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In the mid-1850s, Thomas Henry Huxley, who coined the term ‘coccolith’, described their presence in oceanic sediments dredged from the sea floor. Subsequent recognition of their occurrence in the Upper Cretaceous English Chalk, largely unconsolidated pelagic sediment, and similar, more lithified limestones in the Jurassic of the Alps, led to their being considered major rock-forming elements through much of geological time, although they are now known to be limited to the Late Triassic–Recent interval. Unlike Charles Darwin, who did not travel abroad following the voyage of the Beagle , Huxley made a number of trips to Italy and Switzerland and is recorded as a guest in the exclusive Hotel Kursaal Maloja in the Engadin in 1893. While staying there, he made a number of excursions on foot and his presence was thought significant enough that it is recorded in an inscribed granitic stone tablet, erected in 1896, describing him as’the illustrious writer and naturalist’. His rambles would have led him past outcrops of tectonically emplaced true oceanic calcareous sediment of Early Cretaceous age, here shown to have originally contained coccoliths that were largely destroyed under the imprint of Alpine metamorphism of sub-greenschist to greenschist facies. To this extent, Huxley could have come close to recognizing true oceanic sediments exposed on land, but the dissimilarity between these Swiss Alpine deposits and the friable English Chalk would not obviously have led to the investigation of the former for the organisms he had christened as ‘coccoliths’.

Various enriched recycled oceanic components in the source of Cenozoic intra-plate alkaline basalts from eastern China were identified by previous studies. Due to the existence of a stagnant subducted Pacific slab in the mantle transition zone beneath eastern China, it is logical to connect the stagnant slab to the recycled oceanic materials. However, the recycled oceanic materials could also result from ancient subduction events (e.g., Paleo-Tethyan, Paleo-Asian or Izanagi plate subduction) because enriched geochemical signatures of a recycled slab can be preserved in the mantle for longer than 1 Gyr. Investigating the temporal variations of the recycled oceanic materials in the mantle source is a useful way to trace the origin of the basalts. In this article, we have conducted a detailed geochemical study, including major and trace elements and Sr–Nd–Pb isotopes, on two alkaline basalt groups from Zhejiang, SE China, which erupted 26–17 Ma and after 11 Ma, respectively. In particular, we recovered the H 2 O content of the initial magmas based on the H 2 O content of the clinopyroxene (cpx) phenocrysts and the partition coefficients of H 2 O between cpx and basaltic melts. The H 2 O contents of the Zhejiang basalts range from 1.3 to 2.6 (wt.%), which fall within the range of back-arc basin or island arc basalts. The older basalts are more alkaline and have lower Si and Al contents; higher trace element concentrations; higher La/Yb, Ce/Pb and Nb/La ratios; lower H 2 O/Ce and Ba/Th ratios; and stronger negative K, Pb, Hf and Ti anomalies than the younger ones. The co-relationships between Ba/La, H 2 O/Ce, Nb/La, Ce/Pb and Ba/Th in the two groups of the Zhejiang basalts indicate that a recycled dehydrated oceanic alkaline basalt component is needed in the source of the older rocks, along with a depleted mantle component. Meanwhile, an additional recycled dehydrated sediment component was required in the source of the younger rocks. The temporal change in the recycled oceanic materials in the mantle sources of Zhejiang Cenozoic basalts demonstrates that the recycled components can only originate in the stagnant Pacific slab that is the only plate subducted since 100 Ma in this area.

To certify the suitability of pretreatment by thermal drying to measure iodine concentrations of oceanic sediment and terrestrial soil samples, changes in iodine concentrations after drying (50, 80 or 85, and 110 °C for 48 h) were examined using the samples in addition to a terrestrial plant (pine needles), which was selected as an intact organic sample. The iodine concentrations per wet weight of the sediment and soil samples processed by thermal drying were comparable to those of the raw samples at all temperatures. However, the concentrations of the plant samples dried at 85 and 110 °C were lower than those of the raw samples. The lower concentrations of the plant samples at higher temperatures were considered to be derived from the volatilization of a part of the plant’s organic matter. Finally, these results suggested that the iodine concentrations in oceanic sediment and terrestrial soil samples scarcely change after thermal drying at 110 °C, although the concentrations may decrease when these samples include high contributions of fresh organic matter.

High-throughput sequencing of the 16S ribosomal RNA (16S rRNA) gene has been successfully applied to explore the microbial structure and dynamics in various environments. The distinctive microbial communities in oceanic trench sediments are expected because of the extremely high pressure and V-shape topology that caused the isolation from the other marine sediments. However, they have only been primarily targeted using ‘universal’ primers that provide variable performances for different environments. It is necessary to design specific primers to improve the detection resolution of unique microbial groups in oceanic trenches. Here, we designed one pair of bacterial and two pairs of archaeal specific primers based on 16S rRNA gene full-length sequences that truly come from trench sediment and tested their performances in 30 oceanic trench sediment samples. An in silico analysis showed that the V3–V4 hypervariable region was the most informative and representative for oceanic trench microbial groups. Compared with the ‘universal’ primers, 46 bacterial families were only detected by newly designed primer B344F/B749R, and eight archaeal families were only detected by the newly designed primer A306F/A713R which covered the one or two orders of magnitude more ASVs (amplicon sequence variants) (1,470,216) in the tested total 30 samples. Moreover, A306F/A713R had the largest number of observed ASVs suggesting its better performance in discovering more archaeal species which were easily ignored in universal primer-based experiments for oceanic trench sediments. The novel primers designed in this research could be a better option to access the unique microbial communities in extreme oceanic trench sediments. Key points • Defining V3–V4 as the most adequate hypervariable region for archaea and bacteria from oceanic trench sediments. • Three sets of bacterial and archaeal primers appear validity and advantage in revealing the real trench microbial communities. • The novel primers provide a better option to specifically detect the unique microbial communities in extreme oceanic trench sediments.

The CRC Marine Science Series is dedicated to providing state-of-the-art coverage of important topics in marine biology, marine chemistry, marine geology, and physical oceanography. The series includes volumes that focus on the synthesis of recent advances in marine science.

This study demonstrates the effects of growth stimulators in oceanic sediment on biomass and lipid production of two oleaginous microalgae, Botryococcus braunii LB572 and Phaeodactylum tricornutum B2089. At the optimal mixing ratio of culture medium and oceanic sediment extract of 6:4 (v/v), specific growth rates of B. braunii LB572 and P. tricornutum B2089 increased 13.0- and 11.3-fold, respectively, compared to a sediment-free medium. The maximum biomass and lipid productions of B. braunii LB572 were 5.54 and 3.09 g L−1, and those of P. tricornutum B2089 were 6.41 and 3.61 g L−1, respectively, indicating that biomass and lipid production in both microalgae increased at least 6- and 8-fold, respectively. Thus, their cultivation time was reduced by at least 6 days. A positive effect of nitrate in the sediment on biomass and lipid production was not found. Fe3+ and Ca2+ promoted biomass and lipid production as their concentrations increased. However, metal ion concentration is not as critical to biomass and lipid production as humic acid, a chelating substance to enhance bioavailability of metal ions to the microalgae. The optimal humic acid concentration for maximal biomass and lipid production was 80 mg L−1, which is the concentration contained in the culture medium mixed with sediment extract at a ratio of 6:4 (v/v). Thus, low-cost oceanic sediment can supply sufficient growth stimulators, especially humic acid, for mass production of biomass and lipid in both microalgae.

The Amur and Kiselevka–Manoma accretionary complexes belong to the Cretaceous Khingan–Okhotsk active continental margin, which was formed in the east of Eurasia as a result of the subduction of the Pacific oceanic plates. The Kiselevka–Manoma complex is composed of oceanic pelagic and hemipelagic sedimentary rocks and intraplate oceanic basalts. It is located to the southeast, along the ocean-faced front of the Amur complex, which is predominantly composed of turbidites of the convergent boundary of lithospheric plates. The biostratigraphic study of radiolarians from rocks of the frontal part of the Amur complex allowed us to correlate them with rocks of the Kiselevka–Manoma complex and to define the period of accretion to be from the Late Aptian to the Middle Albian. The tectonostratigraphic interrelations of these two contrasting lithotectonic complexes are established and two possible models of their common emplacement are suggested. Both models suppose a continuous spatiotemporal relation of complexes with the primary paleolocation of the Kiselevka–Manoma complex in front of (on the ocean side) the Amur complex. The frontal part of the Amur complex and the Kiselevka–Manoma complex were emplaced synchronously with the western part of the East Sakhalin accretionary complex. This scenario defines the Early Cretaceous tectonic zonation of the region and the choice of the appropriate paleotectonic model. At the end of the Early Cretaceous, a single convergent boundary of the lithospheric plates is suggested with the position of the Sakhalin island arc system south of the Khingan–Okhotsk active continental margin.

In this paper, we focus on the geological features of volcanic edifices and the geochemistry of intermediate–basic volcanic rocks of Shaerbuti Mountain, which offer a new perspective on recycled materials in the study area. The Shaerbuti volcanic rocks consist of calc-alkali basalt and andesite formed in an arc setting. The porphyroclastic texture of basalt, explosive breccia rock, and the distribution of both breccia and agglomerate provide robust evidence that a volcanic edifice exists in Shaerbuti Mountain. Based on geochemical features, the Shaerbuti volcanic rocks have been identified as being of two types. Type I volcanic rocks have light rare earth element (LREE)-enriched patterns, with La/Sm ratios of 2.27–4.03, Th/Yb ratios of 0.50–1.46, and Nb/Yb ratios of 1.11–2.28. Type II volcanic rocks display a flat rare earth element (REE) pattern, with La/Sm ratios ranging from 1.83 to 2.43, Th/Yb ratios ranging from 0.24 to 0.45, and Nb/Yb ratios ranging from 0.87 to 0.93. In the studied rocks, MgO-Cr, MgO-Ni and MgO-CaO present a positive relationship, which indicates clinopyroxenes crystallized. The Sr-Nd-Pb isotopic compositions of these basalts present values of 0.7045 to 0.7063 ((87Sr/86Sr)i), 6.4 to 6.6 (εNd(t)), and 17.1300 to 18.3477 ((206Pb/204Pb)i), respectively. According to Sr-Nd-Pb isotope features, we argue that melts of altered oceanic crust and sediments were incorporated into the source. We also evaluate the water content (0.55%–6.72%) of the studied volcanic rocks.

Comparative data on tectono-stratigraphic complexes of the Ultra-Tamba terrane (Inner Zone of Japan) and upper structural level of the Samarka terrane in the Jurassic accretionary prism of Sikhote Alin are considered. Structural, lithological, petrographic data and age constraints characterizing rock associations of the terranes show that the latter are similar to a great extent, and consequently the Ultra-Tamba terrane can be regarded as an element of the Tamba-Mino-Ashio accretionary prism of the Jurassic but not Permian age, as it was thought earlier. The considered data substantiate confident structural correlation of both fragments of the Jurassic prism and of two regions in general.[PUBLICATION ABSTRACT]

The oceanic pelagic and hemipelagic siliceous and siliceous-clayey sediments play a subordinate role in the Amur Terrane, where they constitute thin tectonic slices separated by thicker terrigenous continental-margin deposits. The analysis of the radiolarian assemblages revealed the Middle-Late Jurassic age of hemipelagic siliceous mudstone and the Early Cretaceous age of similar continental-margin sediments. These new data contribute to the knowledge of the terrane's stratigraphy and demonstrate the progressively younger age of the stratigraphic boundaries between the different sedimentary facies in the southeastern direction. The multiple stacking of the oceanic and continental-margin sediments is characteristic of the accretionary complexes, and precisely such an interpretation of the tectonic nature of the Amur Terrane is consistent with its composition and position in the regional structure.