帘蛤科4种养殖蛤群体遗传多样性和种间关系的fAFLP分析

利用荧光标记扩增片段长度多态性(fAFLP)技术对文蛤(Meretrix meretrix)、青蛤(Cyclina sinensis)、菲律宾蛤仔(Ruditapes philippinarum)和硬壳蛤(Mercenaria mercenaria)4种帘蛤科贝类的群体遗传多样性和种间关系进行了研究。选择EcoRⅠ/MseⅠ进行酶切,使用6个E 3/M 3引物组合进行扩增,共获得1 096个位点,多态位点比率95.1%,片段长度50~456 bp。其中,文蛤、青蛤、菲律宾蛤仔和硬壳蛤分别得到681,715,702和694个位点,相应的多态位点比率为76.8%,81.7%,83.0%和75.1%,得到17个种特异性位点,可作为4物种特征标记。分析了群体遗传相似系数和遗传多样性指数以及种间遗传相似系数。结果表明,硬壳蛤群体遗传相似系数最高(0.670 9),遗传多样性指数最低(0.236 0);菲律宾蛤仔群体遗传相似系数最低(0.592 5),遗传多样性指数最高(0.261 8);根据遗传相似系数采用UPGMA法构建了4物种32个体的聚类图,表明文蛤与菲律宾蛤仔遗传关系最近,青蛤与其他3物种遗传关系较远。     

莱州湾南岸第三陆相层年龄的铀系等时线法(TSD)测定

于莱州湾南岸ZK32-1钻孔第三陆相层上下边界处选取自生钙质结核,采用样品全溶铀系等时线法(TSD法)测定钙质结核的年龄。测试结果表明,所有等时线上的数据都有很好的线性关系,表明所获得的年龄数据是合理的。通过对样品代表性的讨论,说明所选取的钙质结核的年龄确可代表其所在地层的年龄,从而得出莱州湾南岸第三陆相层的沉积起止时间为72.16ka B.P.±7.41ka B.P.到45.34ka B.P.±5.35ka B.P.的结论。本研究首次获得莱州湾南岸地层的铀系TSD年龄,为全面认识该地区晚更新世地层年代学提供了一个新视角。     

南阿尔金巴什瓦克基性麻粒岩的变质演化P-T-t轨迹

大陆碰撞造山带中高压麻粒岩的P-T-t轨迹研究对于理解造山带的热演化历史及大陆地壳的形成与演化具有重要的意义,然而,如何连接同位素年龄与变质演化过程是恢复和建立P-T-t轨迹的重点和难点。本文通过对南阿尔金巴什瓦克地区基性麻粒岩的详细岩相学研究,认为该基性麻粒岩经历了原岩阶段(M1)、峰期变质阶段(M2)、峰后退变质阶段(M3)以及晚期角闪岩相-绿片岩相退变质阶段(M4)。其中,传统矿物温压计和矿物微量元素温压计获得该基性麻粒岩所记录的峰期变质条件分别为17.5～22.6 kbar,901～985℃和17～28 kbar,1012～1049℃,退变质阶段的温压条件为7.6～10.7 kbar,750～810℃。此外,锆石U-Pb年代学结果表明基性麻粒岩的变质时代为491±3.5 Ma (MSWD=0.62),结合锆石和石榴子石的微量元素分配系数以及前人的实验岩石学数据,认为该变质时代记录了早古生代高压-超高温的变质事件,进而恢复了南阿尔金基性麻粒岩所记录的顺时针P-T-t轨迹。     

A hybrid ensemble method for improved prediction of slope stability

Accurate prediction of slope stability is a significant issue in geomechanics with many artificial intelligence (AI) techniques being utilised. However, the application of AI has not reached its full potential because of the lack of more robust algorithms. In this paper, we proposed a hybrid ensemble method for the improved prediction of slope stability using classifier ensembles and genetic algorithm. Gaussian process classification, quadratic discriminant analysis, support vector machine, artificial neural networks, adaptive boosted decision trees, and k‐nearest neighbours were chosen to be individual AI techniques, and the weighted majority voting was used as the combination method. Validation method was chosen to be the 10‐fold cross‐validation, and performance measures were selected to be the accuracy, the receiver operating characteristic curve, and the area under the receiver operating characteristic curve (AUC). Grid search and genetic algorithm were used for the hyperparameter tuning and weight tuning respectively. The results show that the proposed hybrid ensemble method has great potential in improving the prediction of slope stability. Compared with individual classifiers, the optimum ensemble classifier achieved the highest AUC value (0.943) and the highest accuracy (0.902) on the testing set, denoting that the predictive performance has been improved. The optimum ensemble classifier with the Youden's cut‐off was recommended for slope stability prediction with respect to the AUC value, the accuracy, the true positive rate, and the true negative rate. This research indicates that the use of the classifier ensembles, rather than the search for the ideal individual classifiers, might help for the slope stability prediction.     

Influence of late holocene pyroclastic eruptions on the sedimentary geochemistry of Lake Rotoiti,North Island,New Zealand

Lake Rotoiti in Taupo Volcanic Zone was formed by damming of the drainage system through the floor of Okataina Caldera. Basin sediments are predominantly silt or sand, with mineralogy consistent with derivation from local silicic rocks and airfall tephras. Sandy lithofacies around the shoreline are wave worked deposits. Sand and gravel lithofacies in deeper water and on steep slopes are largely relict or airfall tephras, or both. Profundal sediments are diatomaceous silts. Organic-rich diatomaceous silts also accumulate in near-shore wave-damped zones under weed beds.Short cores penetrated the Tarawera (1886 AD) and Kaharoa (1180 AD) Tephras, identified by their stratigraphic position, geochemistry and mineralogy. Localised slumping is evidenced from secondary tephras interbedded and redeposited within the basin silts. Sedimentation rates in the basins, estimated from the age of bounding tephras, are 0.9 to 4.0 mm y^-1, and are highest under the influence of inflowing water from adjacent Lake Rotorua. For several hundred years prior to the Tarawera eruption sediment accumulation rates and the sediment geochemistry remained unchanged; deposition was predominantly biogenic opaline silica with a small terrestrial component. The Tarawera eruption deposited a terrestrial-silica, aluminum-rich primary tephra across the lake, which was followed by reworked tephra from within the catchment, the effects of which were progressively diluted by biogenic opaline silica as conditions stabilised. While the major effects of the eruption have been rapidly absorbed the lake has not returned to pre-eruption background conditions. A new equilibrium has been attained in which Tarawera Tephra continues to be eroded into the lake and is the principal source for a doubling of sedimentation rates following the eruption. High arsenic levels in some diatomaceous silts are attributed to episodic venting of hydrothermal fluids or gases into the water column.     

地幔橄榄岩部分熔融及相转变（尖晶石相→斜长石相）过程中的固相化学成分演化──Ⅱ．在自然岩石中的应用

分析了全球一些有代表性的上地幔尖晶石橄榄岩和斜长石橄榄岩中各矿物的化学成分变化特征。发现在斜长石橄榄岩中，尖晶石和斜方辉石富Ｔｉ，且Ｔｉ含量随Ｃｒ／（Ｃｒ＋Ａｌ）的增大而增大；单斜辉石富Ｔｉ贫Ｎａ，其Ｔｉ含量随Ｎａ含量的增大而减少。据此，结合实验结果，可以肯定世界各地大多数斜长石二辉橄榄岩在斜长石相域内未经受部分熔融。岩体所曾经受的部分熔融只发生在尖晶石或石榴石相。它们的相对熔融度可以用下面两个指标来估计：（１）最贫Ｔｉ尖晶石的Ｃｒ／（Ｃｒ＋Ａｌ）；（２）单斜辉石的最高Ｎａ含量。对于尖晶石橄榄岩，从二辉橄榄岩、方辉橄榄岩到纯橄榄岩，其尖晶石和斜方辉石的Ｃｒ／（Ｃｒ＋Ａｌ）逐渐增大，而含量很低的Ｔｉ或Ｎａ在尖晶石、斜方辉石及单斜辉石中保持不变或趋向逐渐减小。尖晶石橄榄岩的相对熔融度可据尖晶石的Ｃｒ／（Ｃｒ＋Ａｌ）和单斜辉石的Ｎａ含量来判断。     

辽东太子河流域石炭—二叠纪岩相古地理及铝土矿成矿地质条件

晚石炭—早二叠世的辽东太子河盆地是一个周边为平移断层的断陷盆地。以东西向垂直运动为主体的构造活动控制了盆地的发展和演化。根据构造特征、沉积相和古地磁与华北腹地石炭一二叠系的差异,太子河地区的石炭一二叠系应是华北型石炭一二叠系的一个分支,作者称“辽东亚型”。古地理演化表现为从晚石炭世早期的扇三角3洲→峡湾海岸→碳酸盐台地的快速海进,直至早二叠世末的三角洲→冲积平原→湖泊体系的缓慢海退,堆积了近陆特征明显的、近尔西展布的各沉积相带。随时代渐新,堆积物中碎屑组分成熟度趋于增高,大地构造背景从部分卷入大陆边缘活动带过渡为大陆板块克拉通内部,均反映本区的断陷活动由次稳定向稳定型转化。铝土矿成矿物质主要来源于北部古陆结晶岩石,系红土(钙红土)—沉积成因。G层铝土矿形成于泻湖边缘环境;B臣则位于近海湖泊的滨—浅湖地带,同受控于北纬41°20′的同沉积断裂,与北东向断裂复合凹地为成矿最佳场所。     

河南临汝安沟地区前嵩山群变质作用

河南临汝安沟地区前嵩山群变质矿物、变质矿物组合以及变质温压条件研究表明,前嵩山群分属不同的变质建造,其中安沟群属中压相系绿片岩相变质作用,登封群头道河组为中压相系角闪岩相。同时,两套地层变质作用之间缺少钠长—绿帘角闪岩相,这一变质作用的间断,从一个侧面反映了地层的间断。     

改进的最优窗宽理论对年径流量的插值预测研究——以黄河利津等站为例

针对小样本数据造成年径流量预测效果不理想的情况,以及非对称和非正态资料的处理问题,引入信息扩散和模糊映射思想,同时运用遗传算法改进最优窗宽理论,建立了新的扩散插值模型。该模型通过对零散数据点的信息进行模糊扩散,进而实现对有限数据点信息向其邻近区域点的概率插值。选取黄河利津站为例,根据其近70 a(1942—2011年)径流量实测数据,进行了缺损数据的插值和预测试验,同时与正态扩散插值模型进行对比分析,结果表明:1)预测值能较好地模拟实际径流序列的波形变化,对丰水年(如2007年)和枯水年(如2009年)的预报都比较准确;2)中长期预报(10a)平均相对误差仅为11.59%,相较传统方法有较大的改进;3)以黄河流域2个站点(花园口和兰州)和长江流域的3个站点(朱沱、宜昌和大通)年径流量预测试验以及海温资料的插值试验作为补充,验证了该算法的有效性和普适性。该模型可为实际水文数据资料的客观分析和中长期预报提供参考。     

应用粒度成因单元划分高分辨率层序地层基准面旋回

摘要　在Goodwin和Anderson于1985提出的PAC假说基础上,针对目前基准面旋回级别划分较为混乱的状况,将基准面旋回赋予了自旋回和异旋回的涵义,探索性地提出了粒度成因单元的概念和研究方法,并将其应用到柴窝堡盆地中二叠统芦草沟组高分辨率层序地层的研究中,建立了该区中二叠统草沟组高分辨率层序地层格架,划分出了2个长期基准面旋回6个中期粒度成因单元以及5段。