The advent of satellite altimetry and the detailed ocean-floor topography derived from it in the 1990s led to the opportunity to test models of Gondwana reconstruction by going back to first principles using paleogeographic modelling software. While evidence may still be incomplete, this will always be the case. This is no excuse for not quantifying simple, defensible models that are driven by the 'photo-geology' of the ocean-floor and that can be tested against other data. At the same time, perhaps new ideas can help steer future investigations to where new data will be the most pertinent. What follows is a summary of the main findings to September 2026.

We have used ocean floor topography (satellite altimetry, Smith and Sandwell 1998) as the primary control for a refined model of Gondwana dispersal. We have used the CPSL ‘Atlas’ plate-modelling software and their ‘Feb04’ model (Smith, unpublished) as the starting point Animation A. Virtually all their original rotation parameters have been replaced over 20+ years. We have worked from first principles so the result is as independent as possible of published plate models.

The outlines of the Precambrian terranes of Gondwana have been defined from geological maps, including those of the new geological map of Gondwana (ref). The margins of Precambrian terranes have been refined using aeromagnetic coverage to show where Precambrian rocks are only thinly covered by younger cover (in places extending well offshore, such as in the Great Australian Bight for example) as opposed to where the younger cover is thick and the basement has been faulted to depth (even inland, such as northern Mozambique) during the rifting of Gondwana disruption and later.

We have concentrated on events prior to C34 (83.64 Ma, Santonian, GTS 2020 used throughout). After this time, ocean growth is relatively well-constrained by observed marine magnetic anomalies (world database, Animation C. Before this time there is a period of about 40 My devoid of anomalies (Cretaceous Quiet Zone, KQZ, 121.4-83.64 Ma). Before M0 (121.4 Ma) observations of M-series anomalies are limited or too close to conjugate margins to resolve paleo-positions with certainty. The conjugate margins are of greatest interest in resource exploration.

We have worked with Euler Interval Poles Animation E since great and small circles about such poles define the rift stretching direction and the strike direction of transform offsets respectively. This assists in the rigorous interpretation of the ocean-floor topography which repays the extra effort involved using interval poles.

We have used a limited number of ‘waypoints’ at specific times to determine when changes of interval pole apply across the whole system. These mostly coincide either with the dates of marine magnetic anomalies or with the boundaries between specific stratigraphic stages.

Small circles about successive interval poles will be co-linear where new lithosphere is being created. If the pole position changes in its position normal to the growth direction only the curvature of the growth path will change; a closer pole indicates more curvature in the path described, a more distant pole less curvature. Most of the big mid-ocean ridges active today operate largely in the ‘Euler tropics’, i.e. the rotation pole is 90 degrees distant from the most active part of the ridge. A fundamental change in spreading direction must lead to a reorganisation of the active rift system at the ridge. Usually the accommodation zones are preserved in position while the orientation of the active ridge changes. A totally new path for the ridge system may well result with a fragment of old ocean along with a defunct ridge section being left behind on one of the plates.

We have refined the original fit of the Precambrian pieces of Gondwana by fitting the clearly defined anomalies recorded unequivocally in satellite altimetry around most continental margins. While the precise origin of these features (we call them ‘gravity margins’) may be uncertain, the similarities in geometry observed by fitting conjugate anomalies is persuasive of a common cause Animation B. The resulting ‘fit’ is considerably closer than that of the de Wit et al (1988) geological map of Gondwana. This approach, while often contested, immediately avoids two questions arising from the loser fits: (1) What geological material filled the gaps? and (2) Where is it now? Our gaps are no bigger than the quantity of Precambrian continental crust that we expect to have been stretched and buried in the pre-drift rifting process. There is often a case for magmatic addition to the stretched crust, not mention underplating and other methods of thickening the extended crust. The main difference in our result from that of Smith and Hallam (1970) are explained in a News item.

If extension of continental lithosphere in the extended zone between true continent and true ocean has a beta factor of 2.0, then there should be an overlap of 100 per cent of the conjugate extended zones in their reassembled positions.

The start of Gondwana dispersal is taken as 184.2 Ma (Toarcian). There may be arguments for some dispersion preceding this time, for example during Karoo (Permian to Triassic) rifting [Animation T[(https://www.reeves.nl/gondwana/articulated-africa). This could be followed up further. However, earlier extension should not be such that is has to be partially reversed to achieve a later continental configuration.

Since oceanic crust is created by intrusion at mid-ocean ridges and the subsequent separation of pre-existing oceanic crust occurs symmetrically about that ridge, we have paid particular attention to modelling the paleo-positions of all mid-ocean ridges, in addition to those of the continents Animation H. In the vicinity of minor fragments, it is the most likely position and activity of the minor ridges that constrains the construction of credible local models.

The geometry of each major mid-ocean ridge is surprisingly constant over long periods of geological time. The result is that mid-ocean ridges are, to a great extent, self-replicating. Offsets in the ridge – accommodation zones in the rift or transform faults in the oceans – give rise to fracture zones that may be traced across oceans, often for thousands of kilometres.

Ridge jumps are limited in number and can often be interpreted from their record in the sea-floor topography. The preserved lengths of fracture zones can be assumed to have been coincident and colinear at the time of their creation. Hence the principle of telescoping fracture zones (Reeves and de Wit, 1990; Animation F) has been paramount in determining the paleo-positions of the continents. Where available, M-series marine magnetic anomalies Animation D have been used to calibrate the ‘telescoping’ against geochronology.

The two largest fragments of Gondwana are familiar as present-day continents ‘Africa’ and ‘Antarctica’ and their respective oceanic sections of their tectonic plates. The ocean-crust record of their early separation is, however, confined to a narrow strip of ocean (about 600 km in width) that is known as the Africa-Antarctica Corridor (AAC) (Reeves and de Wit, 1990; Animation K. This strip forms part of both main plate circuits, namely (1) Africa-South America-Antarctica-Africa and (2) Africa-Antarctica- India-Madagascar-Africa. Accurately tracking the relative motions in the AAC pre-M0 has only become possible since the fundamental magnetic survey work of König and Jokat (2010).

Intrusion and extrusion attributable to ‘large igneous provinces’ is familiar on land (ref). Usually a far larger volume of magmatic output has accumulated on oceanic crust and is now seen as oceanic plateaus large and small, seamounts and other edifices in sea-floor topography Animation I. Relating the provenance of all this magma to active plumes in the earth’s mantle requires a plate model in which Africa itself moves with respect to the ‘mantle reference frame’. We have adjusted the track of Africa to maximise the coincidence of magma output to the location of plume heads across the whole of the area occupied by the Gondwana continents.

It then emerges that the Bouvet plume is central to the story of Gondwana dispersal and its activity can be traced at least as far back in time as the Karoo magmatism, dated at 182 Ma (ref), across much of southern Africa. At this time the Bouvet plume head lay below Mozambique, near the starting point of the AAC and the Mwenezi (formerly Nuanetsi) igneous centre (Cox et al, 1965). Its activity tracks the subsequent locality of the triple junction between the three large plates, Africa, Antarctica and South America Animation M.

Since we have included the paleo-positions of the mid-ocean ridges in our model, we can now show how their positions over time relate to the constellation of plume heads recognised in the South Atlantic and Indian oceans. A key result is that, while most people are aware of the continents being in motion, the system of mid-ocean ridges separating Gondwana have remained remarkably constant in their position with respect to the mantle-plume reference frame Animation J.

The separation of South America from Africa is classically simple, with the exception of some smaller fragments around the latitude of Sao Paulo Reeves and Camoes, 2021. The separation of East and West Gondwana was less simple.

Madagascar is a clear example of a fragment that initially left the Africa (West Gondwana) plate before joining it again later. Further south, around the Bouvet plume head, there was a number of small fragments with complex tectonic histories Animation L. Understanding these has been stalled by repeated assertions over many years that the Mozambique plains and the Agulhas plateau are ‘continental’ in nature. In both cases the crust is indeed very thick but post-dates Gondwana break-up. Thick (more than 10 km) accumulations of magmatic and sedimentary rock there rest on either transitional or oceanic crust. A kinematic model showing how, for example, the Agulhas Plateau (larger than Iceland!) gets left behind on the Africa plate appears in Animation O.

Reviewing the process of disruption across East Gondwana, we find that the Davie fracture zone, the Wallaby-Zenith fracture zone and the proto-Owen fracture zone together define the rotational movement of India and Madagascar from about 142 Ma until the mid-ocean ridge between Madagascar and Africa is abandoned at about 118 Ma Animation P. Its demise is recorded in the topography of the AAC at this time as well (just SW of Madagascar) as the area of the small triple junction Africa-Madagascar-Antarctica created from 142 to 118 Ma as a result of this earlier plate configuration.

The history of development of the Southwest Indian Ridge is complicated by a number of ridge jumps Animation Q. A brief explanation is given in the 2025 Poster. A number of ridge jumps have to be considered to fully understand this history. The location of some of them is still unclear.

The position of Sri Lanka and its separation from India and Antarctica is confined by these neighbouring continents during break up. It is only just possible to rotate Sri Lanka without compromising the principle of not consuming new ocean crust once it has been created. The result does appear to be confirmed by the ocean floor topography off conjugate Antarctica Animation R.

My original interest in the (largely hidden) geology of Africa has been displaced by the fascinating story of the creation of the oceans that separated Gondwana. Reverting to Africa, the tight re-assembly of Gondwana we advocate is not possible while the geometrical outline of Africa is retained in its present shape. The East Africa Rift has to be ‘undone’, as well as the Cretaceous rifting across west and central Africa. While the relative movements across these rifts are small in comparison with continental-scale drifting, the movement of, for example, northwest Africa against central Africa makes changes of hundred of kilometres for the paleo-positions of America (North and South) once re-joined to Africa Animation T. The geology of the fit of NE Brazil against its conjugate in the African Gulf of Guinea is an undertaking that deserves further attention Animation U.

We have also raised the possibility of Phanerozoic movements on the Southern Trans-Africa Shear System (STASS) and the Mwembishi shear zone Animation S as part of the ‘Karoo’ (Permian-Triassic) systems of Africa (and their time-equivalents in India and Anartica).

Finally, the possibilities of representing African geology as a series of GIS ‘layers’ that appear over geological time is indicated in Animation V. Much is yet to be learned!

(1). Why is it that, with so much tectonic activity going on 150 to 120 Ma, this interval has so few ‘golden spikes’ in the International Chronostratigraphic Chart (ICC)? Every period of similar length in Phanerozoic time has more. Only quite recently were the Barremian, Valanginian and Hauterivian stages identified from the earlier single ‘Neocomian’ stage.

(2). Is there evidence in the stratigraphic record of southern Africa of the huge Morokweng impact? This event is dated precisely at 146.06 Ma while the Jurassic-Cretaceous boundary itself is only placed at approximately 145 Ma in the ICC. The event appears large enough to have had global consequences. If not, why not?

It is easy to make continent-to-continent fits locally. But errors in such fits have a magnified effect at distance; a rotation of one large fragment by just a few degrees locally requires hundreds of kilometres of displacement of that fragment 90 degrees away. Fits therefore have to be adjusted across the whole of the Gondwana reassembly, not taken in isolation. For this reason, serious work should be done within the context of geometrically defined digital maps of all Gondwana. It follows that ‘hand-waving’ and ‘sketch maps’ should be things of the past.

Continental motions are assumed to be generally smooth. Large areas of ocean growth show little sign of irregularity or interruption. We have therefore kept ocean growth regular over long time intervals unless there is evidence to the contrary. Abrupt changes without evidence we class as unnecessary invention whereas we have always been guided by minimising hypothesis.

When the work started, at the height of the early explosion in PC use, it was assumed that within a few years all tech-savvy earth scientists would be using paleo-reconstruction software routinely. Sadly, this still seems not to be the case and, even worse, much of the literature evidently includes re-use of a body of published (but possibly-erroneous) early interpretations that predate modern datsets and are often, then, in need of critical re-appraisal.

It is relatively easy to match two conjugate margins in isolation. As the work has evolved, the need to build the model holistically - across the whole of Gondwana - has become accepted as a necessary constraint on the validity of the model itself. It also gives a robust framework for testing past events in local areas where added complexity may exist. Very often 'blue sky thinking' still prevails in the community where global models should be providing some form of 'air traffic control'.

To bring new ideas to the attention of all those open to robust new thinking, a series of informal papers has been written with the aim of documenting progress quickly and sharing results with others as rapidly as possible. Some of the work has been written up and published formally but, of course, this process lags way behind what is being discussed actively with users from day to day.

The following documents may be seen as a series of discussion papers that invite comment, particularly from those with (preferably non-confidential) local knowledge and/or experience that can help confirm, deny or fine-tune the results. Generally speaking, the less recent papers are the most in need of revision. Some older papers have been totally superceded. But, best of all, join in the discussion!

A series of posters presented at the annual Netherlands Earth Science Congress since 2020 are accessible below and may provide the reader with rapid introductions to some of the main conclusions.