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Paleoceanographic changes of the Indian Ocean and corresponding tectonic events recorded in the Himalayan Range
XII tinctive formation known all over West Africa. This formation is made up of three members, and consists, from base to top, of diamictites generally tillites with detrital intercalations, carbonate rocks with barite, and bedded cherts with local shale or siltstone intercalations. In Eastern Senegal, in the cratonic Taoudeni basin, the carbonate member is palaeontologically dated as Early Cambrian. Deposited during a glacio-eustatic transgression, it can be considered as a chronostratigraphic marker for the entire West Africa. Phosphorites, associated with or immediately following the eustatic transgression, are also possibly of Early Cambrian age. They are located either in the lower part of the chert member, in the upper part of the carbonate member, or sandwiched between these two units. In Fersiga and Name], in the Taoudeni basin, phosphorites are associated with stromatolites characterizing the initial stage of the transgression. They are overlain by evaporites which can be related to an isostatic rebound. In the Volta foreland basin, phosphorites are associated with the chertmember. There, they were deposited on a shelf ramp, either on its proximal portion, where they are strongly reworked (Kodjari and Arli occurrences), or in its distal part where they are interbedded with sediments deposited under anoxic conditions (Tapoa, Mekrou and Aloub Djouana occurrences). The depth of marine sedimentation, as indicated by the sedimentological characteristics of phosphorites andassociated sediments, wascontrolled by thecombined effect of glacio-eustatic sea-level rise, subsidence rate and isostatic rebound. Numerous textural features are similar in the phosphorites from the two basins. Phosphatic grains occurring as oncolites and stromatolitic fragments, together with intraclasts show a noticeable biogenic contribution of microbialorigin. Microbialbuild-upswereformedinsubmerthe Taoudeni basin, andin the gent/emergent environmentsin outer shelf of the Volta basin. Apatites from these basins have similar REE contents, which suggest a continental origin for thephosphorus. EarlyCambrianphosphoritesofWest Africa were deposited soon after glacially derived sedime Some contributions to the Lower Gondwana stratigraphy of the Pranblta-Godavari Valley, Deccan, India Ray S., Journal - Geological Society of India, 1997,50/5 (633640).
The ‘Infra-Kamthi’ Formation is described from the central part of Pranhita-Godavari valley as an essentially sandstone rich horizon with subordinate amount of red mudstone in the lower part and highly ferruginous shale (ironstones) in the upper part of the rock succession. This formation is renamed here as Kundaram Formation, after the village Kundaram in its type area. The northwestern part of the valley has yielded the only known Late Permian reptilian fauna so far found in India. The lithologs reveal a distinct lateral variation of the formation from the sand-dominant central Pranhita-Godavari to red mudstone rich horizon of the northwest. Ironstones are absent. Sheet sand bodies form composite complexes in the lower part of the rock succession followed upward by thick red mudstone units with small lenses of channel-fill sandstone. This package of sediments were probably deposited by anastomosing river channel. Development of the early Paleozoic Pacific margin of Gondwana from detrital-zircon ages across the Delamerian orogen Ireland T.R., Flottmann T., Fanning C.M., Gibson G.M. & Preiss W.V., Geology, 1998, 26/3 (243-246). Detrital-zircon age spectra have been determined for sedimentary rocks from the Delamerian orogen, southern Australia. In Neoproterozoic sedimentary rocks, patterns progressively change from Mesoproterozoicto Neoproterozoic-dominated detritus and there are few zircons that are close to the depositional age. The base of the Cambrian Kanmantoo Group marks an abrupt change in provenance to detrital patterns dominated by Ross and Delamerian (600-500 Ma) and Grenvillean ages (1200- 1000 Ma). These patterns are strikely similar to those obtained from Lachlan fold belt sedimentary rocks, indicating that the sedimentation recorded in
the Kanmantoo Group marks a change from deposition of sediments derived from the Australian cratons to those representative of the early Paleozoic Gondwana mudpile. If sedimentary rocks with zircon-provenance characteristics such as those of the Kanmantoo rocks extend under elements of the Lachlan fold belt, they would provide suitable protoliths for the S-type granites of southeastern Australia. Palaeocurrent pattern and provenance of a part of Gondwana succession, Talcbir Basin, Orissa Das R. & Pandya K.L., Journal - Geological Society of India, 1997, 50/4 (425-433).
The Talchir Group and the Karharbari Formation including a Boulder Gravel Unit of Damuda Group had a predominant northerly palaeoflow with a radiating sediment dispersal pattern suggesting a transverse tilling of the basin. In contrast, the Barakar sedimentation had a unidirectional northwesterly palaeoflow implying an axial filling. The sediments were largely derived from the Eastern Ghat source which occurs along the southern boundary of the basin. The Talchir Group represents a denudation phase of source area with declining relief manifested by a decreasing mean grain size and increasing complexity in the heavy mineral suite due to unroofing of low rank metamorphic rocks at the source. TheDamudaGrouprepresentsasyn-andpost-tectonicphase of sedimentation displaying differences in tectonic style manifested by source area uplift, basin subsidence and steepening of alluvial surface documented by upward increase in grain size, increased complexity in heavy minerals by exposure of high rank metamorphic rocks at source and post-tectonic drainage deflection towards northwest during Barakar sedimentation. Paleoceanographic changes of the Indian Ocean and corresponding tectonic events recorded in the Himalayan Range Nishi H. & Sakai H., Journal - Geological Society qf Japan, 1997, 103/3 (313-327).
This paper reviews the tectonic and paleoceanographicevents based on the investigation of ODP Legs 115 to 123 in the Indian Ocean, and discusses the interaction between events which occurred in the Indian Ocean and in the Himalayan Range. ODP Leg 122 and 123 revealed that the incipient Indian Ocean formed at Argi Abyssal Plain, off the northwest Australia after the late Jurassic breakup of eastern Gondwana. Purely pelagic sediments began to be deposited after the Cenomanian/Turonian anoxic event. The terminal events of the Cretaceous/Paleogene and Palaeocene/Eocene boundaries were recovered in some cores of Legs 119 to 122. The study of Cenozoic magnetic anomalies in the Indian Ocean confirms that the collision between India and Eurasia began between 53 to 55 Ma (the middle Eocene) and coincides with the initiaton of global oceanographic cooling based on paleontological and geochemical data. Sedimentation in the Ganges-Indus submarine fan complexes is controlled by uplift and denudation of the Himalayan Range. The analysis of detrital heavy minerals in the cores of ODP Leg 116 indicates two-phase episodic uplift of the Higher Himalayas, dated at 10.9-7.5 Ma and after 0.9 Ma. Monsoonal upwelling intheIndianOceanstartedatabout lOMa,andmayrepresent the appearance of extensive high mountains and plateau. In the Quaternary, the upwelling records of the western Arabian Sea suggest that southwest summer monsoon became strong during interglacial times, and weak during glacial times. Novedosos hallazgos de Sphenopsida en la Formation Bajo de Veliz, Provincia de San Luis, Argentina (New Sphenopsida from the Bajo de Veliz Formation, San Luis Province, Argentina) Duran M., Hunicken M.A. & Anton A.M., Ameghiniana, 1997, 3413 (259-264).
The new species Tschernovia? velizensis is described. The specimens are compared with illustrations from the palaeofloristic region ofAngara (Russia). Close similarities suggest that
The ‘Infra-Kamthi’ Formation is described from the central part of Pranhita-Godavari valley as an essentially sandstone rich horizon with subordinate amount of red mudstone in the lower part and highly ferruginous shale (ironstones) in the upper part of the rock succession. This formation is renamed here as Kundaram Formation, after the village Kundaram in its type area. The northwestern part of the valley has yielded the only known Late Permian reptilian fauna so far found in India. The lithologs reveal a distinct lateral variation of the formation from the sand-dominant central Pranhita-Godavari to red mudstone rich horizon of the northwest. Ironstones are absent. Sheet sand bodies form composite complexes in the lower part of the rock succession followed upward by thick red mudstone units with small lenses of channel-fill sandstone. This package of sediments were probably deposited by anastomosing river channel. Development of the early Paleozoic Pacific margin of Gondwana from detrital-zircon ages across the Delamerian orogen Ireland T.R., Flottmann T., Fanning C.M., Gibson G.M. & Preiss W.V., Geology, 1998, 26/3 (243-246). Detrital-zircon age spectra have been determined for sedimentary rocks from the Delamerian orogen, southern Australia. In Neoproterozoic sedimentary rocks, patterns progressively change from Mesoproterozoicto Neoproterozoic-dominated detritus and there are few zircons that are close to the depositional age. The base of the Cambrian Kanmantoo Group marks an abrupt change in provenance to detrital patterns dominated by Ross and Delamerian (600-500 Ma) and Grenvillean ages (1200- 1000 Ma). These patterns are strikely similar to those obtained from Lachlan fold belt sedimentary rocks, indicating that the sedimentation recorded in
the Kanmantoo Group marks a change from deposition of sediments derived from the Australian cratons to those representative of the early Paleozoic Gondwana mudpile. If sedimentary rocks with zircon-provenance characteristics such as those of the Kanmantoo rocks extend under elements of the Lachlan fold belt, they would provide suitable protoliths for the S-type granites of southeastern Australia. Palaeocurrent pattern and provenance of a part of Gondwana succession, Talcbir Basin, Orissa Das R. & Pandya K.L., Journal - Geological Society of India, 1997, 50/4 (425-433).
The Talchir Group and the Karharbari Formation including a Boulder Gravel Unit of Damuda Group had a predominant northerly palaeoflow with a radiating sediment dispersal pattern suggesting a transverse tilling of the basin. In contrast, the Barakar sedimentation had a unidirectional northwesterly palaeoflow implying an axial filling. The sediments were largely derived from the Eastern Ghat source which occurs along the southern boundary of the basin. The Talchir Group represents a denudation phase of source area with declining relief manifested by a decreasing mean grain size and increasing complexity in the heavy mineral suite due to unroofing of low rank metamorphic rocks at the source. TheDamudaGrouprepresentsasyn-andpost-tectonicphase of sedimentation displaying differences in tectonic style manifested by source area uplift, basin subsidence and steepening of alluvial surface documented by upward increase in grain size, increased complexity in heavy minerals by exposure of high rank metamorphic rocks at source and post-tectonic drainage deflection towards northwest during Barakar sedimentation. Paleoceanographic changes of the Indian Ocean and corresponding tectonic events recorded in the Himalayan Range Nishi H. & Sakai H., Journal - Geological Society qf Japan, 1997, 103/3 (313-327).
This paper reviews the tectonic and paleoceanographicevents based on the investigation of ODP Legs 115 to 123 in the Indian Ocean, and discusses the interaction between events which occurred in the Indian Ocean and in the Himalayan Range. ODP Leg 122 and 123 revealed that the incipient Indian Ocean formed at Argi Abyssal Plain, off the northwest Australia after the late Jurassic breakup of eastern Gondwana. Purely pelagic sediments began to be deposited after the Cenomanian/Turonian anoxic event. The terminal events of the Cretaceous/Paleogene and Palaeocene/Eocene boundaries were recovered in some cores of Legs 119 to 122. The study of Cenozoic magnetic anomalies in the Indian Ocean confirms that the collision between India and Eurasia began between 53 to 55 Ma (the middle Eocene) and coincides with the initiaton of global oceanographic cooling based on paleontological and geochemical data. Sedimentation in the Ganges-Indus submarine fan complexes is controlled by uplift and denudation of the Himalayan Range. The analysis of detrital heavy minerals in the cores of ODP Leg 116 indicates two-phase episodic uplift of the Higher Himalayas, dated at 10.9-7.5 Ma and after 0.9 Ma. Monsoonal upwelling intheIndianOceanstartedatabout lOMa,andmayrepresent the appearance of extensive high mountains and plateau. In the Quaternary, the upwelling records of the western Arabian Sea suggest that southwest summer monsoon became strong during interglacial times, and weak during glacial times. Novedosos hallazgos de Sphenopsida en la Formation Bajo de Veliz, Provincia de San Luis, Argentina (New Sphenopsida from the Bajo de Veliz Formation, San Luis Province, Argentina) Duran M., Hunicken M.A. & Anton A.M., Ameghiniana, 1997, 3413 (259-264).
The new species Tschernovia? velizensis is described. The specimens are compared with illustrations from the palaeofloristic region ofAngara (Russia). Close similarities suggest that