The organic-rich, black mudstones that were initially described as the Black Band in Lincolnshire, Humberside and Yorkshire are known to be a local representation of the Cenomanian-Turonian Boundary ...Event (CTBE). This world-wide event is known as Oceanic Anoxic Event ll (OAEll) and it marks a distinctive extinction event within the Cretaceous biota. Since some of the original work on the benthic foraminifera that are found in both the Black Band and coeval sedimentary rocks, there has been a significant increase in the understanding of the biology of foraminifera, and their response to both modern and fossil low-O2 environments. While the overall event is clearly global, the local response appears to be a function of both geological setting and water depth with the occurrence of organic-rich sediments as a combination of this setting, plankton productivity and preservation.
Statoliths, in modern cephalopods, are the paired calcareous ‘stones’ that lie in two adjacent cavities (or statocysts) within the cartilage of the head. The stones are generally 0.5–2.0 mm in length ...and appear to be formed of aragonite. Statoliths often co‐occur with fish otoliths, and being of similar appearance, size, colour, etc., this has caused confusion in the past. It was only towards the latter part of the twentieth century that it was recognized that statoliths could occur as fossils.
The Jurassic succession of the Wessex Basin, especially that cropping out along the Dorset Coast, contains important Lagerstätten for coleoid cephalopods. The Blue Lias and Charmouth Mudstone ...formations have, since the nineteenth century, provided large numbers of important body fossils that inform our knowledge of coleoid palaeontology. In many of these mudstones specimens of palaeobiological significance have been found, especially those with the arms and hooks with which the living animals caught their prey. This is particularly true in the case of a specimen of Clarkeiteuthis sp. cf. C. montefiorei (Buckman, 1879) found in the nineteenth century with a fish in its jaws and which appears to have caused the death, and subsequent preservation, of both animals.
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, UK. 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 seafloor 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. Supplementary material: One pdf file, with detailed sample positions and descriptions, tables of supporting information (also available in Excel format), quarry photographs and a palynological distribution chart, is available at https://doi.org/10.6084/m9.figshare.c.4987205
In the 1960s and 1970s Werner Fuchs of the Austrian Geological Survey (Vienna) described a significant number of new foraminiferal taxa that he considered ancestral to the planktonic foraminifera. ...All these taxa are well-curated in the collections of the Austrian Geological Survey and have been studied by one of us (Malcolm B. Hart). Some of these taxa, from the Triassic and lowermost Jurassic strata of Austria and northern Italy, are poorly preserved, possibly the result of having an original aragonitic wall structure. None of these taxa possess characters which give the appearance of a planktonic mode of life, although some of them (e.g. Oberhauserella, Praegubkinella) may well have been ancestral to the holoplanktonic foraminifera that appeared in the Toarcian and younger strata. Other taxa in the collections of the Austrian Geological Survey (part of GeoSphere Austria), from the Jurassic of Poland, are preserved as glauconitic steinkerns and are either unidentifiable as foraminifera or suspect in terms of their stratigraphical and evolutionary significance.
Jurassic (Bathonian–Oxfordian) planktic foraminifera from the
epicontinental strata of the Polish Basin have been investigated. The
palaeoecology, palaeobiogeography, and biostratigraphical potential ...of the
recorded taxa are discussed. Four species are recorded: Conoglobigerina helvetojurassica (Haeusler, 1881),
Globuligerina balakhmatovae (Morozova, 1961), G. bathoniana (Pazdrowa, 1969), and G. oxfordiana (Grigelis, 1958). This assemblage is
probably the most diverse of those described to date from the epicontinental
areas of Europe. The recorded taxa are thought to represent three different
ecological morphotypes. The clear relationship between
transgressive–regressive facies and the palaeobiogeography of the recorded
planktic foraminifera indicates a morphotype-related depth–distribution
pattern in which small, simple, globular-chambered morphotypes occupied
shallow waters whereas slightly larger, more complex forms, or those with
hemispherical chambers, inhabited deeper and more open-water environments.
Isotopic data (C and O) derived from Callovian (Middle Jurassic) mollusks (bivalves, ammonites and belemnoids, including true belemnites and Belemnotheutis) are presented from a narrow stratigraphic ...interval in the Christian Malford Lagerstätte, UK. The exceptionally well-preserved mollusks include aragonite-calcite pairs precipitated by individual belemnite animals that enable an assessment of possible “vital” effects and the reliability of using belemnite calcite to determine ocean water compositions. The oxygen isotope data derived from the calcitic rostra of the belemnites (Cylindroteuthis) show modest variability, ranging from −1.2 to 0.9‰ (V-PDB), while their accompanying aragonitic phragmocones range from −1.4 to 0.0‰. Data derived from the ammonite Kosmoceras show some scatter, with oxygen isotope values varying from −3.6 to −0.2‰. The aragonite data from Cylindroteuthis, Kosmoceras and Belemnotheutis all overlap, suggesting they inhabited similar (surface) water depths. However, the corresponding data from the calcitic rostra of the Cylindroteuthis specimens suggest temperatures ~ 5°C cooler. As we have analyzed aragonite-calcite pairs, the discrepancy cannot be explained by environmental effects. Though clearly a vital effect, it is difficult to resolve whether the temperatures derived from the aragonite (phragmocone) are too warm or from the calcite (rostrum) are too cool. Consequently, the applicability of standard paleotemperature equations to Cylindroteuthid belemnite rostra remains unproven. Sequentially sampled ontogenetic isotope data derived from Belemnotheutis phragmocones reveal only modest δ18O variation, consistent with limited movement between warmer (shallower) and cooler (deeper) waters. A coincidental systematic pattern of δ13C enrichment may signal changes in metabolic activity associated with a shift in ecology or feeding with age.
Recent concern over the effects of ocean acidification upon calcifying organisms has highlighted the aragonitic shelled thecosomatous pteropods as being at a high risk. Both in-situ and laboratory ...studies have shown that an increased dissolved CO2 concentration, leading to decreased water pH and low carbonate concentration, causes reduced calcification rates and enhanced dissolution in the shells of living pteropods. In fossil records unaffected by post-depositional dissolution, this in-life shell dissolution can be detected. Here we present the first evidence of variations of in-life pteropod shell dissolution due to variations in surface water carbonate concentration during the Late Pleistocene by analysing the surface layer of pteropod shells in marine sediment cores from the Caribbean Sea and Indian Ocean. In-life shell dissolution was determined by applying the Limacina Dissolution Index (LDX) to the sub-tropical pteropod Limacina inflata. Average shell size information shows that high in-life dissolution is accompanied by smaller shell sizes in L. inflata, which may indicate a reduction in calcification rate. Comparison of the LDX profile to Late Pleistocene Vostok atmospheric CO2 concentrations, shows that in-life pteropod dissolution is closely associated to variations in past ocean carbonate saturation. This study confirms the findings of laboratory studies, showing enhanced shell dissolution and reduced calcification in living pteropods when surface ocean carbonate concentrations were lower. Results also demonstrate that oceanic pH levels that were less acidic and changing less rapidly than those predicted for the 21st Century, negatively affected pteropods during the Late Pleistocene.
•In-life dissolution of fossil pteropod shells was examined using the LDX scale.•Average shell diameter was used as an indicator of calcification rate.•LDX shows significant correlation to CO2 and surface water carbonate concentration.•Smaller, more corroded shells were found during interglacial periods.•Larger, pristine shells were found during glacial periods.
PDF
