Paleoenvironmental records from the northern South China Sea since the Last Glacial Maximum

Core ZHS-176 contains the paleoenvironmental records from the northern South China Sea (NSCS) since the Last Glacial Maximum (LGM). A coupled approach based on clay mineral assemblages, planktonic foraminiferal oxygen and carbon isotopes, and calcium carbonate content is used to trace the sources of the fine-grained sediment and to investigate the paleoenviornmental evolution in this area. Clay mineral assemblages are dominated by illite (average about 39%) and chlorite (about 27%), which comes mainly from Taiwan and the East China Sea. Kaolinite, which accounts for about 13%, comes mainly from the Zhujiang (Pearl) River, and Luzon Island is the main source for smectite (about 21%). The planktonic foraminiferal oxygen isotopic oscillations during the last glacial period are coeval with climate variations recorded in the Greenland ice core and Western Pacific sediment. These variations include the LGM, Heinrich event 1, Bφlling-Allerφd (B/A), and Younger Dryas. For the Holocene, three periods of strong precipitation (S1-S3) and three periods of weak precipitation (W1-W3) are identified. The oxygen isotopic record exhibits corre-lation with climate records from distant regions, including the high-latitude Northern Hemisphere, providing evidence for global tele-connection among regional climate. A brief, negative planktonic foraminiferal carbon isotopic excursion during B/A reflects increased methane released from marine gas hydrate due to the rapid warming of the water. By comparing calcium carbonate content curves of the core ZHS-176 with these of other five boreholes lying above the lysocline, a remarkable low calcium carbonate event is found during the early Holocene in NSCS.     

南海海盆区深部结构的不对称性及控制因素

南海海盆区具有复杂的构造演化史,但目前对其深部结构的不对称性的研究和控制因素的探讨还存在不足.利用南海最新的重力数据和从27条地震剖面上获取的海盆范围沉积物精确数据计算了全海盆的剩余地幔布格重力异常(residual mantle Bouguer anomaly,RMBA),并反演了海盆的地壳厚度,运用Crust1.0...     

Morphotectonics and evolutionary controls on the Pearl River Canyon system, South China Sea

The Pearl River Canyon system is a typical canyon system on the northern continental slope of the South China Sea, which has significant implications for hydrocarbon exploration. Through swath bathymetry in the canyon area combined with different types of seismic data, we have studied the morphotectonics and controlling factors of the canyon by analyzing its morphology and sedimentary structure, as well as the main features of the continental slope around the canyon. Results show that the Pearl River Canyon can be separated into three segments with different orientations. The upper reach is NW-oriented with a shallowly incised course, whereas the middle and lower reaches, that are located mainly in the Baiyun Sag, have a broad U-shape and have experienced consistent deposition. Seventeen deeply-cut canyons have developed in the slope north of the Baiyun Sag, playing an important role in the sedimentary processes of the middle and lower reaches of the Pearl River Canyon. These canyons display both asymmetrical V- and U-shapes along their lengths. Numerous buried channels can be identified below the modern canyons with unidirectionally migrating stacking patterns, suggesting that the canyons have experienced a cyclic evolution with several cut and fill phases of varying magnitude. These long established canyons, rather than the upper reach of the Pearl River Canyon, are the main conduits for the transport of terrigenous materials to the lower slope and abyssal basin during lowstand stage, and have contributed to the formation of vertically stacked deep-water fans in the middle reach. Canyon morphology is interpreted as a result of erosive sediment flows. The Pearl River Canyon and the 17 canyons in the slope area north of the Baiyun Sag probably have developed since the Miocene. Cenozoic tectonics, sea level change and sediment supply jointly control the morphology and sedimentary structure. The middle and lower reaches of the Pearl River Canyon developed on the paleo-terrain of the Baiyun Sag, which has been a persistently rapid depositional environment, receiving most of the materials transported via the canyons.     

热烈的祝贺(发刊词)

《南极研究》与广大读者见面了.我怀着十分高兴的心情为它的创刊致以热烈的祝贺!我国的南极考察工作起步较晚,但发展较快,尤其是近几年,建成了南极长城站,已在长城站地区进行了三次较大规模的多学科考察,初步取得了可喜的成果.我国已经具备了独立开展南极考察的能力,并取得了一些经验.这些成绩是在党中央、国务院的关怀和支持下取得的,     

三门峡新一代天气雷达冰雹回波特征分析

利用三门峡新一代天气雷达资料,分析了冰雹天气时雷达产品的特征,并确定冰雹天气预报指标。     

冲绳海槽天然气水合物稳定带厚度的计算

水合物稳定带（HSZ）的研究对天然气水合物的成矿与分布规律以及资源评价研究都具有重要的指导意义，文章根据天然气水合物的相平衡条件和相应的压力-温度方程，参照有关的身体算法，讨论了海底天然气水合物稳定带厚度的理论计算方法，并根据稳定带厚度的理论计算方法，在Windows中文平台上编制了简单实用的程序，利用该程序对冲绳海槽水合物稳定带的厚度进行了计算，并讨论了冲绳海槽水合物稳定带厚度的分布特征。     

南海西南次海盆基底形态特征及控制因素

本文解释了横穿南海西南次海盆的两条多道地震测线,对南海西南次海盆的基底形态特征进行了描述和分类,并讨论了基底形态与扩张速率之间的对应关系。研究结果表明,西南次海盆基底可以分为两种类型：类型1为岩浆作用主导的平坦基底,局部有岩浆侵入;类型2为构造作用主导的掀斜断块。扩张速率的计算表明：N3测线所代表的西南次海盆北东段的半扩张速率在13~36 mm/a之间周期性变化,而在NH973-1所代表的中段半扩张速率基本稳定在19 mm/a左右,未有明显变化。海盆基底的类型变化与扩张速率的对应关系明显,在扩张速率较快的区域以类型1为主,而在扩张速率慢的区域以类型2为主。西南次海盆北东段扩张速率呈现周期性变化,相应海盆基底也表现为相间排列;而西南次海盆中段的基底比较单一,以类型2为主。南海西南次海盆北东段扩张时间更久,并可能存在周期性活动的岩浆房;而海盆中段海底扩张发生较晚,岩浆作用较弱,从而造成西南次海盆从北东到南西不同的基底形态特征。     

The crustal nature of the northern Mozambique Ridge,Southwest Indian Ocean

The Mozambique Ridge (MOZR) is one of the basement high structures located in the Southwest Indian Ocean, parallel to the Southeast African continental margin. It was formed as a result of the tectono-magmatic evolution of the Gondwana breakup. The origin of the MOZR has been highly debated, with models suggesting either continental or oceanic origin. With new free-air gravity anomaly and multichannel seismic (MCS) reflection data, we present results of 2D density modeling along two seismic profiles acquired by R/V Xiangyanghong 10 at the northern Mozambique Ridge (N-MOZR) between 26°S and 28°S. We observed high free-air gravity anomaly and strong positive magnetic anomaly related to the emplaced seaward dipping reflectors (SDR) and high density lower crustal body (HDLCB), and high Bouguer gravity anomaly associated with the thinning of the continental crust underneath the N-MOZR over a distance of ~82 km. This suggests a thinned and intruded continental crust bound by the Mozambique Fracture Zone (MFZ) that is characterized by gravity low and negative magnetic anomaly. This fracture zone marks the continent-ocean boundary (COB) while the N-MOZR is the transform margin high, i.e., marks the continent-ocean transition (COT) of the Southern Mozambique margin, following the definition of transform margins. We suggest that the N-MOZR was formed by continental extension and subsequent breakup of the MFZ, accompanied by massive volcanism during the southward movement of the Antarctica block. The presence of SDR, HDLCB, and relatively thick oceanic crust indicates the volcanic nature of this transform margin.     

冲绳海槽天然气水合物稳定带特征和资源量评价

根据冲绳海槽多道地震资料的处理解释,在16条地震剖面上发现了水合物拟海底反射层BSR,经过AVO、波形反演等特殊的处理技术,首次直接利用BSR圈定了冲绳海槽天然气水合物具体分布范围,直接利用数据得出了天然气水合物稳定带厚度在冲绳海槽的分布趋势,认为海槽南部最厚,中部次之,北部最薄,并通过计算得出了冲绳海槽水合物稳定带的厚度和水合物资源量,对今后海槽水合物勘查和资源量评价具有一定的指导意义。     

天然气水合物释放甲烷对晚第四纪气候影响的古环境记录

天然气水合物作为全球碳循环中最大的碳储库,在全球变暖或海平面变化导致压力减小的情况下将分解释放大量甲烷进入水体和大气,对气候和环境造成巨大的影响。自从1995年Dickens等提出形成晚古新世温度峰值事件(LPTM)的主要原因是海底天然气水合物大规模分解释放甲烷这一假说以来,地质历史时期天然气水合物演化的研究蓬勃发展。而晚第四纪以来经历了一系列气候变化过程,在加利福尼亚的圣巴巴拉盆地、瓜伊马斯盆地、俄罗斯的贝加尔湖、格陵兰海、秘鲁、东格陵兰陆架、巴布亚新几内亚以及南海等地都记录了天然气水合物分解释放而形成的碳同位素负偏的古环境信息。主要针对这些古环境记录进行整理总结,为进一步研究天然气水合物的动态演化提供基础。