Thin Section Biostratigraphy of Mesozoic Carbonates

Thin Section Biostratigraphy of Mesozoic Carbonates

While we regularly design and co-ordinate integrated biostratigraphic analysis programmes in conjunction with an established network of world-class associates, Oolithica also has significant in-house specialist expertise in thin section biostratigraphy, particularly the identification of Mesozoic microfossils.

Our expertise extends not just to conventional fossil groups such as benthic foraminifera and calcareous algae, but also to other stratigraphically important components such as stromatoporoids, calcareous dinocysts and microproblematica which often go unrecognised or are disregarded by other workers.

Stromatoporoids qualify as honorary microfossils as they are typically speciated in thin section.  They have great value in Middle Jurassic to Upper Cretaceous shallow-water successions where they allow age determinations and refined palaeoenvironmental interpretations to be made.

Detail of the Late Callovian stromatoporoid Actostroma damesini which is characterised by dense closely-packed dark spicules within the axial part of the fibrous walls.  This species is characteristic of the upper Tuwaiq Mountain Limestone of Saudi Arabia and its lateral equivalents.

Microproblematica and calcareous dinocysts often occur in significant abundance in offshore deposits, particularly so in source-prone intrashelf basin facies which characterize several major ‘unconventional’ play fairways.  They are small enough to be identifiable in ditch cuttings thin sections, thus enabling age determinations to be made under circumstances where larger benthic foraminifera and calcareous algae are often of little use.

The enigmatic Oxfordian to Early Kimmeridgian calcimicrobe Gahkumella huberi which forms microbial build-ups at the rim of the Gotnia intrashelf basin in northern Arabia. Gahkumella could evidently tolerate extreme hypersalinity.

Calcareous dinocysts in particular offer exceptional stratigraphic resolution in Oxfordian to Lower Tithonian successions, prior to the occurrence of calpionellids and the major diversification of planktic foraminifera.  They are also useful where other fossil groups are environmentally excluded, as for example in the mid Cretaceous Khatiyah/Shilaif source rock of the Middle East.

Detail of the Oxfordian - Early Kimmeridgian calcareous dinocyst Commitosphaera czestochowiensis.  This species is characteristic of the Diyab source rock and the age-equivalent basinal Hanifa of eastern Arabia.

We have unrivalled experience and expertise in working with these unconventional fossil groups in the southern Tethyan realm.