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Calcareous Nannofossils Boistratigraphy and Paleoecology of the Late Paleocene/Early Eocene of Wadi Nukhul, Westcentral Sinai, Egypt
Issue:
Volume 4, Issue 2, April 2015
Pages:
59-71
Received:
24 February 2015
Accepted:
9 March 2015
Published:
14 March 2015
Abstract: The calcareous nannofossil biozones NP7/8 through NP12 were identified from the Esna and base of the Thebes formations at Wadi Nukhul, westcentral Sinai. The Subzone NP9a spans the lower part of Esna Formation. The Zone NP10 is easily differentiated into 4 subzones (a-d). The NP9/NP10 zonal boundary can be identified at the level of increase frequency of Neochiastozygus junctus. Zone NP11 occupies the topmost part of the Esna Formation and the base of the Thebes Formation indicating conformable relation between them. The Paleocene/Eocene boundary is traced between the NP9a/NP9b subzonal boundary which is marked by the first- appearances of Rhomboaster spp. It is located at the basal part of the Esna Formation and conforms lithologic change from blackish calcareous shale to brown calcarenite. On the basis of nannofossils, the Paleocene Eocene Thermal maximum (PETM) interval can be divided into two parts (lower and upper). The major assemblage shift across the P/E boundary suggests a change from colder, more productive surface waters to warmer, more oligotrophic conditions. Above the PETM interval, the niche of Fasciculithus spp. was filled by Neochiastozygus juncts and Rhabdolithus solus, the cooler and more eutrophic taxa.
Abstract: The calcareous nannofossil biozones NP7/8 through NP12 were identified from the Esna and base of the Thebes formations at Wadi Nukhul, westcentral Sinai. The Subzone NP9a spans the lower part of Esna Formation. The Zone NP10 is easily differentiated into 4 subzones (a-d). The NP9/NP10 zonal boundary can be identified at the level of increase freque...
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Glaciers Retreat and Climate Change Effect During the Last One Century in the Mestiachala River Basin, Caucasus Mountains, Georgia
Levan G. Tielidze,
Nino Lomidze,
Lasha Asanidze
Issue:
Volume 4, Issue 2, April 2015
Pages:
72-79
Received:
14 March 2015
Accepted:
25 March 2015
Published:
31 March 2015
Abstract: The dynamics of glaciers of Mestiachala river basin for the last century is revised in the paper. The percentage shrinking of areas of compound valley glaciers with the relation of air temperature is given. The retreat of largest glacier of Georgia Lekhziri and shrinking of its area is revised according to the years. The height gradient and correlation between the air temperature data of the only meteorological station (Mestia) of region and air temperature data of the glacier Chalaati in 2011 is determined. The time series of air temperature for Chalaati glacier in 1906-2011 are restored by the using of transfer function. The surface ablation of Chalaati glacier is also calculated. During the study we used a 1:42 000 scale topographic maps of the 19th century, which were drawn up during the first topographic survey by using the plane-table surveying method. Also, we used the catalog of the glaciers of the southern slope of the Caucasus compiled in 1911 by a well-known researcher of the Caucasus K. Podozerskiy, which is drawn up on the basis of the 19th century maps. In order to identify the area and number of the glaciers of the 60s of the 20th century, we used the work of R. Gobejishvili – the Georgian glaciologist of the 20-21st centuries, composed on the basis of 1:50 000 scale topographic maps of 1960. The data of 2014 have been obtained by the Landsat aerial images of L5 TM (Thematic Mapper) taken in August 2014. In the mentioned study, except of the old topographic maps and aerial images we use the climate information of the Mestia weather station.
Abstract: The dynamics of glaciers of Mestiachala river basin for the last century is revised in the paper. The percentage shrinking of areas of compound valley glaciers with the relation of air temperature is given. The retreat of largest glacier of Georgia Lekhziri and shrinking of its area is revised according to the years. The height gradient and correla...
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Global Mid-Ocean Ridges Mantle Tomography Profiles
Desiderius Cyril Patrick Masalu
Issue:
Volume 4, Issue 2, April 2015
Pages:
80-88
Received:
12 March 2015
Accepted:
31 March 2015
Published:
10 April 2015
Abstract: We have studied mantle tomography profiles of global mid-ocean ridges to investigate their depth of origin and other characteristics. The Mid-Atlantic and the South West Indian Ridges are deep rooted ridges that extend as far down in the mantle to 250-300 km. The Central Indian Ridge, South East Indian Ridge, Antarctica Nazca, Pacific Antarctica, Pacific Nazca and Juan de Fuca are shallow rooted ridges that extend down in the mantle only to 100 km. The deep rooted ridges appear to be characterized by a weak low velocity ridge anomaly while the shallow rooted ridges are characterized by strong low velocity ridge anomaly. This may be due to the variations of the geochemistry of the ridges due to the fractionation process during magma ascent. Furthermore, despite the three ridges that make the Indian Rodriguez Triple Junction having different characteristics, all the three sections of the ridges that make the Triple Junction are characterized by strong low velocity ridge anomaly and extended down to only 100 km. This is particularly typical for the length of nine to ten degrees from the Triple Junction which makes it appear as an independent system.
Abstract: We have studied mantle tomography profiles of global mid-ocean ridges to investigate their depth of origin and other characteristics. The Mid-Atlantic and the South West Indian Ridges are deep rooted ridges that extend as far down in the mantle to 250-300 km. The Central Indian Ridge, South East Indian Ridge, Antarctica Nazca, Pacific Antarctica, P...
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