Ian Boomer

Crustaceans exhibit a wide range of organic pigments with different colorations and functions. However, little is known about the origin and function of the characteristic green pigmentation that podocopid ostracods, and in particular Eucypris virens, exhibit in their valves. In the present work, we tested the hypothesis that such green pigmentation may be related to the presence of photosynthetic symbionts. First, we performed respiration experiments to test whether anaesthetised individuals of E. virens showed lower oxygen consumption rates under light conditions than in darkness, which could indicate photosynthetic activity. Second, we carried out incubation experiments in a ¹³ C‐enriched medium to test for an increased incorporation of ¹³ C into the ostracod bodies under light conditions. Third, we applied epifluorescence microscopy to check for the presence of autofluorescent pigments in the ostracod valves. Finally, we analysed metagenomic data to characterise the microbiota associated with the ostracod and identify potential photosynthetic symbionts. Our results show that a greater ¹³ C uptake is obtained in the ostracods under light conditions than in darkness, and in the valves than in the ostracod inner bodies, suggesting a greater uptake due to photosynthetic activity in the valves' tissue. Microscopy analyses revealed the presence of small autofluorescent structures in the inner part of the valves compatible with small photosynthetic cells but not matching exactly the whole green area of the carapace. Some respiration experiments showed lower oxygen consumption under light conditions, suggesting balanced effects of oxygen production, while other respiration experiments did not confirm this pattern, pointing to inconclusive results that need to be clarified with further experimental work. Molecular analyses were also contradictory, with the detection of potential photosymbionts in E. virens microbiomes obtained from repositories, but not in fresh analyses from valves or the main body. Despite some contradictory results, this study provides positive evidence on differential ecophysiology of carbon uptake and oxygen balance under light or dark conditions in a freshwater ostracod, suggesting coupled photosynthetic activity. The lack of consistency between experiments might be related to differences between populations or in their biological state. If the positive results are confirmed with further studies, this may represent the first example of photosynthetic symbiosis in arthropods.

The Hypsilophodon Bed occurs at the top of the Wessex Formation (Early Cretaceous, Barremian) on the Isle of Wight, southern England. Numerous remains of the small ornithopod dinosaur Hypsilophodon foxii have been recovered from the bed since the mid-nineteenth century. Previous theories for these fossil occurrences have focused on catastrophic mass death events, including miring and flood-related mortality. However, only limited sedimentological and taphonomic analyses of the horizon and its fossil assemblage have been undertaken, hindering efforts to evaluate different theories about how the assemblage formed. Here, we report a sedimentological study of the bed to constrain its depositional environment, an examination of the matrix from Hypsilophodon fossils to identify where they were collected from within the bed, and a taphonomic investigation of Hypsilophodon specimens. Our results indicate a floodplain environment, which later became a marsh and then mudflats at the edge of a lagoon. Hypsilophodon fossils are spatially and stratigraphically distributed throughout the bed. The specimens are largely incomplete and unabraded, suggesting that most perished on, or near to, the floodplain and may have lain exposed for some time prior to burial. Overall, the evidence suggests that the fossil assemblage of the Hypsilophodon Bed formed as an accumulation of remains over time.

Drilling for the International Continental Scientific Drilling Program (ICDP) Early Jurassic Earth System and Timescale project (JET) was undertaken between October 2020 and January 2021. The drill site is situated in a small-scale synformal basin of the latest Triassic to Early Jurassic age that formed above the major Permian–Triassic half-graben system of the Cheshire Basin. The borehole is located to recover an expanded and complete succession to complement the legacy core from the Llanbedr (Mochras Farm) borehole drilled through 1967–1969 on the edge of the Cardigan Bay Basin, North Wales. The overall aim of the project is to construct an astronomically calibrated integrated timescale for the Early Jurassic and to provide insights into the operation of the Early Jurassic Earth system. Core of Quaternary age cover and Early Jurassic mudstone was obtained from two shallow partially cored geotechnical holes (Prees 2A to 32.2 m below surface (m b.s.) and Prees 2B to 37.0 m b.s.) together with Early Jurassic and Late Triassic mudstone from the principal hole, Prees 2C, which was cored from 32.92 to 651.32 m (corrected core depth scale). Core recovery was 99.7 % for Prees 2C. The ages of the recovered stratigraphy range from the Late Triassic (probably Rhaetian) to the Early Jurassic, Early Pliensbachian (Ibex Ammonoid Chronozone). All ammonoid chronozones have been identified for the drilled Early Jurassic strata. The full lithological succession comprises the Branscombe Mudstone and Blue Anchor formations of the Mercia Mudstone Group, the Westbury and Lilstock formations of the Penarth Group, and the Redcar Mudstone Formation of the Lias Group. A distinct interval of siltstone is recognized within the Late Sinemurian of the Redcar Mudstone Formation, and the name “Prees Siltstone Member” is proposed. Depositional environments range from playa lake in the Late Triassic to distal offshore marine in the Early Jurassic. Initial datasets compiled from the core include radiography, natural gamma ray, density, magnetic susceptibility, and X-ray fluorescence (XRF). A full suite of downhole logs was also run. Intervals of organic carbon enrichment occur in the Rhaetian (Late Triassic) Westbury Formation and in the earliest Hettangian and earliest Pliensbachian strata of the Redcar Mudstone Formation, where up to 4 % total organic carbon (TOC) is recorded. Other parts of the succession are generally organic-lean, containing less than 1 % TOC. Carbon-isotope values from bulk organic matter have also been determined, initially at a resolution of ∼ 1 m, and these provide the basis for detailed correlation between the Prees 2 succession and adjacent boreholes and Global Stratotype Section and Point (GSSP) outcrops. Multiple complementary studies are currently underway and preliminary results promise an astronomically calibrated biostratigraphy, magnetostratigraphy, and chemostratigraphy for the combined Prees and Mochras successions as well as insights into the dynamics of background processes and major palaeo-environmental changes.

A multiproxy oxygen and carbon isotope (d13C and d18O), growth rate and trace element stalagmite paleoenvironmental record is presented for the Early Holocene from Achere Cave, Ethiopia. The annually laminated stalagmite grew from 10.6 to 10.4 ka, and from 9.7 to 9.0 ka with a short hiatus at ~9.25 ka. Using oxygen and carbon isotopic, and cave monitoring data, we demonstrate that the stalagmite deposition is out of isotopic equilibrium, yet trace element and isotope geochemistry is sensitive to hydroclimate variability. Variogram analysis of annual growth rate data suggests that this proxy can only contain hydroclimate information over less than 28-year timescales. Statistically significant and coherent spectral frequencies in d13C and d18O are observed at 15-25 and 19-23 years respectively. Combined with compelling evidence for deposition out of isotope equilibrium, the observed ~1 ‰ amplitude variability in stalagmite d18O is likely forced by non-equilibrium deposition, likely due to kinetic effects during the progressive degassing of CO2 from the water film during stalagmite formation. These frequencies are similar to the periodicity reported for Holocene stalagmite records from Ethiopian caves, suggesting that multidecadal variability in stalagmite d18O is typical. We hypothesise that a hydroclimate forcing, such as runs of one or more years of low annual rainfall, is likely to be the primary control on the extent of the partial evaporation of soil and shallow epikarst water, which is subsequently modulated by karst hydrology, and the extent of in-cave non-equilibrium stalagmite deposition. Combined with possible recharge-biases in drip water d18O, modulated by karst hydrology, these processes can generate multidecadal d18O variability which can operate with opposite signs. Comparison of Early Holocene d18O stalagmite records from the monsoon regions of Ethiopia, Oman and central China show different multi-decadal d18O signals, implying regional difference in climate forcing. Seismic activities due to the active tectonics in the region control the frequency of growth gaps (hiatuses) by changing the water flow paths to the stalagmite.

This study focuses on a condensed sequence of alternating carbonate–clastic sediments of the Barrington Member, Beacon Limestone Formation (latest Pliensbachian to early Toarcian) from Somerset (SW England). Abundant ammonites confirm (apart from the absence of the Clevelandicum and Tenuicostatum ammonite subchronozones) the presence of Hawskerense Subchronozone to Fallaciosum–Bingmanni subchronozones. Well-preserved, sometimes diverse assemblages of ostracods, foraminifera, nannofossils and low-diversity dinoflagellate assemblages support the chronostratigraphic framework. Stable-isotope analyses demonstrate the presence of a carbon isotope excursion, relating to the Toarcian Oceanic Anoxic Event, within the early Toarcian. Faunal, geochemical and sedimentological evidence suggest that deposition largely took place in a relatively deep-water (subwave base), mid-outer shelf environment under a well-mixed water column. However, reduced benthic diversity, the presence of weakly laminated sediments and changes in microplankton assemblage composition within the Toarcian Oceanic Anoxic Event indicates dysoxic, but probably never anoxic, bottom-water conditions during this event. The onset of the carbon isotope excursion coincides with extinction in the nannofossils and benthos, including the disappearance of the ostracod suborder Metacopina. Faunal evidence indicates connectivity with the Mediterranean region, not previously recorded for the UK during the early Toarcian.

Deep-sea benthic foraminifera provide important markers of environmental conditions in the deep-ocean basins where their assemblage composition and test chemistry are influenced by ambient physical and chemical conditions in bottom-water masses. However, all foraminiferal studies must be underpinned by robust taxonomic approaches. Although many parts of the world's oceans have been examined, over a range of geological timescales, the Neogene benthic foraminifera from the southern Indian Ocean have only been recorded from a few isolated sites. In this study, we have examined 97 samples from Neogene sediments recovered from three ODP sites in the southern Indian Ocean (Sites 752, Broken Ridge; 1139, Kerguelan Plateau; 1168, west Tasmania). These data cover a range of palaeolatitudes and water depths during the Miocene. More than 200 species of benthic foraminifera were recorded at each site and, despite their geographic and bathymetric separation, the most abundant taxa were similar at all three sites. Many of these species range from late Oligocene to early Pliocene demonstrating relatively little faunal turnover of the most abundant taxa during the key palaeoclimatic shifts of the Miocene. We illustrate and document the occurrence of the 52 most abundant species (i.e. those with >1 % abundance) encountered across the three study sites.

During much of the Triassic, Britain was largely an emergent landmass with little marine deposition. The main phase of marine deposition only occurred at the end of the Triassic, within the Rhaetian Mercia Mudstone Group, Blue Anchor Formation and the succeeding Penarth Group. A brief marine incursion, probably from the north, also occurred in the middle Triassic. Few ostracod assemblages are known from this period. The main Triassic outcrop and key sites in the British Isles are illustrated in Figure 1. Globally, Triassic ostracod assemblages are generally of low diversity following the end-Permian extinction and the British record is no exception. It is the late Triassic eustatic sea-level rise that opens new biotopes on the transgressed landmasses and mixes marginal marine faunas with new pioneer species.