has captured the attention, fascinated and sustained proponents and users throughout the decades since Liu and Phillips1 were equally enthralled by what they produced, the first time they witnessed their result. This technology update largely addresses developments over the last 2 years (late 2017 - 2019) since the Synovec group presented their review.2 Progressive advances in instrumentation, software and data analysis tools, fundamental relationships and capabilities, and the numerous repertoire of applications to which GC×GC methods have been applied will be included. We attempt to offer an insight into the dynamic nature of the field, and hopefully many newer converts to the field will be recognized for their emerging interest and contributions.

Ameen, C., Feuerborn, T.R., Brown, S.K., Linderholm, A., Hulme-Beaman, A., Lebrasseur, O., Sinding, M.-H.S., Lounsberry, Z.T., Lin, A.T., Appelt, M., Bachmann, L., Betts, M., Britton, K., Darwent, J., Dietz, R., Fredholm, M., Gopalakrishnan, S., Goriunova, O.I., Grønnow, B., Haile, J., Hallsson, J.H., Harrison, R., Heide-Jørgensen, M.P., Knecht, R., Losey, R.J., Masson-MacLean, E., McGovern, T.H., McManus-Fry, E., Meldgaard, M., Midtdal, Å., Moss, M.L., Nikitin, I.G., Nomokonova, T., Pálsdóttir, A.H., Perri, A., Popov, A.N., Rankin, L., Reuther, J.D., Sablin, M., Schmidt, A.L., Shirar, S., Smiarowski, K., Sonne, C., Stiner, M.C., Vasyukov, M., West, C.F., Ween, G.B., Wennerberg, S.E., Wiig, Ø., Woollett, J., Dalén, L., Hansen, A.J., P. Gilbert, M.T., Sacks, B.N., Frantz, L., Larson, G., Dobney, K., Darwent, C.M., Evin, A., 2019. Specialized sledge dogs accompanied Inuit dispersal across the North American Arctic. Proceedings of the Royal Society B: Biological Sciences 286, 20191929. https://doi.org/10.1098/rspb.2019. 1929

Domestic dogs have been central to life in the North American Arctic for millennia. The ancestors of the Inuit were the first to introduce the widespread usage of dog sledge transportation technology to the Americas, but whether the Inuit adopted local Palaeo-Inuit dogs or introduced a new dog population to the region remains unknown. To test these hypotheses, we generated mitochondrial DNA and geometric morphometric data of skull and dental elements from a total of 922 North American Arctic dogs and wolves spanning over 4500 years. Our analyses revealed that dogs from Inuit sites dating from 2000 BP possess morphological and genetic signatures that distinguish them from earlier Palaeo-Inuit dogs, and identified a novel mitochondrial clade in eastern Siberia and Alaska. The genetic legacy of these Inuit dogs survives today in modern Arctic sledge dogs despite phenotypic differences between archaeological and modern Arctic dogs. Together, our data reveal that Inuit dogs derive from a secondary pre-contact migration of dogs distinct from Palaeo-Inuit dogs, and probably aided the Inuit expansion across the North American Arctic beginning around 1000 BP.

Ansari, A.H., Ahmad, S., Govil, P., Agrawal, S., Mathews, R.P., 2020. Mo-Ni and organic carbon isotope signatures of the mid-late Mesoproterozoic oxygenation. Journal of Asian Earth Sciences 191, 104201.

http://www.sciencedirect.com/science/article/pii/S136791201930553X This study performed a redox sensitive trace element (RSTE) and organic carbon isotope investigation on the shallow section of ~1.2 Ga Bijaigarh Shale, Kaimur Group, Vindhyan Supergroup. The results demonstrate that unlike the coeval deeper section, in which Moand Ni concentrations are several-folds higher compared to the upper continental crust (UCC), the shallow section contains Moand Ni equivalent to the upper continental crust (UCC). This spatially heterogeneous burial of Moand Ni is very similar to the modern stratified basins i.e., Black Sea and Cariaco Basin, where Ni and Mo composition of the sediments underlying a shallow oxic water column is comparable to the UCC however, the deeper sediments underlying the anoxic/euxinic contains several folds-higher Mo and Ni compared to the UCC. Bulk precipitation of Mo in a hydrosphere is mainly controlled by sulphide present in the anoxic/euxinic layers of the water column, on the other hand, Ni precipitation is generally controlled by oxygenic primary productivity. Though the shallow section of the Bijaigarh Shale is depleted in Ni, a significant correlation between Ni and TOC is still relevant and indicates an 13 oxygen- rich surface water layer for the respective palaeohydrosphere. Furthermore, δ C-org values (between -32.0 and -30.4‰) from the shallow section suggests that the organic carbon exported into the sediments during the Bijaigarh Shale deposition was primarily derived from oxygenic photosynthesis in the concurrent surface water layers.