2nd Gondwana Symposium, 649-652
Capitosaurs have a long history which has been adequately summarized by Welles and Cosgriff (1965). They recognize three valid genera, which in order of appearance are Parotosaurus (Bunter-early Muschelkalk), Cyclotosaurus (Upper Muschelkalk-Lower Keuper) and Paracyclotosaurus (Upper Keuper). Howie (1969 - in press) proposed a new species of Parotosaurus, P. pronus, for a form in which the tabular horn expands in two dimensions only to approach the squamosal. It is distinguished from P. brookvalensis which has a globular expansion on the end of the tabular horn. Howie also raised the possibility that the unornamented closure of the otic notch of Paracyclotosaurus davidi may be a gap filled with matrix. She also proposed the likelihood of the presence of an anterior palatal vacuity in this species and concluded that Parotosaurus pronus and Paracyclotosaurus davidi are remarkably similar and may be closely related. The purpose of this paper is to provide the first description of a Capitosaurid amphibian from the Triassic of Zambia and to try and fit it into the Southern African stratigraphic sequence. No attempt will be made to correlate the South African Triassic with the European. A revision of the South African amphibian material is long overdue.
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2nd Gondwana Symposium, 395-408
The deep hole oil exploration drilling program initiated by Soekor in recent years has contributed much towards unravelling the unknown subsurface geology of the Karoo and Cape Systems in South Africa. The most important lithological changes in the sub-surface are illustrated by means of borehole columns, and analyzed by isopach, facies and structure contour maps. Problems arising from existing unsatisfactory definitions of the boundaries of major subdivisions are discussed. Preferred upper contacts of the Ecca and Dwyka Series are respectively the top of the main mass of dark gray Ecca shales below the base of the lowermost massive sandstone and the top of the massive tillite following upon the transition zone of dark gray shale with beds of tillite.
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2nd Gondwana Symposium, 451-454
A study of the "crystallinity" of illite as measured by means of the Kubler index may give an indication of the amount of contact metamorphism which argillaceous sediments have undergone. However, care should be taken with the way specimens are treated and a thorough knowledge of the mineralogy of the specimens is necessary. It is suggested that individual results from one laboratory should not be compared with those of another but that in such investigations trends rather than absolute values should be taken. A comparison of the Kubler indices with the nature of the organic matter in the sediments may then make the Kubler indices a valuable indicator for the source rock potential of the sediments.
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2nd Gondwana Symposium, 313-320
The Molteno Stage is characterized by a cyclic pattern of deposition which has been divided into four major facies according to lithology, grain size, and sedimentary structures. The basal facies (A) of conglomerate overlying an erosional surface appears to be the result of erosion and deposition within a braided river channel wandering across a floodplain. The overlying sandstone facies (B) has been divided into three subfacies and shows all the characteristics of a modern point bar complex. The fine sandstone, siltstone, and silty shale facies (C) represents a transitional facies deposited mainly from suspension in the quiet parts of the channel or in abandoned channels during low water. If the clastic facies in the sequence represents channel deposits then the shale and coal facies (D) probably records overbank deposits from flood waters in the quiet back-swamp areas of the flood plain. The environment was permanently inundated by water of such depth as to allow for the growth of plants and the formation of peat swamps.
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2nd Gondwana Symposium, 197-204
The result of investigations pursued during the past decade are outlined under the heads of: - Stratigraphy and lithology; Palaeocurrents; Stratigraphic maps and tectonic framework; Depositional environment and palaeo-geography; Age.
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2nd Gondwana Symposium, 125-138
Since this review is aimed at testing current ideas on predrift reassembly of the Gondwana area, consideration of Cretaceous marine invertebrate faunas is here omitted, because supporters of continental drift generally agree that all southern oceans were in existence during this geologic period. Let us then briefly recapitulate.
(1) For the Late Precambrian we can postulate a shallow sea covering parts of Australia and South-West Africa. No equivalents of the Ediacara fauna have been reported so far from South America, Peninsular India, and Antarctica, but the fauna is widespread in other parts of the world.
(2) In the Cambrian the Archaeocyatha fauna of Antarctica shows poor agreement with that of South Australia. If the two faunas had existed in one continuous trough one would expect the similarities to have been much greater. The Middle Cambrian Redlichia fauna is a Tethyan one, the Upper Cambrian Mindyallan fauna of Australia has close relationships with the Kushanian fauna of China. Middle and Upper Cambrian faunas of Antarctica seem to have few or no correlatives in South Australia.
(3) In the Ordovician, eastern Australian graptolite faunas have close relationships with those of western North America. Ordovician cephalopods of Australia show close affinities with eastern Asia and North America. The rocks of the Table Mountain Series have been proven to be mostly of marine origin, containing an Ordovician fauna, and Rust wrote about "gigantic surf" that pounded South African beaches in Ordovician times. At least parts of Cape Province were covered by the sea during the Ordovician and a shallow transgression occurred in Natal. The source of these transgressions can only have been an ocean situated to the east and south, and probably also to the west, of South Africa.
(4) Our knowledge of marine Silurian is small. If indeed, as seems most likely, the uppermost part of the Table Mountain series is marine and of silurian age, marine conditions in the western Cape Province must have continued from the Ordovician onward for some time into the Silurian. Marine Silurian containing little known faunas is also present in western Australia, and in the Parana Basin of South America.
(5) In the Early Devonian a marine biogeographic graphic (Malvinocaffric) province is clearly delineated, comprising parts of South America, South Africa, and Antarctica but not Australia and New Zealand where Early Devonian faunas are equally clearly are equally clearly of Eurasian affinities. In Late Devonian times European affinities of faunas, especially in northwestern Australia, are even closer.
(6) Carboniferous faunas of the Gondwana region are not well known. Since they are predominantly brachiopods they are also difficult to correlate. The difficulties of trying to reconcile the distribution of foraminiferal biogeographic provinces with the continental drift picture have been pointed out.
(7) The importance of the rich Permian faunas in western Australia and their strong Tethyan affinities cannot be overemphasized. Presence of these faunas here, and of Silurian, Devonian, and Carboniferous faunas that preceded them, rule out any suggestions to weld the western Australian margin firmly to the Indian shield. Madagascar which is usually pushed around quite a bit on continental drift maps has a small Late Permian fauna, including tectonic ammonoids. These faunas occur on the west side of the island. It is therefore not possible in the Late Permian to weld the west coast of Madagascar to the east coast of Africa nor to the east coast of India as some reconstructions have suggested.
Turning to the southern Atlantic Ocean, we note that presence of marine Cretaceous rocks on both sides has often been cited as evidence for the "opening-up" of the ocean at this time. We now know that Permian marine rocks are widely distributed in south marine rocks are widely distributed in South-West Africa, South Africa, and the Parana Basin of South America and that, on this basis, an equally good case can be made for the "opening-up" of the South Atlantic in Permian time. Because of wide distribution of marine Late Precambrian and Palaeozoic on both sides of the South Atlantic, Stille, as long ago as 1948, concluded that this ocean must be of great age. More recently this view, although hotly disputed by others, has been advocated by Biswas and by Meyerhoff.
(8) Very significant records of marine Lower Triassic are present in Madagascar and western Australia, furnishing evidence of the continued existence of marine waters to the west of these lands. (9) Both in Madagascar and in western Australia a hiatus in marine sedimentation exists that comprises the Middle and Late Triassic, but in the Jurassic marine deposition was again resumed and led to accumulations of sediments of great thickness. There are in this entire record of marine faunas in the Gondwana area a few facts that may be reconcilable with continental drift, but there are many more that are not. At any rate, in no discussion of continental drift and predrift reassembly of the continents must the facts presented here be ignored. A scientific theory must fit all the facts, not just selected data.
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2nd Gondwana Symposium, 483-490
The tectonic framework of sedimentation during the Dwyka Period in Southern Africa is portrayed on a neotectonic map which delineates the various tectonic elements during the Dwyka Period. From a detailed paleo-ice-flow study the major highland source areas were found almost to enclose the Karoo Basin with a main opening in the north-western corner and a less prominent opening in the south- east. From the north the land sloped gently from a mildly positive tectonic area to a stable shelf region; this gave way to a mildly negative tectonic and unstable shelf area which also stretched into South-West Africa. A hinge line in the southern Cape and Natal separated the unstable shelf area from the strongly negative troughs of deposition in the southern Cape and Natal. A comparison between this tectonic framework and that of adjacent Gondwana countries during the Dwyka Period would aid in the reconstruction of Gondwanaland.
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2nd Gondwana Symposium, 209-211
The surface upon which the Dwyka Tillite was deposited is represented by a map of the Sub-Karoo geology. This illustrates the geology as it would appear at present if the rocks of the Karoo System were removed. The Sub-Karoo geology of the central part of the Karoo Basin consists of granite, while in the more northern parts rocks of the Swaziland System are widespread. Towards the periphery of the Karoo Basin rocks more recent than the Swaziland System and granites make their appearance.
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2nd Gondwana Symposium, 441-445
The name Lebombo Stage is proposed for the thick assemblage of acid rocks overlying the basalt of the Drakensberg Stage of the Karoo System. This new stage is subdivided into three suites. The rocks of the Lower Lebombo Suite have the composition of andesite, dacite and rhyodacite; they occur as pyroclastic flow breccias and pyroclastic breccia dykes, massive, jointed and vesicular lava and tuff. The Middle Lebombo Suite, which consists of andesite, basalt and dolerite intrusions, is poorly developed in this area. The rocks of the Upper Lebombo Suite have the composition of trachyte, rhyolite, igneous quartz veins and the hypabyssal and plutonic equivalents of the trachyte and rhyolite. They occur as ignimbrites and associated tuffaceous deposits, pyroclastic flow breccias, massive lava and fairly extensive intrusions. There are also minor sedimentary deposits. The hypothesis is presented that the sequence of eruption of the rock suites is determined by tectonism. During phases of tension basic magma was unrestricted and could flow forth freely. When tension was released the flow of the basic magma was restricted causing its upper portions to assimilate some of the overlying Karoo sediments. Together with differentiation in the magma chamber this led to the production of the acid rocks in the sequence.
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2nd Gondwana Symposium, 461-468
An interesting feature of the Central Witbank Coalfield is that the coal in the three major seams is of better quality there than it is to the east, west and south of this area. The reason for this quality difference appears to relate principally to the higher dry ash-free calorific value and lower inherent moisture content of the Central Witbank coals. Explanations of these quality anomalies, such as difference in (a) environment of deposition, (b) plant species contributing to the coals, (c) thicknesses of superimposed strata, and (d) degree of intensity of dolerite intrusion, are discounted. A striking correlation between low inherent moisture of No. 4 Seam coal and the distribution of pre-Karoo felsite and pyroclasts is shown. This correlation is not exact but it is felt that the heat flow characteristics of these rocks, or of the region in which they happen to occur, must have affected the overlying coal seams during their history.
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2nd Gondwana Symposium, 627-635
Seven arthropod trails and four arthropod resting impressions are described from the late Carboniferous Dwyka Series in northern Natal. Most of the animals responsible for these trails and impressions possessed several pairs of walking appendages and may have been early paracarids or syncarids. The deposits at this horizon are of glacial origin and consist of varved shales which appear to have accumulated in freshwater periglacial lakes.
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2nd Gondwana Symposium, 205-208
In the Districts of Willowmore and Steytlerville a lenticular band of dark fissile shale (maximum thickness of 164 m) which may be overlain by a band of greenish sandstone, cross-bedded in parts and of the same maximum thickness, parts the main mass of Dwyka Tillite from a basal 94 m dark argillaceous tillite, containing prominent lenticular bodies of white plicated quartzite. This fissile shale contains scattered lenses of tillitic material, and is not varved. These shale and sandstone bands wedge out laterally.
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2nd Gondwana Symposium, 111-124
This paper reviews the early tetrapods of the continental areas believed to have been parts of ancient Gondwanaland, citing evidence, pro and con, concerning the possible early direct terrestrial connections between these areas. In this study of vertebrates discussion of fossil fishes is omitted and attention confined almost entirely to the continental tetrapods of the Permian and Triassic. Some notes on fishes and on tetrapods of other periods are given in concluding sections.
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2nd Gondwana Symposium, 457-460
In Angola alkaline complexes are probably Cretaceous. In Brazil the age of the complexes is a matter of discussion. The complexes cut Precambrian metamorphic rocks. They are believed to be early Jurassic in age. It seems that the period of intense tectonic activity responsible for the referred alignments in Angola and Brazil was the same and occurred before the translations of the continents. Subsequent igneous activity was concentrated along these lines of crustal weakness and resulted in the emplacement of igneous complexes. When a study of age determinations on the alkaline complexes of Angola and Brazil is carried out we may perhaps come to more interesting conclusions.
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2nd Gondwana Symposium, 139-149
"Every part of Gondwanaland has certain plants that are unique in that they are unknown elsewhere. Whenever one of these is located in another area it becomes a valuable link, and possibly an index fossil for particular zones of different continents". Four examples of hitherto undescribed forms are selected for description and discussion. They are (1) Taeniocrada, a lower Devonian link between Africa, Europe and Argentina; (2) Gangamopteris obovata Carr, and Walikalia Hoeg and Bose; (3) Plumsteadiella which links southern Transvaal and Brazil; (4) Phyllotheca etheridgei Arber and Dictyopteridium sporiferum Feistm linking Natal, Queensland and India.
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2nd Gondwana Symposium, 433-439
In the Ndedema Valley at the foot of the Drakensberg escarpment near Cathedral Peak, Natal, a basal lava flow of the Drakensberg Volcanic Stage of the Stormberg Series of the Karoo System has all the characteristics of a pillow lava. The basal flow showing pillow structures is 6 metres thick and is overlain by a succession of normal basalt flows having a maximum residual thickness of 1 400 metres. This occurrence of pillow lava substantiates the generally accepted view that although the underlying Cave Sandstone Stage accumulated under predominantly desert conditions, an aqueous environment existed locally.
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2nd Gondwana Symposium, 491-499
Three broad and contrasting paleotopographic zones, forming part of the foundation to the late Palaeozoic glacial deposits of the Dwyka formation, have been recognized in the northern half of Natal, an area of about 5 000 square miles in the eastern region of South Africa. Each zone is associated with a distinctive development of the Dwyka formation. The trends of pre-Dwyka valleys and contours on the subsurface provide information on local and regional preglacial paleoslopes which are consistent with the pattern of glacial striations previously recorded for this region. The widespread occurrence of two strongly divergent sets of glacial striations can be attributed to the influence of topographic obstructions on the flow of a single ice-sheet, in contrast to the current opinion (du Toit, 1921) that two distinct ice-sheets moved across this region. A reconstruction of the pre-glacial paleogeography suggests that the ice-front had a major lobate form during the early and late stages of the Dwyka glaciation. This concept is consistent with the restricted distribution of fluvial interglacial Dwyka sediments in northern Natal.
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2nd Gondwana Symposium, 225-232
The small list of fossils known from the Eurydesma Beds has been augmented by the discovery of a Goniatite, of Radiolaria, several genera of Foraminiferal and an Asteroidean. The known fossils comprise two main categories: (1) free- swimming, planktonic and pseudo-planktonic forms; (2) neritic forms adapted to agitated water and a rough bottom. The former are found in concretions in the shales and the boulder-bearing mudstones, the latter especially Eurydesma are confined to turbidite layers interbedded in the mudstones. They did not live at the sites where they are found. The original slope of the floor of the embayment can be deduced from the sedimentary features of the turbidite beds. This slope was inclined towards the south-southwest. The embayment had a wide opening in the southwest. It included the now isolated Warmbad basin.
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2nd Gondwana Symposium, 621-625
A Goniatite of the genus Eoasianities, sub-genus Glaphyrites, was found in a siliceous phosphatic radiolaria-bearing nodule near Schlip, lat. 24°02'S, long. 17°08'E. At Schlip similar fossiliferous radiolaria-bearing nodules occur in a shale interbedded between a basal moraine and an overlying tillite. Closely related Goniatites of the same genus and subgenus, occurring in a similar stratigraphic position, have been reported from Uruguay. The restoration of Africa and South America to their assumed predrift positions brings the two occurrences into close proximity.
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2nd Gondwana Symposium, 309-312
As a result of two decades of intensive collecting of Beaufort reptiles and the concurrent determination of the exact stratigraphical horizon of each "find", the author revises the nomenclature of the palaeontological zones within the Beaufort succession, discarding the Endothiodon and Procolophon zones of the earlier classification and proposing the following subdivisions of the series: Upper Stage - Cynognathus zone Middle Stage - Lystrosaurus zone Daptocephalus zone Lower Stage - (Cistecephalus zone (Tapinocephalus zone) (see original abstract in above-mentioned Magazine for complete abstract).
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2nd Gondwana Symposium, 687-689
The stratigraphy and palaeontological make-up of the Cistecephalus zone of the Beaufort Series is briefly discussed. The physical environment under which the plants and animals of the zone lived appears to have been constant during the deposition of the beds of this zone. The possible food and energy relationships of the more common plants and animals are considered. It is concluded that there were too few ecological niches to accommodate the large number of vertebrate species that have been described from this zone and that taxonomic subdivision might have been carried to extremes.
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2nd Gondwana Symposium, 73-97
The hypothesis of continental drift is approached from the point of view of paleocurrent analyses. A short revision of other approaches to the problem is made, including palaeomagnetism, sea-floor spreading and geologic similarities. The paleomagnetic evidences suggest that both continents were adjacent to each other until Upper Permian or Triassic times. In the Precambrian radiometric age determinations suggest also that both continents were adjacent to each other. The few paleomagnetic data available for the Lower Paleozoic rocks do not seem to be enough for a more precise determination of the pole position. There is no good agreement between the postulated pole and the paleoclimatic evidences for the Lower Palaeozoic sequence. The adjacent position of South America and Africa seems to be in agreement with the cross-bedding resultant vector obtained from sandstones, from Ordovician to Devonian age, deposits in the pre-Waterberg topography. Agglomeratic lavas are moderately developed whereas pyroclasts are rare.
A chemical analysis of unaltered trachyte shows high Fe and Ti contents. Sediments associated with lavas consist partly of volcanic detritus mainly derived from hydrothermal alteration products of lavas. A tuffaceous admixture is possible, but some types have been laid down by volcanic mud-flows or lahars, for instance a volcanic conglomerate with chlorite filled cavities is considered,to be derived from a hot lahar. Fine-grained ferruginous sandstone and siltstone in the Langkloof and Alma beds are probably also partly of volcanic origin. A lahar origin is also postulated for types containing cavities in the Upper Langkloof Stage. The focal area of volcanicity was situated east of Loubad and falls within a zone of centres of subsidence of the basin. This shifted to the north during deposition of the higher subdivisions. Extrusion most likely took place along fissures with local central eruptions. Field data and age-determinations indicate a comparatively small time interval between the final phase of the Bushveld Complex (intrusion of granite) and the initial phase of Waterberg volcanicity.
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2nd Gondwana Symposium, 233-240
Large areas of the southern Kaokoveld in South-West Africa are covered by sediments which are correlated with the Karoo System in South Africa. These sediments consist of a poorly developed basal tillite, which is of the same period as the Dwyka Tillite in South Africa. The tillite is overlain by shales, limestones and sandstones - a total thickness of 150 m. Above these sediments follows a zone of eolian sandstones, locally called the Etjo Sandstones. This is correlated with the Cave Sandstone stage in South Africa. These sediments are overlain by basalts and rhyolites of the Stormberg Series. If the above correlations are correct, the Ecca Series and Beaufort Series, as well as the Molteno and the Red Beds of the Stormberg Series in South Africa, have to fit in between the tillite and the Etjo Sandstones in S.W.A. However, to correlate to this detail over such distances, without markers, is not possible. Therefore, the sediments between the Dwyka Tillite and the Etjo Sandstones are simply referred to as the Karoo Sediments. A palaeocurrent analysis of the sandstones above the Dwyka Tillite indicates that the arenaceous material was deposited from many directions. Also, the undulating nature of the pre-Karoo floor suggests that these sediments were deposited in valleys between huge mountains. The Etjo Sandstones, however, which are of eolian origin, were deposited from the south-west.
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2nd Gondwana Symposium, 49-54
Although first brought to notice nearly 120 years ago, the Karoo System in southern Africa is far from having its detailed history fully delineated. For the most part, the rocks composing it were deposited under continental conditions and display lateral variations that depend on the local conditions that governed their modes of deposition. Broad time-correlations between the preserved rocks of the several regions in this large African area have been attempted from detailed studies of the vertebrate and plant fossils that they have yielded, and from the evidence afforded by the widespread glacial deposits that lie at the base of the succession. From this evidence a broad chronostratigraphic sequence has been suggested for the Karoo beds of southern Africa, beds that may cover a timespan of approximately 100 million years. There are, however, those who argue that it would be preferable to replace, or at least couple, this concept of a chronostratigraphic sequence by, or with, a lithostratigraphic succession. In the absence of decisive fossil evidence, it is not proven that the remnants of the glacially-derived material found at the, base of the Karoo system in various parts of southern Africa were synchronously formed, nor that these African tillitic rocks were contemporaneous with the similar materials occurring in other sectors of the hypothetical Gondwanaland.
The concept of discordance between lithological boundaries and time boundaries is by no means new - for example, E.C. Case discussed it, almost 50 years ago, in a memoir describing the varying position of red strata in the Permo- Carboniferous beds of the United States of America; but, as papers to be delivered at this symposium will show, it is still receiving considerable attention. Of the history of Karoo times in southern Africa there is still much to be learnt through tectonic, lithologic, sedimentological, sedimentological, palaeontological, and geochronological studies. Of the relationships between this history and that of the same period in other continental areas this symposium will yield further evidence.
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2nd Gondwana Symposium, 151-155
A public lecture given to explain briefly the objectives of holding a symposium on "the stratigraphy and history of the Gondwana system". Its purpose is to make and disclose observations and to discuss the relationships of the observations one to another, with the ultimate aim of deciphering the successive stages of earth history during the period of formation of Gondwana rocks.
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2nd Gondwana Symposium, 455-456
The occurrence of laumontite in samples of Beaufort and Stormberg sediments in the eastern and north-eastern part of the Cape Province is recorded. Certain tentative implications having a bearing on the conditions of sedimentation towards the close of Karoo times are discussed.
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2nd Gondwana Symposium, 99-109
The present distribution of late Palaeozoic deposits of glacial derivation in all the southern continents, and including India, is random with respect to latitude but may be explained without resorting to extra-terrestrial causes by the passage of a reconstructed Gondwanaland over the South Rotational Pole during Palaeozoic time. A slight modification of the reconstruction made by A.L. du Toit fits all the data on glacial paleogeography well, including the newest information from Antarctic glacial rocks and pole positions deduced from paleomagnetic studies. Major questions still confront us, however, with regard to circulation systems in the Palaeozoic oceans and atmosphere ultimately responsible for global precipitation patterns, and with regard to more local sources of moisture and accumulation areas.
The shape of Gondwanaland was long and relatively narrow the length stretching from Colombia in South America across southern Africa and East Antarctica to Queensland in northeastern Australia, and the width essentially being represented by the length of Africa from the United Arab Republic to the South African Coast. This continental block in the late Palaeozoic was positioned on the South Rotational Pole and, with its length lying at least 105 degrees of latitude, it served to deflect equatorial oceanic currents from their normal axial flow into north-south paths. In Early Carboniferous time, the west-flowing equatorial current was deflected by the eastern Australia coastline and by Coriolis force to meridional flow deep into a Gondwanaland sulcus near Cape Town, in a manner analogous to the actual deflection of the of the Equatorial Current to give rise to the Brazil Current. The presence of this warm, easily evaporated water within the Antarctic Circle facilitated the initiation of ice masses which grew to a major ice sheet centred in southern Africa. Prevailing westerly winds from the paleo-Pacific carried abundant moisture onshore to elevated ranges of the tectonically active Andean belt, leading to the development of smaller ice masses there. By Early Permian time, Gondwanaland had drifted so that the South Rotational Pole lay in East Antarctica and a major ice sheet extended into southern Australia. The Arabian shoulder of Africa deflected equatorial zonal flow into the high-latitude India- Australia sulcus in a manner analogous to the Early Carboniferous, and prevailing westerlies led to local ice centres in western Australia and Antarctica.
However, in the Permian, deflection of the counterclockwise oceanic gyre in the paleo-Indian Ocean became progressively less effective as the African segment moved out of the equatorial zone and as the Gondwanaland coastline tended toward a more latitudinal orientation. From these considerations we can see that many conditions were favourable for the initiation and migration of glaciation initiation and migration of glaciation in Gondwanaland in late Palaeozoic time and that much resulted from the motion of the supercontinent with respect to the rotation axis, so as to influence oceanic and atmospheric circulation patterns in the proper sense. The final consideration of course is that drift of Gondwanaland across the pole provided a landmass on which the glaciers eventually formed.
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2nd Gondwana Symposium, 343-370
The author gives here a summary of a memoir on the Palaeontology and Palaeobotany of Lesotho (in preparation). He studies here the Stormberg and the Drakensberg Lavas. The Stormberg, classically subdivided into three zones (Molteno, Red Beds and Cave Sandstone) is here divided only into two phases: one warm and humid phase, corresponding to the lower Stormberg (divided into 7 zones), and the other also warm but steppic and arid, corresponding to the Upper Stormberg (also divided into 7 zones). A division into zones is also given for the Drakensberg Lavas.
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2nd Gondwana Symposium, 409-420
Studies resulting from four years mapping and diamond drilling in the Siankondobo-Mulungwa region of the mid-Zambezi Valley have led to division of the Siankondobo sandstone and recognition of a new formation named Sinakumbe Formation. The Sinakumbe Formation, consisting of a turbidite sequence, underlies the Siankondobo Sandstone Formation in the Maze area. The former is correlated with the Sijarira Series of Rhodesia which has been dated between 600 and 550 million years, thus pre-dating the Karoo deposits by some 200 million years. Earlier authors have placed rocks of this formation in the lowermost Karoo beds. K symbols are introduced for formations of the Karoo System, and the basal formation is the Siankondobo Sandstone, which has been divided into lower and upper units. The lower consists of conglomerates, mixtites, varved sediments and siltstones, and the upper of massive sandstones. The lithological sequence suggests sedimentation in a basin affected by spasmodic subsidence and source area uplift.
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2nd Gondwana Symposium, 683-685
The braincases of Captorhinus, Sphenodon, Proterosuchus and Euparkeria are all of the same basic pattern. The retention of this primary pattern of braincase in thecodont archosaurs is unexpected and must be associated with some aspect of their life. All of them except Sphenodon have evidence of a kinetic skull, typified by the basipterygoid articulations and largely unfused pterygoids with a relatively long, free cultriform process. The lack of an ossified laterosphenoid and, in Proterosuchus and Captorhinus, a poorly ossified dorsal extension to the epiterygoid indicates that the braincase must have been free to move relative to the skull roof. The paraoccipital processes in all these animals fit into sockets in the squamosals, and these must have been well-placed to act as a major centre of rotation. Any fore-and-after stresses on the braincase would require a corresponding strut to reinforce the region between the basipterygoid and the paroccipital processes.
It is thus likely that in the line leading to the archosaurs, and as late as the Proterosuchia, cranial kinesis was important and that the ventral process of the opisthotic acted as a reinforcement on the side of the braincase. The ventral processes of the opisthotic reported by Robinson in the early lizards from the English Trias are very much more strongly developed than here and seem to divide the basisphenoid from the basioccipital with a club-shaped expansion at their lower ends. This probably indicates an early specialisation of the line leading to these early lizards and it is possible to see how this could have arisen from the more generalised state in e.g. Captorhinus. Finally, the presence or absence of an ossified lateros phenoid may be of use in distinguishing Proterosuchian and Pseudosuchian thecodonts. As Proterosuchus itself and Euparkeria lack this bone they may be conveniently placed together as Proterosuchians. One other genus which seems to lack the laterosphenoid is Shansisuchus, but the cond
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2nd Gondwana Symposium, 469-476
The distribution of glacial sediments and related facies in the Gondwana continents, supplemented by data from directional-current structures, preserved geomorphic glacial features, and published paleomagnetic data, confirm the inference of Du Toit and of King that late Palaeozoic glaciation in southern Africa and then-adjacent continents is largely due to the migration of united Gondwanaland across the south pole. Glaciation developed in the early Carboniferous in southern Africa and nearby South America, culminated in this region during late Carboniferous, and rapidly waned during the Permian. In Antarctica and Australia, on the other hand, continental glaciation waxed in the latest Carboniferous and culminated in the Permian. The timing of these waxings, culminations, and wanings is compatible with paleomagnetic information as well as with the concept of a united Gondwana super-continent moving across the south pole. Ordovician glaciation in the Saharan region, and possible tillites and associated glacial (?) strata in the Cambrian (?), Silurian, and Devonian of Brazil, suggest that earlier drift of the supercontinent brought the united Brazilian-Saharan region into the polar regime. This is supported by paleomagnetic data. Infracambrian and possible Cambrian glaciations of northern Africa and then-adjacent parts of Laurasia may also fit the migration. Comparisons of Palaeozoic paleogeographic configurations in the southern hemisphere with those of the Cenozoic in the northern hemisphere suggest that a basic cause of ice ages is the arrangement of continental masses and their effect on air-ocean circulation. During glaciation, latitudinal ocean currents were blocked or deflected poleward, and the circulation became more meridional. Moreover, the elevation of continents and location of highlands, the availability of evaporative moisture sources, the availability of evaporative moisture sources, the freezing and thawing of polar seas, the effect of snow and ice cover and frozen seas on the earth's albedo and the mean earth temperature, and the positioning and positioning and swinging of storm tracks along the polar weather front with the development of strong air-mass contrast all play a role. When many of these re-enforce, continental glaciation results. The causes of ice stages are therefore probably rooted in tectonic changes on an earth with a very mobile crust, and earth climates during the Phanerozoic have always been near a balance easily tipped toward or away from glaciation.
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2nd Gondwana Symposium, 55-72
The polar-wander curves, deduced from palaeomagnetic studies of rocks from South America, Africa, Australia, India and Antarctica are described. They have been used to deduce how these continents were arranged when they were united forming Gondwanaland. They also provide a new method of correlation of magnetic ages of rock formations in the different continents. The South Pole wandered across Gondwanaland from the vicinity of Dakar in the Lower Palaeozoic, through South Africa in the Lower Carboniferous and across Antarctica almost as far as Australia in the Permo-Carboniferous. It is deduced that Laurasia was joined to Gondwanaland throughout the middle and upper parts of the Palaeozoic era and that rifting between North West Africa and the eastern U.S.A. occurred at the end of the Triassic. Within Gondwanaland, the earliest movement appears to have involved Australia during the Permo-Triassic. The development of the South Atlantic appears to have started by the Jurassic. In the Late Mesozoic and Tertiary the polar wander curves for the different continents diverge when plotted against the Gondwana geography, showing that by then this had changed: the continents as we know them today were then drifting towards the positions they occupy on the contemporary world globe.
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2nd Gondwana Symposium, 447-450
The petrographic study of the rocks from Bokkeveld and Ventana shows a great similarity and homogeneity between the two groups of rocks. They should be considered as sedimentary rocks. They have been affected only by dynamic forces that did not produce high temperature values. This conclusion is confirmed by:
1. The observed structures seem to be the product of flow cleavage, responsible for the orientation of muscovite and chlorite flakes.
2. The chlorites are not metamorphic but diagenetic; this is suggested by the fact that the greatest intensity of their reflection is in 14 AU when the samples are calcinated. Also because most of the chlorites are interlayered with montmorillonite.
3. The composition of the plagioclases varies between 25-35% An. This is a too basic composition to include the rocks within a low grade regional metamorphic facies.
4. The study of the presence of mixed-layer clay minerals, which are extraordinarily sensitive to P.T. conditions. The total height of the illite peak at 10 AU and the secondary reflection at 10,5 AU gives a ratio ranging between 2,3 and 4,2. According to Weaver (1960) these values correspond to rocks without metamorphism or with "naissant metamorphism" respectively.
5. The mineral parageneses do not indicate the existence of a chemical equilibrium compatible with a regional metamorphism.
6. Epidote, fairly abundant in Bonete and Tunas Formations, should be considered of hydrothermal origin and not as a metamorphic mineral.
7. The borehole samples from Bokkeveld Group show indications of a mild metamorphism, while the outcrop rock samples show only diagenetic effects.
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2nd Gondwana Symposium, 501-509
Glacial sediments of the Lower Karoo Dwyka Series outcrop over an area of several thousand square miles in north-western Rhodesia. They comprise a varied lithological suite including tillites, glacio-fluvial sandstones and conglomerates, and limnoglacial varves and mudstones. At one locality they rest on a glacial pavement of Sijarira Group sandstones. The available evidence suggests that the area was one of moderate relief, with valley glaciers and possibly a small ice cap, discharging water across a glacio-fluvial outwash plain. A tentative Lower to Upper Carboniferous date is given to these deposits.
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2nd Gondwana Symposium, 321-341
The Cave Sandstone Stage of the Stormberg Series of the Karoo System is divided into three rock stratigraphical zones. The basal part (Zone 1) consists of massive, thick to very thick bedded, light brown and light red, very fine grained sandstone, silty sandstone and sandy siltstone. Irregular calcareous concretions and lenticular deposits with shallow water structures such as mudcracks, ripple marks etc. are abundant.
Zone II consists of alternating beds of massive and cross-bedded sandstone. Zone III consists of massive, thick to very thick bedded, very fine grained sandstone in the northern and western part of the area which grades laterally towards the east and south-east into massive silty sandstone, sandy siltstone and siltstone. Zone III is overlain by basalt of the Drakensberg stage, at the base of which layers of sandstone, which were most probably deposited in playa lakes, are found.
It is considered that the sediments of the Cave Sandstone Stage were deposited in the final relic of the primary huge sedimentary basin of the Karroo System. Local variations in thickness are mainly the result of an uneven surface on to which the lava flowed the early commencement of volcanic activities in certain areas which hampered sedimentation. Eolian cross-bedding is almost solely restricted to Zone II. The massive sandstone was first deposited by wind but sand-flows and filtering rain water in a semi-arid climate are believed to have destroyed the dune structures and resulted in normal bedding. Some of the sand was redeposited in huge playa lakes by sand-flows. The palaeowind directions indicated that the source area was situated towards the western side of the area and the main direction of transport was towards the east. The average grain of the cross-bedded sandstones decreases in the down-wind direction while the grain size distribution to some extent suggests primary eolian deposition. Although the sandstone is submature, mature, well rounded zircon grains, primary angular grains with diameters between 50 and 2 micron, and the general fine grained character of the Cave Sandstone suggest that the sediments were derived from a sedimentary source area which most probably consisted of rocks of the Beaufort Series.
Animal and plant life were relatively abundant during the whole period of deposition of the Cave Sandstone, although it was less abundant during the deposition of Zone II. When the two continents are fitted together, the paleocurrent pattern is peripheral to a large continental area located at the oriental part of South America eastward into Africa. The paleocurrents in both continents flow away from this common area.
The Ordovician-Devonian formations used in this analyses are (1) in Africa the Cape System and the Palaeozoic sequence of the Ahaggar in Central Sahara; (2) in South America the Caacupe, Furnas and Serra Grande formations. The Ordovician and/or Silurian glaciations indicate also the provenance of the ice from the same continental area as is inferred from cross-bedding measurements. The ice movement in the Sahara was to the north, while the ice flow in the Cape Province was to the south. The examination of the well-planed erosion surface which preceded the sedimentation of the Palaeozoic sequences indicates a semi-arid environment for its development. In the different areas studied, the well-planed erosion surfaces do not seem to be contemporaneous with each other. These surfaces were actually pedilanes and not peneplanes as usually stated.
The ice flow patterns deduced, for both Tubarao and Dwyka sequences, are suggestive of a former connection between Africa and South America. Nevertheless, complementary studies are still needed to solve many problems. During the Permian, the Karoo and Parana basins had a separate development as shown by paleocurrent analysis. In South America the data are still rather scarce. Good paleocurrent information is available for the Ecca and Beaufort sequences of South Africa. Cross-bedding measurements of the eolian Mesozoic sandstones, both in South America and in Africa, indicate the presence of the South Atlantic Ocean between the two continents.
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2nd Gondwana Symposium, 653-657
By reason of the sudden appearance of a well-represented and large vertebrate faunal assemblage in the lowermost Beds of the Beaufort Series, the underlying Ecca Series (lower Middle Permian) of South Africa should be one of the most important periods in the evolution of the Karoo reptiles. However, the lack of fossil discoveries in this series, together with the lithological evidence that the bulk of the sediments were deposited in shallow to deep water, have tended to strengthen the generally held view that conditions obtaining during this period militated against the presence of land vertebrates. The recent discovery of vertebrate fossils in Ecca defined beds is therefore of considerable significance, especially as they show certain primitive features which could be correlated with ancestral trends of the lower Beaufort dicynodonts.
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2nd Gondwana Symposium, 637-647
The trails each consist of a series of parallel waves. On the basis of relative positioning and amplitude, the various wave types are attributed to different appendages of a fish. The possibility that a tetrapod may have been responsible for the trails is, however, not excluded. It is possible to calculate the dimensions of the proposed fish involved by exploiting formulae derived by Bainbridge. A reconstruction is attempted, but this finds no counterpart in the fossil record. The direction in which the fish were swimming and the asymmetrical nature of the trails are discussed.
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2nd Gondwana Symposium, 29-47
Geological studies of the Gondwanas distributed in widely separated basin-belts (Plate I) commenced as early as the mid-nineteenth century in India. But an integrated analysis of their stratigraphic, tectonic and sedimentological framework by a co-ordination of interdisciplinary methods, however, received special attention only during recent years. Some of the notable advances in this respect are briefly reviewed.
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2nd Gondwana Symposium, 189-192
The Devonian sequence of Brazil, beginning with clastic sediments, lies mainly directly on crystalline rocks, except near the border of the Andean geosyncline, where Ordovician and Silurian layers are intercalated. Therefore two main basins of deposition have to be distinguished: the Andean geosyncline with a more or less complete marine sequence, and the Devonian to Carboniferous Gondwana basins, containing fragmentary clastic layers with only some marine ingressions.
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2nd Gondwana Symposium, 241-247
This paper is an attempt to establish the limits of the depositional basin of the Paganzo Group and to sum up the tectonic events that were associated with its formation and later disintegration. It is also intended to characterize briefly its depositional environments. All the sedimentary rocks deposited in this basin have been considered as belonging to the Paganzo Group, which has been divided into Lower, Middle and Upper Sections. Correlations between previously known formational units are indicated in Table 1.
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2nd Gondwana Symposium, 257-264
Some of the advances that have been made in knowledge of the Beacon Supergroup since the First Symposium in Argentina, Brazil and Uruguay in 1967 are summarised below under various headings. The sills of Ferrar Dolerite and extrusives of the Kirkpatrick Basalt are virtually comagmatic, and are co-extensive with the Beacon Supergroup, and references to them are therefore included in the bibliography.
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2nd Gondwana Symposium, 477-481
The extent and apparent continuity of the Paleozoic glacial deposits and the consistency in paleo-ice direction in Antarctica suggest an ice sheet of continental dimensions centred in southern Victoria Land. In the central Transantarctic Mountains 126 m to 395 m of glacial sediments were deposited from actively deforming temperate ice which flowed to the south-east. The central Transantarctic Mountains were possibly situated in middle latitudes during the glaciation, although the continental dimensions of the ice sheet suggests that it also extended into higher and lower latitudes. Between advances of the ice, streams, some of them quite large, flowed across the area and were locally diverted or dammed by the retreating ice front.
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2nd Gondwana Symposium, 541-542
One of the greatest technological advances of this century was the development of high speed computing machines. The use of these machines has advanced from mathematical toys through generalized mathematical tools into the area of information storage and retrieval devices. The last of these categories is one of the most exciting for the geologist. Digital computers are being made available for the simultaneous and direct use by many geologists. Karplus (1967, p.vii) has pointed out the key concepts in this evolution are 'on-line', 'man-computer' and 'time sharing'. These developments allow a more objective experimental approach to geology by giving immediate access to a data bank of relevant information, and providing a means of rapid hypothesis testing through a terminal at the geologist's desk.
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2nd Gondwana Symposium, 551-555
New data on relationship of fossil floras of various territories are somehow or other reflected on paleogeographic generalizations. The present paper deals with the Carboniferous and Permian floras in their relation to paleogeography. Existing views on this point were formed in the nineteen-thirties or earlier. The paleogeographical interpretation of the paleobotanical data, obtained during the past 10 to 15 years, is very sketchy. To fill up the gap as far as possible in a short paper is the main aim of the presentation, which, of course, can be in no way complete.
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2nd Gondwana Symposium, 593-598
Evidence from the Recent fauna and from the known Australian fossil insects is considered to indicate that the main evolutionary lines of the insects had been established before the earliest insects reached Australia from the Angara province towards the end of the Palaeozoic, probably in Mid-Permian time, by way of a partial barrier that enabled colonization by actively-flying, more rapidly dispersed endopterygote and hemipteroid insects slightly in advance of the less rapidly dispersed Blattodea and the orthopteroid insects.
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2nd Gondwana Symposium, 175-178
It is suggested that the geological age limits for Gondwana sequences should be extended from Early Paleozoic to Lower Cretaceous instead of the original limits, from Upper Carboniferous to Jurassic. The writer's previous paleogeographic and geotectonic studies indicated that South America and Africa were separate continents by Early Devonian time. The recent discovery of marine Ordovician-Silurian faunas in South Africa and in North-west Africa and the recent geotectonic recognitions in South America suggest that separation of the continents may have occurred earlier (Loczy, 1968b and 1969).
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2nd Gondwana Symposium, 169-174
The available Mesozoic and Cenozoic palaeomagnetic data from South America are critically analysed. These data are compared with the similar aged palaeomagnetic data from Africa and a history of the fragmentation of the South American-African block is suggested: (i) during the Triassic period neither relative continental displacements nor polar-wandering took place; (ii) the fragmentation of this western block of Gondwanaland and the origin of the South Atlantic Ocean occurred in lower Jurassic times, and (iii) during the Cenozoic South America and Africa drifted apart in a basically east-west sense. A tentative reconstruction of the relative positions of South America and Africa for the Mesozoic-Cenozoic transition, on the basis of palaeomagnetic and sea-floor spreading data, is given.
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2nd Gondwana Symposium, 179-188
Several palaeogeographic reconstructions suggested to explain the Permian transgression in Peninsular India are examined critically, and the one, by Shastri and Shah envisaging two incursions, at different times, is discussed in detail. It is pointed out that there is no justification for the presumption that Productids indicate warm climatic conditions, for numerous cases are known of Productids occurring in marine tillites. The close similarities in the Umaria and the Lyons Series faunas of Western Australia are emphasized and it is believed that the incursion must have been from the south-east. However, there was also an opening to the west and the subsequent Barakar river system must have found an outlet through it.
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2nd Gondwana Symposium, 193-194
A repeated sequence of alluvial flood-plain and sublittoral deposits is described from the Trias of southern Tunisia. Two seaward extensions of the flood-plain and two marine transgressions are recorded. Middle Triassic reptiles, including typical Tethyan nothosaurs and placodonts and a new heavily armoured archosaur, are present.
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2nd Gondwana Symposium, 381-394
Considerable difficulty is experienced in trying to correlate Permian marine sequences of Gondwanan countries with the world standard sequence. There are three reasons: much of the world standard is non-marine; its most closely studied fossils, Fusulinacea and ammonoids, are comparatively rare or sporadic in the Gondwanan realm (as over much of the rest of the world); and the brachiopods, bivalves, gastropods and polyzoa of the world standard, found also in abundance in Gondwana, have not been extensively revised. A model is therefore proposed for Gondwanan Permian, based on internal sequences from Tasmania, New South Wales, Queensland, Western Australia, New Zealand and the Salt Range. Eight subdivisions are recognised, and traced over these countries, and tentative correlations suggested with the world standard sequence. Support is expressed for the erection of an international subcommission for reconsideration of the Permian System, and the need to replace several of the present world standard stages with more satisfactory stratotypes.
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2nd Gondwana Symposium, 589-592
Several conchostracan beds occur at different elevations in the Antarctic Queen Alexandra Range (David Elliot Collection) and in the Patagonian Jurassic. Mauger Nunatak, Antarctica, contains a few specimens of the conchostracan genus Paleolimnadia. This genus also occurs in the Upper Permian and/or Triassic of New South Wales, Brazil, Bolivia, and South Africa. Conchostracans have been reported from Devonian fish beds of the Lashly Mts., Antarctica. Preliminary examination (N.Z. Geol. Surv. Collection) indicates preservation too poor for identification. Nevertheless a likely source is the Australian Devonian, although the lower portion of the Devonian-Carboniferous of South Africa was also available. Patagonian cyziciid conchostracans, two subgenera, from Canad¢n Asfalto formation (Tasch and Volkheimer, in preparation) have relatives in the Jurassic of Antarctica, Mozambique, India and elsewhere. Besides faunal similarity there is a more striking aspect of Mesozoic conchostracan occurrences in Patagonia, Central Transantarctic Mts. Victoria Land and Mozambique (Lebombo belt); fossils occur in freshwater interbeds of volcanic or intrusive sequences. Antarctic fossil insects point to a transantarctic migratory route from Permian through Jurassic (possibly Cretaceous) time (Sentinel Mts-Tasch Collection; Carapace Nunatak-Borns-Hall Collection, and older data). An outstanding feature of Antarctic insects (both Paleozoic and Mesozoic) is their affinities to Asiatic and/or Russian or Australian forms. These data require proximity of Australia and Antarctica, and grouping of southern hemisphere continents around- Antarctica from at least Devonian through Jurassic time.
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2nd Gondwana Symposium, 615-616
Three genera of freshwater lamellibranchs, Palaeomutela, Palaeonodonta and Kidodia, including 7 species, and a few scattered gastropods have been found in the Lower Beaufort beds (Upper Permian) of the Republic of South Africa and in Rhodesia. The lamellibranchs closely resemble forms from Tanzania and the U.S.S.R., and similar forms occur in South Burma, Ceylon and South America.
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2nd Gondwana Symposium, 617-619
Drilling and geological field activities along the eastern margin of Brazil (mainly in the Brazilian states of Bahia, Alagoas and Sergipe), and along the opposite margin of the South Atlantic Ocean in Western Africa (mainly in Gabon, Congo Coastal region and Angola) during the past decade have yielded much new geological and palaeontological information. Most of this information directly or indirectly affects the hypothesis of a former land connection between the two continents and its breaking up into the shape and position of the present-day continents. One group of new data relevant to the various problems of ancient continental connections between South America and Africa is presented here and offered for critical discussion. It concerns the stratigraphy and especially the micropalaeontology (ostracods) of the non-marine "Wealden" Series (Upper Jurassic? to Aptian in age) in the regions mentioned above and their striking similarities, lithologically and micropalaeontologically.
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2nd Gondwana Symposium, 157-167
Inclination of the earth's magnetic field at a station and the conventional statement of its relationship to geographic latitude are examined critically. Great discordance exists between observed latitude and latitude computed from magnetic inclination. A new method is developed from inclination as an expression of the vertical components of force in the earth's magnetic field at equilibrium; it gives greatly improved precision. The vertical intensity of the earth's magnetic field, now, indicates that the inclination can be accounted for satisfactorily by a bar 250 miles in diameter and 2 945 miles long. Its axis is 305 miles from the geographic axis and almost halfway to an axis joining the magnetic poles; it is displaced towards 135øE longitude. The eccentricity of this dipole is responsible for the apparent discordant pole positions determined at different modern stations by use of the conventional equation. A new equation for an eccentric dipole is applied to paleomagnetic measurements for Permian Period rocks and shows all stations referable to an eccentric magnetic axis which intersects the earth's surface at N41.3ø,136.1øE and S24.8ø, 79.1øW. The N pole is 2 250 miles inwards along this axis, the S pole is 1 875 miles inward, and they are 3 315 miles apart. Measurements for the Triassic Period show all stations referable to an eccentric magnetic axis which intersects the earth's surface at N 68ø, 92øE and S 64ø, 50øW. The N pole is 700 miles inwards along this axis, the S pole is l 320 miles inwards, and they are 5 730 miles apart. The results show that the existing paleomagnetic measurements indicate no definitive displacement of stations relative to these reference axes since their respective periods.
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2nd Gondwana Symposium, 511-529
A preliminary palynological study of the Permian sediments of the northern Perth Basin, Western Australia, has been completed, and systematic descriptions and stratigraphic ranges have been prepared (Balme and Segroves, 1966; Segroves, 1967, 1969, in press). Samples studied during the investigation came from localities scattered over an area of about 4 000 sq. miles in the northern portion of the Perth Basin. In the Perth Basin outcrops of Permian sediments are rare and, with the exception of certain coals, samples collected from outcrop are unsuitable for palynological examination because of prolonged weathering. Most of the 300 samples studied were taken from 59 bores distributed sporadically throughout the area. These were drilled by the Public Works Department of Western Australia, Geological Survey of Western Australia, West Australian Petroleum Pty. Ltd., and the University of Western Australia. The Permian sediments contain a well-preserved microflora. Lithological monotony and extensive normal faulting in the basin make the subsurface stratigraphy difficult to interpret and plant rnicrofossils appear to be the most generally applicable palaeontological means of elucidating this stratigraphic complexity. In his discussion of pre-Tertiary microfloras from throughout Australia, Balme (1964) recognized three Permian assemblages. His "Nuskoisporites Assemblage" is of Sakmarian and lower Artinskian age. The remainder of the Lower Permian is represented by the "Vittatina Assemblage" although this was not seen outside Western Australia. His Upper Permian "Dulhuntyispora Assemblage", like the "Nuskoisporites Assemblage", was recognized in sediments from several basins in both eastern and western Australia. After the publication of the above study, considerable drilling in the Perth Basin itself made available enough well-documented material to merit a study of the Permian sediments there. The work indicated that the general sub-division of the Permian made earlier by Balme could, for the Perth Basin, be somewhat refined, and that five biostratigraphic units are recognizable within the Permian succession, using plant microfossil assemblages as the basis for sub-division. The gross quantitative variations of the general categories of microfossils present are indicated in Text-Figure 2. The quantitative variations of several stratigraphically useful species are shown in Text-Figure 3. For all of the species encountered in the sediments studied, the known stratigraphic ranges for the Perth Basin are given. The general composition of the five assemblages is given below.
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2nd Gondwana Symposium, 15-22
Over the past 15 years, twelve countries have participated in the investigation of the geology of Antarctica by undertaking broad programmes of mapping; both the field programmes and the results have been co-ordinated by the Scientific Committee on Antarctic Research. The use of long-range aircraft has allowed access to the remotest regions of the continent and helicopters have successfully supported detailed field mapping programmes in relatively inaccessible areas. Now it is possible to make a reasonable overall assessment of the stratigraphy and structure of Antarctica. But it must still be recognised that there are vast regions of the continent that are ice-covered, and here the structural interpretation must depend on geophysical evidence. There are also problems of stratigraphical nomenclature and correlation that have naturally arisen from the exploration of new areas. Antarctica can be divided into two distinctive geological provinces, the Gondwanan and Andean, which almost coincide with the physiographical provinces, but the precise structural relationship between these provinces remains a matter for further field investigation. The continental shield of east Antarctica is formed by a basement composed of ancient complexly metamorphosed rocks (including several phases of gneisses and charnockites), migmatites and igneous intrusions which have been affected by at least two major and two minor orogenies; sub-horizontal sediments of the Beacon Group cap the basement complex, especially along the 5 000 m high Transantarctic Mountains which fringe the poleward margin of this province. Cenozoic volcanism, perhaps associated with late tectonism, is of isolated occurrence. In strong contrast is the Andean Province of the Antarctic Peninsula- and west Antarctica, where an ancient basement is absent. This region is the trace of the Carboniferous marginal geosynclinal belt, which has been subsequently modified by at least six intrusive phases, three important volcanic episodes, and two major orogenies (Triassic and late Cretaceous-early Tertiary). Folding and late Tertiary block-faulting, with associated volcanism, have been responsible for the present form of the Antarctic Peninsula and much of west Antarctica. Included in west Antarctica is a region (the Ellsworth Mountains) which is stratigraphically related to east Antarctica, but which has an anomalous structure. It is conceivable that this is perhaps one of several fragments that were sheared from the continental shield during the formation of the Antarctandes. One of the main features of the Transantarctic Mountains region is the extensive sub-horizontal pre-Devonian Kukri Peneplain, on which rest the Devonian-early Jurassic Beacon Group sediments. These sediments had a varied origin, ranging from marine to glacial, lacustrine, fluviatile and terrestrial, and have their thickest development in the central Transantarctic Mountains. The lowermost beds contain both Devonian fish and plant fragments, but the Permo-Carboniferous and the succeeding Permian fluviatile beds possess an abundant glossopterid flora, woods and coal measures. Characteristic of the Triassic cyclic sequences are plants, and in several localities reptile bones have recently been discovered in these sediments. The Beacon Group is capped by agglomerates, tuffs and lavas of the Ferrar Group, and with these are allied the extensive dolerite sheets which intrude the Beacon Group. Important problems are the detailed correlation of this thick and varied sequence over a great distance, and whether there is sufficient evidence for applying broader stratigraphical status to the "Beacon Group". The stratigraphical, structural and tectonic problems of Antarctica are reviewed in the light of recent field investigations.
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2nd Gondwana Symposium, 1-13
The two years since the 1st Gondwana Symposium produced a tremendous wealth of information. Almost two hundred papers appeared in this period covering the Geological Sciences from Palynology to Paleomagnetism. About 80 papers were on Gondwana Palaeontology, and the rest are mostly stratigraphical. Radiometric age determinations of rocks from Precambrian to Pliocene are undoubtedly the most interesting information relating to Continental Drift given during this period. Also Paleomagnetic studies of Trias and younger rocks contributed to this problem and to the age of separation of South America and Africa. The history and origin of the South Atlantic Ocean was presented on various evidence. Some papers published during 1967 have been included as they were not known at the time of the Mar del Plata Symposium, and some papers in preparation or in press have been considered as they are of great interest to geologists from other parts of the world. The authors wish to thank Dr. Cordani (University of São Paulo), Ing. Valencio (University of Buenos Aires), Dr. Caminos (Dirección Nacional de Minería, Buenos Aires) and Dr. Millan (Universidade Federal do Rio de Janeiro) for their interesting information. Thanks are also due to Mr. Manceñido for his help in preparing this review.
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2nd Gondwana Symposium, 23-28
Much information has been gathered on the Carboniferous, Permian, Triassic and Jurassic. A highlight of the Carboniferous has been the detailed investigation of the Bonaparte Gulf Basin of Western Australia. Reef formation has been shown to extend from the Devonian into the Lower Carboniferous. Detailed studies have been made of the conodonts, brachiopods, foraminifers and spores. Widespread instability and mobility during the Permian are confirmed, with protracted and complex igneous activity in eastern Australia. Radiometric data place the Carboniferous-Permian boundary at about 280 million years and the Permian-Triassic boundary at 230-235 million years. The main period of glaciation in Australia is not younger than early Lower Permian and may have begun in the late Upper Carboniferous. Interpretation of ice activity in the Upper Carboniferous is complicated by the evidence of mountain glaciation-glaciation at sea level has not so far been proven. In the eastern Australian terrestrial deposits the Permian- Triassic boundary may be higher than previously supposed. Elaboration of the faunal succession in eastern Australia and its applications to time, climate and palaeogeographical relationships has continued. The evidence from the sparse marine sedimentation in the Lower Triassic confirms the peculiarity of the late Permian and early Triassic. In eastern Australia some igneous activity previously ascribed to the Tertiary can now be shown to belong with the Triassic and Jurassic.
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2nd Gondwana Symposium, 249-256
The Beacon Supergroup in the Transantarctic Mountains is largely a flat-lying non-marine sequence from Devonian or older to Jurassic in age. It rests unconformably on a Precambrian and Lower Paleozoic basement, and is intruded and overlain by Jurassic basaltic rocks. The Taylor Group, largely a quartzose sandstone succession, is exposed between the Mawson and Beardmore Glaciers, and reaches a thickness of 1 100 m. The only datable fossils are lycopod stems and fish remains of Devonian age from the uppermost strata, but there is a thin marine sequence of Lower Devonian age in the Ohio Range. The bulk of the Taylor Group was derived from a shield area to the west. Thick folded sequences of similar age and lithology crop out in the Pensacola and Ellsworth Mountains. The Victoria Group is a heterogeneous sequence of glacial beds, carbonaceous and non-carbonaceous alluvial plain sediments, and volcaniclastic strata from Permian to Jurassic in age. It increases in thickness from a few metres in northern Victoria Land to 2 400 m in the Beardmore Glacier area. Permian or Triassic plant fossils are found at most places, and a Lower Triassic assemblage of amphibian and reptile remains has recently been found in the Beardmore Glacier area. The Permian transport direction was, except for southern Victoria Land, to the south-east along the Transantarctic Mountains, but the Triassic alluvial plain sloped to the north-west. Intermediate-acid volcanism in the upper part of the Permian and the Triassic section culminated in the explosive eruption and redeposition of coarse volcaniclastic beds at the top of the group. A stratigraphic correlation chart of Beacon formations in the Transantarctic Mountains is presented.
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2nd Gondwana Symposium, 213-223
The Talchir sedimentation was ushered in by widespread deposition of glacial sediments in different Gondwana basins of India. In the initial phase, the basins were restricted to several isolated erosional depressions on the Precambrian platform. Despite the restricted domain of sedimentation, the Talchirs are characterized by a varied assemblage of lithofacies, such as tillites, fluvio-glacial outwash sandstones and conglomerates, glaciolacustrine shales, rhythmites and turbidites. Present find of widespread turbidites in association with these sediments is an important addition to the existing knowledge of the sedimentary framework of such periglacial deposits. It is postulated that the unstable pile of sediments, built up by the meltwater streams near the periglacial lake margins, was susceptible to frequent slumping which resulted in the generation of spasmodic turbidity currents in the lakes where the Talchirs were deposited. The relationship of the different lithofacies of the Talchirs in a vertical sequence constitutes a distinctive pattern, which through recurrence defines two major cycles in some of the basins as in the Damodar valley. Such cyclic arrangement is well developed in the basins located away from the main centres of glaciation, whereas, in those peripheral to the main gathering grounds of ice, the evidences of cyclicity are less well imprinted. It has been concluded that the cyclic pattern of the Talchir sedimentation is a function of the advancing and retreating ice fronts.
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2nd Gondwana Symposium, 273-291
The Arckaringa Basin, situated in northern South Australia, is an intracratonic Permian basin, composed of deep marginal grabens or half grabens and a central area of shallow basement, the latter covered by only a thin sediment blanket. The sedimentary sequence comprises, in ascending order, diamictites and cyclically graded graywacke (Unit 2), a dark coloured shale sequence (Unit 1) and dark grey micaceous siltstones, sandstones and coal-seams (Mt. Toondina Beds). Along the eastern margin of the Basin, coarse clastics with clayey, sandy and dolomitic matrix, containing striated, fluted and soled cobbles and pebbles, are exposed. The thickness of the sediments ranges from about 100 feet (30 m) in outcrop, 800 to 1 200 feet (240 to 365 m) over the area of shallow basement to more than 5 000 feet (1 524 m) in the centre of some of the grabens. The Arckaringa Basin was established by downfaulting of the graben structures in late Carboniferous-early Permian times, but shortlived movements along the same trends were already experienced in the Devonian. Upfaulting of adjacent basement blocks created uplands on which plateau glaciers formed during the early Permian. Moraines and eskers were deposited along the basin margin whence glacial debris was transported into the distal troughs by mudflows and turbidity currents. Available evidence suggests that the Permian glaciation was concluded in mid-Sakmarian time and that the cyclically graded graywackes are largely the product of post-glacial turbidity currents, fed by high intake rates of detrital material which was maintained by continuous movements along the marginal faults. Tectonic stability in the late Sakmarian produced a low-energy marine environment during which the dark shales of Unit 1 were deposited. Temporary evaporitic conditions are documented locally and such changing environments are thought to be responsible for the low diversity of the foraminiferal fauna. Regression of the sea in early Artinskian was brought
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2nd Gondwana Symposium, 265-271
Recent discoveries of fossil tetrapods in Antarctica have all been in the lower part of the Fremouw Formation in the Transantarctic Mountains near Beardmore Glacier. The Fremouw Formation is a Triassic floodplain deposit within the widespread sequence of mainly nonmarine Beacon rocks, which range in age from Devonian (?) to Triassic-Jurassic. Coarse channel sandstones near the base of the Fremouw Formation contain bones that occur as disarticulated fragments associated with quartz pebbles and mudstone pebbles and cobbles. Discovery sites now include Graphite Peak, Mount Sirius, an outcrop north-east of Mount Marshall, and Coalsack Bluff, the last-named locality being the most productive to date. The fossil tetrapods confirm the Triassic age of the Fremouw Formation, which was previously assigned that age on the basis of stratigraphic position and the occurrence of the fossil plant Dicroidium odontopteroides in its upper part.
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2nd Gondwana Symposium, 531-536
All the palynological information regarding Gondwana rocks in India has been synthesized, building up the vertical succession of principle spore groups through the Gondwana Era. It has been possible to distinguish 8 miofloras, three being restricted to Permian, two each to Triassic and Jurassic together with Lower Cretaceous, and the youngest as the basal, non-angiospermous precursor of the Angiosperm miofloras of Middle Cretaceous and younger ages. The five maxima of trilete spores, separating the miofloras, have been shown to be directly succeeding the miofloral changes. Three of these changes tend to lie along the boundaries between Permian, Triassic, Liassic and Oolitic. It has been concluded that palynologically the Gondwana Era is divisible into four Divisions. However, the youngest Division, presumably commencing from Aptian and floristically representing the basal part of the angiospermous flora of the later ages, is suggested to be excluded from the limits of the Gondwana Era.
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2nd Gondwana Symposium, 421-431
The Late Triassic-Early Jurassic Prebble Formation consists of mudflow debris and pyroclastic rocks which represent the culmination of an episode of volcanism recorded in the underlying Triassic sedimentary formations by volcanic detritus and tuffs. The Mawson Tillite is the only known unit in a similar stratigraphic position with similar lithology. The Prebble Formation is overlain by the Kirkpatrick Basalt, comprising at least 525 m of Jurassic tholeiitic flood basalts. Similar lavas crop out in isolated areas between the Queen Alexandra Range and northern Victoria Land, where there is an extensive field of flood basalts about 1 370 m thick. Although no lithologic equivalent of the Prebble Formation has been found either in southern Africa or the Parana Basin, the Gondwana Triassic succession of western Argentina and several Triassic basins in eastern Australia contain volcanic material. Basalts in the same stratigraphic position as the Kirkpatrick Basalt crop out in southern Africa and India; however, in South America, the basalts of the Serra Geral Formation are significantly younger. The Kirkpatrick Basalt, the correlative Ferrar Dolerite of Antarctica, and the Tasmanian Dolerites have geochemical characteristics which have established a magmatic province and provide a major contrast with the other Gondwana Mesozoic tholeiites.
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2nd Gondwana Symposium, 303-308
The sequence of continental Gondwana formations of the Pranhita-Godavari Valley, Central India, and of their vertebrate faunas is discussed in the light of recent work in stratigraphy and palaeontology. It is now seen that the sequence in this outcrop is unbroken for the most part, and it has already yielded four distinct vertebrate faunas. In these respects, it holds a unique position among the Gondwana outcrops of India and may well prove to be of importance in the correlation of Mesozoic continental sequences of the world.
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2nd Gondwana Symposium, 293-301
The Panchet sediments are marked by an alternate sequence of arkosic sandstones and red and green shales and are found to occur in widely separated Peninsular Gondwana basins in India. These sediments are stable residual products of a granitic terrain and are represented by a single sand-coarse silt population which has been further differentiated to give rise to two distinct lithic units, viz., a sandy fraction and a red argillaceous fraction. Repetition in regular order of these lithic units along with the associated structural elements suggests a cyclic pattern in sedimentary organisation. Analysis of the textural parameters and associated sedimentary structures of the Panchets indicates an alluvial environment where the coarse clastics were deposited as lateral accretion within the channel as point bars. The finer clastics accumulated in the inter-channel flood plains as vertical accretion deposits. Petrographic, chemical and X-ray analyses of the red beds of the Panchets show that the red colour of these sediments is due to red pigmentary hematite present as thin coatings on the clastics and also probably as finely powdered detritus present throughout the sediment. Petrographic study further reveals that this pigmentary hematite has been formed in situ due to diagenetic transformation of the original hydrated ferric oxide.
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2nd Gondwana Symposium, 557-560
The present study has been made to analyse the floral correlation of Gangamopteris prevailing during the Gondwana period between the two Gondwana provinces of India and Australia. The author has examined all the available figures of different species of Glossopteris and Gangamopteris of the two countries, and the species under the latter genus are tabulated chronologically in this paper. In a previous paper (Sarkar, 1969) the author approached the examination of the homogeneity of a few individual species of Glossopteris, such as G. indica, G. angustifolia, and G. browniana which occur widely throughout the Gondwanaland. In another paper (Sarkar, 1970) read before the International Gondwana Symposium held at Aligarh in India, the author presented the correlation of the Glossopteris flora of India and Australia. Thus a comparative study of the Indo-Australian Gangamopteris is essential from the point of view of correlation. The present study is based upon figures only as given by various authors and no cuticular study of the genus has been taken into consideration, as such studies have been done infrequently and do not permit a fair assessment of all the species distributed intercontinentally. Descriptions given by authors have been consulted only when it became necessary, as also the Indian type specimens.
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2nd Gondwana Symposium, 543-549
Microfloras of Aalenian, Bajocian, Lower Callovian, and Oxfordian age are reported from various localities of central western Argentina (Neuquén Province) and one locality of central Extraandean Patagonia (Chubut Province). The Aalenian microflora from Chacai-Có (Neuquén) was deposited in marine Posidonomya cf. alpina-bearing black shales and is mainly composed of Classopollis, Araucariacites australis and Inaperturopollenites turbatus. It contains also bisaccate grains, a few spores and microplankton (Tasmanites sp. and hystrichospheres). The Bajocian microflora from Bajo de los Baguales contains nearly 60 species of plant microfossils belonging to five microfloral associations, which mainly consist of conifer pollen grains of Classopollis-Araucariacites- and Vitreisporites-type. The frequency of trilete spores ranges from 15 to 25% in the five associations mentioned. Callovian microfloras are known from Picún Leufú, Neuquén Province (Las Lajas Formation, Lower Callovian), and Charahuilla, Neuquén Province (Lower Callovian). They can be compared with the Australian "Dampieri - Assemblage". The sedimentary environment of the Callovian microfloras mentioned is continental. They do not contain any microplankton. The Charahuilla-Association was extracted from a coal and is composed of nearly 70% of trilete and monolete spores (mainly Deltoidospora, Verrucosisporites, Osmundacidites, Gleicheniidites, Concavisporites, Peromonolites) and 30% of pollen grains (Callialasporites dampieri, Araucariacites australis, Vitreisporites, Podocarpidites, Microcachryidites), numerous species of monocolpate grains (Cycadopites, Monosulcites, etc.) and, less frequently, monoporate grains (Classopollis, Gliscopollis). The association also contains the first finds of Ephedratae-pollen grains (Ephedripites) known from Jurassic beds in the world register. The Oxfordian microflora from central Patagonia (Cañadón Asfalto Formation) is characterized by the earliest register of Callialasporites trilobatus (Balme) Dev, which is absent in all earlier microfloras of the Jurassic in Argentina. Classopollis (more than 65%) is the main component. The microfloristic evidence complements and corroborates the paleoclimatic information obtained by macro-paleobotanical, paleozoological and lithological indicators from the Jurassic of Argentina. In Neuquen/Mendoza and t Patagonia this period is characterized by frequent changes g of moist and dry conditions in time and space. As a general rule, the Lower Jurassic was warm-temperate and moist; the Middle Jurassic was warm and arid with local moist conditions. During the Upper Jurassic extremely arid and very warm conditions prevailed. Relations of climate and paleogeography (transgressions and regressions) are outlined.
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2nd Gondwana Symposium, 605-612
The bivalve and gastropod faunas reviewed from Paraná Basin (Itararé Subgroup), Brazil, and Argentina (Bonete and Santa Elena formations) include genera considered characteristic of the Gondwana (cold) province during the upper Paleozoic together with more cosmopolitan genera. The fauna from the Itararé Subgroup show affinities to other upper Paleozoic faunas of South America (Argentina and Peru), as well as to Permian faunas of Australia. A Gondwanic character is clearly exhibited by the faunas of Argentina that show closer relationship with the Australian Permian faunas.
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2nd Gondwana Symposium, 665-682
South America has provided abundant Triassic reptiles which give important additional data that enable us to understand better the evolutionary paths followed by the Early Triassic reptilian assemblages in producing the completely distinct reptile fauna of the Late Triassic. The evolutionary implications of these South American reptiles are precisely the reason for their importance and the factor which most attracts us to work on them. Obviously, they are also involved with paleogeographical, chronological and paleoecological problems, but up to the present only a few attempts have been made to study these. The systematic study of the South American Triassic reptiles was initiated vigorously by the late Prof. F. von Huene, who made a fruitful expedition to Brazil in 1928. After some previous papers he published a worthy monograph on the South Brazilian reptiles from the Santa Maria beds (1935-42). The first discoveries in Argentina were made by the late Dr. J. Frenguelli in the Ischigualasto and Cacheuta basins, published by Cabrera (1943, 1944); and from 1948 in by the late Prof. C. Rusconi, with brilliant discoveries of labyrinthodonts and a thecodont from the Cacheuta basin, published in several papers. The Museum of Comparative Zoology, Harvard University, worked intensively in Brazil and Argentina in 1936, 1958 and 1964, and the American Museum worked in Brazil in 1959. At the same time, good collections were made in Brazil by the Brazilian Divisão de Geologia e Mineralogia, and the Museu Nacional. The various collections of Triassic tetrapods from Brazil have been made in the same area and beds as the Huene collection, this latter kept in Tübingen, Germany. In Argentina, after the Romer expedition in 1958, every year expeditions have been sent by the Instituto M. Lillo, Universidad Nacional de Tucumán, for systematic exploration of several Triassic localities, which resulted in important and numerous discoveries. The biggest Triassic collections from Argentina are at the Instituto M. Lillo, Argentina, and at the Museum of Comparative Zoology, USA. They very likely represent the best continental Middle and Upper Triassic tetrapods collections known to date. In addition, since 1960 the Universidad de La Plata (Argentina) has made three expeditions to a South Patagonian Triassic locality containing dinosaurs.
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2nd Gondwana Symposium, 659-664
Late Paleozoic and early Mesozoic amphibians and reptiles are widely distributed throughout the continents that once formed Gondwanaland. Land-living tetrapods of Permian and Triassic age are found in great abundance in the Karroo rocks of South Africa, numerous Triassic tetrapods have been discovered within recent years in South America, and the fossil record extends with varying degrees of completeness to Australia and to peninsular India. Indeed, Gondwana tetrapods are found beyond the limits of Gondwanaland-in the upper Permian sediments of Russia, and in the Lower Triassic beds of western China. But until quite recently there was no record of such fossils in the Paleozoic and Mesozoic rocks of Antarctica. This was a major deficiency in the evidence that had been accumulating through the years for a continent of Gondwanaland and for Continental Drift. Yet, paleontologically speaking, Antarctica was and is the key to Gondwanaland and to Continental Drift. The distributions of Gondwana-type fossils, especially land-living tetrapods. on the southern continents other than Antarctica, can be explained (albeit in a tortured fashion) without resort to a Gondwanaland and to Drift, because intercontinental connections are (or have been in the not too distant past) of such nature that land-living animals might have spread along these familiar paths from one region to another across the face of the globe. But Antarctica is an isolated continent, and it has been isolated for a long time. If the fossils of land-living vertebrates were to be found in Antarctica the existence of a former Gondwanaland and of subsequent Continental Drift would pass from the realm of probability into that of almost complete certainty, a statement that is made with all due respect to the geophysical and geomagnetic evidence that has accumulated within the past decade, and particularly to the exciting and convincing evidence of sea-floor spreading. For in the final analysis the theory of Gondwanaland and of Continental Drift has to accord with the realities of the geological evidence, not the least of which is the distribution of fossils. t So it was that until recently the absence of any evidence as to Gondwana tetrapods in Antarctica formed a hiatus-perhaps small but nonetheless most crucial - in the accumulation of facts that with ever-increasing force pointed to the existence of a former Gondwanaland, and the subsequent separation of its constituent parts by Continental Drift. In 1967, the validity of this hiatus was challenged by the discovery of a fragmentary amphibian jaw in the Triassic rocks of the Beacon sequence in the Transantarctic Mountains. The specimen was found by Peter Barrett in the Fremouw Formation, at Graphite Peak, near the Beardmore Glacier. Its discovery caused considerable excitement among geologists and paleontologists, for the implications of this very small and broken specimen were large. If one imperfect tetrapod fossil could be found in Antarctica, certainly more should be found. Therefore a search for Triassic tetrapods in the Fremouw Formation was organized, and was carried on with success during the field season of 1969-1970, so that a considerable assemblage of tetrapod bones was collected from the Fremouw Formation at Coalsack Bluff, across the Beardmore Glacier from Barrett's discovery at Graphite Peak. This collection of fossils has proven to be of African relationships, and it has amply justified the prediction made by Lester C. King in 1965: "Amid the mountains at the head of Beardmore Glacier therefore is surely the place for Mr. James Kitching to search for Karroo Therapsida!" (King, 1965, p. 10) Perhaps the most exciting aspect of the discovery of fossils at Coalsack Bluff is the presence in the collection of numerous bones of the reptilian therapsid genus, Lystrosaurus. There are other therapsids and other reptiles as well in the collection, and in addition the remains of labyrinthodont amphibians, but Lystrosaurus is the key fossil that makes the Coalsack Bluff fossils especially significant. Lystrosaurus is the guide fossil of the Lower Triassic Lystrosaurus zone in the Middle Beaufort beds of South Africa, and it is characteristic of the Lower Triassic of peninsular India and of western China as well.
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2nd Gondwana Symposium, 613-614
Permian invertebrate faunas are exceptionally differentiated into many biogeographic provinces reflecting, no doubt, climatic and geographic contrasts of Permian times. Associated with and interstratified with the Glossopteris land flora, marine bivalves of the families Megadesmidae and Eurydesmidae are highly characteristic of Gondwanaland. More local, strictly endemic, taxa also are numerous in the Permian rocks. Outstanding among these is a bivalve molluscan fauna of the molluscan fauna of the Estrada Nova Formation in the Paraná Basin of southern Brazil, Uruguay, Paraguay, and Argentina over an area of about one and a half million square kilometres. This fauna is well preserved, abundant, diverse, and widely distributed in the Paraná Basin. It is, however, unknown in rocks of equivalent age in Africa and elsewhere. From our studies, we conclude that there are thirteen well-characterized pelecypod genera in the Estrada Nova fauna of which twelve are unknown outside the Paraná Basin. Twenty-five species are recognized, all of them endemic. These fossils have been made well known through the work of Josué Camargo Mendes and others, but the ecological significance has remained obscure and even the family affinities of the species have been uncertain. Mendes thought that the Estrada Nova fauna might have developed in freshwater lakes and streams of the Paraná Basin Mendes, 1967). We think, however, that this hypothesis does not explain the extreme endemism of the Estrada Nova fossils. Families of freshwater molluscs generally are much more widely distributed than the Estrada Nova fossils use because their facilities generally are adequate for crossing stream divides. Throughout geologic time, families of marine molluscs have tended to be even more widely distributed than freshwater taxa. Consequently, if the Estrada Nova molluscs lived in fresh, normal marine, or even estuarine waters, they should appear in rocks of upper Permian age in Africa and elsewhere in Gondwanaland, but thus far they do not. Thus, the narrowly restricted regional distribution of the Estrada Nova fauna constitutes a problem that clearly calls for a special solution. Throughout the whole geologic column there is only one well-documented, closely parallel situation. That is provided by the late Cenozoic evolution of the Caspian region. The Caspian Sea has an average salinity of about 15 parts per thousand and contains a molluscan fauna which, until foreign species were introduced by man, was dominated by brackish-water endemic genera and species. Judging from the fossil records of these taxa they developed essentially in situ during the Pliocene in an arm of the Mediterranean, the Pontian Sea (Ebersin, 1965). The Pliocene faunas of the Pontian sediments are dominated by diverse bivalves of a single family, the Cardiidae. They are distributed among some 36 genera and five subfamilies of cardiids, apparently derived from a few species of the common Mediterranean cockle, Cerastoderma (Cardium). A significant number of the brackish-water forms are still living in the Caspian and Azov Seas (Zenkevitch, 1963), so their environmental tolerances are well known.
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2nd Gondwana Symposium, 599-603
Recent work on Permian faunas of eastern Australia has revealed undoubted resemblances with Western Australian faunas. Many genera are found in eastern Australia that were previously considered to be indigenous to Western Australia only. This has significant implications, as for many years the Permian faunas of Australia have been divided into the eastern and Western Australian provinces.
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2nd Gondwana Symposium, 575-584
Re-examination of the literature and examination of a number of recent collections have led to redetermination of a number of species present in the Lower Gondwana flora of the Paraná Basin. This flora is a normal Lower Gondwana flora predominantly of local affinities, with few species from other Gondwana areas. The flora of the Tubarão Group is dominated by Glossopteris and Gangamopteris. The flora of the Passa Dois Group is dominated by Lycopodiopsis. The age lies within the range of Upper Carboniferous to Upper Permian.
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2nd Gondwana Symposium, 561-570
The present paper deals with a review of some species of Glossopteris viz.,G. acuta Dun, G. clarkei Feistm., G. elegans Feistm., G. parallela Feistm., G. rectinervis Dun, G. spathulatocordata Feistm., G. taeniopteroides Feistm. and G. wilkinsonii Feistm. Lectotype has been selected for each of these above-mentioned species by studying the originally described specimens of the individual species. The correct number of the neotype selected for G. cordata Dana by Rigby has been communicated in the present paper. Emphasis has been laid on the selection of holotypes or lectotype specimens of Glossopteris species on the basis of morphographic characteristics of each of the individual species for successfully implementing the plant fossil evidences in Gondwana stratigraphy. The situation of doubtful identification of some of the fertile leaves of Glossopteris described from South Africa and India has been discussed in the light of recent revisional study of the original specimens of the respective Glossopteris species.
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2nd Gondwana Symposium, 585-588
The fossil record supplies chronological evidence for the stages in the evolution of the leaves of the Glossopteridae. With minor modifications all of the stages recognised can still be found in living Angiosperms. It is shown that the leaves of Angiospermae and Glossopteridae share a group of venation characters which is called the Glossopterid syndrome. Examples of Angiosperms with leaf characters resembling those of Gangamopteris, Glossopteris and Taeniopteris are discussed and the manner of their transformation into modern leaf types is indicated. Additional evidence for a relationship between Angiospermae and Glossopteridae is provided by bracts, sepals and petals and by the reproductive organs.
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2nd Gondwana Symposium, 537-540
The coal-beds of the Sakoa sedimentary Group, lower Karroo System, located in the Sakoa-Sakamena basin, south-west Madagascar, are being studied with a palynostratigraphical aim. 317 samples mostly of coal obtained from the cores of 11 bore-holes and gathered into 110 representative samples have been analysed both qualitatively and quantitatively. 64 miospore genera have been distinguished out of which 23 are Sporites and 41 Pollenites. On the other hand, the present author opines that the coal-beds according to the palynological analysis belong to the lower Barakar stage of the Damuda Series in India. The Artinskian of the lower Permian would be the equivalent age of these beds in the Northern hemisphere. The Malagasy coal-beds are then compared to Gondwanic formations which are believed to be of the same age according to the palynological data in the following countries: India, South Africa, Tanzania, Congo-Kinshasa, Australia and the Antarctic continent. These beds very probably are also referable to other Gondwanic formations occurring both in Africa (Mozambique, Rhodesia, Zambia) and in South America (Brazil, Uruguay, Argentina and the Falkland Islands).
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2nd Gondwana Symposium, 371-380
The N'Khom Series and the Agoula Series of Gabon (Equatorial Africa) are, according to their microfloral content, mainly of Permian age. They are equivalent. in reduced thickness, to the Lower Karroo. In Gabon, the Karroo System commences with basal glacial deposits (N'Khom Series) followed by black shales (Bekang Member of Agoula Series) deposited in a reducing environment. The latter are comparable with the black shales of Walikale and Lukuga Series of the Congo Basin. Sandstones and stromatolitic dolomites (Koumiki Member of Agoula Series) overlie the Bekang Member and are interpreted as having been deposited at the edge of a lagoon or salt lake. The top of the Agoula Series is represented by vividly coloured shales and fine-grained sandstones (Assango Member).
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