Characteristics and provenance implication of detrital minerals since Marine Isotope Stage 3 in Core SYS-0701 in the western South Huanghai Sea

The previous studies of the sedimentology and chronology of sediment core SYS-0701, which was recovered from the western South Huanghai Sea （Yellow Sea）, have revealed the changes in the sea-level and sedimen- tary evolution during the late Quaternary in the region. The present study used mineralogical data from the section of the core deposited since Marine Isotope Stage （MIS） 3, to decipher the provenance of sediments of the paleo-delta deposited during MIS 3 and MIS 1. Based on the lithologic features and the variations with depth of the concentrations of carbonates and both heavy and light minerals in bulk samples, the up- per part of Core SYS-0701 can be divided into three units designated DU1, DU4, and DU5, in accord with previouslyused terminology. Sub-units of units DU1 （DU1-1 and DU1-2） and DU4 （DU4-1 and DU4-2） have also been identified. DU1 was deposited during MIS 1, and DIJ4 and DU 5 were formed during MIS 3. All data pertaining to dominant heavy mineral assemblages, diagnostic minerals, ratios of diagnostic minerals, light mineral associations, textural maturities, and carbonate contents, indicate that the sediments of Core SYS-0701 are comparable with Huanghe River （Yellow River） sediments. Moreover, the mineralogy of the sediment evidenced its dependence on supply rates and hydrodynamic conditions. Weak hydrodynamics （DU5 and DU4-2） and/or low sediment supply （DU1-2） led to sediment containing less hornblende and epidote, with a large specific gravity and high content of flaky minerals, and vice versa in cases of strong hydrodynamics （DIJ4-1） and very large sediment supply （DUI-1）.

Biomarker assessments of sources and environmental implications of organic matter in sediments from potential cold seep areas of the northeastern South China Sea

Multi-biomarker indexes were analyzed for two piston cores from potential cold seep areas of the South China Sea off southwestern Taiwan. Total organic carbon（TOC） normalized terrestrial（n-alkanes） and marine（brassicasterol, dinosterol, alkenones and iso-GDGTs） biomarker contents and ratios（TMBR, 1/Pmar-aq, BIT） were used to evaluate the contributions of terrestrial and marine organic matter（TOM and MOM respectively） to the sedimentary organic matter, indicating that MOM dominated the organic sources in Core MD052911 and the sedimentary organic matter in Core ORI-_（86）0-22 was mainly derived from terrestrial inputs, and different morphologies were the likely reason for TOM percentage differences. BIT results suggested that river-transported terrestrial soil organic matter was not a major source of TOM of sedimentary organic matter around these settings.Diagnostic biomarkers for methane-oxidizing archaea（MOA） were only detected in one sample at 172 cm depth of Core ORI-_（86）0-22, with abnormally high iso-GDGTs content and Methane Index（MI） value（0.94）. These results indicated high anaerobic oxidation of methane（AOM） activities at or around 172 cm in Core ORI-_（86）0-22.However in Core MD052911, MOA biomarkers were not detected and MI values were lower（0.19–0.38）, indicated insignificant contributions of iso-GDGTs from methanotrophic archaea and the absence of significant AOM activities. Biomarker results thus indicated that the discontinuous upward methane seepage and insufficient methane flux could not induce high AOM activities in our sampling sites. In addition, the different patterns of TEX_（86） and U_（37）^（K′） temperature in two cores suggested that AOM activities affected TEX_（86）37 temperature estimates with lower values in Core ORI-_（86）0-22, but not significantly on TEX_（86） temperature estimates in Core MD052911.

Evaluation of Natural Radioactivity in Marine Sand Deposits from Offshore China

Natural radioactivity is very important for the assessment of the marine sand property and usability. By using gamma spectrometry, the concentration of the natural radionuclides 226Ra, 232Th and 40K have been measured in marine sand deposits from Liaodong Bay (LDB), North Yellow Sea (NYS), Zhoushan area (ZS), Taiwan Shoal (TS) and Pearl River Mouth (PR), offshore China, which are potential marine sand mining areas. The radiation activity equivalent (Raeq), indoor gamma absorbed dose rate (DR), annual effective dose (HR), alpha index (Ia), gamma index (Ig), external radiation hazard index (Hex), internal radiation hazard index (Hin), representative level index (RLI), excess lifetime cancer risk (ELCR) and annual gonadal dose equivalent (AGDE) associated with the natural radionuclides are calculated to assess the radiation hazard of the natural radioactivity in the marine sands offshore China. From the analysis, it is found that these marine sands are safe for the constructions. The Pearson correlation coefficient reveals that the 226Ra distribution in the marine sands offshore China is controlled by the variation of the 40K concentration. Principal component analysis (PCA) yields a two-component representation of the entire data from the marine sands, wherein 98.22% of the total variance is explained. Our results provide good baseline data to expand the database of radioactivity of building materials in China and all over the world.

Effects of Nitrogen Addition on Plant Functional Traits in Freshwater Wetland of Sanjiang Plain,Northeast China

To clarify the responses of plant functional traits to nitrogen(N) enrichment, we investigated the whole-plant traits(plant height and aboveground biomass), leaf morphological(specific leaf area(SLA) and leaf dry mass content(LDMC)) and chemical traits(leaf N concentration(LNC) and leaf phosphorus(P) concentration(LPC)) of Deyeuxia angustifolia and Glyceria spiculosa following seven consecutive years of N addition at four rates(0 g N/(m2·yr), 6 g N/(m2·yr), 12 g N/(m2·yr) and 24 g N/(m2·yr)) in a freshwater marsh in the Sanjiang Plain, Northeast China. The results showed that, for both D. angustifolia and G. spiculosa, N addition generally increased plant height, leaf, stem and total aboveground biomass, but did not cause changes in SLA and LDMC. Moreover, increased N availability caused an increase in LNC, and did not affect LPC. Thus, N addition decreased leaf C∶N ratio, but caused an increase in leaf N∶P ratio, and did not affect leaf C∶P ratio. Our results suggest that, in the mid-term, elevated N loading does not alter leaf morphological traits, but causes substantial changes in whole-plant traits and leaf chemical traits in temperate freshwater wetlands. These may help to better understand the effects of N enrichment on plant functional traits and thus ecosystem structure and functioning in freshwater wetlands.

Characteristics of Meso-Cenozoic Igneous Complexes in the South Yellow Sea Basin,Lower Yangtze Craton of Eastern China and the Tectonic Setting

The South Yellow Sea Basin is partially surrounded by the East Asian continental Meso- Cenozoic widespread igneous rocks belt. Magnetic anomaly and multi-channel seismic data both reveal the prevalent occurrence of igneous rocks. We preliminarily defined the coupling relation between magnetic anomalies and igneous rock bodies. Some igneous complexes were also recognized by using multi-channel seismic and drilling data. We identified various intrusive and extrusive igneous rock bodies, such as stocks, sills, dikes, laccoliths and volcanic edifice relics through seismic facies analysis. We also forecasted the distribution characteristics of igneous complexes. More than fifty hypabyssal intrusions and volcanic relics were delineated based on the interpretation of magnetic anomaly and dense intersecting multi-channel seismic data. It is an important supplement to regional geology and basin evolution research. Spatial matching relations between igneous rock belts and fractures document that extensional N-E and N-NE-trending deep fractures may be effective pathways for magma intrusion. These fractures formed under the influence of regional extension during the Meso- Cenozoic after the Indosinian movement. Isotopic ages and crosscutting relations between igneous rock bodies and the surrounding bedded sedimentary strata both indicate that igneous activities might have initiated during the Late Jurassic, peaked in the Early Cretaceous, gradually weakened in the Late Cretaceous, and continued until the Miocene. Combined with previous studies, it is considered that the Meso-Cenozoic igneous activities, especially the intensive igneous activity of the Early Cretaceous, are closely associated with the subduction of the Paleo-Pacific Plate.

Distribution and Provenance of Detrital Minerals in Southern Coast of Shandong Peninsula

Detrital minerals of 137 offshore and 22 river sediment samples collected from Qingdao coastal areas have been analyzed. Four mineral assemblage provinces can be classified by Q-mode cluster analysis. Factor analysis identifies two major factors that account for the total variability in most common minerals: 1) based on the relationship of quartz, hornblende, actinolite, micas, and authigenic pyrite, 41.55% of the variability is related to sediment sources; 2) based on the relationship of epidote, garnet, sphere, and ilmenite, 23.21% can be related to strong hydrodynamic conditions that control transport and sedimentation. By comparing mineral compositions of river waters in the study area, the following four mineral provenances can be identified. The Qingdao-Laoshan nearshore area has a quartz-feldspar-epidote-hornblende-limenite-limonite-sphene assemblage, which is largely attributed to relict sediment and coastal erosion. The Jimo-Haiyang nearshore area has a quartz-feldspar-hornblende-epidote-limonite-mica-actinolite assemblage, derived largely from the Wulong River and Rushan River, and is also affected by the Huanghe River, while the Qianliyan Island area in the deeper offshore area separated by a mud belt has a similar assemblage. The Haiyang-Rushan nearshore area has a quartz-feldspar-hornblende-epidote-micas-limonite assemblage, indicating multiple sources from the Rushan River, the Wulong River, the Huanghe River, and coastal erosion. The central area, located in an eddy center, has a mica-authigenic pyrite-hornblende-quartz-feldspar assemblage, indicating multiple sources dominated by Huanghe River distal sediments.

Sedimentary facies and evolution of aeolianites on Shidao Island,Xisha Islands

The aeolianite deposits on Shidao Island of the Xisha Islands,the South China Sea,contain five stages of aeolian biocalcarenites and four paleosols.The aeolian biocalcarenites consist of two sedimentary facies:dune and interdune deposits.In the dunes,large-scale festoon cross-bedding,humped cross-bedding and high-angle foreset bedding are well developed,and in the interdunes,large-scale flat-bedding and low-angle wedge shaped cross-bedding are well developed.The sedimentary structures and lamella features indicate that the aeolian deposits are driven mainly by the northeast monsoon.The aeolian biocalcarenite and paleosols may reflect the arid and humid climates of the East Asian monsoon,respectively.By comparison with the stalagmite oxygen isotope climosequence of Hulu Cave,Nanjing,we inferred that the aeolianite formed in the last glacial stage,and the paleosols were formed during relatively long-term warm events.

The reverse sediment transport trend between abandoned Huanghe River(Yellow River) Delta and radial sand ridges along Jiangsu coastline of China——an evidence from grain size analysis

To reveal the sediment transporting mechanism between the abandoned Huanghe River （Yellow River） Delta and radial sand ridges, “End Member” Model and grain size trend analysis have been employed to separate the “dynamic populations” in the surficial sediment particle spectra and to determine the possible sediment transporting pathway. The results reveal four “dynamic subpopulations”（EM1 to EM4） and two reverse sediment transporting directions： a northward transport tend from the radial sand ridges to mud patch, and a southward transport trend in deep water area outside the mud patch. Combined with the published hydrodynamic information, the transporting mechanism of dynamic populations has been discussed, and the main conclusion is that the transporting of finer subpopulations EM1 and EM2 is controlled by the “anticlockwise residual current circulation” forming during tidal cycle, which favor a northward transporting trend and the forming of mud patch on the north of radial sand ridges, while the transporting of coarser EM3 is mainly controlled by wind driven drift in winter, which favors a southward transporting direction.

Numerical Study on Seasonal Transportation of the Suspended Sediments in the Modern Yellow River Mouth Effected by the Artificial Water and Sediment Regulation

Since 2002, an artificial water and sediment regulation(AWSR) has been carried out, which largely reduced water and sediment discharged from the Yellow River into the Bohai Sea. Although the sediment transport in the Yellow River Mouth(YRM) has been observed and modeled intensively since AWSR, but preferentially for the non-storm conditions. In this study, a three-dimensional current-wave-sediment coupled model, DHI-MIKE numerical model, was used to examine the seasonal suspended-sediment transport in the YRM after the AWSR. Results show that the seasonal distribution of suspended-sediments in the YRM is dominated by wind and wave rather than river input. The major transport pathway of suspended-sediments is from the western Laizhou Bay to the Bohai Strait during the winter monsoon, especially in storm events. In addition, about 66% of the river sediments deposit within 30 km of the YRM, which is smaller than previous estimations. It suggests that the YRM has been eroded in recent decades.

The Mesozoic Basin-Mountain Coupling Process of the Southern East China Sea Shelf Basin and its Adjacent Land Area

Basin-mountain coupling is a key issue for basin formation and evolution. The analysis of basin-mountain coupling process, as well as quantitative or semiquantitative restoration of prototype basin and the evolution of continental margin, can be used to interpret the geological process of basin-range conversion and reconstruct early prototype basins, which is a difficult and leadin~ scientific oroblem of basin research.

Stability of submarine slopes in the northern South China Sea: a numerical approach

Submarine landslides occur frequently on most continental margins. They are effective mechanisms of sediment transfer but also a geological hazard to seafloor installations. In this paper, submarine slope stability is evaluated using a 2D limit equilibrium method. Considerations of slope, sediment, and triggering force on the factor of safety (FOS) were calculated in drained and undrained (Φ=0) cases. Results show that submarine slopes are stable when the slope is <16° under static conditions and without a weak interlayer. With a weak interlayer, slopes are stable at <18° in the drained case and at <9° in the undrained case. Earthquake loading can drastically reduce the shear strength of sediment with increased pore water pressure. The slope became unstable at >13° with earthquake peak ground acceleration (PGA) of 0.5 g; whereas with a weak layer, a PGA of 0.2 g could trigger instability at slopes >10°, and >3° for PGA of 0.5 g. The northern slope of the South China Sea is geomorphologically stable under static conditions. However, because of the possibility of high PGA at the eastern margin of the South China Sea, submarine slides are likely on the Taiwan Bank slope and eastern part of the Dongsha slope. Therefore, submarine slides recognized in seismic profiles on the Taiwan Bank slope would be triggered by an earthquake, the most important factor for triggering submarine slides on the northern slope of the South China Sea. Considering the distribution of PGA, we consider the northern slope of the South China Sea to be stable, excluding the Taiwan Bank slope, which is tectonically active.

Revision of P-wave Velocity and Thickness of Hydrate Layer in Shenhu Area, South China Sea

To revise P-wave velocity and thickness of the hydrate layer in the Shenhu area of the South China Sea, acoustic and resistivity logging curves are reanalyzed. The waterlogging phenomenon is found in the shallow sediments of five drilling wells, which causes P-wave velocity to approximate the propagation velocity of sea water(about 1500 m s-1). This also affects the identification of the hydrate layer and results in the underestimate of its thickness. In addition, because there could be about a 5 m thick velocity ramp above or below the hydrate layer as interpreted by acoustic and resistivity logging curves, the recalibrated thickness of this layer is less than the original estimated thickness. The recalibrated P-wave velocity of the hydrate layer is also higher than the original estimated velocity. For the drilling well with a relatively thin hydrate layer, the velocity ramp plays a more important role in identifying and determining the thickness of the layer.

Paleo-Fluvial Systems during Marine Isotope Stages 6, 4 and 2 in the North Yellow Sea

Objective During the sea-level lowstands of the Late Quatemary, paleo-channels resulting from large-scale glacial regressions were extensively developed on continental shelves worldwide. Great attention has been paid to the mechanisms and ages of these successions of fluvial incisions, which provide insight into the sedimentary evolution and processes of shelves.

Historical records and the sources of polycyclic aromatic hydrocarbons in the East China Sea

The coastal cities are the most advanced regions in China.In the past few decades,the environment changed very significantly due to large scale human activities in the coastal regions.Polycyclic aromatic hydrocarbons (PAHs)in three dated sediment cores from the west coast of the Yellow Sea (core A01),the Yangtze River estuary (YRE;core A02)and the Oujiang River estuary (ORE;core A03)were analyzed to reconstruct the environmental evolutionary process of the east China coastal region over the past century. In the three cores,PAHs concentrations were increased rapidly.Lower concentrations of PAHs were measured in core A02 than in cores A01 and A03.The vertical variation of PAHs in the YRE Was dominated by the petrogenic sources.Historical records of PAHs in the ORE were controlled by pyrolytic sources.PAHs on the west coast of the Yellow Sea were contributed by the two sources.

Provenance analysis of surface sediments in the Holocene mud area of the southern coastal waters off Shandong Peninsula,China

The sedimentary record of mud areas is an important carrier of information on the Holocene evolution of marine environments. Based on fine interpretations of the shallow stratigraphic section data, a small mud deposit area has been found in the southern coastal waters off Shandong Peninsula. This mud area is mainly distributed in coastal waters north of Laoshantou to the vicinity of Rushan Estuary. Overall, it is parallel to the coastline and spreads in a banded pattern, gradually thinning from offshore to the sea. The isopach map of depth distribution is parallel with the shoreline, and the depocenter lies in coastal waters of the Aoshan Bay where the maximum thickness is up to 22.5 m. Accelerator mass spectrometry（AMS） ^（14）C dating shows that the mud area was formed in the Holocene. The test data of surface sediments from the mud area, including particle size, mineral characteristics, and rare earth element contents, are used in comparisons with the composition of materials from the major surrounding medium and small rivers flowing into the sea and the Huanghe（Yellow） River. In this paper, the sedimentary characteristics and provenance of the mud deposit area are discussed. The results show that the formation of this mud area resulted from the joint action of the Huanghe River and surrounding rivers flowing into the sea.

Morphology and internal architecture of a banner bank off Chengshan Headland, Shandong Peninsula

A banner bank off the north coast of the Chengshan Headland, Shandong Peninsula, has been described on the basis of echo sounder bathymetry, side-scan sonar and high-resolution seismic data sets. The bank is in NWW direction, approximately parallel to the coastline. The bank consists of sandy silt or clayed silt. Sand waves and megaripples are observed on the north side, which result from strong tidal currents around the headland and storm waves in winter. These bed forms indicate that the bank is influenced by the modern hydrodynamics. The bank is separated from the coast and Holocene subaqueous clinoform around the Shandong Peninsula in its east part. High-resolution seismic profiles reveal that the bank was formed during two periods： the earlier seismic unit Ua, and later seismic units Ub and Uc which overlays Ua with erosional surfaces on its south side and north side, respectively. As comparing with the clinoform, the bank has a different internal architecture. In the west of the bank, however, topography and surface sediment characteristics suggest that the bank links to the clinoform. The authors propose that seismic Ua is a residual part of early clinoform deposit. After the sediments in the north and south of Ua were eroded by strong currents, the Ub and Uc started to deposit probably by a complex hydrodynamic process. These results provide new insights into the evolution of the bank and its relation with the Holocene subqueous clinoform.

Heavy Minerals in Shelf Sediments off Fujian-Zhejiang Coast of the East China Sea: Their Provenance and Geological Application

To examine the composition and source variations of heavy minerals in the Fujian-Zhejiang mud belt(FZMB) over the past few hundred years, heavy minerals in 150 surficial sediment samples and two sediments cores collected from the southern FZMB were identified and analyzed. The results show that the mineral assemblage of hornblende-magnetite-epidote-chlorite is dominant in the study area. Based on the heavy mineral contents, the study area is divided into two mineral zones, namely a near-shore muddy sediment zone(zone Ⅰ) and an offshore mixed sediment zone(zone Ⅱ). The sediments from zone Ⅰ contains relatively abundant metallic minerals with proximal sediments from the Oujiang River and the Minjiang River as the primary component. The sediment from zone Ⅱ has relatively low content for minerals from the near-shore materials and is significantly affected by the Oujiang River sediments, and by the flaky minerals from the Yangtze River to a certain extent. The characteristics of heavy minerals in the cores may be affected by a variety of factors. Before the 20th century, under the influence of strong East Asian winter monsoon(EAWM), the sandy sediment in FZMB is significantly affected by the Oujiang River and the Yangtze River sediments, and relatively unaffected by near-shore terrigenous matter. In the 20th century, as the intensity of the Zhejiang-Fujian Coastal Current(ZFCC) decreased, the influence of the Minjiang coastal sand enhanced. Since the 1980s, as the collective effect of relatively weak EAWM and frequent storm surges and typhoons, the impact of the Minjiang River sediments on the FZMB sediments has increased considerably.

Study on the Submarine Slope Stability of the Deep Channel in the Caofeidian Harbor

Objective The greatest advantage of the Caofeidian Harbor is its deep channel facing the Bohai Bay. The deep channel is a natural port hub for shipping of the Caofeidian Habor. The construction of the Caofeidian Harbor has impacted the hydrodynamic environment and the sediments movement, which has attracted much attention about the geomorphic evolution, slope stability and the evolution trend after submarine slope destruction. Insight from this study might be significant for the future development of the Caofeidian Habor, including planning, operation and maintenance.

A Holocene Yalu River-derived fine-grained deposit in the southeast coastal area of the Liaodong Peninsula

High-resolution seismic profiles and surface samples were studied in detail in order to determine the structures, provenance, and dynamic mechanisms of a fine-grained deposit in the southeast coastal area of the Liaodong Peninsula, China. Results indicate that there is a prominent fine-grained deposit distributed alongshore up to 14 m thick, which thins out to less than 2 m in both seaward and landward directions, forming an Ω-shaped pattern of cross-section. The deposit is 180-300 km away from the Yalu River mouth and extends along the southeast coast of the Liaodong Peninsula between the northeast of Dalian Bay and southwest of the Changshan Islands, in water depths of 20-40 m. The deposit, which is mainly derived from the Yalu River, represents a Holocene Highstand System Tract sequence formed since the highest sea level around 7.0 ka. The Yalu River-derived sediments were redeposited in the area off the southeast coast of the Liaodong Peninsula after resuspension and transportation by the Liaonan Coastal Current.

Stratigraphy of late Quaternary deposits in the mid-western North Yellow Sea

The North Yellow Sea(NYS) is characterized by strong land-sea interaction and paleoenvironmental changes with sea-level fluctuations during the late Quaternary. However, large-time scale depositional stratigraphy in this area and its relationship with sea-level changes remain unresolved. Highresolution seismic profiles from NYS were subdivided into eleven seismic units(U1 to U11 in descending order). A 70.6-m-long borehole(DLC70-2) from localities on seismic profiles, analyzed for lithology, microfossil assemblages and geochronology, comprises eleven sedimentary units(D1 to D11 in descending order), which were clearly correlated with the eleven seismic units. These units constitute four distinctive sequences(SQ1 to SQ4 from top to bottom) bounded by three sequence boundaries(S3, S5 and S10) with obvious depositional hiatus, correlated with sea-level lowstands of MIS2, MIS4 and MIS6, respectively. The lowermost SQ4 below S10, has been identified only upper part of transgressive systems tract(TST)(D11, tidal flat facies in early MIS6). SQ3 overlying S10 consists of a set of lowstand systems tracts(LST)(D10, fluvial to incised-channel filling facies in late MIS6), TST and highstand systems tracts(HST)(D9 to D6, interactive deposits of neritic and littoral facies in MIS5 and early MIS4). SQ2 above S5 is composed of LST(D5, channel-filling facies in late MIS4) and TST(D4, littoral to estuary facies in early-middle MIS3), but lack of HST resulting from subaerial exposure and channel incising during the Last Glacial Maximum(LGM). The uppermost SQ1 overlying S3 comprises LST(D3, channel-filling to flooding plain or marsh facies in MIS2), Holocene TST(D2, littoral and tidal sand ridge facies) and HST(D1, neritic facies). The unusual depositional stratigraphy was largely dominated by sea-level fluctuations and the Bohai Strait topography. This study confirms that TSTs are relative continuous and widely distributed, while LSTs vary considerably in thickness and lateral extent since MIS6 in NYS.