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The geomechanical properties of rock masses must be identified to assess their quality and employability; however, the methodologies may differ depending on the lithotype and analytical purposes. The present study aimed to estimate the not-well-known physical-mechanical properties of three types of carbonate rocks (calcarenite, calcilutite, and marble) of Sete Lagoas Formation, which are not recognized in scientific literature, southeast Brazil. These are important rocks from an economic point of view, as they comprise an important input for cement, fertilizers and construction material. Both physical indexes (apparent porosity, apparently dry and saturated specific mass, apparent absorption capacity and wave propagation velocity) and mechanical properties (uniaxial compression, point load and slake durability) were determined. Mechanical tests for these three rock types were correlated to those of other carbonate rocks from other countries, for comparisons. The results showed that the lithotypes under study are peculiar in terms of porosity, wave propagation velocity and strength. Also found were a very high durability and a very good correlation between specific mass and uniaxial compressive strength.

Homogenites are homogeneous and structureless, fine-grained rocks. They have been studied extensively in marine settings and are typically interpreted as being related to catastrophic events such as earthquakes. However, studies on lacustrine homogenite-like rocks are limited. New core data from the Shulu Sag in China reveal that thick massive calcilutites exist in the lower Shahejie 3 Formation, which formed during the middle Eocene rifting stage. Based on petrographic, geochemical, and mineralogical data, these massive calcilutites are interpreted as homogenites and grouped into two types. Type A homogenite is composed of intrabasinal materials characterized by high calcite, total organic carbon (TOC) content, and δ13C value. Type A homogenite has two facies successions, the first of which is characterized by homogeneous appearance capped by an erosional interface and the second is characterized by repeated massive-laminated calcilutite successions. Type B homogenite contains abundant allochthonous materials displaying relatively high dolomite content and low calcite, TOC, and δ13C content. Type B homogenite represents the topmost finer portion of a graded megabed which includes, from base to top, grain supported carbonate conglomerates, slumped deformed portions, and debrites. The whole unit can be considered as a megaturbidite. Earthquakes are the most reasonable triggers of homogenite formation in the Shulu Sag. Type A homogenites are thought to be derived by fluidification, resuspension, and decantation of lacustrine fines due to shock waves generated by an earthquake. Type B homogenites might be deposits of distal turbidity currents and turbid clouds transformed from other gravity flows. The results of this study provide a better understanding of the formation of homogenites caused by earthquakes in a confined lacustrine basin.

The calcareous contourites from the Late Oligocene and Early Miocene in the Petra Tou Romiou type section (southern Cyprus) have been studied in detail, being regarded as outstanding examples of fossil bioclastic contourites and representative of the standard facies model of contourite bigradational sequence. These bigradational sequences of sand-dominated contourites consists of whitish calcarenite beds with wavy layering in the middle portion of the sequence. Gradual alternations of whitish and greenish calcilutites appear above and below these calcarenites. The internal wavy layering is composed by compacted interlayers and non-compacted interstratified layers. In the present study, an in-depth ichnological analysis of the bigradational sequence has been conducted, focusing on ichnological features such as length, shape, diameter, and orientation of individual burrow segments, the configuration of burrow systems, as well as external features, fill material, and finally taphonomy. Trace-fossil assemblages differ, containing Planolites isp., Chondrites isp., and ?Thalassinoides isp. at the compacted interlayers, and non-compacted layers bearing only Planolites structures. The compacted interlayer structures are flattened and elliptical, containing similar fill material as the calcilutite host sediment, though lighter in color. In the non-compacted layers, Planolites are near un-deformed, being cylindrical and tubular, with circular to sub-circular cross-sections. These are located mainly at the base or occupy the entire layer, locally showing longitudinal striae (Planolites reinecki Ksiąziewicz), and filled with calcarenite material. The different trace-fossil assemblages in the compacted layers and non-compacted interlayers, varying in fill material, evidence an original primary differentiation, presumably indicative of fluctuating paleoenvironmental conditions. In consecutive non-compacted layers, the distribution of Planolites is separated by compacted interlayers. This indicates that the middle portion of the contourite type facies, with internal wavy layering, underwent a multiphase deposition. In the non-compacted layers, the almost undeformed Planolites, marked by striae, is consistent with a higher substrate consistency, which is interpreted as being associated with sedimentary condensation or omission, immediately before the next compacted interlayers were deposited. This evidence clearly supports the contention that sedimentary processes governing contourite deposition were intermittent rather than continuous, as traditionally proposed. These findings raise basic questions regarding the bottom current processes, and consequent bedform development in these deep-marine environments.

Tight oil has been discovered in calcilutite and carbonate conglomerate reservoirs in the lower part of the third member of the Eocene Shahejie Formation of the Shulu Sag, Bohai Bay Basin, Northern China. Understanding the nature of lithofacies is essential to evaluating the quality of tight reservoirs. This study analyzed the sedimentary characteristics, geochemistry, and reservoir characteristics of each lithofacies based on thin-section and field-emission-scanning electron microscope observations combined with X-ray diffraction, geochemical parameter, and physical property analysis. Eight lithofacies were identified: (1) varve-like laminated calcilutite, (2) non-regular laminated calcilutite, (3) interlaminated calcisiltite-calcilutite, (4) massive calcilutite, (5) massive calcisiltite-calcarenite, (6) grain-supported carbonate nconglomerate, (7) matrix-supported carbonate conglomerate, and (8) mixed-source carbonate conglomerate. The varve-like laminated calcilutites have intrabasinal organic matter with a low Pr/Ph ratio (0.50–0.63) and high gammacerane/C31 homohopane (0.13–0.29), indicating that they are normal sediments and have good hydrocarbon generation potential. The other lithofacies are event sediments containing a certain amount of terrestrial organic matter. Laminated, organic-rich lithofacies develop organic matter pores and other storage spaces modified by organic acid. Their reservoir quality is better than that of massive or organic matter-lean lithofacies. The conglomerates containing less matrices have better reservoir quality than conglomerates with high matrix contents. The hydrocarbon generation ability and reservoir quality of lithofacies as well as the fracture density are the key factors that control the formation of tight oil reservoirs in the Shulu Sag.

Ichnological analysis of Eocene deep-pelagic whitish chalky calcilutites interstratified with high-energy calcarenite beds in the lower part of the Petra Tou Romiou section (southern Cyprus) was conducted to interpret the development and evolution of the trace maker associations during calcilutite deposition after high-energy episodes. The trace fossil assemblage from the chalky calcilutites consists of Chondrites isp. (Chondrites intricatus and Chondrites targionii), Planolites isp., Taenidium isp., Thalassinoides isp., and Zoophycos isp., typical of the Zoophycos ichnofacies. A composite chalky ichnofabric reveals a multi-tiered association of burrowing animals: the uppermost tier determines a mottled background, the upper tier shows the highest trace fossil abundance and diversity (Planolites, Taenidium and Thalassinoides), the middle tier features Zoophycos and large Chondrites, and the deepest tier consists mainly/exclusively of small Chondrites. This ichnofabric has an autocomposite character, associated with bioturbation by a single ichnocoenosis and gradual upward migration of the tiered macrobenthic community as the pelagic calcilutite sedimentation slowly progresses. There are no changes in the trace fossil assemblage between or within calcilutite intervals, regardless of the associated calcarenite beds. This supports a stable, mature, background calcilutite trace maker association, which recovers shortly after the deposition of high-energy calcarenites. In turn, there would have been a rapid re-establishment of paleoenvironmental conditions during pelagic calcilutite accumulation after episodic deposition of any calcarenitic material.

The study area is part of Gunungsewu Unesco Global Geopark. It is located at Playen District Gunungkidul Regency. Its lithology consists of the intersection of fine-grain carbonate rocks and the marl of the Kepek Formation. Disturbed soils and karst in unique geological conditions control the most building foundations, so those soil improvements to increase the strength of building materials are needed. The method of study was surface geological mapping and collect soil samples. Field mapping recorded 3 types of soils; sandy soils, marly soils, and clayey soils. The soil samples were mixed with 0%, 10%, 15%, 20%, and 25% amounts of calcarenite, calcilutite, and marl to a shape of a beam (for each type of sample soil), then ripened for 0 days, 14 days, 28 days, and 56 days. All beams were tested for liquid limit, plastic limit, specific gravity, bulk density, moisture content, and compressive strength according to laboratory standard operating procedures. Thermal buckling behavior of the composite beam reinforced with the Shape Memory Alloy (SMA) under a non-uniform temperature distribution. The influence of positioning SMA reinforced lamina across the thickness and such parameters as the distribution of temperature, lamination schemes, SMA pre-strains level, and SMA volume fractions on the thermal buckling of laminated beams. The results are the marly soil is the worst soil in quality (highest moisture contents and lowest adhesion). The additions of lime powder (calcarenite and calcilutite) of 25% or 40% into marly soils have reduced the moisture contents and densities of the sample beams, as well as increased adhesion and compressive strength. Those were decreased the specific gravity until ∼1.76gr/cm3, the water content until ∼4.42%, and increased the strength until ∼0.25%.

We used high-resolution 3D seismic data and applied seismic attribute analysis to geometrically interpret and characterize the polygonal fault systems in the Paleocene-Eocene sequence of the Rankin Platform Sub-basin, Northern Carnarvon Basin, Australia. The polygonal faults were identified in a stratigraphic sequence dominated by calcareous clay with minor calcilutite at its lower section that changes to argillaceous calcilutite and calcareous claystone at its upper section. Seismic sections and time slices, through multi-attribute (coherence, energy ratio similarity, and curvature) volumes display a dense distribution of normal faults with polygonal shape and small throws in the plain view. The polygonal fault systems (PFS) exist in two well-defined tiers, which can act as pathways for the fluid flow migration. The first tier coincides with the upper section (Early-Middle Eocene Wilcox Formation) with a few faults and the second one coincides with the lower section of the sequence (Paleocene Lambert and Dockrell formations) with a greater number of faults. Proper understanding and interpretation of the polygonal fault systems as non-tectonic extensional faults are a critical issue in assessing the migration pathway for hydrocarbon (gas) through the Paleocene-Eocene sequence in the Northern Carnarvon Basin, and elsewhere in the world.

Red pelagic sediments are relatively common in the Phanerozoic. They are often interpreted as products of sea-bottom oxidation during greenhouse climate showing a conspicuous alternation with black shales and thus carrying important palaeoceanographic information. The Lower Devonian (Pragian) carbonate strata of the Prague Basin, Czech Republic (Praha Formation) contain a marked band of red pelagic carbonate, up to ~ 15 m thick, which can be correlated for several tens of km. We investigated seven sections (17 to 255 m thick) of the Prague Basin using the methods of facies analysis, outcrop gamma-ray logging, diffuse reflectance spectroscopy, optical microscopy, element geochemistry, magneto-mineralogy and electron microprobe analysis. The aim was to find the mineral carriers of the red colour, investigate the stratigraphic context of the red carbonates and evaluate the local and global prerequisites for their formation. The red pigmentation represents enrichment by hematite with respect to goethite. Approximately 31% of the total reflectance falling in the red colour band represents a threshold for red coloration. The red pigmentation is carried by submicronic hematite dispersed in argillaceous pelagic calcilutite and/or inside skeletal allochems. Gamma-ray log correlation indicates that the red carbonate band developed in stratigraphic levels with low sedimentation rates, typically from 1 to 7.1 mm/kyr, which are comparable to the Mesozoic Rosso Ammonitico facies. The red beds and the whole Praha Formation (Pragian to early Emsian) are characterized by low TOC values (

Fine-grained carbonate rocks, which extensively occur in the Eocene strata in the Shulu sag, Bohai Bay Basin, North China, represent an unconventional, fine-grained carbonate reservoir. However, previous studies have ignored the complexity of the lithofacies components and their formation mechanisms. Fine-grained carbonate rocks are typical reservoirs in which hydrocarbons form and gather. A better understanding of the nature of these rocks is extremely important for evaluating the quality of unconventional, fine-grained carbonate reservoirs. Various lithofacies components were discriminated in this study with a combination of petrographic observations and carbon isotope analyses. These finegrained carbonate rocks comprise terrigenous, biogenic and diagenetic materials. Terrigenous input and biologically induced precipitation are the main sources of the materials in the lake. Five lithofacies were identified based on the observations of sedimentary features (core and thin section) and mineralogical data: (1) varve-like laminated calcilutite, (2) graded laminated calcilutite, (3) interlaminated calcisiltitecalcilutite, (4) massive calcilutite, and (5) massive calcisiltite-calcarenite. Their origins were recorded by various lithofacies components, which are controlled by the interactions of physical, chemical and biological processes. This study indicated that the lithology of the bedrocks was the key factor controlling carbonate accumulation. The tectonics and climate can influence the weathering and types of lithofacies. Primary productivity controlled the precipitation of the endogenic calcite. These factors jointly determined the abundant fine-grained carbonate rocks that have accumulated in the Shulu sag.

We investigated high-resolution stratigraphic distribution of selected major and trace elements and gamma-ray spectra of fourteen Devonian/Carboniferous (D/C) boundary sections of Europe located in the late Palaeozoic Laurussia and Gondwana. The aim was to trace the geochemical signature of a marked forced and normal regressive interval which was associated with rapid progradation of siliciclastics into the marine carbonate systems (Rhenish Massif) and a prominent hiatus in shallow-water ramp settings (Namur–Dinant Basin). This interval represents the late Devonian Hangenberg event (HBE) sensu lato (middle praesulcata conodont zone) as defined by previous authors. This regressive interval (FSST to LST) correlates with thin shale layers (HBE shale) sandwiched between monotonous nodular calcilutite/calcisiltite successions at five pelagic sections of Moravia, Carnic Alps, Montagne Noire, and Pyrenees. In all sections with continuous D/C sedimentation (i.e., except those of the Namur–Dinant Basin), the HBE s.l. interval is accompanied by elevated percentages of detrital proxies (Al, K, Rb, Zr) and changes in their ratios (Zr/Rb, K/Al, Rb/K) which are normally interpreted as indicators of increased siliciclastic input, provenance, and grain size. Zr/Rb and other proxies are traceable even without apparent lithological evidence and can, therefore, facilitate stratigraphic correlation. Paleoredox and productivity proxies (U/Th and Ni/Rb enrichment factors) only rarely show elevated values in the Hangenberg black shale interval, indicating that the associated water dysoxia/anoxia was a local rather than global phenomenon. Global correlations based on the HBE black shales should therefore be dropped in favor of the HBE s.l. interval. Moreover, analysis of sedimentation rates in the upper expansa to kockeli zone interval using the published radiometric ages suggests that the HBE s.l. was a time of significant increase in the rate of siliciclastic supply into the ocean, even in the most distal pelagic sections. Consequently, the previous interpretation of the HBE black shale as a condensed succession deposited during rapid sea-level rise seems unlikely. We interpret the HBE s.l. (i.e., including the HBE black shale) as a marine record of glacioeustatic sea-level drop and increased aeolian transport in connection with late Devonian climatic cooling and glaciation. The set of geochemical markers related to the late Devonian sea-level fluctuation can be used for super-regional to global correlations from platform to basin settings. Moreover, they can facilitate current efforts to determine a new D/C boundary definition.

Infilling of trace fossils can serve as a proxy for sediment otherwise missing from basin deposits. The Petra Tou Romiou section (southern Cyprus) includes calcilutite/calcarenite material that represents deep-marine deposits of Eocene age. Lateral and vertical variation indicates pelagic, gravitational, and bottom-current processes simultaneously influencing sedimentation. Detailed ichnological analysis resolved interactions between these deep-marine sedimentary processes in this distal marine setting. Calcarenite turbiditic beds occur as well-preserved and continuous tabular beds that disappear laterally. In some cases, trace fossils infilled with calcarenitic material are termed tubular turbidites. These structures correspond to actively filled Planolites formed in softground conditions and infilled by calcarenitic sediment interpreted as the record of missing turbiditic deposits when calcarenite turbiditic beds disappeared due to erosion. The variable preservation of calcarenite turbidite beds along with the presences of tubular turbidites indicate rapid erosion following turbidite deposition and post-depositional reworking of turbidites by bottom-currents. A refined interpretation of tubular turbidites can help constrain sedimentary processes that form deep-marine deposits and as such, has considerable paleoceanographic and economic implications.

A railroad crosses the coastal Gascons rockslide, in Quebec, Canada. This study improves the understanding of the rockslide’s failure mechanism and post-failure behaviour responsible for the deformation in the railroad. The slide is an asymmetrical wedge failure of 410,000 m3, in rocks made up of centimetre-scale beds of nodular calcilutite alternating with sandstones and limestone. The post-failure stage of the rockslide is characterised by continuous movement of blocks with speeds ranging from 6 to 110 mm/year. The main water table is just below the sliding surface, but precipitation and snowmelt can raise it above the sliding surface in the upper part of the slide. We propose a model for the rockslide, its failure mechanism, geometry and hydrogeology to provide a baseline for interpreting the near-real-time data collected since 2009.

The Crato Member is one of the most important stratigraphic units of the Araripe Basin due to its fossil content, its context analogous to the Brazilian “Pre-Salt Layers”, and its use as covering stone. Facies and petrographic analyses were combined in our study of a section of the Crato Member in Nova Olinda (State of Ceará, Brazil), aiming to investigate its depositional and diagenetic history. Thus, we analysed the faciology of a continuous columnar section ca. 70 m thick, and collected 13 samples of limestones, sandstones and evaporites. The collected samples were analysed by optical petrography. Five depositional facies were described: massive marly mudstone (Lm), laminated calcilutite (Cl), almost-massive arenite (Am), siltite with climbing ripple lamination (Scc), and columnar evaporite (Ec). The thickest and recurrent facies were interpreted as lacustrine (Lm, Cl), followed by alluvial successions (Am, Scc) interbedded between the lacustrine ones. The succession finishes with faciological evidences for extreme arid conditions (Ec) reached at the end of the interval. The petrography, here focused on rocks of facies Cl, Aqm, and Scc, reinforces the idea of an arid lacustrine system for the local Aptian Stage, and that this system was fed by immature alluvial flows coming from close source areas. Particularly, the very low grade of mechanical compaction and incipient cementation of the terrigenous rocks suggest that the succession as a whole was barely affected by diagenesis after burial that, for this reason, was shallow. The resemblance of the Crato Member terrigenous intervals to the ones of the final of the underlying Barbalha Formation suggests contemporaneity and transitional retrograding passage from one unit to another. Na Bacia do Araripe, o Membro Crato é uma das mais importantes unidades estratigráficas por seu conteúdo fossilífero, seu contexto análogo ao das “Camadas Pré-Sal” e seu aproveitamento econômico como material de revestimento. Neste trabalho, análises de fácies e petrográficas foram combinadas no estudo de uma seção do Membro Crato em Nova Olinda (CE), com o intuito de investigar sua história deposicional e diagenética. Para tanto, a faciologia de uma seção colunar contínua de cerca de 70 m de espessura foi analisada com a coleta de 13 amostras de rochas carbonáticas, siliciclásticas e evaporíticas. As amostras foram analisadas por petrografia ótica. Foram descritas cinco fácies deposicionais: lamito margoso (Lm), calcilutito laminado (Cl), arenito maciço (Am), siltito com laminação cruzada cavalgante (Scc) e evaporito colunar (Ec). As fácies mais espessas e recorrentes foram interpretadas como lacustres (Lm, Cl), seguidas de sucessões aluviais (Am, Scc) em meio aos intervalos lacustres. A sucessão termina com indícios faciológicos de que condições de extrema aridez (Ec) foram atingidas ao final do intervalo descrito. A petrografia, aqui focada em rochas das fácies Cl, Am e Scc, reforça a ideia de que o intervalo do Aptiano local correspondia a um sistema lacustre árido, eventualmente alimentado por fluxos aluviais imaturos a partir de áreas-fontes próximas. Em particular, o baixíssimo grau de compactação mecânica e cimentação incipiente das rochas terrígenas sugere que a sucessão foi pouco afetada por diagênese após seu soterramento, que foi, por essa razão, pouco profundo. A semelhança dos intervalos terrígenos do Membro Crato com aqueles descritos para a porção final da sotoposta Formação Barbalha sugere contemporaneidade com passagem transicional retrogradante entre as duas unidades.

The Shulu Sag is a typical rift valley basin in Eastern China, where the formation mechanism of Cenozoic salt-bearing series has been poorly understood. In this paper, petrologic analysis, X-ray powder Diffraction (XRD) analysis and the analysis of halite ion concentrations of the first member of the Shahejie Formation from two drilling cores were conducted to interpret the formation mechanism of these salt-bearing series in Shulu Sag. The results indicated that the salt-bearing series is mainly composed of calcilutite or mudstone at top and bottom, and anhydrite-bearing halite and thin interbeds of salt-bearing calcilutite and dark grey shale in the middle part. These thin interbeds with porphyritic or petalshaped glauberite crystals or some thinner dark grey shale interbeds separated halites into several members with the average thickness of only 9~12 cm in the two drilling holes. This typical rhythmic pattern due to frequent alternation of concentration was evidenced by the variation of chemical composition and hydrogen isotopes of halite fluid inclusions. The presence of large number of primary fluid inclusions within chevron crystals and vertically oriented bottom-growth crystals showed that the halite were precipitated in shallow water (

Although extensive studies have been conducted on unconventional mudstone (shales) reservoirs in recent years, little work has been performed on unconventional tight organic matter-rich, fine-grained carbonate reservoirs. The Shulu Sag is located in the southwestern corner of the Jizhong Depression in the Bohai Bay Basin and filled with 400–1000 m of Eocene lacustrine organic matter-rich carbonates. The study of the organic matter-rich calcilutite in the Shulu Sag will provide a good opportunity to improve our knowledge of unconventional tight oil in North China. The dominant minerals of calcilutite rocks in the Shulu Sag are carbonates (including calcite and dolomite), with an average of 61.5 wt.%. The carbonate particles are predominantly in the clay to silt size range. Three lithofacies were identified: laminated calcilutite, massive calcilutite, and calcisiltite–calcilutite. The calcilutite rocks (including all the three lithofacies) in the third unit of the Shahejie Formation in the Eocene (Es3) have total organic carbon (TOC) values ranging from 0.12 to 7.97 wt.%, with an average of 1.66 wt.%. Most of the analyzed samples have good, very good or excellent hydrocarbon potential. The organic matter in the Shulu samples is predominantly of Type I to Type II kerogen, with minor amounts of Type III kerogen. The temperature of maximum yield of pyrolysate (Tmax) values range from 424 to 452 °C (with an average of 444 °C) indicating most of samples are thermally mature with respect to oil generation. The calcilutite samples have the free hydrocarbons (S1) values from 0.03 to 2.32 mg HC/g rock, with an average of 0.5 mg HC/g rock, the hydrocarbons cracked from kerogen (S2) yield values in the range of 0.08–57.08 mg HC/g rock, with an average of 9.06 mg HC/g rock, and hydrogen index (HI) values in the range of 55–749 mg HC/g TOC, with an average of 464 mg HC/g TOC. The organic-rich calcilutite of the Shulu Sag has very good source rock generative potential and have obtained thermal maturity levels equivalent to the oil window. The pores in the Shulu calcilutite are of various types and sizes and were divided into three types: (1) pores within organic matter, (2) interparticle pores between detrital or authigenic particles, and (3) intraparticle pores within detrital grains or crystals. Fractures in the Shulu calcilutite are parallel to bedding, high angle, and vertical, having a significant effect on hydrocarbon migration and production. The organic matter and dolomite contents are the main factors that control calcilutite reservoir quality in the Shulu Sag.

Some Internal Units of the western Alpine peri-Mediterranean orogenic system (Betic Cordillera, Calabria-Peloritani Arc) point out to a complex Alpine tectono-metamorphic evolution followed by an exhumation phase. Before the onset of the Alpine compressive tectonics, the rocks of these units belonged to the margins of a microcontinent, the Mesomediterranean Microplate, originated, together with the main plates, following the break-up of Pangaea. To these units, characterized by similar tectono-sedimentary evolution, belongs the Ali-Montagnareale Unit of the Peloritani Mountains (NE Sicily), where the Internal Units of the Sicilian sector of the Maghrebian Chain crop out. The Ali-Montagnareale Unit appears within two small tectonic semi-windows, under the phyllites of the Mandanici-Piraino Unit, and it proves to be formed by three groups of anchimetamorphic formations.The Lower Group is made up of two Upper Permian?-Upper Triassic siliciclastic formations, which grade into each other and which were deposited in alluvial environments. This group is followed by the Intermediate Group, consisting of Middle?-Upper? Triassic formations, indicating deposition in an evaporitic coastal plain evolving to a marine carbonate platform. The Upper Group consists of a Pliensbachian formation, made up of pelagic calcilutites with added carbonate turbiditic beds, followed by a prevailingly marly formation with strata of silicified limestones and episodic calcareous re-sediments. In this latter formation, the finding of Jurassic fossils and Globuligerina oxfordiana, which occurs up to the Valanginian, indicate that the stratigraphic succession spans from the late Early Jurassic to the Late Jurassic and probably reaches the Early Cretaceous.The stratigraphic units are generally separated by tectonic contacts which act as preferential detachment surfaces during compressive and exhumation tectonic phases. The tectonic elision of more or less large intervals of the original stratigraphic succession is diffuse in both tectonic windows.The succession of the Ali-Montagnareale Unit testifies to extensional tectonics, which in Middle-Late Triassic determined the evolution of sedimentation from continental to evaporitic and neritic environments, and, since the Early Jurassic, to calcilutite and marly pelagic sediments with added calcareous re-sediments. This sedimentary evolution records the break-up of Pangaea and the successive opening of oceanic basins. A similar tectono-sedimentary history may be recognized in many other Internal Units of the Alpine peri-Mediterranean Chains.

V kamnolomu Crnotice je bila izkopana s sedimenti in sigo z zapolnjena jama. Analiziran je bil 1,75 m visok del zapolnitve. Profil je sestavljen iz pasovite karbonatne kamnine z interkalacijami rdecih ilovic. Te so se odložile na erozijsko/korozijsko povrsino starejse, že mocno prekristaljene sige. Pasovita in laminirana karbonatna kamnina profila je sestavljena iz prekristaljenega kalcilutita ter je podobna sladkovodnemu apnencu. Znacilna laminiranost nakazuje nastanek iz bogatih organskih filmov. Rdece ilovice sestavljajo kremen, smektit, vermikulit, gibbsit, pM kaolinit, goethit, atanas, rutil, haematit, kalcit, sljude in glinenec. Vsebujejo tudi pelete z vec Mn hidroksioksidov. Rdece ilovice so ostanki preperevanja, odloženi v z vodo zasicenem okolju. Za v profilu vzete vzorce so znacilne srednje do visoke vrednosti Jn kar je posledica velike kolicine železovih mineralov. Srednja paleomagnetna smer je za skupino normalnih paleomagnetnih polaritet enaka D = 10.6°; I = 55.0°, za skupino reverznih polaritet pa D = 173.0°; I = -31.3°. Zgornji del profila kaže reverzno paleomagnetno smer, ki jo prekinjata dve normalni magnetozoni. Sodec po razporeditvi posameznih magnetozon sklepamo, da je vrh najvisje normalno polarizirane cone primerljiv z dogodkom Olduvai (1.76/1.79 Ma) kot najmlajso možnostjo, ostali del profila pa je lahko le starejsi. A fossil cave, filled with cave sediments was open in the Crnotice Quarry. An about 1.75 m high section was analysed. Profile consists of banded carbonate rocks intercalated by red clays which was deposited on corroded/ eroded surface of older speleothems. Banded and laminated carbonate rocks are composed of recrystallized calcilutite resemble freshwater limestones. Characteristics of lamination could indicate its origin from organic-rich films. Red clays are composed of quartz, smectite, vermiculite, gibbsite, pM kaolinite, goethite, anatase, rutile, haematite, calcite, micas and feldspar. They contain pellets with Mn hydroxyoxides. That red clays are weathering products redeposited in water-saturated environment. Samples are characterised by intermediate up to high magnetic values of Jn which is caused by the presence of high amount of Fe-minerals. Mean palaeomagnetic directions are for the group of normal palaeomagnetic polarity equal to D = 10.6°; I = 55.0°, and for the group of reverse polarity than D = 173.0°; I = -31.3°. The top part of the profile shows reverse palaeomagnetic direction interrupted by two normal magnetised zones. According to the arrangement of individual magnetozones we assume, that the top of the highest normal polarised magnetozone could be correlated with the Olduvai event (1.76/1.79 Ma) as the youngest possibility, and therefore the rest of profile must be older.

Microfacies analysis of the Upper Triassic (Norian) "Bača Dolomite": early evolution of the western Slovenian Basin (eastern Southern Alps, western Slovenia)The Slovenian Basin represents a Mesozoic deep-water sedimentary environment, situated on the southern Tethyan passive margin. Little is known about its earliest history, from the initial opening in the Carnian (probably Ladinian) to a marked deepening at the beginning of the Jurassic. The bulk of the sediment deposited during this period is represented by the Norian-Rhaetian "Bača Dolomite", which has, until now, been poorly investigated due to a late-diagenetic dolomitization. The Mount Slatnik section (south-eastern Julian Alps, western Slovenia) is one of a few sections where the dolomitization was incomplete. Detailed analysis of this section allowed us to recognize eight microfacies (MF): MF 1 (calcilutite), MF 2 (pelagic bivalve-radiolarian floatstone/wackestone to rudstone/packstone), MF 3 (dolomitized mudstone) with sub-types MF 3-LamB and MF 3-LamD (laminated mudstone found in a breccia matrix and laminated mudstone found in thin-bedded dolomites, respectively) and MF 3-Mix (mixed mudstone), MF 4 (bioturbated radiolarian-spiculite wackestone), MF 5 (fine peloidal-bioclastic packstone), MF 6 (very fine peloidal packstone), MF 7 (bioclastic wackestone) and MF 8 (crystalline dolomite). The microfacies and facies associations indicate a carbonate slope apron depositional environment with hemipelagic sedimentation punctuated by depositions from turbidites and slumps. In addition to the sedimentary environment, two "retrogradation-progradation" cycles were recognized, each with a shift of the depositional setting from an inner apron to a basin plain environment.

The ∼2720 Ma-old Meentheena Member of the Tumbiana Formation, Fortescue Group, is a 30–50 m-thick succession of alternating siliciclastic and limestone beds that crop out intermittently over a distance of ∼680 km across the Pilbara Craton, Western Australia. Limestones of the member consist of flat-pebble (intraformational) conglomerate, oolite, grainstone, calcisiltite, and calcilutite. Siliciclastics consist of shale, siltstone, and sandstone, and many of these are tuffaceous. Sedimentary structures include abundant symmetrical ripples, ripple cross-stratification, desiccation cracks, teepee structures, and planar to wavy lamination. The member is superficially similar in appearance wherever it crops out; however, the correlation of individual beds and units over distances greater than 15 km is problematic. There are no regional marker beds. Radiometric ages from tuffaceous units young to the west by a few million years. Four lithofacies are defined: (a) flat-pebble conglomerate, (b) ripple cross-laminated oolite/grainstone, (c) planar to wavy-laminated calcilutite/calcisiltite, and (d) shale/siltstone. Stromatolites are found in all three of the limestone facies. Evaporites are rare and include halite pseudomorphs. The four lithofacies are generally found in a vertical succession that characterizes a lithofacies association and reflects a deepening upward succession. Associations may not have all four lithofacies, but do reflect the same deepening upward pattern. The uppermost portions of shale/siltstone facies commonly contain symmetrical ripples and desiccation cracks indicating subaerial exposure. Measured sections contain as many as 25 of these parasequences indicating fluctuating water levels. Limestone lithology and facies commonly change abruptly laterally (at the meter and greater scale) and vertically (centimeter- to meter-scale). The sedimentary structures, differences and abrupt changes in lithofacies patterns, the inability to correlate confidently between regions, and the differences in age from east to west suggest a complex, diachronous, depositional system of fluctuating water levels in separate bodies of water. The limestone is dominated by sedimentary structures indicative of shallow water within wave base; however, it is devoid of evidence of any tidal influence. Possibilities for depositional environments include a tideless sea or a lacustrine system. 87Sr/86Sr values from limestone differ from known Archean marine carbonates. REE patterns are decidedly non-marine as well. A lacustrine system is favored for the Meentheena Member based on sedimentary structures, the abruptness of lithologic and facies changes, the facies association, lateral gradation into fluvial deposits, the inability to correlate many units and beds for more than a few to several kilometers, geochemical data, stromatolites, and comparisons with younger lacustrine basins as well as marine successions. There is no single line of evidence that unequivocally establishes a lacustrine origin; however, multiple lines of evidence are collectively consistent with a lacustrine origin. The Meentheena Member would therefore represent the oldest known carbonate-rich, lacustrine system, which we call the Meentheena lakes system.

The modern Bass Canyon is one of the world's largest submarine canyon systems that is entirely located within a cool-water carbonate environment. Five large shelf-breaching and three slope-confined tributary canyons coalesce on the lower slope and enter the massive deep-water Bass Canyon at 3000 m depth. Normal slope sediments consist predominantly of sandy calcilutite and muddy calcarenite interpreted as mud flow and mud-lubricated sandy debris flow deposits respectively, and hemipelagic foraminiferal calcilutite. Canyon head sediments consist of intraclast-rich calcarenite and calcirudite, probably deposited by mass-wasting events, and fine calcarenite, deposited by cohesionless sandy debris flows. Canyon filling sediments consist of well-sorted fine calcarenite deposited by (long term) semi-continuous cohesionless sandy debris flows, and rarer intraclast-rich mud, interpreted as cohesive sediment gravity flow deposits. Two types of tributary canyons are recognized: V-shaped canyons with steep walls (up to 35°) that are well-defined by backscatter acoustics; and broad U-shaped canyons (walls ≤ 10°) poorly defined by backscatter. It is most likely that tributary canyons developed from down-slope eroding sediment gravity flows triggered at the shelf break, which mature to develop dendritic canyon heads. Dendritic canyon heads entrain coarse-grained shelf sediment, which fuel erosive gravity flows and scour deep V-shaped canyon profiles. Once canyon heads stabilise, shelf-derived erosive sediment flows are reduced and the canyon profile switches from V- to U-shaped. This is aided by continual pelagic sedimentation and sediment gravity flows from the adjacent slope and canyon walls. Mud-free sandy debris flows from the lower slope converge with sandy outflows from tributary canyons and flow down the Bass Canyon floor. Sand cored from the Bass Canyon floor preserves cyclic fluctuations in magnetic susceptibility. High magnetic susceptibility zones are associated with increases in cool-temperature planktonic foraminiferal, and have been tentatively correlated to oxygen isotope stages 6.2–6.8 (135–185 ka) and 8.2–8.4 (245–278 ka). Based on this correlation, sedimentation rates on the slope and within the Bass Canyon were found to be highest during the highstand and regressive systems tracts, and lowest during the lowstand and transgressive systems tracts.

Ancient accretionary wedges have been recognised by the presence of glaucophane schist, radiolarian chert and melange. Recent techniques for the reconstruction of disrupted fragments of such wedges by means of radiolarian biostratigraphy, provide a more comprehensive history of ocean plate subduction and successive accretion of ocean floor materials from the oceanic plate through offscraping and underplating. Reconstructed ocean floor sequences found in ancient accretionary complexes in Japan comprise, from oldest to youngest, pillow basalt, limestone, radiolarian chert, siliceous shale, and shale and sandstone. Similar lithologies also occur in the melange complexes of the Philippines, Indonesia, Thailand and other regions. This succession is called ‘Ocean Plate Stratigraphy’ (OPS), and it represents the following sequence of processes: birth of the oceanic plate at the oceanic ridge; formation of volcanic islands near the ridge, covered by calcareous reefs; sedimentation of calcilutite on the flanks of the volcanic islands where radiolarian chert is also deposited; deposition of radiolarian skeletons on the oceanic plate in a pelagic setting, and sedimentary mixing of radiolarian remains and detrital grains to form siliceous shale in a hemipelagic setting; and sedimentation of coarse-grained sandstone and shale at or near the trench of the convergent margin. Radiolarian biostratigraphy of detrital sedimentary rocks provides information on the time and duration of ocean plate subduction. The ages of detrital sediments becomes younger oceanward as younger packages of OPS are scraped off the downgoing plate. OPS reconstructed from ancient accretionary complexes give us the age of subduction and accretion, direction of subduction, and ancient tectonic environments and is an important key to understanding the paleoenvironment and history of the paleo-oceans now represented only in suture zones and orogenic belts.

The trace fossil Zoophycos has been described from the Middle Triassic carbonates of the German Basin for the first time. It occurs in a calcilutite bed at the top of a shallowing-upward cycle (parasequence) in the transgressive systems tract of the Middle to Upper Muschelkalk sequence of Thuringia (Germany). Based on sedimentological and palaeontological features, the studied interval is interpreted as deposited in a marine nearshore environment with proximal storm deposits (tempestites). Zoophycos occurs in a very simple planar form with lobate spreiten, which were most likely produced by a worm-like animal by strip mining. The upper tier of the ichnofabric consists of Zoophycos, whereas the lower tier is occupied by cylindrical trace fossils of unknown taxonomic affiliation and with decreasing size towards the bottom. Associated trace fossils such as Rhizocorallium, Balanoglossites and Trypanites indicate a partly firm to hard substrate. No mixed layer is developed at the top of the trace fossil bearing succession. The ichnofabric together with the sedimentological features (disseminated pyrite, blue-grey colour) and palaeontological circumstances (poor benthic fauna, meiofauna with a small body size) support an interpretation of a dysaerobic environment. In the view of evolutionary change, Palaeozoic Zoophycos occurs in both deep and shallow marine deposits, whereas Mesozoic and Cenozoic Zoophycos is only common in shelfal and deeper-marine deposits. The new finding from the shallow-marine Middle Triassic represents the first reliable occurrence of Zoophycos after the end-Permian mass extinction and shows close similarities to its Palaeozoic precursors. It demonstrates that the producer survived the end-Permian mass extinction, became re-established in the nearshore realm and progressively colonized deeper-marine environments during the Mesozoic and Cenozoic.

New biostratigraphic data and revised lithostratigraphic correlations reveal that the current stratigraphic nomenclature for the Lower Jurassic portions of the Fernie Formation in the subsurface of west-central Alberta is inadequate. This paper introduces a new member, the Gordondale Member, for highly radioactive, fine-grained strata previously referred to as either the lower Fernie Formation, the Lower Fernie shelf limestone and clastics, the Nordegg Member, or the “Nordegg Member”. A new occurrence of a late Toarcian ammonite, which constrains the age of the top of the Gordondale Member, is also reported. The Hettangian to upper Toarcian Gordondale Member is an important hydrocarbon source rock and consists of dark brown, finely laminated, organic-rich, phosphatic and highly radioactive calcitic mudstones, calcilutites and fine-grained calcarenites. Fish fragments, pectinoid bivalves, Ostrea, belemnoids, ammonites, coccoliths and radiolarians are abundant. The Gordondale Member is laterally extensive and thins westward from a maximum thickness of approximately 50 m in the subsurface of west-central Alberta to 19 m at Pink Mountain in northeastern British Columbia.

This paper presents the experimental characterisation of hydraulic and mechanical properties of two fine-grained materials from the Aigion Fault Zone, on the southern shore of the Gulf of Corinth, Greece. One is a calcilutite, which commonly caps the basal limestone units, and the other is siliceous active fault gouge from 760 m depth in the borehole. Oedometric compaction/consolidation tests of unconsolidated cylindrical samples at variable stresses were conducted under drained conditions, and then permeability measured by a constant flow technique. The axial strain measurements show consolidation curves with a decelerating strain rate that can be approximated by a power-law function. The permeability is negatively and linearly correlated to the stress, and ranges from 9 to 15×10−18 m2 for the calcilutite and 0.9 to 2×10−18 m2 for the fault gouge with varied vertical stresses. To cite this article: I. Song et al., C. R. Geoscience 336 (2004).

During detailed interpretation of seismic survey JNOC88 and some AGSO lines in the northeastern part of the Offshore Canning Basin (Offshore Fitzroy graben and part of the Rowley sub-basin), different scales of valleys and channels in the Albian to Palaeocene succession were noted. The sediments in the area of valley/channel development are dominantly calcilutite, marl, clay, silt, and fine sand deposited in shelf-to-slope water depths. The most evident valleys are associated with the Upper Cretaceous seismic event C6-2 and the Base Tertiary seismic event C13-1, with dominant north-south and northeast trends that are different from the northwest dip of the paleo-slope and -shelf. Small channels developed between C6-2 and C13-1 with an estimated northwest trend. We classify these channels and valleys into four categories: Type 1 to 3 valleys and Type 1 channels according to their scale, morphology, and related geological processes. Among them, Type 1 and Type 2 valleys are associated with the low point of ...

We present a finite-element study of stress perturbation in evolving compressive and extensional strike-slip fault bridges. The results are compared with a fracture study of a compressive bridge at St Donats, UK. Horizontally interbedded calcareous mudstone and bioclastic calcilutite at St Donats have a distinct vertical permeability anisotropy. This sedimentary sequence behaves as a set of horizontal aquifers. The fluid flow in these aquifers is sensitive to mean stress gradients. Paleostress analysis of field fracture data, verified by finite-element modelling, indicates a rotation of σ 1 towards parallelism with boundary faults inside the growing compressive bridge. Boundary faults and bridge faults recorded numerous fluid flow events. The modelled mean stress pattern shows a regional maximum within the bridge and local maxima/minima pairs at boundary fault tips. Finite-element modelling of an extensional bridge indicates that σ 3 rotates towards parallelism with boundary faults. The mean stress pattern is similar to the pattern in compressive bridge but with maxima and minima locations interchanged. The stress patterns are reestablished by each stress build-up preceding the rupturation of the boundary faults throughout the development stages of strike-slip fault bridges. Mean stress gradients developed pre-failure control the fluid flow in fractures of the strike-slip fault system at and after the end of each stress build-up and the fluid flow in boundary faults post-failure. Fracture reactivation and new fracture generation within an evolving bridge is a process consisting of multiple successive events that retain the storage capacity of the bridge. Rupture and sealing of the main bounding-faults is a step-wise process that opens and closes fluid conduits between areas with different pressures.

As part of a study to investigate relative sea level history from the Tertiary North West Shelf of Australia, we describe a seismically imaged, stratigraphic architectural element not previously associated with prograding carbonate clinoforms, a strike-oriented trough on an early mid-Miocene sequence boundary. This trough, located on a shallowly dipping carbonate ramp, is recognized on both 2-D and 3-D seismic data by truncation, reflector interruption and amplitude variations. It is composed of three individual segments, each up to 500 m wide and 60 m deep, with variable cross-sections. Their combined length, orthogonal to the progradation direction, is ∼8 km. The trough occurs where there is a slight basinward increase in dip, and a facies change on the ramp from sand-sized calcarenite to clay-sized calcilutite. It has both a cross-cutting and sub-parallel relationship with underlying Paleogene faults reactivated within a Mesozoic basin-forming trend. The trough, does not conform to known drainage patterns, or contour current incisions mapped in similar environments elsewhere. We propose that this seismically mapped trough is karst topography that developed as a result of preferential dissolution focused by heterogeneities within the exposed carbonate ramp. Stable isotope analyses conducted on bulk carbonate samples ∼2 km updip, suggest a mixed, marine to slightly meteoric origin for associated porewaters. Furthermore, the sequence boundary on which the trough is developed is contemporaneous with recognized subaerial exposure surfaces to the northeast and southwest. The presence of such a karst feature indicates a minimum fall in relative sea level at this location of 80–160 m during the early mid-Miocene.

The uppermost Maastrichtian Penalver Formation and its equivalents in northwestern Cuba are characterized by thick, normal-graded calcarenite with distinct basal conglomerate, and have been suspected as deposits related to the Cretaceous–Tertiary boundary (K/T) impact. However, its depositional mechanism is not well understood and clear evidence for its association with the impact has never been presented. In this study, detailed field survey and petrographic observations were carried out on the Penalver Formation in order to clarify its sedimentary processes and to test its relation to the K/T impact. The Penalver Formation at the type locality near Havana is approximately 180 m thick and is subdivided into the Basal, Lower, Middle, Upper and Uppermost Members based on its lithology. The Basal Member consists of massive, poorly sorted, calcirudite with grain-supported fabric, which contains abundant macrofossils of shallow-marine origin and occasional large intraclasts of the underlying strata, suggesting that it was formed by a grain flow from a carbonate platform on the Cretaceous Cuban Arc. The Lower to Uppermost Members consist of massive calcarenite and calcilutite that show upward fining. Composition of the calcarenite is distinctly different from that of the Basal Member. The homogeneous appearance, coarse-tail normal grading, abundant water escape structures, and abundant reworked fossils in these members are consistent with those of the Mediterranean “homogenite”, a deep sea tsunami-induced deposit that was formed by settling from a high density suspension. Repetition of thin conglomerate beds in the Lower Member that contain well-sorted, well-rounded mud clasts and shallow marine fossils is considered to reflect intermittent lateral flow possibly induced by a series of tsunami waves during an early stage of settling of grains from a high density suspension. Altered vesicular glass of probable impact origin and shocked quartz are discovered in the Basal and the Lower to Upper Members, respectively. Together with the biostratigraphically constrained age of the Penalver Formation, this evidence suggests that the Penalver Formation has a genetic relation to the K/T impact. Distribution of altered vesicular glass and shocked quartz grains can explain the sequence of the initial grain flow and the following tsunami waves.

Three formations exposed in the Giralia Anticline record the transition from siliciclastic to carbonate-dominated sedimentation on the Southern Carnarvon Platform, a stable shelf on the passive western Australian continental margin. The succession consists of condensed and partly eroded sequences that record maximum marine flooding events and the unconformities between them. The stratigraphic record of the depositional change is evident in four

Sediments of the Upper Carboniferous to Lower Jurassic Karoo Supergroup (∼ 4.5 km thick) were deposited in the mid-Zambezi Valley Basin, southern Zambia. The Upper Palaeozoic Lower Karoo Group in this area ends with a Late Permian sedimentary unit called the Madumabisa Mudstone Formation. The formation is 700 m thick and comprises four lithofacies grouped into two facies assemblages, collectively interpreted as lacustrine deposits. Sediments of a massive mudrock facies assemblage were deposited from suspension, probably from sediment-laden rivers entering a lake. Concretionary calcilutite beds probably mark the positions of palaeosediment-water interfaces where calcite was precipitated. A laminated mudrock facies assemblage is attributed to lacustrine deposition from inflowing rivers at the lake margins and shallow parts of the lake. Repeated thickening-upward cycles are evidence of upward shallowing, interrupted by events of more abrupt deepening. Sandstone interbeds are interpreted as fluvial deposits laid down during low lake stands, with cross-lamination and asymmetrical ripples indicating current rather than wave deposition. A fossil assemblage of ostracods, bivalves, gastropods, fish scales, the alga Botryococcus sp. and fossil burrows is consistent with a lacustrine origin for the formation.

Sonic velocities in the Toolonga Calcilutite (Upper Cretaceous), the Gearle Siltstone and Haycock Marl (mid-Cretaceous), and the Muderong Shale (Lower Cretaceous) were each used to independently quantify apparent uplift (height above maximum burial depth) in the Carnarvon Basin. Apparent uplift is given by the difference in depth between the present-day velocity–depth trend for a unit in a particular well and the reference trend (unaffected by uplift) of the unit. Apparent uplift results derived from the Toolonga Calcilutite, Gearle Siltstone and Muderong Shale are statistically similar. The consistency of results from carbonate and clastic units suggests that, at the formation and regional scale, overcompaction (i.e. anomalously high interval velocity) in these three units reflects previously greater burial depth, rather than sedimentological and/or diagenetic processes, and validates the use of lithologies other than shale in maximum burial-depth studies. The proposed magnitudes of apparent uplift are greatest along some of the main structural highs of the Carnarvon Basin. Apparent uplift of approximately 800 m was determined along the Legendre Trend, and along the Barrow Arch. In excess of 900 m of apparent uplift was determined on the Bambra Anticline. The consistency of results from units of Early to Late Cretaceous age suggests that uplift must have post-dated the youngest (Late Cretaceous) unit analysed.

The Karoo Supergroup outcropst in the mid-Zambezi Valley, southern Zambia. It is underlain by the Sinakumbe Group of Ordovician to Devonian age. The Lower Karoo Group (Late Carboniferous to Permian age) consists of the basal Siankondobo Sandstone Formation, which comprises three facies, overlain by the Gwembe Coal Formation with its economically important coal deposits, in turn overlain by the Madumabisa Mudstone Formation which consists of lacustrine mudstone, calcilutite, sandstone, and concretionary calcareous beds. The Upper Karoo Group (Triassic to Early Jurassic) is sub-divided into the coarsely arenaceous Escarpment Grit, overlain by the fining upwards Interbedded Sandstone and Mudstone, Red Sandstone; and Batoka Basalt Formations. Palynomorph assemblages suggest that the Siankondobo Sandstone Formation is Late Carboniferous (Gzhelian) to Early Permian (Asselian to Early Sakmarian) in age, the Gwembe Coal Formation Early Permian (Artinskian to Kungurian), the Madumabisa Mudstone Late Permian (Tatarian), and the Interbedded Sandstone and Mudstone Early or Middle Triassic (Late Scythian or Anisian). The marked quantitative variations in the assemblages are due partly to age differences, but they also reflect vegetational differences resulting from different paleoclimates and different facies. The low thermal maturity of the formations (Thermal Alteration Index 2) suggests that the rocks are oil prone. However, the general scarcity of amorphous kerogen, such as the alga Botryococcus sp., and the low proportion of exinous material, indicates a low potential for liquid hydrocarbons. Gas may have been generated, particularly in the coal seams of the Gwembe Coal Formation, that are more deeply buried.

The Dorud Formation (Lower Permian) in the Alborz Mountains, Iran, was sampled on the basis of changes in lithology and 185 vertically oriented thin sections and acetate peels were prepared and subjected to detailed petrographic study. Statistical sequence analysis using embedded Markov chains, combined with microfacies techniques, led to recognition of an ideal shallowing-upward sequence, which, in turn, was converted into a horizontal depositional model. This new combined approach revealed that the Dorud Formation consists of two distinct, but related, groups of microfacies; designated as carbonates and siliciclastics. The first group represents marine, subtidal to intertidal environments and includes the following microfacies: (1) a mud-supported calcarenite with calcilutite matrix; (2) a grain-supported biocalcarenite with calcilutite matrix containing Pseudoschwagerina sp.; (3) a grain-supported biocalcarenite with sparite cement; (4) a grain-supported oncolitic calcirudite with sparite cement; (5) a dolomitized arenaceous calcarenite with sparite and dolosparite cements; and (6) a grain-supported pelletoidal calcarenite with sparite cement. The second group represents a marine to fluviodeltaic environment and consists mainly of sandstone (ranging from quartz-arenite to chert-arenite) and siltstone. The following diagenetic events occurred in the carbonate microfacies: dissolution of high-Mg calcite and aragonitic shells; precipitation of syntaxial and bladed calcite cement; compaction; precipitation of blocky sparite cement; fracturing; dolomitization; a second phase of bladed calcite cementation; a second phase of blocky calcite cementation; and stylolitization. The diagenetic features observed petrographically in the siliciclastic microfacies represent changes which took place under shallow to deep burial conditions.

Apresenta-se o resultado da investigação de dois furos de sondagem realizados em uma mina na região de Arcos (MG). Foram realizados estudos de petrografia macroscópica e microscópica, que permitiram o detalhamento de uma seção de aproximadamente 175 m, a qual contempla o embasamento cristalino e 10 unidades sedimentares. O embasamento é representado por granodiorito verde-escuro a cinza, de granulação fina a média, inequigranular. Na base da coluna sedimentar, a Unidade 1 representa uma camada decimétrica de diamictito polimítico, sobre o qual se assentam os calcários impuros da Unidade 2. A Unidade 3 é composta por calcilutito e eventuais camadas de folhelho carbonoso, apresentando gradação para a Unidade 4, composta por marga e argilito. A Unidade 5 corresponde a uma espessa sequência de calcarenito claro, maciço e estilolítico, que passa a apresentar estratos lamelares e estruturas microbianas na Unidade 6. A Unidade 7 é semelhante à anterior, porém com diversas camadas intraclásticos. A Unidade 8 representa um espesso intervalo com frequentes variações granulométricas que gradam para o calcarenito oolítico da Unidade 9. Capeando a sequência, a Unidade 10 é um espesso pacote de dolarenito estromatolítico. O arranjo estratigráfico observado permite a identificação de tendências progradacionais/retrogradacionais coerentes com o contexto regional da bacia. As características sedimentológicas presentes, principalmente na porção basal, sugerem que pelo menos parte do pacote carbonático possa representar um cap carbonate, apontando no sentido de uma origem glacial para o diamictito. Ainda nas unidades inferiores, os dados sugerem modificações na área fonte no início do preenchimento da bacia.

The Cow Head Group is an Early Palaeozoic base-of-slope sediment apron composed of carbonate and shale. Whereas coarse-grained conglomerate and calcarenite are readily interpreted as debris-flow and turbidite deposits, calcilutite (lime mudstone), calcisiltite, and shale combine to form three distinct lithofacies whose present attributes are a function of both sedimentation and early diagenesis. Shale is the most common lithology. Black, green, and red shale colour variations reflect the abundance of organic matter in the source area and oxygenation conditions of the sea bottom. In black and green shale, millimetre- to centimetre-thick, alternating dark and light laminations represent terrigenous mud turbidites and hemipelagites, respectively. The calcisiltite/shale facies is uncommon and is composed of numerous graded carbonate-shale sequences (GCSS) deposited from waning carbonate turbidites and fall-out of terrigenous muds. Some of the characteristics of ribbon and parted lime mudstones in the calcilutite/shale facies can be explained by deposition of carbonate mud from dilute turbidity currents or hemipelagic settling. Other features are diagenetic in origin. The lack of micrite in GCSS and in the interbedded shales of the calcilutite/shale facies is interpreted to reflect early dissolution of the finer carbonate from these sediments. This remobilized carbonate was precipitated locally to: lithify lime mudstone turbidites or hemipelagites; form diagenetic lime mudstone beds and nodules; cement calcisiltites; and form dolomite. Many of the calcisiltites and calcilutites were, therefore, carbonate enriched at the expense of adjacent argillaceous sediments. These attributes characterize not only fine-grained sediments of the Cow Head Group but many other Early Palaeozoic slope carbonates as well, suggesting that the model proposed here for depositionl diagenesis has wider application.

Limestone localities are more studied because of their palaeontological yield. In the absence of an appropriate name, the Rajang Group, which occurs in Sarawak and western-central Sabah are chronologically equivalent. This chapter discusses the eastern Rajang Group. The marine strata that overlie the Lower Cretaceous chert consist of sandstone-shale turbidite and calcareous rocks. They represent an infilling phase of the marine basin by terrestrially derived turbidites and localized carbonates as the water shallowed above the carbonate compensation depth. The limestones with their age discussed in the chapter are Agob-Dabalan area, Madai, Batu Baturong, Lower Tingkayu River, and other limesztone localities in the segama area. Thin beds of tuffaceous limestone and calcilutite occur in the Agob-Dabalan area of the Segama River of Lahad Datu. The main part of the Madai Limestone is detrital and all fossils broken and abraded. Both the Madai and the Baturong limestones are deposited on seamounts occurring within the Chert-Spilite Formation deep sea. Thin lenses of Foraminiferal limestone and marl occur in the Lower Tingkayu River NE of Gunung Madai.

A thick, calcareous, clastic megabed of late Maastrichtian age has been known for sometime in western and central Cuba. This megabed was formed in association with the bolide impact at Chicxulub, Yucatn, at the K/T boundary, and is composed of a lower gravity-flow unit and an upper homogenite unit. The lower gravity-flow unit is dominantly composed of calcirudite that was formed because of collapses of the Yucatn, Cuban, and Bahamian platform margins and subsequent accumulation in the lower slope to basin margin environment. The gravity flow probably was triggered by a seismic wave induced by the impact, although a ballistic flow may have triggered collapse in the case of proximal sites (Yucatn margin). The upper homogenite unit is composed of massive and normally graded calcarenite to calcilutite that was formed as a result of large tsunamis associated with the impact and deposited in wider areas in the deeper part of Paleo-western Caribbean basin. Slight grain-size oscillations in this unit probably reflect the influence of repeated tsunamis. The large tsunamis were generated either by the movement of water into and out of the crater cavity or by the large-scale slope failure on the eastern margin of the Yucatn platform. In upper slope to shelf environments, gravity-flow deposits and homogenite are absent, and a thin sandstone complex influenced by repeating tsunami waves was deposited.

Cyclicities observed in a (hemi-)pelagic rhythmic calcilutite-marl succession of late Berriasian age near Caravaca, southeast Spain, match well with the quasi-periodicities of the Milankovitch model. The shortening of the precession and obliquity in pre-Quaternary times is taken into account. The interval of the Miravetes formation studied has a thickness of 77.5 m, extends from the base of the Calpionellopsis simplex subzone (D1) to the top of the Calpionellopsis oblonga subzone (D2), and has an estimated duration between 1.1 and 2.9 Ma. The evolution of the cyclicities in this succession was analyzed by comparing the spectra of ten successive overlapping segments. From this comparison we conclude that ∼11 m at the top and base of the succession show variations in accumulation rate. Disregarding these parts, the spectrum of the remaining interval (56 m) reveals well-defined spectral peaks. The cyclicity is ascribed to orbital forcing, because all cycles longer than the bedding cyclicity can be matched with the known orbital quasi-periodicities reported in Berger and others (1989a, 1989b). This match with Milankovitch cyclicities produces a considerably more precise estimate for Berriasian zone durations. The range of the duration of the combined calpionellid subzones D1 and D2 reduces to an interval between 1.1 and 1.2 Ma, and the length of the entire Berriasian stage is estimated to fall between 2.9 and 3.1 Ma.

The Teurian (Paleocene) sequence at Te Kaukau Point, southeast Wairarapa, includes light green-grey, indurated, burrowed, slightly sandy calcilutite. These rocks are interbedded with laminated sandstone, mudstone, and siliceous limestone lithotypes, all of which are cut by intrusive sandstone. A variety of sedimentary structures, including burrows, indicate that the laminated sandstone was deposited conformably within the limestone sequence and is regarded as a turbidity current deposit, which later became overpressured to produce the intrusive sandstone. In terms of age, lithology, and stratigraphic position, the calcilutite at Te Kaukau is equivalent to the Amuri Limestone of the northeastern South Island.

The epifaunal, rudist-like bivalve Lithiotis formed extensive bioherms during the Pliensbachian and Toarcian ages of the Early Jurassic. The best developed bioherms in North America occur in the Pliensbachian Robertson Formation of east-central Oregon, a unit deposited in a shallow sea transgressing across the Suplee shelf. A typical bioherm consists of three biofacies that coexisted laterally and replaced each other vertically. The reef flank assemblage is the most diverse consisting of Nerinea gastropods, terebratulid brachiopods and Lithiotis debris in a calcarenite or calcilutite matrix. The death assemblage consists of tightly packed, current-aligned Lithiotis valves with gastropods and brachiopods much reduced in numbers. The core of the reef is built almost exclusively of in situ Lithiotis forming a bafflestone with a calcilutite matrix. Lithiotis inhabited a stressful environment inimical to most invertebrates since diversity is very low and there is no evidence of bioerosion. During the Pliensbachian, Lithiotis formed an endemic centre encompassing western North America and the Tethyan Ocean, linked through central America and the central Atlantic by the Hispanic Corridor. By the close of the Pliensbachian it had disappeared from North America but in the Toarcian made its first appearance in South America. By the end of the Toarcian, Lithiotis was extinct.

A number of facies can be recognised within the Waulsortian Limestone Formation of the Dungarvan Syncline. Bryozoan ‘reefs’ are common, but mottled, shale-wisped and homogeneous calcilutites comprise the bulk of the formation. Crinoidal limestones, banded and cherty calcilutites are minor components. The bryozoan ‘reefs’ developed in deep water, but with decreasing water depth the production and sedimentation of micrite increased, eventually smothering the bryozoans, resulting in mottled and homogeneous calcilutites. The presence of bryozoan ‘reefs’ at higher levels suggests that the sea-level was fluctuating with bryozoan recolonization occurring after increases in water depth. The crinoidal facies represents dense crinoid colonies which acted as localized sediment baffles. Shale-wisped calcilutites are most common at or close to the base of the Waulsortian, where background shale deposition was significant. However at higher levels the increased carbonate production had a diluting effect. These facies have been related to the phases of Lees, Hallet & Hibo (1985). The bryozoan ‘reefs’ are considered to represent Phase A, while mottled calcilutites can be related to Phases B and C. The homogeneous calcilutites which display evidence of intense algal activity represent Phase D.

Ten silicified brachiopod taxa have been recovered from the Ben Suardal Limestone Formation (Durness Group) on the Isle of Skye, western Scotland. This Arenig fauna contains a new camerellid genus, Boreadocamara, and new species of each of the orthacean genera Archaeorthis, Fasciculina, and Oligorthis. Representatives of Billingsella, Finkelnburgia, Syntrophia, Syntrophopsis, and an indeterminate orthacean have also been recovered from etched residues of the Ben Suardal Limestone. The Skye fossils show strong affinities with the Scoto-Appalachian or American faunal province, in keeping with the inferred plate tectonic position of the Durness Group along the northwestern margin of the early Palaeozoic ‘Iapetus’ Ocean.

The first results on the periodicity in the carbonate/insoluble residue ratio of a (hemi-) pelagic calcilutite-marl succession 77.5 m thick, and late Berriasian, are presented. The succession forms part of the Miravetes Formation, near Caravaca, SE Spain. It starts at the base of the Calpionellopsis simplex Zone (D1) and terminates at the top of the Calpionellopsis oblonga Zone (D2). Depending on the time scale used a time interval between 1.1 and 2.5 ma is involved. The succession, comprising 360 layers, has been surveyed and sampled in detail (1275 samples). The ratio of carbonate and insoluble residue content is used as a crude measure reflecting the combined effect of carbonate productivity and terrigenous dilution. The variations in this measure are stationary in the wide sense. Spectral analysis demonstrates the presence of a dozen cyclicities. Diagenesis is not the primary cause of the cyclicities, although it may have enhanced the contrasts between individual layers. After transformation into time, several high powers of the discrete periodogram can be matched with the quasi-periodicities of the Milankovitch model. The highest peak, located at 646.4 cm, is interpreted as the short cycle of eccentricity, the peaks at 133.7, 115.8, 106.3 and 97.0 cm are associated with precession and the period of 2585.5 cm can be matched with the long eccentricity cycle. Finally, a period at 3878.2 cm within the range of low resolution matches a cyclicity between 600 and 750 Ka. The absence of significant powers at periods matching obliquity is explained by the low palaeolatitude of the area of deposition. From this interpretation of the spectrum, the time-span of the zones D1 plus D2 is estimated to fall between 1.2 and 1.5 Ma.

The Wenlockian Hogklint Beds of Gotland represent a “barrier zone” of large bioherms and intervening channels. Three bioherms sampled north of Visby consist of 53% calcilutite matrix and represent quiet-water mud-mounds with organism stabilization but no skeletal framework or properties of wave resistance. The dominant organisms are stromatoporoids (35%), crinoids (18%), tabulate corals (15%) and calcareous algae (13%). Large colonies are less than 0.5 m in size, have relatively simple, massive growth forms and provide few special habitats for other organisms. In consequence, the bioherm-dwelling fauna consists of unspecialized mud-dwellers with the same diversity and taxonomic composition as co-eval, level-bottom communities. No ecologic succession is apparent within bioherms, and an upward change from stromatoporoid to algal dominance reflects a simple change in physical conditions.

This work is the result of geological mapping on the scale 1:25,000 comprising an area of 220 km 2 , located in the Chapada Diamantina northwest of Morro do Chapeu town, in Bahia state. The stratigraphy of this area is represented, from bottom to top by Morro do Chapeu Formation, of the Chapada Diamantina Group (constituted by quartzites, representing 27% of the area); by Bebedouro Formation (formated by metassiltites, tills, flints, and arkosean quartzites, comprising 18% of the area); by Bambui Group (indicated by calcilutite, dololutitc, dolomite, marldolorrudites, and intraformational breccia, corresponding to 53% of the area); by Caatinga Formation (represented by monomitic breccia, sandstone, petromitic conglomerate, and limestone, representing 0,6% of the area), and unconsolidated sediments comprising 1,4% of the total area. The quartzites of the Morro do Chapeu Formation show transgressive-regressive alternations (with marine-coastal sediments), stood by presence of feldspar, possibiliting its division in two facies. The Bebedouro Formation was separated in two parts: inferior and superior members. Bambui Group, for its characteristics: color, texture, thickness of the layer, and sheets, may be divided into facies and subfacies, and it may be still made on type section to the area, since the Serra da Babilonia until extreme western part of the region.