Conjugate Continental Margins Research Articles

Definition of tectono-sedimentary elements for rifted continental margins of the Norwegian and Greenland seas

Abstract The geology of the conjugate continental margins of the Norwegian and Greenland Seas reflects 400 Ma of post-Caledonian continental rifting, continental breakup between early Eocene and Miocene times, and subsequent passive margin conditions accompanying seafloor spreading. During Devonian-Carboniferous time, rifting and continental deposition prevailed, but from the mid-Carboniferous, rifting decreased and marine deposition commenced in the north culminating in a Late Permian open seaway as rifting resumed. The seaway became partly filled by Triassic and Lower Jurassic sediments causing mixed marine/non-marine deposition. A permanent, open seaway established by the end of the Early Jurassic and was followed by the development of an axial line of deep marine Cretaceous basins. The final, strong rift pulse of continental breakup occurred along a line oblique to the axis of these basins. The Jan Mayen Micro-Continent formed by resumed rifting in a part of the East Greenland margin in Eocene to Miocene times. This complex tectonic development is reflected in the sedimentary record in the two conjugate margins, which clearly shows their common pre-breakup geological development. The strong correlation between the two present margins is the basis for defining seven tectono-sedimentary elements (TSE) and establishing eight composite tectono-sedimentary elements (CTSE) in the region.

Contemporaneous intraplate magmatism on conjugate South Atlantic margins: A hotspot conundrum

Intraplate magmatism is enigmatic in origin despite its importance in our understanding of crustal cycling through the deep mantle. A mantle plume origin is justified for some intraplate magmatism, but not in the case of a large number of occurrences. Here we present a novel explanation for intraplate magmatism in situations where evidence for a plume origin is either lacking or equivocal. Specifically, we highlight two voluminous, long-lived intraplate magmatic provinces located on the precisely conjugate continental margins of Cameroon and NE Brazil and which lasted, respectively, from 65 and 52 Ma to the present. New Ar dating and geochemical data show that magmatism in the two provinces was contemporaneous, identical in incompatible-element composition, and started >40 Myr after continental separation, when the two margins were ∼2000 km apart. Lack of age progression in magmatic activity rules out a mantle plume origin. We propose an origin in sub-continental lithospheric mantle that was thickened during Gondwana supercontinent assembly. Thermal re-equilibration of the thickened lithosphere accompanied by percolation of carbonate-rich melt led to the formation of a thick zone of newly created, enriched asthenosphere that is held in place by buoyancy, prevented from dispersing by adjacent lithospheric blocks, and heated by radioactive decay. Following continental breakup at 105 Ma, slow outward drainage of this enriched and heated asthenosphere was channelled into thinner parts of the continental and oceanic lithosphere. Sublithospheric drainage and decompression melting of this enriched mantle provides a viable explanation for these and many other intraplate magmatic occurrences.

Plate tectonic reconstructions and paleogeographic maps of the central and North Atlantic oceans1This article is one of a series of papers published in this CJES Special Issue on the theme ofMesozoic–Cenozoic geology of the Scotian Basin.2Earth Sciences Sector Contribution 20120172.

We have established a new plate kinematic model of the central and North Atlantic oceans between North America, Africa, Meseta, Iberia, Flemish Cap, and Galicia Bank from Late Triassic to Late Cretaceous to better understand the nature and timing of rifting of Nova Scotia and Morocco conjugate continental margins since Late Triassic. The maps of salt distributions at the Sinemurian–Pliensbachian limit (190 Ma; after salt deposition) and in middle Bajocian (170 Ma) show that an area of the Nova Scotia margin is devoid of allochthonous salt and that an area of similar size located oceanward of the West African Coast Magnetic Anomaly shows salt deposits, suggesting that a portion of the Nova Scotia margin with its overlying salt deposits could have been transferred onto the Moroccan side right after the formation of the conjugate East Coast Magnetic Anomaly and West African Coast Magnetic Anomaly. Seven paleogeographic maps, from Late Triassic to Late Cretaceous, are presented with structural elements and magnetic lineations. They show that the connection between the Central Atlantic and the Tethys, with an aborted rift between Iberia and North America ending in the north against the Flemish Cap – Galicia Bank dam, started to deepen at the end of the first rifting phase (190 Ma ago) after the rupture of the thinned continental crust. It is only during the Early Cretaceous, after the rupture of the Flemish Cap – Galicia Bank dam, that the deep connection around Iberia was finally established between the Central and North Atlantic, the Tethys, and the Bay of Biscay.

Scientific Drilling

No abstract available. doi:10.2204/iodp.sd.14.07.2012

Comparison of lithosphere structure across the Orphan Basin–Flemish Cap and Irish Atlantic conjugate continental margins from constrained 3D gravity inversions

Regionally constrained 3D gravity inversion results on the Orphan Basin–Flemish Cap and the Irish Atlantic conjugate continental margins are compared to investigate crustal structure, early rifting history and geological evolution of this part of the North Atlantic. The full-crustal density anomaly distributions provide some of the first depth images of how rifted structures compare along and across these conjugate margins. Broad similarities in crustal structure are identified with some noticeable differences, linked to rifting and crustal stretching processes. Extreme crustal thinning (stretching factors >3.5) is indicated beneath much of the southern Porcupine Basin, the western half of West Orphan Basin, the eastern half of Jeanne d’Arc Basin, the southeastern half of East Orphan Basin and in pockets beneath Rockall Basin. This appears to have resulted in the serpentinization (and possible exhumation) of mantle lithosphere on the Irish Atlantic and Flemish Cap margins but not beneath Orphan Basin. A simple evolution model is proposed for the early stages of rifting between the margins. It is suggested that ancient orogenic sutures played an important role in controlling the northward migration of rifting and the rotation and displacement of Flemish Cap out of Orphan Basin. Supplementary material: Enlarged maps from this paper are available at www.geolsoc.org.uk/SUP18527 .

Magnetic recording of the Cenozoic oceanic crustal accretion and evolution of the South China Sea basin

We review and discuss some of the recent scientific findings made on magnetic data in the South China Sea (SCS). Magnetic anomalies bear extremely rich information on Mesozoic and Cenozoic tectonic evolution. 3D analytical signal amplitudes computed from magnetic anomalies reveal very precisely relict distributions of Mesozoic sedimentary sequences on the two conjugate continental margins, and they are also found very effective in depicting later-stage magmatism and tectonic transitions and zonation within the SCS oceanic crust. Through integrated analyses of magnetic, gravity and reflection seismic data, we define the continent-ocean boundary (COB) around the South China Sea continental margin, and find that the COB coincides very well with a transition zone from mostly positive to negative free-air gravity anomalies. This accurate outlining of the COB is critical for better tracing magnetic anomalies induced by the oceanic crust. The geometrically complex COB and inner magnetic zonation require the introduction of an episodic opening model, as well as a transform fault (here coined as Zhongnan Fault) between the East and Southwest Sub-basins, while within the East and Southwest Sub-basins, magnetic anomalies are rather continuous laterally, indicating nonexistence of large transform faults within these sub-basins. We enhance magnetic anomalies caused by the shallow basaltic layer via a band-pass filter, and recognize that the likely oldest magnetic anomaly near the northern continental margin is C12 according to the magnetic time scale CK95. Near the southern continental margin, magnetic anomalies are less recognizable and the anomaly C12 appears to be missing. These differences show an asymmetrical opening style with respect to the relict spreading center, and the northern part appears to have slightly faster spreading rates than to the south. The magnetic anomalies C8 (M1 and M2, ∼26 Ma) represent important magnetic boundaries within the oceanic basin, and are possibly related to changes in spreading rates and magmatic intensities. The magnetic evidence for a previously proposed ridge jump after the anomaly C7 is not clear. The age of the Southwest Sub-basin has yet to be further examined, most favorably with deep-tow magnetic surveys and ocean drilling. Our magnetic spectral study shows that the shallowest Curie points are located around the eastern part of the Southwestern Sub-basin, whereas within the East Sub-basin Curie depths are smaller to the north of the relict spreading center than to the south. This pattern of Curie depths is consistent to regional heat flow measurements and later-stage volcanic seamount distributions, and we therefore reason that Curie-depth variations are closely associated with later-stage magmatism, rather than with crustal ages. Although magnetic anomalies located around the northern continent-ocean transition zone (COT) are relatively quiet, this area is not a typical magnetic quiet zone since conceptually it differs markedly from an oceanic magnetic quiet zone. The relatively quiet magnetic anomalies are seemingly associated with a shallowing in Curie isotherm and thinning in magnetic layer, but our comprehensive observations suggest that the well-preserved thick Mesozoic sedimentary rocks are major causes for the magnetically quiet zone. The high similarities between various low-pass filtered marine and air-borne magnetic anomalies and satellite magnetic anomalies clearly confirm that deeper magnetic sources (in the lower crust and the uppermost mantle) have contributions to long-wavelength surface magnetic anomalies in the area, as already inferred from magnetically inversed Curie depths. The offshore south China magnetic anomaly (SCMA) becomes more prominent on low-pass filtered marine and air-borne magnetic anomalies and satellite magnetic anomalies, indicating very deeply-buried magnetic sources beneath it.

The Jurassic history of the Africa–Antarctica corridor — new constraints from magnetic data on the conjugate continental margins

Finding the best fit for East- and West-Gondwana requires a detailed knowledge of the initial Jurassic movements between Africa and Antarctica. This study presents results of systematic and densely spaced aeromagnetic measurements, which have been conducted in 2009/2010 across the Astrid Ridge (Antarctica) and in the western Riiser-Larsen Sea to provide constraints for the early seafloor spreading history between both continents. The data reveal different magnetic signatures of the northern and southern parts of the Astrid Ridge, which are separated by the Astrid Fracture Zone. The southern part is weakly magnetised, corresponding to the low amplitude anomaly field of the southwestern Riiser-Larsen Sea. In contrast, the northern Astrid Ridge bears strong anomalies of positive value. Furthermore, several sets of trends are visible in the data.In the Mozambique Channel, we extended the existing magnetic spreading anomaly identifications. Combined with the spreading anomalies in the conjugate Riiser-Larsen Sea, they were used to establish a new model of the relative movements of Africa and Antarctica after the breakup of Gondwana in Jurassic times. A detailed model for the emplacement of the Mozambique Ridge is now incorporated.The model postulates a tight fit between Africa and Antarctica and two stages of breakup, the first of which lasting until ~159Ma (M33n). During this stage, Antarctica rotated anticlockwise with respect to Africa. The Grunehogna Craton cleared the Coastal Plains of Mozambique to a position east of the Mozambique Fracture Zone. The southern Astrid Ridge is interpreted to consist of oceanic crust, also formed during this first stage, prior to the Riiser-Larsen Sea. During the second stage, Antarctica moved southward with respect to Africa forming the Mozambique Basin and the conjugate Riiser-Larsen Sea. The Mozambique Ridge and the Northern Natal Valley were formed at different spreading centres being active subsequently.

Integrated Geophysical Research on the Tectonic Attribute of Conjugate Continental Margins of South China Sea

AbstractIn this paper the density and magnetic structures along 6 typical profiles in the South China Sea were determined by inversion of the latest gravity and magnetic data based on the results of rock property analysis and whole‐sea magnetic basement distribution, then the deep structures were further compared and analyzed. The inversion was constrained as much as possible by the sea bottom seismometer (OBS) and multi‐channel seismic (MCS) data, such as for profile FF0 the newest MCS data collected in 2009 by the 973 Project “Continental Margin Dynamics and Oil/Gas Resource Potential of South China Sea” were used in interval velocity analysis, and the OBS2009 data of Nansha section were combined with gravity data in structure modeling. Based on the deep structures and the density/magnetic characteristics of the 6 profiles, it is inferred that the tectonic attributes of both the northern and southern margins of South China Sea are basically of non‐volcanic type. To the east of profile CC0 in the north margin there is a high‐density layer in the lower crust accompanied with active magma activity, however, the evidence of typical seaward dipping reflectors is lacking; therefore it is inferred that the high‐density layer, as well as the shallow magmatic rocks, are the products of continental margin rifting after seafloor spreading. The magnetic basement and the deep structures of Zhongsha Uplift and Liyue Basin are very similar; they are deduced to belong to the same block before the pull‐apart of the sea basin, being a pair of conjugate points of the northern and southern margins of the South China Sea. The integrated geophysical interpretation of the south margin of SW Sub‐basin indicated that the Mesozoic group exists near the foot of continental slope, but it may not be continuous on the entire profile.

OBS Survey and Crustal Structure of the SW Sub‐Basin and Nansha Block, South China Sea

AbstractOBS973‐1 is a wide angle reflection and refraction deep seismic line using Ocean Bottom Seismometers (OBS), collected for the first time in the southern part of South China Sea. The line crosses the southern margin of the Southwest Sub‐basin and the middle part of Nansha Block. By seismic phase analysing and travel time fitting, a 2D P‐wave velocity model along the line is constructed. The modeling results show that the surface sedimentary layer has a velocity of 2.5~4.5 km/s and a thickness of 1000~3000 m, with locally rough basement interface. The crystalline basement has a velocity of 4.5~5.5 km/s on the top, increasing to 6.8~6.9 km/s near the bottom of the crust. In the middle crust there is a small velocity discontinuity (0.1~0.2 km/s), while the Moho on the bottom crust has a large velocity contrast (1.2 km/s). In the top mantle the velocity is 8.0~8.1 km/s. The Moho depth and the crustal thickness have much difference between the northern and southern segments along the line. The northern segment is in the deep sea basin, where the Moho is 11 km deep and the crystalline crust is only 5~6 km thick, which are typical characteristics of oceanic crust. In contrast, the southern segment is on the continental block, where the Moho has a maximum depth of 24 km and the crust has a corresponding thickness of 20 km, which are representative characteristics of thinned continental crust. From the deep sea basin to the continental block, the Moho depth and the crustal thickness increase rapidly. In the continental area, the upper crust and lower crust have similar thickness and variation. No High Velocity Layer (HVL) is seen in the lower crust. These may imply that pure‐shear extension and uniform thinning are dominating inside the crust, and magma underplating is not developed in the lower crust. Comparing with the structure models of OBS973‐2 and OBS973‐3, it is inferred that the middle and eastern parts of Nansha Block have similar tectonic characters, and the two sides of Southwest Sub‐basin are a pair of non‐volcanic asymmetric conjugate continental margins.

Volcanism, jump and propagation on the Sheba ridge, eastern Gulf of Aden: segmentation evolution and implications for oceanic accretion processes

The rifting between Arabia and Somalia, which started around 35 Ma, was followed by oceanic accretion from at least 17.6 Ma leading to the formation of the present-day Gulf of Aden. Bathymetric, gravity and magnetic data from the Encens-Sheba cruise are used to constrain the structure and segmentation of the oceanic basin separating the conjugate continental margins in the eastern part of the Gulf of Aden between 51 degrees E and 55.5 degrees E. Data analysis reveals that the oceanic domain along this ridge section is divided into two distinct areas. The Eastern area is characterized by a shorter wavelength variation of the axial segmentation and an extremely thin oceanic crust. In the western segment, a thicker oceanic crust suggests a high melt supply. This supply is probably due to an off-axis melting anomaly located below the southern flank of the Sheba ridge, 75 km east of the major Alula-Fartak transform fault. This suggests that the axial morphology is produced by a combination of factors, including spreading rate, melt supply and the edge effect of the Alula-Fartak transform fault, as well as the proximity of the continental margin. The oceanic domains have undergone two distinct phases of accretion since the onset of seafloor spreading, with a shift around 11 Ma. At that time, the ridge jumped southwards, in response to the melting anomaly. Propagating ridges were triggered by the melting activity, and propagated both eastward and westward. The influence of the melting anomaly on the ridges decreased, stopping their propagation since less than 9 Ma. From that time up to the present, the N025 degrees E-trending Socotra transform fault developed in association with the formation of the N115 degrees E-trending segment #2. In recent times, a counter-clockwise rotation of the stress field associated with kinematic changes could explain the structural morphology of the Alula-Fartak and Socotra-Hadbeen fracture zones.

Structure and evolution of the continental margin off Norway and the Barents Sea

The Norwegian Margin formed in response to early Cenozoic continental breakup and subsequent opening of the Norwegian-Greenland Sea. There is a welldefined margin segmentation and the various segments are characterized by distinct crustal properties, structural and magmatic styles, and post-opening history of vertical motions. The sedimentary basins at the conjugate continental margins off Norway and Greenland and in the western Barents Sea developed as a result of a series of post-Caledonian rift episodes until early Cenozoic time, when complete continental separation took place.

Structure and evolution of an obliquely sheared continental margin: Rio Muni, West Africa

Oblique-shear margins are divergent continental terrains whose breakup and early drift evolution are characterized by significant obliquity in the plate divergence vector relative to the strike of the margin. We focus on the Rio Muni margin, equatorial West Africa, where the ca. 70-km-wide Ascension Fracture Zone (AFZ) exhibits oblique–slip faulting and synrift half-graben formation that accommodated oblique extension during the period leading up to and immediately following whole lithosphere failure and continental breakup (ca. 117 Ma). Oblique extension is recorded also by strike–slip and oblique–slip fault geometry within the AFZ, and buckling of Aptian synrift rocks in response to block rotation and local transpression. Rio Muni shares basic characteristics of both rifted and transform margins, the end members of a spectrum of continental margin kinematics. At transform margins, continental breakup and the onset of oceanic spreading (drifting) are separate episodes recorded by discrete breakup and drift unconformities. Oceanic opening will proceed immediately following breakup on a rifted margin, whereas transform and oblique-shear margins may experience several tens of millennia between breakup and drift. Noncoeval breakup and drift have important consequences for the fit of the equatorial South American and African margins because, in reconstructing the configuration of conjugate continental margins at the time of their breakup, it cannot be assumed that highly segmented margins like the South Atlantic will match each other at their ocean–continent boundaries (OCBs). Well known ‘misfits’ in reconstructions of South Atlantic continental margins may be accounted for by differential timing of breakup and drifting between oblique-shear margins and their adjacent rifted segments.

Models for continental breakup and deep-water basin formation: insights from integration of potential field modelling and deep seismic data on conjugate continental passive margins

Recently acquired deep seismic reflection and refraction datasets, with coincident shipborne gravity and towed magnetometer data from the Great Australian Bight and its Antarctic conjugate margin basins, provide significant new constraints on conceptual models for continental breakup and subsequent deep-water basin formation.

Continental margin off Western India and Deccan Large Igneous Province

Massive, transient late syn-rift-to-breakup volcanism during separation between the Seychelles microcontinent and India formed the Deccan continental flood basalts and their equivalents on the Seychelles-Mascarene Plateau and on the conjugate continental margins, i.e. the Deccan Large Igneous Province. We estimate an original extrusive area of at least 1.8×106 km2, and a volume >1.8×106 km3, and suggest a plate tectonic model comprising: (1) development of the Seychelles microplate by fan-shaped spreading in the Mascarene Basin, and continental extension followed by fan-shaped spreading between India and the Seychelles during A29-27 time. (2) Cessation of fan-shaped spreading just after A27 time, followed by spreading along the India-Seychelles plate boundary. (3) Margin subsidence, modified south of Goa by the persistent, time-transgressive effects along the plume trail. The margin is divided into three regional provinces by the prolongation of regional transforms which formed the east and west boundaries of the Seychelles microplate during breakup and early sea floor spreading. In some aspects, the conjugate margins are different from other volcanic margins; e.g. regional wedges of seaward dipping reflectors along the continent-ocean transition have not yet been reported. We ascribe this to the eruption of the most voluminous lavas during chron 29r, i.e on continental lithosphere in a late syn-rift setting. The enigmatic Laxmi Ridge is a complex marginal high comprised of both continental and oceanic crust. It was probably created during breakup, but may have experienced later magmatic and/or tectonic deformation.

Constraints on the tectonic development of the eastern Gulf of Mexico provided by magnetic anomaly data

Boundaries between oceanic and transitional crust in the eastern Gulf of Mexico have been delineated using detailed, accurately navigated, high‐quality aeromagnetic data. These data indicate that considerably more oceanic crust may be present than previously suggested by other geophysical data, especially seismic reflection data. The N‐S extent of oceanic crust substantially increases westward from approximately 280 km near 87°W to roughly 390 km near 90°W, indicating the proximity (<10°) of the pole of rotation. Variations in the amount of oceanic crust together with discontinuities in the magnetic anomaly patterns, interpreted as the traces of fossil transform faults or fracture zones, have been used to obtain a rough estimate of the location of the pole of rotation (24°N, 81.5°W) for the seafloor spreading phase of opening. The magnetic data have been used to develop a model for the opening of the Gulf and to identify some geometrical relationships between its conjugate continental margins. Based upon the estimated pole position, the eastern Gulf is interpreted to have opened in an approximately NNE‐SSW direction with the counterclockwise rotation of Yucatan away from North America. The seafloor spreading phase of movement accounts for about 25° of the counterclockwise motion of Yucatan. Rotating the Yucatan block clockwise by this amount to restore it to its predrift position places the Campeche Bank adjacent to the Mississippi Trough‐Louisiana shelf. Further clockwise rotation of Yucatan by an additional 30–35° about this pole restores extended crust to its original thickness and is consistent with rotations of Yucatan predicted from paleomagnetic data from Chiapas.

Stretching and subsidence: Rifting of conjugate margins in the North Atlantic Region

Subsidence on rifted conjugate continental margins around the North Atlantic is analyzed to derive the amount and areal distribution of stretching in the crust and in the lower lithosphere during continental rifting. Study areas are the Grand Banks and Orphan Basin regions of the eastern Canadian continental margin and the Goban Spur and Galicia Bank regions off western Europe. In all areas, maps of synrift and postrift sediment thickness and bathymetry were used to derive maps of post‐ and synrift subsidence. A two‐layer lithospheric stretching model with independent amounts of stretching in the crust and in the lower lithosphere was assumed to be applicable, with the rifting history approximated by several instantaneous episodes of extension. This model was used to derive estimates of stretching at all points on a 0.05° geographical grid, where subsidence values were available within the study regions. The models are constrained with seismic measurements of crustal thickness. The results imply that pure shear stretching predominates at a lithospheric scale, while simple shear is more localized laterally and confined to the crust. In places there is significant decoupling between crustal and mantle stretching. Near the continent‐ocean boundary, final continental breakup may be localized on one side of the rift between conjugate margin pairs, rather than symmetrically located. Total extension of the margins is compatible with that estimated from normal fault geometries and indicates that the continent‐ocean boundary has been extended up to 350 km seaward of its original position, which should be considered in plate kinematic reconstructions.

A Pull-Apart Model for the Red Sea Without a Pole of Rotation in the Separation of Arabia and Africa

Wide-angle seismic surveys in the Red Sea and adjacent areas revealed fundamental asymmetries of the conjugate continental margins: the Western flank shows large areas of old oceanic crust, whereas the whole eastern flank is underlain by stretched continental crust. In addition, the African margin appears very abrupt over long sectors of the northern and central Red Sea. Gravity, magnetic, and heat flow density observations reveal the controlling structural trends, spreading history, and locations of recent magmatic intrusions, They confirm the seismic results and provide information on the entire basin. These geophysical results have implications for Red Sea evolution models: strike-slip processes controlled the breakup of the Arabian plate from Africa. The geometry of the early strike-slip zones reflects the configuration of major preexisting fault systems such as the Najd fault system, the Onib-Harnisana and Baraka suture zones, the Central African fault zone, or the Marda line. Further evolution introduced en echelon fracture systems of Aqaba orientation as major structural trends in the northern Red Sea, whereas symmetrical extension by sea floor spreading began in the axial trough of the southern Red Sea. The central Red Sea represents the zone of transition between these two contrasting domains. The significant changes acrossmore » as well as along the rift cannot be explained by using a single pole of rotation to describe the separation of Arabia from Africa. Instead, several segments of both flanks have to be considered independently.« less

Evolution of the eastern Indian Ocean since the Late Cretaceous: Constraints from Geosat altimetry

We propose a new model for the tectonic evolution of the eastern Indian Ocean from the Late Cretaceous to the present. Two types of data are used to improve previously published reconstructions. First, recent reinterpretations of seafloor magnetic anomalies, between Australia and Antarctica and in the Wharton Basin, provide new constraints on spreading rates and the timing of major reorganizations. Second, vertical deflection profiles (i.e., horizontal gravity anomaly), derived from 22 repeat cycles of Geosat altimeter data, reveal the tectonic fabric associated with fracture zones. These new Geosat data provide tight constraints on paleospreading directions. For example, three prominent fracture zones can be traced from south of Tasmania to the George V Basin, Antarctica, providing an important constraint on the relative motions of Australia and Antarctica through the Late Eocene. In addition, the Geosat profiles are used to locate the conjugate continental margins and continent‐ocean boundaries of Australia and Antarctica, as well as the conjugate rifted margins of Kerguelen Plateau and Broken Ridge. Based on a compilation of magnetic anomaly data from the Crozet Basin, the Central Indian Basin, the Wharton Basin and the Australian‐Antarctic Basin, ten plate tectonic reconstructions are proposed. Reconstructions at chrons 5 (11 Ma), 6 (21 Ma), 13 (36 Ma) and 18 (43 Ma) confirm that the Southeast Indian Ridge behaved as a single plate boundary since chron 18. The constraints from the Geosat data provide an improvement in the fit of the Kerguelen Plateau and Broken Ridge at chron 20 (46 Ma). To avoid overlaps between Broken Ridge and the Kerguelen Plateau prior to their breakup, our model includes relative motions between the northern and southern provinces of the Kerguelen Plateau. Finally, we examine the implications of our model for the relative motions of India, Australia and Antarctica on the tectonic evolution of the Kerguelen Plateau and Broken Ridge, and the adjacent Labuan Basin and Diamantina Zone, as well as the emplacement of the Ninetyeast Ridge and the Kerguelen Plateau over a fixed hot spot.