--> Abstract: New Aspects of Saudi Arabian Jurassic Biostratigraphy, by Geraint W. Hughes, Osman Varol, Nigel P. Hooker, and Raymond Enay; #90077 (2008)

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New Aspects of Saudi Arabian Jurassic Biostratigraphy

Geraint W. Hughes1*, Osman Varol2, Nigel P. Hooker1, and Raymond Enay3
1Saudi Aramco
2Varol Research, UK
3Université Claude Bernard - Lyon 1, France
*[email protected]

Age determination of the Saudi Arabian Jurassic carbonate succession was originally based on outcrop macropalaeontology and micropalaeontology, and the essential chronostratigraphy of the formations and members was completed by 1968. It is to the credit of the earlier workers that their age assignments have been largely retained to the present-day. Subsequent biostratigraphic investigations of outcrop samples using ammonite, nautiloid, brachiopod and echinoid macrofossils refined these earlier age determinations. New ammonite and nautiloid determinations have further added to this refinement. In the subsurface, where macrofossils are rarely encountered or preserved within exploratory well samples, lithostratigraphic assignment relies heavily on lithofacies characteristics. Such methodology becomes difficult within intra-shelf basin areas where the defining shallower lithofacies are either poorly developed or absent. In such circumstances, micropalaeontological evidence is essential, with support from nannofossil and palynology. Current research is being focused on the micropalaeontological, nannofossil and palynological calibration between the exposed, macropalaeontologically dated, type or reference sections and subsurface core and cuttings samples. Of these, palynology is beginning to provide new stratigraphically useful data, including outcrop samples, where palynomorph recovery has previously been assumed to be poor and of limited value. Such an approach, using their biostratigraphic fingerprint, is proving successful to assist exploration activities by identifying formations in historical wells where lithostratigraphic units had been miss-assigned resulting in mis-correlations.

 

AAPG Search and Discovery Article #90077©2008 GEO 2008 Middle East Conference and Exhibition, Manama, Bahrain