Detailed Facies Research Articles

Facies analysis and paleoenvironmental reconstruction of Upper Cretaceous sequences in the eastern Para-Tethys Basin, NW Iran

Upper Cretaceous mixed carbonate-siliciclastic sequences are among the most important targets for hydrocarbon exploration in the Moghan area, located in the eastern Para-Tethys Basin. Despite of their significance, little is known about their facies characteristics and depositional environments. Detailed facies analysis and paleoenvironmental reconstruction of these sequences have been carried out in eight surface sections. Accordingly, four siliciclastic facies, eight carbonate facies and one volcanic facies have been recognized. Detailed facies descriptions and interpretations, together with the results of facies frequency analysis, standard facies models and Upper Cretaceous depositional models of Para-Tethys Basin, have been integrated and a non-rimmed carbonate platform is presented. This platform was affected by siliciclastic influx, in the form of coastal fan delta and submarine fans in the shallow- to deep-marine parts, respectively. This model is interpreted to be shallower in the central and northeastern parts of the Moghan area. Toward the southeast and southwest, this shallow platform turns into deep marine settings along steep slopes without remarkable marginal barriers.

On the connectivity anisotropy in fluvial Hot Sedimentary Aquifers and its influence on geothermal doublet performance

This study finds that the geothermal doublet layout with respect to the paleo flow direction in fluvial sedimentary reservoirs could significantly affect pump energy losses. These losses can be reduced by up to 10% if a doublet well pair is oriented parallel to the paleo flow trend compared to perpendicular. The chance that flow paths are formed perpendicular to this trend strongly depends on the net sandstone volume in the reservoir. Detailed fluvial facies architecture realisations which are used in this study, are generated with a process-based approach utilizing geological data from the Lower Cretaceous Nieuwerkerk Formation in the West Netherlands Basin. Finally, this study emphasizes the importance of detailed facies architecture modelling for the assessment of both risks and production strategies in Hot Sedimentary Aquifers.

Friction- and Inertia-Dominated Effluents In A Lacustrine, River-Dominated Deltaic Succession (Pliocene Upper Valdarno Basin, Italy)

Abstract Sediment transport and deposition at river-dominated river mouths are controlled by: i) outflow inertia, ii) turbulent bed friction, or iii) outflow buoyancy. In mouth-bar-type deltas, which typically form in shallow-water settings, friction-dominated effluents are prevailing, although inertia-dominated ones may develop depending on: i) bedload at the river mouth and ii) water depth immediately downstream of the outlet. This paper deals with lacustrine river-dominated deltaic sediments deposited in a Pliocene, small, and protected lake, where wave reworking was limited to absent, allowing the preservation of the primary sedimentary features and stratal architecture developed by river-mouth sedimentary dynamics. This study focuses on sedimentary facies and stratal architecture of these deltaic deposits and aims at detecting the role of river floods in shaping and distributing sediment in shoalwater deltaic bodies. A detailed facies analysis resulted in the identification of sedimentary bodies related to friction- and inertia-dominated effluents, which appear to be genetically linked. High-discharge events promoted development of jet-flow deposits (i.e., from an inertia-dominated effluent) at the outlets of the main distributary channels, whereas during lower-discharge events minor channels bifurcated around the jet lobe feeding friction-dominated effluents giving rise to low-relief lobes. Coexistence of different types of jet deposits is also linked to deposition at different stages within a single flood event, with friction- and inertia-dominated bars accumulated during low- and high-stage flood discharge, respectively.

A multiproxy study of the early Pleistocene palaeoenvironmental and palaeoclimatic conditions of an anastomosed fluvial sequence from the Çameli Basin (SW Anatolia, Turkey)

A multiproxy study of the anastomosed fluvial succession from the Çameli Basin (SW Anatolia, Turkey) provides new insights on the palaeoenvironmental and palaeogeographical evolution of an extensional basin located at the top of western Taurides mountain range in the eastern Mediterranean. Detailed sedimentological, palaeontological and geochemical analyses on biogenic carbonates were carried out on the early Pleistocene (latest Villanyian) organic-rich fluvial succession in the Bıçakçı locality.Five main facies association groups characteristic of different sedimentary environments are recognized: (i) channel (CH), comprising lens-shaped bodies of fine- to medium-grained sandstones with minor siltstone interlayers; (ii) crevasse-splay (CS), including laminated siltstones and fine- to medium-grained sandstones sheets; (iii) pond (PD), containing laminated carbonaceous shales interbedded with siltstone or sandstone; (iv) swamp (SW), comprising coal beds with siltstone interbeds; and (v) floodplain (FP), including massive mudstones interbedded with siltstone and sandstone beds. Detailed facies analysis of the Bıçakçı succession reflects deposition on a floodplain which was traversed by a network of low-energy, well-defined channels separated by swamp and ponded areas in an anastomosed fluvial system.The Bıçakçı succession comprises a very rich micromammal fauna with a few large mammal remains, a rich variety of molluscs, plant macrofossils and pollen. This comprehensive record allows a multiproxy approach in reconstructing the early Pleistocene palaeoenvironment. The fauna and flora and stable isotope composition of the mollusc fauna of the Bıçakçı succession reflect vegetated quiet to slow moving freshwater shallow lakes and swamps under mostly cold and arid climatic conditions (stages 1 and 3) interrupted by a warm and subhumid interval (stage 2).The multiproxy record from Bıçakçı shows that early Pleistocene palaeoenvironments were predominantly open, steppe with some isolated shrubs and trees with forest at higher elevations. The very diverse landscape mosaics in the Çameli Basin during the early Pleistocene provided an excellent setting for refugia of Eurasian taxa. The biogeographic signature of mollusc and plant biota is predominantly modern Palaearctic with a minor amount of modern Palaearctic of the eastern Mediterranean, whereas mammal biota are dominated by extinct Palaearctic with a low proportion of the modern Palaearctic. During the early Pleistocene (2.25–2.1Ma), the palaeoclimate and palaeoenvironmental conditions in Bıçakçı correspond to climatic deterioration after the onset of northern hemisphere glaciation (NHG, ~2.55Ma) in the eastern Mediterranean.

Significance of seismites in the Late Cretaceous transgressive Nimar Sandstone succession, Son-Narmada rift valley, Central India

Detailed facies architecture study of the Late Cretaceous (Cenomanian) Nimar Sandstone (Bagh Group), from Son-Narmada rift valley, Central India, reveals deposition in a fluvial–marine environment. The lower part of the Nimar Sandstone succession depicts deposition in predominantly fluvial setting, whereas the middle–upper part of the succession manifests sedimentation under a tide-dominated estuarine to a tide–wave influenced shoreface environment. Retrogradational nature of the successions in the upper part and lateral facies change from west to east signifies an eastwardly decreasing marine influence. This attests to a sustained event of marine transgression from the west affecting the Son-Narmada rift valley during the Late Cretaceous time. Beds with various soft-sediment deformation structures (SSDS), viz., convolute laminae, load and flame structures, pseudonodules, contorted beddings, syn-sedimentary faults, and sand/silt dykes, occur in distinct stratigraphic levels within the middle part of the succession. These beds are separated by thick successions of undeformed beds. This paper reports these beds as seismites for the first time from the Son-Narmada rift valley. The seismites signify instantaneous liquefaction and fluidization of unconsolidated sediments triggered by passage of repetitive earthquake shock waves during sedimentation in fault-bound rift basin. These seismites are important as they mark a new phase of reactivation of the Son-Narmada South Fault within the Son-Narmada rift valley during the Cenomanian time. This reactivation of the Son-Narmada South Fault led to basinal subsidence under prevalent extensional tectonism, which controlled the sedimentation during the Late Cretaceous time. Copyright © 2016 John Wiley & Sons, Ltd.

Sequence stratigraphic framework for mixed aeolian, peritidal and marine environments: Insights from the Pennsylvanian subtropical record of Western Pangaea

AbstractDue to difficulties in correlating aeolian deposits with coeval marine facies, sequence stratigraphic interpretations for arid coastal successions are debated and lack a unifying model. The Pennsylvanian record of northern Wyoming, USA, consisting of mixed siliciclastic–carbonate sequences deposited in arid, subtropical conditions, provides an ideal opportunity to study linkages between such environments. Detailed facies models and sequence stratigraphic frameworks were developed for the Ranchester Limestone Member (Amsden Formation) and Tensleep Formation by integrating data from 16 measured sections across the eastern side of the Bighorn Basin with new conodont biostratigraphic data. The basal Ranchester Limestone Member consists of dolomite interbedded with thin shale layers, interpreted to represent alternating deposition in shallow marine (fossiliferous dolomite) and supratidal (cherty dolomite) settings, interspersed with periods of exposure (pedogenically modified dolomites and shales). The upper Ranchester Limestone Member consists of purple shales, siltstones, dolomicrites and bimodally cross‐bedded sandstones in the northern part of the basin, interpreted as deposits of mixed siliciclastic–carbonate tidal flats. The Tensleep Formation is characterized by thick (3 to 15 m) aeolian sandstones interbedded with peritidal heteroliths and marine dolomites, indicating cycles of erg accumulation, preservation and flooding. Marine carbonates are unconformably overlain by peritidal deposits and/or aeolian sandstones interpreted as lowstand systems tract deposits. Marine transgression was often accompanied by the generation of sharp supersurfaces. Lags and peritidal heteroliths were deposited during early stages of transgression. Late transgressive systems tract fossiliferous carbonates overlie supersurfaces. Highstand systems tract deposits are lacking, either due to non‐deposition or post‐depositional erosion. The magnitude of inferred relative sea‐level fluctuations (>19 m), estimated by comparison with analogous modern settings, is similar to estimates from coeval palaeotropical records. This study demonstrates that sequence stratigraphic terminology can be extended to coastal ergs interacting with marine environments, and offers insights into the dynamics of subtropical environments.

Depositional processes in the distal part of a large alluvial fan's feeder channel in Himalayan foothills, India

This paper presents results of detailed facies and architectural element analyses of the sedimentary fill of the Ranibag valley in the Himalayan foothills of north-western India. Forming a buffer zone between the source and sink of the Ganga foreland basin's Gola alluvial fan, the Ranibag valley is filled with coarse gravels comprising five distinct facies. These are clast-supported massive gravel, horizontal-bedded gravel, crudely bedded gravel, sandy gravel and matrix-supported disorganized gravel facies. The specific assemblages and sequences of these facies, defined by fifth- and fourth-order bounding surfaces, belong to mutually associated channel (CH) and gravel bar and bedform (GB) architectural elements. Both the elements have accreted only during floods by combined fluvial and debris-flow processes, but dominantly by the fluvial processes under conditions of high water-to-sediment ratio. Depositional processes in the valley are akin to those of the proximal alluvial fans of the Ganga Basin. Nonetheless, voluminous alluviation of coarser gravels in this extreme distal feeder channel valley has affected the fan processes downstream. It reduced the sediment budget and thus increased water-to-sediment ratio downstream to favour fluvial processes on the Gola fan. Copyright © 2016 John Wiley & Sons, Ltd.

Catastrophic landslide of medieval Portonovo (Ancona, Italy)

This paper is a case study about a natural catastrophic event that caused a human disaster in the medieval Benedictine enclave of Santa Maria in Portonovo—a large landslide involving some 5 million cubic meters of rock, which suddenly collapsed from the northeastern flank of the Monte Conero anticline hurling down from 400 m elevation over the littoral zone of the Portonovo bay, ∼9 km south of the Adriatic port city of Ancona. This landslide is the largest of the Conero Riviera, a 16-km-long, seismically active high coast with cliffs overhanging directly over the sea, which is therefore particularly prone to landsliding. While the landslide risk along the Conero Riviera has been evaluated by the local municipal authority, the risk in the Portonovo bay, a very popular beach resort, has been somewhat underestimated inasmuch as the huge landslide was previously considered, by geologists and geoengineers, to be a prehistoric event and therefore unimportant in the context of prevention plans aimed at assessing the hydrogeological instability of this area. We approached our study by surveying the area of the landslide using detailed ground truthing and geological mapping, and defining the geomorphology and lithologic composition of the landslide from head to toe. Radiocarbon dating of neritic mollusk shells from the autochthonous sediments underlying the landslide toe, which were retrieved from two drill cores from the toe of the landslide deposit, indicated that the landslide occurred in historical times, contrary to common belief that it occurred in prehistory. We then reconstructed the history of environmental changes of the Portonovo bay prior to, and subsequent to the landslide event using a detailed facies analysis of these two drill cores and of a third one drilled through the center of the landslide body. Written documentation about the medieval history of Portonovo, including an old map of the northeastern face of Monte Conero, which shows no evidence for the landslide, suggests that it occurred in the early fourteenth century, destroyed the strategic harbor of Novo Porto, and caused the definitive abandonment of the three-centuries-old Benedictine abbey of Santa Maria in A.D. 1320. The lithologic, structural, and rheologic setting of the steep northeastern flank of the Monte Conero anticline provided the predisposition for the huge medieval landslide, a structural setting possibly weakened by unusually intense seismic activity that affected the Conero Riviera from the late thirteenth to the early fourteenth centuries. The same structural and lithologic settings are found today on the slopes adjacent to the western side of the medieval detachment scar, thus representing a serious threat for the stability of the area and a high risk for imminent large landsliding, which may have grave consequences for present-day infrastructure and inhabitants of the popular Portonovo beach resort. Therefore, we present this work on the giant Portonovo landslide as an example of how interdisciplinary scientific investigation on hydrogeologically unstable areas may help in preventing human disasters.

Permian-Cenozoic deep-water carbonate rocks of the Southern Tethyan Domain. The case of Central Sicily

We present an integrated stratigraphy of the outcropping and buried Permian-Cenozoic deep-water carbonate successions, forming some of the tectonic units mostly buried beneath the Late Neogene sedimentary cover in the fold and thrust belt of Central Sicily. Three main successions, pertaining to the well known Lercara, Imerese and Sicanian domains, have been reconstructed on the basis of a detailed facies analysis, seismostratigraphic interpretation, bio -stratigraphy (mostly based on palynological data) and comparison between outcropping and subsurface deep-water sediments. The main results reveal a continuous sedimentation of the deep-water Southern Tethyan Sicilian succession since the Permian to Cenozoic. In detail: a ) the Permian-Middle Triassic terrigenous and carbonate deep-water successions, outcropping or buried in the Cerda, Lercara-Roccapalumba and Sosio Valley regions, are well comparable to each other and represent the common substrate of the Mesozoic-Paleogene Imerese and Sicanian carbonate successions; b ) the Mesozoic-Paleogene deep-water carbonates, when compared among them, reveal the occurrence of different sedimentary successions (Imerese and Sicanian); c ) the Oligo-Miocene foreland basin terrigenous sediments (Numidian flysch) clearly differ from the coeval foreland pelagic to open-shelf carbonates. The paleogeographic reconstruction envisages: a ) during the Permian-Triassic, a wide subsident continental rifting area, bordered by a shallow-water domain periodically supplying the basin with calciturbiditic to gravity flows sedimentation (rift stage of the Southern Tethyan margin); b ) during the Jurassic-Paleogene, two different deep-water basins developed in a context of a post-rift stage. The different sedimentation reflects the location of the Imerese and Sicanian basins, respectively, along adjacent rimmed shelf and stepped carbonate platform margins.

Facies analysis of the Semanggol Formation, South Kedah, Malaysia: A possible Permian–Triassic boundary section

Although the Permian–Triassic Semanggol Formation is widely distributed in northwestern Peninsula Malaysia and is made of various lithofacies, its sedimentology and possible relation with the Permian–Triassic boundary (PTB) were not considered before. In this study, detailed facies analysis was conducted for two sections of the Semanggol Formation at the Bukit Kukus and Baling areas, South Kedah to clarify its sedimentology and relation to the PTB. Four facies from the Permian part of the Semanggol Formation that were identified at the Bukit Kukus section include laminated black mudstone, interbedded mudstone and sandstone, volcanogenic sediments, and bedded chert. In Baling area, the Triassic part of the formation is classified into three members. The lower member comprises of claystone and bedded chert facies, while the middle member is composed of sandstone and claystone interbeds (rhythmite). On the other hand, the upper member is grouped into two main units. The lower unit is mainly claystone and includes two facies: the varve-like laminated silt and clay and massive black claystone. The upper unit is composed of various sandstone lithofacies ranging from hummocky cross stratified (HCS) sandstone to thinly laminated sandstone to burrowed sandstone facies. The HCS sandstones occur as two units of fine-grained poorly sorted sandstone with clay lenses as flaser structure and are separated by a hard iron crust. They also show coarse grains of lag deposits at their bases. The laminated black mudstone at the lowermost part of the Semanggol Formation represents a reducing and quite conditions, which is most probably below the fairweather wave base in offshore environment that changed upwards into a fining upward sequence of tide environment. Abundance of chert beds in the volcanogenic sediments suggests the deposition of tuffs and volcanic ashes in deep marine setting which continues to form the Permian pelagic bedded chert and claystone. The bedded chert in the lower member of the Triassic section suggests its formation in deep marine conditions. The rhythmic sandstone and claystone interbeds of the middle member are suggestive for its formation as a distal fan of a turbidite sequence. Lithology and primary sedimentary structure of the upper member suggest its deposition in environments range from deep marine represented by the varve-like laminated silt and clay to subtidal environment corresponds to the massive black claystone to coastal environment represented by the hummocky sandstone units and reaches the maximum regression at the hiatus surface. Another cycle of transgression can be indicated from the second hummocky unit with transgressive lag deposits that develops to relatively deeper conditions as indicated from the formation of relatively thick laminated sandstone and bioturbated massive sandstone facies that represent tidal and subtidal environment, respectively. Late Permian lithological variation from the radiolarian chert into early Triassic claystone probably resulted from a decrease in productivity of radiolarians and might represent a PTB in the Semanggol Formation. Volcanogenic sediments in the studied section can be used as an evidence for volcanic activities at the end of the Permian, which is probably connected to the nearby volcanic ash layers in the eastern China, the ultimate cause of the PTB in this area. Black mudstone in the Permian part of the studied section may be interrelated to the Latest Permian Anoxia that started to build in the deep ocean well before the event on shallow shelves.

Depositional model and sequential evolution of the upper Quintuco Formation in its type area: implications for paleogeographic reconstructions for the southern Neuquén Basin during the Valanginian

The Quintuco Formation (Berriasian-early Valanginian) in central Neuquén province comprise marine, transitional and continental deposits. These deposits were included in several regional stratigraphic studies since the 80’s but receiving little attention in terms of detailed facies analysis, palaeoenvironmental reconstructions and evolution. Understanding the evolutionary stage corresponding to cusp section of the Quintuco Formation and its relation with basal deposits of the Mulichinco Formation, is key to estimate the magnitude of associated change to the event of basin reconfiguration occurred in the early later Valanginian. In order to reconstruct the final stages of the evolution of the Quintuco Formation in its type locality (Sierra de la Vaca Muerta), a facial, architectural and sequence-stratigraphic analysis of the uppermost interval is presented. The study comprise the sedimentological description and interpretation of facies, combined with architectural analysis of key intervals. This allowed the identification of 7 facies associations, which represent the accumulation in prodelta (FA 1), delta front (FA 2 and FA 3), distal delta plain (FA 4 y FA 5) and proximal delta plain (FA 6 and FA 7). Subsequently, the spatial distribution of the different facies associations were analyzed and key surfaces related to significant changes in the depositional settings were identified across the investigated region. In this context, sequence-stratigraphic analysis of the studied interval was addressed and stacking patterns of the successions and vertical evolution of the interval are discussed. The upper interval of the Quintuco Formation represents the development of a deltaic system, where fluvial processes were dominant, but waves affected the off-axis parts of the system. The proximal areas were located towards the southwest with prodelta settings located toward the east. The delta system was built by successive shallowing-upward successions (15-40 m), bounded by regional transgressive surfaces, and with a long-term progradational staking. The reconstructed paleogeography for the last evolutionary stage of the Quintuco Formation suggest a well-established source area from the west-southwest, that would represent a new insight for paleogeographic settings for the southern Neuquén Basin during the Valanginian.

The Vaca Muerta–Quintuco system (Tithonian–Valanginian) in the Neuquén Basin, Argentina: A view from the outcrops in the Chos Malal fold and thrust belt

The Vaca Muerta–Quintuco system (uppermost lower Tithonian–lower Valanginian) is a thick shallowing-upward sedimentary cycle consisting of dark bituminous shales, marlstones, limestones, and sandstones, cropping out in the Neuquen Basin, west–central Argentina. This paper analyzes three outcrop sections in Chos Malal area, northem Neuquen province. Detailed facies analysis allows us to differentiate six facies associations, representing basinal to proximal outer ramp facies of a homoclinal carbonate ramp system (Vaca Muerta Formation) and basinal to shoreface facies of a mixed carbonate–siliciclastic shelf system (Quintuco Formation), prograding westward from the eastern margin of the basin. Two sequence hierarchies were recognized: 5 composite depositional sequences (third order) and 15 high-frequency sequences (fourth order). Fluctuations in organic matter content within the Vaca Muerta Formation suggest a relationship with depositional sequences, finding the highest values associated with transgressive systems tract, whereas the transition to the Quintuco Formation shows a strong decrease in total organic carbon. The x-ray diffraction studies show an increase of clay minerals and quartz in the transgressive systems tract of the Vaca Muerta Formation and an increase in the content of calcite in highstand systems tracts. This pattern is reversed in the Quintuco Formation. Our sequence stratigraphic approach contributes to the understanding of the relationship between organic matter, clay minerals, facies, stacking pattern, and relative sea level changes in this exceptional shale oil and shale gas unconventional reservoir. This study may be helpful for a better postulate of petrophysical and geomechanical models for unconventional exploration.

Reconstruction and evolution of Archean intracaldera facies: the Rouyn–Pelletier Caldera Complex of the Blake River Group, Abitibi greenstone belt, Canada

Subvertically- to vertically-dipping Archean strata provide an excellent opportunity to study synvolcanic structures and internal organization of subaqueous volcanic complexes. The Abitibi greenstone belt in Quebec, Canada, hosts a number of these volcanic complexes and specifically the unique Blake River Megacaldera Complex. The Blake River Megacaldera Complex is composed of (i) an initial shield phase known as the Misema Caldera and (ii) two graben-type calderas known as the New Senator and Noranda calderas. The southern portion of the New Senator Caldera, the focus of this study, is of particular interest as the structure hosts the 54 Mt Horne Au-rich volcanogenic massive sulfide deposit. Detailed facies mapping, coupled with geochemical and geochronological analysis at multiple outcrop localities throughout the city of Rouyn-Noranda, Quebec, show that the stratigraphy of the New Senator Caldera is dominated by subaqueous effusive mafic volcanic facies with local felsic effusive and intrusive deposits. With the incorporation of structural data, we have used synvolcanic faults and dyke complexes to divide these facies into specific blocks within this region, here renamed the Rouyn–Pelletier sector. This study focuses on the facies and characteristics of the Pelletier, Senator, and Glenwood blocks and identifies the Évain, Stadacona, and Chadbourne blocks. Geochronological analysis reveals that facies of the Glenwood Block are approximately the same age as those of the felsic flows of the previously identified Horne Block. Together, all extrusive and intrusive volcanic facies from the Stadacona unit north to the Horne Creek fault compose a large caldera complex known as the Rouyn–Pelletier Caldera Complex.

Facies and depositional architecture according to a jet efflux model of a late Paleozoic tidewater grounding-line system from the Itararé Group (Paraná Basin), southern Brazil

During the Late Paleozoic, the Gondwana supercontinent was affected by multiple glacial and deglacial episodes known as “The Late Paleozoic Ice Age” (LPIA). In Brazil, the evidence of this episode is recorded mainly by widespread glacial deposits preserved in the Paraná Basin that contain the most extensive record of glaciation (Itararé Group) in Gondwana. The Pennsylvanian to early Permian glaciogenic deposits of the Itararé Group (Paraná Basin) are widely known and cover an extensive area in southern Brazil. In the Doutor Pedrinho area (Santa Catarina state, southern Brazil), three glacial cycles of glacier advance and retreat were described. The focus of this article is to detail the base of the second glacial episodes or Sequence II. The entire sequence records a deglacial system tract that is represented by a proximal glacial grounding-line system covered by marine mudstones and shales associated with a rapid flooding of the proglacial area. This study deals with the ice proximal grounding-line systems herein interpreted according to lab model named plane-wall jet with jump. Detailed facies analysis allowed the identification of several facies ranging from boulder-rich conglomerates to fine-grained sandstones. No fine-grained deposits such as siltstone or shale were recorded. According to this model, the deposits are a product of a supercritical plane-wall outflow jet that changes to a subcritical jet downflow from a hydraulic jump. The hydraulic jump forms an important energy boundary that is indicated by an abrupt change in grain size and cut-and-fill structures that occur at the middle-fan. The sedimentary facies and facies associations show a downflow trend that can be subdivided into three distinct stages of flow development: (1) a zone of flow establishment (ZFE), (2) a zone of transition (ZFT), and (3) an established zone (ZEF). The proximal discharge is characterized by hyperconcentrated-to-concentrated flow due to the high energy and sediment-laden nature of the flows. At the transitional zone, a hydraulic jump produces a rapid shift of conglomeratic to sandy facies with associated scour features. Towards the distal zones, the jet detaches to originate a vertical turbulent jet characterized by more diluted flows. Discussion of fan facies and architecture within a framework of jet-efflux dynamics provides an improved understanding of grounding-line fans systems that produce coarse-grained strata commonly enclosed by fine-grained rocks. The results have clear implication in terms of prediction of facies tract and geometry of oil and gas reservoirs deposited under similar conditions. And also can be useful to identifying the position of a glacial terminus through time.

Sedimentology and sequence stratigraphy of the Zebbag formation (Upper Albian-Lower Turonian) from Saharan platform (Southeastern Tunisia)

Sedimentological and sequential analyses of the Zebbag formation, Upper Albian-Lower Turonian age, from the Tataouine basin have been carried out. These analyses were based on detailed logging of five field sections across the Dahar cliff (Southern Tunisia). Indeed, the study was built upon a detailed facies and microfacies analysis where five facies associations were found. In fact, they represent a spectrum of environments ranging from tidal flat, coastal lagoon, peritidal, shallow subtidal inner ramp, to shallow subtidal middle ramp settings. Our analysis allowed the recognition of five transgressive/regressive sequences which tend to decrease towards the south showing a progressive onlapping of the Zebbag formation carbonate on Saharan craton. The sedimentary infill of the basin documents one of the various types of lateral and vertical variations in component lithofacies assemblages. Besides, it appears that the Upper Albian-Lower Turonian time interval has recorded the interplay between the mostly eustatic and tectonic phases recorded on the Saharan platform of southern Tunisia.

Sequence Stratigraphic Analysis of the Youngest Nonmarine Sequence In the Cretaceous Ferron Notom Delta, South Central Utah, U.S.A.

Abstract This study evaluates the nature and internal complexity of high-frequency fluvial aggradational cycles and linked paleosols that were previously not recognized in nonmarine sequences of the Turonian Ferron Notom Delta in Central Utah. Detailed facies analysis of the ∼ 33-meter-thick youngest nonmarine sequence (Sequence 1) reveals 11 depositional facies that build 33 fluvial aggradational cycles, 9 fluvial aggradation cycles sets, and 3 sequences, in what was previously classified as a single 100 ka, 4th- or 5th-order sequence. Fluvial aggradation cycles in the succession are either simple floodplain bedsets or single channel stories that are bounded by paleosols or erosional surfaces. They represent depositional events that likely do not span more than 2 ka. Depositional periods are followed by short hiati (10 to < 400 a) characterized by subaerial exposure, and soil development, possibly reflecting floodplain abandonment or short-term river avulsions. Fluvial aggradational cycle sets show systematic stacking of fluvial aggradational cycles, and are analogous to parasequence sets. They are represented by either compound floodplain bedsets or multi-story channel sandstones, bounded by relatively mature paleosols or erosionally top-truncated. They represent multiple small-scale depositional events that span not more than 14 ka followed by relatively long (100 a to < 1 ka) hiati, characterized by subaerial exposure and soil development, which suggest a relationship to longer-term floodplain abandonment, due to either longer-term avulsion or fluvial entrenchment during base-level falls. Fluvial aggradational cycle sets are often capped by coals and carbonaceous strata. Marine trace fossils and dinocysts above coal beds suggest marine transgression due to compactional subsidence or sea-level rise. The scale of cyclicity of the fluvial aggradation cycle sets (14 ka) is similar to underlying marine parasequences (10 to 15 ka) and suggests that nonmarine and marine cycles have a similar control. Fluvial sequences are aggregates of fluvial aggradational cycle sets that are bounded by unconformities or their correlative conformities that represent longer periods (1 to 5 ka) of subaerial exposure and pedogenic development. Cyclicity on the sequence scale in this succession is attributed to high-frequency Milankovitch-scale (∼ 20 ka, 40 ka) rises and falls in sea level.

Modern morpho-sedimentological patterns in a tide-dominated estuary system: the Bay of Brest (west Britanny, France)

ABSTRACTLong-studied with respect to its sedimentological features (1897), the Bay of Brest (Western Britanny, France) is a textbook example of a tide-dominated estuary. Characterised by macrotidal conditions, this estuary system is sheltered from the open sea (Iroise Sea) by a narrow strait that partitions the wave tide influences and continental/marine inputs. Sediments are supplied to the bay both by rivers (the Aulne and Elorn rivers) and by marine tidal currents. This study presents new analyses of detailed facies and morphological patterns, based on the integration of multisource data compiling seabed sampling, swath and LIDAR bathymetry, and backscatter imagery. The Main Map, at a scale of 1:90,000, contains (1) a sedimentological distribution using the ‘Code Manche’ classification, (2) a morphological map, and (3) bathymetric mapping which presents the morphology of marine and terrestrial landforms. This work may lay the foundation for a future study on sedimentary transport in a unique and confined coastal environment.

Depositional Environments of the Miocene-Pliocene Siliciclastic Succession, Al Rehaili Area, North of Jeddah, Saudi Arabia

Abstract A detailed facies and depositional analysis of the Miocene–Pliocene siliciclastic-dominated sequence (ranges from 10 to 35 m thick) of siliciclastic succession below the basalt rocks have been carried out to interpret the depositional pattern, facies and sedimentary depositional environments. This siliciclastic-dominated succession, underlying Harrat Rahat, belonging to the Miocene–Pliocene is exposed at Al-Rehaili area, North Jeddah. Three main depositional units from bottom to top: Unit I, II and III are identified and correlated. These units comprise of gravels/conglomerates, sandstones, siltstones and mudstones. Sandstones below the basaltic rocks of Harrat Rahat generally contain about 30-70 % quartz, 10-50 % rock fragments, 10-20 % feldspar, 15-40 % detrital clay, 2-8 % iron oxides, and minor amounts of other components. Siltstones are distinguished from sandstones by their finer grain sizes of the quartz silt (45-70 % quart and higher proportion of clay (30-55% detrital clay minerals). Mudstones contain about 25-50 % quartz, 40-60 and detrital clay minerals, 2-8 iron oxides, and minor amounts of other components. Based on petrography, components, textures, fabrics, contacts nature, sedimentary structures, stratal geometry, and stratigraphic relationships, ten facies, covering the three depositional units are distinguished representing fluvial to lacustrine depositional conditions.

Sedimentology and environmental interpretation of the Coniacian deposits in the Saharan platform (SE Tunisia)

In southern Tunisia, the carbonate series of the Upper Cretaceous (from Turonian to Campanian) are widely present in the Saharan platform and the Chotts ridge. The study of several sections in this area permits analyzing these carbonates which help to determine their depositional environment. This study was based not only on a detailed facies but also on a microfacies analysis. Fourteen facies were identified. They could be organized in six facies associations which characterize a ramp environment ranging from tidal flat to middle ramp settings. These carbonates show considerable variations of facies and thickness with many syn-tectonic figures (slumps). This result contrasts the monotony of these series and indicates a very important sedimentary dynamics. This dynamic is controlled primarily by the reactivation of preexistent faults.

Integration of Markov mesh models and data assimilation techniques in complex reservoirs

We present a methodology that allows conditioning the spatial distribution of geological and petrophysical properties of reservoir model realizations on available production data. The approach is fully consistent with modern concepts depicting natural reservoirs as composite media where the distribution of both lithological units (or facies) and associated attributes are modeled as stochastic processes of space. We represent the uncertain spatial distribution of the facies through a Markov mesh (MM) model, which allows describing complex and detailed facies geometries in a rigorous Bayesian framework. The latter is then embedded within a history matching workflow based on an iterative form of the ensemble Kalman filter (EnKF). We test the proposed methodology by way of a synthetic study characterized by the presence of two distinct facies. We analyze the accuracy and computational efficiency of our algorithm and its ability with respect to the standard EnKF to properly estimate model parameters and assess future reservoir production. We show the feasibility of integrating MM in a data assimilation scheme. Our methodology is conducive to a set of updated model realizations characterized by a realistic spatial distribution of facies and their log permeabilities. Model realizations updated through our proposed algorithm correctly capture the production dynamics.