana along the Zambezi Belt: Metamorphic response and basement Survey of Namibia, Windhoek, 13-69 13-136. reactivation during the Kuunga orogeny. Gondwana Research, 80, 410-465. Hoffman, P.F. and Halverson, G.P., 2018. Discussion of “Depositional ages and Goscombe, B., Foster, D.A., Gray, D., Wade, B., Marsellos, A. and Titus, J., provenance of the Neoproterozoic Damara Supergroup (northwest 2017. Deformation correlations, stress field switches and evolution of an Namibia): Implications for the Angola-Congo and Kalahari cratons orogenic intersection: The Pan-African Kaoko−Damara orogenic junction, connection” by D.B. Nascimento, R.S. Schmitt, A. Ribeiro, R.A.J. Trouw, Namibia. Geoscience Frontiers, 8, 1187-1232. C.W. Passchier, and M.A.S. Basei. Gondwana Research, 58, 235-238. Goscombe, B., Gray, D., Armstrong, R., Foster, D.A. and Vogl, J., 2005. Event Hoffman, P.F. and Lamothe, K.G., 2019. Seawater-buffered diagenesis, geochronology of the Pan-African Kaoko Belt, Namibia. Precambrian destruction of carbon isotope excursions, and the composition of DIC in Research, 140, 103.e1-e41. Neoproterozoic oceans. Proceedings of the National Academy of Sciences Goscombe, B., Hand, M. and Gray, D., 2003. Structure of the Kaoko Belt, USA, 116, 18874-18879. Namibia: progressive evolution of a classic transpressional orogen. Journal Hoffman, P.F. and Schrag, D.P., 2002. The snowball Earth hypothesis: testing of Structural Geology, 25, 1049-1081. the limits of global change. Terra Nova, 14, 129-155. Gresse, P.G., 1995. Transpression and transection in the late Pan-African Hoffman, P.F., Halverson, G.P., Domack, E.W., Husson, J.M., Higgins, J.A. and Vanrhynsdorp foreland thrust-fold belt, South Africa. Journal of African Schrag, D.P., 2007. Are basal Ediacaran (635 Ma) post-glacial “cap Earth Sciences, 21, 91-105. dolostones” diachronous? Earth and Planetary Science Letters, 258, 114-131. Grotzinger, J.P., Bowring, S.A., Saylor, B.Z. and Kaufman, A.J., 1995. Hoffman, P.F., Halverson, G.P., Schrag, D.P., Higgins, J.A., Domack, E.W., Biostratigraphic and geochronological constraints on early animal Macdonald, F.A., Pruss, S.B., Blättler, C.L., Crockford, P.W., Hodgin, E.B., evolution. Science (AAAS), 270, 598-604. Bellefroid, E.J., Johnson, B.W., Hodgskiss, M.S.W., Lamothe, K.G., LoBianco, Guj, P., 1970. The Damara Mobile Belt in the South-western Kaokoveld, South S.J.C., Busch, J.F., Howes, B.J., Greenman, J.W. and Nelson, L.L., 2021. West Africa. Bulletin 8, Precambrian Research Unit, University of Cape Snowballs in Africa: sectioning a long-lived Neoproterozoic carbonate
416 SOUTH AFRICAN JOURNAL OF GEOLOGY P.F. HOFFMAN
platform and its bathyal foreslope (NW Namibia). Earth-Science Reviews, Kasemann, S.A., Prave, A.R., Fallick, A.E., Hawkesworth, C.J. and Hoffmann, https://www.sciencedirect.com/journal/earth-science-reviews/vol/217/suppl/C K.-H., 2010. Neoproterozoic ice ages, boron isotopes, and ocean Hoffman, P.F., Hawkins, D.P., Isachsen, C.E. and Bowring, S.A., 1996. Precise acidification: Implications for a snowball Earth. Geology, 38, 775-778. U-Pb zircon ages for early Damaran magmatism in the Summas Mountains Kennedy, M.J., Runnegar, B., Prave, A.R., Hoffmann, K.-H. and Arthur, M.A., and Welwitschia Inlier, northern Damara belt, Namibia. Communications 1998. Two or four Neoproterozoic glaciations? Geology, 26, 1059-1063. of the Geological Survey of Namibia, 11, 47-52. Khodayar, M., Björnsson, S., Kristinsson, S.G., Karlsdóttir, R., Ólafsson, M. and Hoffman, P.F., Lamothe, K.G. and Greenman, J.W., 2018. Report: Stratigraphic Víkingsson, S., 2018. Tectonic control of the Theistareykir geothermal field investigations of the Neoproterozoic Otavi/Swakop Group in the southern by rift and transform zones in north Iceland: a multidisciplinary approach. Kunene Region. Communications of the Geological Survey of Namibia, Open Journal of Geology, 8, 543-584. 20, 100-113. Kleinhanns, I.C., Fullgraf, T., Wilsky, F., Nolte, N., Fliegel, D., Klemd, R. and Hoffman, P.F., Lamothe, K.G., LoBianco, S.J.C., Hodsgskiss, M.S.W., Hansen B.T., 2015. U-Pb zircon ages and (isotope) geochemical signatures Bellefroid, E.J., Johnson, B.W., Hodgin, E.B. and Halverson, G.P., 2017. of the Kamanjab Inlier (NW Namibia): constraints on Palaeoproterozoic Sedimentary depocenters on Snowball Earth: Case studies from the Sturtian crustal evolution along the southern Congo craton. In: N.M.W. Roberts, Chuos Formation in northern Namibia. Geosphere, 13, 811-837. M. van Kranendonk, S. Parman, S. Shirey and P.D. Clift (Editors), Continent Hoffmann, K.-H., 1991. Stratigraphic analysis of eustatic and tectonic effects Formation Through Time. Special Publication 389, Geological Society, on subsidence and deposition during convergent margin sedimentation London, 165-195 in the Damara Belt and adjacent cratonic foreland basins. Terra Nova, Konopásek, J., Cavalcante, C., Fossen, H. and Janoušek, V., 2020. Adamastor Abstracts Supplement, 3, 15-16. – an ocean that never existed? Earth-Science Reviews, 205, 103201, 1-18. Hoffmann, K.-H. and Prave, A.R., 1996. A preliminary note on a revised Konopásek, J., Hoffmann, K.-H., Sláma, J. and Košler, J., 2017. The onset of subdivision and regional correlation of the Otavi Group based on flysch sedimentation in the Kaoko Belt (NW Namibia) – Implications for glaciogenic diamictites and associated cap dolomites. Communications of the pre-collisional evolution of the Kaoko−Dom Feliciano−Gariep orogen. the Geological Survey of Namibia, 11, 77-82. Precambrian Research, 298, 220-234. Hueck, B., Oyhantçabal, P., Philipp, R.P., Basei, M.A.S. and Siegesmund S., Konopásek, J., Janoušek, V., Oyhantçabal, P., Sláma, J. and Ulrich, S., 2018. 2018. The Dom Feliciano Belt in southern Brazil and Uruguay. In: Did the circum-Rodinia subduction trigger the Neoproterozoic rifting along S. Siegesmund, M.A.S. Basei, P. Oyhantçabal and S. Oriolo (Editors), the Congo−Kalahari Craton margin? International Journal of Earth Sciences, Geology of Southwest Gondwana. Springer Nature, 267-302. 107, 1859-1894. Hurtgen, M.T., Halverson, G.P., Arthur, M.A. and Hoffman, P.F., 2006. Sulfur Konopásek, J., Košler, J., Sláma, J. and Janoušek, V., 2014. Timing and sources cycling in the aftermath of a 635-Ma snowball glaciation: Evidence for a of pre-collisional Neoproterozoic sedimentation along the SW margin of syn-glacial sulfidic deep ocean. Earth and PLanetary Science Letters, the Congo Craton (Kaoko Belt, NW Namibia). Gondwana Research, 26, 245, 551-570. 386-401. Hyndman, R.D., Currie, C.A. and Mazzotti, S.P., 2005. Subduction zone Konopásek, J., Kröner, S., Kitt, S.L., Passchier, C.W. and Kröner, A., 2005. backarcs, mobile belts, and orogenic heat. GSA Today, 15, 4-10. Oblique collision and evolution of large-scale transcurrent shear zones in Jacob, R.E., Moore, J.M. and Armstrong, R.A., 2000. Zircon and titanite age the Kaoko belt, NW Namibia. Precambrian Research, 136, 139-157. determinations from igneous rocks in the Karibib District, Namibia: Konopásek, J., Sláma, J. and Košler, J., 2016. Linking the basement geology implications for Navachab vein-style gold mineralization. Communications along the Africa–South America coasts in the South Atlantic. Precambrian of the Geological Survey of Namibia, 12, 157-166. Research, 280, 221-230. Jerram, D., Mountney, N., Holzförster, F. and Stollhofen, H., 1999. Internal Kröner, A. and Correia, H., 1980. Continuation of the Pan African Damara belt stratigraphic relationships in the Etendeka Group in the Huab Basin, NW into Angola: a proposed correlation of the Chela Group in southern Angola Namibia: understanding the onset of flood volcanism. Journal of with the Nosib Group in northern Namibia/SWA. Transactions of the Geodynamics, 28, 393-418. Geological Society of South Africa, 83, 5-16. Jerram, D.A., Mountney, N., Howell, J. and Stollhofen, H., 2000. The Fossilized Lan, Z.W., Huyskens, M.H., Lu, K., Li, X.H., Zhang, G.Y., Lu, D.B. and Yin, Desert: Recent developments in our understanding of the Lower Cretaceous Q.Z., 2020. Toward refining the onset age of Sturtian glaciation in South deposits in the Huab Basin, NW Namibia. In: R.McG. Miller (Editor), Special China. Precambrian Research, 338, 105555, 1-8. Issue: Henno Martin Commemorative Volume, Communications of the Le Ber, E., Le Heron, D.P., Winterleitner, G., Bosence, D. and Vining, B.A., 2013. Geological Survey of Namibia, 12, 269-278. Microbialite recovery in the aftermath of the Sturtian glaciation: Insights Jiang, L.Q., Feely, R.A., Carter, B.R., Greeley, D.J., Gledhill, D.K. and Arzayus, from the Rasthof Formation, Namibia. Sedimentary Geology, 294, 1-12. K.M., 2015. Climatological distribution of aragonite saturation state in the Lechte, M.A., Wallace, M.W. and Hoffmann, K.-H., 2018. Glacio-marine iron global oceans. Global Biogeochemical Cycles, 29, 1656-1673. formation deposition in a c. 700 Ma glaciated margin: insights from the Jing, X.Q., Yang, Z.Y., Evans, D.A.D., Tong, Y.B., Xu, Y.C. and Wang, H., 2020. Chuos Formation, Namibia. In: D.P. Le Heron, K.A. Hogan, E.R. Phillips, A pan-latitudinal Rodinia in the Tonian true polar wander frame. Earth and M. Huuse, M.E. Busfield and A.G.C. Graham (Editors), Glaciated Margins: Planetary Science Letters, 530, 115880, 1-14. The Sedimentary and Geophysical Archive. Special Publication 475, Johnson, S.D., Poujol, M. and Kisters, A.F.M., 2006. Constraining the timing Geological Society, London, 9-34. and migration of collisional tectonics in the Damara Belt, Namibia: U-Pb Lechte, M.A., Wallace, M.W., van Smeerdijk Hood, A, Li, W.Q., Halverson, G.P., zircon ages for the syntectonic Salem-type Stinkbank granite. South African Asael, D., MCColl, S.L. and Planavsky, N.J., 2019. Subglacial meltwater Journal of Geology, 109, 611-624. supported aerobic marine habitats during Snowball Earth. Proceedings of Kamguia Kamani, M.S., Wang, W., Tchouankoue, J.-P., Huang, S.F., Yomeun, the National Academy of Sciences USA, 116, 25,478-25,483. B., Xue, E.K. and Lu, G.M., 2021. Neoproterozoic syn-collision magmatism Le Heron, D.P., Busfield, M.E. and Kettler, C., 2020. Ice-rafted dropstones in in the Nkondjock region at the northern border of the Congo craton in “postglacial” Cryogenian cap carbonates. Geology, 49, https://doi.org/ Cameroon: Geodynamic implications for the Central African orogenic belt. 10.1130/G48208.1 Precambrian Research, 353, 106015, 1-19. Le Heron, D.P., Busfield, M.E., Le Ber, E. and Kamona, A.F., 2013. Karig, D.E., 1974. Evolution of arc systems in the western Pacific. Annual Neoproterozoic ironstones in northern Namibia: Biogenic precipitation and Reviews of Earth and Planetary Sciences, 2, 51-75. Cryogenian glaciation. Palaeogeography, Palaeoclimatology, Palaeoecology, Kasch, K.W., 1983. Continental collision, suture progradation and thermal 369, 48-57. relaxation: a plate tectonic model for the Damara Orogen in central Lehmann, J., Saalmann, K., Naydenov, K.V., Milani, L., Belyanin, G.A., Namibia. In: R.McG. Miller (Editor), Evolution of the Damara Orogen of Zwingmann, H., Charlesworth, G. and Kinnaird, J.A., 2016. Structural and South West Africa/Namibia. Special Publication 11, Geological Society of geochronological constraints on the Pan-African tectonic evolution of the South Africa, 423-429. northern Damara Belt, Namibia. Tectonics, 35, 103-135.
SOUTH AFRICAN JOURNAL OF GEOLOGY 417 ON THE KINEMATICS AND TIMING OF RODINIA BREAKUP: A POSSIBLE RIFT−TRANSFORM JUNCTION OF CRYOGENIAN AGE AT THE SOUTHWEST CAPE OF CONGO CRATON (NORTHWEST NAMIBIA)
Li, Z.X., Bogdanova, S.V., Collins, A.S., Davidson, A., De Waele, B., Ernst, R.E., Merdith, A.S., Williams, S.A., Collins, A.S., Tetley, M.G., Mulder, J.A., Blades, Fitzsimmons, I.C.W., Fuck, R.A., Gladkochup, D.P., Jacobs, J., Karlstrom, M.L., Young, A., Armistead, S.E., Cannon, J., Zahirovic, S. and Müller, R.D., K.E., Lu, S., Natapov, L.M., Pease, V., Pisarevsky, S.A., Thrane, K. and 2021. Extending full-plate tectonic models into deep time: Linking the Vernikovsky, V., 2008. Assembly, configuration, and break-up history of Neoproterozoic and the Phanerozoic. Earth-Science Reviews, 214, 103477. Rodinia: A synthesis. Precambrian Research, 160, 179-210. Mikucki, J.A., Pearson, A., Johnston, D.T., Turchyn, A.V., Farquhar, J., Macdonald, F.A., Schmitz, M.D., Strauss, J.V., Halverson, G.P., Gibson, T.M., Schrag, D.P., Anbar, A.D., Priscu, J.C. and Lee, P.A., 2009. A contemporary Eyster, A., Cox, G., Mamroi, P. and Crowley, J.L., 2018. Cryogenian of microbially maintained subglacial ferrous “ocean”. Science (AAAS), Yukon. Precambrian Research, 319, 114-143. 324, 397-400. MacLennan, S., Park, Y., Swanson-Hysell, N., Maloof, A., Schoene, B., Miller, R.McG., 1974. The stratigraphic significance of the Naauwpoort Gebreslassie, M., Antilla, E., Tesema, T., Alene M. and Haileab, B., 2018. Formation of east central Damaraland, South West Africa. Transactions of The arc of the Snowball: U-Pb dates constrain the Islay anomaly and the the Geological Society of South Africa, 77, 363-367. initiation of the Sturtian glaciation. Geology, 46, 539-542. Miller, R.McG., 1980. Geology of a Portion of Central Damaraland, South West Maestro, A., Jané, G., Llave, E., López-Martínez, J., Bohoyo, F. and Druet, M., Africa/Namibia. South West Africa Series No. 6, Geological Survey of South 2018. The role of tectonic inheritance in the morphostructural evolution of Africa, Pretoria, 78pp. the Galicia continental margin and adjacent abyssal plains from digital Miller, R.McG., 1983. The Pan-African Damara Orogen of South West bathymetric model (DBM) analysis (NW Spain). International Journal of Africa/Namibia. In: R.McG. Miller (Editor), Evolution of the Damara Orogen Earth Sciences (Geologische Rundschau), 1007, 1267-1286. of South West Africa/Namibia. Special Publication 11, Geological Society Maloof, A.C., 2000. Superposed folding at the junction of the inland and of South Africa, 431-515. coastal belts, Damara Orogen, NW Namibia. In: R.McG. Miller (Edior), Miller, R.McG., 1997. The Owambo Basin of northern Namibia. In: R.C. Selley Special Issue: Henno Martin Commemorative Volume. Communications of (Editor), African Basins. Sedimentary Basins of the World Volume 3, the Geological Survey of Namibia, 12, 89-98. Elsevier, Amsterdam, 237-268. Martin, H., 1965a. Beobeachtungen zum Problem der jung-Präkambrischen Miller, R.McG., 2008a. The Geology of Namibia: Volume 1, Archaean to Glazialen ablagerungen in Südwestafrika. Geologische Rundschau, 54, 115-127. Mesoproterozoic. Geological Survey of Namibia, Windhoek. Martin, H., 1965b. The Precambrian Geology of South West Africa and Miller, R.McG., 2008b. The Geology of Namibia: Volume 2, Neoproterozoic to Namaqualand. Precambrian Research Unit, University of Cape Town, 159pp. Lower Paleozoic. Geological Survey of Namibia, Windhoek. Martin, H., 1983. Overview of the geosynclinal, structural and metamorphic Miller, R.McG., 2008c. The Geology of Namibia: Volume 3, Palaeozoic to development of the intracontinental branch of the Damara orogen. In: Cenozoic. Geological Survey of Namibia, Windhoek. H. Martin and F.W. Eder (Editors), Intracontinental Fold Belts. Springer- Miller, R.McG., 2012. Review of Mesoproterozoic magmatism, sedimentation Verlag, Berlin, 473-502. and terrane amalgamation in southwestern Africa. South African Journal of Mbede, E.I., Kumpunzu, A.B. and Armstrong, A.E., 2004. Neoproterozoic Geology, 115, 417-448. inheritance during Cainozoic rifting in the western and southern branches Miller, R.McG., 2014. Comparative stratigraphic and geochronological of the East African rift system: Evidence from carbonatite and alkaline evolution of the northern Damara Supergroup in Namibia and the Katanga intrusions. Conference abstract, The East African Rift System: Development, Supergroup in the Lufilian arc of Central Africa. Geoscience Canada, 40, Evolution and Resources, Addis Ababa, June 20-24, 2004. 118-140. McDermott, K., Gilbard, E. and Clarke, N., 2015. From basalt to skeletons – Millero, F.J., 1979. The thermodynamics of the carbonate system in seawater. the 200 million-year history of the Namibian margin uncovered by new Geochimica et Cosmochimica Acta, 43, 1651-1661. seimic data. First Break, 33, 77-85. Moloto-A-Kenguemba, G.R., Trindade, R.I.F., Monié, P. Nédélec, A. and Siqueira, McGee, B., Collins, A.S., Trindade, R.I.F. and Jourdan, F., 2015a. Investigating R., 2008. A late Neoproterozoic paleomagnetic pole for the Congo craton: mid-Ediacaran glaciation and final Gondwana amalgamation using coupled Tectonic setting, paleomagnetism and geochronology of the Nola dike sedimentology and 40Ar/39Ar detrital muscovite provenance from the swarm (Central African Republic). Precambrian Research, 164, 214-226. Paraguay Belt, Brazil. Sedimentology 62, 130-154. Monié, P., Bosch, D., Bruguier, O., Vauchez, A., Rolland, Y., Nsungani, P. and McGee, B., Collins, A.S., Trindade, R.I.F. and Payne, J., 2015b. Age and Buta Neto, A., 2012. The Late Neoproterozoic/Early Palaeozoic evolution provenance of the Cryogenian to Cambrian passive margin to foreland of the West Congo Belt of NW Angola: geochronological (U-Pb and Ar-Ar) basin sequence of the northern Paraguay Belt, Brazil. Geological Society and petrostructural constraints. Terra Nova, 24, 238-247. of America Bulletin, 127, 76-86. Morley, C.K., 2017. The impact of multiple extension events, stress rotation McGee, B., Halverson, G.P. and Collins, A.S., 2012. Cryogenian rift-related and inherited fabrics on normal fault geometries and evolution in magmatism and sedimentation: South-western Congo Craton, Namibia. the Cenozoic rift basins of Thailand. In: C. Childs, R.E. Holdsworth, Journal of African Earth Sciences, 76, 34-49. C.A.-L. Jackson, T. Manzocchi, J.J. Walsh and G. Yielding (Editors), The McMillan, I.K., Brink, G.J., Broad, D.S. and Maier, J.J., 1997. Late Mesozoic Geometry and Growth of Normal Faults. Special Publication 439, Geological sedimentary basins off the south coast of South Africa. In: R.C. Selley Society, London, 413-445. (Editor), African Basins. Sedimentary Basins of the World Volume 3, Narbonne, G.M., Xiao, S.H., Shields, G.A. and Gehling, J.G., 2012. The Elsevier, Amsterdam, 319-376. Ediacaran Period. In: F.M. Gradstein, J.G. Ogg and M. Schmitz (Editors), Meert, J.G., van der Voo, R. and Ayub, S., 1995. Paleomagnetic investigation The Geologic Time Scale 2012. Elsevier, Amsterdam, 413-435. of the Neoproterozoic Gagwe lavas and Mbozi complex, Tanzania and the Nascimento, D.B., Ribeiro, A., Trouw, R.A.J., Schmitt, R.S. and Passchier, C.W., assembly of Gondwana. Precambrian Research, 74, 225-244. 2016. Stratigraphy of the Neoproterozoic Damara Sequence in northwest Meneghini, F., Kisters, A., Buick, I. and Fagereng, Å., 2014. Fingerprints of late Namibia: Slope to basin sub-marine mass-transport deposits and olisotlith Neoproterozoic ridge subduction in the Pan-African Damara Belt, Namibia. fields. Precambrian Research, 278, 108-125. Geology, 42, 903-906. Nascimento, D.B., Schmitt, R.S., Ribeiro, A., Trouw, R.A.J., Passchier, C.W. Merdith, A.S., Collins, A.S., Williams, S.E., Pisarevsky, S., Foden, J.D., Archibald, and Basei, M.A.S., 2017. Depositional ages and provenance of the D.B., Blades, M.L., Alessio, B.L., Armistead, S., Plavsa, D., Clark, C. and Neoproterozoic Damara Supergroup (northwest Namibia): Implications Müller, R.D., 2017a. A full-plate global reconstruction of the Neoproterozoic. for the Angola-Congo and Kalahari cratons connection. Gondwana Gondwana Research, 50, 84-134. Research, 52, 153-171. Merdith, A.S., Williams, S.E., Müller, R.D. and Collins, A.S., 2017b. Kinematic Nelson, L.L., Smith, E.F., Hodgin, E.B., Crowley, J.L., Schmitz, M.D. and constraints on the Rodinia to Gondwana transition. Precambrian Research, Macdonald, F.A., 2020. Geochronological constraints on Neoproterozoic 299, 132-150. rifting ond onset of the Marinoan glaciation from the Kingston Peak Merdith, A.S., Williams, S.E., Brune, S., Collins, A.S. and Müller, R.D., 2019. Formation in Death Valley, California. Geology, 48, 1083-1087. Rift and plate boundary evolution across two supercontinent cycles. Global Nieminski, N.M., Grove, M. and Lowe, D.R., 2018. Provenance of the and Planetary Change, 173, 1-14. Neoproterozoic deep-water Zerrissene Group of the Damara Orogen,
418 SOUTH AFRICAN JOURNAL OF GEOLOGY P.F. HOFFMAN
Namibia, and paleogeographic implications for the closing of the Microbial facies in a Sturtian cap carbonate, the Rasthof Formation, Otavi Adamastor Ocean and assembly of the Gondwana supercontinent. Group, northern Namibia. Precambrian Research, 181, 187-208. Geological Society of America Bulletin, 131, 355-371. Roberts, D.G. and Kidd, R.B., 1984. Sedimentary and structural patterns on Opdyke, B.N. and Wilkinson, B.H., 1990. Paleolatitude distribution of the Iberian continental margin: an alternative view of continental margin Phanerozoic marine ooids and cements. Palaeogeography, Palaeoclimatology, sedimentation. Marine and Petroleum Geology, 1, 37-48. Palaeoecology, 78, 135-148. Rooney, A.D., Strauss, J.V. and Macdonald. F.A., 2015. A Cryogenian Oriolo, S., Oyhantçabal, P., Wemmer, K. and Siegesmund, S., 2017. chronology: Two long-lasting synchronous Neoproterozoic glaciations. Contemporaneous assembly of western Gondwana and final Rodinia break- Geology, 43, 459-462. up: Implications for the supercontinent cycle. Geoscience Frontiers, Rooney, A.D., Yang, C., Condon, D.J., Zhu, M.Y. and Macdonald, F.A., 2020. 8, 1431-1445. U-Pb and Re−Os geochronology in the Sturtian snowball Earth aftermath. Oyhantçabal, P., Siegesmund, S., Wemmer, K. and Passchier, C.W., 2011. The Geology, 48, 625-629. transpressional connection between Dom Feliciano and Kaoko belts at Rust, D. and Whitworth, M., 2019. A unique ~12 ka subaerial record of rift- 580-550 Ma. International Journal of Earth Sciences, 100, 379-390. transform triple-junction tectonics, NE Icerland. Scientific Reports, 9, 9669, Partin, C.A. and Sadler, P.M., 2016. Slow net accumulation sets snowball Earth https://doi.org/10.1038/s41598-019-45903-8 apart from all younger glacial episodes. Geology, 44, 1019-1022. SACS (South African Committee for Stratigraphy), 1980. Damara Sequence. Passchier, C.W., Trouw, R.A.J., Ribeiro, A. and Paciullo, F.V.P., 2002. Tectonic In: L.E. Kent (Editor), Stratigraphy of South Africa Part 1: Lithostratigraphy evolution of the southern Kaoko belt, Namibia. Journal of African Earth of the Republic of South Africa, South West Africa/Namibia and the Sciences, 35, 61-75. Republics of Bophuthatswana, Transkei and Venda. Handbook 8, Passchier, C., Trouw, R. and da Silva Schmitt, R., 2016. How to make a Geological Survey of South Africa, Pretoria, 415-438. transverse triple junction–New evidence for the assemblage of Gondwana Salminen, J., Hanson, R., Evans, D.A.D., Gong, Z., Larson, T., Walker, O., along the Kaoko−Damara belt, Namibia. Geology, 44, 843-846. Gumsley, A., Söderlund, U. and Ernst, R., 2018. Direct Mesoproterozoic Paton, D.A. and Underhill, J.R., 2004. Role of crustal anisotropy in modifying connection of the Congo and Kalahari cratons in proto-Africa: Strange the structural and sedimentological evolution of extensional basins: the attractors across supercontinental cycles. Geology, 46, 1011-1014. Gamtoos Basin, South Africa. Basin Research, 16, 339-359. Sapin, F., Ringenbach, J.-C. and Clerc, C., 2021. Rifted margins classification Percival, J.J., Konopásek, J., Eiesland, R., Sláma, J., Campos, R.S. de, Battisti, and forcing parameters. Nature Scientific Reports, 11, 8199, https://doi.org/ M.A. and Bitencourt, M. de F., 2021. Pre-orogenic connection of the 10.1038/s41598-021-87648-3. foreland domains of the Kaoko−Dom Feliciano−Gariep orogenic system. Sawyer, E.W., 1981. Damaran Structural and Metamorphic Geology of an Area Precambrian Research, 354, 106060, 1-20. South-east of Walvis Bay, South West Africa/Namibia. Memoir 7, Geological Perrin, C., Manighetti, I. and Gaudemer, Y., 2016. Off-fault tip splay networks: Survey of South West Africa, Windhoek, 94pp. A genetic and generic property of faults indicative of their long-term Schermerhorn, L.J.G., 1961. Sedimentary cycles in the West Congo propagation. Comptes Rendus Geoscience, 348, 52-60. Geosyncline of Northwest Angola. Boletim 3, Servicios de Geologia e Petrie, S.H., Brown, J.R., Granger, P.J. and Lovell, J.P.B., 1989. Mesozoic history Minas, Luanda, 49-62. of the Celtic Sea basins. In: A.J. Tankard and H.R. Balkwill (Editors), Schreiber, U.M., 2006. Sheet 2014 – Fransfontein (Provisional). Geological Map Extensional Tectonnics and Stratigraphy of the North Atlantic Margins. of Namibia, 1:250,000 Geological Series, Geological Survey of Namibia, Memoir 46, American Association of Petroleum Geologists, Tulsa, Windhoek. Oklahoma, 433-444. Scotese, C.R., 2009. Late Proterozoic plate tectonics and paleogeography: a Pisarevsky, S.A., Murphy, J.B., Cawood, P.A. and Collins, A.S., 2008. Late tale of two supercontinents, Rodinia and Pannotia. In: J. Craig, J. Thurlow, Neoproterozoic and Early Cambrian palaeogeography: models and A. Whitham and Y. Abutarruma (Editors), Neoproterozoic Petroleum problems. In: R.J. Pankhurst, R.A.J. Trouw, B.B. Brito Neves and M.J.de Wit Systems: The Emerging Potential in North Africa. Special Publication 326, (Editors), West Gondwana: Pre-Cenozoic Correlations Across the South Geological Society, London, 67-83. Atlantic Region. Special Publication 294, Geological Society, London, 9-31. Seth, B., Kröner, A., Mezger, K., Nemchin, A.A., Pidgeon, R.T. and Okrusch, Pisarevsky, S.A., Wingate, M.T.D., Powell, C.McA., Johnson, S. and Evans, M., 1998. Archaean to Neoproterozoic magmatic events in the Kaoko belt D.A.D., 2003. Models of Rodinia assembly and fragmentation. In: of NW Namibia and their geodynamic significance. Precambrian Research, M. Yoshida, B.F. Windley, and S. Dasgupta (Editors), Proterozoic East 92, 341-363. Gondwana: Supercontinent Assembly and Breakup. Special Publication Smit, J.M., 1962. Stratigraphy and metamorphism of the Otavi Series south- 206, Geological Society, London, 35-55. east of Otavi, South West Africa. Transactions of the Geological Society of Poidevin, J.-L., 2007. Stratigraphie isotopique du strontium et datation des South Africa, 65, 63-78. formations carbonatées et glaciogéniques néoprotérozoiques du Nord et Stanistreet, I.G. and Charlesworth, E.G., 1999. Damaran Basement-cored Fold de l’Ouest du craton du Congo. C. R. Geoscience, 339, 259-273. Nappes Incorporating Pre-collisional Basins, Kaoko Belt, Namibia, and Porada, H., 1974. The Khoabendus Formation in the area northwest of Controls on Mesozoic Supercontinental Breakup. Information Circular 332, Kamanjab and in the southeastern Kaokoveld, South West Africa. South Economic Geology Research Unit, University of Witwatersrand, West Africa Series No. 4, Geological Survey of South Africa, Pretoria, 23pp. Johannesburg, 14pp. Porada, H., 1979. The Damara−Ribeira orogen of the Pan-African−Brasiliano Stanistreet, I.G., Kukla, P.A. and Henry, G., 1991. Sedimentary basinal cycle in Namibia (Southwest Africa) and Brazil as interpreted in terms of responses to a Late Precambrian Wilson Cycle: the Damara Orogen and continental collision. Tectonophysics, 57, 237-265. Nama Foreland, Namibia. Journal of African Earth Sciences, 13, 141-156. Porada, H., 1983. Geodynamic model for the geosynclinal development of the Stanton, W.I., Schermerhorn, L.J.G. and Korpershoek, H.R., 1963. The West Damara Orogen, Namibia, South West Africa. In: H. Martin and F.W. Eder Congo System. Boletim 8, Servicios de Geologia e Minas, Luanda, 69-78. (Editors), Intracontinental Fold Belts. Springer-Verlag, Heidelberg, 503-541. Swart, R., 1992a. The sedimentology of the Zerrissene turbidite system, Porada, H., 1989. Pan-African rifting and orogenesis in southern to equatorial Damara Orogen, Namibia. Memoir 13, Geological Survey of Namibia, Africa and eastern Brazil. Precambrian Research, 44, 103-136. Windhoek, 54p. Porada, H., Ahrendt, H., Behr, H.-J. and Weber, K., 1983. The join of the coastal Swart, R., 1992b. Facies analysis of late Proterozoic carbonate turbidites in the and intracontinental branches of the Damara Orogen, Namibia, South West Zerrissene Basin, Damara Orogen, Namibia. Journal of African Earth Africa. In: H. Martin and F.W. Eder (Editors), Intracontinental Fold Belts. Sciences, 14, 283-294. Springer-Verlag, Heidelberg, 901-912. Tibaldi, A., Bonalli, F.L. and Pasquaré Mariotto, F.A., 2016. Interaction between Prave, A.R., 1996. Tale of three cratons: Tectonostratigraphic anatomy of the transform faults and rift systems: a combined field and experimental Damara orogen in northwestern Namibia and the assembly of Gondwana. approach. Frontiers in Earth Science, 4, 33, 1-18. Geology, 24, 1115-1118. Tohver, E., Cawood, P.A., Rossello, E.A. and Jourdan, F., 2012. Closure of the Pruss, S.B., Bosack, T., Macdonald, F.A., McLane, M. and Hoffman, P.F., 2010. Clymene Ocean and formation of West Gondwana in the Cambrian:
SOUTH AFRICAN JOURNAL OF GEOLOGY 419 ON THE KINEMATICS AND TIMING OF RODINIA BREAKUP: A POSSIBLE RIFT−TRANSFORM JUNCTION OF CRYOGENIAN AGE AT THE SOUTHWEST CAPE OF CONGO CRATON (NORTHWEST NAMIBIA)
Evidence from the Sierras Australes of the southernmost Rio de la Plata Wildman, M., Brown, R., Watkins, R., Carter, A., Gleadow, A. and craton, Argentina. Gondwana Research, 21, 394-405. Summerfield, M., 2015. Post break-up inversion across the southwestern Trindade, R.I.F. and Macouin M., 2007. Palaeolatitude of glacial deposits and cape of South Africa: New insights from apatite and zircon fission track palaeogeography of Neoproterozoic ice ages. C. R. Geoscience, 339, thermochronometry. Tectonophysics, 654, 30-55. 200-211. Will, T.M., Okrusch, M. and Gruner, B.B., 2004. Barrovian and Buchan type Trompette, R. (Carozzi, A.V., translator), 1994. Geology of Western Gondwana metamorphism in the Pan-African Kaoko belt, Namibia: implications for its (2000−500 Ma): Pan-African – Brasiliano Aggregation of South America and geotectonic position with the framework of Western Gondwana. South Africa. A. A. Balkema, Rotterdam, 350pp. African Journal of Geology, 107, 431-454. Uliana, M.A., Biddle, K.T. and Cerdan, J., 1989. Mesozoic extension and Wingate, M.T., Pisarevsky, S.A. and De Waele, B., 2004. Paleomagnetism of the the formation of Argenitine sedimentary basins. In: A.J. Tankard and 765 Ma Luakele Volcanics in NW Zambia and implications for Neoproterozoic H.R. Balkwill (Editors), Extensional Tectonnics and Stratigraphy of the positions of the Congo Craton. Eos, Transactions of the American North Atlantic Margins. Memoir 46, American Association of Petroleum Geophysical Union, 85, Fall Meeting Supplement, Abstract U32A-03. Geologists, Tulsa, Oklahoma, 599-614. Yoshioka, H., Asahara, Y., Tojo, B. and Kawakami, S., 2003. Systematic Wanke, A., Stollhofen, H., Stanistreet, I.G. and Lorenz, V., 2000. Karoo variations in C, O, and Sr isotopes and elemental concentrations in unconformities in NW Namibia and their tectonic implications. In: R.McG. Neoproterozoic carbonates in Namibia: implications for a glacial to Miller (Editor), Special Issue: Henno Martin Commemorative Volume. interglacial transition. Precambrian Research, 124, 69-85. Communications of the Geological Survey of Namibia, 12, 259-268. Zhou, C.M., Huyskens, M.H., Lang, X.G., Xiao, S.H. and Yin, Q.Z., 2019. Watts, A.B., Karner, G.D. and Steckler, M.S., 1982. Lithosphric flexure and the Calibrating the termination of Cryogenian global glaciations. Geology, evolution of sedimentary basins. Philosophical Transactions of the Royal 47, 251-254. Society, London, Series A, 305, 249-281. Zhou, G.C., Wang, Y.J., Huang, B.C., Dong, Y.P., Li, S.Z., Zhang, G.W. and Weber, K. and Ahrendt, H., 1983. Structural development of the Ugab Yu, S., 2018. Geological reconstruction of the East Asian blocks: From structural domain of the Northern Zone of the Damara Orogen. In: the breakup of Rodinia to the assembly of Pangea. Earth-Science H. Martin and F.W. Eder (Editors), Intracontinental Fold Belts. Springer- Reviews, 186, 262-286. Verlag, Heidelberg, 699-717. Wen, B., Evans, D.A.D., Anderson, R.P. and MCCausland, P.J.A., 2020. Late Ediacaran paleogeography of Avalonia and the Cambrian assembly of West Gondwana. Earth and Planetary Science Letters, 552, 116591, 1-12. Editorial handling: S. McCourt
420 SOUTH AFRICAN JOURNAL OF GEOLOGY