A sequence of three lignite seams and interlayering carbonaceous mudstone is characterized by geochemical proxies. The study is extended by the palaeoenvironmental details given by the fossil fauna (gastropods, ostracods, and fishes). The predominant minerals (quartz and kaolinite) and main oxide relations of the carbonaceous mudstone point to sand and clay washed from weathered and/or altered felsic rocks from the catchment area. The mudstone features to deposition from suspension in standing or slow to persistently moving fresh waters at the bottom of the core log, and slightly aerated, warm, fresh to low saline, acidic to alkaline waters on the top. Three communities of organisms are depicted. The first is the pre‐swamp environment characterized by standing or slow moving fresh waters and detrital organic matter deposition. The second is the environment of swamp of detrital forest trunks. Depending on the climate and water table, the main forest communities are of trees of families Cupressaceae, Taxodiaceae, and Podocarpaceae accompanied by trees of family Betulaceae, and herbaceous plants. Different Sphagnum species are also abundant. The dry/cold environment is reflected in the herbaceous organic matter deposition. Polar terpenoids ratio differentiates slight climatic oscillations for the samples with a strong Gymnospermae dominance. The second coal seam development reflects the optimum tectonic conditions for peat growth in a cold and dry climate leading up to 25 m lignite deposition. The third is the moss swamp environment with very fluctuating elements. At the top of the log, a Sphagnum‐dominated peat has developed.

Geochemical features of the deep-sea sediments from a high polymetallic nodule area in the eastern part of the Clarion-Clipperton Fractures Zone (CCZ), NE Pacific were studied. Box-corer samples from six stations in individual depth layers 0–3, 3–5, 5–10, 10–20 cm were collected from 4300–4500 m depth. The deep-sea sediments were classified as clayey-siliceous oozes according to the mineral and grain-size analyses. The chemical composition of the studied samples is compatible with that of pelagic sediments. Manganese content varies from 0.16% to 0.70% being the highest in the geochemically active layer (top 7–12 cm) and decreases with depth. The Mn/Fe ratio, Ba, Co, Ni and Cu have the highest values in the first (0–3) and second (3–5) layers and decrease with depth. REE range is 195.84–357.79 ppm showing low variation between the layers. PAAS-normalized REE patterns show significant enrichment of MREE and HREE with strong negative Ce anomaly and weak positive Eu and Y anomalies. The geochemical characteristics of the studied sediments infer polygenic origin. The redox sensitive oxides and barite presense, Eh values and negative Ce anomaly, indicate oxidizing environment of sediment formation.

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The renewed importance of polymetallic nodules in the context of forecasted increasing demands for metals are discussed. Based on the Interoceanmetal Joint Organization’s (IOM) site-specific data obtained during the exploration activity in the Clarion-Clipperton Fracture Zone, a total of 272.5 Mt of nodules were estimated as economically reasonable for future mining for Ni, Cu, Co, and Mn. Additionally, data for REE and other critical elements in nodules as potential by-products are presented.