川北旺苍唐家河剖面仙女洞组灰泥丘沉积特征及造丘环境分析

目前川北地区早寒武世微生物藻与古杯参与的生物礁(丘)发育特征存在较大争议。通过实测剖面与镜下分析,川北旺苍县鼓城乡唐家河剖面仙女洞组发育三期灰泥丘。对该剖面灰泥丘沉积特征进行精细研究认为:第一期灰泥丘发育在滑塌角砾灰岩之上,造丘生物主要为枝状和房室状附枝藻,主要岩性为砾屑灰岩、藻格架凝块灰岩和含云生物碎屑灰岩,发育丘基、丘核、丘盖和丘翼,后期演化为钙质砂泥岩结束生长。第二期生物丘发育在鲕粒滩间生屑灰岩之上,造丘生物主要为肾状藻,次为附枝藻,主要岩性为生物碎屑灰岩、藻格架凝块灰岩、漂浮砾岩和亮晶鲕粒灰岩,纵向上发育丘基、丘核、丘坪、丘盖和丘翼,最终再度沉积鲕粒灰岩。第三期灰泥丘发育在藻叠层灰岩之上,造丘生物为古杯和微生物藻,岩性主要为古杯灰岩、生物碎屑泥晶灰岩、藻格架凝块灰岩和藻叠层灰岩,发育丘基、丘核和丘盖。进一步分析三期灰泥丘的成丘环境认为第一期灰泥丘属于台缘斜坡环境内的斜坡灰泥丘低能沉积,经历三个演化阶段;第二期属于台地边缘灰泥丘,经历四期演化阶段;第三期为台缘高能鲕粒滩向陆一侧能量相对较低的台缘古杯灰泥丘沉积,经历三个演化阶段。剖面中灰泥丘多与鲕粒滩共存,构成丘滩复合体,为后期研究储集性能和油气富集关系具有重要的油气地质意义。     

北京西山下苇甸中寒武统张夏组生物丘发育特征及其地质意义

北京西山下苇甸剖面寒武系地层出露完整,中寒武统张夏组底部和顶部发育两期生物丘地层.通过野外观察及薄片鉴定发现,张夏组底部发育的生物丘为凝块石生物丘,顶部发育的为叠层石生物丘,两期生物丘的造丘生物主要为藻类.凝块石生物丘生长在低能的潮下带环境,而叠层石生物丘则形成于海水能量较高的潮间带或潮下带上部.不同的沉积环境造成了两期生物丘内部结构的差异,主要体现在造丘生物的排列方式上.根据该剖面两期生物丘的特征,总结了生物丘的发育模式,并对其地质意义进行了探讨.     

四川盆地北部中二叠统茅口组碳酸盐岩斜坡沉积及其油气勘探意义

在露头分析的基础上,结合钻井和地震资料,提出四川盆地中二叠统茅口组发育碳酸盐岩斜坡相沉积。其典型岩性为深灰色砾屑灰岩,砾屑成分以生物碎屑泥晶灰岩为主,局部地区见亮晶生物碎屑灰岩、造礁生物和重力滑动变形构造,砾径变化范围大;次要岩性为含钙屑浊积岩的深灰色薄层泥晶灰岩。中二叠统从栖霞组开阔台地相到茅口组斜坡相的演化,说明茅口组沉积时期构造活动加强,导致盆地北部及其他区域都有可能发生相带的分异。茅口组地震剖面上的厚度由南向北明显增厚,且具有楔形反射的特征,印证了盆地北部斜坡相的南区发育有台地边缘高能相带,这一认识有利于对四川盆地茅口组构造-岩相古地理的重建以及有利相带和储层的预测。     

大连金州湾寒武系毛庄组微生物碳酸盐岩生物丘复合体

寒武纪苗岭世早期的毛庄组沉积时期,华北地台围绕着西北部的古陆分布着两个沉积相带,靠近古陆的是局限潮坪相带,远离古陆的是开阔潮坪相带,前者以海侵体系域的干旱红层或海岸萨布哈沉积与高水位体系域的潮坪相白云岩沉积序列为特征,后者则以海侵体系域的潮坪相砂泥岩与开阔海台地相(潮下坪)灰岩沉积序列为特征;大连金州湾剖面的毛庄组,属于远离古陆的开阔潮坪相带的产物,在其高水位体系域中为一套夹有鲕粒灰岩的叠层石与均一石生物丘灰岩,组成一个特别的生物丘复合体。以下特征表明,这个微生物碳酸盐岩生物丘复合体代表着一个较为罕见的蓝细菌主导的微生物席形成的微生物碳酸盐岩的典型实例:①在生物丘复合体第一个单元的大型柱状和穹隆状砂泥质叠层石中发现孢网菌状组构,说明了这些叠层石属于蓝细菌微生物席的钙化作用产物;②在第二个单元均一石灰岩生物丘中,见到少量丝状蓝细菌鞘化石,表明均一石可能为较厚的蓝细菌微生物席的钙化作用产物;③在小型柱状叠层石组成的顶部单元中,保存较好的蓝细菌泥晶纹层、以及充填在叠层石柱体之间的基质中的蓝细菌团块,较为特征地说明了这些小型柱状叠层石是蓝细菌所主导的微生物席的建造物;④在鲕粒灰岩组成的第三个单元中,鲕粒边缘中的丝状蓝细菌鞘化石,表明了鲕粒的蓝细菌生物膜成因。因此,毛庄组生物丘复合体构成了一个壮观的沉积学现象,成为窥视"显生宙早期第一幕蓝细菌钙化作用事件"的典型实例。     

四川盆地中二叠世栖霞期微生物丘及其对沉积环境的启示

在四川盆地华蓥溪口地区首次发现了发育在二叠纪栖霞期的微生物灰泥丘,该灰泥丘以灰泥作为支撑结构;参与建筑的生物主要是菌类微生物,其次为多门类无脊椎动物,如有孔虫、腕足等,但生物物种分异度较低,丰度较高;岩石类型主要为生屑泥晶灰岩以及凝块石等;灰泥丘可划分为丘基、丘核及丘翼。根据地化分析,华蓥溪口栖霞组剖面野外样品古盐度Z值均122,且δ~(13)C0;δ~(18)O变化在-6.33‰~-4.22‰,向上δ~(18)O总体为正偏移,表明海平面逐渐下降。恢复的古水温在33.60~24.26℃。V/(V+Ni)比值为0.51228,U/Th比值为8.28205;指出华蓥溪口地区处于水体较深,水动力较弱,温度较高的超咸缺氧环境。这种环境有利于微生物丘的发育,并影响了造礁生物的发育和生长,是导致栖霞期没有发育骨架礁的原因之一。     

城口-鄂西海槽西侧晚二叠世碳酸盐台地边缘发育新认识

基于城口-鄂西海槽西侧地区详细的露头调查、钻井资料分析,结合古生物、古生态以及地层对比,对研究区晚二叠世长兴期碳酸盐台地边缘沉积相及其演化进行详细解剖,得出区内台地边缘骨架礁-凝块石灰泥丘生态-沉积演化对碳酸盐台地边缘构筑具有积极作用的认识。研究表明区内长兴期碳酸盐台地边缘礁滩经历了三个演化阶段:第一阶段,碳酸盐台地边缘坡折带尚未形成,台地边缘礁滩欠发育,且台地前缘斜坡坡度较缓;第二阶段,碳酸盐台地镶边开始形成,发育骨架礁及滩相沉积,垂向上构成进积-加积组合序列,台地前缘斜坡变陡;第三阶段,微生物逐渐占据后生造礁生物生态空间,发育台地边缘凝块石灰泥丘,与上覆台地边缘滩构成垂向加积组合序列,促进了台地边缘正向地貌的发育,使区内台地边缘更加陡峭,台地前缘斜坡发育滑塌角砾岩。造礁生物生态演替及相对海平面变化共同影响并控制长兴期碳酸盐台地边缘构筑过程。     

四川盆地南部志留系碳酸盐灰泥丘成因与储集性

灰泥丘与生物礁具有相似的地震反射特征,但两者的形成环境及内部组成完全不同。缓坡环境和较弱的水动力环境是灰泥丘形成的两个重要条件,灰泥丘主要由微生物所建造。川南志留系主要发育中—下志留统,自下而上划分为龙马溪组、石半栏组、韩家店组和秀山组,其中石牛栏组主要为碳酸盐岩,岩性较硬,上下地层相对为软岩层,构成“两软夹一硬”的地晏剖面结构。灰泥丘主要发育在石牛栏组,属于典型的开阔台地内缓坡泥丘。灰泥丘储层主要发育在丘翼和丘顶微相中,经历了胶结作用、重结晶作用、白云石化作用、压实作用和溶解作用等,其中胶结作用使丘翼储集物性变差,而白云石化作用使丘顶物性变好。因此丘翼灰岩被胶结后储集性能普遍较差,平均孔隙度1％～2％,渗透率(3～5)×10~(-3)μm~2;丘顶白云石化后储集物性普遍较好,孔隙度4％～5％,渗透率(6～8)×10~(-3)μm~2,构成了川南地区相对有利的天然气储层。     

京西地区寒武系凤山组地球化学特征及古环境意义

为重建京西地区芙蓉世古海洋环境演化、更好地理解沉积环境对碳酸盐岩沉积的影响,选取下苇甸剖面凤山组为研究对象,在沉积环境分析基础上,运用碳-氧同位素、主-微量元素和稀土元素等分析手段,探讨地球化学特征对沉积古环境的指示意义。下苇甸剖面凤山组主要发育泥岩、薄板状泥晶灰岩、薄板状泥晶灰岩与泥岩互层、灰泥丘、生物扰动藻黏结泥晶灰岩、砾屑灰岩、粉屑砂屑灰岩和白云质灰岩8种岩相类型,垂向上表现为多个向上变浅的米级旋回,构成了一个三级层序,其中海侵体系域以潮下低能带沉积为主,高位体系域以潮下高能带-潮间高能带藻席沉积为主。凤山组碳酸盐矿物含量以方解石为主,Al和Si等陆源碎屑元素含量较低。δ13C_car介于-0.71‰~1.51‰,反映沉积期海平面逐渐上升、末期短暂下降的变化趋势;Ce/Ce*和氧化还原敏感微量元素特征表明凤山期沉积水体以弱氧化性为主。     

华北地台是晚寒武世沉积层序中生物丘构造研究

华北古克拉盆地中晚寒武纪沉积层序中发育的生物丘沉积构造的生物组成有隐藻类，钙藻类和非藻类多细胞生物，它们构成了隐藻凝块石生物丘简单类型和复合的五种生物丘类型。生物丘的发生，发展，灭亡过程经历了奠基期，拓殖期，泛殖期及消亡期等四个阶段，每阶段都爱相对海平面变化的控制，它决定了丘体的大小，生物组成及内部结构及周期。     

贵州早二叠世岩相古地理研究

根据岩石组合,古生物组合,沉积构造及剖面结构,将贵州早二叠世沉积相划分为四个相区、九个相带,它们是: 1.滨岸漫滩沼泽相 Ⅰ.陆地边缘相区 2.潮汐泥坪相 3.潮坪沼泽相 4.半局限台地相带 Ⅱ.碳酸盐台地相区 5.开阔台地相带 6.较深水台沟相带 7.碳酸盐合地边缘生物滩相带 Ⅲ .碳酸盐台地边缘相区8.碳酸盐台地边缘生物礁相带 　 Ⅳ.浅海盆地相区 9.浅海陆棚相带。 贵州早二叠世经历了一个完整的海进海退旋回,茅口早期是最大的海侵期,就沉积的演化而言,它大体经历了两个阶段。即第一阶段(栖霞早期)系清水和浊水混合的缓坡型沉积,其特征是:1.碳酸岩与碎屑岩共同发育;2.碳酸盐台地边缘礁滩相不发育。第二阶段(栖霞晚期至茅日晚期)为清水碳酸盐台地沉积,特征是:1.主要为碳酸盐岩,2.碳酸盐台地边缘生物滩礁带发育。     

藏西北三岔口地区泥瓮系生物礁特征及其意义

在羌塘西部的三岔口一带泥盆系拉竹龙组中发现规模较大的生物礁——台地前缘礁。下层礁体厚7．28m，上层礁体厚40.98m。两个礁体均为叠置礁，礁体由礁基、礁核、礁顶组成。剖面显示发育有礁前垮塌角砾、礁格架、礁间及礁后环境。泥盆纪生物礁的发现为羌塘盆地寻找油气资源提供了新思路。     

Submarine-spring controlled calcification and growth of large Rivularia bioherms, Late Pleistocene (MIS 5e), Gulf of Corinth, Greece

The cyanobacterium Rivularia haematites has calcified to form unusually large (up to 10 m high) bioherms in the Pleistocene Gulf of Corinth. Today R. haematites calcifies only in freshwater environments but these Gulf of Corinth bioherms have a brackish affinity, limited areal extent, and occur within marine deposits. Field relations and preliminary U-series dating suggest a marine isotope stage (MIS) 5e age for the bioherms. This age is compatible with published MIS 5e ages for corals in the marine sediments above the bioherms and is consistent with their current elevation based on average uplift rates. Bioherm growth during MIS 5e constrains their formation during a time of near sea-level highstand when the Gulf of Corinth was marine. Growth cavities in the bioherms are encrusted by brackish tolerant coralline algae. Field mapping of the MIS 5e highstand palaeoshoreline shows the bioherms grew in water <16 m deep. Mg contents of the bioherm calcites, and associated coralline algal skeletons, are both much lower than expected for marine MIS 5e carbonates. They are best explained if the calcites precipitated from brackish fluids with Mg/Ca ratios below 2, implying at least 60% input of freshwater with low Mg/Ca ratio. Sr isotopes confirm a strong input of groundwater that had partially equilibrated with Mesozoic limestones. The limited areal extent of the bioherms and their close association with karstified fault scarps suggest that they formed in shallow sea water where freshwater submarine springs delivered CaCO₃ saturated water that promoted rapid calcification of cyanobacteria. Rapid calcification and strong degassing of CO₂ from the spring water resulted in disequilibrium stable isotope compositions for the calcites.     

河北柳江盆地中晚寒武世藻类丘礁的演化

河北柳江盆地中晚寒武世藻类丘礁十分发育，并形成完好纵向演化序列。藻礁具有两个演化方向，其一是骨骼钙藻Ｅｐｉｐｈｙｔｏｎ向非骨骼蓝绿藻方向演化；其二是块状藻丘向厚层状叠层石礁方向演化。藻类丘礁的演化特征及其沉积相序揭示了该区中晚寒武世时从碳酸盐台地边缘斜坡至台缘浅滩和潮坪环境的演化历史。     

Lower Cambrian shelf and shelf margin buildups,Flinders Ranges,South Australia1

Carbonate buildups in the Flinders Ranges of mid-Early Cambrian age grew during a period of high archaeocyath diversity and are of two types: (1) low-energy, archaeocyath-sponge-spicule mud mounds, and (2) high-energy, archaeocyath-calcimicrobe (calcified microbial microfossil) bioherms. Mud mounds are composed of red carbonate mudstone and sparse to abundant archaeocyath floatstone, have a fenestral fabric, display distinct stromatactis, contain abundant sponge spicules and form structures up to 150m wide and 80 m thick. Bioherms are either red or dark grey limestone and occur as isolated small structures 2–20 m in size surrounded by cross-bedded calcarenites and calcirudites or as complexes of mounds and carbonate sands several hundreds of metres across. Red bioherms comprise masses of white Epiphyton with scattered archaeocyaths and intervening areas of archaeocyath-rich lime mudstone. Grey bioherms are complex intergrowths of archaeocyaths, encrusting dark grey Renalcis and thick rinds of fibrous calcite cement. The bioherms were prone to synsedimentary fracturing and exhibit large irregular cavities, up to 1.5 m across, lined with fibrous calcite. The buildups are isolated or in contiguous vertical succession. Mud mounds occur alone in low-energy, frequently nodular, limestone facies. Individual bioherms and bioherm complexes occur in high-energy on-shelf and shelf-margin facies. The two types also form large-scale, shallowing-upward sequences composed of basal (deep water) mud mounds grading upward into archaeocyath-calcimicrobe bioherm complexes and bioherms in cross-bedded carbonate sands. The uppermost sequence is capped by ooid grainstone and/ or fenestral to stromatolitic mudstone. The calcimicrobe and metazoan associations form the two major biotic elements which were to dominate reefs throughout much of subsequent Phanerozoic time.     

藏西北三岔口地区泥盆系生物礁特征及其意义

在羌塘西部的三岔口一带泥盆系拉竹龙组中发现规模较大的生物礁———台地前缘礁。下层礁体厚7.28m,上层礁体厚40.98m。两个礁体均为叠置礁,礁体由礁基、礁核、礁顶组成。剖面显示发育有礁前垮塌角砾、礁格架、礁间及礁后环境。泥盆纪生物礁的发现为羌塘盆地寻找油气资源提供了新思路。     

湘西花垣地区下寒武统清虚洞组生物丘钙藻形态群与环境群带的划分及意义

引言生物作为一种举足轻重的判别沉积环境的标志,已为广大沉积学者所公认。然而,这种标志是通过古生物与其有亲缘关系的现代生物的生活环境的对比及可靠的相标志互为验证而得到的。对于那些早已绝种而无法与现代生物生活环境参照对比的生物来说,研究形态群与环境的关系显得格外重要而有意义。作者自1986—1988年在湘西花垣地区的地质调研中,发现该区19个钙藻属种据其形态特征可以划分为四个群七个亚群。这些形态群在剖面上有某种规律性的排列分布,详细的研究又证实了这种排列分布与一定的沉积环境关系密切,从而作者厘定了“与一定的环境相     

Facies, geometry and geological significance of Late Ordovician (early Caradocian) coral bioherms: Lourdes Formation, western Newfoundland

Late Ordovician coral bioherms in the Lourdes Formation of western Newfoundland exhibit a complex mixing of architectural elements, including framework, boundstone and suspension deposits. The bioherms occur within a narrow (16 m) stratigraphic interval, and a prominent unconformity truncates the interval of bioherm growth and tops of many of the bioherms. The buildups developed along a carbonate ramp. They occur isolated and in groups, individuals in groups are aligned in parallel orientation. The sizes of the bioherms range from small (50–100 cm) coral piles to columnar and dome‐shaped masses (1–15 m); however, topographic relief was never more than ≈1 m. Bioherm construction reflects: (i) stacking of the tabulate coral Labyrinthites chidlensis, and less common stromatoporoids; (ii) accumulation of microbial‐stromatoporoid boundstone and suspension deposits within shelter cavities between corals; and (iii) detrital bioherm‐flank skeletal grainstone beds. Trypanites borings are common in the tops of coral heads. The bioherms exhibit three growth‐development stages: (i) seafloor stabilization, wherein rare, abraded coral colonies lie scattered within pelmatozoan/skeletal grainstone lenses; (ii) colonization, wherein corals (L. chidlensis), rare stromatoporoids (Labechia sp.), and other biota (bryozoans) produced a bioherm overlying the basal sediment base; and (iii) diversification, which is marked by a more diverse range of fauna and flora as well as occurrence of shelter‐cavity deposits. The diversification stage usually makes up more than 70% of a bioherm structure, and, in some defines multiple periods of start‐up and shut‐down of bioherm growth. The latter is defined by bored omission surfaces and/or deposition of inter‐bioherm sediment. The Lourdes bioherms have a similar ecological structure, biotic diversity and depositional environment to patch reefs in the equivalent Carters Limestone in Tennessee. The mixture of coral stacking and boundstone as architectural elements identify an Early Palaeozoic transition of reef‐design development along shallow‐water platforms that began to displace the muddy (boundstone, bafflestone) carbonate buildups more typical of the Early and Middle Ordovician time.     

埋藏反馈及其对生物礁发育的作用

底栖生物与基底之间的关系十分密切,基底的性质直接影响生物的生活特性及分布。死亡生物的硬体骨骼大量堆积,将改变底栖生物生态环境的基底性质,产生埋藏反馈作用,从而使底栖生物群落发生演替。生物礁的初期发育阶段直接受到埋藏反馈的影响。本文结合国内外有关资料,系统论述了埋藏反馈及其对生物礁发育的影响。     

Cryptalgal-metazoan bioherms of early Ordovician age in the St George Group, western Newfoundland

Bioherms are common in the St George Group, a sequence of shallow-water carbonate rocks deposited on the western continental shelf of Iapetus Ocean. They range from small heads and metre-sized mounds to extensive banks and complexes many metres thick and hundreds of metres in lateral extent. The cores of these bioherms are principally composed of thrombolites (unlaminated, branching, columnar stromatolites), structures quite distinct from laminated stromatolites which are common in intertidal beds. Associated with thrombolites is a diverse fauna of burrowing invertebrates, trilobites, nautiloids, pelmatozoans, brachiopods, gastropods, rostroconchs and archaeoscyphiid sponges. On the basis of framework-building components, three main bioherm types are distinguished: (1) thrombolite mounds, (2) thrombolite-Lichenaria or -sponge mounds and (3) thrombolite-Lichenaria-Renalcis reef complexes. The framework of the last is the most complex, with abundant cavities and a demonstrably uneven growth surface of thrombolites, corals and free-standing Renalcis heads, walls and roofs. Some cavities were active sediment conduits while others were protected, their roofs draped with Renalcis and their walls coated by cryptalgal laminites. These bioherms possess the attributes of shallow-water ecologic reefs. They span a critical time gap in the development of reefs, the transition period from algal-dominated bioherms of the Precambrian and Cambrian to the metazoan-dominated bioherms of the Middle Ordovician and remaining Phanerozoic.