Evaluating the fidelity of the cerium paleoredox tracer during variable carbonate diagenesis on the Great Bahamas Bank

Inferring redox conditions for ancient marine environments is critical to our understanding of biogeochemical cycles over Earth history. Because of the redox sensitivity of cerium (Ce) relative to other rare earth elements (REEs) and its uptake in marine carbonates, the Ce anomaly (Ce/Ce*) is widely applied to ancient carbonates as a proxy for local redox conditions in the water column. However, carbonate sediments and rocks are particularly vulnerable to multiple stages and styles of post-depositional diagenetic alteration where the diagenetic redox conditions and fluid compositions can vary widely from overlying seawater. Evaluations of the effects of this post-depositional alteration for the Ce anomaly have mostly been limited to ancient carbonate rocks rather than recent, well-characterized analog facies. Here, we report on analyses of REE plus yttrium concentrations (REY) and Ce anomalies in bulk carbonate samples from drill cores collected in the Bahamas (Clino and Unda) that allow us to track loss or retention of primary signals of initial oxic deposition through a range of subsequent alteration scenarios mostly under anoxic conditions. Specifically, these materials have experienced well-constrained overprints linked to meteoric processes and marine burial diagenesis, including dolomitization. Our results show that, regardless of mineralogy, diagenetic fluid composition, and redox state, the REY patterns in these carbonates, including the Ce anomaly, are similar to those of modern oxic seawater, indicating that they likely record the seawater signatures of primary deposition. As such, the Ce anomaly in shallow marine carbonates has the potential to preserve records of primary deposition even when subject to multiple stages and styles of diagenetic alteration, confirming its utility in studies of ancient marine redox

Limited iodate reduction in shipboard seawater incubations from the Eastern Tropical North Pacific oxygen deficient zone

The relative abundance of the inorganic iodine species, iodide and iodate, are applied to characterize both modern and ancient marine oxygen deficient zones (ODZs). However, the rates and mechanisms responsible for in situ iodine redox transformations are poorly characterized, rendering iodine-based redox reconstructions uncertain. Here, we provide constraints on the rates and mechanisms of iodate reduction in the Eastern Tropical North Pacific (ETNP) offshore ODZ using a shipboard tracer–incubation method. Observations of iodate reduction from incubations were limited to the top of the oxycline (σθ∼25.2kgm−3) where native oxygen concentrations were low, but detectable (≈11 μM). Incubations from additional depths below the oxycline—where O2 was <2 μM—yielded no detectable evidence of iodate reduction despite hosting the lowest iodate concentrations. These experiments place an upper limit of iodate reduction rates of generally <15 nM day−1 but as low as <2.3 nM day−1, which are based on variable precision of individually incubated replicates between experiments. Experimental inferences of limited or slow iodate reduction in the ODZ core relative to that observed in the oxycline are generally consistent with iodate persistence of up to 70 nM and low biological productivity in this zone. We also compare dissolved iodine and oxygen concentrations between variable water masses of the ETNP and globally distributed open ocean ODZs. Consistent with sluggish reduction rates, comparison of iodate concentrations with previously published water mass analyses within the ETNP ODZ (σθ=26-27kgm−3; O<27μM) demonstrate iodate as a semi-conservative tracer at least partially reflecting regional water mass mixing. A compilation of iodate and dissolved oxygen concentrations from global ODZs generally supports that at least some iodate variations in both vertical and lateral transects largely reflect variable combinations of relatively slow reduction and mixing of iodate reduction signals generated in adjacent regions—as opposed to solely rapid in situ processes. In this context, the variations in iodine speciation inferred for the ancient and modern ocean represent a combination of in situ processes and regional mixing between water masses that retain variable spatially and temporally integrated redox histories

A novel haemophilia B defect due to partial duplication of the factor IX gene

Summary. A patient with mild FIX deficiency was found to have partial duplication of the 3' region of the gene, giving, in addition to the a normal gene, another piece of DNA containing exons 5', 6', 7' and 8' and the intervening sequences. Cloning and sequencing of the junction region revealed that crossover occurred at nt 31927 in the 3° untranslated region of one chromosome/chromatid and nt 10640 in intron 4 of the other. No homology or topoisomerase specific sequences were observed in the crossover region. PCR and sequencing of illegitimate FIX transcripts from the patient's lymphocytes showed at least three different species of mRNAs. Translation of two of these 'novel'mRNAs should result in truncated proteins. Possibilities for the splicing of the mature mRNA are offered to explain the translation of a normal-size FIX protein, which was the only product demonstrated on Western blot analysis