The pyrite sulfur isotope record of the 1.98 Ga Zaonega Formation in the Onega Basin, NWRussia, has played a central role in understanding ocean-atmosphere composition and inferring worldwide fluctuations of the seawater sulfate reservoir during the pivotal times of the Paleoproterozoic Era. That, in turn, has led to a concept that Earth's atmospheric oxygen levels underwent global-scale changes. Here we present a steady-state isotope mass-balance model to gain insight into the mechanisms governing the sulfur cycle and sulfate reservoir during deposition of the organic-rich Zaonega Formation. We demonstrate that coupling between high microbial sulfate reduction rates and effective sulfate removal by pyrite precipitation can lead to Rayleigh 34 distillation of the basinal sulfate reservoir and development of high amplitude positive δ S excursions. This modelling approach illustrates that secular changes in sedimentary pyrite isotope trends can be explained by processes that reflect local (basin-scale) fluctuations in sulfur cycling rather than global mechanisms.

Pan, H., Li, H., Chen, J., Zhang, Y., Cai, S., Huang, Y., Zheng, Y., Zhao, Y., Deng, J., 2020. A unified contact cementation theory for gas hydrate morphology detection and saturation estimation from elastic-wave velocities. Marine and Petroleum Geology 113, 104146.

http://www.sciencedirect.com/science/article/pii/S0264817219305987 Good knowledge of hydrate morphology and accurate quantification of hydrate saturation are significant for reservoir characterization, resource exploitation and geohazards assessment. Although many of empirical or theoretical models have been developed to detect hydrate morphology and predict hydrate saturation from elastic-wave velocities, they either fail to hold true for complex morphologies or cannot provide accurate hydrate saturation estimate. In this study, we propose a unified contact cementation theory by applying the modified Hashin-Shtrikman upper and lower bounds to an extended cementation theory. By merging the cementation theory and effective medium theory, it can be used to account for four types of hydrate morphologies. Numerical modeling results provide some new insights into effects of normalized thickness of hydrate layer, friction coefficient and effective pressure on elastic-wave velocities for different morphologies, which will be helpful for analyzing the borehole stability and determining optimum production-related strategies. In addition, we propose a hydrate morphology-based inversion method by introducing the ratio of multiple hydrate morphologies from statistical analyses and apply it to the acoustic logs from the Mallik 5L-38 permafrost-related gas hydrate research well in Mackenzie Delta and other three marine wells in Nankai Trough and Hikurangi margin. The velocity-based gas hydrate saturation estimations are in good agreement with those predicted from resistivity log and Nuclear Magnetic Resonance measurement, as well as core data, confirming feasibility and applicability of our theory and inversion method, and indicating its potential in seismic characterization of gas hydrate reservoirs.

Pan, Q., Yu, H., Daling, P.S., Zhang, Y., Reed, M., Wang, Z., Li, Y., Wang, X., Wu, L., Zhang, Z., Yu, H., Zou, Y., Sanchi 2020. Fate and behavior of oil spill transported by the Kuroshio during January - February 2018. Marine Pollution Bulletin 152, 110917.

http://www.sciencedirect.com/science/article/pii/S0025326X20300357 The fate and behavior of the Sanchi oil spill during January - February 2018 was simulated by coupling an oil spill model and satellite observations with meteo-oceanographic forcing. Extensive validation tests were performed for winds, currents, surface slick, stranded oil and oil fate. A series of hindcast experiments was designed to take into account the uncertainties in oil amount, environmental forcing and model parameters. The simulations confirmed that the stable large-scale Kuroshio acted as the primary driving force. Most oil followed the Kuroshio's large-meander path, rapidly passing through the East China Sea to the waters south of Japan. The wind, appearing as the secondary transport factor, did not change the path of this large-scale current, but did contribute to the drift of surface oil. The different fates for heavy fuel oil and condensate in the accident were also compared quantitatively and discussed in this study.

Panagiotopoulos, I.P., Paraschos, F., Rousakis, G., Hatzianestis, I., Parinos, C., Morfis, I., Gogou, A., 2020. Assessment of the eruptive activity and identification of the mud breccia's source in the Olimpi mud volcano field, Eastern Mediterranean. Deep Sea Research Part II: Topical Studies in Oceanography 171, 104701.