Late Proterozoic Supercontinent Research Articles

Relict 1.4 Ga oceanic crust in the Zambezi Valley, northern Zimbabwe: Evidence for Mesoproterozoic supercontinental fragmentation

The Archean cratons of southern Africa are separated from one another by younger orogenic belts. It is widely believed that these deformation belts developed entirely within continental crust, but in the Zambezi belt of northern Zimbabwe, relict oceanic crust, i.e., ophiolite, has now been discovered. The zircon age of a plagiogranite dike within the ophiolite—1393 ± 22 Ma—makes this the oldest dated remnant of oceanic crust in Africa. Presence of the ophiolite is direct evidence for the rifting and/or assembly of continental fragments within Africa. The age of the ophiolite is consistent with its being a remnant of sea floor formed during the episode of continental fragmentation that immediately preceded the Grenville orogeny, the global event that marked the coalescence of the Late Proterozoic supercontinent of Rodinia.

Palaeomagnetic study of Neoproterozoic glacial rocks of the Yangzi Block: palaeolatitude and configuration of South China in the late Proterozoic Supercontinent

Regional glaciation is recorded at two stratigraphic levels in the Neoproterozoic Sinian succession of the Yangzi (South China) Block. A palaeomagnetic study is reported here of the upper sequence (∼ 730-670 Ma) which contains red beds. An ‘A1’ component ( D I = 291 −57° , α 95 = 5.0°, Palaeopole 151.2°E, 0.2°N) is resolved at high unblocking temperatures and resides in specular haematite. A study of contemporaneous deformation structures suggests that this component was acquired at an early stage of lithification and yields a representative palaeolatitude (37°) for the glaciation. Lower blocking temperature magnetizations referred to as ‘A2’ ( D I = 297 −19° , α 95 = 7.6°, Palaeopole 171.8°E, 19.2°S) and ‘A3’ ( D I = 319 −1° , α 95 = 3.2°, Palaeopole 169.1°E, 41.8°S) are later overprints correlating with probable Late Precambrian or Cambrian palaeofields. In other regions, the ‘A’ magnetizations were found to be partially or completely overprinted by a Recent field and/or a ‘B’ remanence ( D I = 4 13° ); the latter correlates with a remagnetization widely recorded elsewhere in South China and is attributed to the Mesozoic Indosinian Orogeny. An ∼90° apparent polar wander (APW) swathe is identified from the Yangzi Block between ∼730-670 Ma and 540 Ma. It is not yet clear whether poles from older Sinian rocks record earlier magnetizations or were overprinted during this APW motion. Comparison of the Sinian-Cambrian palaeomagnetic record from South China with the contemporaneous record from Australia implies that the former block was located immediately to the north-west of Australia during these times. This reconstruction is compatible with Early Palaeozoic biogeographic data. Continuity of the ∼900 Ma Cathaysian-Yangzi suture with the ∼ 1000 Ma Albany-Fraser belt in Australia suggests an extension of this reconstruction back to the earlier part of Neoproterozoic times. A proposed location of South China adjacent to western North America (Li et al., 1995) does not conform with the palaeomagnetic data. No support is also found for the Rodinia reconstruction during the critical 750-550 Ma interval required by the stratigraphic correlation from which the reconstruction was originally derived (Jefferson, 1980). We conclude that the large-scale three-fold sedimentary cycle, which formed the basis for this reconstruction, resulted from global eustatic changes and cannot be used to infer close spatial proximity.

A Geologic History of the North-Central Appalachians; Part 2, the Appalachian Basin From the Silurian Through the Carboniferous

The north-central Appalachians occupy a critical position within the 3000+ km-long Appalachian orogen, lying southwest of the boundary between the central and northern Appalachians (CNAB). The one-billion-year-long history of tectonic activity in the north-central Appalachians includes the assembly and breakup of a late Proterozoic supercontinent, the creation and evolution of the Appalachian orogen during the Paleozoic, and the Mesozoic transformation of the active orogen into a passive margin during Pangea9s disassembly. An important part of the Middle and Late Paleozoic history is the formation and growth of the Appalachian basin, an enormous, elongate continental basin lying cratonward of the active Appalachian internides along Laurentia9s eastern margin. The Appalachian basin developed out of the Taconic orogeny, the second of the four orogenies that formed and modified the character of the Appalachian orogen. Prior to the Taconic orogeny, the eastern margin of Laurentia consisted of a broad carbonate shelf facing the Theic Ocean. The Taconic orogeny obduced various Theic components, including microcontinents, magmatic arcs, and accretionary prisms, onto the carbonate shelf. The resulting Taconic highlands formed a topographic barrier between Theia and the craton9s interior. Because tectonic activity in the internides continued more or less throughout the remainder of the Paleozoic, the Appalachian basin never had a direct connection with Theia. The coarse-grained molasse from the newly uplifted Taconic highland spread westward over most of the basin during the Early Silurian. Carbonate deposition gradually encroached eastward over the basin as the siliciclastic input from the southeast waned. A resurgence in the earliest Late Silurian, perhaps related to orogenesis in Newfoundland and the Maritimes, expanded the clastic wedge somewhat. Before long, however, carbonate deposition once again dominated most of the north-central basin for the remainder of the Silurian and into the Early Devonian. The Early-to-Middle Devonian Acadian orogeny began introducing siliciclastic material into the eastern part of the Appalachian basin, thereby ending the largely paralic environment that persisted from the Late Silurian. A number of deltas formed around local sediment-input centers during the Middle Devonian. Continued uplift and/or orogenesis must have continued into the Late Devonian because a vast amount of terrigenous sediment was introduced into the Appalachian basin to form the vast Upper Devonian Catskill delta. Although the principal tectonic activity appears to have centered in New England, the large volume of sediment input suggests that orogenesis may have extended southward to the north-central Appalachians. However, direct evidence of actual Acadian deformation and metamorphism is lacking at this latitude. The north-central Appalachian basin underwent a significant change during the Carboniferous. Prior to this time, the shoreline shifted laterally through transgressions and regressions largely as a function of sediment input and regional subsidence. In the Carboniferous, vertical movements in the basin became more important. During the Early Carboniferous, much of the Mauch Chunk delta was eroded in the central and western parts of the basin. At the end of the Early Carboniferous, an unconformity truncated progressively older rocks to the north toward New York. New sediment transport patterns and depositional environments within the basin during the Late Carboniferous probably reflect significant topographic and tectonic changes, not only in the hinterland, but in the basin itself, perhaps in conjunction with climatic changes. Extensive interfluvial swamps on a lower delta plain accumulated thick organic deposits which would become coal. This delta plain graded southwestward into tidal and marine environments. The Alleghany orogeny in the Early Permian interrupted deposition in much of the north-central Appalachian basin and profoundly altered its structure.

変成岩岩石学の現状と将来への展望 変成帯研究とテクトニクス

The author picks up the study topics of metamorphic rocks in consideration of the paradigm of plume tectonics. First of all, He refers to minerals which are considered to have derived from the transitional zone and the lower mantle, i.e., inclusions in diamond in kimberlite. A problem of transitional zone origin of the Alpe Arami peridotite is introduced. Subsequently, ultra high pressure (UHP) metamorphic rocks exhumed by continent-continent collision are also briefly introduced. In addition, he reviews a discussion on diamond of possible UHP origin in the New England Fold Belt (NEFB), Australia.The author emphasizes that tectonics of regional metamorphic belts in global scale relates closely to the formation and subsequent fragmentation of a Late Proterozoic supercontinent, Rodinia, and amalgamation forming new continents. Chronological study, especially by SHRIMP, is effective to estimate linkage among fragmented continental blocks, and an example in northern Japan is referred.Introduced is the structural studies on the metamorphic belts along the plate collision zones which reveal non-rigidness of the lithosphere. Active deformation in the mountains is explained by not only extrinsic force along the plate boundary but also intrinsic force (gravitational potential energy) acting on the continental lithosphere. Study on deformation of metamorphic rocks composing the lower crust is important to test the effect of the intrinsic force and to reveal the influences of regional surface subsidence behind the subduction zone and mountain building along the collision zones. Modelling by experimental work and computer simulation increase the weights in studies of tectonics of metamorphic belts.

A geologic history of the north-central Appalachians; Part 2, The Appalachian Basin from the Silurian through the Carboniferous

The north-central Appalachians occupy a critical position within the 3000+ km-long Appalachian orogen, lying southwest of the boundary between the central and northern Appalachians (CNAB). The one-billion-year-long history of tectonic activity in the north-central Appalachians includes the assembly and breakup of a late Proterozoic supercontinent, the creation and evolution of the Appalachian orogen during the Paleozoic, and the Mesozoic transformation of the active orogen into a passive margin during Pangea9s disassembly. An important part of the Middle and Late Paleozoic history is the formation and growth of the Appalachian basin, an enormous, elongate continental basin lying cratonward of the active Appalachian internides along Laurentia9s eastern margin. The Appalachian basin developed out of the Taconic orogeny, the second of the four orogenies that formed and modified the character of the Appalachian orogen. Prior to the Taconic orogeny, the eastern margin of Laurentia consisted of a broad carbonate shelf facing the Theic Ocean. The Taconic orogeny obduced various Theic components, including microcontinents, magmatic arcs, and accretionary prisms, onto the carbonate shelf. The resulting Taconic highlands formed a topographic barrier between Theia and the craton9s interior. Because tectonic activity in the internides continued more or less throughout the remainder of the Paleozoic, the Appalachian basin never had a direct connection with Theia. The coarse-grained molasse from the newly uplifted Taconic highland spread westward over most of the basin during the Early Silurian. Carbonate deposition gradually encroached eastward over the basin as the siliciclastic input from the southeast waned. A resurgence in the earliest Late Silurian, perhaps related to orogenesis in Newfoundland and the Maritimes, expanded the clastic wedge somewhat. Before long, however, carbonate deposition once again dominated most of the north-central basin for the remainder of the Silurian and into the Early Devonian. The Early-to-Middle Devonian Acadian orogeny began introducing siliciclastic material into the eastern part of the Appalachian basin, thereby ending the largely paralic environment that persisted from the Late Silurian. A number of deltas formed around local sediment-input centers during the Middle Devonian. Continued uplift and/or orogenesis must have continued into the Late Devonian because a vast amount of terrigenous sediment was introduced into the Appalachian basin to form the vast Upper Devonian Catskill delta. Although the principal tectonic activity appears to have centered in New England, the large volume of sediment input suggests that orogenesis may have extended southward to the north-central Appalachians. However, direct evidence of actual Acadian deformation and metamorphism is lacking at this latitude. The north-central Appalachian basin underwent a significant change during the Carboniferous. Prior to this time, the shoreline shifted laterally through transgressions and regressions largely as a function of sediment input and regional subsidence. In the Carboniferous, vertical movements in the basin became more important. During the Early Carboniferous, much of the Mauch Chunk delta was eroded in the central and western parts of the basin. At the end of the Early Carboniferous, an unconformity truncated progressively older rocks to the north toward New York. New sediment transport patterns and depositional environments within the basin during the Late Carboniferous probably reflect significant topographic and tectonic changes, not only in the hinterland, but in the basin itself, perhaps in conjunction with climatic changes. Extensive interfluvial swamps on a lower delta plain accumulated thick organic deposits which would become coal. This delta plain graded southwestward into tidal and marine environments. The Alleghany orogeny in the Early Permian interrupted deposition in much of the north-central Appalachian basin and profoundly altered its structure.

Laurentia, Australia, and Antarctica as a Late Proterozoic supercontinent: Constraints from isotopic mapping

The reconstruction of Laurentia, Australia, and Antarctica into a Proterozoic supercontinent is evaluated by analyzing the fit of Precambrian provinces defined by isotopic and geochronologic mapping. The analysis is complicated by allochthonous segments of the Antarctic and eastern Australian margins. Removal of the allochthonous provinces produces a closer fit of the continents; there is a match of Early Proterozoic basement between southwestern Laurentia and the only exposure of craton known from the paleo-Pacific margin of Antarctica. In addition, western Laurentia is brought closer to the Australian Gawler block, consistent with provenance interpretations of the Belt Supergroup. Removal of the allochthonous provinces by right-lateral translation relative to the Antarctic craton margin places them in a pre-750 Ma position where they could be southwestward extensions of the Yavapai-Mazatzal and Grenville provinces of southern Laurentia. This modified reconstruction leads to a prediction of extensive Archean basement in Antarctica between the South Pole and Victoria Land, a prediction partly borne out by Archean rocks in the Miller Range of the Transantarctic Mountains; it also predicts the presence of 1.4Ga rapakivi granites in the Transantarctic Mountains basement. This configuration implies assembly of the Australia-Antarctica Gondwana margin by terrane accretion following, or accompanied by, left-lateral translation. This is compatible with a tectonic regime of clockwise rotation of Laurentia relative to Australia and Antarctica after rifting. Thus, the proposed supercontinent, with some modifications, has potential for explaining several aspects of the pattern of Precambrian provinces in the three continents.

Earth's glacial record and its tectonic setting

Earth's glacial record and its tectonic setting

Supercontinent cycles and the distribution of metal deposits through time

Systematic temporal variations in the distribution of several important groups of metal deposits reflect the cyclic aggregation and breakup of large continents. In particular, metal deposits that form in continental basins or are associated with anorogenic magmatism were extraordinarily abundant in the Middle Proterozoic (2.0 to 1.4 Ga), corresponding to the assembly of the first large continents. It is important to note that peaks in the abundance of continental metal deposits also coincide with a postulated Late Proterozoic supercontinent (1.0 to 0.8 Ga) and the near maximum extent of Pangea. In contrast, metal deposits that form, or are preserved, in convergent-margin orogens were most abundant in the late Archean (2.9 to 2.6 Ga), corresponding to a period of high global heat flow and rapid stabilization of continental crust, and the past 200 m.y., which corresponds to the present tectonic cycle. Similar mineralization was also present, albeit less abundant, in Early Proterozoic orogens, as well as in Late Proterozoic and Phanerozoic orogens. Future metals exploration may benefit from the application of sequence stratigraphy, as used by the oil industry, to recognize such cycles, particularly in the Precambrian rock record.

Did the Breakout of Laurentia Turn Gondwanaland Inside-Out?

Comparative geology suggests that the continents adjacent to northern, western, southern, and eastern Laurentia in the Late Proterozoic were Siberia, Australia-Antarctica, southern Africa, and Amazonia-Baltica, respectively. Late Proterozoic fragmentation of the supercontinent centered on Laurentia would then have been followed by rapid fan-like collapse of the (present) southern continents and eventual consolidation of East and West Gondwanaland. In this scenario, a pole of rotation near the Weddell Sea would explain the observed dominance of wrench tectonics in (present) east-west trending Pan-African mobile belts and subduction-accretion tectonics in north-south trending belts. In the process of fragmentation, rifts originating in the interior of the Late Proterozoic supercontinent became the external margins of Paleozoic Gondwanaland; exterior margins of the Late Proterozoic supercontinent became landlocked within the interior of Gondwanaland.

Supercontinent model for the contrasting character of Late Proterozoic orogenic belts

Two fundamentally different types of orogenic belts may reflect the accretion and breakup of a Late Proterozoic supercontinent. Interior orogens (e.g., trans- Saharan fold belts) lie within the supercontinent after its amalgamation. Orogenic activity commenced with ca. 850-800 Ma Cordilleran-type subduction associated with contraction of interior oceans and terminated in ca. 650-600 Ma continent-continent collision and the amalgamation of an Afro-Brazilian supercontinent. Orogenic activity produced abundant calc-alkalic granitoid magmatism, crustal thickening, large-scale thrusting, uplift and exposure of medium-to high-grade metamorphic rocks, and regional angular unconformities with postorogenic sequences. In contrast, peripheral orogens (e.g., Avalonian-Cadomian belt, Arabian shield) lie at the extremity of the supercontinent following its amalgamation. Orogenic activity commenced with ca. 820-800 Ma subduction in an exterior, expanding ocean that generated a diverse assemblage of arcs and back-arc basins as the plate retreated from the subducting slab. Voluminous ca. 600 Ma ensialic tectonothermal activity in peripheral orogens may reflect renewed subduction at the periphery of the supercontinent following its amalgamation and the destruction of interior oceans. Peripheral orogenic activity produced synorogenic, low-grade volcanic-sedimentary successions, inter-arc and intra-arc rifts, localized and predominantly strike-slip deformation, limited uplift, and only local unconformities with postorogenic successions. Basin closure and termination of peripheral orogens may reflect supercontinent breakup and dispersal.

Exotic metamorphic terranes in the Caledonides: Tectonic history of the Dalradian block, Scotland

Research Article| November 01, 1991 Exotic metamorphic terranes in the Caledonides: Tectonic history of the Dalradian block, Scotland B. J. Bluck; B. J. Bluck 1Department of Geology and Applied Geology, University of Glasgow,Glasgow G12 8QQ, Scotland Search for other works by this author on: GSW Google Scholar T. J. Dempster T. J. Dempster 1Department of Geology and Applied Geology, University of Glasgow,Glasgow G12 8QQ, Scotland Search for other works by this author on: GSW Google Scholar Author and Article Information B. J. Bluck 1Department of Geology and Applied Geology, University of Glasgow,Glasgow G12 8QQ, Scotland T. J. Dempster 1Department of Geology and Applied Geology, University of Glasgow,Glasgow G12 8QQ, Scotland Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1991) 19 (11): 1133–1136. https://doi.org/10.1130/0091-7613(1991)019<1133:EMTITC>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation B. J. Bluck, T. J. Dempster; Exotic metamorphic terranes in the Caledonides: Tectonic history of the Dalradian block, Scotland. Geology 1991;; 19 (11): 1133–1136. doi: https://doi.org/10.1130/0091-7613(1991)019<1133:EMTITC>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract The Dalradian block, a part of the Precambrian metamorphic basement of Scotland, is thought to be exotic to Laurentia, having a provenance in Gondwana. In contrast to the rest of the Laurentian margin, which from ca. 700 to 530 Ma was undergoing extension, the Dalradian block was undergoing severe compression ca. 590 Ma. At the time of splitting of the Late Proterozoic supercontinent, both Gondwana and Laurentia shared a common history of extension; however, at ca. 670 Ma Gondwana converted to a destructive margin and underwent compression, whereas Laurentia remained in extension and passive to 500-510 Ma. The Dalradian block had two major phases of metamorphism and deformation, one in Gondwana, and the other in Laurentia. The second phase of classical Barrovian metamorphism may have been produced by thickening due to emplacement of ophiolitic and other nappes, rather than the earlier internal nappe structures. Late-stage ductile folding in the Moine basement to the north may be related to the final emplacement of the Dalradian block onto Laurentia. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Gondwana facies started when Gondwanaland merged in Pangea

The late Paleozoic and early Mesozoic Gondwana sequence of peninsular India and its equivalents in the present southern continents were deposited during the merging of the continents in Pangea and are a facies of the Pangean super-sequence distinguished by late Carboniferous and Early Permian glacial deposits and a provincial biota, in particular the Glossopteris flora. The Gondwana facies owes its distinctive character not to its isolation in Gondwanaland, which had merged in Pangea in the late Paleozoic, but to its mid- to high-latitude depositional environment in the Southern Hemisphere. As a free-standing continental assemblage, Gondwanaland started in the earliest Paleozoic at the breakup of a Late Proterozoic supercontinent and ended at the very inception of the Gondwana facies.

Breakup of a supercontinent between 625 Ma and 555 Ma: new evidence and implications for continental histories

A method developed recently for constructing tectonic subsidence curves in early Paleozoic miogeoclines has produced new evidence for the breakup of a late Proterozoic supercontinent. Tectonic subsidence analyses in miogeoclines of eastern and western North America, northwestern Argentina, the Middle East and northwestern Australia limit the timing of the continental breakup to between 625 and 555 Ma. These results refine the implications of a much broader range of radiometric ages of rift-related igneous rocks and biostratigraphic ages of the transition from active extension to passive subsidence in miogeoclines. The recognition of the timing and extent of rifting has led to testable hypotheses for latest Proterozoic and early Paleozoic continental histories. Breakup and onset of drift along an extensive system of continental fractures within a relatively short period of time would generate a large amount of young ocean floor, thereby reducing the volume of the global ocean basin and causing a sea level rise. Maximum reduction of ocean basin volume would postdate the time of breakup, probably by about 70 m.y., placing the transgressive peak at a time not older then about 510–520 Ma. That age agrees well with the time of maximum flooding on the continents close to the end of the Cambrian. Restriction of the breakup to between 625 and 555 Ma reduces the time gap between an essentially intact late Proterozoic supercontinent and the oldest reliable paleomagnetic reconstruction of the dispersed continents at about 560 Ma. A continental reconstruction produced by rotating Laurentia and Baltica into Gondwana a minimum distance from the 560 Ma position is consistent with limited geologic data. However, that reconstruction places Laurentia and Baltica in low latitudes which is difficult to reconcile with the absence of evaporites in syn-rift complexes in both continents.

Proterozoic plate tectonics in Canada with emphasis on evidence for a Late Proterozoic rifting event

Several Early Proterozoic fold belts in the Canadian shield have been interpreted in terms of plate tectonic processes. The most impressive evidence comes from those preserved on the margins of Archaean cratons such as the Wopmay orogen and the Penokean fold belt. There are striking similarities in the stratigraphic successions of many widely separated Early Proterozoic fold belts within the Canadian shield. Most of these are currently best interpreted in terms of some modified version of plate tectonics. Post-Grenville rocks contain several independent lines of evidence that support a major episode of continental fragmentation. Stratigraphic and sedimentological evidence from the Cordilleran region records a dramatic change from widespread development of essentially platformal marine sediments (L. Mackenzie Mountains Supergroup) through rift-related evaporites and clastics (U. Mackenzie Mountains Supergroup) to a largely resedimented sequence (Ekwi or Windermere Supergroup) that has been interpreted as a continental margin facies. A closely comparable succession of facies can be documented in other parts of the world but perhaps the closest analogue is found in S.E. Australia. It has been suggested that these two regions may formerly have been juxtaposed and represent the sundered fragments of a Late Proterozoic supercontinent. Relevant to these interpretations are geochemical data such as δ 34S values from Late Proterozoic evaporites and 87Sr/ 86Sr measurements from carbonates, and processes involved in precipitation of glacially-related iron-formations such as those of the Rapitan Group in the N. Cordillera. Preservation of Late Proterozoic ophiolites in North Africa provides additional evidence of plate tectonic processes at that time. These several lines of evidence all suggest a significant period of Late Proterozoic continental breakup which produced many of the continental margins that were and are the loci of subsequent Phanerozoic orogenic activity.

Significance of major Proterozoic high grade linear belts in continental evolution

Major Proterozoic high grade linear belts are broadly conformable and sub-parallel to Archaean trends. Some are marginal to Archaean cratons, others intracratonic. All belong to a major set extending across the middle to late Proterozoic supercontinent. They are broadly contemporaneous with hairpin bends of polar wander curves, and some controlled igneous activity. Some are intracontinental structures developed in Proterozoic times when the deeper levels of continental masses underwent internal movement without loss of general coherence.