Chromium (III) concentrations are stable over the diel cycle yet correlate with NCP, with maxima found in highly productive surface waters but not in lower productivity waters, indicating biological control on Cr (III). 53 53 The relationship between Cr (III) an d δ Cr suggests that δ Cr distributions may be controlled by the removal 53 of isotopically light Cr (III) at an isotopic enrichment factor (∆ Cr) of -1.08‰ ± 0.25 relative to total dissolved 53 53 53 δ Cr, in agreement with the global δ Cr-Cr fractionation factor (-0.82‰ ± 0.05). No perturbation to δ Cr, Cr, or Cr (III) is observed in oxygen-depleted waters (~10 μmol/kg), suggesting no strong control by O 2 availability, in agreement with other recent studies. Therefore, we propose that biological productivity is the 53 53 primary control on Cr and δ Cr in the modern ocean. Consequently, δ Cr records in marine sediments may not 53 faithfully record oxygen availability in the Late Quaternary. Instead, our data demonstrate that δ Cr records may be a useful tracer for biological productivity.

Jayakumar, A., Ward, B.B., 2020. Diversity and distribution of nitrogen fixation genes in the oxygen minimum zones of the world oceans. Biogeosciences Discussions 2020, 1-28.

https://www.biogeosciences-discuss.net/bg-2019-445/ Diversity and community composition of nitrogen fixing microbes in the three main oxygen minimum zones nifH (OMZs) of the world ocean were investigated using operational taxonomic unit (OTU) analysis of clone nifH libraries. Representatives of the all four main clusters of genes were detected. Cluster I sequences were most diverse in the surface waters and the most abundant OTUs were affiliated with Alpha- and Gammaproteobacteria. Cluster II, III, IV assemblages were most diverse at oxygen depleted depths and none of the sequences were closely related to sequences from cultivated organisms. The OTUs were biogeographically distinct for the most part - there was little overlap among regions, between depths or between cDNA and DNA. nifH Only a few cyanobacterial sequences were detected. The prevalence and diversity of microbes that harbour genes in the OMZregions, where low rates of N fixation are reported, remains an enigma.

Jiang, Y., Hu, H., Gluyas, J., Zhao, K., 2019. Distribution characteristics and accumulation model for the coal- formed gas generated from Permo-Carboniferous coal measures in Bohai Bay Basin, China: A review. Acta Geologica Sinica - English Edition 93, 1869-1884.

https://doi.org/10.1111/1755-6724.14290 Coal-formed gas generated from the Permo-Carboniferous coal measures has become one of the most important targets for deep hydrocarbon exploration in the Bohai Bay Basin, offshore eastern China. However, the proven gas reserves from this source rock remain low to date, and the distribution characteristics and accumulation model for the coal-formed gas are not clear. Here we review the coal-formed gas deposits formed from the Permo-Carboniferous coal measures in the Bohai Bay Basin. The accumulations are sca ttered, and dominated 8 3 by middle-small sized gas fields, of which the proven reserves ranging from 0.002 to 149.4×10 m with an 8 3 8 3 average of 44.30×10 m and a mid-point of 8.16×10 m . The commercially valuable gas fields are mainly found in the central and southern parts of the basin. Vertically, the coal-formed gas is accumulated at multiple stratigraphic levels from Paleogene to Archaeozoic, among which the Paleogene and Permo-Carboniferous are the main reservoir strata. According to the transporting pathway, filling mechanism and the relationship between source rocks and reservoir, the coal-formed gas accumulation model can be defined into three types: 'Upward migrated, fault transported gas' accumulation model, 'Laterally migrated, sandbody transported gas' accumulation model, and 'Downward migrated, sub-source, fracture transported gas' accumulation model. Source rock distribution, thermal evolution and hydrocarbon generation capacity are the fundamental controlling factors for the macro distribution and enrichment of the coal-formed gas. The fault activity and the configuration of fault and caprock control the vertical enrichment pattern.

Jiao, X., Liu, Y.-q., Yang, W., Zhou, D.-w., Bai, B., Zhang, T.-s., Zhao, M.-r., Li, Z.-x., Meng, Z.-y., Yang, Y.-y., Li, Z.-x., 2020. Fine-grained volcanic-hydrothermal sedimentary rocks in Permian Lucaogou Formation, Santanghu Basin, NWChina: Implications on hydrocarbon source rocks and accumulation in lacustrine rift basins. Marine and Petroleum Geology 114, 104201.