Estimating the uncertainty of coral isochron U–Th ages

Recently, alternative models to estimate the age of diagenetically altered fossil reef corals have been presented based on either redistribution of U or its immediate daughters ²³⁴Th and ²³⁰Th. Here, we present three methods to estimate the uncertainty of ages derived using an amended version of our coral isochron method [Scholz et al., 2004. U-series dating of diagenetically altered fossil reef corals. Earth and Planetary Science Letters 218, 163–178], which is based on addition/loss of U. The obtained uncertainties are substantially larger than those previously published and should, in general, be more reliable. The isochron method yields larger uncertainties than alternative models based on Th redistribution due to -recoil processes. However, comparison of model open-system ages based on such redistribution of U-series daughters for different sub-samples from an individual coral specimen shows that the smaller errors derived with these models cannot account for the observed variability. We recognise that none of the available models is applicable to all corals, probably reflecting different diagenetic processes even in different sub-samples from one coral specimen. To better understand the diagenetic processes and precisely constrain the uncertainties of the ages derived from diagenetically altered corals, the application of all available models is recommended.     

Coral δO records as an indicator of winter monsoon intensity in the South China Sea

We have used correlative analysis between mean December-January-February winter wind velocities, measured at the Xisha Meteorological Observatory (16°50′N, 112°20′E) in the middle of the South China Sea, and mean δ¹⁸O data for the corresponding month from Porites lutea coral, collected in Longwan waters (19°20′N, 110°39′E), to obtain a linear equation relating the two datasets. This winter wind velocity for the South China Sea (WMII_scs) can then be correlated to the coral δ¹⁸O by the equation WMII_scs = −1.213-1.351 δ¹⁸O (‰ PDB), r = −0.60, n = 40, P = 0.01. From this, the calculated WMII_scs-δ18O series from 1944 to 1997 tends to decrease during the 1940s to the 1960s; it increases slightly during the 1970s and then decreases again in the 1980s and 1990s. The calculated decadal mean WMII_scs-δ18O series had a obvious decrease from 5.92 to 4.63 m/s during the period of 1944-1997. The calculated yearly mean WMII_scs-δ18O value is 5.58 m/s from 1944 to 1976 and this decreases to 4.85 m/s from 1977 to 1998. That is the opposite trend to the observed yearly mean SST variation. The yearly mean SST anomaly is −0.27° from 1943 to 1976 and this increases to +0.16° from 1977 to 1998. Spectral analysis used on a 54-year-long calculated WMII_scs-δ18O series produces spectral peaks at 2.4-7 yr, which can be closely correlated with the quasibiennial oscillation band (QBO band, 2-2.4 yr) and the El Ñino southern oscillation band (ENSO band, 3-8 yr). Hence most of the variability of the winter monsoon intensity in the middle of the South China Sea is mainly constrained by changes in the thermal difference between the land and the adjoining sea area, perhaps due to global warming.     

Type and evolution of landscapes of Nansha Islands

ＴＹＰＥＡＮＤＥＶＯＬＵＴＩＯＮＯＦＬＡＮＤＳＣＡＰＥＳＯＦＮＡＮＳＨＡＩＳＬＡＮＤＳＺｈａｏＨｕａｎｔｉｎｇ（赵焕庭）ＳｏｕｔｈＣｈｉｎａＳｅａＩｎｓｔｉｔｕｔｅｏｆＯｃｅａｎｏｌｏｇｙ,ｔｈｅＣｈｉｎｅｓｅＡｃａｄｅｍｙｏｆＳｃｉｅｎｃｅｓ,Ｇｕ...     

华南二叠纪生物成礁模式探讨

二叠纪生物礁广泛发育于我国南方碳酸盐岩地区。鉴于许多研究者从成礁的外部环境因素来探讨生物礁的发育模式,笔者从我国南方二叠纪生物礁的内部成礁因素分析,即从主要造礁生物——钙质海绵和钙质藻类等的生物学和生态学特征、埋藏和保存特点方面进行分析,继而提出了华南二叠纪海绵礁的成礁模式。此模式不同于其它地质历史时期生物礁的成礁模式     

川东黄龙场构造长兴组生物礁分布地震预测研究

在川东黄龙场构造内，利用测井资料和地震数据，通过多种地震信息处理手段（LANDMARK、STRATA等地震叠后反演平台）来提取长兴组地层中生物礁的异常信息，总结已知钻遇生物礁的地震响应特性，建立生物礁异常识别模式。并主要运用STRATA速度反演剖面来预测生物礁厚度变化的分布范围，勾绘出生物礁储层的厚度变化分布图。     

雷州半岛造礁珊瑚Porites lutea月分辨率的δ18O温度计研究

对雷州半岛西南部珊瑚岸礁区1995～1997年生长的造礁珊瑚Poriteslutea的骨骼密度、生长速度和δ¹⁸O分析表明：1)造礁珊瑚骨骼的密度、生长速度和δ¹⁸O与其生存环境的表层海水温度之间存在很好的相关性,高密度、低生长速率和高δ¹⁸O值对应于冬季;2)δ¹⁸O具有明显的年际和季节性变化。根据δ¹⁸O估计的表层海水温度变化范围与实测基本一致,进一步揭示了珊瑚骨骼δ¹⁸O可作为定量研究高分辨率表层海水温度变化的温度计。     

德国泥盆纪生物礁的基本特征

德国泥盆纪的层孔虫十分繁盛，不同形态、不同规模的层孔虫礁体广泛发育于台地内部、台地边缘和深海盆地内的火山周日。块状层孔虫是主要的造礁生物，四射珊瑚也参与了造礁，但数量极少。礁区岩相分异明显，盆地相、礁前相、礁核相和礁后泻湖相清晰可辨。部分礁体，如布瑞隆环礁显示清楚的初殖、拓殖、繁殖和衰亡四个演化阶段。层孔虫礁的主要繁盛期为吉维特期－弗拉斯期。德国泥盆纪生物礁的基本特征类似于加拿大同时期的生物礁，但在德国泥盆纪的礁灰岩杂体内至今尚未发现有经济价值的石油和天然气。这可能与莱茵海西地槽复杂的地质发展史有关。     

利用微量元素分析对广西凌云生物礁成礁环境的研究

本文利用微量元素分析,探讨了广西凌云县二叠系生物礁的成礁环境,指出不同微最元素的分布与生物骨骸的固定作用和沉积环境的影响有关,利用R型因子分析对微量元系进行了分类。     

Calcareous Algae from Northeastern Brilon Reef Complex of Middle and Upper Devonian in Eastern Sauerland， Germany

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南沙群岛海域岛礁鱼类资源的开发现状和开发潜力

南沙群岛海域蕴藏着丰富的礁栖性鱼类资源,是我国珊瑚礁渔业的主要作业渔场.根据近年来的渔业生产数据对开发现状进行了评价,判断南沙群岛岛礁鱼类资源尚处于轻度开发状态.通过采用初级生产力方法估算,南沙群岛岛礁水域鱼类的年生产量不低于2.1t·km-2,以年生产量的50%估算,潜在渔获量不少于5.5万t.