Integration Of Sedimentology Research Articles

Variations of organic matter content and type within the sequence stratigraphic framework of the lacustrine deep-water Dongyuemiao formation, Sichuan Basin, Western China

The organic matter (OM) enrichment patterns and mechanisms in lacustrine deep-water shale successions were controlled by complex geological and biological processes, rather than any single factor. The integration of sedimentology, petrography, geochemistry, and sequence stratigraphy in the study of shale successions is vital to the development of robust paleoenvironmental interpretations and OM enrichment model. Based on a systematic sedimentological, petrographic, and geochemical analysis of three continuous cored wells of the Lower Jurassic Dongyuemiao Formation, Sichuan Basin, within a sequence stratigraphic framework, this study reports the complex geological responses in detrital input, sedimentation rate, benthic redox conditions, primary water column productivity, and OM enrichment pattern that caused by lake-level fluctuation. The results indicate that none of the proxies for detrital input, redox conditions, or productivity exhibit a significant correlation with total organic carbon (TOC) content in sediments. The OM enrichment was regulated by a complex interplay of these three factors, which is a function of relative lake-level fluctuation. In general, detrital input was decreased during lake-level transgression; whereas increased during lake-level regression. Reducing conditions and primary productivity were generally enhanced during lake-level transgression; whereas diminished during lake-level regression. Coupled relationships between lake-level fluctuation, bulk TOC content, and OM types were observed. The bulk TOC content and liptinite proportion in sediments increased gradually during the lake-level transgression. In contrast, the bulk TOC content and liptinite proportion in sediments gradually decreased during the lake-level regression. This general principle applies to both second-order and third-order lake-level fluctuation. Our study demonstrates that the development of a reliable OM enrichment model in lacustrine shale successions requires a comprehensive sequence stratigraphic framework.

Main controlling factors of organic-matter enrichment in the Ordovician-Silurian marine organic-rich mudrock in the Yangtze Block, South China

The Ordovician-Silurian organic-rich black shales located in the Wufeng-Longmaxi Formation in the southeastern part of the Upper Yangtze region are among the most important source rocks for shale gas in China. Given the importance of these sources, this study was initiated to determine the dominant factors controlling organic-matter enrichment in this region through the integration of sedimentology, petrology and geochemistry. Based on the sedimentary fabric features observed in thin section, six major mudrock lithofacies were identified in the Wufeng-Guanyinqiao-Longmaxi Formations black shale: (1) indistinctly laminated siltstone; (2) indistinctly laminated mudrock; (3) parallel-laminated mudrock; (4) nonparallel-laminated mudrock; (5) lenticular mudrock; and (6) normal-graded mudrock. Based on changes in the characteristics of lithofacies, trace-element ratios and the sizes of pyrite framboids, six kinds of mudrock facies were identified in the three formations. First, the indistinctly-laminated mudrock of the Wufeng Formation and the lower part of the Lower Longmaxi Formation that was deposited in a continuous suspension condition with pervasively anoxic and quiet water columns; second, the parallel-laminated mudrock of the upper part of the Lower Longmaxi Formation that was deposited from episodic suspension under an anoxic water column with weak fluctuation; third, the nonparallel-laminated mudrock of the lower part of the Upper Longmaxi Formation that was deposited in debris flow conditions with oxygen-rich and fluctuating water columns (graded mudrock deposited through event sedimentation in a suspension environment with a low-density, oxygen-rich bottom and turbidity currents also occurred in this stage); and finally, the indistinctly-laminated siltstones of the Guanyinqiao Formation and the upper part of the Upper Longmaxi Formation that were deposited in debris flow conditions with oxic and fluctuating water columns. The study then incorporated major- and trace-element analysis, global and regional sea-level fluctuations and regional stratigraphic characteristics to develop the depositional model. The results of the study indicate that the accumulation of organic matter in the middle region of the Sichuan Basin was predominantly controlled by regional tectonic activity.

High resolution sequence stratigraphic reconstruction of mud-dominated systems below storm wave base; A case study from the Middle to Upper Devonian Horn River Group, British Columbia, Canada

The application of sequence stratigraphy to deep-water mud-dominated systems is more challenging than in shallow water siliciclastic settings, largely because mudstones display subtle contrasts in grain size and lithology that make identification of facies and recognition of major stratigraphic surfaces difficult. However, the integration of sedimentology, ichnology and geochemistry and an extensive suite of cores from the Middle to Upper Devonian Horn River Group shales allow us to better understand how deep-water mud-dominated systems respond to fluctuations in the relative sea level, manifested in sequence stratigraphic relationships. The Horn River Group consists of, in ascending order, the Evie Member and Otter Park Member of the Horn River Formation and the Muskwa Formation. Four systems tracts, including highstand, transgressive, lowstand and falling stage systems tracts (HST, TST, LST, FSST, respectively) are identified and mapped. Highstand and transgressive systems tracts are both represented by dominantly massive mudstone lithofacies, sparse bioturbation, high Mo/Al ratios and high TOC values (avg. 3.1 and 3.4 wt%, respectively), as well as low Al2O3 concentrations. They can be distinguished by upward increasing gamma ray values for transgressive systems tracts and upward decreasing values for highstand systems tracts. The falling stage and low stand systems tracts display more heterolithic and laminated lithofacies, sparse to intense bioturbation, lower Mo/Al ratio and lower TOC values (avg. 1.2 and 1.7 wt%, respectively) and high Al2O3, concentrations and relatively low gamma ray readings. Sequence boundaries are represented by a transition from unbioturbated units to moderately or intensely bioturbated units, suggesting increased bottom water oxygen levels, which we infer to represent shallower waters. They are gradational and clearly conformable contacts in distal parts of the basin. They are sharp in more proximal settings, but no erosional surfaces were identified that would indicate unconformable contacts. Maximum flooding surfaces are characterized by the highest TOC contents and an increased gamma ray values. Our results suggest that the Otter Park Member belongs to a long-period sea level lowstand (e.g., 2nd order cycle), whereas the Evie Member and Muskwa Formation belong to long-period sea level highstands.

Trace fossils, sedimentary facies and parasequence architecture from the Lower Cretaceous Mulichinco Formation of Argentina: The role of fair-weather waves in shoreface deposits

Shorefaces can display strong facies variability and integration of sedimentology and ichnology provides a high-resolution model to identify variations among strongly storm-dominated (high energy), moderately storm-affected (intermediate energy), and weakly storm-affected (low energy) shoreface deposits. In addition, ichnology has proved to be of help to delineate parasequences as trace-fossil associations are excellent indicators of environmental conditions which typically change along the depositional profile. Shallow-marine deposits and associated ichnofaunas from the Mulichinco Formation (Valanginian, Lower Cretaceous) in Puerta Curaco, Neuquén Basin, western Argentina, were analyzed to evaluate stress factors on shoreface benthos and parasequence architecture.During storm-dominated conditions, the Skolithos Ichnofacies prevails within the offshore transition and lower shoreface represented by assemblages dominated by Thalassinoides isp. and Ophiomorpha irregulaire. Under weakly storm-affected conditions, the Cruziana Ichnofacies is recognized, characterized by assemblages dominated by Thalassinoides isp. and Gyrochorte comosa in the offshore transition, and by Gyrochorte comosa within the lower shoreface. Storm-influenced conditions yield wider ichnologic variability, showing elements of both ichnofacies.Storm influence on sedimentation is affected by both allogenic (e.g. tectonic subsidence, sea-level, and sediment influx) and autogenic (e.g. hydrodynamic) controls at both parasequence and intra-parasequence scales. Four distinct types of parasequences were recognized, strongly storm-dominated, moderately storm-affected, moderately storm-affected – strongly fair-weather reworked, and weakly storm-affected, categorized based on parasequence architectural variability derived from varying degrees of storm and fair-weather wave influence. The new type of shoreface described here, the moderately storm-affected – strongly fair-weather reworked shoreface, features storm deposits reworked thoroughly by fair-weather waves. During fair-weather wave reworking, elements of the Cruziana Ichnofacies are overprinted upon relict elements of the Skolithos Ichnofacies from previous storm induced deposition. This type of shoreface, commonly overlooked in past literature, expands our understanding of the sedimentary dynamics and stratigraphic architecture in a shoreface susceptible to various parasequence and intra-parasequence scale degrees of storm and fair-weather wave influence.

Sea-level reconstruction for Turonian sediments from Tanzania based on integration of sedimentology, microfacies, geochemistry and micropaleontology

Despite many advances in sea-level research, the nature of cyclic eustatic sea-level fluctuations during warm periods without, or with much reduced, polar ice remains enigmatic. Recently published δ18O records from extremely well-preserved Turonian microfossils from Tanzania do not support the contentious idea of glacio-eustatic control of global sea-level changes during the warmest period of the Cretaceous. For the same locality (site TDP 31) we reconstruct relative sea-level changes based on sequence stratigraphy and integration of sedimentology, microfacies, geochemistry, and micropaleontology. Four local sequence boundaries (SBs TuTz1–4) are recognized: at the base, middle, and top of the Helvetoglobotruncana helvetica Zone and in the Late Turonian. The lowstands are characterized by increased grain size, enhanced organic carbon flux, faunal assemblage changes, and bulk δ13Corg and foraminiferal δ13Cf and δ18Of minima. Strong benthic and planktic foraminiferal turnovers above the top Middle Turonian SB TuTz3 probably reflect shallowing (from upper slope to outer shelf) and/or eutrophication.The TDP 31 age model is refined through inter-regional comparison of planktic foraminiferal ranges and δ13C records from three other South-Tethyan localities (ODP Holes 762C and 763B, Exmouth Plateau, and the Guru section, Tibet). This age model enables correlation of the regressive events at a global scale and suggests that, within stratigraphic uncertainty, the TDP 31 depositional sequences are synchronous with the global Turonian third-order sequences and are likely driven by eustasy. These correlations, together with recent astrochronological and radiometric dating, indicate a considerably younger age (91.17±0.52Ma) for the top H. helvetica Zone than currently assumed, resulting in zonal duration of 2.35±0.52 myr. Foraminiferal stable-isotope data from TDP 31 indicate slight surface- and bottom-water warming during the regressions and possibly a minor surface-water salinity decrease, which is inconsistent with glacio-eustatic forcing of Turonian third-order sea-level cycles and is more in line with the model of aquifer-eustasy.

Uppermost Devonian (Famennian) to Lower Mississippian events of the western U.S.: Stratigraphy, sedimentology, chemostratigraphy, and detrital zircon geochronology

Upper Devonian to Lower Mississippian strata in Utah and Montana record global events through this important interval in Earth history. Late Famennian strata of the Beirdneau, Leatham, and Pilot Shale formations in Utah, and Three Forks and Sappington formations in Montana, record widespread deposition of generally fine-grained siliciclastic and carbonate strata. Integration of sedimentology, physical stratigraphy, chemostratigraphy, and published biostratigraphy allows for the recognition of important disconformities and regional stratigraphic patterns. These enable the reconstruction of uppermost Devonian to lowermost Mississippian depositional, tectonic, and eustatic history of the region. Carbon isotopic data allows for stratigraphic evaluation of the presence and absence of global bioevents of the Late Devonian, including the Annulata, Dasberg, and Hangenberg events, some of which are clearly recorded in hinterland deposits to the east in Colorado. While the Devonian–Mississippian boundary is also missing in our sections, a significant positive shift in δ13Ccarb in Lower Mississippian strata in Utah and Montana represents one of the largest positive δ13Ccarb isotope excursions of the Phanerozoic, linked to drawdown of atmospheric CO2 and glaciation in the Kinderhookian. Detrital zircon spectra from latest Devonian to Early Mississippian strata of Utah and Colorado include populations representing derivation from the Mazatzal and Yavapai provinces, Middle Proterozoic anorogenic granite bodies, and a small influx of Grenville and presumed Appalachian–Caledonian grains. Minor Paleoproterozoic and Late Archean peaks in Utah are likely multiple generation grains originally derived from the Peace River Arch of northwestern Canada and recycled in Ordovician rocks of Nevada. These patterns in detrital zircon geochronological data reflect, in part, changes in sediment dispersal patterns due to tectonic and eustastic variability within the Antler foreland basin during the Devonian–Mississippian boundary interval. This variability also led to irregular spatial patterns of unconformity development, as well as complicated physical stratigraphic and chemostratigraphic architecture.

3D geology and reservoir modeling in oil industry: Geologic model construction by integration of sedimentology, sequence stratigraphy, seismic geomorphology, exploration geophysics and geostatistics

3D geology and reservoir modeling in oil industry: Geologic model construction by integration of sedimentology, sequence stratigraphy, seismic geomorphology, exploration geophysics and geostatistics

Terreneuvian small shelly faunas of East Yunnan (South China) and their biostratigraphic implications

The study discusses the detailed composition of Terreneuvian small shelly fossil (SSF) assemblages of eastern Yunnan Province (Meishucun, Xianfeng and Huize regions). The described sections represent shallow water deposits of the Yangtze Platform that include a number of stratigraphical hiati. The reported SSF assemblages can be assigned to the regional SSF biozones I–III (Anabarites trisulcatus–Protohertzina anabarica Assemblage Zone; Paragloborilus subglobosus–Purella squamulosa Assemblage Zone; Watsonella crosbyi Assemblage Zone). Zones II and III are slightly redefined based on new data. Two subzones of Zone II are proposed here, namely, Annelitellus yangtzensis–Obtusoconus honorabilis Subzone and Maikhanella cambriana–Oelandiella korobkovi Subzone. Claviconchella qianyii gen. et sp. nov. and Bubiites simplex gen. et sp. nov. are reported. Here we also provide a critical revision of the SSF distribution for the well-known Meishucun section. The correlation scheme for East Yunnan documents the extent and duration of stratigraphical hiati. The distribution of SSFs and the lithological characterization indicate three major events of exposure of the carbonate platform resulting in sedimentary breaks and possible karstification. This prompts new consideration of the previously described stable isotope stratigraphy of shallow platform strata. Considering the complexity of the Terreneuvian Earth history as well as the uniqueness of SSF, an integration of sedimentology, geochemistry and paleontology is needed for future SSF study.

Using high-resolution stratigraphy and structural analysis to constrain polyphase tectonics in wedge-top basins: Inferences from the late Tortonian Scillato Basin (central-northern Sicily)

The present paper aims to show, both from a stratigraphic and structural points of view, the main features of a wedge-top syntectonic basin which evolved recording polyphase and non-coaxial tectonics. The study area is the Scillato Basin (SB), a roughly N–S-oriented structural depression located in the central-northern sector of the Sicililian Maghrebides. There, an approximately 1300m-thick upper Serravallian to upper Tortonian succession of clastic units outcrops as a portion of the Neogene syntectonic covers of the Sicilian fold and thrust belt. Within the outcropping succession the upper Tortonian Terravecchia Fm represents the main topic of this paper. A multidisciplinary approach was carried out through an integration of sedimentology, facies, stratal pattern and structural analyses; this was applied to the formation enabling one to recognize in the Scillato Basin a fining to coarsening upward succession, deposited recording an early transgressive and a late regressive depositional stage. In our model these two main depositional stages developed and are directly relatable to a two-step structural evolution of the basin. During the first step, a NW–SE-oriented structural depression existed, enclosed between structural highs and accommodating the lower and middle portion of the upper Tortonian succession. Subsequently, during the second step, the NW–SE depression was non-coaxially deformed by superimposition of high-angle transpressive faults (many of which were SE-dipping), developed in response to the upward propagation of structures enucleated at deeper structural levels. This step was recorded in the basin by development of both depositional and structural interferences recognizable along the upper portion of the Scillato Basin succession. A comparison between field data and deep geophysical data interpreted at the preliminary stage, raises questions about the late Miocene geological evolution of this sector of the Sicilian chain, including: (i) the syn-tectonic deposition of the Terravecchia Fm. in the Scillato Basin clearly recorded the interference of two main and non-coaxial tectonic events; (ii) the younger of these two events has a clear tranpressional character and was active during the very late Tortonian; (iii) as also indicated by many authors in neighboring orogenic wedges, the main control on the location, geometry and depositional evolution of the Scillato wedge-top Basin was carried out by compressional and transpressional structures developed at a deeper structural level. Their deformation propagated upward both into the shallow structural level and sedimentary covers; therefore (iv) the late Miocene structural scenario here depicted is not consistent either with the back-arc-related extension or with the late orogenic gravitational collapse models previously invoked by other authors with regard to this sector of the Sicilian thrust belt.

Stratigraphy of the Birdrong: an integrated approach

A detailed study of the Early Cretaceous Birdrong Sequence (S. areolata - P. burgeri) has been undertaken in the East Spar and Woollybutt fields, which lie in the northern end of the Barrow Delta complex in the Barrow Sub-basin, Northern Carnarvon Basin. This project integrates palynological, sedimentological and seismic stratigraphic interpretations to progress our understanding of the way in which the Barrow Delta evolved. The results will help develop remaining hydrocarbon prospectivity in the northern Barrow area. Palynological analysis within the Helby, Morgan and Partridge (2004) zonation scheme for the North West Shelf has enabled the identification of several significant biostratigraphic events, which have allowed further subdivision of the existing broad palynological zones. These palynological events represent influxes of specific dinoflagellate cyst taxa that may be tied to key stratal surfaces. These surfaces include transgressive ravinement surfaces, sequence boundaries and flooding surfaces. The palynological and sedimentological data, when combined, indicate a strong facies relationship between specific taxa and interpreted depositional environment. Such taxa include Gagiella, freshwater and brackish algae, and fully marine dinoflagellate cysts including Kaiwaradinium scrutillinum, Systematophora areolata, Phoberocysta neocomica and Cribroperidinium muderongense. The integration of sedimentology and palynology provides a powerful tool in interpreting depositional systems in shallow marine palaeoenvironments. Initial results indicate this may be used as a predictive tool for reservoir correlation and facies modelling. Key stratal surfaces identified through palynological and sedimentological study will be tested against 3D seismic to understand fully the stratigraphy of the study interval.

Integration of sedimentology and ground‐penetrating radar for high‐resolution imaging of a carbonate platform

AbstractGround‐penetrating radar has not been applied widely to the recognition of ancient carbonate platform geometries. This article reports the results of an integrated study performed on an Upper Jurassic outcrop from the south‐east Paris basin, where coral bioherms laterally change into prograding depositional sequences. Ground‐penetrating radar profiles illustrate the different bedding planes and major erosional unconformities visible at outcrop. A ground‐penetrating radar profile conducted at the base of the cliff displays a palaeotopographic surface on which the outcropping bioherms settled. The excellent penetration depths of the ground‐penetrating radar (20 m with a monostatic 200 MHz antenna) images the carbonate platform geometries, ranging between outcrop workscale (a few metres) and seismic scale (several hundreds of metres). This study supports recent evidence of icehouse conditions and induced sea‐level fluctuations controlling the Upper Jurassic carbonate production.

石油業界における3次元貯留層モデリング：堆積学・シーケンス層序学・サイスミック地形学・地震探査学・地球統計学の融合による地質モデルの構築

石油業界における3次元貯留層モデリング：堆積学・シーケンス層序学・サイスミック地形学・地震探査学・地球統計学の融合による地質モデルの構築

Cyclicity in the nearshore marine to coastal, Lower Permian, Pebbley Beach Formation, southern Sydney Basin, Australia: a record of relative sea‐level fluctuations at the close of the Late Palaeozoic Gondwanan ice age

AbstractThe Lower Permian (Artinskian to Sakmarian) Pebbley Beach Formation (PBF) of the southernmost Sydney Basin in New South Wales, Australia, records sediment accumulation in shallow marine to coastal environments at the close of the Late Palaeozoic Gondwanan ice age. This paper presents a sequence stratigraphic re‐evaluation of the upper half of the unit based on the integration of sedimentology and ichnology. Ten facies are recognized, separated into two facies associations. Facies Association A (seven facies) comprises variably bioturbated siltstones and sandstones with marine body fossils, interpreted as recording sediment accumulation in open marine environments ranging from lower offshore to middle shoreface water depths. Evidence of deltaic influence is seen in several Association A facies. Facies Association B (three facies) comprises mainly heterolithic, interlaminated and thinly interbedded sandstone and siltstone with some thicker intervals of dark grey, organic‐rich mudstone, some units clearly filling incised channel forms. These facies are interpreted as the deposits of estuarine channels and basins. Throughout the upper half of the formation, erosion surfaces with several metres relief abruptly separate open marine facies of Association A (below) from estuarine facies of Association B (above). Vertical facies changes imply significant basinward shift of environment across these surfaces, and lowering of relative sea level in the order of 50 m. These surfaces can be traced over several kilometres along depositional strike, and are defined as sequence boundaries. On this basis, at least nine sequences have been recognized in the upper half of the formation, each of which is < 10 m thick, condensed, incomplete and top‐truncated. Sequences contain little if any record of the lowstand systems tract, a more substantial transgressive systems tract and a highstand systems tract that is erosionally truncated (or in some cases, missing). This distinctive stacking pattern (which suggests a dominance of retrogradation and progradation over aggradation) and the implied relative sea‐level drop across sequence boundaries of tens of metres are remarkably similar to some other studies of continental margin successions formed under the Neogene icehouse climatic regime. Accordingly, it is suggested that the stratigraphic architecture of the PBF was a result of an Icehouse climate regime characterized by repeated, high‐amplitude cycles of relative sea‐level change.

Controversies in anesthesia for carotid endarterectomy: General versus regional anesthesia

Shorefaces can display strong facies variability and integration of sedimentology and ichnology provides a high-resolution model to identify variations among strongly storm-dominated (high energy), moderately storm-affected (intermediate energy), and weakly storm-affected (low energy) shoreface deposits. In addition, ichnology has proved to be of help to delineate parasequences as trace-fossil associations are excellent indicators of environmental conditions which typically change along the depositional profile. Shallow-marine deposits and associated ichnofaunas from the Mulichinco Formation (Valanginian, Lower Cretaceous) in Puerta Curaco, Neuquén Basin, western Argentina, were analyzed to evaluate stress factors on shoreface benthos and parasequence architecture.During storm-dominated conditions, the Skolithos Ichnofacies prevails within the offshore transition and lower shoreface represented by assemblages dominated by Thalassinoides isp. and Ophiomorpha irregulaire. Under weakly storm-affected conditions, the Cruziana Ichnofacies is recognized, characterized by assemblages dominated by Thalassinoides isp. and Gyrochorte comosa in the offshore transition, and by Gyrochorte comosa within the lower shoreface. Storm-influenced conditions yield wider ichnologic variability, showing elements of both ichnofacies.Storm influence on sedimentation is affected by both allogenic (e.g. tectonic subsidence, sea-level, and sediment influx) and autogenic (e.g. hydrodynamic) controls at both parasequence and intra-parasequence scales. Four distinct types of parasequences were recognized, strongly storm-dominated, moderately storm-affected, moderately storm-affected – strongly fair-weather reworked, and weakly storm-affected, categorized based on parasequence architectural variability derived from varying degrees of storm and fair-weather wave influence. The new type of shoreface described here, the moderately storm-affected – strongly fair-weather reworked shoreface, features storm deposits reworked thoroughly by fair-weather waves. During fair-weather wave reworking, elements of the Cruziana Ichnofacies are overprinted upon relict elements of the Skolithos Ichnofacies from previous storm induced deposition. This type of shoreface, commonly overlooked in past literature, expands our understanding of the sedimentary dynamics and stratigraphic architecture in a shoreface susceptible to various parasequence and intra-parasequence scale degrees of storm and fair-weather wave influence.

Stratigraphic process-response model for submarine channels and related features from studies of Permian Brushy Canyon outcrops, West Texas

This paper presents a process-response model for submarine channel-lobe systems based on the integration of sedimentology, architectural element analysis, paleogeographic reconstructions, and stratigraphy to characterize the migration patterns of the channel-lobe transition zone (CLTZ). In the Permian Brushy Canyon basinal cycle, deposition is the product of the basinward then landward migration of the CLTZ across the depositional profile (zonal or facies tract shift). This is expressed in outcrop by the vertical association of sandstone lobes overlain by channel fills capped by sandstone lobes. Linking these sedimentary bodies to their facies associations provides the framework for relating variable degrees of flow confinement to small-scale composite erosional depressions (less than 150 m wide by 5 m deep). This model identifies (1) coeval geomorphological expressions of the depositional profile and (2) the stratigraphic evolution of depositional cycles at every profile position. This permits relating facies associations to lateral and longitudinal changes in flow conditions at the time of deposition. Stacking patterns, geometry of sedimentary bodies and facies associations reflect fluctuations in flow volume and efficiency. Architectural element analysis differentiates evolutionary phases of channel-lobe systems. The power of the model lies in its ability to compare architecture and evolution across several scales of sedimentary bodies. Recognizing the vertical and lateral association of sedimentary bodies, arranged in a hierarchical order, permits understanding how the geomorphological building blocks of this depositional system change through time. Channel-fill, channel-flank and lobe strata represent the building blocks that form composite features documented at four scales. These range from tens of meters to several kilometers wide, by meters to hundreds of meters thick. Areal distribution of sedimentary bodies at each scale responds to specific controls, i.e. flow volume and topography. For example, channels extending basinward of a canyon mouth form local depositional topography that produces lateral migration of channel-lobe systems through time. This strongly controls the frequency of channel avulsion and lateral deposition.

High resolution sequence stratigraphic architecture of a transgressive coastal succession: Albian Bow Island Formation, southwestern Alberta

ABSTRACT We here present the first detailed published sequence stratigraphic study of the Lower Cretaceous Bow Island Formation. Two orders of sequences are identified, based on the integration of sedimentology, micropaleontology, ichnology and petrophysical characteristics. The studied interval encompasses two lower-order sequences. Shelf, shoreface, and coastal plain deposits of the lower and middle members of the Bow Island Formation form the transgressive and highstand systems tracts of the basal sequence. A major relative sea level fall caused a prolonged period of sub-aerial exposure and weathering of the deposits of the middle member of the Bow Island Formation, and farther to the east and northeast, incision of deep valleys into shoreface deposits of the Viking Formation. An overlying complex succession of tidal flat, estuarine, shoreface, and shelf deposits of the upper member of the Bow Island Formation and marine shales of the Westgate Formation represent the transgressive systems tract of the younger low-order sequence. Within the transgressive succession of the upper member of the Bow Island Formation and Westgate Formation, five higher-order sequences are identified. The high-order sequence boundaries are marked by basinward shifts of facies, incision of up to 15 m deep valleys and soil development on intervalley areas. This demonstrates that this period of overall sea level rise was punctuated by relative sea level falls, justifying subdivision into sequences rather than parasequences. Transgressive surfaces, often developed as prominent, pebble-mantled ravinement surfaces, subdivide the individual highorder sequences into lower and upper units. The lower units are comprised of tidal influenced incised valley fill, forming the main reservoirs, and tidal and storm influenced back-barrier lagoons deposited during lowstand and early transgressive periods. Foraminiferal assemblages were critical in distinguishing between these lagoonal deposits and open marine shoreface deposits. Deposits of the basal part of the upper units are characterized by a stepwise change towards more open marine conditions following each transgression, from marginal marine tidal flat and lagoonal deposits to shoreface and finally to shelf deposits of the Westgate Formation. This demonstrates the stacking in a retrogradational sequence set of the high-order sequences of the upper member of the Bow Island Formation and Westgate Formation. Erosion associated with the transgressions increases upward in intensity with each successive transgression with the greatest depth of erosion associated with the Westgate transgression. This reflects an upward increase in energy regime of the sedimentary environments that bypassed the area during the transgression. Within the overall transgressive upper member of the Bow Island Formation, an upward increase in the depth of incised valleys with each successive incision event likely reflects an upward increase in depositional relief due to the development of more open marine conditions and to the retrogradational and aggradational character of the upper member of the Bow Island Formation. The Westgate transgressive surface is a complex ravinement surface characterized by a westward, stepwise rise, indicating that it was formed during a period of gradual relative sea level rise, interrupted by phases of more rapid sea level rise. Establishment of this high-resolution sequence stratigraphic framework allows differentiation between these various generations of incision and thereby the mapping of the individual valleys and reservoirs associated with them. * Current address: Petroleum Geology, Saskatchewan Industry and Resources, 201 Dewdney Ave East, Regina, SK, Canada, S4N 4G3; E-mail: ppedersen@ir.gov.sk.ca End_Page 441------------------------

High resolution zonation within a tide-dominated deltaic reservoir: the Middle Jurassic Beryl Formation, Beryl Field, UKCS

The Middle Jurassic (Bajocian–Bathonian) Beryl Formation of the Beryl (Bravo) Field (Viking Graben), has been produced since 1979 and contains estimated remaining reserves of 180 × 10 6 BBL oil. Previous studies of this deltaic/shallow marine succession have defined five reservoir units. Production characteristics indicate that this lithostratigraphically-based zonation scheme does not adequately define reservoir flow units and constrain sweep efficiency. Here, a more refined reservoir zonation is used to form the basis for an upgraded reservoir simulation model. High density well coverage (50 wells) in the Beryl Bravo area allows the construction of a high resolution reservoir zonation scheme within the main producing interval of the Beryl Formation: Unit 3. The scheme is based on integration of sedimentology, ichnology, biostratigraphy, dynamic data and well log character. Nine reservoir zones (consisting of nine genetic sequences) have been defined and confirmed and are supported by drilling and production data. The complex reservoir zonation scheme is based upon the recognition of regionally extensive marine/brackish mudstones which, in many cases, form traceable pressure barriers across tilted fault blocks. This framework has allowed subdivision into 3 to 25 m thick correlatable units. Individual units record the progradation and transgression of tide-dominated deltaic deposits. Variations in the thickness and development of these units result from sedimentation in actively subsiding half-graben that were subject to regionally extensive base-level changes. The integrated approach taken here has substantially improved the understanding of the architecture and production characteristics of the Beryl Formation.

Abstract: Improvement of Sand Bodies Pinch-Out Description by Integration of Sedimentological and Seismic Data

Abstract: Improvement of Sand Bodies Pinch-Out Description by Integration of Sedimentological and Seismic Data

Porosity Prediction by Integration of Sedimentology and Burial History Data: Application to the Norwegian Sector of the North Sea: ABSTRACT

Porosity Prediction by Integration of Sedimentology and Burial History Data: Application to the Norwegian Sector of the North Sea: ABSTRACT

Integration of Sedimentological, Paleontological, Petrophysical, Paleomagnetic, and 3-D Seismic Data to Construct a 3-D Geological Model of the C Sands Reservoir, Maui Field, Offshore New Zealand

Integration of core descriptions with paleontological data and a core-derived paleomagnetic reversal stratigraphy has been used to interpret a conceptual depositional model for the Eocene C sands reservoir of the Maui gas-condensate field. The C1 sands were deposited as highstand, regressive shoreline sands that are partitioned by thin, tight transgressive deposits. Lowstand valleys were incised into these sediments in the eastern part of the field. On the basis of the paleomagnetic reversal stratigraphy, the fill of these valleys is demonstrably of a different age to laterally equivalent shoreline sediments. Dipmeter data indicate that the early fill of these valleys predominantly comprises flood-tidal sediments, deposited as relative sea level began to rise. This model has been extended from the cored wells by careful calibration and correlation of wireline logs from all wells. Both the landward and seaward pinch-out of the shoreline sands have been traced from amplitude displays of the three-dimensional (3-D) seismic data. The lateral extent of the lowstand valley fills is also defined by the 3-D seismic data. The well and seismic data have been combined within a sequence stratigraphic framework to construct 3-D geological models of the field that are consistent with the dynamic performance of the reservoir more » and will be used to construct a 3-D reservoir simulation model. « less