Oceanic strike-slip faults represent active fluid conduits in the abyssal sub-seafloor

We present pore-fluid geochemistry and heat-flow data along the SWIM1 fault in the Horseshoe Abyssal Plain (northeastern Atlantic Ocean). The SWIM1 fault is part of the transcurrent plate boundary between Africa and Eurasia and cuts through as much as 5-km-thick sediments overlying >140 Ma oceanic lithosphere. In a number of places, restraining segments (as long as 15 km) of the SWIM1 fault generate anticlines (positive flower structures) that protrude as ~100-m-high hills above the abyssal plain. Heat flow and gradients of dissolved constituents in pore water are enhanced at these seafloor highs. Transport-reaction modeling confirms that slow advection of deep-seated fluids, depleted in Mg and enriched in Sr and CH4, can explain the observations. The geochemical signature is similar to the one observed at deep-sea mud volcanoes located eastward on the SWIM1 fault. The upward-migrating fluids have interacted with carbonate rocks at maximum 5 km depth, which represent the oldest sedimentary unit on top of the basement. We argue that deep-rooted fluids can generally be mobilized and transported upward along flower structures that formed in restraining-bend segments of long strike-slip faults. Such tectonic settings represent largely unrecognized corridors for mass exchange between lithosphere and ocean.

A Synthesized Study of the Spatiotemporal Evolution of Central Yellow Sea Mud Depositional Processes During the Holocene

The spatial distribution patterns of central Yellow Sea Mud (CYSM) thicknesses and their temporal evolution during the Holocene are here updated using data from 10 new cores, in combination with the previously-published data for 64 cores from this area. Of these 74 cores, 15 exhibit clear AMS 14C dating constraints. Three subareas of mud deposition can be delineated using analyses of spatiotemporal mud thickness distributions and the variations between these. A depocenter subarea, with mud thicknesses >4 m, lies in the northwestern part of the CYSM; the mean sedimentation rate (SR) is relatively high in this subarea, with two high SR stages occurring at ∼6.1–5.4 ka and ∼4–2.5 ka. An adjacent subarea surrounds the depocenter subarea; this subarea has mud thicknesses between 2 and 4 m, and a high mid-Holocene SR which evinces a gradually decreasing trend after 5 ka. A distal periphery subarea lies in the eastern part of the CYSM, with mud thicknesses between 0.5 and −2 m, and a low mean SR that has been generally stable over the last 7 ka. Our results indicate that both sedimentary sources and hydrological dynamics played important roles in the formation of CYSM. The Yellow River may be the principal sedimentary source for CYSM, as mud thickness decreases gradually from northwest to southeast. Different mud subareas appear to be affected by different hydrological dynamics: in the depocenter subarea, oceanic current fronts seem to play an important role in mud deposition, while in the adjacent subarea and the distal periphery subarea, weak tidal currents appear to be the dominant depositional control. The generally decreasing trend in the SR of the adjacent subarea indicate that the East Asian winter monsoon (EAWM) potentially controlled changes in CYSM sedimentary sources after 7 ka.

Mathematical model of a non-stationary process of accumulation of gas hydrates, confined to deep-water mud volcanoes

<p>Large amounts of methane hydrate locked up within marine sediments are associated to mud volcanoes. We have investigated by means of mathematical modeling the unsteady process of accumulation of gas hydrates associated with the processes of mud volcanism. A mathematical model has been developed. The system of equations of the model describes the interrelated processes of filtration of gas-saturated fluid, thermal regime and pressure, and accumulation of gas hydrates in the seabed in the zone of thermobaric stability of gas hydrates. The numerical simulation of the accumulation of gas hydrates in the seabed in the deep structures of underwater mud volcanoes has been carried out using the realistic physical parameters values. The influence of the depth of the feeding reservoir and the pressure in it on the evolution of gas hydrate accumulations associated with deep-sea mud volcanoes is quantitatively analyzed. Modeling quantitatively showed that the hydrate saturation in the zones of underwater mud volcanoes is variable and its evolution depends on the geophysical properties of the bottom environment (temperature gradient, porosity, permeability, physical properties of sediments) and the depth of the mud reservoir and pressure in it. The volume of accumulated gas hydrates depends on the duration of the non-stationary process of accumulation between eruptions of a mud volcano. The rate of hydrate accumulation is tens and hundreds times the rate of hydrate accumulation in sedimentary basins of passive continental margins.</p>

Ecological Engineering and Restoration of Eroded Muddy Coasts in South East Asia: Knowledge Gaps and Recommendations

Ecological engineering (EE) was employed for developing strategies for stabilizing eroded muddy coasts (EMCs). However, there was a limited analysis of these EE strategies with respect to design, performance, and lessons learned. This study employed a critical review for addressing the limitations. There were four EE models designed with different restoration interventions for stabilizing EMCs. The models using active interventions have not been cost-effective in controlling erosion because the interventions failed to achieve their goals or were costly and unnecessary. Of the two passive intervention models, the one with structures constructed from onshore proved to be more cost-effective in terms of construction costs, the survival rate of transplanted seedlings, and levels of sea mud accumulation. Interventions with adequate consideration of the muddy coastal ecological processes and the ecological reasoning for the positioning of these interventions play a crucial role in stabilizing EMCs. A passive restoration model using gradually expanded interventions should be promoted in order to ensure sustainable management of EMCs in the future.

Fungal Community and Biodeterioration Analysis of Hull Wood and Its Storage Environment of the Nanhai No. 1 Shipwreck

The Nanhai No. 1 shipwreck is a Chinese merchant ship in the Southern Song Dynasty, and now it is stored in a huge enclosed glass warehouse in Maritime Silk Road Museum in Guangdong Province. At present, the hull of the Nanhai No. 1 shipwreck is still being excavated, and a small part of the hull wood is soaked in a specific solution to desalt. Through long-term exploration, we found that the above two states of hull wood had undergone biodeterioration, so the purpose of this study is to analyze the fungal community of exposed and soaked wood from the Nanhai No. 1 shipwreck. We sampled 10 exposed hull wood and sea mud samples, two wood storage water samples, and air samples in the glass warehouse. We used scanning electron microscope and optical microscope to find that there were obvious fungal structures in exposed wood and wood storing water samples. High-throughput sequencing of fungi revealed that the most abundant genera in exposed and soaked wood were Fusarium sp., and Scedosporium sp., respectively. In addition, Fusarium solani and Scedosporium apiospermum were successfully isolated from the hull wood surface and wood storing water samples, and the degradation tests of lignin and cellulose, the sensitivity tests of biocides and growth curve assay were carried out. We also found that Penicillium sp. and Cladosporium sp. are the most abundant in the glass warehouse air. Our research results show that F. solani and S. apiospermum should be regarded as a major threat to the preservation of the Nanhai No. 1 shipwreck. These results provide a reference for our protection of shipwrecks and other similar artifacts.