Gondwana

The designation Gondwana for the southern supercontinent has both a biostratigraphic and an etymological history. Key palaeobiogeographic inferences about past continental connections rested on congruent distributions of several Permian–Triassic fossil assemblages across now-separated regions. Those co-occurring fossil groups, preserved within characteristic Permian–Triassic sedimentary successions, provided the temporal and lithostratigraphic framework that allowed geologists to correlate distant terranes and to argue for former physical continuity (initially interpreted by some as land bridges and later as continental drift).

Etymologically, the term traces to the Indian toponym Gondwana, itself derived from the Sanskrit goṇḍavana, meaning “forest of the Gonds.” H. B. Medlicott introduced Gondwana into geological usage in 1872 to denote the specific Permian–Triassic sedimentary sequences that bear the fossils central to these reconstructions. Eduard Suess subsequently adopted the name for the southern supercontinent, thereby extending a regional place-name to a global palaeogeographic entity. In the literature a semantic distinction is sometimes observed—“Gondwanaland” is used by some authors to separate the concept of the large palaeocontinental mass from the local Indian toponym and its regional applications.

The assembly of Gondwana was a protracted, multi‑stage process extending through the Neoproterozoic into the early Paleozoic. Sparse palaeomagnetic constraints complicate precise palaeogeographic reconstructions, so the array of collisional and accretionary events is commonly subsumed under the Pan‑African orogeny. Nonetheless, integrated geological and industrial datasets resolve several principal orogenic provinces and a sequence of suturing events that together built the Gondwanan supercontinent.

A major Neoproterozoic orogenic zone is the Mozambique Belt (formed c. 800–650 Ma), long interpreted as the principal suture between East Gondwana (India, Madagascar, Antarctica, Australia) and West Gondwana (Africa, South America). More broadly, three principal orogenic systems can be distinguished by timing and tectonic role: the East African Orogeny, the Kuunga Orogeny (with the Malagasy orogeny as a southern expression), and the Brasiliano orogeny. Each operated on different Gondwanan sectors and at partly overlapping times to weld continental fragments together.

The East African Orogeny records an earlier collisional phase (roughly 800–650–650 Ma) followed by a post‑collisional extensional and metamorphic episode from about 620 to 550 Ma; during this interval the Arabian‑Nubian Shield became affixed to eastern Africa, particularly in the Kenya–Tanzania region. The Kuunga Orogeny (also invoked as the Pinjarra event in some areas) produced intense collisional metamorphism mainly between c. 570 and 530 Ma and corresponds to the final docking of Australia and East Antarctica with other eastern Gondwanan blocks; India reached its final Gondwanan position by about c. 550 Ma, a movement closely tied to Kuunga‑age deformation. The Malagasy orogeny (c. 550–515 Ma) documents collision of Neoproterozoic India with the pre‑existing Azania and Congo–Tanzania–Bangweulu composite, producing suturing along the Mozambique Belt. In the west, the Brasiliano orogeny (c. 660–530 Ma) comprises the successive collisions of South American and African cratons that completed much of western Gondwana’s amalgamation.

Palaeogeographic reconstructions indicate that the Mozambique Ocean separated the Congo–Tanzania–Bangweulu Block from a Neoproterozoic Indian realm (including India proper, the Antongil Block of eastern Madagascar, the Seychelles, and East Antarctic complexes). The Azania continent—now represented by central Madagascar, parts of the Horn of Africa and fragments in Arabia and Yemen—sat as an intra‑oceanic block within the Mozambique Ocean. By c. 600 Ma much of western Gondwana had been assembled, but Australia and East Antarctica remained detached from India, eastern Africa and the Kalahari craton. By c. 550 Ma India had docked into its Gondwanan position (triggering Kuunga deformation), while contemporaneous collisions of Kalahari with Congo and Rio de la Plata closed the Adamastor Ocean. Final closure of the Mozambique Ocean between c. 540 and 530 Ma brought India into proximity with the Australia–East Antarctica composite; at about this time North and South China also lay near Australia, indicating complex far‑field interactions along evolving Gondwanan margins.

Overall, the eastern components of Gondwana were accreted through a succession of orogenic events between c. 750 and 530 Ma: initial collision of the Arabian‑Nubian Shield with eastern Africa occurred c. 750–620 Ma, followed by the incorporation of Australia and East Antarctica during the Kuunga interval (c. 570–530 Ma). Complementing these suturing episodes, a long‑lived peripheral belt—the Terra Australis Orogen—extended for roughly 18,000 km along Gondwana’s western, southern and eastern margins. Remnants of proto‑Gondwanan Cambrian arc systems derived from this orogen are preserved in eastern Australia, Tasmania, New Zealand and Antarctica; these arcs once formed an essentially continuous chain, albeit with contrasting subduction polarities between the Australian–Tasmanian and New Zealand–Antarctic sectors.

Peri‑Gondwana development: Paleozoic rifts and accretions

During the Paleozoic, a complex history of rifting, ocean opening and terrane accretion along Gondwana’s northern margin produced many continental fragments that were ultimately sutured to Eurasia. Although numerous microcontinents and terranes joined the growing Eurasian landmass, the Precambrian or Cambrian affinities of several blocks remain ambiguous; notable examples are the so‑called Kazakh and Mongolian terranes, which were assembled into Kazakhstania by the late Silurian but whose original positions relative to Gondwana are unresolved.

Western peri‑Gondwanan history is exemplified by Armorica (now much of France), which separated from Gondwana in the Early Paleozoic as the Rheic Ocean closed in its forefield while the Paleo‑Tethys opened to its rear. Comparable Precambrian lithologies on the Iberian Peninsula indicate Iberia’s Gondwanan origin prior to its detachment and deformation into an orocline during the Variscan orogeny around the Carboniferous–Permian boundary.

Southeast Asia records a staged dispersal of Gondwanan fragments in three major rifting episodes that opened successive ocean basins—Paleo‑Tethys, Meso‑Tethys and Neo‑Tethys—and drove progressive terrane migration and accretion to Eurasia from the Devonian through the Cretaceous. In the Devonian (Phase 1) blocks such as North China, South China, Tarim and Quidam (northwestern China) rifted from Gondwana and left the nascent Paleo‑Tethys behind them; these terranes were reincorporated into the Asian margin in Late Devonian and Permian episodes of suturing.

Phase 2, spanning the Late Carboniferous–Early Permian through the Early Jurassic, involved the separation of the Cimmerian terranes and formation of the Meso‑Tethys. Key fragments including Sibumasu and Qiangtang detached during the Late Permian and were progressively welded onto the southern Asian margin through the Early Jurassic. Phase 3, from the Late Triassic–Late Jurassic into the Cretaceous, saw rifting of Lhasa, Burma and Woyla and the opening of the Neo‑Tethys; their collisions with Asia occurred diachronously, with Lhasa accreting in the Early Cretaceous and Burma and Woyla in the Late Cretaceous.

Throughout much of the Paleozoic Gondwana’s northern margin behaved as a broadly passive margin. The Early Permian expansion of the Neo‑Tethys established a longitudinal procession of terranes that were translated northward and later deformed by Himalayan‑scale orogenesis. From west to east these include the Taurides (southern Turkey), the Lesser Caucasus (Georgia), the Sanand, Alborz and Lut terranes (Iran), the Mangysglak (Caspian region), the Afghan terrane, the Karakorum (northern Pakistan), and the Lhasa and Qiangtang terranes (Tibet). Permian–Triassic widening of the Neo‑Tethys carried many of these blocks across the Equator toward eventual collision with Eurasia, producing the mosaic of accreted terranes observable in Eurasia today.

During the Neoproterozoic–Paleozoic phase of the Terra Australis Orogen the proto-Andean margin experienced repeated detachment, dispersal and subsequent reattachment of continental fragments. These terranes were rifted away in concert with the opening of the Iapetus Ocean and were later accreted back onto the Gondwanan edge during convergence, producing a complex, accretionary mosaic along the former continental margin.

A key Ordovician event involved the transfer of a Laurentian-derived crustal block into the developing southern South American domain; this block, variously termed Cuyania or the Precordillera, is implicated in the Famatinian orogeny of northwest Argentina and has been interpreted by some researchers as a southward continuation of Appalachian structural elements. After emplacement of Cuyania, the Chilenia terrane subsequently docked against it, recording a series of island-arc and microcontinental collisions that progressively constructed the western margin of Gondwana in what is now western South America.

Further south, the Patagonian composite terrane joined the Gondwanan margin in the late Paleozoic. Geochronological data from subduction-related magmatism beneath the North Patagonian Massif yield ages of about 320–330 Ma, indicating subduction initiation in the early Carboniferous. That subduction episode appears to have been relatively short-lived—on the order of 20 million years—such that lithospheric contact between Patagonia and Gondwana was achieved by the mid-Carboniferous and a more complete collisional assembly was attained by the early Permian.

Intervening accretionary events include the Devonian addition of the Chaitenia island-arc terrane to the Patagonian sector, an episode preserved in south-central Chile that contributed to the composite nature of Patagonian crust. Collectively, the sequence of Laurentian transfers (Cuyania/Precordillera), the accretion of Chilenia and Chaitenia, and the late Paleozoic Patagonian collision record a protracted, multi-stage construction of Gondwana’s western margin. This composite history not only shaped the present geology of the Southern Cone (northwest Argentina, south-central Chile and Patagonia) but also links these terranes to broader Paleozoic orogenic systems, including possible ties to Appalachian trends.

Gondwana as part of Pangaea: Late Paleozoic to Early Mesozoic

Gondwana remained sutured to Laurasia within the Pangaea supercontinent for roughly 150 million years. The broad assembly took place during the Carboniferous, culminating in final amalgamation in the Late Carboniferous–Early Permian; nevertheless, oblique convergence and transtensional stresses continued to shape the lithosphere until rifting began in the Triassic.

Although continental breakup was initiated in the Triassic, the major oceanic gateway between western and eastern Pangaea—the Central Atlantic—did not fully open until the Mid‑Jurassic. The fragmentation of western Pangaea was accompanied by extensive magmatism: the Central Atlantic Magmatic Province (CAMP) emplaced enormous flood basalts over several million years, peaked at ~200 Ma, and is temporally linked to the end‑Triassic biotic crisis.

Convergence between Gondwana and Laurasia closed intervening ocean basins (notably the Rheic and Paleo‑Tethys) and produced oblique orogenesis that accreted northern terranes to continental margins. A string of mountain belts—expressed in North America and Europe as the Marathon, Ouachita, Alleghanian and Variscan orogenies—record the terminal collision and together form a continuous Variscan–Appalachian orogenic system extending, in its broadest reconstruction, from present‑day Mexico across eastern North America and into southern Europe. Not all marginal blocks participated equally: some southern peri‑Laurentian fragments (e.g., Chortis, Oaxaca) remained largely passive, certain Peri‑Gondwanan blocks (for example Yucatán and Florida) were sheltered by promontories, while others (such as Carolina and Meguma) were directly involved in collision and accretion.

The construction of Laurasia proceeded in parallel. Collisions among Baltica, Siberia and Kazakhstania generated the Uralian orogeny, contributing to continental assembly at the northern end of Pangaea. At the eastern margin, a sequence of rifting and docking events—North China, South China and Indochina rifting from Gondwana to open the Proto‑Tethys, followed by Carboniferous–Permian docking of North China (and later South China), and Late Carboniferous rifting of the Cimmerian blocks to form the Paleo‑ and Neo‑Tethys—produced a protracted and diachronous pattern of basin opening and closure. The Cimmerian fragments ultimately accreted to Eurasia during the Triassic–Jurassic interval.

This diachronous coupling of assembly and breakup produced complex spatial and temporal mosaics of terrane transfer, basin evolution and sediment routing. The amalgamation of Pangaea and its mountain chains strongly affected global climate, sea level and ocean circulation, promoting glaciations, major shifts in depositional regimes and large‑scale continental erosion and sedimentation. These environmental perturbations are implicated in the Permian–Triassic biotic crisis and in the establishment of major natural‑resource provinces, including extensive coal, hydrocarbon, evaporite and metal deposits. In North America, for example, the base of the Absaroka stratigraphic sequence is contemporaneous with Alleghanian and Ouachita deformation and thus records continent‑scale changes in sediment provenance and dispersal far inland from active orogenic fronts.

Finally, the post‑breakup configuration of Gondwana‑derived fragments did not simply revert to a pre‑Pangaean arrangement. Rifting and seafloor spreading transferred and juxtaposed exotic crustal blocks in complex ways: parts of the modern southeastern United States (most of Florida and southern Georgia and Alabama) are underlain by crustal material derived from Gondwana yet remained attached to North America during Central Atlantic opening, illustrating the intricate terrane exchanges that accompanied Pangaea’s fragmentation.

Antarctica occupied the geographic and tectonic heart of Gondwana, forming continuous continental contacts with the adjacent landmasses and thereby acting as the nexus from which continental disaggregation radiated. The principal magmatic influence on this breakup was the Karoo–Ferrar large igneous province (LIP); plume-derived magmatism associated with this LIP (c. 200–170 Ma) produced extensive intrusion and eruption that weakened lithospheric strength and facilitated rift initiation along Antarctica’s margins.

Geophysical data record the earliest oceanic separation among Gondwanan blocks as the oldest marine magnetic anomaly patterns preserved between South America, Africa and Antarctica, concentrated in the present-day southern Weddell Sea. These anomalies indicate seafloor spreading and new ocean crust formation during the Jurassic (c. 180–160 Ma), a timing that overlaps with the Karoo–Ferrar emplacement. Synthesizing spatial and temporal evidence therefore implies that plume-related magmatism preconditioned Antarctic margins for rifting, that the first ocean basins formed in the southern Weddell Sea in the Early–Middle Jurassic, and that subsequent fragmentation propagated clockwise around Antarctica as continental fragments (for example, South America and Africa) separated and drifted apart.

The opening of the western Indian Ocean is rooted in Early Jurassic continental breakup that followed the rapid emplacement of the Karoo–Ferrar flood basalts (~184 Ma). Mantle upwelling associated with the Karoo plume is widely invoked as the trigger for rifting between Africa and Antarctica, but fragmentation of Gondwana had already begun along its southern, Proto‑Pacific margin. Detached fragments that now form the Antarctic Peninsula, Marie Byrd Land, Zealandia and Thurston Island separated from that margin before plume‑driven rifting intensified, and larger rigid blocks underwent dramatic reorganization: the Falkland Islands and the Ellsworth–Whitmore Mountains rotated by roughly 90° in opposite senses, while Patagonia (south of the Gastre Fault) translated westward during the early stages of break‑up.

The subsequent separation of Africa and Antarctica and ensuing seafloor spreading are recorded in fracture zones and magnetic anomaly patterns that flank the Southwest Indian Ridge; these features preserve the kinematic history of plate motions that opened the ocean basin. Along the eastern Gondwana margin, rifting within the India–Madagascar–Seychelles system produced discrete fragments—most notably Madagascar and an “Insular India” block separated from the Mascarene Plateau (which extends from the Seychelles toward Réunion). Portions of this rift chronology coincide with the end‑Cretaceous interval and appear temporally linked to major plume activity: the eruptions of the Deccan basalts and the inferred Réunion hotspot are broadly contemporaneous with India–Madagascar–Seychelles separations. In the modern oceanic layout the Seychelles and the Maldives are divided by the Central Indian Ridge, a product of these divergent motions.

Rifting and plume activity thus combined to reorganize continental fragments and generate new oceanic crust, while regional sea‑level rise accompanied the initial break‑up. In the Horn of Africa, an Early Jurassic marine transgression flooded pre‑existing Triassic planation surfaces and deposited a succession of clastic and carbonate sediments—sandstones, limestones, shales and marls—interspersed with evaporites, marking the transition from continental erosion surfaces to a nascent passive‑margin sedimentary regime.

Opening of the eastern Indian Ocean

During the Mesozoic reorganization of Gondwana, East Gondwana — comprising Antarctica, Madagascar, India and Australia — detached progressively from Africa, initiating prolonged geographic isolation that preconditioned subsequent internal fragmentation. The principal phase of internal breakup occurred between ca. 132.5 and 96 Ma and was driven by the north‑westward translation of the Indian block relative to the conjugate Australia–Antarctica margin. This lateral displacement established rift systems and nascent plate boundaries within the former contiguous Gondwanan domain.

The consequences of that breakup and later kinematic adjustments include the present non‑contiguity of the Indian and Australian plates. Between them lies the Capricorn plate and a zone of diffuse, distributed deformation characterised by microplate behaviour and complex, partly ill‑defined plate boundaries rather than a single coherent plate boundary. These structural reconfigurations reflect the progressive fragmentation of East Gondwana into discrete lithospheric fragments.

Large‑scale magmatism associated with the Kerguelen hotspot played a major role during the opening of the Indian Ocean. The hotspot generated time‑transgressive large igneous provinces: the Kerguelen Plateau formed on the Antarctic plate between ca. 118 and 95 Ma, and roughly contemporaneously (around 100 Ma) a linear volcanic track, the Ninety East Ridge, was emplaced on the Indian plate. Parts of this volcanic system are today separated by the Southeast Indian Ridge, the mid‑ocean spreading axis that now divides the Kerguelen Plateau from the Broken Ridge (the southern continuation of the Ninety East Ridge) and marks a principal segment of the southern Indian Ocean plate boundary.

Rifting between Australia and East Antarctica began about 132 Ma, with seafloor spreading established by ca. 96 Ma. In the Early Cenozoic a shallow seaway developed across the South Tasman Rise, and by the Eocene (≈35.5 Ma) continued generation of oceanic crust between the continents coincided with a global decline in ocean temperatures. These changes reflect linked tectonic, oceanographic and climatic reorganisation as the southern oceans took on their modern geometry.

A major tectono‑magmatic transition around 100 Ma — from arc‑style volcanism to extensional rift magmatism — facilitated the isolation of the submerged continent Zealandia from West Antarctica. By about 84 Ma the suite of fragments that constitute Zealandia (including present‑day New Zealand, Campbell Plateau, Chatham Rise, Lord Howe Rise, Norfolk Ridge and New Caledonia) had separated from the Antarctic margin, producing the dispersed continental fragments that characterise the southwest Pacific today.

The opening of the South Atlantic was a protracted, sectorial process rather than a single instantaneous rupture: rifting propagated diachronously from high southern latitudes toward the north, exploiting pre-existing Triassic–Early Jurassic structural lineaments. From the Jurassic into the Cretaceous, intracontinental extension segmented both Africa and South America into multiple sub-plates (commonly divided into three blocks on each continent), generating a suite of rift systems within continental sedimentary basins that preceded and accompanied the transition to oceanic spreading.

Rift initiation is recorded near Falkland latitudes at ~190 Ma, when Patagonia began a sustained westward displacement relative to the remainder of South America and Africa, a kinematic trend that lasted until the Early Cretaceous (ca. 126.7 Ma). Northward propagation of rifting followed—either in the Late Jurassic (~150 Ma) or Early Cretaceous (~140 Ma)—and appears to have produced dextral (right-lateral) strike-slip motions between neighboring sub-plates on opposite margins. South of bathymetric highs such as the Walvis Ridge and Rio Grande Rise, voluminous Paraná–Etendeka magmatism (ca. 130–135 Ma) coincided with renewed ocean-floor generation and development of conjugate rift segments on both margins.

Rift-related deformation and magmatism in southwestern Africa and eastern Brazil established long-lived intracontinental features, notably the Central African Rift System and the Central African Shear Zone, whose tectonic influence on basin architecture persisted until roughly 85 Ma. Constraints on seafloor spreading and kinematics at Brazilian latitudes remain limited by sparse palaeomagnetic data, although contemporaneous extension is well documented in parts of West Africa (for example the Benue Trough at ~118 Ma). Continental separation in equatorial and northern sectors occurred later and more slowly: rifting north of the equator began after ~120.4 Ma and continued through a protracted interval to about 100–96 Ma, producing an asynchronous opening along the margins. Paleobiogeographic evidence—such as identical dinosaur footprint assemblages in Brazil and Cameroon dated to ~120 Ma—supports the persistence of narrow land connections or short-distance dispersal pathways into the early Aptian. In sum, the South Atlantic breakup involved staged south-to-north rift propagation from ~190 Ma to at least ~85 Ma, multiple intracontinental rift systems, major magmatic pulses around 130–135 Ma, episodic right-lateral motions during northward advance, and geographically variable timing with later separation in the equatorial sector.

Early Andean orogeny

The Andean orogeny records a pronounced tectonic shift from an extensional, rift-dominated margin in the Jurassic–Early Cretaceous to a predominantly contractional orogenic regime by the mid–Late Cretaceous (~90 Ma), with sustained uplift and enhanced erosion thereafter. During its early phases, extension along the western South American margin produced rifting, back‑arc basin formation and voluminous batholithic magmatism—features consistent with subduction of relatively cold, old oceanic lithosphere beneath the continent.

Around ~90 Ma a fundamental change in the nature of the subducting plate—becoming younger and thermally warmer—coincided with a transition to intense compressional deformation of previously diverse shelf, slope and arc assemblages, and with the initiation or amplification of continental uplift and erosional stripping in the Late Cretaceous. This mid‑Cretaceous transformation occurred in the context of large‑scale plate reorganisation associated with the opening of the South Atlantic, implying that shifts in relative plate motions at oceanic scales modulated Andean margin dynamics.

Kinematically, the direction of trench‑parallel motion of the downgoing lithosphere changed markedly at this time: a dominant south‑eastward component gave way to a north‑eastward trajectory, representing a major reorientation of convergence vectors at the margin. Subduction nevertheless remained oblique to the continental margin, so that strain was partitioned between trench‑normal shortening and trench‑parallel shear, with persistent influence on the style and localization of deformation.

The plate‑scale kinematic reconfiguration was transmitted into the crustal fault network and drove reactivation and modification of several major subduction‑zone‑parallel fault systems. Notably, the Atacama, Domeyko and Liquiñe‑Ofqui fault systems record this mid‑Cretaceous change through renewed displacement, reoriented slip vectors and structural adjustments that link plate motion changes directly to Andean fault behaviour.

Cenozoic tectonics profoundly reconfigured former Gondwanan margins and global circulation. The northward drift and ultimate collision of the Indian plate with Eurasia at about 70 Ma initiated the construction of the Indian subcontinent and drove extreme crustal shortening and thickening; more than 1,400 km of crustal material has been incorporated into the Himalayan–Tibetan orogen, fundamentally altering regional tectonic regimes and crustal architecture. Continued convergence during the Cenozoic produced the high, internally deformed Tibetan Plateau—a broad domain of thickened crust and sustained uplift that expanded laterally between the Tethyan Himalaya to the south and the Kunlun–Qilian ranges to the north.

Contemporary reconfiguration of ocean gateways and ongoing rifting also mark the Cenozoic. The emergence of the Isthmus of Panama linked North and South America and severed equatorial oceanic throughflow, modifying meridional heat transport, contributing to cooling at high latitudes (including the Arctic) and enabling the Great American Biotic Interchange. Meanwhile, the fragmentation of Gondwana persists in eastern Africa at the Afar triple junction, where the Arabian, African and Somali plates diverge. This plate separation drives active rifting expressed in the Red Sea and the East African Rift system and records a continuing transition from continental rifting toward nascent oceanic spreading.

Australia–Antarctica separation

In the Early Cenozoic Australia remained joined to Antarctica and lay some 35–40° of latitude farther south than today; this connection formed one limb of a trans-Antarctic land bridge that also linked Antarctica with South America. A rift between Australia and Antarctica developed but functioned as a broad embayment until the Eocene–Oligocene transition, when the onset of continuous circum‑Antarctic ocean circulation coincided with the initiation of Antarctic glaciation.

Paleocene Australia experienced warm, wet conditions dominated by extensive rainforests, indicative of high precipitation and low seasonality immediately after the Cenozoic dawn. Between roughly 40 and 30 Ma the Tasman Gateway began to open, and by the Eocene–Oligocene boundary (~33 Ma) its deepening produced abrupt regional cooling; paradoxically, the early Oligocene in Australia saw elevated rainfall and widespread swamp development in the southeast. The Miocene returned the continent to generally warm, humid conditions with scattered rainforest remnants, but a late‑Miocene shift toward colder, drier climates caused dramatic rainforest contraction. The Pliocene brought a short phase of increased precipitation followed by a persistent drying trend and grassland expansion; thereafter, alternating wet interglacial and dry glacial cycles superimposed a long‑term decline in precipitation (on the order of 15 Myr) that produced the present arid to semi‑arid regime.

The Antarctic Circumpolar Current (ACC) emerged as a coherent, circumpolar circulation in the Late Oligocene (~23 Ma) with the full opening of the Drake Passage and further deepening of the Tasman Gateway. However, the oldest oceanic crust in the Drake Passage dates to 34–29 Ma, indicating that seafloor spreading between Antarctica and South America began near the Eocene–Oligocene boundary. Deep‑sea sediments and paleoenvironmental records from Tierra del Fuego and the North Scotia Ridge document an earlier, weaker Proto‑ACC during the Eocene–Oligocene; between ca. 26 and 14 Ma geological events (shallowing along the North Scotia Ridge, closure of the Fuegan Seaway, uplift of the Patagonian Cordillera), together with volcanic forcing from a reactivated Iceland plume, strongly restricted this Proto‑ACC and contributed to a transient global warming. Subsequent Miocene widening of the Drake Passage renewed and intensified ACC flow, thermally isolating Antarctica and acting as a principal driver of global cooling through altered oceanic heat transport.

Concomitant plate tectonic motion further shaped Australia’s palaeogeography: northward translation of the Australian Plate produced arc–continent collisions and interactions with the Philippine and Caroline plates and promoted uplift of the New Guinea Highlands. These tectonic rearrangements, coupled with the progressive climatic transitions from Oligocene rainforest dominance through Miocene fragmentation to Pliocene–Quaternary aridification, define the principal palaeogeographic and palaeoclimatic evolution of Australia following its separation from Antarctica.

Biogeography

In biogeographical practice, “Gondwanan” describes taxa whose present ranges are restricted to two or more geographically separated regions that were once contiguous within the supercontinent Gondwana; this concept explicitly incorporates elements of the Antarctic flora. Such patterns are typified by plant families like Proteaceae, which historically occupied the southern landmasses and today have representatives on the major Southern Hemisphere continents, reflecting deep evolutionary roots and often being regarded as archaic or relict lineages on the basis of their phylogenetic histories.

Banksia, a genus within the grevilleoid clade of Proteaceae, serves as a representative example of a Gondwanan distribution: its affinities and geographic occurrence illustrate how a lineage can retain a southern-hemisphere signature. The contemporary, disjunct distribution of Proteaceae is best understood as the product of two sequential sets of processes. First, vicariance associated with continental fragmentation and plate motions redistributed ancestral lineages as landmasses separated. Second, following separation, episodic long‑distance oceanic dispersal moved some lineages across marine barriers, producing the finer‑scale, post‑breakup occurrences now observed.

Consequently, meaningful interpretation of Gondwanan distributions requires an integrated approach that combines palaeogeographic reconstruction of former land connections (including the role of the Antarctic floristic component) with evidence for later transoceanic dispersal, since both mechanisms have shaped the present-day patterns.

Post‑Cambrian diversification

During the Silurian Gondwana extended from near the Equator (present‑day Australia) to polar latitudes (North Africa and South America), while Laurasia lay at equatorial latitudes opposite Australia. A short Late Ordovician glaciation gave way to a warmer Silurian interval; the End‑Ordovician extinction that accompanied this climatic transition removed roughly 27% of marine families and 57% of genera. Terrestrial colonization had already begun: by the close of the Ordovician the small, ground‑covering vascular plant Cooksonia represents the earliest known vascular land plant, but this pioneering vegetation was largely confined to equatorial landmasses (Laurasia and equatorial Australia within Gondwana).

In the late Silurian tropical zones two divergent lineages of early vascular plants became established. Zosterophylls, which ultimately led to lycopods, and rhyniophytes, ancestral to horsetails and later seed plants, initiated distinct tropical radiations. Much of Gondwana remained distant from the tropics and therefore comparatively depauperate in terrestrial life.

During the Devonian, northward drift of West Gondwana brought the supercontinent closer to Laurasia even as global cooling culminated in the Late Devonian extinction (about 19% of marine families and 50% of genera lost) and episodic glaciation in South America. Nevertheless pteridophytes underwent rapid diversification and dispersed into Gondwana, producing novel regional floras. The Baragwanathia Flora of Victoria, preserved only in the Yea Beds in two stratigraphic levels separated by approximately 1,700 m (c. 30 Myr), documents this transition: the younger assemblage is richer and contains Baragwanathia, a primitive herbaceous lycopod derived from zosterophylls. Later Devonian successions show the rise of tree‑forming plants—giant club mosses inaugurated an arborescent habit and progymnosperms such as Archaeopteris mark the emergence of large woody trees.

Vertebrate evolution across the Devonian–Carboniferous boundary likewise records a major transformation: osteolepiform fishes in Laurasia gave rise to amphibian tetrapods in regions such as Greenland and Russia. Gondwana’s fossil record of this transition is sparse, limited mainly to amphibian footprints and a solitary jaw from Australia.

Carboniferous tectonics and oceanographic rearrangement—notably the closure of the Rheic Ocean and the assembly of Pangaea—altered currents and ushered in an Ice‑House climate. As Gondwana rotated clockwise, Australia moved into more temperate latitudes and an ice cap that originated over southern Africa and South America expanded to cover most of the supercontinent, leaving only the northernmost reaches of Africa–South America ice‑free. Biotic contrasts between hemispheres were pronounced: equatorial Laurasia supported extensive lycopod‑ and horsetail‑dominated forests and a diverse assemblage of true insects, whereas glaciation and, in parts of Gondwana, volcanism reduced Devonian floras to low‑diversity seed‑fern communities. Over the Carboniferous and beyond pteridophytes were progressively supplanted by gymnosperms in Gondwana, a dominance that persisted until the Mid‑Cretaceous. Early in the Carboniferous, when Australia still lay near the Equator, temnospondyl and lepospondyl amphibians and early amniote reptiles — faunas closely related to Laurasian groups — evolved there, but advancing glaciation ultimately extirpated these vertebrate assemblages from much of Gondwana.

Permian–Triassic global warming melted the Gondwanan ice sheet and lowered sea levels, enabling glossopterid seed‑ferns to colonize and reach peak diversity in the Late Permian, when extensive coal‑forming forests blanketed the supercontinent. Within this interval the order Voltziales arose and was among the few plant groups to survive the Permian–Triassic mass extinction (which removed approximately 57% of marine families and 83% of genera); Voltziales subsequently gave rise to true conifers that came to dominate later Mesozoic and Cenozoic floras. Early Permian wetlands in Gondwana remained dominated by tall lycopods and horsetails, while insects radiated in close association with glossopterids, exceeding 200 species in 21 orders by the Late Permian with substantial records from South Africa and Australia (beetles and cockroaches were comparatively minor components). Tetrapod remains appear first in Laurasia in the Early Permian but become widespread in Gondwana later in the Permian, and the proliferation of therapsids helped establish the first broadly integrated plant–vertebrate–insect terrestrial ecosystems across the supercontinent.

Modern diversification

During the Triassic a rapid biotic recovery from the end‑Permian crisis occurred under generally hot‑house climates. Early Triassic woodlands were dominated by conifer lineages such as Podocarpaceae and Araucariaceae and by the extinct seed‑fern Dicroidium, but conifers themselves underwent an especially rapid radiation: by the close of the Triassic six of the eight extant conifer families had appeared and two now‑extinct gymnosperm orders (Bennettitales, Pentoxylales) originated and later became important in Mesozoic floras. Among pteridophytes there was a marked divergence of trajectories—lycophytes and sphenophytes steadily dwindled while ferns, although never numerically dominant, diversified. Overall gymnosperm biodiversity in the Triassic may have rivalled or exceeded later angiosperm diversity; if flowering plants began in the Triassic, the evidence points more strongly to Laurasian than Gondwanan origins.

The Triassic–Jurassic crisis brought a brief return to cooler conditions that disproportionately affected vertebrate lineages (notably many dinosaurs) while leaving most plant groups comparatively intact. The Jurassic that followed remained largely warm and favoured further vertebrate diversification; plant innovation is less conspicuous, however, with Jurassic Gondwanan vegetation still dominated by conifers and other gymnosperms inherited from the Triassic. Cheiroleidiacean conifers, Caytoniales and several seed‑fern lineages persist in the Jurassic record, whereas most Paleozoic‑dominant pteridophytes retreated to minor roles dominated by certain fern lineages. Fossil insects are relatively scarce in Gondwana’s Jurassic deposits—likely a product of extensive aridity and volcanism—so insect–plant coevolutionary signals are weaker than in some northern regions; dinosaur evolutionary patterns during this interval nonetheless reflect the progressive fragmentation of Pangaea.

The Cretaceous marks a fundamental floral transition with the arrival and staged radiation of angiosperms, most plausibly originating in western Gondwana (the South America–Africa region). Monocots and magnoliids appear in the Early Cretaceous, followed by major diversification among dicot lineages. By the mid‑Cretaceous angiosperms comprised roughly half the flora in parts of northeastern Australia. This explosive rise of flowering plants shows no clear temporal tie to a single mass extinction or to an abrupt shift in insect or vertebrate evolution: many putative pollinator insect orders (beetles, flies, Lepidoptera, and hymenopterans) had been diversifying continuously since the Permian–Triassic interval. Exceptionally preserved insect assemblages from Cretaceous Gondwanan deposits (e.g., Santana, Koonwarra, Orapa) document this long‑standing insect diversity.

Later Cretaceous floral turnover in Gondwana (~115 Ma) is characterised by the disappearance of several formerly important groups—conifers, bennettitaleans and pentoxylaleans—concurrent with the loss of specialized herbivorous ornithischians, whereas generalist sauropodomorph browsers persisted. The Cretaceous–Paleogene extinction eliminated non‑avian dinosaurs but had a comparatively muted effect on Gondwanan plant lineages, many of which crossed the boundary intact.