The tsunami generated by the Chicxulub impact eroded the uppermost Cretaceous surface of the Gulf Coast region (U.S.A.) forming a distinctive topography that was previously interpreted as a sequence ...boundary. At more distal sites, such as Stevns Klint (Denmark), there appears to be no sequence boundary at the Cretaceous/Paleogene boundary but there is one within the uppermost Maastrichtian, between the Sigerslev and Højerup members, and another in the lowermost Paleocene (top of Zone P1a). Both of these surfaces are identified by distinctive, phosphatized, and incipient hardgrounds. The changes in sea level involved in the generation of uppermost Cretaceous sequences are thought to have been minimal as, in the Gulpen and Maastricht formations of the Maastricht area (Netherlands), the presence of sea grasses and their associated foraminifera would indicate that the chalk sea floor remained within the range of water depth that would allow photosynthesis (<20m), even across the postulated sequence boundaries. The assemblages of foraminifera associated with sea grasses in the uppermost Maastrichtian are comparable in morphology with those associated with modern sea grass meadows and indicate a relationship that may have existed since, at least, the latest Cretaceous.
•Suggests that estimates of Maastrichtian sea level changes are too high•Identifies sequence boundaries above and below the K/Pg boundary•Reports that assemblages of Maastrichtian foraminifera in Maastricht area may reflect seagrass communities•Suggests that foraminifera/seagrass linkage may have been operative since the latest Cretaceous
A re-examination of the uppermost Maastrichtian chalks and an expanded section of the Fish Clay (Fiskeler Member) undertaken at Stevns Klint, Denmark, one of the classic outcrops of the ...Cretaceous/Paleogene boundary, has identified diverse and abundant dinoflagellate cyst assemblages, which are compared with earlier dinoflagellate cyst (dinocyst) studies. The uppermost part of the white coccolith chalk (Sigerslev Member) of the uppermost Maastrichtian is placed in the Palynodinium grallator Zone. The overlying ‘Grey Chalk’ (Højerup Member) represents a shallower-water marine succession that is characterised by a series of dune-like structures. The last common occurrence of P. grallator is within the Højerup Member, confirming the Danian age for the Fish Clay (Fiskeler Member) and a latest Maastrichtian age for the P. grallator Zone. Within the Fiskeler Member, Damassadinium californicum (previously known as Danea californica), a key biostratigraphical marker, is only intermittently present, while the distributions of Senoniasphaera inornata and Xenicodinium reticulatum provide useful biostratigraphic control. The well-preserved dinocysts of the Fiskeler Member are replaced by reduced assemblages in the Cerithium Limestone Member with only pollen grains recorded.
•The K-Pg boundary succession at Stevns Klint is world famous, and has been a reference point for stratigraphy since the mid-nineteenth century.•It is now a World Heritage Site and one of the most important of the distal K/Pg sites.•Previous dinocyst research from Stevns Klint has yielded some strange results that may be due to preparation techniques.•Unfortunately, most of the sampling has been limited to only a few sample points, often where the boundary clay (Fiskeler Member) is thinnest.•Our research allowed us to identify a dinocyst stratigraphy which can be used to compare the Stevns Klint succession with other boundary sections globally.
Mucosal-associated invariant T (MAIT) cells are innate sensors of viruses and can augment early immune responses and contribute to protection. We hypothesized that MAIT cells may have inherent ...adjuvant activity in vaccine platforms that use replication-incompetent adenovirus vectors. In mice and humans, ChAdOx1 (chimpanzee adenovirus Ox1) immunization robustly activated MAIT cells. Activation required plasmacytoid dendritic cell (pDC)-derived interferon (IFN)-α and monocyte-derived interleukin-18. IFN-α-induced, monocyte-derived tumor necrosis factor was also identified as a key secondary signal. All three cytokines were required in vitro and in vivo. Activation of MAIT cells positively correlated with vaccine-induced T cell responses in human volunteers and MAIT cell-deficient mice displayed impaired CD8
T cell responses to multiple vaccine-encoded antigens. Thus, MAIT cells contribute to the immunogenicity of adenovirus vectors, with implications for vaccine design.
Mutations that perturb normal pre-mRNA splicing are significant contributors to human disease. We used exome sequencing data from 7833 probands with developmental disorders (DDs) and their unaffected ...parents, as well as more than 60,000 aggregated exomes from the Exome Aggregation Consortium, to investigate selection around the splice sites and quantify the contribution of splicing mutations to DDs. Patterns of purifying selection, a deficit of variants in highly constrained genes in healthy subjects, and excess de novo mutations in patients highlighted particular positions within and around the consensus splice site of greater functional relevance. By using mutational burden analyses in this large cohort of proband-parent trios, we could estimate in an unbiased manner the relative contributions of mutations at canonical dinucleotides (73%) and flanking noncanonical positions (27%), and calculate the positive predictive value of pathogenicity for different classes of mutations. We identified 18 patients with likely diagnostic de novo mutations in dominant DD-associated genes at noncanonical positions in splice sites. We estimate 35%-40% of pathogenic variants in noncanonical splice site positions are missing from public databases.
Vδ2+ γδT cells are unconventional T cells that can be activated by cytokines without TCR signaling. Adenovirus vaccine vectors activated Vδ2+ γδT cells in an interleukin 18‐, TNF‐, and type I ...interferon‐dependent manner. This stimulatory capacity was associated with adenovirus vectors of non‐species C origin, including the ChAdOx1 vaccine platform.
The terrestrial sediments of the Petrockstowe and Bovey basins in Devon, UK were examined. Their age is considered to be Eocene and Oligocene. The sediments (kaolinitic clays, silts, sands, gravels, ...and lignites) from both basins were analysed for carbon isotopes of organic material, in conjunction with total organic carbon and palynological analyses used to unravel the type of and provenance of organic matter present. Within the Petrockstowe Basin, the lowermost interval examined shows a palynological distribution dominated by phytoclasts, whilst the upper part of the core is dominated by higher concentrations of palynomorphs (up to 90 %) and an increase in amorphous organic matter consistent (up to 37 %) with a change from sand-filled fluvial channels followed by an ephemeral lake or lake margin setting. Our palynological data from the South John Acres Lane Quarry section, Bovey Basin, show that within the lignites palynomorphs are high again (up to 95 %) consistent with them representing more ephemeral lakes or lake margins periodically exposed with mires. Our palynological data set further allows us to determine that isotope trends are not overly determined by the source of carbon in the basins. Our study suggests that the observed patterns were primarily produced by variations of the isotope ratios of terrestrial atmospheric carbon reservoirs. Even with our less than well constrained biostratigraphical control, the data indicate that the carbon isotope excursions seen in the Eocene and Oligocene could be associated with several transient carbon isotopic shifts (associated with the Paleocene–Eocene Thermal Maximum). Our findings therefore appear to lend support to the surface ocean and atmosphere behaving as coupled reservoirs at this time.
This study demonstrates that the Bunkers Hill borehole, which is located within the Hampshire Basin, contains a carbon isotope excursion (CIE) in the Upnor Formation followed by a positive recovery ...from another CIE within the overlying Reading Formation. This study has also shown that the CIE in the Upnor Formation predates the Paleocene/Eocene Thermal Maximum (PETM), while the carbon isotope recovery at the base of the Reading Formation is most likely related to it. The positive carbon isotope trend, before a return to more negative values, seen throughout the majority of the Reading Formation can also be seen in coeval deposits in the Jubilee 404T borehole in the London Basin and in the Tienen Formation in the Doel and Kallo boreholes from the Belgium Basin. This indicates that this post-PETM carbon isotope signal may, therefore, be regional if not global in nature.
Dinoflagellate cyst analysis has been undertaken on three Kasten cores taken from the Falkland Trough, Scotia Sea and Weddell Sea in the area of the Antarctic Peninsula. Two of these cores are ...situated to the north of the maximum sea-ice limit and one, from the Weddell Sea, is sited within the maximum sea-ice limit. The recovered dinoflagellate cyst assemblages underscore the importance of the maximum sea-ice limit as a basic biogeographic boundary for dinoflagellate cyst distributions. Our results also demonstrate that in general the palaeoceanography of the Holocene and Late Pleistocene has remained reasonably constant and reflects present conditions to a large extent. The relatively constant environments, as evidenced within these latest Quaternary sequences, is in marked contrast to the situation within the North Atlantic Ocean where, during the same time span, marked climatic and oceanographic change has been documented from marine, terrestrial and ice-core records. The stability of the Southern Ocean circulation undoubtedly has important consequences on the maintenance of the global thermohaline circulation system over the period since the last deglaciation until the present time.
Dinoflagellate cyst analysis has been completed on core-top samples that form a transect from the area of the Falkland Islands to the Weddell Sea, Antarctica. This study is the first to document the ...distribution of the Recent dinoflagellate cyst thanatocoenosis in the area. All the dinoflagellate cysts recovered are described and at least two species, Dalella chathamense and Selenopemphix antarctica, are recognized as endemic to the southern hemisphere from the results of this study and from previous research. Data presented here reveal a clear latitudinal trend in the cyst distribution such that subdivision into two domains is possible. The first, to the south of 60 degree S, is characterized by low numbers of cysts, low diversity and the presence of Impagidinium pallidum, Algidasphaeridium? minutum, Pentapharsodinium dalei?, round brown Protoperidinium cysts and Selenopemphix antarctica. The second, to the north of 60 degree S, is characterized by richer assemblages, higher species diversity and the presence of Dalella chathamense, Impagidinium sphaericum, Nematosphaeropsis labyrinthus and high numbers of Selenopemphix antarctica. This division of the cyst assemblages coincides approximately with the northern winter limit of sea-ice and demonstrates the potential of dinoflagellate cyst analysis in the elucidation of the palaeoceanography of the area using this criterion.
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