Warm‐temperate,marine, carbonate sedimentation in an Early Miocene,tide‐influenced,incised valley; Provence,south‐east France     

Noel P. James  Margaret J. Seibel  Robert W. Dalrymple  David Besson  Olivier Parize 《Sedimentology》2014,61(2):497-534

The Saumane‐Venasque compound palaeovalley succession accumulated in a strongly tide‐influenced embayment or estuary. Warm‐temperate normal marine to brackish conditions led to deposition of extensive cross‐bedded biofragmental calcarenites. Echinoids, bryozoans, coralline algae, barnacles and benthic foraminifera were produced in seagrass meadows, on rocky substrates colonized by macroalgae and within subaqueous dune fields. There are two sequences, S1 and S2, the first of which contains three high‐frequency sequences (S1a, S1b and S1c). Sequence 1 is largely confined to the palaeovalley with its upper part covering interfluves. Each of these has a similar upward succession of deposits that includes: (i) a basal erosional surface that is bored and glauconitized; (ii) a discontinuous lagoonal lime mudstone or wackestone; (iii) a thin conglomerate generated by tidal ravinement; (iv) a transgressive systems tract series of cross‐bedded calcarenites; (v) a maximum flooding interval of argillaceous, muddy quartzose, open‐marine limestones; and (vi) a thin highstand systems tract of fine‐grained calcarenite. Tidal currents during stages S1a, S1b and S1c were accentuated by the constricted valley topography, whereas basin‐scale factors enhanced tidal currents during the deposition of S2. The upper part of the succession in all but S1c has been removed by later erosion. There is an overall upward temporal change with quartz, barnacles, encrusting corallines and epifaunal echinoids decreasing but bryozoans, articulated corallines and infaunal echinoids increasing. This trend is interpreted to be the result of changing oceanographic conditions as the valley was filled, bathymetric relief was reduced, rocky substrates were replaced as carbonate factories by seagrass meadows and subaqueous dunes, and the setting became progressively less confined and more open marine. These limestones are characteristic of a suite of similar cool‐water calcareous sand bodies in environments with little siliciclastic or fresh water input during times of high‐amplitude sea‐level change wherein complex inboard antecedent topography was flooded by a rising ocean.  相似文献   

A Fresh Look at the Geobiology & Sedimentary Environments of the Hypersaline Great Salt Lake,USA     

Kathleen NICOLL 《《地质学报》英文版》2014,88(Z1):94-95

正1 Introduction The Great Salt Lake(GSL)is the defining hydrological feature of the Great Basin,North America’s largest desert--and it is the largest waterbody in the western USA.Despite the early(Eardley,1938)recognition of"bioherms,"algal layers,and mats covering hundreds of square km of lake area,these features have not been the  相似文献   

Seasonal change of ice algal and phytoplankton assemblages in the Nella Fjord near Zhongshan Station, East Antarctica     

He Jianfeng  Chen Bo 《极地研究(英文版)》2000,11(2)

The ice algal and phytoplankton assemblages were studied from Nella Fjord near Zhongshan Station, East Antarctica from April 12 to December 30, 1992. Algal blooms occurred about 3 cm thick on the bottom of sea ice in late April and mid November to early December respectively, and a phytoplankton bloom appeared in the underlying surface water in mid December following the spring ice algal bloom. The biomass in ice bottom was 1 to 3 orders of magnitude higher than that of surface water. Amphiprora kjellmanii, Berkeleya sp., Navicula glaciei, Nitzschia barkelyi, N. cylindrus /N. curta, N. lecointei and Nitzschia sp. were common in the sea ice temporarily or throughout the study period. The biomass in a certain ice segment was decreased gradually and the dominant species were usually succeeded as the season went on. Nitzschia sublineata and Dactyliosolen antarctica were two seasonal dominant species only observed in underlying water column. The assemblages between bottom of ice and underlying surface water were different except when spring ice algae bloomed. The evidence shows that the ice algal blooms occurred mainly by in situ growth of ice algae, and the phytoplankton bloom was mostly caused by the release of ice algae.  相似文献   

Phytoplankton dynamics associated with the monsoon in the Sulu Sea as revealed by pigment signature   总被引：2，自引：0，他引：2  

Meguru Miki  Neelam Ramaiah  Shigenobu Takeda  Ken Furuya 《Journal of Oceanography》2008,64(5):663-673

Phytoplankton dynamics during the northeast monsoon was investigated in the Sulu Sea from algal pigment analysis. We visited the Sulu Sea in February 2000, a mid period of the northeast monsoon, and in November and December 2002, the beginning of the northeast monsoon. SeaWiFS images showed generally low concentrations of surface chlorophyll a (Chl a) during the southwest monsoon and higher concentrations with several peaks during the northeast monsoon. In the beginning of the northeast monsoon, subsurface chlorophyll maxima (SCM) occurred, where vertical variation in class-specific composition as estimated from pigment signatures was prominent. Prochlorococcus, cyanobacteria, prymnesiophytes and crysophytes were important groups above the SCM, and the contribution of cyanobacteria to Chl a became much lower at and below the SCM. Contributions of chlorophytes and prasinophytes to Chl a generally showed maxima near the SCM. This distribution was accompanied by vertical changes in the concentration of photoprotective pigments relative to photosynthetic accessory pigments. During the mid northeast monsoon, the upward supply of nutrients was probably enhanced at some stations due to vertical mixing, and as a consequence diatoms dominated in the upper 100 m water column of these stations, and other eukaryotic flagellates including prymnesiophytes, chrysophytes and cryptophytes were secondary major components of the community. The elevation of Chl a concentration and changes in phytoplankton community during the northeast monsoon likely influence the variation in biological production at higher trophic levels in the Sulu Sea.  相似文献   

鄂尔多斯盆地东缘奥陶系马家沟组四段豹斑状云质灰岩特征及成因: 以关家崖剖面为例^*          下载免费PDF全文

许杰  肖笛  苏文杰  晏巍  钟寿康  杨鸣一  杨梦颖  谭秀成 《古地理学报》2022,24(2):261-277

鄂尔多斯盆地东缘中奥陶统马家沟组发育豹斑状云质灰岩,因其分布广泛、成因复杂以及具有重要的油气储集意义而长期受到关注。文中以山西省兴县关家崖剖面马家沟组四段顶部为例,依据宏观、微观岩石学特征,结合碳氧稳定同位素、原位激光剥蚀的微量稀土元素等地球化学分析手段,分析了豹斑状云质灰岩的特征及其成因。研究表明,豹斑状云质灰岩的特征为: (1)常发育于(含颗粒)泥晶灰岩中,且向上白云石化程度增强,云质斑块内常伴有针状或板条状石膏假晶;(2)按产状可大致分为水平、斜交和不规则花斑3种类型,分别对应于向上变浅序列的下部、中部和上部,序列顶部多见近原地角砾化;(3)基质灰岩与云质斑块的δ¹³C、δ¹⁸O值较同期海水略显负偏,顶部不规则云质斑块负偏程度最大;(4)“豹斑”与基质灰岩均具有较低的Mn、Sr、Ba等含量和低Mn/Sr值;(5)“豹斑”的ΣREE含量较基质灰岩略低,且皆表现为轻稀土富集、重稀土亏损的稀土配分模式,δCe微弱负异常,δEu无异常。依据上述结果,推测关家崖剖面马四段豹斑状云质灰岩产状受到生物扰动和高频海平面驱动的早成岩期岩溶耦合控制,序列由下至上耦合改造由弱变强,形成下—中部以岩溶影响较小的水平和斜交虫迹为特征、上部叠合岩溶强改造形成不规则花斑的垂向序列组合;早成岩期的暴露岩溶不仅叠合改造生物潜穴,而且蒸发浓缩的有限重卤水沿叠合优势通道优先交代孔渗条件更好的区域,至埋藏时期白云石化作用进一步加强,从而形成了区内类型多样的豹斑状云质灰岩。研究结果还揭示出沉积期微地貌控制的早成岩期岩溶作用是马四段这类特殊的豹斑状云质灰岩或豹斑状云岩储集层形成的关键,且在很大程度上控制了这类储集层的分布,这一认识可为高频暴露驱动的早成岩期岩溶研究提供新的材料。  相似文献   

海上顶部双驱动联动隔水管钻探取心技术          下载免费PDF全文

张会寅  田烈余  林康  郭武  李占钊  杨楠  王世栋 《探矿工程》2022,49(6):110-115

我国南海海域分布着大量礁灰岩地层,这种地层具有原生孔隙大、压缩性强、容易变形、强度小等特点,因此易渗透、易破碎、易坍塌。在岛礁上钻探也常常出现断钻、垮孔、埋钻等事故。对于海洋礁灰岩地层钻探,不仅要克服陆地上面临的问题,还需要面对更为复杂的海洋环境。为解决海上特殊地层取心困难问题,基于船载无隔水管钻探系统,开发了海上顶部双驱动联动隔水管钻探取心技术。该钻探取心技术方案在西沙海域4个不同的站位进行了海洋钻探试验。试验结果表明,该技术可实现高效率、高岩心采取率的海上礁灰岩取心目的,取心深度可达130.75 m,具有广阔的推广前景。  相似文献   

石灰土中秸秆还田降解率及其对土壤肥力的影响   总被引：1，自引：0，他引：1  

黄芬  韦红群  曹建华 《资源与生态学报(英文版)》2015,(4)

石灰土具有高的有机碳的积累,但营养成分的供给速率偏低,导致土壤贫瘠。本文通过室内模拟实验,研究相同来源玉米秸秆在岩溶土与非岩溶土中的降解情况,对秸秆降解率、土壤理化性质、土壤肥力等进行动态检测,结果表明：（1）总体上岩溶土秸秆降解速率比非岩溶土快。秸秆降解速度最快主要集中在最初60天,之后呈缓慢上升趋势,到98天基本达到平衡。非岩溶土降解峰值出现时间为第42天,岩溶土为第28天,峰值出现时间前者比后者滞后14天。总降解时间持续160天,岩溶土降解率为77%,非岩溶土为75%。（2）秸秆降解期间,土壤pH值前期有下降的趋势,后期慢慢回升,这与秸秆降解过程中不同时期降解产物变化规律相吻合。秸秆还田可以提高土壤肥力,其中速效氮和速效钾含量增加非常明显。（3）与岩溶土相比,全量检测结果显示各肥力指标在非岩溶土含量低,但升幅百分比高;有效态检测结果显示非岩溶土速效磷和速效钾含量高。说明秸秆还田一些营养元素有效态在非岩溶土中更易于释放,而岩溶土由于其土壤质地的特殊性,许多养分被土壤粘土矿物牢固结合,营养元素供给速率慢,但因此也易于养分全量的累积。  相似文献   

川北早寒武世碳酸盐岩台缘斜坡沉积特征及变形构造形成机制探讨   总被引：2，自引：2，他引：0       下载免费PDF全文

沈骋  谭秀成  李凌  施开兰  苏成鹏  连承波  黎虹玮  肖笛 《古地理学报》2015,17(3):321-334

基于对川北米仓山西部旺苍县鼓城乡唐家河下寒武统仙女洞组露头剖面的观察与镜下分析发现,仙女洞组下段由生物碎屑泥晶灰岩(L)、粉砂质泥岩(M)、似瘤状砾屑灰岩(L')、角砾灰岩(R)、藻凝块灰岩(A)和含生屑钙质砂岩(S)组合而成,其以角砾灰岩、似瘤状砾屑灰岩和藻凝块灰岩为特征,且发育异地岩块和滑塌变形构造。进一步分析认为:L-M岩石组合为正常的斜坡环境低能沉积;L'-R岩石组合中的角砾灰岩为上斜坡生物灰泥丘崩坍滑动至下部而形成的,似瘤状砾屑灰岩可能是由于L-M岩石组合快速沉积导致沉积物失稳滑动变形、上斜坡生物灰泥丘崩落角砾致使的差异压实和滑动、以及后期物质成分差异引起的压溶作用等共同作用的结果,从而使灰质层发生破碎并被泥质包围形成断续的砾屑状,甚至轻微的位移,进而形成条带特征不明显的杂乱变形构造;微生物岩(Mb)组合为上斜坡的灰泥丘沉积;S-M岩石组合为斜坡上部的浊流沉积。根据上述分析结果建立米仓山西部仙女洞组碳酸盐岩台缘斜坡沉积模式,表明仙女洞组沉积早期米仓山西部存在台缘斜坡相沉积。  相似文献   

DISTRIBUTIVE　TENDENCY　OF　ELEMENT　CONCENTRATIONS　IN　LIMESTONE　SOILS　IN　EASTERN　CHINA     

温琰茂  曾水泉  潘树荣  罗毓珍 《中国地理科学(英文版)》1995,5(4):316-324

ＤＩＳＴＲＩＢＵＴＩＶＥＴＥＮＤＥＮＣＹＯＦＥＬＥＭＥＮＴＣＯＮＣＥＮＴＲＡＴＩＯＮＳＩＮＬＩＭＥＳＴＯＮＥＳＯＩＬＳＩＮＥＡＳＴＥＲＮＣＨＩＮＡＷｅｎＹａｎｍａｏ（温琰茂）；ＺｅｎｇＳｈｕｉｑｕａｎ（曾水泉）；ＰａｎＳｈｕｒｏｎｇ（潘树荣）；Ｌｕｏ...  相似文献   

Palaeomagnetism of stalagmites (speleothems) in SW Japan     

Hayao Morinaga  Hiroo Inokuchi  Katsumi Yaskawa 《Geophysical Journal International》1989,96(3):519-528

  相似文献