NEW ARTICLE PUBLISHED ONLINE!

Reassessment of the Salzgitter-Salder section as a potential stratotype for the Turonian–Coniacian boundary: stable carbon isotopes and cyclostratigraphy constrained by calcareous nannofossils and palynology

Silke Voigt, Tobias Püttmann, Jörg Mutterlose, André Bornemann, Ian Jarvis, Martin Pearce and Irek Walaszczyk

Abstract. The abandoned limestone quarry section at Salzgitter-Salder in Germany is a potential candidate for the GSSP (Global Boundary Stratotype Section and Point) of the base of the Coniacian. We present a new high-resolution carbon isotope curve of carbonates (δ13Ccarb) from across the Turonian–Coniacian boundary horizon (TCB) that allows for the precise definition of the Navigation Carbon Isotope Event relative to the occurrences of calcareous nannofossil, organic-walled dinoflagellate cyst (dinocyst) and inoceramid index taxa. The Navigation Event offers a robust global chemostratigraphic marker for the Turonian–Coniacian boundary. A series of subsidiary positive δ13Ccarb events have the potential to serve as markers for regional correlation. Namely, the carbon isotope events i5, i6, and i7 can be used to correlate Salzgitter-Salder to the Běchary Bch-1 core in Bohemia. Spectral analysis shows that these small-scaled peaks are related to high-amplitude signals of precession, confirming an orbital control on δ13C variability. Further, these results indicate a duration of about 100 kyr for the Navigation Event. Carbon isotope and calcareous nannofossil correlation of epicontinental-sea records in Europe and the oceanic record of ODP Site 1259 in the tropical western Atlantic place the Turonian–Coniacian boundary within nannofossil zones CC13 and UC9c. An acme occurrence of the calcareous nannofossil Marthasterites furcatus occurs a short distance above the Navigation Event in Salzgitter-Salder, Bohemia and at Site 1259. An abundance minimum of the dinocyst Palaeohystrichophora infusorioides followed by a marked influx of the taxon coincides with the M. furcatus acme in the European sections. These events offer potential additional markers for the stage boundary.

Newsletters on Stratigraphy (Published online 4th September 2020)
https://dx.doi.org/10.1127/nos/2020/0615

NEW ARTICLE PUBLISHED ONLINE!

Palynology of the Cenomanian to lowermost Campanian (Upper Cretaceous) Chalk of the Trunch Borehole (Norfolk, UK) and a new dinoflagellate cyst bioevent stratigraphy for NW Europe

Martin A. Pearce, Ian Jarvis, Philip J. Ball & Jiří Laurin

A high-resolution palynological analysis of the Cenomanian to Lower Campanian in the Trunch borehole, Norfolk (southern North Sea basin) is documented.  This constitutes the most detailed continuous record of organic-walled dinoflagellate cysts (dinocysts) from a single Upper Cretaceous section to date.  A revised stratigraphic framework for the Trunch succession is presented, integrating regionalmarker bed lithostratigraphy, macrofossil biostratigraphy and carbon-isotope chemostratigraphy.  Palynological events at Trunch are compared to published records with an emphasis on NW Europe, and a new stratigraphy comprising 65 dinocyst events is proposed.  A geochronological age model based on radioisotopic and astrochronological ages of macrofossil biostratigraphic datum levels and global carbon-isotope events (CIEs) is used to revise the age calibration of the Upper Cretaceous δ¹³C_carb carbonate reference curve for the English Chalk, and to calculate absolute ages for the palynological events with an accuracy judged to be ±500 kyr.  The palaeogeographic distribution of key taxa is presented based on records obtained from the PALYNODATA database and additional records, summarised to 212 sites world-wide.  Endemic NW Europe, Northern Hemisphere-wide and global species distributions are demonstrated.  A taxonomic and detailed stratigraphic discussion is provided to determine the likelihood that the events may be considered as global first or last appearance datum levels, or are local to regional lowest and highest occurrences.  Four global, 21 Northern Hemisphere and 40 NW Europe events are tabulated, including 29 inceptions or extinctions of marker species; an additional 36 events may be of regional significance.

Review of Palaeobotany and Palynology, 277, in press
https://doi.org/10.1016/j.revpalbo.2020.104188

NEW ARTICLE PUBLISHED ONLINE!

Oceanic Anoxic Event 2 in eastern England: further palynological and geochemical data from Melton Ross

Paul Dodsworth, James S. Eldrett & Malcolm B. Hart

Abstract. The lowermost 1.45 m of the Welton Chalk Formation, including the regional sedimentary record of Oceanic Anoxic Event 2 (OAE-2), has been sampled at Melton Ross Quarry in eastern England, U.K. The section is investigated for organic geochemistry and stable isotopes for the first time, while a detailed palynological study follows previously published preliminary results. It comprises a condensed interval that spans the Cenomanian–Turonian Stage boundary. A locally preserved, lower 'anomalous' succession (Beds I–VII) and a 'Central Limestone' (Bed A) are shown to correlate respectively with the pre-Plenus sequence and Plenus Bed at Misburg and Wunstorf in the Lower Saxony Basin (LSB), NW Germany. They are overlain by a succession of variegated marls (Bed B to Bed H), including the Black Band (Beds C–E), that can be correlated across eastern England. Based on a carbon isotope (δ13C) profile and dinoflagellate cyst and acritarch bio-event correlation, Beds B–H appear to be a highly attenuated post-Plenus equivalent of the LSB succession, including part of the 'Fish Shale'. The δ13C profile shows possible 'precursor' / 'build-up' events in the lower succession at Melton Ross, with the main OAE-2 δ13C excursion occurring in the Central Limestone and overlying Beds B–H. The darker coloured marls from the Black Band and Bed G contain 1.43–3.47% total organic carbon (TOC), hydrogen index values of 78–203 mg HC/g TOC and oxygen index values of 15–26 mg CO2/g TOC, indicating type III and type II–III organic matter, of mixed terrigenous and marine algal sources. The corresponding palynological assemblages are dominated by marine dinoflagellate cysts, comprising mainly gonyaulacoid taxa, with subordinate terrigenous miospores, mainly gymnosperm bisaccate pollen, consistent with a distal marine setting.  The interbedded lighter-coloured marls contain less than 0.4% TOC and lower proportions of miospores and peridinioid dinoflagellate cysts compared with the darker layers. This is suggestive of moderately raised levels of productivity during deposition of the darker layers, possibly related to greater nutrient availability from land-derived sources. The occurrence of the peridinioid taxa Eurydinium saxoniense and Bosedinia spp., together with higher proportions of prasinophyte phycomata in the darker layers, may also point to stimulation of organic-walled phytoplankton productivity by reduced nitrogen chemo-species encroaching the photic zone, possibly by expansion of an oxygen-minimum zone. Exceptionally high concentrations of palynomorphs (in the tens of thousands to lower hundreds of thousands per gramme range) in the darker layers at Melton Ross and eight other eastern England localities is consistent with increased quality of sea floor preservation in a low oxygen environment, coupled with a high degree of stratigraphic condensation. Two new dinoflagellate cyst species are described from Melton Ross, Canninginopsis? lindseyensis sp. nov. and Trithyrodinium maculatum sp. nov., along with two taxa described in open nomenclature.

Proceedings of the Yorkshire Geological Society, 2020, v63: 88–123.
https://doi.org/10.1144/pygs2019-017

NEW ARTICLE PUBLISHED ONLINE!

Chatangiella islae and Trithyrodinium zakkii, new species of peridinioid dinoflagellate cysts (Family Deflandreoideae) from the Coniacian and Campanian (Upper Cretaceous) of the Norwegian Sea

Martin A. Pearce, Catherine E. Stickley & Linn M. Johansen

Abstract. Two new species of deflandreoid dinoflagellate cysts are described from the Coniacian and Campanian from the 6406/3–6 well, Tyrihans Field in the Norwegian Sea. Chatangiella islae sp. nov. possesses spines that are uniquely restricted to the cingulum, while Trithyrodinium zakkii sp. nov. is distinguished from other species of the genus by spines arising from the endophragm. These species have been known under various informal (and invalid) names and are very important biostratigraphic markers in the North, and Norwegian–Greenland seas.

Review of Palaeobotany and Palynology, 271, in press
https://doi.org/10.1016/j.revpalbo.2019.06.003