Abstract

Professor I. G. Gass said that reconnaissance by the Sudan Geological Survey during the period 1952-55 showed the NE Sudan to be primarily a granitic terrain. Within these granites are isolated regions of interbedded pelitic and volcanic sediments on which has been impressed a low grade of metamorphism. These sedimentary masses carry a north-northeasterly structural lineament and depict a regional conformity whereas structures in the surrounding granites are widely at variance to those in the enclosed sediments. The regional picture obtained was that these granite masses quietly invaded the area after the orogenic episode that deformed the sedimentary sequences. He enquired whether studies further to the west, where the sedimentary sequences are more abundant, throw any further light on the problem of the time/space relations between these two major units in the Geology of the NE Sudan.

The Author replied that the work of Professor Gass and his colleagues fifteen years ago in the Sudan Geological Survey provided the basic geological informa­tion concerning the north-eastern part of the country. Little new information has been produced. His own visits to the Red Sea Hills had been brief, but nevertheless he did not think that the sediments and volcanics could be considered as weakly metamorphosed rafts afloat in a sea of granite.

He had been able to show that the regional structures within the metamorphic sequences in the east are not strikingly different from those in the west, or indeed elsewhere in the map-area. The structures within the granitic terrain had not been examined

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