Possible Causal Mechanisms for Palaeozoic Second-Order Depositional Sequences in the Middle East and North Africa: An Appreciation for Geodynamic Models

Owen E. Sutcliffe, David M. Casey, Roger B. Davies, Peter R. Sharland, and Michael D. Simmons
Neftex Petroleum Consultants Ltd, Oxford, United Kingdom

Biostratigraphic correlation of the disparate lithostratigraphic schemes of the Palaeozoic across North Africa allows correlation with a sequence stratigraphic model developed for coeval successions of the Arabian Plate (as defined by Sharland et al 2001).

It is apparent from these correlations that a number of second-order depositional sequences (O30, S10, D30) are present in both regions, allowing the unification of second-order systems tracts across the north Gondwana margin of North Africa and the Middle East..

Second-order maximum flooding surfaces (MFS) and sequence boundary unconformities are recognised in both intra-shelf basin and platform settings across the North Africa-Middle East region. The bounding unconformities of these sequences can be understood by reference to published geodynamic models for the evolution of Gondwana, thereby identifying likely driving mechanisms for their formation.

It is evident that unconformities bounding two sequences (S10 and D30) reflect the expansion of Gondwanan ice sheets, whilst the development of the O30 sequence is attributed to rifting associated with the separation of Avalonia from Gondwana.

The marine flooding events within these sequences are also widely developed outside Gondwana, resulting in widespread deposition of black shales near to the O40, S10 and D30 second-order MFS on both Laurentia and Baltica.

Furthermore, all of these depositional sequences appear to be intimately linked with the progress of mass-extinction events. These data support the potential global significance of these second-order depositional sequences and assist the development of predictive stratigraphic models that have relevance to petroleum exploration.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005