Chu Feng-you

Molecular organic geochemical records of the ANT28-D5-06 sediment core in the Weddell Sea of West Antarctica and their petroleum geology significance

The chromatography - mass spectrometry of soluble extracts from organic sediment source ANT28-D5-06 in the Weddell Sea of West Antarctica allows investigations on molecular biomarkers (n-alkanes, isoprenoid, serroid terpane), organic carbon and isotope, forming environment, organic maturity, hydrocarbon-generation potential and hydrocarbon migration of this core sediment. The results show that, n-alkanes show a unimodal distribution, with peak carbons of nC₁₆, nC₁₇ and nC₁₈, and weak high-carbon peak group; the organic matter type is sapropel, with (ΣC₂₁*/ΣC₂₂⁺) and (C₂₁+C₂₂)/(C₂₈+C₂₉) ratios greater than 1.0, indicative of the derivation of organic matter chiefly from a marine environment; the organic sediment is abundant with tricyclic terpanes and pentacyclic triterpane, with a high content of gammacerane and a distribution dominance of C₂₉ sterol and C₂₇ sterol, further suggesting the organic matter is dominated by input of lower organisms; isotopes of organic carbon (δ¹³C) lie between -25.30⁰/₀₀ and -25.91⁰/₀₀, implying a characteristic of marine aquatic organisms; Pr/Ph ratios range from 0.41 to 0.97, indicating a strong reducing environment; organic carbon in 2cm-11cm of the site ANT28-D5-06 is greater than 1.5; C₂₉ααα20S/C₂₉ααα(20S+20R) ratios are mostly between 0.32 and 0.48; C₂₉αββ/C₂₉(ααα+αββ) ratios lie in a range of 0.31-0.54; C₃₂22S/C₃₂(22S+22R) ratios range from 0.56 to 0.62; Ts/(Tm+Ts) ratios lie between 0.33 and 0.51; all these indices for discrimination of mature oil illustrate that, the organic sediment ANT28-D5-06 has an overall high maturity, close to high-quality organic sediment source, possessing favorable hydrocarbon-generation conditions, and some organic sediment source horizons have reached hydrocarbon-generation peak, which indicate a great prospecting potential for the Weddell basin.

Vegetation and climate change inferred from two marine pollen records in the west Pacific during the Holocene

The palynological analysis of two marine core, MD06-3075 (6.4762°N, 125.8322°E; 1878 m water depth, 30.76 m in length) in the southern Philippines and MD98-2178 (3.6200°N, 118.7000°E; 1984 m water depth, 35.6 m in length) in the northwest Celebes Sea, the detailed oxygen isotope records, and other marine pollen records in the west Pacific, provide the regional vegetation and climate history during the Holocene. The record shows that, during the early Holocene, ~10.0-6 kyr B.P., the pollen percentage of the tropical montane forest decline, suggestting that the tropical montane forest distribute at the high altitude just like nowdays, which indicates a warm condition. The pollen from mangrove group is abundant, presenting the well-development of the mangrove along the coast of the adjacent islands. Meanwhile, the pollen from the herb is rare, but the value of the pteridophyte is much high, indicating a wet condition. During the mid-Holocene, the pollen percentage of the tropical mid-upper montane rainforest is very high at 6-5 kyr B.P, suggesting the downslope movement of the tropical montane forest, indicating a much cold condition at the time. Besides, it is a striking decline in mangrove pollen and a slight less abundance of the fern spore, indicating the vegetation group of mangrove and fern were suppressed during the mid-Holocene. During the late Holocene, a relatively high level of the herbaceous group provides a more open environment. These changes, are relatively the same as stalagmite record in this area, but different from palaeooceanographic records. This likely indicates that tropical vegetation changes have close relationship with the global monsoon.

Discovery of ferromanganese crust boundary and its genetic and ore prospecting significance

Evidences for the existence of ferromanganese crust boundary were found for the first time during the survey of the “DA YANG YI HAO” Vessel 2003. Some typical characteristics of the boundary are summarized and the significances of the finding of the boundary are included in the genesis discussion. Ore prospecting and assessment of the crust resources are described in this paper. The morphologic and extending characteristics of the crust boundary led to the recognition of two types of crust boundary: interpenetration crust boundary and closed crust boundary. According to the distribution and types of the crust, however, the boundaries are classified into three types: the boundary between ferromanganese crust and detrital sediment, the boundary between tabular crust and seamount nodules, and the boundary between tabular crust and rudaceous crust. This study revealed that the boundary between tabular crust and nodules was not formed under different regional environments but formed under different nucleation potential barriers between different initial growth (nucleation and germination) processes and between solid rocks and loose sediments. The rudaceous crusts are controlled spatially by fracture zones and the crusts’ boundaries are controlled by the seamount structure and landform. The discovery of the crust boundaries reveals the crust’s ‘negative growth’ phenomena (especially for some seamount nodules). The boundary investigation can be helpful in identifying the existence of tabular crust covered by detrital sediments and in calculating the area covered by the crust. The resource calculation error and the resource quality as well as resource exploration degree can be assessed through the survey of crust boundary.