网纹红土的成因及其研究意义

本文阐述我国网纹红土的分布和特征,着重讨论网纹红土的形成原因,指出网纹红土可表征我国南方中更新世以来新构造运动的幅度和性质,并可作为我国东部是否存在古冰川作用的佐证.     

辽西建平地区三座庙序列侵入岩年代

三座庙序列侵入岩U—Pb法一致曲线年龄值1708Ma、1717Ma;K—Ar法年龄值为1670Ma、1530Ma、1316Ma,表明该系列侵入岩为中元古宙长城纪大红峪期火山喷发岩的同期侵入体,属燕辽旋回兴城运动的产物。     

渐近非扩张映象多步迭代序列的收敛性

研究了凸度量空间中用多步迭代序列来逼近渐近非扩张映象的不动点,并给出了其收敛于不动点的充分必要条件.     

Quaternary glaciation of the Bale Mountains,Ethiopia

Central Ethiopia comprises a high plateau at 2000–3000 m, formed from Tertiary lava flows and bisected by the Eastern African Rift. Ten volcanic mountains rise to altitudes of just over 4000 m, but on only three has Quaternary glaciation been substantiated by published field observations. On the Bale Mountains (4400 m), a previous report based on limited evidence proposed an ice‐cap extending to 600 km². Based on aerial photographs and ground surveys, this paper reports evidence of a more complex situation. A wide spread of large erratic boulders on the plateau records a central ice cap of 30 km², though ice probably extended for a further 40 km². Further north two groups of deeply incised and clearly glaciated valleys contain moraines and roches moutonnées (60 km²). On interfluves between them and on the open north slopes are moraines from an earlier stage of the same glaciation or from a distinct older event. Altogether about 180 km² may have been glaciated. Cores dated by ¹⁴C from inside and outside the glaciated area suggest that at least the northern valley glaciers may date from the Last Glacial Maximum. Estimated equilibrium line altitudes for these glaciers and the ice‐cap are 3750–4230 m. Copyright © 2005 John Wiley & Sons, Ltd.     

Geomorphological and Pedological Investigations on the Glacial History of the Kali Gandaki (Nepal Himalaya)

In semi-arid orographic left tributaries of the Kali Gandaki at the northern and western flank of the Nilgiri Himal, glacio-geomorphological and pedological investigations were carried out on prehistoric moraines. Geomorphological relief analysis was derived from other literature and the own fieldwork of the author. The resulting glacial chronology was used as benchmark to explore the limits of different pedological dating methods regarding the degree of soil development. These methods are based on iron fractionation, total element contents and particle size distribution. In general the different glacial stages are mirrored correctly in the relative graduation of soil development. The ratio of well crystallised pedogenic iron-oxides to the total iron content and the ratio fine clay to total clay are most suitable, because they are almost independent from existing changes in the lithological composition. The total element based weathering indices are less suitable, because they react highly sensitive to the geology dependent shift to higher carbonate contents. Most of the grain size based weathering indices are inapplicable because of the typically high textural variability within till deposits.     

有机地球化学参数在层序划分对比中的应用——以冀中拗陷束鹿凹陷沙三下亚段为例

深水细粒沉积层系的层序地层单元细分和对比,是建立合理的层序地层格架的关键,也是进行深水区岩性油气藏勘探开发的一项重要基础研究工作。但往往由于细粒沉积层系层序地层单元划分标志不明显,其划分对比较为困难,这也是层序地层学研究的难点。依据高分辨率层序地层学原理,从沉积层序的成因及其表现入手,应用表征沉积环境或沉积物特征的有机地球化学参数在纵向上的周期性变化规律,对渤海湾盆地冀中坳陷束鹿凹陷沙三段下亚段半深湖—深湖相泥灰岩沉积进行了层序地层单元划分和对比,较好地识别出了4级旋回与5级旋回,为建立高分辨率层序地层格架奠定了基础。     

鄂尔多斯盆地东北缘晚古生代陆表海含煤岩系层序地层研究

通过区域不整合面、沉积体系转换面、构造应力场转换面和水上暴露面等层序界面的识别,对研究区进行层序地层划分,指出鄂尔多斯盆地东北缘晚古生代陆表海含煤岩系发育7个三级层序。在此基础上,认为陆表海层序仍然具有“三元”结构,由低位体系域、海侵体系域和高位体系域组成。在盆地北部发育的多期河道砂岩具有低位体系域的下切谷充填特点——面状充填,如晋祠砂岩、桥头砂岩以及北岔沟砂岩等。煤层在层序格架中的定位与海平面变化的转换时期有关,主要发育在陆表海环境的海侵体系域下部以及陆相环境的高位体系域上部。     

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。     

两次强震峰值速度比及其余震分布特征

基于甘肃地震台网和青海地震台网对岷县-漳县MS6.6地震和门源MS6.4地震的波形记录,采用FFT方法分别计算这两次地震三分向的峰值速度,讨论分量之间峰值速度比的分布特征,进而研究其震源性质。结果表明,岷县-漳县地震具有逆冲兼左旋位错性质,南北向能量明显大于东西向;门源地震以逆冲为主,略具左旋走滑特征,两个水平分量的能量相当。结合这两次地震的余震序列分布特征及其他学者的研究结果推测,岷县-漳县地震的发震断层应该是位于临潭-宕昌断裂西北侧且与其平行的一条次级断裂;门源地震的发震断层应该是冷龙岭断裂西北侧的次级断裂,但受到冷龙岭断裂活动控制。     

山东省乳山地区余震分布与速度结构研究

利用山东乳山流动观测台网资料,采用双差精定位方法重新确定2014-05以来山东乳山M3.2地震余震序列的分布;在此基础上,利用双差层析成像方法反演该地区的三维速度结构模型。结果显示,乳山地区的余震序列整体呈现出圆形聚集特征,优势分布主要集中在3~8 km深度,乳山震群集中区的余震活动主要发生在破裂集中的区域,在5 km深度最为集中,说明乳山震群主要发生的区域为上地壳;研究区不同深度的P波速度变化明显。由于离已知的主断层有一定的距离,因此可以判断余震分布集中区可能是乳山断裂的分支或者是一条新的隐伏断裂。