Published:January 01, 2000
Understanding the complexities of sub-surface stratigraphical interpretations have benefited in the past two decades from the major advances in the development of new seismic techniques. These methods have facilitated a much clearer understanding of the three-dimensional spatial relationships between rock units by focusing on the physical characteristics of the units as reflected by their lithological variation. These methods are however largely oblivious of any direct concept of the relationship of these units to time. In the absence of any easy access to resources which would enable abundant geochronological datasets to be available, the only option available to characterise time in any exploration investigation, albeit in a relative sense, is the establishment of a detailed biostratigraphical framework.
In an ideal situation, the development of biostratigraphical zonation infrastructures concentrates on the investigation of the stratotype and reference sections where the systems, stages and formations were designated and described. Whilst it is conceded that these stratotypical studies represent the keystone of global biostratigraphy, they do not represent the complete picture. Any faunal or floral investigation that is undertaken, be it in a modern environment or in the geological past, readily demonstrates that all faunas and floras are regionally specific, being controlled by the complex interaction of physical factors including latitudinal position, climate, altitude (or depth of water) and in the geological past by the palaeo-distribution of the ancient landmasses. The consequence of this complex equation is that there is a constant need to develop both local and regional biostratigraphies which can be linked together to facilitate meaningful global correlations.
The aspiration for the facilities to enable complete global correlation remains the ultimate goal of biostratigraphy but this target still remains in the distance. Frequently as a result of this incomplete record, the biostratigrapher is compelled to resort to relying on long range comparisons in order to effect correlations and commonly finds himself comparing temperate with tropical areas and shallow with deep water depositionary regimes purely on the basis of the presence of a small number of ubiquitous common taxa. The full potential of biostratigraphy will not be achieved until the network of regionally specific datasets is complete.
Prior to the initiation of the joint Saudi Arabian Oil Company - Commission Internationale de Microflore du Paléozoïque special project in 1990, knowledge of the Palaeozoic biostratigraphy of the Arabian Peninsula highlighted many of the problems listed above. The biostratigraphy of this unique region, part of the mobile Arabian Plate and situated close to the northern margin of Gondwana was poorly known. Only a small number of investigations had been published, and there was a heavy reliance on long range correlations, particularly with the distant Euramerican landmass. Few efforts had been made to exploit the stratigraphical potential of the many undescribed indigenous microfossils. This joint study was designed to reverse that situation.
Unlike studies carried out in temperate regions, the effects of desert weathering on outcrop sections in the Kingdom have serious implications for palynological investigations. These processes of natural weathering leave an oxidised zone, often many metres thick, in which all organic material is destroyed. It was therefore necessary to select alternative sub-surface sections for investigation, which appear wherever possible to reflect the lithological character of the section originally specified as the “type”.
Comprehensive studies were carried out on a range of microfossil groups throughout the Palaeozoic and initial results were published in a special volume in 1995. The papers presented in this second special publication update those initial findings and clearly indicate the potential that these palynomorph assemblages have not only to provide a method for well to well correlations within the Kingdom but also in terms of establishing the palaeobiogeographical relationships of the Arabian Plate to adjacent landmasses. It is indeed fortuitous that the period of this research programme coincided with a significant upturn in palynological activity elsewhere in northern and western Gondwana. Conclusions that are proposed in this volume can now be compared with datasets throughout North Africa and in the central and southern parts of South America. The real potential for an integrated Gondwanan palynozonation programme for Palaeozoic deposits is now beginning to emerge.
Sa’id Al-Hajri Saudi Aramco Dhahran, Saudi Arabia
Bernard Owens University of Sheffield Sheffield, UK
A project of this magnitude could have never been completed without the support and encouragement of some influential people whose help here is most gratefully acknowledged. Mr. Mahmoud Abdul-Baqi, Vice President, Exploration, has guided and encouraged the development of this project throughout its period of execution. We are also grateful to Ibrahim Al-Jallal, Hany Abu-Khadra, Abdulla Al-Naim, Abdul-Jaleel Al-Khalifa, and Kamal Al-Yahya for their administrative assistance during the study. Grateful acknowledgement is also made to Wail Islam, Director of the Deputy Ministry of Petroleum and Minerals of the Eastern Province, for facilitating the approval and release of data.
Appreciation is also due to Moujahed Al-Husseini, G. Wyn Hughes, Mansour Al-Ruwaili, John Filatoff, Riyadh Rahmani, Ali Al-Hawaj, Rachel Preece, Sheldon Nelson and Antony Wyatt for their valuable advice and review of the different manuscripts. We also most gratefully acknowledge Mrs. Janet Lines (British Geological Survey) and Miss Thereze Ward (Exploration Technology Department, Saudi Aramco) for their exceptional secretarial support throughout the term of this project. The staff of GeoArabia are thanked for their editorial support and for designing this publication.
We also acknowledge with gratitude the Saudi Arabian Ministry of Petroleum and Mineral Resources and the Saudi Arabian Oil Company (Saudi Aramco) for the financial support and permission to publish this volume.