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The Protomoesian microcontinent of the Balkan Peninsula — a peri-Gondwanaland piece
PALAEONTOLOGY The trace fossil Cruziana semiplicata and the trilobite that made it Fortey R.A. & Seilacher A., Lethuia, 1997,30/2 (105-l 12).A set of criteria is suggested for associating a trace fossil with a plausible fossil: (1) close association in the field; (2) concurrent stratigraphic range; (3) a minimal choice of candidates available that could have made the trace; (4) consistent size range between trace fossil population and that of the maker; and (5) consistent biogeographic ranges for both. In the Upper Cambrian Andam Formation of Oman, there is a rare, direct association between trilobite body fossils and the trace fossil Cruziana in the same rock succession. Anassociation of the trilobite Maladioidella cf. colcheni with the trace fossil Cruziana semiplicata is supported by the criteria listed. Algues calcaires marines du Paleozoique Superieur (Equateur, Bolivie) (Upper Paleozoic marine calcareous algae (Ecuador, Bolivia)) Mamet B., Annales - Societe Geologique de Belgique, 1996, 117/l (155_167).Diverse flora of cyanophytes, palaeosiphonocladales, udoteaceans, phylloid algae, dasycladales, calcispheres, cuneiphycids, stacheiins and microproblematics are illustrated from a number of Carboniferous and Permian basins of South America. This Gondwana flora had been previously completely overlooked. It indicates temperate conditions at the very heart of a subcontinent presumed to be glaciated in the Carboniferous. La flore du Trias superieur vietnamien. Implications paleogeographiques (The Upper Vietnamese Triassic flora: palaeogeographical significance) De Franceschi D. & Vozenin-Serra C., Comptes Rendus Academic des Sciences, Serie II: Sciences de la Terre et des Plunetes, 1997, 324/4 (333-340).The Vietnamese Triassic flora belongs clearly to the coastal floristic assemblage of the SouthWest Pacific. By its littoral features, the boundary of this flora distribution might coincide with the tectonically significant suture zone. Its similarity with the Ussuriland, Japanese and Korean floras raises the question of the real position of these areas in the Triassic. Affinities of its lower plant-fossil assemblage with the Krusin flora (Borneo) maybe explained by Hutchinson’s interpretation (in Ridd, 1980) of a ‘West Malaysia-Western Borneo’ island arc broken up probably during the Carnian. The existence of Gondwanian elements in this flora is discussed. There is an abridged English version.
STRUCTURAL GEOLOGY AND TECTONICS The Protomoesian microcontinent ofthe Balkan Peninsula -a peri-Gondwanaland piece Haydoutov I. & Yanev S., Tectonophysics, 1997, 27212-4 (3033 13)Based on differences in their pre-Palaeozoic and Palaeozoic development, the Protomoesian microcontinent is divided into two terranes: the Balkan and the Moesian. A PrecambrianCambrian ophiolite-island-arc assemblage, unconformably overlain by a Palaeozoic sequence, forms the first terrane. The pre-Palaeozoic basement of the Moesian terrane consists of Proterozoic-Vendian metamorphics of continental origin. The differences in the development of the Palaeozoic rocks are also significant reason for dividing the Balkan and the Moesian terrane. Numerous features of the Palaeozoic sediments (palaeoclimatologic, palaeobiogeographic, palaeomagnetic) from both terranes, and the Pan-African affiliations of the ophioliteisland-arc assemblage, identify the Protomoesian microcontinent as a peri-Gondwanaland piece.
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Geodynamic models and palaeomagnetic constraints on the evolution of the North West Shelf Klootwijk C., AGSO Research Newsletter, 1997,261- (22-24)After the Middle Cambrian completion of the Rodinia-to-Gondwanaland transformation, northeastern Gondwanaland (ie, ‘Greater India’ and ‘Greater Australia’) was fragmented, and the fragments were widely dispersed. An integral part of northeastern Gondwanaland, Australia’s North West Shelf region has recorded the effects of the wider tiagmentation processes. Detailed knowledge of these processes would help us to unravel the evolution of this major petroleum province. To this end, AGSO’s Marine and Petroleum Division has undertaken a review of geodynamic models and palaeomagnetic constraints relevant to the Phanerozoic evolution of Gondwanaland’s northeastern margin. The main findings are summarised in this report. Neoproterozoic (-600 Ma) aggregation of western Gondwana: a tentative scenario Trompette R., Precambrian Research, 1997, 82/l-2 (IOI112).Gondwana resulted from accretion of fragments of the Rodinia supercontinent. However, precise times and circumstances of individual accretions are still disputed. Aggregation of Western Gondwana occurred at ca 600 Ma or somewhat earlier, with the orogeny closing the old, long-lived Pan-African-Brasiliano tectonic cycle (1000-900 to 600 Ma). It resulted mainly from a submeridional collision between the huge West Africa-Amazon-Rio de la Plata megacontinent, recently broken off the eastern border of Laurentia, and two small continents: the joined Congo-Sao Francisco-Northeast Brazil-Central West Africa continent and the Kalahari continent. Basins related to the second young, and short-lived tectonic cycle opened at ca 600 Ma, or slightly later, and were deformed and metamorphosed around the Early-Middle Cambrian boundary at ca 520 Ma. Most of them were ensialic and did not succeed in breaking up the newly aggregated Neoproterozoic West Gondwana supercontinent. Their rifting was contemporaneous with that of the large Palaeozoic basins such as the Appalachians. Relationship ofAvalonian and Cadomian terranes to Grenville and Pan-African events Mallard L.D. &Rogers J.J.W., Journal of Geodynamics, 1997,23/34 (197-22l).Suturing of the supercontinent Rodinia in the Grenville event (-1000 Ma) was followed by rifting in the late Proterozoic (-800-700 Ma), reorganization to Gondwana in the Pan-African (-700-500 Ma) and further accretion to develop Pangea at the end of the Paleozoic. One ofthe Rodinian rifts followed part ofthe Grenville suture, it produced the margin of eastern North America and southern Baltica and the contrasting margin ofwest Gondwana in present South America. The Paleozoic accretionary wedge against the Grenvilleage margin of North America and Baltica contains Avaloniani Cadomian terranes that exhibit Pan-African erogenic events * sediments apparently developed while the terranes were in or near Gondwana. These terranes carry lower-Paleozoic fauna (AcadoBaltic) that are not indigenous to North America and Baltica. The assembly of Gondwana 800-550 Ma Meert J.G. & Van der Voo R., Journal ofGeodynamics, 1997,23/34 (223-235).The formation of the supercontinent Gondwana heralded the beginning of the Phanerozoic following a complex series of collisional events aAer the break-up of earlier supercontinental assemblages. Paleomagnetic data are used to help distinguish between these events and it appears that there are three critical periods of mountain building during Gondwana assembly. The first major erogenic event took place between 800 and 650 Ma and has been termed the East Africa Orogeny. This tectonic episode formed the Mozambique Belt and likely resulted from the collision of India, Madagascar and Sri Lanka with East Africa. The second and third erogenic periods during Gondwana assembly partially overlap in time. The Brasiliano orogeny (600-530 Ma) resulted in the amalgamation of the South American nuclei and Africa. The Kuunga Orogeny was
STRUCTURAL GEOLOGY AND TECTONICS The Protomoesian microcontinent ofthe Balkan Peninsula -a peri-Gondwanaland piece Haydoutov I. & Yanev S., Tectonophysics, 1997, 27212-4 (3033 13)Based on differences in their pre-Palaeozoic and Palaeozoic development, the Protomoesian microcontinent is divided into two terranes: the Balkan and the Moesian. A PrecambrianCambrian ophiolite-island-arc assemblage, unconformably overlain by a Palaeozoic sequence, forms the first terrane. The pre-Palaeozoic basement of the Moesian terrane consists of Proterozoic-Vendian metamorphics of continental origin. The differences in the development of the Palaeozoic rocks are also significant reason for dividing the Balkan and the Moesian terrane. Numerous features of the Palaeozoic sediments (palaeoclimatologic, palaeobiogeographic, palaeomagnetic) from both terranes, and the Pan-African affiliations of the ophioliteisland-arc assemblage, identify the Protomoesian microcontinent as a peri-Gondwanaland piece.
II
Geodynamic models and palaeomagnetic constraints on the evolution of the North West Shelf Klootwijk C., AGSO Research Newsletter, 1997,261- (22-24)After the Middle Cambrian completion of the Rodinia-to-Gondwanaland transformation, northeastern Gondwanaland (ie, ‘Greater India’ and ‘Greater Australia’) was fragmented, and the fragments were widely dispersed. An integral part of northeastern Gondwanaland, Australia’s North West Shelf region has recorded the effects of the wider tiagmentation processes. Detailed knowledge of these processes would help us to unravel the evolution of this major petroleum province. To this end, AGSO’s Marine and Petroleum Division has undertaken a review of geodynamic models and palaeomagnetic constraints relevant to the Phanerozoic evolution of Gondwanaland’s northeastern margin. The main findings are summarised in this report. Neoproterozoic (-600 Ma) aggregation of western Gondwana: a tentative scenario Trompette R., Precambrian Research, 1997, 82/l-2 (IOI112).Gondwana resulted from accretion of fragments of the Rodinia supercontinent. However, precise times and circumstances of individual accretions are still disputed. Aggregation of Western Gondwana occurred at ca 600 Ma or somewhat earlier, with the orogeny closing the old, long-lived Pan-African-Brasiliano tectonic cycle (1000-900 to 600 Ma). It resulted mainly from a submeridional collision between the huge West Africa-Amazon-Rio de la Plata megacontinent, recently broken off the eastern border of Laurentia, and two small continents: the joined Congo-Sao Francisco-Northeast Brazil-Central West Africa continent and the Kalahari continent. Basins related to the second young, and short-lived tectonic cycle opened at ca 600 Ma, or slightly later, and were deformed and metamorphosed around the Early-Middle Cambrian boundary at ca 520 Ma. Most of them were ensialic and did not succeed in breaking up the newly aggregated Neoproterozoic West Gondwana supercontinent. Their rifting was contemporaneous with that of the large Palaeozoic basins such as the Appalachians. Relationship ofAvalonian and Cadomian terranes to Grenville and Pan-African events Mallard L.D. &Rogers J.J.W., Journal of Geodynamics, 1997,23/34 (197-22l).Suturing of the supercontinent Rodinia in the Grenville event (-1000 Ma) was followed by rifting in the late Proterozoic (-800-700 Ma), reorganization to Gondwana in the Pan-African (-700-500 Ma) and further accretion to develop Pangea at the end of the Paleozoic. One ofthe Rodinian rifts followed part ofthe Grenville suture, it produced the margin of eastern North America and southern Baltica and the contrasting margin ofwest Gondwana in present South America. The Paleozoic accretionary wedge against the Grenvilleage margin of North America and Baltica contains Avaloniani Cadomian terranes that exhibit Pan-African erogenic events * sediments apparently developed while the terranes were in or near Gondwana. These terranes carry lower-Paleozoic fauna (AcadoBaltic) that are not indigenous to North America and Baltica. The assembly of Gondwana 800-550 Ma Meert J.G. & Van der Voo R., Journal ofGeodynamics, 1997,23/34 (223-235).The formation of the supercontinent Gondwana heralded the beginning of the Phanerozoic following a complex series of collisional events aAer the break-up of earlier supercontinental assemblages. Paleomagnetic data are used to help distinguish between these events and it appears that there are three critical periods of mountain building during Gondwana assembly. The first major erogenic event took place between 800 and 650 Ma and has been termed the East Africa Orogeny. This tectonic episode formed the Mozambique Belt and likely resulted from the collision of India, Madagascar and Sri Lanka with East Africa. The second and third erogenic periods during Gondwana assembly partially overlap in time. The Brasiliano orogeny (600-530 Ma) resulted in the amalgamation of the South American nuclei and Africa. The Kuunga Orogeny was