173 research outputs found

    Summary of the new stratigraphic guide to the Chalk Group in the UK and Norwegian sectors of the North Sea

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    This brief guide summarizes the updated and unified stratigraphy of the Chalk Group for the UK and Norwegian sectors in the North Sea. The information was presented at the ‘Chalk of the Northern Province’ symposium held in Hull on 12 September 2015. The update rationalizes Chalk Group lithostratigraphy across the North Sea, reducing the need to use unique names for reservoir units, without proper documentation or lack of biostratigraphic and correlative insight

    Stratigraphic Guide to the Cromer Knoll, Shetland and Chalk Groups, North Sea and Norwegian Sea

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    This guide provides a major revision and update of the stratigraphy of the Cromer Knoll, Shetland and Chalk Groups for the UK and Norwegian sectors in the North Sea, and of the Cromer Knoll and Shetland Groups in the Norwegian Sea. The first chapters deal with the paleoceanographic and geologic settings and updated biostratigraphy, followed by the chapters with the new and improved lithostratigraphy. The Cretaceous biostratigraphy calculated for the microfossil record in 37 Norwegian wells integrates over 100 foraminifer, dinoflagellate cyst, diatom and miscellaneous events in nineteen zones, numbered from NCF 1 through NCF 19 (North Sea Cretaceous Micro Fossil Zones 1–19). A literature based Dinoflagellate Cyst Zonation (DCZ), linked to the NCF zones, is also presented with eleven zones and thirty-nine subzones for Cretaceous marine strata in the North Sea. Both zonations are optimized for industrial applications with ditch cuttings samples. The lithostratigraphy of the North Sea, unified for the UK and Norwegian sectors describes 3 groups, 30 formation units and one member. The Cretaceous lithostratigraphy for the Norwegian Sea describes 2 groups, 17 formations and 14 members. This (long overdue) update alleviates misnaming and incidental use of unique names for reservoir units, without documentation and lack of biostratigraphic and correlative insight. The internet site www.nhm2.uio.no/norlex and the CD inserted with this publication provide core archives for the lithostratigraphic units

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    New insights into the taxonomy and evolution of Jurassic planktonic foraminifera

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    Abstract Globuligerina glinskikhae nov. sp. Gradstein & Waskowska and Globuligerina waskowskae nov. sp. Gradstein are new species of Jurassic planktonic foraminifera from the Middle Jurassic of Dagestan and Poland. G. glinskikhae nov. sp. with its remarkable ‘protoglobigerine’ test may be an early evolutionary offshoot of Globuligerina oxfordiana (Grigelis). It may be an index taxon for upper Bajocian through Bathonian strata in Eastern Europe and Southwest Asia, and might be recognizable also in thin sections. We consider G. waskowskae nov. sp. to be a possible forerunner of Conoglobigerina helvetojurassica (Haeusler), the first planktonic foraminiferal species with a reticulate wall texture. Currently, is only known from Poland. In some localities, specimens of G. oxfordiana and of G. glinskikhae nov. sp. posses an additional apertural opening, often lacking a rim; its function is enigmatic. The postulated lineage from Jurassic Globuligerina balakhmatovae (Morozova) to Cretaceous Clavihedbergella eocretacea Neagu is refined with the description of Petaloglobigerina simmonsi nov. gen., nov. sp. Gradstein from the Kimmeridgian of Portugal. The evolutionary transition from G. balakhmatovae to P. simmonsi occurs by means of the ontogenic development of a petaloid test, with a pronounced flattening of the whorl with ovate chambers, the last ones often offset and twisted. Jurassic planktonic foraminifera, now known to consist of three genera and 12+ species underwent long periods of stasis, interrupted by late Bajocian, mid-Oxfordian and early Kimmeridgian evolution. The three ‘stasis and root’ taxa G. oxfordiana , G. bathoniana and G. balakhmat ovae are geographically widespread in lower to mid palaeo-latitudes, and stratigraphically long ranging within the Middle and Late Jurassic. Modern digital microscopes, with co-axial and side LED lighting and excellent image stacking software are important tools in the study of Jurassic planktonic foraminifera, and fast and cost-effective communication tools in modern micropalaeontology
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