The Pfitsch-Mörchner Basin,an example of the post-Variscan sedimentary evolution in the Tauern Window (Eastern Alps)

A review of post-Variscan metasedimentary and metavolcanic successions in the western Tauern Window is presented. U/Pb – datations of zircons in metavolcanic rocks reveal ages between 309 and 280 Ma. Deposition of grey conglomerates and black pelites started before 309 Ma in the northernmost basin of the Tauern, the Riffler-Schönach basin. In the more central Pfitsch-Mörchner basin, the onset of conglomerate sedimentation can be dated into the time span between 293 and 280 Ma. The Pfitsch and Windtal Formations are newly defined. The basins were filled with up to 1 km of mainly continental clastics until Early Triassic. Short marine ingressions in Middle- and Late Triassic times flooded only basinal parts of the area where we suppose a more or less continuous sedimentation until the Late Jurassic. Only the Hochstegen Marble documents a nearly complete submergence in the area of the Tauern Window. In spite of the metamorphic overprint, the tentative interpretations of the sedimentary facies give a reasonable picture and allow correlations to nonmetamorphic areas in South Germany or the External Massifs of Eastern Switzerland.     

Deformation and Metamorphism of the Marble Mountain and Pony Camp Areas,Western Triassic and Paleozoic Belt,Central Klamath Mountains,Northwestern California

The Western Triassic and Paleozoic belt (WTrPz) is a regionally extensive, composite terrane correlative with Cache Creek-affinity rocks, a major crust-forming lithotectonic entity of the North American Cordillera. New structural, stratigraphic, and petrologic data suggest that a large tract of greenschist to amphibolite-grade metavolcanic and metasedimentary rock, previously considered to consist of several separate oceanic terranes, is, instead, a single fault-bounded, volcanic island arc, the Sawyers Bar terrane. It represents a mid-Jurassic, relatively intact, recrystallized nappe complex 5 to 10 km thick, extending over 100 km along strike in the central Klamaths. Protoliths of the complex are interpreted to be Lower Triassic (?) to mid-Jurassic supracrustal, volcanic arc-related units deposited, deformed, and metamorphosed within a suprasubduction zone adjacent to the continental margin. Metamorphism increases monotonically with depth in the nappe, ranging from prehnite-pumpellyite to lower greenschist-grade in the Pony Camp area on the south, through greenschist-grade in the medial Sawyers Bar area, to low-pressure amphibolite-grade metamorphism in the Marble Mountains on the north. The Pony Camp area generally lacks penetrative deformation. In the Marble Mountains, peak metamorphism largely postdates intense deformation; nevertheless, folding of fabrics and brittle deformation are common.

The complex is bounded by low-angle, W-vergent, crustal-scale, mid-Jurassic thrusts. The Soap Creek Ridge fault juxtaposes Stuart Fork blueschists over the Sawyers Bar complex. The lower thrust is not definitely established, but must be situated beneath tectonic levels postulated by earlier workers. It may coincide with the previously unrecognized brittle-plastic Isinglass shear zone in the Marble Mountains, and a poorly exposed, unnamed low-angle fault in the Virgin Buttes region west of Pony Camp. In this area, mapping indicates that the Twin Sisters fault is a relatively minor high-angle break within the WTrPz, rather than being a crustal-scale terrane suture. Synmagmatic, brittle extensional faults are common, as are syn and postmetamorphic, regionally extensive, high-angle faults that internally imbricate the WTrPz; the latter are marked by sheared serpentinite. Folds within the Sawyers Bar nappe complex are NE to NW-trending and W-vergent. Structural evidence suggests that W-vergent thrusting, E-W contraction, regional Siskiyou metamorphism, penetrative deformation, and crustal thickening occurred at ～170 to 165 Ma, and preceded voluminous 167 to 162 Ma calc-alkaline plutonism. In the study areas, waning stages of Siskiyou deformation were characterized by thermal relaxation, uplift, extension, crustal thinning, and E-directed tectonic transport. Nevadan age contraction (155 to 150 Ma), prevalent to the west at lower structural levels of the WTrPz, is not recognized in the Sawyers Bar nappe; however, regionally developed open folding of Siskiyou metamorphic fabrics and rare superposed folding and axial-plane cleavage development in the Marble Mountains may reflect a Nevadan event. Brittle deformation that clearly post-dates Siskiyou folding is younger than 150 Ma, but is older than ～130 Ma, the age of the oldest marine strata that overlie the Klamath province regionally. Kinematic evidence from the eastern Marble Mountains suggests sinistral transtension of possibly latest Jurassic-Early Cretaceous age. Late-stage brittle deformation is permissibly Cenozoic; the Sawyers Bar thrust sheet was tilted a maximum of 30° to the south along the flanks of the Condrey Mountain dome during Cenozoic uplift.

The Sawyers Bar nappe complex is similar to other composite terranes in Phanerozoic convergent suture zones throughout the world. Like the Klamath Mountains, these areas also may represent different exposure levels within a single fault-bounded entity rather than an amalgam of disparate terranes.     

A contribution to the geology of the Bahariya Oasis,Western Desert,Egypt

Detailed petrographic investigations of the Upper Cretaceous-Eocene succession exposed at Bahariya Oasis resulted in the recognition of different litho- and biofacies associations, mostly of the carbonate rock type.The litho- and biofacies characters of the Eocene strata reveal comparatively shallow, quiet marine conditions, interrupted by agitated, high energy intervals.During the Maastrichtian age, deeper quiet marine conditions prevailed. The Upper and Lower members of the Campanian strata were deposited under deep quiet marine conditions, relative to shallower agitated conditions that prevailed during the deposition of the middle member.The Lower Cenomanian sediments were deposited under an alternating high and low energy fresh water environment, interrupted with saline (fluviomarine) periods, relative to the comparatively deeper marine conditions that prevailed during the Upper Cenomanian age.The main diagenetic processes recorded are: cementation, aggrading neomorphism, silicification and dolomitization.     

深圳鹏茜大理石矿矿坑突水地质灾害及防治对策

通过对深圳市鹏茜大理石矿的系统水文地质调查，阐明了鹏茜大理石矿的水文地质条件，详细分析了矿坑突水灾害的成因机理及其危害特征，在此基础上，探讨了鹏茜大理石矿矿坑突水地质灾害的防治对策。     

海相、陆相油气及其成因概述

国外油气主要在海相地层中发现,而中国油气主要在陆相地层中找到,根本原因在于地层形成顺序两者相反,前者浅层以海相为主,后者浅层则以陆相为主,大量油气是通过壳深断裂从深部垂直向上运移所形成,储集于浅部的首先被勘探开发。中国海相油气勘探中面临三大问题:(1)海相碳酸盐岩的有机碳含量均很低,难以形成大规模的烃源岩;(2)无法解决碳酸盐岩中的油气运移问题;(3)一些海相地层油气田的油气来源存在争议。共可归纳出三种油气生成模式,即壳源有机质、壳—幔相互作用以及费-托合成。目前人们过于执着于壳源有机质生成,而对费-托合成模式还没有足够认识和重视,这种思维定势阻碍了油气勘探在理论和实践上的进一步发展。大量油气是在地幔深部通过费-托合成或在地壳深部通过壳—幔相互作用形成,并沿深大断裂向上运移,除了浅部有大量聚集,在地壳深部的花岗岩、火山岩、变质岩等基岩中,在我国深部的海相地层和国外深部的陆相地层中同样可以大量聚集。     

Geochemical and SIMS U-Pb rutile and LA–ICP–MS U-Pb zircon geochronological evidence of the tectonic evolution of the Mudanjiang Ocean from amphibolites of the Heilongjiang Complex,NE China

This study presents new secondary-ion mass spectrometry (SIMS) rutile and laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) zircon U-Pb geochronological and whole-rock geochemical data for amphibolites of the Heilongjiang Complex, located within the Yilan area of NE China, to constrain the tectonic evolution of the Mudanjiang Ocean between the Songnen–Zhangguangcai Range and Jiamusi massifs. Magmatic zircon from amphibolites collected from the Yilan Marble Quarry yields a weighted mean ²⁰⁶Pb/²³⁸U age of 274 ± 2 Ma, which is interpreted as the protolithic age. Amphibolites from the Longlangang and Tuanshanzi areas yield rutile U-Pb ages of 177 ± 11 Ma and 172 ± 5 Ma, respectively, which are interpreted to reflect the cooling of these rocks below the closure temperature of Pb diffusion in rutile. Amphibolites from the Yilan Marble Quarry are enriched in light rare earth elements (LREEs) and depleted in high field strength elements (HFSEs; e.g., Nb, Ta and P) relative to large ion lithophile elements (LILEs). Amphibolites from the Longlangang and Tuanshanzi areas have relatively flat chondrite-normalized rare earth element (REE) patterns, and remarkable negative Nb and Ta anomalies. Moreover, all of the amphibolites from the Heilongjiang Complex in the Yilan area have tholeiitic and arc-type geochemical affinities. These amphibolites formed by similar petrogenetic processes, but from distinct mantle sources. The magmas that formed these units were generated by the partial melting of mantle sources metasomatized by subducted slab fluids, and the magma that formed the amphibolites within the Yilan Marble Quarry may have also incorporated sedimentary material. Mantle peridotite from the garnet-spinel transition zone is a possible source for the protolith of amphibolites in the Yilan Marble Quarry, and spinel-peridotites may have been the magma sources for the protoliths of amphibolites in the Longlangang and Tuanshanzi areas. Combining our data for amphibolites from the Heilongjiang Complex in the Yilan area with the results of previous research on Late Paleozoic–Early Mesozoic arc magmatism and metamorphism, we infer that the Late Paleozoic–Early Mesozoic tectonic evolution of the Mudanjiang Ocean was characterized by double-sided subduction. These data indicate that the Mudanjiang Ocean closed during the Jurassic (180–160 Ma).     

The role of tectonism in sequence development and facies distribution of Upper Oligocene cool-water carbonates: Coromandel Peninsula, New Zealand

The Torehina Formation is part of a cool‐water carbonate succession of Oligocene age in New Zealand that crops out on the Coromandel Peninsula, North Island. It contains two major transgressive sequences that record successive onlap of a once emergent landmass. The first sequence records marine flooding of non‐marine to marginal marine fan delta/estuarine facies, followed by deepening upward and formation of a low‐energy, deep (100+ m) muddy carbonate ramp. The capping sequence boundary is characterized by differential uplift and varies considerably in its character over a small (9 km²) area, varying from a burrowed glauconitic firmground to an erosional hardground to an undulatory marine contact to a palaeokarst with < 25 m relief. Sequence 2 sediments, which overlie the palaeokarst with minor (< 10°) angular unconformity, are clayey, marine (offshore) siltstones, whereas open‐marine limestones of equivalent age overlie the other boundary types with no apparent angular discordance. The siliciclastics could either represent lowstand channel deposits or may define interbank deposits contemporary with adjacent carbonates. Palaeogeographic restriction of palaeokarst and sequence 2 siliciclastics identifies a structural corridor oriented strike‐parallel to the adjacent Harauki Graben, which began to develop by this time. Palaeogeographical differences in the character of the basal limestone facies of sequence 2 also occur. These differences identify variation in accommodation during initial stages of deposition imposed by previous differential movement of fault blocks. As a result, relatively warm‐water (20 °C) Amphistegina‐bearing limestones in one area contrast with co‐existing deeper water, silty foraminiferal (benthic > planktic), echinoderm and bivalve limestones in another. This variation disappears upsection, which suggests that initial bathymetric differences were eliminated with renewed rise in sea level, yielding deeper water inner‐shelf sediment facies followed by the accumulation of still deeper, but higher energy, outer‐shelf bivalve and bryozoan facies. The sequence architecture of the Torehina Formation is controlled by tectonism, both long‐term subsidence and short‐term differential uplift. This arose as a result of increasing tectonic activity throughout proto‐New Zealand during the Late Oligocene. In such a system, local and regional variation in tectonism among adjacent basins can impose subtle to marked differences in the timing of sequence boundaries and the character of basin‐fill patterns.     

Metamorphism of an ophiolitic tectonic mélange, northern California Klamath Mountains, USA

ABSTRACT Mineral assemblages in pelitic, mafic, calcareous and ultramafic rocks within a metamorphosed tectonic mélange indicate that the Marble Mountain terrane and adjacent Western Hayfork subterrane (northern California) underwent regional low- to medium-pressure amphibolite facies metamorphism. Metamorphic conditions estimated by comparison of observed assemblages with experimentally-determined reaction boundaries and by geothermometry constrain metamorphic temperatures between about 500° and 570°C. The occurrence of andalusite in regionally metamorphosed pelites indicates pressures below about 370 MPa. Metabasite amphibole compositions also suggest low to intermediate metamorphic pressures. Metaserpentinites containing the upper amphibolite facies assemblage (olivine + enstatite + anthophyllite) are found locally within the study area and have been reported previously by other workers elsewhere in the Marble Mountain terrane. These assemblages may reflect higher temperatures of recrystallization than assemblages in surrounding rocks and may represent vestiges of an earlier high-temperature metamorphic event undergone by the ultramafic rocks prior to incorporation in the mélange. Although the age of the low- to intermediate-pressure metamorphism is poorly constrained, cross-cutting plutons indicate that metamorphism must be older than about 162 Ma. Therefore this regional metamorphic event, which probably marks the accretion of these terranes to the North American continental margin, is older than the currently accepted 151–147 Ma age of the Nevadan event in the Klamath Mountains. The inferred low to intermediate pressures of metamorphism and the lithologies of the protoliths suggest a near-arc tectonic setting and refute a subduction zone model for this event.     

阿尔金山东段恰什坎萨依沟的地层新发现

出露于阿尔金山北坡的这套厚度巨大、基本不变质的海相沉积地层,岩性以火山岩、碎屑岩、碳酸盐岩为主,在恰什坎萨依沟的实测剖面中发现该套地层不整合于一套中深变质的长城系之上,不整合以上的硅质岩中发现放射虫、海绵骨针等化石,放射虫化石经鉴定,年代为奥陶纪中晚期,根据以上新发现对本地区的该套地层进行了重新划分与厘定。     

Laboratory Investigations for the Role of Flushing Media in Diamond Drilling of Marble

Marble is used as a natural stone for decorative purposes from ages. Marble is a crystalline rock, composed predominantly of calcite, dolomite or serpentine. The presence of impurities imparts decorative pattern and colors. The diamond-based operations are extensively used in the mining and processing of marble. Marble is mined out in the form of blocks of cuboids shape and has to undergo extensive processing to make it suitable for the end users. The processing operation includes slabbing, sizing, polishing, etc. Diamond drilling is also commonly used for the exploration of different mineral deposits throughout the world. In this paper an attempt has been made to enhance the performance of diamond drilling on marble rocks by adding polyethylene-oxide (PEO) in the flushing water. The effect of PEO added with the drilling water was studied by varying different machine parameters and flushing media concentration in the laboratory. The responses were rate of penetration and torque at bit-rock interface. Different physico-mechanical properties of marble were also determined. It was found that flushing water added with PEO can substantially enhance the penetration rates and reduce the torque developed at the bit-rock interface as compared to plain flushing water.     

Chadian faunas and flora from dyserth: Depositional environments and palaeogeographic setting of Viséan strata in northeast wales

New floral and faunal data from the oldest Dinantian limestones (Foel Formation) in the Dyserth area, suggest that these sediments are of Chadian age, rather than the Asbian age concluded by earlier workers. The basal late Chadian limestones rest conformably on Dinantian Basement Beds of ?Chadian age or older. The initial inundation of St. George's Land occurred during Chadian times, when shallow-water marine limestones accumulated in the Dyserth area and further to the south, together with terrestrially derived siliciclastics, containing drifted plant fragments. Periodically, a restricted hypersaline lagoonal environment was established but an open marine, neritic environment with abundant stenohaline fauna prevailed in this area. These Chadian sediments accumulated on the proximal part of a carbonate ramp and are presumed to have passed laterally downslope into deeper water basinal facies with Waulsortian buildups of the Irish Sea Basin. In the later Arundian, a carbonate ramp–to–platform transition occurred, with widespread deposition of shallow-water carbonates. In the Asbian this platform developed a rimmed margin, with buildups forming a linear belt between platform and basin. An almost complete Chadian to Brigantian Lower Carboniferous sequence can now be recognized in North Wales. This succession is comparable with the shelf succession in south Cumbria on the northern margin of the Irish Sea Basin.     

四川广元上寺剖面长兴阶放射虫动物群演变及控制因素

对四川广元上寺剖面大隆组的放射虫动物群进行了详细的鉴定和丰度、分异度的统计。发现该放射虫动物群丰度和分异度均较低,以泡沫虫和内射虫为主,含少量十字多囊虫的分子;其丰度和分异度与长兴期海平面变化具有很好的耦合关系:放射虫丰度、分异度较大的层位对应于长兴早期和长兴晚期两次最大海侵事件发生的层位。相对长兴晚期而言,长兴早期放射虫的丰度和分异度较大,这与长兴早期水体相对较深有关。此外,有孔虫与放射虫丰度变化呈现很好的负相关性,这与它们不同的生活习性和水深的变化有关。分析表明:水深的变化是上寺剖面放射虫动物群演变的主要控制因素。     

U–Pb isotopic dating of fluid infiltration and metasomatism during Dalradian regional metamorphism in Connemara, western Ireland

Abstract A metasomatic diopside rock occurs at the top of the dolomitic Connemara Marble Formation of western Ireland and contains titanite and K-feldspar in addition to around 90% diopside ( X _Mg= 0.90–0.97). U–Pb isotopic measurements on this mineral assemblage show that the titanite is both unusually uranium-rich and isotopically concordant, with the result that a precise U–Pb age of 478 ± 2.5 Ma can be determined. The age is identical within error to a less precise Rb–Sr age of diopside–K-feldspar of 483 ± 6 Ma. Petrological evidence indicates that the assemblage crystallized at c . 620° C close to or below the closure temperature of titanite. The age thus provides a precise estimate of the time of metamorphism; this age is 11 ± 3 Ma younger than the 490 Ma age for nearby gabbroic plutons which has previously been used to constrain the peak metamorphic age. This difference accords well with geological evidence that the gabbros were emplaced prior to the metamorphic peak. Analysis of minerals with high closure temperature from assemblages whose crystallization is unambiguously associated with a specific episode of fluid infiltration at the peak of metamorphism provides the basis for a new approach to dating metamorphism. The success of this approach is demonstrated by the results from Connemara.     

贵州长顺代化石炭系中间界线的沉积相研究

在碳酸盐微相的详细研究基础上，贵州长顺代化下、上石炭统剖面由下至上可分出５个主要沉积相：盆地相、开阔海陆架相、下斜坡相、中斜坡相和上斜坡相，下、上石炭统界线处于连续沉积的中斜坡相内。     

滇西耿马四排山地区地质新认识

滇西耿马四排山地区弄巴组（原南皮可组上部）盛产化石抱粉，通过５０多块样品的分析，获得了晚泥盆世末（Ｒｅｔｉｓｐｏｒａｌｅｐｉｄｏｐｈｙｔａ）叶至早石炭世早期（Ｇｒａｎｄｉｓｐｏｒａｓｐｉｃｕｌｉｆｅｒａ）孢粉组合。它们可以与西欧同期孢粉进行对比，并能部分地与澳大利亚同期孢粉对比。因原南皮河组岩性复杂，已经被刘本培等（１９９３）改为南皮河群。本文对原南皮河组上部地层进行了研究并命名为弄巴组，其时代为晚泥盆世末至早石炭世。通过抱粉相分析和野外沉积标志的观察以及对孢粉比较学的研究，从而获得了对该套地层沉积相和植物古地理方面的新认识。     

煤山D剖面的放射虫动物群与海平面变化

煤山D剖面长兴组的放射虫动物群的研究成果很少.对煤山D剖面的放射虫动物群进行了详细的鉴定、个体数量和种的数量的统计.结果表明: 煤山D剖面长兴组的放射虫动物群的相对丰度、简单分异度与长兴期海平面变化具有耦合性: 放射虫丰度、分异度较大的层位基本对应于长兴早期和长兴晚期2次最大海侵事件发生的层位.长兴早期放射虫的丰度和分异度较大(相对长兴晚期而言), 这与长兴早期水体相对较深有关.煤山剖面放射虫动物群与海平面变化之间的这种耦合性为海平面变化的研究提供了依据.      

High-frequency cycles in the upper Aptian carbonates of the Organyà basin,NE spain

High-frequency cycles in Upper Aptian carbonates have been studied on the carbonate ramp of Organyà (southeastern Pyrenees). The depositional area comprises a shallow marine to deeper marine transect. A detailed facies model is developed subdividing the transect into an inner ramp area (above fairweather wave base), a mid-ramp area (between fairweather wave base and storm wave base) and an outer ramp area (below storm wave base). Based on microfacies analysis a cyclostratigraphic and sequence stratigraphic interpretation is established. Variations of the sedimentary patterns within different sections of the homoclinal ramp are due mainly to sea level changes. Sea level changes of third and fourth order are reflected by the shifting of the shallow subtidal facies belts up and down the ramp. The study of fifth-order sea level changes is based on statistical methods (quantitative facies analysis and principal component analysis). The ratio of the fourth- and fifth-order cycles is very similar to the well-known ratio of the eccentricity (100 ka) and the precession (18.6/22.5 ka). The absolute age values derived from the cyclostratigraphy fit into the biostratigraphic framework. Thus, a global eustatic control is assumed to be responsible for the cycles of higher frequency. The lower frequency third-order sequences, however, were considerably influenced by local tectonic processes.     

Le front de la « Zone des marbres » (Pyrénées basco-cantabriques,Espagne), un chevauchement fini-crétacé fossilisé par les brèches marines paléocènes ?

The post-metamorphic breccias which underline the frontal overthrust of the ‘Marble Zone’ (Basque–Cantabrian Pyrenees, Province of Navarre, Spain), interpreted by P. Lamare as ‘mylonites’, correspond to sedimentary breccias of submarine canyon, filling former incised valleys dug within the metamorphic Jurassic/Early Cretaceous carbonates already folded and cleaved (Pyrenean Cretaceous tectorogen). Associated to microrhythmic hemipelagites containing Danian–Selandian planktonic foraminifera from the P1c–P3 interval, these breccias are now assigned to Palaeocene. Stratified and horizontal, they seal Late-Cretaceous structures, of which the overthrusting front of the ‘Marble Zone’ could be the principal regional element.     

An Anvilian (early pleistocene) marine fauna from western Seward Peninsula, Alaska

Cover sediments of the York Terrace exposed near the California River, western Seward Peninsula, Alaska, yield mollusks, ostracodes, and foraminifera that lived during the Anvilian transgression of early Pleistocene age. The fossiliferous sediments lie at the inner edge of the York Terrace, a deformed wave-cut platform that extends eastward from Bering Strait along much of the southern coast of Seward Peninsula. The seaward margin is truncated by the little-deformed Lost River Terrace, carved during the Pelukian (Sangamonian) transgression. The early Pleistocene sediments seem to have been deposited between the first and second of four glaciations for which evidence can be found in the California River area.The California River fauna includes several extinct species and several species now confined to areas as remote as the northwestern Pacific and north Atlantic. The fauna probably lived in water temperatures much like those of the present time but deeper water on the Bering Shelf is suggested.The presence of an early Pleistocene fauna at the inner edge of the York Terrace at California River shows that the terrace was largely carved before and during early Pleistocene time. However, a marine fauna apparently of middle Pleistocene age is found on the York Terrace near Cassiterite Peak, and this seems to indicate that the terrace remained low until middle Pleistocene time. Uplift of the York Terrace probably was accompanied by uplift of Bering Strait. The strait may have been deeper, and there may have been no land bridge between the Seward Peninsula of Alaksa and the Chukotka Peninsula of Siberia during most of early and middle Pleistocene time.     

陕南镇巴筇竹寺期的海绵骨针化石

在陕南镇巴下寒武统西蒿坪段和水井沱组下段的碳酸盐地层中含有大量保存完好、类型多样的海绵骨针化石。基于形态描述法,对海绵骨针化石进行了详细的形态描述及产地与层位判断。结果表明：根据与其共生的小壳化石和三叶虫等生物地层学资料,发现这些海绵骨针化石属于筇竹寺期;该区海绵骨针类型不仅包含有形态规则的二轴四射骨针、三轴六射骨针、三轴五射骨针,而且还有形态不规则的四轴四射骨针、五轴五射骨针、尖头星状骨针、二歧分叉式骨针等;其中的四轴四射骨针、五轴五射骨针、五刺尖头星状骨针、二歧分叉二射式骨针为本次发现的新类型,极大地丰富了海绵骨针的类型。陕南镇巴筇竹寺期海绵骨针化石的数量以及分异度快速增加,充分说明海绵动物在陕南地区寒武纪早期开始大量繁盛并且迅速演化。