共查询到20条相似文献，搜索用时 46 毫秒
1.
K. K. Sinha Pradeep Pandey C. L. Bhairam P. S. Parihar 《Journal of the Geological Society of India》2011,77(2):183-189
In the western part of Bundelkhand massif, a caldera with intra-caldera sediments, known as Dhala Formation, occurs as an
outlier in and around Mohar village of Shivpuri district, Madhya Pradesh. For the first time, occurrence of peperite is being
reported from the basal part of the Dhala sediment. Two types of peperites have been recognized: blocky and fluidal or globular
with variable morphology. In peperitic zones, features like soft sediment deformations, presence of sediment into the rhyolite
along cracks, vesiculation of the sediments and other evidences suggestive of sediment fluidization are some definite characteristics
of interaction of hot magma with wet sediments forming peperite. The occurrence of peperites reflects the contemporaniety
of deposition of the Dhala sediments and volcanism, which is well in accordance to the volcanic origin of Dhala structure.
Further, the nature of unconformity between the Dhala and overlying Kaimur which is characterized by merely a few centimeter
thick pebbly/conglomeratic bed does not appear to represent a large hiatus as expected between the Semri and Kaimur of Vindhyan
Supergroup. So, the contemporaniety of the Dhala Formation (at least the lower part) as reflected by occurrence of peperites,
coupled with the available age of the rhyolite and the nature of the unconformity between the Dhala and overlying Kaimur provide
convincing evidence to correlate the Dhala Formation with the Lower part of the Kaimur and unlikely with the Semri Group or
Bijawar as proposed earlier. 相似文献
2.
Gabriella Kiss Ferenc Molnár Ladislav A. Palinka? Sándor Kovács Hazim Horvatovi? 《International Journal of Earth Sciences》2012,101(6):1503-1521
Comparative volcanological, mineralogical, petrological, and geochemical studies of blocks of Triassic submarine basalt occurrences hosted by the Jurassic mélange have been carried out. The studied localities are located in displaced parts of the Dinarides in NE-Hungary (Darnó Unit), in the Dinarides (Kalnik Mts., Croatia and Vare?-Smreka, Bosnia and Herzegovina), and in the Hellenides (Stragopetra, Greece). The common characteristic of the studied occurrences is the well observable result of the lava–water-saturated sediment mingling, i.e., the presence of the so-called carbonate peperitic facies. Mixing of the basaltic lava with pelagic lime mud (representing the unconsolidated stage of the red, micritic limestone), as well as fluid inclusion and chlorite thermometry data support that the carbonate peperite was formed above CCD and at the Bosnian locality, a shallower water, about 1.4?km depth is proven. The igneous rocks show mainly within-plate basalt geochemical characteristics; MORB signatures are not common. Low temperature (<200°C) hydrothermal alteration is characteristic to the pillow basalt blocks with peperitic facies. The similarities in the volcanological, geochemical, and textural characteristics observed at the different localities support a strong genetic connection among them. The results of this study suggest to the advanced rifting stage origin of the Triassic basaltic suits and their distinction from the true oceanic basalt pillow units of the Dinarides can be based on the occurrences of the peperite facies. 相似文献
3.
H. G. Wilshire 《Australian Journal of Earth Sciences》2013,60(1):11-20
Late Permian (early Tatarian, 258 Ma) palaeosols exposed near Kiama and Dapto on the south coast of New South Wales can be recognised from their red colour, clayey and massive texture, and clay‐filled root traces. Harvey pedotype palaeosols are within the upper Jamberoo Sandstone Member of the Broughton Formation. Loveleigh pedotype palaeosols are within the basal Kiama Sandstone overlying columnar jointed flows of the Blow Hole Latite Member of the Broughton Formation. Both kinds of palaeosols are strongly ferruginised with little relict bedding, yet they are little weathered and have surprisingly high amounts of feldspar and pyroxene. Both also show deformation of subsurface layers comparable to the active layer of permafrosted soils. Root traces in these palaeosols are sparse and comparable to those of woody gymnosperms, not chambered like the known roots of Glossopteris. Plausible components of the taiga woodland represented by the palaeosols include Gangamopteris, cordaites, seed ferns, and equisetaleans. Frigid palaeoclimatic indications from the palaeosols are compatible with a palaeomagnetically determined palaeolatitude of 57–85°S, and thus indicate an equator‐pole climatic gradient in the Late Permian generally similar to that of today. 相似文献
4.
D. J. Rawlings 《Australian Journal of Earth Sciences》2013,60(2):109-113
Peperite is a non‐genetic term used to describe volcanic breccia in which a texture of dark blocks in a light matrix resembles a mixture of salt and pepper. In the Gold Creek Volcanics, peperite is a mixture of partly vesiculated basalt clasts in a mudstone‐sandstone matrix. It is formed by the buoyant intrusion of basaltic magma into wet unconsolidated sediment. The intruding bodies deform and quench, giving rise to discordant masses of hyaloclastic breccia, confined largely to the subsurface. These basalt masses may remain hot enough to locally superheat pore water and produce convective systems where the basalt clasts and fluidized sediment become mixed, forming the distinctive peperite. 相似文献
5.
Matthew R. Bennett Richard I. Waller Neil F. Glasser Michael J. Hambrey David Huddart 《第四纪科学杂志》1999,14(2):125-135
The interpretation of glacigenic diamictons is a subjective process, for which quantitative support is frequently sought from parameters such as clast shape and fabric. It has been widely suggested that different glacigenic diamicton facies possess distinct clast‐fabric signatures. This paper examines this concept using a data set of 111 clast fabrics, and a synthesis of published results. Eigenvalues are calculated and compared for a variety sedimentary facies. It is concluded that clast fabric alone is not able to discriminate between different glacigenic facies, and it is argued that clast fabric offers little quantitative support in the interpretation of glacigenic sediments. It is suggested, therefore, that although clast fabric may continue to have a role as an indicator of relative strain at specific sites, its use in the discrimination of glacigenic facies is limited. Consequently, we should be much more selective in undertaking such analyses in the future. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
6.
7.
Shallow marine sediments of the Broughton Formation are dominated by immature volcanic debris of intermediate to basic composition, generated in an adjacent subaerial environment by volcanism responsible for the nine shoshonite units intercalated within sediments of the Kiama region. Sediment was supplied to the offshore environment via periodic storm‐generated, expanded high density turbidity currents. Initial deposition, represented by the Westley Park Sandstone Member, was below storm wave base, during which time the depositional surface was subjected to post‐depositional tractional reworking by northerly directed, tidally influenced bottom currents. The resulting positive‐relief sand bodies on the seafloor contain tractional sedimentary structures (the ‘tractional facies association'). Areas of the substrate between these sand bodies retained their turbidite bedding structure (the ‘rhythmically bedded facies association') but were extensively bioturbated by a diverse deposit‐feeding biomass. Upon emplacement of the lowest of the nine shoshonite units as a tri‐composite, locally intrusive lava flow, the depositional surface was elevated, transgressing storm wave base. The body of the shoshonite flow also shielded the substrate from the northerly directed tractional currents, allowing the development and preservation of the hummocky cross‐stratified sandstone facies in the Kiama Sandstone Member. Following burial of the shoshonite flow by continued deposition, this local shielding effect was overcome and tractional currents again reworked the entire depositional surface. 相似文献
8.
R. J. Dixon 《Geological Journal》1990,25(1):35-46
The Moel-y-Golfa Andesite is a discordant intrusive body of porphyritic pyroxene andesite, 1 km across and at least 200 m thick. Textural variation defines a central facies and a marginal facies, the latter displaying well-formed lobes, tubes, and pillows. The vertically stacked lobes, brecciated tubes, and elongate pillows of andesite intrude and locally enclose enclaves of altered host sediment and are cut by steeply dipping slide scars. The host sediments are locally strongly silicified and cut by numerous, anastomosed vertical and subvertical fissures. Fissures are filled by disrupted host sediment and fragments of brecciated andesite. The formation and filling of each fissure system was probably concomitant with the brecciation of an intrusive magma lobe. The complex relationship of igneous and sedimentary material indicates that the Moel-y-Golfa Andesite was emplaced into the host sediments whilst they were unconsolidated or only partly lithified. 相似文献
9.
10.
J. McPhie 《Australian Journal of Earth Sciences》2013,60(6):545-558
Isolated outcrops of coarse‐ and medium‐grained, quartz‐feldspar porphyry occur for some 60 km from Nobles Nob to near Warrego in the Early Proterozoic Tennant Creek Block of the central Northern Territory. The outcrops appear to be part of an approximately conformable sheet of variable thickness (several tens to a few hundred metres), enclosed by sedimentary rocks of the Warramunga Group. The porphyry is characterized by euhedral, complete, evenly distributed crystals up to 2 cm across, in a microcrystalline groundmass. In some samples the groundmass shows relict perlitic cracks and was formerly coherent glass. In detail, upper and lower contacts of the porphyry sheet are highly irregular: porphyry contains wisps, blocks and large rafts of sandstone, and sandstone encloses single euhedral crystals and blebs, tongues and lobes of porphyry. Clasts of each rock type commonly have fluidal shapes. Sedimentary rocks at both the upper and the lower contacts are indurated and silicified. Close to the contacts, bedding is not easily identified, or else is disturbed. The quartz‐feldspar porphyry is interpreted to have cooled and solidified from phenocryst‐rich magma that intruded approximately parallel to bedding in the enclosing sedimentary sequence. The peperite margins of the sill suggest that the porphyritic magma invaded relatively weak, poorly consolidated, wet sediments rather than solid sedimentary rock. Rapid expansion and movement of heated pore fluid would have temporarily disrupted particle packing in the sediments at the contacts, and allowed intricate penetration of magma accompanied by quenching and fragmentation. In addition to relatively short‐term and local effects on the pore fluid chemical and physical properties, the intrusion was probably responsible for premature and permanent dewatering of the adjacent sediments. The sill together with its bordering zone of peperite and indurated sedimentary rocks may have constituted a significant physical barrier to any subsequent fluid transport in the enclosing sedimentary sequence. 相似文献
11.
M. Carracedo Sánchez F. Sarrionandia T. Juteau J. I. Gil Ibarguchi 《International Journal of Earth Sciences》2012,101(8):2201-2214
Distal pillows occur associated with a sheet flow and megapillows in the me?akoz outcrops of the Basque–Cantabrian Basin (N Spain). Basaltic volcanic rocks are interbedded with Turonian sediments and depict typical features of shallow submarine emissions. An exceptional basaltic flow displays four types of morphology: (1) sheet lava with columnar jointing, (2) welded columnar breccia, (3) megapillows, and (4) pillow lavas with sparse megapillows. The field data from me?akoz combined with experimental and field data from the literature for similar volcanic facies can be integrated into a new propagation model for the transition from sheet flows to pillow lavas in underwater environments. At near vent high emission rates, lava flows develop a thin crust immediately after its emplacement and break at the front under the magma pressure allowing for the massive propagation of lava as a sheet flow. Increased cooling promotes thickening of the lava outer crust far from the vent while continuous supply of fresh magma increases the pressure onto the thick crust until its rupture. The lava emitted in small volumes from the flow front promotes the formation of megapillows and pillow lavas that are later on covered by the advancing sheet flow. The lava flow freezes progressively toward more distal parts, gradually increasing its viscosity until it stops. The crust temporarily holds the residual melt pressure increasing the volume of the flow distal section by inflation. Finally, the internal magma pressure breaks the crust and liberates lava at moderate-to-low flow rates producing pillows, while lava drainage inside the inflated sheet flow produces lava tunnels and gravitational collapse of the roofs by hydrostatic pressure to form breccias nurtured by columnar lava fragments. 相似文献
12.
The base of an upper Palaeozoic graben‐fill in eastern Canada was affected by mafic dyke intrusions shortly after deposition, resulting in the formation of peperite. Complex magma–sediment interactions occurred as the melts mingled with the wet and poorly consolidated clastic material of this sedimentary basin, which is separated from underlying rocks by the Acadian unconformity (Middle Devonian). As a result of these interactions, the mafic rocks are strongly oxidized, albitized and autobrecciated near and above the unconformity, where blocky juvenile clasts of mafic glass and porphyritic basalt have mingled with molten or fluidized sediments of the upper Palaeozoic Saint‐Jules Formation, forming a peperite zone several metres thick. In contrast to most peperite occurrences, the New‐Carlisle peperites are associated with the tip of dykes rather than with the sides of sills or dykes. We argue that more heat can be concentrated above a dyke than above a sill, as the former provides a more efficient and focused pathway for heated waters to invade the poorly consolidated host sediments. Superheated groundwaters that issued from the sides of the dykes appear to have promoted melting of carbonate components in calcareous sedimentary rock clasts of the Saint‐Jules Formation, locally generating carbonate melts that contributed to the mingling of juvenile and sedimentary clasts in the peperite. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
13.
Gabriella Kiss Ferenc Molnár Federica Zaccarini 《Central European Journal of Geosciences》2012,4(2):261-274
The Jurassic pillow basalt blocks in the Szarvask? Unit in the SW-Bükk Mountains are incorporated into an accretionary mélange of Cretaceous age which had been displaced from the Dinarides to NE-Hungary during the Alpine-Carpathian collision. The pillow basalt series is a part of an incomplete remnant of an ophiolite-like sequence from which ultramafic units and sheeted dikes are almost completely absent. At the studied Egerbakta quarry, closely packed pillow, pillow fragmented hyaloclastite breccia and peperitic facies of submarine basaltic volcanism were recognized. Peperitic facies was formed by local admixture of unconsolidated siliciclastic sediment into the basaltic lava. Basaltic pillows contains short and thin prehnite-chlorite-carbonate-quartz veins formed during the interaction of seawater with the cooling lava, as well as cross-cutting datolite-prehnite-quartzchlorite-albite bearing veins. Calcite in the short cooling cracks crystallised from upheated seawater at around 160°C temperature and 0.5?C0.6 kbar pressure (water depth of about 5?C6 km). Datolite precipitations in veins can be classified into at least three different textural-morphological types but all of them contain methane bearing primary fluid inclusion assemblages, with variable methane/water ratios, suggesting an inhomogeneous entrapment from a heterogeneous aqueous-carbonic fluid. End member primary fluid inclusions contain aqueous liquid with methane rich vapour phase and apparently methane only inclusions characterized by liquid phase on room temperature. A combination of results from fluid inclusion microthermometry, Raman spectroscopy (used not only for phase identification but also for determination of salinities) and temperatures calculated from chlorite compositions, show that the precipitation of datolite had taken place from low salinity (0.2?C2 NaCl equiv. mass%) aqueous-methane fluids under increasing temperature and pressure (from 160 to 210°C, and from 0.6 to 1.1 kbar) conditions. The elevated pressures and temperatures in comparison to the submarine hydrothermal processes suggest that the datolite bearing mineral parageneses had been formed during the progression of Alpine very low grade metamorphic processes. 相似文献
14.
The Trooper Creek Formation is a mineralised submarine volcano‐sedimentary sequence in the Cambro‐Ordovician Seventy Mile Range Group, Queensland. Most of the Trooper Creek Formation accumulated in a below‐storm‐wave‐base setting. However, microbialites and fossiliferous quartz‐hematite ± magnetite lenses provide evidence for local shoaling to above fairweather wave‐base (typically 5–15 m). The microbialites comprise biogenic (oncolites, stromatolites) and volcanogenic (pumice, shards, crystal fragments) components. Microstructural elements of the bioherms and biostromes include upwardly branching stromatolites, which suggest that photosynthetic microorganisms were important in constructing the microbialites. Because the microbialites are restricted to a thin stratigraphic interval in the Trooper Creek area, shallow‐water environments are interpreted to have been spatially and temporarily restricted. The circumstances that led to local shoaling are recorded by the enclosing volcanic and sedimentary lithofacies. The microbialites are hosted by felsic syneruptive pumiceous turbidites and water‐settled fall deposits generated by explosive eruptions. The microbialite host rocks overlie a thick association (≤?300 m) of andesitic lithofacies that includes four main facies: coherent andesite and associated autoclastic breccia and peperite; graded andesitic scoria breccia (scoriaceous sediment gravity‐flow deposits); fluidal clast‐rich andesitic breccia (water‐settled fall and sediment gravity‐flow deposits); and cross‐stratified andesitic sandstone and breccia (traction‐current deposits). The latter three facies consist of poorly vesicular blocky fragments, scoriaceous clasts (10–90%), and up to 10% fluidally shaped clasts. The fluidal clasts are interpreted as volcanic bombs. Clast shapes and textures in the andesitic volcaniclastic facies association imply that fragmentation occurred through a combination of fire fountaining and Strombolian activity, and a large proportion of the pyroclasts disintegrated due to quenching and impacts. Rapid syneruptive, near‐vent aggradation of bombs, scoria, and quench‐fragmented clasts probably led to temporary shoaling, so that subsequent felsic volcaniclastic facies and microbialites were deposited in shallow water. When subsidence outpaced aggradation, the depositional setting at Trooper Creek returned to being relatively deep marine. 相似文献
15.
北部湾盆地乌石凹陷东区古近系流沙港组二段构造复杂,沉积差异大,横向变化快,对物源和沉积相的认识存在争议。为了查明研究区沉积相分布与演化规律,文中以岩心、测井、地震和分析化验资料为基础,结合区域构造背景,对研究区流沙港组二段沉积物源、沉积相特征及演化规律展开研究。分析认为,流沙港组二段物源来自于北部高地势地区,发育三角洲前缘—深水湖泊沉积序列,主要发育相对远物源的正常三角洲前缘沉积,砂体单层厚度小、多层交互式分布。井震结合由下到上将流沙港组二段划分为4个四级层序,其中MSC2和MSC3层序为短期快速水退到较长期水进过程,物源供给较为充足,砂体发育程度高,是主力砂体展布层段;流沙港组二段储集层物性主要受埋深及沉积相带约束,B油田物性好于A油田,三角洲前缘近源端发育的水下分流河道、河口坝为有利储集层分布区。 相似文献
16.
北部湾盆地乌石凹陷东区流沙港组三段岩性相对复杂,沉积差异大,横向变化快,连通性差,深入研究流沙港组三段沉积物源和沉积特征对油气勘探开发具有一定的指导意义。在系统的岩心观察与精细描述基础上,结合测井、地震和分析化验资料,针对研究区流沙港组三段沉积物源、沉积相类型及展布特征展开研究。综合分析认为,流沙港组三段物源来自于北部高地势地区,发育相对近物源的水进型扇三角洲沉积,砂体厚度较大,相带窄,相变快,其中三角洲前缘可进一步划分为水下分流河道、河口坝、席状砂、分流间湾等4种沉积微相;在物源分析、井震约束的基础上,依据井震结合含砂率等值线,同时结合测井平面相、地震反射结构、地震构型信息等,综合绘制研究区沉积微相平面展布图,确定了研究区流沙港组三段"大前缘小平原"的沉积特征,并最终建立了该区扇三角洲沉积模式,为乌石凹陷东区流沙港组三段油气勘探开发和储量计算提供了借鉴。 相似文献
17.
Diamictic sediments within high Arctic lake sediment cores: evidence for lake ice rafting along the lateral glacial margin 总被引：2，自引：0，他引：2
I. Rod Smith 《Sedimentology》2000,47(6):1157-1179
Sediment cores from six small lake basins in the Canadian high Arctic reveal a gravel‐rich (≤30% by weight) to gravel‐poor (≥2%) diamict facies underlying massive, post‐glacial, clayey silt. Ten other lakes contain a second diamict facies within what are interpreted to be glaciolacustrine sedimentary assemblages. The sedimentology, clast fabrics and fossil remains (diatoms, ostracodes and chironomid head capsules) within both diamict facies suggest that these deposits are not tills. Clast fabrics yielded low S1 (0·41–0·57) and high S3 (0·09–0·22) eigenvalues, placing them within the range of ice‐rafted diamictons and glacigenic sediment flows. The high percentage of clast dip angles >45° (15–61%), random clast azimuth and lower diamict contacts conformable to underlying current‐bedded sediment favours an origin as a rain‐out or settling deposit. Samples of the matrix and scrapings of clasts from the diamicts revealed a diatom assemblage dominated by littoral and planktonic forms, such as are found in the littoral regions of the lakes today. This contrasts sharply with the assemblages within the overlying clayey silt, in which benthic forms predominate. Clasts are thus interpreted to have been rafted from the littoral areas of the lake. The process proposed to explain this is rafting by the lake ice cover in a glacial‐marginal environment. Early season meltwater, impounded along the lateral margin of retreating cold‐based glaciers, would buoyantly lift the lake ice cover and any adfrozen lake sediment. Higher lake levels and increased areal extent of seasonal freeze‐on between the lake ice cover and the lake bed would allow the redeposition of littoral sediments to the benthic regions through greater lateral shifting of the ice cover as it broke up. Incision by meltwater streams into the lateral glacial margins would later isolate the lake, allowing seasonal warming of lake water, enough to support the growth and maturation of the ostracode and chironomid species found as fossils within the diamicts. 相似文献
18.
熔积岩指的是侵入、混合到未固结或弱固结的湿沉积物中的熔浆分解、原位形成的一类特殊岩石。正确地认识该类岩石,有利于增进人们对岩浆-水(沉积物)相互作用过程的理解,恢复古环境。在青海南部沱沱河地区发现了一套角砾为撕片状、锯齿状及浑圆状的安山岩,胶结物为铁硅质组合的特殊熔积岩。研究表明,该熔积岩的角砾为岩浆遇水后快速淬火、裂解的产物,铁硅质组合为海底喷气沉积形成的含铁建造;且安山岩与含铁建造发生混合时,含铁建造尚未固结。该套熔积岩的发现,改变了长期以来对开心岭铁矿为火山热液交代安山岩而形成的认识,对于在矿区寻找VMS型矿床、区域内寻找海底热水喷流沉积型矿床具有重要的启示意义。 相似文献
19.
Internal architecture of a till sheet,Tiskilwa Formation,north‐central Illinois,USA: Application of architectural element analysis 
下载免费PDF全文
下载免费PDF全文 Jessica M. Slomka Carolyn H. Eyles Riley P. M. Mulligan Edward Donald Mckay III Richard C. Berg 《Sedimentology》2015,62(5):1328-1359
Thick till sheets deposited during the Quaternary form significant aquitards in many areas of North America. However, the detailed sedimentary heterogeneity and architecture and depositional history of till units are not well understood. This study utilizes architectural element analysis to delineate the internal sedimentary architecture of the Tiskilwa Formation exposed at two outcrop sections in north‐central Illinois, USA. Architectural element analysis facilitates systematic delineation of sedimentary architecture based on the nature of facies contacts and change in facies associations, delineation of unit geometries and understanding of depositional processes at different scales of resolution; making architectural element analysis suitable for the sedimentological analysis and palaeoenvironmental reconstruction of subglacial deposits. Eleven facies types are identified in this study, including sand, gravel and diamict facies that record a suite of subglacial depositional processes. Detailed analysis of facies contacts (bounding surface hierarchy) and change in facies associations allows the delineation of five architectural elements, including coarse‐grained lens, coarse‐grained sheet, mixed zone, diamict lens and diamict sheet elements. The spatial arrangement and genetic interpretation of elements, and their spatial relationship with fifth‐order bounding surfaces, allows the delineation of five larger scale architectural units (‘element associations’), which can be mapped in the local study area and record at least three stacked successions of meltwater accumulation and till deposition. The results of this study can be utilized for architectural analysis of till sheets and provide insight to groundwater flow pathways through till in the study area and elsewhere. 相似文献
20.
尚义盆地形成于早侏罗世-早白垩世,盆地内沉积了一套以紫红色、灰绿色陆源碎屑岩为主的地层,仅在晚侏罗世-早白垩世地层局部夹薄层玄武安山质火山岩。通过系统分析尚义盆地的沉积岩、沉积相带展布特征及古水流、砾石成分等,分析了早侏罗世-早白垩世盆地的物源区、汇水中心及古气候的演化,恢复了早侏罗世-早白垩世盆地古地理格局。同时,在前人研究基础上,结合尚义盆地的沉积-充填样式,重点总结和综合分析了盆地内熔积岩、辉绿岩、边界断层等的发育特征,初步推断晚侏罗世-早白垩世尚义盆地为伸展断陷盆地。 相似文献