Morphological patterns of Aptian Lithocodium–Bacinella geobodies: relation to environment and scale     

NIELS RAMEIL  ADRIAN IMMENHAUSER  GEORG WARRLICH  HEIKO HILLGÄRTNER  HENK J. DROSTE 《Sedimentology》2010,57(3):883-911

Lithocodium aggregatum and Bacinella irregularis are now extinct, shallow marine life forms of unknown taxonomic origin. Forming part of the tropical platform biota during much of the Mesozoic, these organisms experienced bloom periods and temporarily replaced rudist–coral assemblages during parts of the Early Aptian. Within the limitations of time resolution, this ‘out‐of‐balance’ facies is coeval with the Oceanic Anoxic Event 1a‐related black shale deposition in oceanic basins but the triggering factors remain poorly understood. Here, a platform‐wide comparison of Lithocodium–Bacinella geobodies and morphotypes from the Sultanate of Oman is presented and placed in its environmental, bathymetric and physiographic context. Lithocodium–Bacinella geobodies reach from kilometre‐scale ‘superstructures’ to delicate centimetre‐sized growth forms. Clearly, scale matters and care must be taken when drawing conclusions based on spatially limited observational data. Whilst the factors that cause Lithocodium–Bacinella expansion should probably be considered in a global context, regional to local factors affected growth patterns in a more predictable manner. Here, the unresolved taxonomic relationship remains the main obstacle in any attempt to unravel the response of Lithocodium–Bacinella to specific or interlinked environmental parameters as different organisms respond differently to changing environment. Acknowledging these limitations, the following tentative patterns are observed: (i) Lithocodium–Bacinella tolerated a wide range of hydrodynamic levels and responded to differences in energy level or physiographic settings (margin, intrashelf basin, inner platform) by obtaining characteristic growth forms. (ii) Lithocodium–Bacinella favoured low‐sediment input but had the ability to react to higher sedimentation rates by enhanced upward growth; a feature perhaps pointing to a phototrophic metabolism. Circumstantial evidence for continuous growth within the upper‐sediment column is debated. (iii) The availability of accommodation space had a direct influence on the maximum size of geobodies formed. (iv) Fluctuating nutrient levels and sea water alkalinity may have affected the growth potential of Lithocodium–Bacinella. Understanding the relationship between Lithocodium–Bacinella morphogenesis on a wide range of scales and local environmental parameters allows for better prediction of the spatial distribution of reservoir properties and also results in an improved interpretation of palaeoenvironments. This study might represent a useful first step in this direction.  相似文献   

南海岩石圈厚度变化特征及其构造意义   总被引：2，自引：0，他引：2       下载免费PDF全文

姚伯初  万玲 《中国地质》2010,37(4)

地震层析资料表明,南海地区,自红河口向南经南海、苏录海到苏拉威西海,岩石圈速度低,底部横波速度仅4.4km/s,岩石圈厚度在60～80km,为薄岩石圈地区;而软流层的速度也较低,在4.2～4.4km/s,但厚度较大,大于200km。从红河—莺歌海断裂带经南海到苏录海,存在一条北西向宽约200km的上地幔北西向低速带,速度在4.05～4.25km/s(面波速度)。它反映了新生代南海地区上地幔的动力学过程。南海岩石圈厚度变化存在明显差异,南海陆缘,岩石圈厚度在70～80km,而在南海洋盆之下,岩石圈厚度超过100km,岩石圈底部存在高速岩石层,并且洋盆下的岩石圈之厚度比大陆边缘厚,在海盆岩石圈下部的60～80km深度上存在一高速层,纵波速度为8.2～8.3km/s。特别是中央海盆及西北海盆与西南海盆,其下部岩石圈中均存在一高速岩石层,这是非常具有构造意义的。由此笔者提出大陆岩石圈裂离、上地幔因减压而部分熔融所产生的基性岩浆形成南海新生代洋壳的猜想。  相似文献   

Eight new and three recalculated orbits for binaries     

Z. Cvetkovi&#x;  B. Novakovi&#x; 《Astronomische Nachrichten》2010,331(3):304-311

In this paper new orbital elements are given for eleven binaries. For eight of them, WDS 00003–4417 = I 1477, WDS 00106–7313 = I 43 AB, WDS 00366+5609 = A 914, WDS 00519–4343 = I 47, WDS 01315+1521 = BU 506, WDS 01577+4434 = A 1526, WDS 08144–4550 = FIN 113 AB and WDS 08291–4756 = FIN 315 Aa‐Ab, the orbital elements are calculated for the first time. For three of them, WDS 04422+2257 = MCA 16 Aa‐Ab, WDS 08275–5501 = FIN 116 and WDS 14567–6247 = FIN 372, the orbital elements are recalculated. One of the eleven binaries, MCA 16 Aa‐Ab, was discovered by McAlister in 1980 by speckle interferometry and four pairs were discovered by Finsen between 1929 and 1960. For these five pairs, all measured separations are less than 0″.4 and most of the observations were done by using the interferometric techniques. The orbital periods calculated here are between 39 and 270 years. The remaining six pairs were discovered between 1878 and 1926 and most of the observations are visual. They have longer orbital periods, between 384 and 1637 years. In addition to the orbital elements the masses, dynamical parallaxes, absolute magnitudes and ephemerides for the next five years are also given in this paper (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Elemental abundance analyses with DAO spectrograms: XXX. The middle B through early A stars ξ2 Ceti (B9 III), 21 Aquilae (B8 II‐III), ι Aquilae (B5 III), and ι Delphini (A2V)     

S.J. Adelman  P.C. Westbrook  A.F. Gulliver 《Astronomische Nachrichten》2010,331(4):378-383

This series of high quality elemental abundance analyses of mostly main‐sequence band normal and peculiar B, A, and F stars defines their properties and provides data for the comparison with the analyses of somewhat similar stars and with theoretical predictions. Most use high dispersion and high S/N (≥ 200) spectrograms obtained with CCD detectors at the long camera of the Coudé spectrograph of the 1.22‐m Dominion Astrophysical Observatory telescope. Here we reanalyze 21 Aql with better quality spectra and increase the number of stars consistently analyzed in the spectral range B5 to A2 by analyzing three new stars for this series. In the early A stars the normal and non‐mCP stars have abundances with overlapping ranges. But more stars are needed especially in the B5 to B9 range. ξ² Cet on average has a solar composition with a few abundances outside the solar range while both 21 Aql and ι Aql have abundances marginally less than solar. The abundances of ι Del are greater than solar with a few elements such as Ca being less than solar. It is an Am star (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

P/2008 T1 (Boattini): Another comet under transition from Saturn to Jupiter     

G. Hahn  C.‐I. Lagerkvist 《Astronomische Nachrichten》2010,331(7):692-695

The newly discovered periodic comet P/2008 T1 (Boattini) is found to have experienced a recent capture into its present orbit, following a close approach to Saturn in 1995 to within 0.17 AU. This orbital change transferred the comet into an orbit tangent to that of Jupiter, which lead to an even closer passage within 0.02 AU with that planet in 2003 decoupling it from the influence of Saturn (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

卡马水库应急除险工作的启示          下载免费PDF全文

刘宁  黄金池  张启义 《水科学进展》2010,21(6):742-747

2009年汛期,广西河池卡马水库右岸溢洪道附近发生垮塌,大坝安全风险骤然增加.在应急除险实践中,同时对大坝不同状态进行了有限元渗流分析及采用非线性指标进行边坡稳定分析,初步确定出险位置可能处于放空洞中段,在此基础上,对水库溃决风险进行了分析,得出了风险决策依据,从而提出减灾措施,有效降低了水库溃决的风险.从卡马水库的应急处置出发,探讨了中国水库应急除险的关键技术,并提出了中国水库安全管理相关的一些重要问题.  相似文献   

黑潮源区沉积物微生物多样性初步研究     

魏玉利  王鹏  赵美训  张传伦 《地球科学进展》2010,25(2):212-219

从黑潮源区采集上层沉积物,进行DNA提取,以细菌和古菌的16S rDNA通用引物PCR扩增黑潮源区沉积物中细菌和古菌群落的16S rDNA,并构建细菌和古菌的16S rDNA文库,经限制性片段长度多态性分析(Restriction Fragment Length Polymorphism,RFLP),DNA序列测定和系统发育分析,对黑潮源区表层沉积物的细菌和古菌多样性进行了研究。研究结果表明:黑潮源区细菌包括了变形杆菌(Proteobacteria)、酸杆菌(Acidbacterium)、浮霉菌(Planctanycene)、疣微菌(Verrucomicro-bia)和Candidate division OP8和拟杆菌(Bacteroidetes)共6个类群,其中变形杆菌是优势类群。古菌包括了泉古菌(Crenarchaeota)和广古菌(Euryarchaeota),其中泉古菌占优势;泉古菌包括MCG、C3、MBGA和MGI 4个类群,而广古菌包括SAGMEG、MBGE和MEG 3个类群,其中MBGE是优势类群。  相似文献   

综合物探方法在福建高速公路隧道勘察中的应用     

杨勇 《福建地质》2010,29(2):128-134

在高速公路勘察前期,物探勘察能为高速公路线路的设计及其它勘察工作的布置提供基础资料。根据不同的地质条件以及勘察要求选择合适的物探方法,能达到事半功倍的效果。通过具体实例说明几种物探方法在福建省境内高速公路隧道勘察中的应用效果、存在问题及解决方法等。  相似文献   

数字测井在福建清流马地煤田勘查中的应用     

范德旺 《福建地质》2010,29(2):135-138

清流马地煤矿的勘查实例,说明综合数字测井在煤田勘查中能显示煤层分布状况,可有效地对煤层与围岩进行分层,解决地质问题直观,效果较好。  相似文献   

山区高速公路地质勘察中几种方法的综合应用   总被引：1，自引：0，他引：1  

刘义华 《福建地质》2010,29(3):250-254

龙长高速公路是闽西通往赣南的唯一的一条快速汽车通道。该公路位于山区路段,跨越不同地形(地貌)及地质构造单元,地质构造条件复杂,地层多,岩性多变。介绍了通过多种勘探方法的综合应用、分析评价,有效地解决了在以桥梁、隧道为主的线性工程勘察中,钻孔布置、钻探施工、工程地质测绘、工程地质评价、路线方案比选等技术难题,效果显著。  相似文献