Geochronology and evolution of a complex barrier, Younghusband Peninsula, South Australia

This study examines the southeastern end of the Younghusband Peninsula in South Australia at a location called The Granites in order to gain a better understanding of the processes of formation of the foredune ridge system, and to investigate the drivers that controlled its progradational development during the Holocene. Our findings are based on amorphological analysis, a ground penetrating radar survey, and 14C and OSL dating. The Younghusband Peninsula at The Granites was formed by an initial aggradational phase resulting in a single complex foredune ridge, and which ended around 4.3 ka, and by a regressive (progradational) barrier phase (750 m wide) that developed in the last 4.3 ka, under very low rates of progradation (0.38 to 0.09 m/yr). The last part of this phase shows significant foredune ridge building in the last 1000 years or so. Barrier progradation via foredune ridge development is likely an effect driven by lowwave energy that favored conditions for coastal stability and foredune formation. Paleontological and GPR data indicate a maximum sea-level of +1.23 to +1.5 m, respectively, during initial barrier development. The foredune ridge plain of the barrier experienced at least three phases of significant aeolian activitywith ages centered at around 3.9, 3.4 and 3.0 ka suggesting their occurrence at 500 to 400-year events. Computer modelling indicates that sediments for the progradational phase of the barrier were provided by the forced regression produced by a sea-level fall over the past 4.3 ka. The large foredune complex formed during the last phase of progradation could be the result of both the very low progradation rate of 0.09 m/yr, and periods of disturbance possibly related to enhanced storm activity.

The Influence of Main Factors on Deepwater Sediments

Western Siberia is a unique petroleum basin with exclusive geological objects. Those objects allow us to test various methods of sequence stratigraphy, systematization and evaluation approaches for reservoir characterization of deep-water sediments. Different methods have potential to decrease geological uncertainty and predict distribution and architecture of deep-water sandstone reservoir. There are many different parameters that could be achieved through analysis of clinoform complex. Trajectories of shelf break, volume of sediment supply and topography of basin influence on architecture of deep-water reservoir. Based on general principles of sequence stratigraphy, three main trajectories changes shelf break might be identified: transgression, normal regression and forced regression. And each of them has its own distinctive characteristics of deepwater reservoir. However, to properly assess the architecture of deepwater reservoir and potential of it, numerical characteristics are necessary. In our paper, previously described parameters were analyzed for identification perspective areas of Achimov formation in Western Siberia and estimation of geological uncertainty for unexplored areas. In 1996 Helland-Hansen W., Martinsen O.J. [5] described different types of shoreline trajectory. In 2002 Steel R.J., Olsen T. [11] adopted types of shoreline trajectory for identification of truncation termination. O. Catuneanu (2009) [1] summarize all information with implementation basis of sequence stratigraphy. Over the past decade, many geoscientists have used previously published researches to determine relationship between geometric structures of clinoforms and architecture of deep-water sediments and its reservoir quality. Significant amount of publications has allowed to form theoretical framework for the undersanding sedimentation process and geometrical configuration of clinoforms. However, there is still no relationship between sequence stratigraphy framework of clinoroms and reservoir quality and its uncertainty, which is necessary for new area evaluation.

Sedimentary Sequence, Evolution Model and Petroleum Geological Significance of Forced Regression: A Case Study of the Miocene Zhujiang Formation of the Pearl River Mouth Basin in the Northern South China Sea

Using 2D/3D seismic data and a large number of drilling and logging data and applying sequence stratigraphy, seismic sedimentology, and petroleum geology concepts, the characteristics of the sedimentary sequence of the forced regression have been analysed, the migration trajectory of the coastline have been reconstructed, the evolution model of the forced regression have been presented, and the significance for petroleum geology of the forced regressive sandbodies have been discussed. The falling stage systems tract (FSST) of the Zhujiang Formation present offlap high-angle oblique foreset reflection structure in the seismic profiles of the depositional trends and turbidite fan deposits with strong amplitude mound reflection structure are developed in the downdip direction of its front. The trajectory of migration of the shoreline shows a terraced downtrend in the direction of basin. The FSST is characterized by the shelf-edge delta without topset beds. The FSST was formed in the fall of relative sea-level. Five sets of foreset beds controlled by high-frequency relative eustatic were developed, therefore ordinal regressive overlap can be observed for the five sets of shelf-edge deltas in the depositional trends. The favourable reservoirs which were located close to the upper boundary of the falling stage systems tract and the basal surface of forced regression are sandbodies of the shelf-edge delta front and wave-dominated shoreface sands and the sandbodies of the turbidite fan. Those sandbodies favour the formation of lithologic oil–gas reservoirs by means of good trap sealing conditions, excellent oil–gas reserving performance, and effective oil source communication of fracture system.

Microclinoform structure of the BT10 horizon as a factor controlling the formation of gas fields in the southeastern part of the Yamalo-Nenets Autonomous Okrug

The microclinoform model of the Neocomian shelf reservoirs is becoming more and more supported by practicing geologists, since it allows to effectively address the problems arising in the development of complex reservoirs. According to modern concepts, the microclinoform structure is due to the intense progradation of delta complexes during periods of forced regression. The article demonstrates the effectiveness of the microclinoform concept in building a geological model of an accumulation in BT10 horizon of Zapadno-Chaselsky field, which is located in the southeastern part of the Russko-Chaselsky large swell in the southeast of the Yamalo-Nenets Autonomous Okrug. The microclinoform structure of the target was mapped based on the data volume of the second derivative of the wave field, which is more sensitive to changes in thicknesses, and porosities of sand reservoirs. As a result of comprehensive studies, correlation profiles and a GDE map of stratigraphic unconformity (top of BT10) were built reflecting the microclinoform structure of the target. The results were used to build a model of a gas reservoir and estimate its reserves. Hydrocarbon discoveries have already been made in the BT group of reservoirs at Zapadno-Chaselsky field and neighboring Yuzhno-Russkoye field that improves the potential of this interval within the southeastern part of the Yamalo-Nenets Autonomous Okrug. This poses the task of its more detailed study based on the microclinoform concept.

Stratigraphic distribution of the Codell Sandstone in the Denver Basin using wireline logs and core

Core data from five key wells spanning the Denver Basin were tied to wireline log data and used to interpret the distribution of the Middle Turonian Codell Sandstone Member of the Carlile Formation across the Denver Basin. The character of the Codell’s upper contact is sharp with a localized top-down truncation across the basin, which is consistent with an associated unconformity surface. In contrast, the Codell’s lower contact varies from being gradational in most of the southern Denver Basin to being unconformable in the northern basin. Log correlations reveal that the Codell is absent within an elongate northeast-trending swath up to 125 miles wide in northeastern Colorado. This elongate gap is herein referred to as the ‘No Codell Zone’ abbreviated as NoCoZo. Hypotheses to explain the absence of the Codell Sandstone in the NoCoZo include a lateral facies change from sandstone to shale, non-deposition of Codell-equivalent sediments across this area, post-depositional erosion, or a combination of these processes. Correlation of wireline logs across the northern and southern limits of the NoCoZo, combined with outcrop and core observations, suggest top-down erosion of the Codell increasing into the NoCoZo. However, the overlying Fort Hays Limestone is laterally continuous and has a relatively consistent thickness across the NoCoZo, suggesting two tenable hypotheses: 1) The NoCoZo represents an area of post-Codell erosion due to short-lived growth of a broad, low relief uplift that was no longer active during Fort Hays deposition; or 2) A stepped sea level fall and forced regression resulting in non-deposition of the Codell over this broad swath. North of the NoCoZo, the Codell thickens northward to more than 40 ft into adjacent parts of Wyoming and Nebraska. In this northern area, the Codell has two main lithofacies in three laterally correlative zones, in ascending order: a lower bioturbated siltstone to very fine-grained sandstone ranging from 2 to 20 feet thick, a middle 2 to 10-foot thick laminated to bedded siltstone to fine-grained sandstone, and an upper 5 to 20-foot thick bioturbated siltstone to very fine-grained sandstone. Southeast of the NoCoZo the Codell thickens to as much as 80 feet in an east-trending belt from Pueblo, Colorado, into west central Kansas. The southern Codell can be divided into two coarsening upward parasequences, from a basal muddy coarse siltstones to very fine-grained sandstones. The siltstones and sandstones in the southern Codell are mostly bioturbated with locally developed bedded facies at the top.

Evolution of a complex early Permian coarse-grained shoreline along a rift basin margin

Tectonic activity in extensional basins has a profound control on accommodation and sediment supply through the interplay between footwall uplift and hanging-wall subsidence, and thus largely influences the three-dimensional architecture of syn-rift sequences. This is emphasized in areas close to major rift-border faults, where steep coastal reliefs and fluvial gradients produce compound facies zonation and stratigraphic styles with strong lateral variability. The lower Permian High Cliff Sandstone was deposited in an array of shallow marine environments along the margin of the northern Perth Basin during a protracted late Paleozoic rifting episode in Western Australian basins. The formation is composed of fluvio-deltaic and nearshore strata sharply overlying a thick succession of offshore mudstone that was deposited during a phase of tectonic quiescence. This basal contact likely reflects submarine erosion and is, therefore, interpreted as a regressive surface of marine erosion generated in response to forced regression. The facies arrangement consisting of interbedded sandstone, conglomerate, and heterolithic facies chiefly records the evolution of a low- to high-gradient paleoshoreline punctuated by coastal streams, steep sea cliffs, and back-barrier lagoons. Extraformational outsized clasts were probably emplaced by the erosion of exhumed basement and older sedimentary rocks through fluvial incision, wave sapping, or landsliding. The along-strike variability between low- and high-gradient shoreline deposits indicates a dynamic depositional setting with a complex tectonic influence. The basal regressive surface of marine erosion is attributed to footwall uplift during the early reactivation stage of basin-bounding normal faults and, therefore, records the initiation of a new syn-rift phase in the northern Perth Basin.

Lifecycle of an Intermontane Plio-Pleistocene Fluvial Valley of the Northern Apennines: From Marine-Driven Incision to Tectonic Segmentation and Infill

Downcutting and infill of incised valley systems is mostly controlled by relative sea-level changes, and studies on valley-fill successions accumulated independently from relative sea-level or lake-level oscillations are limited. This study focuses on the Plio-Pleistocene evolution of a fluvial drainage system developed in Southern Tuscany (Italy) following a regional marine forced regression at the end of Piacentian. Subsequent in-valley aggradation was not influenced by any relative sea-level rise, and valley morphological and depositional history mainly resulted from interaction between sediment supply and tectonic activity, which caused segmentation of the major valley trunk into localized subsiding depocenters separated by upwarping blocks. Fluvial sedimentation occurred until late Calabrian time, when the major river abandoned that valley, where minor fluvio-lacustrine depocenters allowed accumulation of siliciclastic and carbonate deposits. The present study demonstrates that the infill of the valley was not controlled by the forcing that caused its incision. Accumulation of the fluvial succession is discussed here in relation with localized, tectonic-controlled base levels, which commonly prevent from establishing of a clear downdip stratigraphic correlations. Chronological reconstruction of the study depositional dynamics provides solid constrains to frame them in the tectono-sedimentary evolution of the Northern Apennines.

Frasnian-Famennian transition in western Thailand: conodonts, biofacies, eustatic changes, extinction

The biofacies of the Lower Palmatolepis rhenana Biozone to Palmatolepis triangularis Biozone in the Mae Sariang section, northwestern Thailand, are marked by alternations of Palmatolepis-dominated biofacies and Polygnathus-dominated biofacies related to fluctuations in seawater depth. Fine-grained limestone accumulated through the Lower Palmatolepis rhenana Biozone, Upper Palmatolepis rhenana Biozone, Palmatolepis linguiformis Biozone, Palmatolepis subperlobata Biozone, and Palmatolepis triangularis Biozone. A regression in the Upper rhenana Zone was followed by a recovery transgression that extended up through the linguiformis Zone. Conodont faunas increased until near the end of the linguiformis Zone, but in the overlying subperlobata Zone and triangularis Zone, conodont numbers dropped and most conodont species disappeared. It is possible the event coincides with a glacially forced regression, but there is no evidence of this in the section apart from a positive spike in δ13C. Another possible cause of the global marine extinction event is toxic levels of metals resulting from widespread volcanism. New taxa in this paper are Palmatolepis chaemensis new species, Palmatolepis thamensis new species, and Polygnathus tenellus surinensis new subspecies.UUID: http://zoobank.org/f2b55ba8-fe49-46f6-a2d5-bfd0208f1460

Sequence Stratigraphy towards its standardization—an important scientific scheme

In the Post-Exxon Era of sequence stratigraphy, various sequence models for the complex stratigraphic records with their response mechanisms are developed. All the models with strong pertinence are endowed, which lead to misapprehension in the conceptual system. Therefore, the standardization of sequence stratigraphy with the aim to provide consistency in the terminology has become an important motive of modern sequence. During the development of sequence stratigraphy, the identification and distinction between normal and forced regression have laid important foundation for the system description of sequence development. This becomes the first step towards the standardization because of model-independent nature. The introduction of model-independent unconventional system tracts in fluvial sequence models, which are low- and high-accommodation system tracts, which turn out to be another successful attempt of towards the standardization of sequence stratigraphy. The four parts of stratigraphic records, which include the complexity and cyclicity in the stratigraphic accumulation process; the non-gradual change and the non-integrity of the stratigraphic records; the variability represented by the diversity of the sequence models and the nature of standardization including variability, will provide more clues and approaches for further sequence stratigraphy development

Regional paleodepositional environment of the Cretaceous in the Great Australian Bight – a support for frontier exploration

To reveal the development of the depositional environment in the Great Australian Bight, regional and high-resolution 3D-seismic interpretation and palynological evidence from well data was integrated with tectonic plate- and paleo topographical-reconstructions. Results from that work explain the drainage patterns and changes in the sedimentary evolution. A maximum transgression at the Cenomanian–Turonian boundary causes the deposition of the expected main source rock interval at the base of the Tiger mega-sequence. This is supported by Integrated Ocean Drilling Program wells (2017), asphalite strandings and dredge samples from the basin. A relative sea-level drop in the mid-Turonian initiates a forced regression and sand deposition in more distal parts of the basin. As a third mega-sequence the Hammerhead Formation progrades into the basin, depositing several thousand metres of deltaic sandstones and lagoonal shales. Our source to sink model based on our gross depositional environment maps could explain the presence of source rocks and reservoir intervals within this frontier exploration basin.