Massive Sandstone Research Articles

Sedimentary facies development of breccia deposit in Tanjung Sekakap-Tanjung Murau area, near Mersing, Johor, Peninsular Malaysia

Breccia dominated rocks outcropping in the Tanjung Murau - Tanjung Sekakap area have been deposited in a composite system of alluvial fans and Gilbert-type deltas. The sedimentary facies ranges from boulder-dominated facies at the bottom to gravelstone-sandstone-dominated facies at the top of the succession. Other recognized facies are disorganized boulder-cobble- supported breccia (Bd), crudely stratified cobble-boulder-rich breccia (Bs), crudely stratified cobble-rich gravelstone (Gs-1), disorganized clast-supported gravelstone (Gd), crudely stratified pebble-rich gravelstone (Gs-2), normally-inversely-graded gravelstone (Gn-i), crossbedded gravelstone (Gc), stratified sandstone (Ss), massive sandstone (Sm) and homogenous mudstone (Mh) facies. Alluvial fan association feature discontinuous breccias and gravelstones (facies Bd and Bs), where sheet-floods and debris flows are dominant. The gravelstone dominated facies Gd, Gs-1 and Gs-2 intercalated with facies Gc are associated with the topset-foreset of a Gilbert-type fan-delta. The Gilbert-type topset are represented by facies Gc, Gn-i and Gs-2 as well as facies Ss. The dominance of breccia and gravelstone facies of alluvial fan and Gilbert-type topset - foreset delta facies associations suggest that these sediments were deposited on a steeply sloping continental margin with a rate of deposition similar to the rate of subsidence.

Lithostratigraphy and depositional environments of the Pyeongan Supergroup (Carboniferous–Permian) in the Taebaek area, mid-east Korea

The Pyeongan Supergroup (Carboniferous–Permian) consists of a thick siliciclastic sequence (1700 m thick). Recent sedimentological work in the Taebaek area has refined the lithostratigraphic units: Manhang, Geumcheon-Jangseong, Hambaeksan, Dosagok, Gohan and Donggo formations in ascending order. The entire sequence is represented by thirteen sedimentary facies, which can be organized into seven facies associations (FA). The lower part of the Manhang Formation (FA 1) (Moscovian) consists of crudely cross-stratified conglomerate, massive sandstone and gray homogeneous siltstone, formed in shoreface off river mouth, whereas purple siltstone and grainstone of the upper part (FA 2) probably formed in a coastal plain environment. The Geumcheon-Jangseong Formation (Moscovian-Artinskian) consists of dark gray sandstone, dark gray shale, coal and bioturbated wackestone (FA 3) formed in a lagoonal environment. The Hambaeksan Formation (Kungurian) comprises milky white, crudely stratified, conglomerate, gray coarse sandstone and partly laminated black shale (FA 4), representing a shoreface progradation. The Dosagok Formation (Late Permian) is characterized by an alternation of purple fine sandstone and conglomerate (FA 5), formed in a bedload-dominated fluvial system. The Gohan Formation (Late Permian) is mostly composed of upward-fining units (massive sandstone to dark gray siltstone) (FA 6), suggesting a restricted inter-distributary bay environment. The Donggo Formation (?Late Permian) consists of cross-stratified coarse sandstone and purple sandstone (FA 7), interpreted as deposits of perennial, sandy braided river system.

Characterization of permeability distributions in six lithofacies from the Helsby and Wilmslow sandstone formations of the Cheshire Basin, UK

Abstract The lithofacies and permeability structure of the Abbey Wood borehole, near Delamere, Cheshire, UK, have been investigated so that permeability distributions can be established for characteristic sandstone lithofacies in the Permo-Triassic sandstone aquifer. The borehole penetrates the Helsby Sandstone and Wilmslow Sandstone formations and six major facies (coarse- and fine-grained fluvial channel fill sandstones, sandy sabkha, sand sheet and dune aeolian sandstones, and a massive sandstone facies) and one minor lithofacies, a mudstone facies, have been identified. The permeability distributions for each lithofacies show subtle systematic differences. The two fluvial sandstone facies and the massive sandstone facies have systematically lower permeabilities than the aeolian sandstones, and within the aeolian sandstones the sand sheet and dune sandstones appear to be systematically more permeable than the sabkha facies. Statistical tests on the permeability distributions of each facies indicate that the distributions are statistically distinct and so support the lithofacies classification.

深海底堆積物研究の進展：低海水準期堆積モデルの再構築

A falling-stage deep-water succession is characterized by sandstone-dominated channel-and-overbank deposits and age-equivalent depositional-lobe deposits. In contrast, a lowstand deep-water succession is muddier and is characterized by a thickening-upward pattern of distal overbank deposits. The base of the falling-stage deposits is characterized by a distinct erosional surface compared with the base of the lowstand deposits, which is commonly represented by a gradational contact to the underlying falling-stage deposits.Deep-water channels commonly exhibit meandering patterns similar to fluvial channels, and the channel-fill deposits are encased in muddy overbank deposits. The distribution patterns and volumes of coarse-grained channel-fill deposits developed mainly during falling- and lowstand stages can be estimated from outcrop and seismic data on the basis of several empirical relationships among width, depth, and sinuosity of deep-water channels. Hyperpycnal flows have recently been interpreted to be one of the important mechanisms for developing thick to very thick-bedded, deep-water massive sandstones (DWMSs). DWMSs commonly exhibit sheet-like geometry and abruptly thin out and fine to the downslope direction. These abrupt changes in thickness and grain size of DWMSs are interpreted to be a result of deposition of a sufficient volume of sand particles from precursor hyperpycnal flows, which are subsequently transformed into buoyant plumes with finer-grained sediment particles associated with residual lower-density turbidity currents flowing to the further downslope direction. Modulation and transformation of turbidity currents into debris flows at a channel-to-lobe transition zone were recognized. The transformation of turbidity currents into debris flows is interpreted to have occurred in response to incorporation of many siltstone clasts and finer-grained sediment particles into the precursor turbidity currents from muddy substrates. The finding indicates that a laterally continuous sandstone body from middle-fan channel to depositional lobe deposits internally contains muddy baffles, which develop heterogeneity of fluid flows in reservoir sands and sandstones.

Análise multiescalar de atributos sedimentares em depósitos fluviais paleogênicos na Bacia de Volta Redonda, RJ

This study aims to perform a multi-scale analysis of the sedimentary attributes presented by Paleogene fluvial deposits of the Volta Redonda Basin (Continental Rift of Southeastern Brazil), including the characterization of sedimentary facies, depositional architecture and petrographical features. The results from this study may be applied to the modelling of fluid behaviour inside fluvial reservoir-rocks. Among the studied deposits are the main aquifers of the sedimentary basins which compose the Continental Rift of Southeastern Brazil. The methodologic framework comprised: interpretation of an outcrop by using a photomosaic to the recognition of depositional architecture, emphasizing the stratigraphic surface hierarchy; facies characterization with vertical profiles; and petrographic analysis of selected samples. Two distinct facies associations were recognized, corresponding to Resende and Pinheiral formations. The Resende Formation deposits present a simple complexity heterogeneity style, with a wide lateral continuity. They are composed by decimetric layers of massive sandstones interbedded to clayey sandstones, showing a tabular geometry and few dozen-meters width. The contacts between these deposits are gradual. The Pinheiral Formation deposits present a medium complexity heterogeneity style, exhibiting frequent truncation of architectural elements, characterized by decimetric and dozen-meters width sandy layers with conglomeratic levels interbedded to thin pelitic intervals. These deposits present a extended lenticular geometry and irregular contacts. Microscopically, sandstones from Resende Formation present low porosity, related to the occurrence of clayey matrix resulted from feldspars alteration. The sandstones from Pinheiral Formation show porosities similar to reservoir patterns.

Neoproterozoic environmental change recorded in the Port Askaig Formation, Scotland: Climatic vs tectonic controls

The snowball Earth hypothesis suggests that the Neoproterozoic was characterized by several prolonged and severe global glaciations followed by very rapid climate change to ‘hot house’ conditions. The Neoproterozoic Port Askaig Formation of Scotland consists of a thick succession of diamictite, sandstone, conglomerate and mudstone. Sedimentological and stratigraphic analysis of Port Askaig deposits exposed on the Garvellach Islands was carried out to establish the nature of Neoproterozoic palaeoenvironmental change preserved in this thick succession. Particular emphasis was placed on identifying and distinguishing between climatic and tectonic controls on sedimentation. Port Askaig Formation diamictite units are attributed to deposition by sediment gravity flow processes or ‘rainout’ of fine-grained sediment and ice-rafted debris in a glacially influenced marine setting. Associated facies record various depositional processes ranging from sediment gravity flows (conglomerate, massive sandstone and laminated mudstone) to deposition under other unidirectional currents (cross-bedded and horizontally laminated sandstone). The Port Askaig Formation is also characterized by abundant soft sediment deformation features that occur at discrete intervals and are interpreted to record episodic seismic activity. Stratigraphic analysis of the Port Askaig Formation on the Garvellach Islands reveals three phases of deposition. Phase I was dominated by sediment gravity flow processes and sedimentation was primarily tectonically controlled. Phase II was a transitional phase characterized by continued tectonic-instability, an increased supply of sand to the basin and the preservation of current-generated facies. In the third and final phase of deposition, the interbedded units of sandstone and diamictite are interpreted to reflect development of large sandy bedforms and ice margin fluctuations in a tectonically stable marine setting. Sedimentological and stratigraphic analysis of the Port Askaig Formation demonstrates that tectonic activity had a significant influence on development of the lowermost parts of the succession. Climatic influences on sedimentation are difficult to identify during such phases of tectonic activity but are more easily discerned during episodes of tectonic quiescence (e.g.,, Phase III of the Port Askaig Formation). The thick succession of diamictite interbedded with current-deposited sandstone preserved within the Port Askaig Formation is not consistent with deep freeze conditions proposed by the snowball Earth hypothesis.

Integrated Approach To Develop Shaly, Interbedded Sandstone Reservoirs in Greater Burgan Field

Abstract The Greater Burgan Field of Kuwait has been producing for 57 years. The massive sandstone reservoirs have contributed the bulk of oil production. Large reserves are situated in interbedded sandstone reservoirs and will play a critical role in future Greater Burgan development. The current challenge is how to develop these reservoirs that have high uncertainty in net pay. In the recent past, several wells were completed in the interbedded sandstone sequences and no flow was reported. As a result, a review of log, core, fluid, well tests, PLT, pressure data, and the method of net pay determination has been done. The team's objective has been to develop an integrated understanding of the net pay intervals that can contribute to flow at a given API, viscosity, depth, and reservoir pressure. It is assumed that artificial lift may be available, and that drilling, workover, and completion practices do not result in any permeability or perforation damage. A conceptual model has been set up to study all the related parameters and to prove what contributes to making the well flow. Our simulation model includes vertical lift performance for the tubing size, the depth of the reservoir, and the hydrocarbon properties. The model has been calibrated using log, core, PLT, and well test data. This paper represents the details of the integrated study made to redefine net pay by improving and incorporating static and dynamic data. The objective is to guide the well completion strategy for interbedded sandstone reservoirs and reduce the uncertainty of remaining oil in place and reserves. The proposed methodology will influence future investments in infill wells, artificial lift, and improved oil recovery methods. Background The Greater Burgan Field of Kuwait has been in production from the upper Cretaceous Wara and Burgan formations. The bulk of the production has been comprised from the generally massive Third Sand Middle and Fourth Sand members of the Burgan formation. Other reservoirs such as Wara, Third Sand Upper, and Third Sand Lower members are primarily interbedded sand and shale reservoirs. These reservoirs have been deposited under various sedimentary systems typical of a delta plain environment. Some of the examples are distributory channel fills, interdistributory bays, overbank splays, bay fills, distributory mouth bars, delta front, and prodelta deposits. This diverse setting explains the complex heterogeneous nature of these reservoirs in the Greater Burgan Field. Formation Evaluation The development of the Greater Burgan Field has taken place over more than five decades; the petrophysical data demonstrate the evolution of formation evaluation tools and technology. The petrophysical data of the field consists of a wide range of different vintages and quality of data. It includes one of the first ever "electric logs." Petrophysicists have been consolidating, validating, and normalizing these data to ensure reliability and consistency of formation evaluation. Shale Volume Determination Shale volume (Vsh) has been of prime importance in developing an understanding of quality of pay. Vsh curves were calculated mainly on the basis of gamma ray (GR) and spontaneous potential (SP) data.

Imaging bed geometry and architecture of massive sandstones in the Fontanelice Channels, Italian Apennines, using new digiscoping techniques

In this study we present digital images and sedimentological data from a channel fill succession in the Italian Apennines that is dominated by massive sandstones. Although the studied outcrop is largely inaccessible, valuable data have now been obtained using the new technique of ‘digiscoping’, which allows features of < 10 cm to be resolved from a distance of several hundred metres. About 75–80% of the channel fill is composed of massive sandstone beds > 1 m thick, with overall sandstone : shale ratios of ∼9 : 1. Massive sandstones are poorly sorted and overall show little or no normal grading. They are commonly amalgamated and always have sharp bed tops. Massive sandstone beds show abrupt pinch-outs at the channel margin, whereas overlying thin-bedded siltstone/mudstone layers taper gradually and drape up the margin more extensively. This suggests that the depositing flows were stratified into a lower, thin, (hyper)concentrated density flow and an upper, more dilute, turbidity current. In summary, the digiscoping technique is shown to be a cheap and efficient method for imaging distant and/or inaccessible outcrops and providing information on bed geometry and architecture.

The first plesiosaur from the Primorye krai

Riabinin, 1915 wasfound by N.N. Tikhonovich in 1909 in the LowerSenonian (Coniacian–Santonian, 89–83 Ma) of Sakha-lin [3, 4]. This specimen is impossible to identify moreclosely than Plesiosauria indet. [1]. The teeth and ver-tebrae of the long-necked plesiosaurs Elasmosauridaewere found by L.A. Nessov in 1988 in the upper strataof the Koryak Formation (Upper Maastrichtian, 68–65 Ma) on the Pacific coast of the Chukotka Peninsula[4]. In the areas bordering on Russia (Korea, China, andJapan), plesiosaurs have not been recorded. In 2000,V.K. Popov discovered the fourth plesiosaur occurrencein the Far East; it was found during the geological sur-vey in southern Primorye in marine deposits of theKangauz Formation of the Upper Albian (103–98 Ma)on the right slope of the Sukhodol River (Kangauz),opposite the village of Novonezhino ( 43°12 ′ N, 132°35 ′ E), Primorye krai (Fig. 1). This is a caudal ver-tebra of a plesiosaur (specimen ZIN PH, no. 1/48, Pale-oherpetological collection of the Zoological Institute ofthe Russian Academy of Sciences). The bone beds arecomposed of dark greenish gray fine- and medium-grained tuffaceous sandstones, with carbonate material,containing abundant gastropod and bivalve shells, plantdetritus, and rare fragments of reptile bones. Thesesandstones are interbedded with siltstones containingplant remains. The presence of fragmentary reptilebones in these beds (Cape Sedlovidnyi) was first estab-lished in an unpublished report by N.A. Belyaevskiiand V.D. Prinada (1948). They found a relatively largefragment of a reptile bone (at least 45 cm long) incoarse-grained (gravellike) sandstones forming inter-beds in massive dense medium-grained sandstones inthe northern extremity of the Cape Sedlovidnyi (Khan-gan). This was the first finding of reptile bones in theNikanskaya Beds of southern Primorye. Subsequently,in the explanatory note to the geological map of Pri-morye, scale 1 : 500000 [5, p. 123], it was indicatedthat “…in siltstone deposits considered, vertebrates arerepresented by unidentifiable fish remains (scale andgill covers) and an imprint of a vertebral column, whilesandstone deposits have yielded large fragments of rep-tile bones.” Siltstones of these strata yielded conchost-racans, ostracodes, freshwater gastropods and bivalves,and plant imprints. From 2001 to 2003, V.S. Markevich,E.V. Bugdaeva (Institute of Biology and Soil Sciences,Far East Division, Russian Academy of Sciences), andYu.L. Bolotskii (AMURKNII) collected fish imprintsand unidentifiable fragments of reptile bones in out-crops on capes Palets and Sedlovidnyi.The strata described extend in northeast directionfrom Cape Sedlovidnyi (Andreev Bay) on the easterncoast of Ussuriiskii Gulf to the village of Novonezhino(Sukhodol River Basin) over a distance of more than20 km. Belyaevskii and Prinada (report, 1948)described bone-bearing beds in the green siltstonestrata dated Early Cretaceous. Subsequently, thesedeposits were assigned to the Cenomanian–Santonian(97–83 Ma) [5]. As a result of geological survey(1 : 200000), these strata were later assigned to theFrentsevka Formation dated Albian–Cenomanian(112–93 Ma) [6]. At present, these strata are recognizedas the separate Kangauz Formation dated Middle–LateAlbian (105–98 Ma) [7]. The Kangauz Formation iscomposed of siltstones, sandstones, tuffites, and con-glomerates and occurs on the eastern coast of Ussuri-iskii Gulf.The vertebra (Fig. 2) is platycelous, with circulararticular facets. The ventral side of the vertebral cen-trum is 23.5 mm long. The greatest height of the verte-bra, including the neural spine, is 48 mm. The posteriorarticular facet of the vertebral centrum is slightlyoblique. Its ventral margin, along with the articular fac-ets for the haemal arch, are broken off. The transverseprocess is stout, its base occupies the ventral area of theneural arch and the dorsal area of the vertebral centrum.The distal end of the transverse process expandsabruptly dorsoventrally. The transverse process is39 mm long. The vertebral foramen is relatively small.The prezygapophyses are broken off. The postzygapo-physes are shifted close to one another, located near themidheight of the neural arch. Anteroposteriorly, the

Reappraisal of the Cambrian glauconite-bearing Anse Maranda Formation, Quebec Appalachians: from deep-sea turbidites to clastic shelf deposits

The Cambrian Anse Maranda Formation is a glauconite-bearing clastic succession within the Quebec Reentrant. It is part of the Appalachians Humber Zone, particularly of the shale – feldspathic sandstone assemblage, which represents the rift-to-drift deposits of the Laurentian margin. The massive sandstones of the Anse Maranda were originally interpreted as the proximal turbidites of a deep-sea fan. The occurrence of glauconite and the high degree of bioturbation, which give the sandstones a massive aspect, suggest a different depositional environment. Detailed ichnology and lithofacies descriptions indicate that the Anse Maranda predominantly represents shelf sediments deposited in storm-influenced environment and that intense bioturbation destroyed most of the sedimentary structures. The paleo geographic reconstruction suggests that the Anse Maranda was deposited seaward of a headland identified as the Montmorency Promontory, along a narrow shelf with an irregular topography. Some coeval turbidites of similar composition were deposited in the deeper sub-basins. This reconstruction allows for sustained sediment-starved conditions to be maintained for more than 10 Ma and to produce anomalously thick glauconite-bearing succession. The bioturbation has influenced the diagenetic evolution of the Anse Maranda Formation. The laminated sandstones and burrows were cemented by early calcite, while the microporosity of the bioturbated sandstones lasted longer and permitted the formation of a muddy pseudomatrix.

Lower Cretaceous: the next target for oil exploration in the Barents Sea?

During the early days of exploration in the southwestern Barents Sea, Lower Cretaceous wedges and mounds were identified on seismic data along the margins of the Hammerfest Basin above rotated Jurassic fault blocks. They were ranked as secondary targets after the giant Jurassic closures in the central part of the basin. Drilling of the latter proved the Snøhvit area gas fields and Snøhvit’s thin oil leg. However, the majority of the wells drilled in the Hammerfest Basin have oil shows in Lower Cretaceous strata. Even the claystones in the most basinal part have oil shows, interpreted by the industry to be remnants of oil leaked from Jurassic reservoirs to the surface. Lower Cretaceous sandstones have also been drilled along the Troms–Finnmark Platform, Loppa High and Senja Ridge, where almost all wells have oil shows. Three wells drilled along the southern margin of the Loppa High have even proved small amounts of oil ranging from 31° API to 38° API and the westernmost well, 7120/1-2, is ranked as an oil discovery. Thick (123–157m) massive sandstones of Valanginian to Hauterivian age in wells 7120/1-2, 7122/2-1 and 7120/10-2 represent the reservoir analogues for a possible Lower Cretaceous oil giant. The Gamma gas discovery 7019/1-1 at the eastern margin of the Tromsø Basin could be an indication of such a giant. Lower Cretaceous sandstones were also the primary target for 7120/10-2. The reservoir sandstones were deposited as submarine fans and the drilled massive sandstones have good reservoir parameters.

Jotun Field reservoir geology and development strategy: pioneering play knowledge, multidisciplinary teams and partner co-operation – key to discovery and successful development

Accumulated knowledge from the early pioneering wells and subsequent exploration history led to the discovery of several fields in the Utsira High area during the 1990s. One of these, the Jotun Field, was discovered in 1994. The Jotun Field consists of three structures and is located on the western flank of the Utsira High, close to the eastern pinchout of the Tertiary submarine fan system. The reservoir at Jotun comprises Paleocene Heimdal Formation sands shed from the East Shetland Platform and transported across the Viking Graben area onto the Utsira High by high density gravity flow processes dominated by sandy turbidites. These distal gravity flow deposits display both thin-bedded sands alternating with shales and thicker, more massive sandstones (tens of metres thick). Minor sand injections occur throughout the field but are volumetrically insignificant. The production wells in one of the structures are completed in a slump and injection complex above thick massive reservoir sands. The Jotun Field development strategy was designed to optimize oil capture and minimize risk based on the interpreted reservoir geology. The initial development comprised 14 development wells: 12 horizontal producers, 1 water injector and 1 water disposal well. Production from the Jotun Field started in October 1999 and reached peak production in June 2000, with 140 000 BOPD. After exceeding initial expectations, declining production and rising water cut prompted an infill well programme, time-lapse seismic data acquisition and production logging in 2002. The first two wells were disappointing due to facies transition to interbedded sands and shales on the flanks of the structure and underprediction of oil–water contact movement. The newly available time-lapse seismic data were then integrated with production logging and updated depositional facies studies to evaluate additional drilling opportunities. The discovery, appraisal and development history of the Jotun Field serves as a good example of the key challenges in the Tertiary Utsira High play and the strength of applying multidisciplinary team efforts, partner co-operation and involvement to optimize asset value through tailored drilling and data acquisition programmes.

Cusp-corrugations due to boudinage nicely exhibited in the Flamierge area (High Ardenne, Belgium)

Cusp-corrugations with a highly ordered alignment are nicely exhibited in the Flamierge area. These structures due to boudi¬ nage are located on the bedding plane, at the top of a pelitic layer overlaid by a massive sandstone layer. Data measurements do not show significant variations between the different planes of cleavage and interboudin vein. In the thicker interboudin veins, crystal fibres are observed transverse rather than perpendicular to the walls of the veins. Such fibres, indicating dilatant shear and pro¬ gressive growth during boudinage, can be slightly curved and sometimes exhibit sigmoid shapes.

마젤란 분지의 백악기 심해저 하도 퇴적계의 퇴적상 및 진화

The Lago Sofia Conglomerate encased in the 2km thick hemipelagic mudstones and thinbedded turbidites of the Cretaceous Cerro Toro Formation, southern Chile, is a deposit of a gigantic submarine channel developed along a foredeep trough. It is hundreds of meters thick kilometers wide, and extends for more than 120km from north to south, representing one of the largest ancient submarine channels in the world. The channel deposits consist of four major facies, including stratified conglomerates (Facies A), massive or graded conglomerates (Facies B), normally graded conglomerates with intraformational megaclasts (Facies C), and thick-bedded massive sandstones (Facies D). Conglomerates of Facies A and B show laterally inclined stratification, foreset stratification, and hollow-fill structures, reminiscent of terrestrial fluvial deposits and are suggestive of highly competent gravelly turbidity currents. Facies C conglomerates are interpreted as deposits of composite or multiphase debris flows associated with preceding hyperconcentrated flows. Facies D sandstones indicate rapidly dissipating, sand-rich turbidity currents. The Lago Sofia Conglomerate occurs as isolated channel-fill bodies in the northern part of the study area, generally less than 100m thick, composed mainly of Facies C conglomerates and intercalated between much thicker fine-grained deposits. Paleocurrent data indicate sediment transport to the east and southeast. They are interpreted to represent tributaries of a larger submarine channel system, which joined to form a trunk channel to the south. The conglomerate in the southern part is more than 300 m thick, composed of subequal proportions of Facies A, B, and C conglomerates, and overlain by hundreds of m-thick turbidite sandstones (Facies D) with scarce intervening fine-grained deposits. It is interpreted as vertically stacked and interconnected channel bodies formed by a trunk channel confined along the axis of the foredeep trough. The channel bodies in the southern part are classified into 5 architectural elements on the basis of large-scale bed geometry and sedimentary facies: (1) stacked sheets, indicative of bedload deposition by turbidity currents and typical of broad gravel bars in terrestrial gravelly braided rivers, (2) laterally-inclined strata, suggestive of lateral accretion with respect to paleocurrent direction and related to spiral flows in curved channel segments around bars, (3) foreset strata, interpreted as the deposits of targe gravel dunes that have migrated downstream under quasi-steady turbidity currents, (4) hollow fills, which are filling thalwegs, minor channels, and local scours, and (5) mass-flow deposits of Facies C. The stacked sheets, laterally inclined strata, and hollow fills are laterally transitional to one another, reflecting juxtaposed geomorphic units of deep-sea channel systems. It is noticeable that the channel bodies in the southern part are of feet stacked toward the east, indicating eastward migration of the channel thalwegs. The laterally inclined strata also dip dominantly to the east. These features suggest that the trunk channel of the Lago Sofia submarine channel system gradually migrated eastward. The eastward channel migration is Interpreted to be due to tectonic forcing imposed by the subduction of an oceanic plate beneath the Andean Cordillera just to the west of the Lago Sofia submarine channel.

Three-dimensional distinct element modelling of relay growth and breaching along normal faults

Three-dimensional numerical models of neutral (i.e. slip-parallel) relay zones on normal faults that cut massive sandstone host rocks have been constructed using the distinct element method code, Particle Flow Code in 3-D (PFC 3D). The models successfully reproduce the geometries, displacement profiles and strains observed in natural relay zones. In contrast to boundary element method simulations, the modelled relay ramps dip towards the hanging wall, consistent with observations of most natural relay zones. The modelling shows that relay zones are stable structures that ‘grow’ by progressive rotation of an approximately planar relay ramp without significant propagation of the relay-bounding faults prior to breaching. Stable growth is terminated when a breaching fault propagates across the top or bottom of the relay ramp. Breaching fault propagation is not instantaneous and the ramp continues to rotate, and therefore transfer displacement between the relay-bounding faults, until they become fully hard linked. Following hard linkage, displacement is accommodated by slip on the through-going fault surface. The modelling results confirm previous conceptual models of relay growth and breaching based on geometric and kinematic analysis of natural relay zones.

Conditions for formation of massive turbiditic sandstones by primary depositional processes

It can be shown from bedform stability diagrams, that each turbidity current, regardless of whether its density is low or high, or whether its history is simple (e.g., surging flow) or complex (e.g., sustained flow), should pass through a final waning phase in which flow conditions are prone to bedform development. Yet, many thick deep-marine sandstones of supposed turbidity-current origin are totally devoid of tractional structures, such as plane-parallel lamination and ripple cross-lamination. TDURE, a mathematical model for the calculation of duration of sediment deposition from high-density turbidity currents (HDTCs), is used to show that the absence of Bouma T b and T c divisions cannot be explained by rapid temporal flow deceleration only. The model calculations imply that discernible tractional structures are formed, even at residence times within the upper-stage plane bed and ripple stability regimes of several seconds and several tens of seconds, respectively. Therefore, other explanations have to be sought for the absence of lamination in turbiditic massive sandstones. These include incompatible grain size, post-depositional removal or obstruction of lamination by bioturbation and liquefaction, and erosion of laminated divisions followed by rapid burial.

Provenance of Permian sandstones, South Kitakami Terrane, Northeast Japan: implications for Permian arc evolution

The sandstone petrography of the Permian sequence of the South Kitakami Terrane (SKT) suggests the disrupted development of a magmatic arc and subsequent scattering of the arc along the northern margin of the Sino–Korea continent. The SKT in northeastern Japan is a stratigraphic terrane with well-developed coherent sequences of Silurian to Lower Cretaceous extent on a pre-Silurian basement. While most of the pre-Tertiary terranes of the Japanese islands are regarded as accretionary in origin, the Permian deposits of the SKT are particularly well developed and unconformably overlie Carboniferous strata. These Permian deposits are overlain by Lower Triassic sediments and then Upper Triassic and Jurassic sediments with local unconformities. The Permian system is divided into Lower, Middle and Upper Permian units on the basis of lithofacies and fusulinid zonation. The Lower Permian is composed of sandstone, mudstone and limestone with a basal conglomerate. The Middle Permian unit is subdivided into a lower sequence consisting of massive sandstone and an upper sequence of limestone or mudstone associated with thick conglomerates. The Upper Permian unit is mainly composed of massive mudstone, although sandstone and conglomerates are predominant near the top of the unit. The provenance of the Permian sandstones in the SKT was investigated based on the petrography and chemical composition of detrital pyroxene grains. The Lower Permian sandstones can be divided into two petrofacies based on petrographic character; quartzose lithic sandstones derived from pre-Permian rocks, and volcanolithic sandstones dominated by andesitic fragments suggestive of a magmatic arc provenance. From the upper Middle to Upper Permian, the sandstone composition changes upwards from polymictic quartzofeldspathic to feldspathic. Detritus derived from the pre-Permian felsic volcanics and from contemporaneous magmatic arc volcanic–plutonic rocks are mixed in various proportions and deposited as Middle Permian sediments. The compositional variation within the Permian sequence reflects progressive denudation from undissected to dissected magmatic arc. The Triassic to Jurassic sandstones are derived from a continental provenance. The Permian–Jurassic sequences overall, therefore, records the transition of the tectonic setting of the SKT, from its development as an oceanic magmatic arc in the Permian to its accretion with a continental block by the end of the Triassic. This tectonic history and paleobiogeographic data suggest that the SKT may have originated as one of the terranes along the northern margin of the Sino–Korea Block.

New Important Iguanodontid and Theropod Trackways of the Tracksite Obernkirchen in the Berriasian of NW Germany and Megatracksite Concept of Central Europe

This article examines the high-resolution track horizon stratigraphy at the outcrop Obernkirchen. Massive sandstones, products of marine sand bar and fluviatile environments are present at the tracksite. Recently two track beds were examined in the outcrop. One new track slab of the lower track bed is described exposing well-preserved quadrupedal iguanodontid tracktypes of Iguanodontipus Sarjeant, Delair, and Lockley, 1998, and bipedal theropod tracks Megalosauropus Kaever and Lapparent, 1974. The ichnogenus Iguanodontipus is discussed and the diagnosis extended. The tracksite Obernkirchen belongs to a megatracksite of the ancient coastline of the marginal marine Hercynic Basin of the Lower Cretaceous of Europe, including the four well-known sites Obernkirchen, Bad Rehburg, Münchehagen, and Bückeburg of Northwest Germany. Three different tracktypes of huge sauropods, theropods, and ornithopods are abundant at basal Lower Cretaceous siliciclastic coastlines in different regions in Spain, Portugal, England, Germany, and Switzerland. Dinosaur tracks are also present in carbonate platform environments of northern Italy and Istria.

Sand-grade density flow evolution on a shelf-edge–slope–basin-floor complex in the Upper Jurassic Olympen Formation, East Greenland

The uppermost Callovian–Middle Oxfordian Olympen Formation is part of the early syn-rift succession of Jameson Land and Traill Ø, East Greenland and was deposited in prograding shelf-edge, slope and basin-floor environments. The formation consists of: (1) coarsening-upward units of sand-rich, prograding shelf-edge wedges; (2) slope and basin-floor mudstone; and (3) lenticular elongate and sheet-like, massive sandstone bodies deposited by sedimentary density flows on the slope, base-of-slope and basin floor. Systematic spatial and temporal variations in sandstone body geometry reflect down-slope transformations of the density flows. Lenticular and down-slope elongate sandstones mainly occur randomly scattered within prograding shelf-edge sandstone and slope mudstone. They represent short-travelled, hyperconcentrated density flows, filling pre-existing gullies that formed by retrogressive slumping. Sheet-like sandstones encased in mudstone were deposited from unconfined, concentrated density flows transitional to turbidity flows at the base-of-slope and on the basin floor. The Olympen Formation provides a well-exposed example of a sand-dominated shelf-edge–slope–basin-floor dispersal system in which the down-slope transformation of sand-grade density flows and resultant sandbody geometries can be demonstrated effectively. It may serve as a useful field analogue for a poorly understood but important type of hydrocarbon reservoir.

Anatomy of ancient passive margin slope systems: Aptian gravity‐driven deposition on the Vocontian palaeomargin, western Alps, south‐east France

AbstractThe Aptian succession on the Vocontian palaeomargin (south‐east France) consists of marl and marly calcareous pelagic slope facies together with a range of gravity‐driven deposits (slumps, debris‐flow deposits, turbidite packages and massive sandstones). The massive sandstones were emplaced by high‐density turbidity currents and are associated with extensive clastic sills and dykes. The sedimentology is constrained by a high‐resolution bio‐ and lithostratigraphic framework and permits a detailed analysis of the slope succession including: (1) a sequence stratigraphical analysis of the slope deposits; and (2) lateral tracing of individual sedimentary packages downslope. The resulting model for the Vocontian slope represents an alternative to the ‘classic’ Exxon delta‐fed, mud‐rich model. Key elements of the Vocontian model are: (1) an emphasis on lowstand slope erosion and complex slope morphology controlled by contemporary tectonism and salt diapirism; (2) slope deposition in confined erosional and structurally controlled conduits rather than the buildout of slope fans/channel‐levee complexes; (3) a dominance of large‐volume muddy slump and transitional debris‐flow deposits, with subordinate sandy turbidites, including significant massive sandstone facies; (4) common sand injections (sills and dykes) associated with the massive sandstone facies; and (5) minimal downslope evolution of the flows, with the nature of the source sediment being the over‐riding factor determining flow behaviour and deposit character. The Vocontian system is a rare instance in which large sections of a ‘fossil’ passive margin slope are preserved in the geological record. The slope deposits differ from the classic models of turbidite systems that have mainly been built from peripheral foreland basins, and the new insight makes it possible to compare ancient and present‐day passive margin slope systems.