Urquhart, Elspeth; (1992) Upper Cretaceous radiolaria from the Atlantic Ocean and Cyprus. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Micropalaeontological analyses, with special reference to radiolaria, have been carried out on 255 samples of Campanian - Maastrichtian sediments from 3 sections encountered at offshore DSDP/IPOD Sites in the Atlantic Ocean and 20 onshore sections in Cyprus in the Mediterranean sea. Radiolarian assemblages recorded here are integrated with calcareous nannofossils where possible, the studied sections having been carefully chosen in order to test existing biostratigraphical schemes using radiolaria and calcareous microfossils. Of the published zonation schemes for the Late Cretaceous, seven are discussed and their application to material recorded here considered. A number of interesting biostratigraphical observations confirmations and conclusions have been made in relation to the geological history of Cyprus, whilst the radiolarian biostratigraphical database from DSDP Sites 152 and 369A has been amended. A taxonomic atlas has been compiled, with extensive synonymy lists and the geographical and stratigraphical occurrence patterns both for published species and for new forms recorded exclusively in this study. The stratigraphical occurrences recorded here are correlated with co-occurring calcareous nannofossils. The taxonomic atlas includes 141 taxa and 47 genera which are described and/or figured. Of these morphotypes, 59 are left in open nomenclature, many of which represent new and undescribed species to be formally described when their occurrence patterns are fully researched. Eighty-two of the species recorded have published ranges which include the Campanian whilst the ranges of a further 11 species are here extended into the (stratigraphically higher) Campanian stage. Published radiolarian ranges are confirmed and extended. The organisation and storage of the lithological and micropalaeontological data from this study on a computer database allowed for rapid searches for correlative and inversely correlative sample characteristics. Equally, future rapid selection of samples for purposes such as refining zonation schemes or selection of particularly well-preserved specimens for photography or specific reappraisal is facilitated. Controls on production and preservation of siliceous microfossils are discussed and applied to the interpreted depositional conditions in the Late Cretaceous. The effects of these controls, as interpreted for the Late Cretaceous, are discussed in relation to biostratigraphical utilization of the group. A comprehensive assessment of sample processing and analytical techniques and a discussion on the technical problems encountered, together with their impact on recorded data, is included. Finally, future research areas have been defined in relation to the following : 1. developing/refining radiolarian biozonation; 2. standardization of preparation techniques, data production and storage; 3. advancement of stored computerised data to include pictorial representation of taxa; 4. more extensive work on Cyprus involving correlation with DSDP/ODP material.

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