In this study, concentrations of organic biomarkers of core MD012404, recovered from central part of the Okinawa Trough, were analyzed, included of unsaturated alkenones and n-alkanes, for reconstructing paleoenviromental and paleoclimatic records for the past 100,000 years. The unsaturated alkenone index of Uk¡¬37 were calculated for reconstructing past variations of sea surface temperature (SST) in the East Chna Sea (ECS). Through the past 100,000 years, our record revealed that the varied pattern of paleo-SSTs of the ECS was mainly reflecting Interglacial/Glacial cycles. This result indicates that the enhanced East Asian winter monsoon which is induced by the changing orbital forcing is the dominant controlling factor to influence the hydrological conditions in the ECS. Otherwise, except of the warming event of Bølling-Allerød and cooling event of Younger Dryas, no obviously cooling trends were observed in the record indicating that the Uk¡¬37 based SST was not sensitive to the millennial-scaled climate events. This may be caused by the slow response of the SST to the millennial-sclaed events. The concentrations of unsaturated alkenones reconstructed in this study can represent to the surface productivity of the ECS. Our record shows that the values are higher in glacial period than in interglacial period. The higher productivity observed in glacial period may result from the wind-driven water mixing. Therefore, the well-mixing of surface and subsurface water thus can supply higher nutrients upto the surface water than induce the higher productivity in glacial period in the ECS. However, a more complicated pattern is found in MIS 5, the unsaturated alkenones have extremely high values in this interval which is different to the Holocene even though that the climatic conditions and global sea level are similar in these two periods. These high values may be caused by either higher surface production or well preservation, which results from the pool ventilation in the ECS. In addition, distributed pattern of n-alkanes can represent to the possible sources of organic materials and vegetation changes on land. Our record shows that n-C31 alkane is dominant in n-alkanes, and the distribution pattern of n-alkanes (C31 > C29 > C33 > C27 > C25 ) is similar to the sediments discovered on the continental shelf of ECS and the estuary of the Changjiang River and is different with the sediments from the Lanyang Hsi River. This fact indicates that the organic materials buried in sediments of the Okinawa Trough are mainly contribute from the ECS continental shelf and the Changjiang River is serves as the main contributor of terrestrial sediments in the study region. Our calculated Carbon preference index (CPI) indicates that terrigenous orangic matters are less influenced by degradation and diagenesis in glacial period, especially during LGM, and the changing pattern is highly correlated with the global sea level changes. Lower sea level observed in glacial period shorten the transporting distance of sediments from the Changjiang River to the Okinawa Trough thus causes more terrestrial inputs and deposits in the Okinawa Trough.

The purpose of this thesis is to describe the preliminary results from the investigation of shallow (<20m) hydrothermal vents with a total venting area of about 0.5 km2 off the eastern tip of Kueishantao Island. The chemical compositions of hot fluids, sediments and rocks as well as a continuous record of fluid temperature of a fumarole were measured in order to understand the venting process of hydrothermal fluids. The continuous temperature records show that the attainment of the maximum temperature of the hot fluids is related to the tidal cycle. The temperature variation seems to be associated with changes in the boiling point of seawater, which is affected by changes in water pressure. Such a correlation has not been reported in the literature. The hydrothermal fluids reach their highest temperature about 3.5 hours after each high tide, which is indicative of a shallow infiltration of seawater since the time it takes the boiling seawater to exit is so short. The hottest temperature recorded in our study area is 116¢J, while the lowest pH is 1.75, both a record in the world amid shallow hydrothermal systems. And, 1.75 is the lowest pH been reported on hydrothermal systems in the literature. At one point, the temperature recorder was covered with sand as a result of an encroaching typhoon. This suggests that the topography of the study area is susceptible to external forces. Based on salinity, the source of the hot fluids is taken to be ambient seawater, with no meteoric water from the islet involved. Concentrations of major ions in the hydrothermal fluids are almost the same as those in the ambient seawater. Mg is slightly enriched, however, which is unlike other hydrothermal fluids where, as reported elsewhere, Mg is generally lower because it replaces Ca in the bedrock. Low concentrations of Si in the studied fluids make for another distinct feature. Compared with other hydrothermal fluids in the world, the concentrations of Si in our study area are much lower, possibly on account of there being insufficient time for the rock to dissolve in the infiltrated seawater. Black and white smokers have widely been reported in the literature, but here are found heretofore unheard of yellow smokers as high as 6 meters. Other than one vent which emits liquid sulfur and forms a sulfur chimney, some vent sulfur from sulfur mounds. Still others are low- temperature vents which do not emit sulfur whatsoever. The most active venting activities are off the eastern tip of the islet. There are no other large reliefs associated with the hydrothermal activity, except for the chimney and a depression down to 35m deep. the chimney and a depression down to 35m deep. The composition of gravel on the seafloor is andesite, which is the same as the rock on the islet. The major composition of the sediments collected from the seafloor is sulfur, which is different from the sediments of the hydrothermal systems in the Okinawa Trough. The sulfur particles observed in this study originate from the fumaroles. Besides, sulfur balls the size of softballs and with distinct growth rings are found near some vents. The formation mechanism of these rings at this time, however, remains unclear. The bubbles from the vents are mostly made up of CO2, which is different from the composition of the shallow hot springs on the beach of Green islet. The 3He/4He of the emitted gas is high, this indicates that the gas may have originated from the mantle.

Abstract This study is to investigate the spatial and temporal variabilities of geochemical and carbon isotopic compositions of particles collected in the region off northeast Taiwan. Organic carbon isotopic compositions (d13Corg), total organic carbon content (TOC) and C/N ratio were determined in sediment particles collected at different water depths from three time-series sediment traps (at T12, T13, and T18 stations, respectively). The results showed abnormally high mass fluxes than those previously found. Generally they increase with water depths, implying both the transport from Lanyang-Hsi River and the resuspension from the seafloor. TOC contents range from 0.5 to 1.5wt% and decrease with depths. This can be attributed to changes in the surface productivity, lateral transport and organic preservation. The organic carbon isotopic compositions range between -21 and -25o/oo, which falls well within the d13Corg values of continental margin sediments. The lower d13Corg values at T12 station than those at T13 station can be attributed to the large terrestrial inputs. It is noted that d13Corg values decrease with depths, suggesting a significant contribution of the horizontal transport of particles to the settling process.

Abstract This study elucidates the processes that may determine the distributions of Mn and other trace metals on the slope of the southern Okinawa Trough. In addition to salinity and temperature, large-volume seawater samples were collected for analyzing dissolved manganese (DMn), particulate manganese (PMn), suspended, particulate organic carbon (POC), pH and dissolved CO2 (TCO2 ) during June-July of 1998, 1999 and 2000. Concentrations of DMn and PMn in a transect decrease generally seaward from the shelf break. However, anomalous distributions of DMn and PMn occur usually between 600 m and 900 m in many deep profiles. Such distribution patterns are probably influenced by the lateral transport of metals released from slope sediments or from the plumes of submarine venting systems. For example, dissolved manganese generally decreases with depth in the oxygenated condition, but in the study area unusual high DMn concentrations were observed commonly at depth 400 m, 600 m, 800 m and 1200 m. The unusual Mn signals become weak, in general, from the South Mien-Hua Canyon to the North Mien-Hua Canyon. The higher concentration of PMn sometimes was observed in deep stations than in shallow stations at the same depth implying that processes other than lateral transport may account for the distributions. Images obtained from EK-500 showed that submarine venting systems exist in anomalous Mn distribution areas. Anomalous distributions of PMn and Kd match DMn unusual distributions very well. Besides, the distribution of TSM is closely related to PMn distributions (R=0.433, p=0.01). Although the distribution of pH data appears to be normal, total alkalinity and total CO2 display anomalous distributions coincidently with those Mn unusual distributions. Meanwhile, the ratio (PMn/PAl) is higher for those unusual Mn distributions, and this is likely the effect of submarine venting.

In order to understand the source, transport pathway and sink of settling particulates in the sea off northeast Taiwan, three moorings with six sediment traps (about 100 m and 300 m above bottom) were deployed on the northern slope of the Ilan ridge (T17S and T18S) and in the South Okinawa trough (T19S). The mooring deployed at T17S was lost due to a connecting ring which was rusted and broken. The duration of the mooring was 6 months (late November, 1999 to early May, 2000) with sampling intervals at 15 days each. When the moorings were recovered, seawater samples were collected for filtration near each station and a box core at T19S was also taken so that the settling particulates, suspended particulates and bottom sediments can be compared for their characteristics. The results show that higher apparent mass fluxes were observed in January, February and early April, 2000 at T18S. The apparent mass fluxes vary between 11 and 91 g/m2/d at T18S, and between 6 and 22 g/m2/d at T19S. The time-series variations of the Pb-210 activity are between 46 and 76 dpm/g at T18S, and between 79 and 122 dpm/g at T19S, the values of which are much higher than those of T18S. The temporal Po-210 variations range between 18 and 90 dpm/g at T18S, and from 65 to 193 dpm/g at T19S. The Po-210 activity and its variation are greater at T19S than at T18S. The 210Po/210Pb activity ratios are less than unity at about 0.8 at T18S, and greater than unity at about 1.3 at T19S. The total Po-210 activity in all water columns varies between 0.2 and 16 dpm/100kg while the total Pb-210 activity varies between 28 and 43 dpm/100kg. The mean total 210Po/210Pb activity ratio is about 0.3, indicating that Po-210 was easily scavenged and removed from water columns by particulate matter. The box core taken at T19S has Po-210 activity ranging from 54 to 121 dpm/g and Pb-210 activity from 51 to 90 dpm/g. The 210Po/210Pb activity ratio is greater than unity in the upper 6 cm, indicating an excess of Po-210 activity. Below 6 cm Po-210 and Pb-210 are nearly at equilibrium. The 210Po/210Pb activity ratios in the water columns observed after the first deployments were higher than those observed after the second deployments. However, the 210Po/210Pb activity ratios of the settling particulates collected from the first trap deployments were lower than those from the second trap deployments. These changes might be attributed to earthquakes which occurred mainly before the second mooring period. These earthquakes could have caused a large quantity of terrigenous particulates with higher 210Po/210Pb activity ratio to be transported out to the study area in addition to resuspended shelf and slope sediments. These settling particulates, being enriched in organic matter with higher activity ratio, could preferentially scavenge Po-210 from the water column, resulting in much higher 210Po/210Pb activity ratios.

Abstract In order to understand the source, transport pathway and sink of settling particulates off northeast Taiwan, time-series sediment traps (PPS-3/3) were deployed on the north slope of Ilan ridge (T18) and in the Okinawa trough (T15 and T16) to collect settling particulates. The trapped particulate samples were determined for apparent mass flux (T18), particle size distribution, and contents of lithogenic portion, metals (Al, Mg, Ca, Fe, Mn, Cu), opal, OC (organic carbon) and IC (inorganic carbon). The results show that mass flux in winter is higher than in summer except for typhoon or rainstorm in summer which may cause high particulate flux. At mooring T11 and T17, only 2 cups had collected particulates but with rapid decrease, and the remaining cups were empty. It is not clear whether Kuroshio plays a role and further investigation is needed. The trapped particulates were mainly clay and silt in the north slope of Ilan ridge and south Okinawa trough, and were sand and silt in the Mien-Hwa canyon. The portion of coarse silt and larger particles (>31 mm) decreases with an increase of distance from the land (from T11 to T18). The grain size distribution of particulate at T18 is similar to that at T15 and T16, but the mass flux in the north slope of Ilan ridge is an order of magnitude higher than in the south Okinawa trough. The size distribution pattern below 600m water depth is very similar at both T15 and T16, but the coarse fraction (> 31 mm) is more at the upper than lower traps, presumably due to lateral transport. The Mn content of the trapped particulates in the south Okinawa trough is twice as hign as that in the north slope of Ilan ridge. High Mn/Al ratio in the trough suggests that Mn is supplied by hydrothermal activities. Lithogenic portions occupy about 84~88.5% at T18, T16 and T15. Relative to other marginal seas biogenic contributions are clearly lower.

Abstract The research was conducted as a part of the phase III of the KEEP(Kuroshio Edge Exchange Processes)program. Two strings of sediment traps were deployed simultaneously: one near the outlet of North Mien-Hua Canyon (T15), and the other at the south rim of the South Okinawa Trough (T16). The purposes are to collect settling particulates at various depths for the studies of temporal and spatial variations of the particulate flux, 210Pb activity, 210Pb flux and size distribution. The particulate fluxes showed synchronous variations among the traps deployed at different depths of the same site. In general, the particulate flux in the marginal sea areas increases with depth but the maximum values may be at the mid-depth rather than at the deepest trap and remain so for the entire mooring period as observed at T15 and T16. Unusually high particulate fluxes could occur within the same period, probably reflecting an episodic event, such as typhoon or rain storm. 210Pb activity measured from different depths at T15 and T16 increases generally with depth along with the increase of the particulate flux toward the bottom. The temporal variation of 210Pb activity is generally smaller than that of the particulate flux in terms of relative amplitude. At the outlet of the canyon, T15, the temporal mean particulate flux of each trap ranged from 0.16 to 3.3 g/m2/d(a factor of ~ 20), while the mean 210Pb activity of each trap varied from about 98 to 168 dpm/g. At T16 located at the south rim of the South Okinawa Trough, the temporal mean particulate flux ranged from 0.06 to 5.7 g/m2/d(a factor of ~ 100), while the mean 210Pb activity varied from 82 to 192 dpm/g. The particulate 210Pb flux was smaller at T15 than at T16 because T15 has smaller particulate flux. The trapped particulates in the canyon(T1-T3) are mostly silt and sand, while the particulates collected from the Okinawa Trough(T15, T16) are mainly silt and clay. The 210Pb activity of the former is much lower than that of the latter, indicating the enrichment of 210Pb on the fine particulates. As the fine-grained particulates away from landmass have longer residence time in the ambient water, they can scavenge 210Pb more effectively.