Quantifying particle aggregation in sediments     

DAVID HABERLAH  GRANT H. MCTAINSH 《Sedimentology》2011,58(5):1208-1216

Sediments often occur as non‐normal size distributions composed of discrete, partially aggregated particle populations. These populations reflect provenance, dispersal pathways and their depositional environments. Recent experimental laboratory studies describing mud flocculation in turbulent marine systems prompted this investigation of the potential of aggregates to record size‐sensitive transport dynamics in a terrestrial fluvial system. Here, sediment‐size distributions in their natural condition of particle–aggregate mixtures are analysed by parametric statistics. A practical and freely available decompositional approach is outlined and field tested, which allows sediment to be viewed in both its conventional particulate form and as its naturally occurring mixture of transport‐stable aggregates and elementary particles. From a sequence of upward‐fining slack water couplets in the Flinders Ranges, South Australia, it is demonstrated that the characteristics, provenance and depositional history of fine‐grained sediments consisting of particle‐aggregate mixtures can best be understood fully by quantifying aggregation.  相似文献   

生产探矿实践对前常铁矿矿体的重新认识     

陈计划 《安徽地质》2011,(4):257-259,278

前常铁矿地质条件较复杂,摸清矿体形态,满足矿山生产三级矿量平衡是一项十分迫切的任务。通过对前常铁矿-360m水平以上生产勘探揭露与原地质资料对比,发现矿体的分布、形态、产状、规模、连续性及资源储量变化极大,为典型的"鸡窝"状矿体,生产中必须重新认识和圈定矿体。  相似文献   

天然气水合物钻井泥浆冷却系统的设计及现场应用   总被引：3，自引：1，他引：2       下载免费PDF全文

李国圣  孙友宏  郭威 《探矿工程》2011,38(2):8-11

从天然气水合物赋存的温压条件入手,说明了制冷泥浆的重要性。介绍了天然气水合物钻井泥浆冷却系统的结构组成、工作原理及设计过程。进而阐述了该套系统在中国冻土区天然气水合物科学钻探施工中的应用情况。试验证明：该套系统完全达到了设计要求,并首次成功地在青藏高原木里盆地永冻区钻获天然气水合物样品。  相似文献   

明光苏巷石盐钾盐矿区钻孔地层造浆的研究          下载免费PDF全文

罗艳珍  乌效鸣  朱恒银  刘鸿燕  王幼凤 《探矿工程》2011,38(3):38-40

粘土侵是地层粘土侵入钻井液使其性能变坏的现象。只要在沉积地层（一般为砂岩、泥岩、页岩、灰岩）中钻进,或多或少都存在粘土侵入钻井液的问题,使其性能变坏。而地层造浆不但解决了粘土侵的问题,同时把粘土侵变废为宝、变害为利,关键问题是什么样的地层可以采用地层造浆。目前国内各个地方都在不自主的使用地层造浆,而对地层造浆的具体研究却相对较少。以明光苏巷石盐钾盐矿区ZK012普查（科研）钻孔为例对地层造浆进行了探讨研究。  相似文献   

低固相泥浆在福建煤田钻探中的应用          下载免费PDF全文

李宏 《探矿工程》2011,38(9):18-20

通过对福建煤田地层特征及其对钻探影响的分析,阐述了在福建煤田钻探中所遇的主要问题,结合实践论述了低固相泥浆的主要性能和优点、以及低固相泥浆对预防处理水敏性地层的缩径和破碎、松散等不稳定地层的坍塌、掉块现象具有的效果,对保证施工的顺利进行、提高施工质量与效率的重要作用。  相似文献   

海底节点长期地震观测:油气田开发与CO2地质封存过程监测     

耿建华  董良国  马在田 《地球科学进展》2011,26(6):669-677

地震观测方法目前被广泛用于海底油气田勘探开发与CO2地质封存过程监测.比较了海面拖缆地震观测与海底节点地震观测方法的差异.海底节点地震观测方法能够采集多分量、全方位、高信噪比和高分辨率数据,同时具有数据定位精度高、采集可重复性以及数据采集性价比高等优势.在回顾海底节点地震观测方法发展过程与现状的基础上,展望了海底长期节...  相似文献   

Nematode species distribution patterns at the Håkon Mosby Mud Volcano (Norwegian Sea)     

Daria Portnova  Vadim Mokievsky  Thomas Soltwedel 《Marine Ecology》2011,32(1):24-41

The Håkon Mosby Mud Volcano (HMMV) is a methane seep that is densely populated by the bacteria Beggiatoa spp. as well as by tubeworms of the Family Siboglinidae. Analyses of samples from seven stations located in five different habitats (bare sediments, bacterial mats, siboglinid fields, sediments with small patches of siboglinids and areas of ‘normal’ sea floor) revealed differences in the density and species‐level diversity of nematode communities. Total densities increased from stations inside the mud volcano and on its rim towards the ‘normal’ areas outside the volcano. Nematode species diversity was similar in samples from the siboglinid fields and the bare HMMV sediments. However, the sediment with patches of siboglinids collected outside the volcano was characterised by a diverse nematode community comprising 47 species, whereas the control sediments without siboglinids yielded only 27 species. The nematode assemblage at the bacterial mat site included only two identified species, Halomonhystera disjuncta and Sabatieria ornata, with H. disjuncta being strongly dominant. Terschellingia distlamphida, S. ornata and Aponema ninae dominated nematode communities at the siboglinid fields and in bare HMMV sediments. Species dominating at stations inside the caldera were found in comparable low densities in the sediment with siboglinid patches collected outside the volcano, but were missing in the background samples, where species of Endeolophos, Acantholaimus and Desmoscolex were dominant. Species diversity generally decreased with sediment depth. A subsurface‐dwelling nematode community was observed in the siboglinid fields and the bare sediments. Background sediments showed a sharp decline with 18–20 species at 0–2 cm versus three species at 3–5 cm sediment depth. The trophic composition of the nematode fauna at the HMMV showed a prevalence of deposit feeders at almost all stations, whereas background sediments exhibited a uniform distribution of non‐selective and selective deposit feeders and epistrate feeders. The high percentage of deposit feeders inside the mud volcano could be related to the grain‐size distribution and the significantly higher bacterial biomass compared to the control sediments.  相似文献   

Light as a driver of phytoplankton growth and production in the freshwater tidal zone of a turbid estuary   总被引：2，自引：0，他引：2  

Rita B. Domingues  Tnia P. Anselmo  Ana B. Barbosa  Ulrich Sommer  Helena M. Galvo 《Estuarine, Coastal and Shelf Science》2011,91(4):282

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Freshwater seepages and ephemeral macroalgae proliferation in an intertidal bay: II. Effect on benthic biomass and metabolism     

Aline Migné  Vincent Ouisse  Cédric Hubas  Dominique Davoult 《Estuarine, Coastal and Shelf Science》2011

Intertidal soft-sediments biomass and metabolism are naturally heterogeneous in time and space at different scales. Particular perturbations such as freshwater seepages and seasonal proliferation of ephemeral macroalgae can intermittently and/or locally create additional variability in these systems. Since the impacts of such environmental stresses on natural processes are not well understood, the hypothesis that they would affect the functioning of the benthic system was tested. An intertidal bay whose structure and functioning has been previously described and where a carbon budget has been calculated, was chosen. The results showed that the metabolism of the intertidal sediments was greatly impacted by the above perturbations. Freshwater seepage increased meiofauna and microalgae biomasses and enhanced the total benthic metabolism (increasing community respiration and gross primary production until 4 and 2 fold respectively) without altering its seasonal trend. Ephemeral macroalgae proliferation had a more important effect on the total benthic metabolism, increasing community respiration and gross primary production 8 and 12 fold respectively and leading to a change in the seasonal trend.  相似文献   

Secondary production in a Laminaria hyperborea kelp forest and variation according to wave exposure     

Kjell M. Norderhaug  Hartvig Christie 《Estuarine, Coastal and Shelf Science》2011

The secondary production of mobile invertebrate fauna in the Laminaria hyperborea (Gunn.) Foslie kelp forest increases with wave exposure level. This faunal group has a key function in transferring kelp carbon to higher levels in the food web. By using a size-frequency method the calculated production was 68 (±18) g D.W. m⁻² yr⁻¹ (±S.E.) at low, 250 (±57) at medium and 308 (±64) at high exposure levels. The calculations included 30 macrofauna species, which accounted for 96% of the specimens registered, with Gastropods, amphipods and bivalves being the most abundant taxa. The calculated secondary production is high, but comparable to that previously reported from other macrophyte systems and was 3%, 8% and 8% of the total primary production at low, medium and high exposure levels, respectively. Our results indicate that large quantities of Laminaria kelp are exported from the system, although the production of sessile animals was not taken into account. The most important factor in determining faunal densities and secondary production was probably habitat size but at low exposure levels the percentage of egg-carrying crustacean females and juveniles were lower than at medium and high exposure levels, thereby indicating lower fitness for animals at low exposure stations.  相似文献