Rodinia - an overview | ScienceDirect Topics

2.3 The Break-up of Rodinia

The Pharusian microplates, which exhibit a wide variety of oceanic island arc suites of sedimentary and volcanic rocks, are now preserved as accreted terranes in the Touareg shield of Algeria and Mali. The tectonic events which produced these rocks began at about 880 Ma and persisted until about 550 Ma. Evidence from deep oil wells shows that rocks belonging to this assemblage form basement across much of northern Libya, including the Ghadamis Basin, northern Sirt Basin and Cyrenaica Platform (Figure 2.5).⁶

The period from 700 to 500 Ma was marked by the final break-up of Rodinia and the reassembly of the component plates into a new supercontinent which was given the name Pannotia by Powell. The magnitude of this reorganisation cannot be over-emphasised. In effect Rodinia was turned inside out. During this phase the entire assemblage of ‘ eastern ’ Rodinia was rotated in an anticlockwise direction and translated relatively ‘eastwards’, whereas ‘western’ Rodinia was rotated clockwise and displaced relatively towards the ‘ west ’(Figure 2.2).⁷

Abstract

Rodinia is the purported supercontinent that existed in early Neoproterozoic time. Most currently viable Rodinia models, that is, consistent with both the geological/geochemical record and geophysical constraints from paleomagnetism and reasonable plate kinematics, include Laurentia in a central position, flanked on nearly all sides by about 6–8 other cratons. Details of the history of Rodinia formation depend critically on the ages of orogens within those bounding cratons, some of which might have closed as late as ~900 Ma. Rodinia’s initial breakup likely coincided with voluminous large igneous province emplacement at ~800 Ma, lasting until final separations as young as ~600 Ma.

The Rodinian-era paleomagnetic database of reliable poles is growing steadily but still requires augmentation for most cratons. Enough poles are available in key intervals (especially c.1110 and 760 Ma) that kinematic models can be constructed that plausibly evolve toward better-established Paleozoic reconstructions. A new synthesis-based model of Rodinia assembly and breakup is briefly introduced herein, which includes Tarim craton in a “missing link” role between Laurentia and proto-Australia, as well as South China and India in their recently proposed inverted orientation near the supercontinent’s southern paleo-margin.

Kinematic transitions between successive supercontinents Nuna, Rodinia, and Pangea are each postulated to contain elements of both “introverted” and “extroverted” style, depending on the paleogeographic sectors of the supercontinents and distinct temporal stages of evolution that produce megacontinents prior to supercontinents. Both of these components can be rectified within an overall mantle-convective framework of “orthoversion” whereby each supercontinent fully assembles within the subduction-girdle ~90 degrees from the centroid of its predecessor.

12.5.2.6 Kalahari’s drift following Rodinia breakup and Gondwana amalgamation

Rodinia breakup is heralded in the Kalahari Craton by the emplacement of the c.0.80 Ga Gannakouriep and c.0.72 Ga Mutare dyke swarms during northward drift toward mid-to-high latitudes. The Pan-African orogenic belts developed between 0.59 and 0.54 Ga (Oriolo and Becker, 2018). This was followed by drift back toward the equator during the latter part of the Neoproterozoic allowing the Kalahari Craton (as part of East Gondwana) to end up in the southern hemisphere in the Cambrian Period (Fig. 12.5). Several Neoproterozoic glacial events that are preserved in Namibia occurred during this equator-ward drift and are low-latitude glaciations.

Rodinia

Neoproterozoic palaeogeography and H.O.G.

Rodinia (Fig. 3.11-3a) was thought to have formed largely during the 1100–1000 Ma Grenvillian orogeny (Dalziel, 1997) although parts of the supercontinent may have coalesced earlier (see also section 3.10). The supercontinent began to break up at c. 800 Ma (Li et al., 1999, 2002) with the arrival of a mantle plume beneath south China (along the present-day western margin of Laurentia). Frimmel et al. (2001) (section 3.10) noted that extensive igneous activity in South Africa (Richtersveld Igneous complex) was broadly coeval with the south China event. They proposed that a c. 800 ± 60 Ma megaplume stretched from S. Africa through Australia–south China and northernmost Laurentia (see also Park et al., 1995; Wingate et al., 1998; Wingate and Giddings, 2000; Foden et al., 2002). If these estimates are correct, then the mantle plume(s) developed beneath the Rodinia supercontinent some 200–300 My after its formation. This timing is in agreement with one of the proposals by Honda et al. (2000).

Unfortunately, we have difficulty estimating minimum plate velocities during the initial breakup of the supercontinent due to a (near-complete) lack of palaeomagnetic data during the 750–600 Ma interval (see Meert and Powell, 2001). The model given here would predict a short “burst” of rapid plate motion, but its testing must await further refinement of the palaeomagnetic database.

The supercontinent was not fully disaggregated during this first rifting phase and it was followed some 200 million years later by a second pulse of plume activity (the so-called Sept Îles plume; Higgins and van Breeman, 1998). The presence of this plume has clear manifestations in eastern Laurentia and possible manifestations in Baltica (Bingen et al., 1998; Meert et al., 1998), but there is no clear evidence of the plume in the South American blocks. However, there is some controversy regarding the relationship between the South American cratons and eastern Laurentia (Tohver et al., 2002; Meert and Torsvik, in review).

Palaeomagnetic data from Laurentia during the 570–510 Ma interval is estimated conservatively to give drift rates of 16–20 cm yr^− 1 (Meert, 1999). Palaeomagnetic data from Gondwana show rapid motion of western Gondwana over the pole from c. 550–500 Ma (c. 24 cm yr^− 1 Meert et al., 2001) although the magnitude of this motion may be reduced significantly if non-dipolar fields are considered (Torsvik and Van der Voo, in press).

Rifting of Rodinia

Supercontinent Rodinia formed 1.2–1 billion years ago (Ga) as a product of the worldwide Grenvillian Orogeny. The continent remained intact for ∼300 million years (My) and then rifted apart at ∼750 Ma in western and north-eastern North America, but failed rifting occurred at ∼735 Ma in the southern and central Appalachians. Failed rifting, however, produced the alkalic A-type Crossnore plutonic–volcanic suite; the Grandfather Mountain and Mount Rogers Formation marine, non-marine, and glaciogenic sedimentary and bimodal volcanic rocks in North Carolina, Tennessee, and Virginia; and the Robertson River igneous complex in central Virginia. Successful rifting of Rodinia along the entire southern-central Appalachian margin occurred at ∼565 Ma, with basins that deposited the Ocoee Supergroup in Tennessee, North Carolina, and Georgia, and the Catoctin volcanic–sedimentary assemblage in Virginia. Neither of these assemblages is physically connected, because initial rifting created an irregular margin in south-eastern Laurentia, leaving basement highs that separated rift basins.

Deposition of the Ocoee Supergroup locally reached thicknesses exceeding 15 km, with most of the thickness contained in the Great Smoky Group. The Ocoee Supergroup contains three groups: (1) the Snowbird Group, which rests unconformably on Grenvillian basement, (2) the Great Smoky Group, which nowhere has been observed in direct contact with basement rocks and is faulted onto the Snowbird Group rocks, and (3) the Walden Creek Group, which conformably overlies both the Great Smoky Group and the Snowbird Group, revealing an extraordinarily complex relationship between the components of the Ocoee Supergroup. The Snowbird Group consists of immature basal sandstone overlain by much cleaner quartz arenite to arkosic sandstone, then a pelitic unit. The Great Smoky Group consists of a rapidly deposited deep-water sequence of immature greywacke and pelite (some of which was deposited in an anoxic environment), minor amounts of cleaner sedimentary rocks, and polymictic vein quartz-dominated conglomerate that also contains quartzite, sandstone, granitoid, black shale rip-ups, and variably textured limestone and dolostone clasts. The Walden Creek Group consists of banded chlorite–sericite slate that contains minor amounts of limestone overlain by shale, clean sandstone, and limestone. The latter unit has yielded soft-bodied wormlike fossils, and possible ostracodes and inarticulate brachiopods, indicating a Cambrian (probably Tommotian) age. Coarse polymictic vein quartz-dominated conglomerate facies also occur within this unit, and again the clasts are dominated by vein quartz; several textural and compositional variations of limestone and dolomite; and quartzite, sandstone, and black shale rip-ups. Many of the conglomerates clearly were deposited in channels; armoured mudballs have been observed in at least one palaeochannel. Though the Ocoee Supergroup thins gradually southward to near Cartersville, Georgia, its thickness rapidly decreases northward from its maximum of 15 km in the Great Smoky Mountains National Park, to zero south-east of Johnson City, Tennessee.

In central Virginia, the Ocoee-equivalent ∼565-My-old Catoctin Formation consists of basalt and rhyolite, with some interlayered clastic sedimentary rocks that are locally underlain by an older suite of immature rift-related sedimentary rocks (Snowbird Group equivalent?). East of the Blue Ridge anticlinorium in northern North Carolina and Virginia is a sequence of distal, deeper water clastic sedimentary and rift-related volcanic rocks, the Ashe–Alligator Back-Lynchburg sequence. More distal eastward and south-eastward equivalents of these metasedimentary and metavolcanic rocks (Ashe–Tallulah Falls–Sandy Springs) have been recognized in the eastern Blue Ridge and Inner Piedmont from the Carolinas to Alabama. They are overlain by Cambrian–Ordovician(?) metasedimentary rocks (Candler, Chauga River), and by Middle Ordovician(?) mid-oceanic ridge basalt-arc volcanic rocks (Slippery Creek–Poor Mountain–Ropes Creek). Farther east in the Virginia Piedmont is a sequence of felsic–mafic volcanic rocks from ∼470 Ma (Chopawamsic) that were intruded by plutons at ∼455 Ma, then overlain by fossiliferous Late Ordovician (Ashgill) fine-grained clastic rocks comprising the Chopawamsic Terrane.

The Lower Cambrian Chilhowee Group was deposited on the Laurentian margin during the rift-to-drift transition, and consists of upward-maturing alternating sandstone and shale units. The lowest unit consists of immature sandstone and greywacke with some basalt. The upper part of the Chilhowee Group was probably deposited along the open-ocean margin, because it grades upward into the first successful carbonate bank assemblage. Both the Chilhowee Group and the overlying Shady (–Tomstown–Dunham) Dolomite are continuous throughout the Appalachian margin.

2.4 The Pan-African Orogeny and the Assembly of Pannotia

The Pannotia super-continent had a relatively brief existence. During the earliest Palaeozoic it broke apart along the lines of the Neoproterozoic sutures, and Laurentia, Baltica, and Siberia became detached to form separate entities, which remained discrete for the next 200 million years. The remaining continental assemblage, at this time extending from the South Pole to about 60° south and comprising Africa, Antarctica, South America, Australia and India, is named Gondwana, after a region in India where the distinctive palaeofloral assemblage which characterises it was first described (Fig. 2.3).⁴

Breakup of Rodinia and Neoproterozoic to Mid-Paleozoic Sedimentation

The breakup of Rodinia was followed by development of a thick wedge of Neoproterozoic through mid-Paleozoic continental terrace deposits along the Cordilleran and Appalachian margins. In what is now the Canadian Cordillera, rifting began at ~ 750 Ma and evolved into a Neoproterozoic passive margin where the Windermere Supergroup was deposited. In the Southern Cordillera initial rifting was incomplete, and only during a second rifting event was the rift-to-drift transition achieved. Tectonic subsidence studies indicate that the drift phase in the U.S. Cordillera did not occur until the latest Neoproterozoic or earliest Cambrian (~ 600–555 Ma). Nevertheless, Neoproterozoic clastic deposits, including glacial diamictite, can be traced from the Mackenzie Mountains in the Canadian Cordillera to the Death Valley region, southern California. The Neoproterozoic rocks in the Southern Cordillera are considered rift deposits that accumulated in isolated basins, but by Early Cambrian a continuous, Atlantic-type, passive margin existed virtually the length of the western North American Cordillera.

The Neoproterozoic deposits were the initial stratigraphic units of an enormous wedge of chiefly clastic and carbonate rocks that accumulated along the rifted, western margin of the Southern Cordillera through Late Devonian time. This wedge of continental margin deposits is often referred to as the ‘Cordilleran miogeocline,’ and it reached ~ 10 000 m in total thickness. The miogeocline is separated from a partially equivalent, but considerably thinner, cratonic sequence by the ‘Wasatch line,’ interpreted as a hinge line in the depositional framework of the Southern Cordillera. This fundamental boundary is also interpreted as the eastern limit of Neoproterozoic, syndepositional faulting related to initial rifting of Rodinia in the Southern Cordillera. The Phanerozoic cratonic sedimentary sequence is characterized by disconformities and in some cases complete periods are unrepresented (e.g., the Silurian over most of Wyoming). Subsequently, the Wasatch line represents an important boundary during Pennsylvanian-Permian basin development (e.g., Oquirrh Basin), coincides with a regional ramp during foreland fold-and-thrust belt development, and is the approximate eastern margin of the Cenozoic, extensional Basin and Range Province. Furthermore, a segment of the Intermountain Seismic Belt follows the Wasatch line.

Breakup of Rodinia, and Neoproterozoic to Mid-Palaeozoic Sedimentation

The breakup of Rodinia was followed by development of a thick wedge of Neoproterozoic through mid-Palaeozoic continental terrace deposits along the Cordilleran and Appalachian margins. In what is now the Canadian Cordillera, rifting began ∼750 Ma and evolved into a Neoproterozoic passive margin where the Windermere Supergroup was deposited. In the Southern Cordillera, initial rifting was incomplete, and only during a second rifting event was the rift-to-drift transition achieved. Tectonic subsidence studies indicate that the drift phase in the US Cordillera did not occur until the latest Neoproterozoic or earliest Cambrian (∼600–555 Ma). Nevertheless, Neoproterozoic clastic deposits, including glacial diamictite, can be traced from the Mackenzie Mountains in the Canadian Cordillera to the Death Valley region in southern California. The Neoproterozoic rocks in the Southern Cordillera are considered rift deposits that accumulated in isolated basins, but by the Early Cambrian, a continuous, Atlantic-type, passive margin existed virtually the length of the western North American Cordillera.

The Neoproterozoic deposits were the initial stratigraphic units of an enormous wedge of chiefly clastic and carbonate rocks that accumulated along the rifted, western margin of the Southern Cordillera through Late Devonian time. This wedge of continental margin deposits is often referred to as the ‘Cordilleran Miogeocline’, and it reached ∼10 000 m in total thickness. The miogeocline is separated from a partially equivalent, but considerably thinner, cratonic sequence by the ‘Wasatch Line’, interpreted as a hinge line in the depositional framework of Southern Cordillera. This fundamental boundary is also interpreted as the eastern limit of Neoproterozoic, syndepositional faulting related to initial rifting of Rodinia in the Southern Cordillera. The Phanerozoic cratonic sedimentary sequence is characterized by disconformities and in some cases complete periods are unrepresented (e.g., the Silurian over most of Wyoming). Subsequently, the Wasatch Line represents an important boundary during Pennsylvanian–Permian basin development (e.g., Oquirrh Basin), coincides with a regional ramp during foreland fold-and-thrust belt development, and is the approximate eastern margin of the Cenozoic Basin and Range extensional province. Furthermore, a segment of the Intermountain seismic belt follows the Wasatch Line.

Rodinia

Rodinia began to fragment at 780 Ma with the separation of India from Australia and East Antarctica, followed by the separation of South China from Laurentia-Australia by 750 Ma (Fig. 7.18). Although rifting between Amazonia and Laurentia may have begun about the same time, fragmentation along this boundary was not complete until about 600 Ma. At this same time, cratons in western Gondwana were amalgamating, and thus fragmentation of one supercontinent coincided with assembly of another supercontinent. Although most fragmentation occurred between 750 and 650 Ma, the opening of the Iapetus Ocean began about 600 Ma with the separation of Baltica-Laurentia-Amazonia. In addition, small continental blocks, such as Avalonia-Cadomia and several blocks from western Laurentia, were rifted away as recently as 600–550 Ma.