Different Depositional Settings of the Nubian Lithofacies in Libya and Southern Egypt
- J. D. Collinson and
- J. Lewin
Published Online: 29 APR 2009
Copyright © 1983 The International Association of Sedimentologists
Modern and Ancient Fluvial Systems
How to Cite
Bhattacharyya, D. P. and Lorenz, J. C. (1983) Different Depositional Settings of the Nubian Lithofacies in Libya and Southern Egypt, in Modern and Ancient Fluvial Systems (eds J. D. Collinson and J. Lewin), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444303773.ch35
- Published Online: 29 APR 2009
- Published Print: 7 FEB 1983
Print ISBN: 9780632009978
Online ISBN: 9781444303773
- different depositional settings of Nubian lithofacies – Libya and southern Egypt;
- tabular–planar cross-bedded sands;
- depositional environments;
- palaeosol horizons;
- lacustrine deposits
Thick sequences of tabular-planar cross-bedded sands, commonly known as the ‘Nubian Sandstone’, cover wide areas of north-east Africa, and include two major regressive facies: (a) a widespread pre-Cenomanian fluvial facies locally known as the Messak Sandstone (Libya) or the Basal Clastic and the Desert Rose Sandstones (south-west Egypt) and (b) the Taref Sandstone in central and south-east Egypt that marks a brief period of active northward progradation following the Cenomanian transgressive episode over the north-east African platform.
Although the generalized sandbody morphology and internal sedimentary structures of these closely related sandy sequences appear similar, in detail there are subtle but discernible differences between them which are helpful in deciphering their depositional environments.
The sandbodies in the Messak Sandstone are broadly lenticular with interbedded claystone. The sandstones are texturally immature but mineralogically mature, with tabular-planar cross-beds similar to those found in present-day braided stream deposits. Many of the cross-beds are stacked in a series of sets, up to 4 m thick. Local, tectonically controlled ponding produced thick accumulations of clay. The Basal Clastics and the Desert Rose Sandstone, on the other hand, are characterized by dominantly trough to tabular cross-bedded, immature, lenticular sandbodies and well developed interfluve palaeosols, interpreted together as the deposits of a low-sinuosity stream system.
The spectacularly tabular-planar cross-bedded, texturally mature and broadly lenticular sandbodies of the Taref Sandstone in south-eastern Egypt, in contrast, were deposited as distributary channel bars and migrating sandwaves, with intercalations of interdistributary bay mud deposits on a delta plain.