黄骅坳陷埕北断坡不整合特征与油气成藏

黄骅坳陷埕北断坡处于歧口凹陷向埕宁隆起过渡的斜坡带上,发育多个不整合,这些不整合对该区的油气成藏起重要作用。利用地震资料,在剖面上将不整合划分为5种类型：褶皱不整合、断褶不整合、削截不整合、超覆不整合、平行不整合。其中平行不整合分布在凹陷区,褶皱不整合分布在基底,断褶不整合分布在大断裂下降盘,削截不整合分布在大断裂上升盘,而超覆不整合多分布在隆起斜坡区;利用测井资料,在纵向上将不整合划分为3层结构：不整合面之上岩石、风化粘土层及半风化岩石,由于每层结构的岩性与厚度不同,形成ACE型、ADE型、BCE型和BDF型4种岩性配置模式。不整合构成埕北断坡油气侧向运移的重要通道,同时在其之上形成超覆不整合油气藏,在其之下依靠风化粘土层遮挡形成削截不整合与褶皱不整合油气藏。勘探证实,研究区众多油气显示或油气藏均位于不整合面上、下50 m范围内。开展不整合与油气成藏关系研究,将拓宽黄骅坳陷隐蔽油气藏的勘探空间,对我国东部油气资源挖潜具有重要的理论与实践意义。     

西昆仑北缘新元古代片麻状花岗岩锆石SHRIMP年龄及其意义

在西昆仑北缘早前寒武纪变质地层中,笔者等识别出大量不同时代的片麻状花岗岩,其中包括新元古代片麻状花岗岩。获得最新的新元古代片麻状花岗岩的单颗粒锆石SHRIMP年龄为815±57Ma,片麻状花岗岩的岩石学特征反映它们形成于裂解构造背景,结合对区域上新元古代地层及中元古代末期构造事件的研究,笔者认为新元古代片麻状花岗岩反映了古塔里木板块作为Rodinia超大陆一员发生裂解的时间,这对研究古塔里木板块在Rodinia超大陆中的位置及中国Rodinia超大陆裂解的研究提供了重要的地质依据。     

Thermal history of the Rio Muni (West Africa)–NE Brazil margins during continental breakup

We document the thermal record of breakup of the conjugate Rio Muni (West Africa) and NE Brazil margins using apatite fission track analysis, vitrinite reflectance data and stratigraphic observations from both margins. These results permit determination of the timing of four cooling episodes, and the temperature of samples at the onset of each episode. All samples are interpreted to have experienced higher temperatures in the geological past due to i) elevated basal heatflow (palaeogeothermal gradient in Rio Muni-1 well decaying from 58 °C/km during the Mid Cretaceous to 21.5 °C/km in the Late Cenozoic) and ii) progressive exhumation from formerly greater burial depth. A well constrained history of changing palaeogeothermal gradient allows for much more precise quantification of the thickness of eroded section (exhumation) than if a constant heatflow is assumed. Cooling episodes identified from the palaeotemperature data at 110–95 Ma (both margins) and 85–70 Ma (Rio Muni only) coincide with major unconformities signifying, respectively, the cessation of rifting (breakup) and compressional shortening that affected the African continent following the establishment of post-rift sedimentation (drift). The interval between these separate unconformities is occupied by allochthonous rafts of shallow-water carbonates recording gravitational collapse of a marginal platform. The rift shoulder uplift that triggered this collapse was enhanced by local transpression associated with the obliquely divergent Ascension Fracture Zone, and thermal doming due to the coeval St Helena and Ascension Plumes. The data also reveal a c.45–35 Ma cooling episode, attributed to deep sea erosion at the onset of Eo-Oligocene ice growth, and a c.15–10 Ma episode interpreted as the record of Miocene exhumation of the West African continental margin related to continent-wide plume development. Integration of thermal history methods with traditional seismic- and stratigraphy-based observations yields a dynamic picture of kilometre-scale fluctuations in base level through the breakup and early drift phases of development of these margins. Major unconformities at ocean margins are likely to represent composite surfaces recording not only eustasy, but also regional plate margin-generated deformation, local ‘intra-basinal’ reorganization, and the amplifying effect of negative feedbacks between these processes.     

滇西施甸地区晚泛非运动的地层学和岩石学响应

保山地块的寒武系露头少,研究范围有限。长期以来,地学界对寒武系与奥陶系之间的接触关系存在较大争议,有人认为是整合接触,有人认为是假整合接触,囿于过去的工作精度,目前尚无定论。近年来,在保山施甸地区开展1∶5万区调工作时发现,区内普遍缺失早奥陶世沉积,仅在施甸半坡一带有中奥陶统,在大寨一带,中上奥陶统蒲缥组直接平行不整合在上寒武统保山组之上,结合晚寒武世—早奥陶世业已存在的岩浆活动,认为这是晚泛非运动的远程响应。     

准噶尔盆地陆梁隆起不整合面与油气运聚关系

准噶尔盆地陆梁隆起不整合面十分发育，且与油气运聚关系非常密切：二叠系、三叠系底不整合面是该区侏罗纪末成藏的主控因素，侏罗系底不整合面是深部油气进入该系的有利通道，而白垩系底不整合面又是油气顺利从侏罗系进入白垩系的必要条件。研究区的不整合面有褶皱、断褶、超覆、削截、平行5种类型，各种类型的不整合面对研究区油气运聚作用也有着差异，其中断褶不整合面对油气的垂向运移与聚集作用最大，是研究区最为典型的油气成藏方式。不整合面的分布具有差异性、继承性、迁移性，三性对油气的演化和分配有着影响作用。     

贵州独山中深盆统不整合的发现及其意义

黔南中泥盆统独山组鸡窝寨段底部存在的古风化壳层和其之上的底砾岩,为一次地亮相对上升、海平面下降的上升运动（独山抬升）,表明独山组内存在着沉积间断。建议将此古风化壳之上的原＂独山组鸡窝寨段＂修订为＂鸡窝寨组＂,代表中泥盆世晚期较独山组更大海侵的以碳酸盐岩为主的沉积。     

Palaeosols and palaeokarst beneath subaerial unconformities in an Upper Devonian isolated reef complex (Judy Creek), Swan Hills Formation,west‐central Alberta,Canada

Subaerial unconformities are used widely for palaeoenvironmental and palaeogeographic reconstructions, sequence stratigraphy and petroleum reservoir assessments. Recognition and interpretation of these unconformities, particularly those with associated palaeosols, may be problematic in Lower and Middle Palaeozoic carbonate successions because of the collective effect of limited land plant development, superficial similarities between some pedogenic and marine features, and overprinting by later diagenesis. The isolated Judy Creek reef complex in the Lower Frasnian Swan Hills Formation in west‐central Alberta, Canada, contains two subaerial unconformities, R0.5 and R4, which formed as a consequence of relative sea‐level falls of at least regional scale. Deposits beneath these unconformities have distinctive palaeosol and palaeokarst features. The lower unconformity, R0.5, occurs at the top of a progradational reefal phase of stromatoporoid rudstones–floatstones and peloidal packstones–grainstones and has been recognized in at least one other isolated Swan Hills reef complex (Snipe Lake). Palaeosol–palaeokarst profiles beneath this unconformity extend as deep as ca 2 m below the unconformity. These profiles are characterized by the presence of small rhizoliths, laminar calcretes, ferroan dolomite glaebules, desiccation cracks, breccias, green shale and solution vugs. The upper unconformity, R4, occurs at the top of a backstepping phase of reef growth and has been correlated widely between isolated reefs and carbonate banks on both the western and eastern shelves of the Central Alberta Basin. Palaeosol–palaeokarst profiles, extending as deep as ca 9·5 m beneath the R4 unconformity, are distinguished by abundant, sub‐horizontal desiccation cracks filled with green shale, occurring in peloidal wackestones–packstones. Comparison of the R0.5 and R4 profiles indicates that the major intrinsic controls on the development and modification of the profiles are parent‐material lithology, particularly the prior degree of induration and particle size; the low topographic relief at the top of the reef interior; and limited vegetation of the exposed reef top due to unfavourable growth conditions and geographic isolation. In addition to climate, the major extrinsic controls are the extent of relative sea‐level fall, estimated to be 2·5 to 3 m and 13 to 14 m associated with the R0.5 and R4 unconformities, respectively, and the degree of shoreface erosion during the ensuing marine transgression, estimated to be up to 3 m. This study highlights the complex interplay of mainly physical and chemical processes influencing the formation of subaerial unconformities in carbonate environments during the Devonian, before major evolutionary innovations among vascular land plants led to more intense pedogenesis.     

The evolution of rifting on the volcanic margin of the Pelotas Basin and the contextualization of the Paraná–Etendeka LIP in the separation of Gondwana in the South Atlantic

The Pelotas Basin is the classical example of a volcanic passive margin displaying large wedges of seaward-dipping reflectors (SDR). The SDR fill entirely its rifts throughout the basin, characterizing the abundant syn-rift magmatism (133–113 Ma). The Paraná–Etendeka Large Igneous Province (LIP), adjacent to west, constituted the pre-rift magmatism (134–132 Ma). The interpretation of ultra-deep seismic lines showed a very different geology from the adjacent Santos, Campos and Espírito Santo Basins, which constitute examples of magma-poor passive margins. Besides displaying rifts totally filled by volcanic rocks, diverse continental crustal domains were defined in the Pelotas Basin, such as an outer domain, probably constituted by highly stretched and permeated continental igneous crust, and a highly reflective lower crust probably reflecting underplating.The analysis of rifting in this portion of the South Atlantic is based on seismic interpretation and on the distribution of regional linear magnetic anomalies. The lateral accretion of SDR to the east towards the future site of the breakup and the temporal relationship between their rift and sag geometries allows the reconstitution of the evolution of rifting in the basin. Breakup propagated from south to north in three stages (130–127.5; 127.5–125; 125–113 Ma) physically separated by oceanic fracture zones (FZ). The width of the stretched, thinned and heavily intruded continental crust also showed a three-stage increase in the same direction and at the same FZ. Consequently, the Continental-Oceanic Boundary (COB) shows three marked shifts, from west to east, from south to north, resulting into rift to margin segmentation. Rifting also propagated from west to east, in the direction of the final breakup, in each of the three segments defined. The importance of the Paraná–Etendeka LIP upon the overall history of rupturing and breakup of Western Gondwanaland seems to have been restricted in time and in space only to the Pelotas Basin.     

青海南部杂多地区新建扎青组的地层层序及地质意义

在青藏高原北羌塘盆地青海南部,青海省杂多县扎青乡地区的然者涌一带,发现以基性火山熔岩为主夹有中基性火山碎屑岩,具大陆板内裂谷拉斑玄武岩喷发特点的一套火山地层。该地层底部角度不整合接触覆盖在早中二叠世开心岭群诺日巴尕日保组、九十道班组之上,其上被晚三叠世结扎群甲丕拉组角度不整合覆盖。主要岩性为灰绿—灰紫色橄榄玄武岩、粗面玄武岩、玄武粗安岩及流纹岩、中基性火山角砾岩、角砾凝灰岩夹少量流纹岩和紫红色岩屑砂岩及细砾岩,其特征与峨眉山低钛玄武岩相似,具陆相喷发-沉积特征。区域对比在北羌塘地区具有独特地层特征,可与四川峨眉山玄武岩地层进行对比。而区域上该地区晚二叠世主要为一套海陆交互相含煤碎屑岩建造,未发现陆相火山岩出露,本文建立正式地层单位扎青组,以供参考,其时代暂归晚二叠—早三叠世。     

论全吉运动

全吉运动发生于柴北缘地区的全吉山一带,除角度不整合的自然现象外,接触面上下岩层之岩性载然不同、变质程度迥异,同位素测试值显示,是一次强烈的区域动力变质构造运动。