Sequence Stratigraphic Interpretation Research Articles

셰일층의 순차층서 분석법

셰일층의 순차층서 분석법

Sedimentary dynamics along carbonate slopes (Bahamas archipelago)

AbstractHydroacoustic and sedimentological data in the Santaren Channel covering both the leeward slope of Great Bahama Bank and the windward slope of Cay Sal Bank allow new insights into carbonate platform slope sedimentation. The data document the interplay between depositional and erosive processes on both slopes through time and provide information on the current regime and its influence on the slope sedimentary processes. This study emphasizes the diversity and complexity of the slope morphology and the sediment distribution of the youngest high‐frequency sequence, which has developed since the last glacial maximum. The processes triggering slope failures and the formation of channels and gullies differ on both slopes. At the leeward slope of the Great Bahama Bank, extensive slope failures occurred primarily during sea‐level lowering following an interglacial. These slope failures created a slope morphology that channelizes the exported platform sediments during the subsequent highstand. At the windward slope of Cay Sal Bank, contour currents and the local tectonic regime are responsible for slope failures. During sea‐level lowstands, downwelling induces turbidity currents. The interaction of turbidity and contour currents leads to the formation of a system of furrows and slope‐parallel sediment ridges. The discovered heterogeneities in slope sedimentation improve the understanding of carbonate slope sedimentation and provide implications for sequence stratigraphic interpretation of carbonate platform slopes.

Depositional facies and ichnology of a tidally influenced coastal plain deposit: the Ogwashi Formation, Niger Delta Basin

The Ogwashi Formation is re-interpreted as tidally influenced coastal plain deposit based on the detailed outcrop description of exposures and facies analysis. Facies associations comprise strata interpreted to be the deposits of the following environments: fluvio-estuarine channels, tidal channels, tidal flats, coastal plain channels and coastal floodplain/mire. The fluvio-estuarine channels deposits are characterised by high-energy conglomerate and coarse-grained sandstone that are strongly to weakly bioturbated with trace fossils belonging to the Skolithos and the depauperate Cruziana ichnofacies. The tidal channel deposit contains mud chips and mud lenses (at the base) and includes mud draped planar and trough cross-beds. The tidal flat deposit comprises sandy heterolithic sediments that are intensely burrowed. The coastal plain channel deposits are mud-filled channels, with sand sheets interpreted as splay deposits and variegated sandy claystone which has undergone pedogenic alteration. The floodplain and mire deposits are light grey mudstone and dark grey carbonaceous mudstone with plant remains and lignite. These depositional successions show a change from marine to non-marine conditions, interpreted to be a result of relative sea level changes. The architectural elements of the coastal plain succession are grouped into channelised, sandy cross-stratified and floodplain deposits. The channelised elements occur either as isolated or as multistorey channel deposits. Sequence stratigraphic interpretation reveals one depositional sequence with a sequence boundary and an erosive transgressive surface of erosion identified by the occurrence of the Glossifungites ichnofacies with sharp, erosive contacts.

Sand Compositional Changes As A Support For Sequence-Stratigraphic Interpretation: The Middle Upper Pleistocene To Holocene Deposits of the Roman Basin (Rome, Italy)

Abstract Sand composition is one of the factors of a stratigraphic succession that best records the interaction between allogenic and autogenic processes. This is particularly true for the Quaternary successions where the effects of this processes are better recognized and differentiated. The Quaternary succession of the Roman Basin and, in particular, the one developed during the late early Pleistocene to Holocene, records a close interaction among tectonic uplift, volcanism, climate, and glacio-eustasy. Such interaction is reflected in a complex stratal pattern and stratigraphic architecture where high-rank and low-rank depositional sequences are developed and where qualitative and quantitative changes in sand composition are recorded in the same systems tracts. The analyzed succession corresponding to the high-rank Ponte Galeria sequence (PGS) was supplied by the Tiber River and its tributaries, which developed along the Latium Tyrrhenian margin; such deposits include sediment derived from carbonate to siliciclastic Meso-Cenozoic rocks and from Pleistocene volcanic complexes of the Roman Magmatic Province. We defined three main sand petrofacies (A, B, C) that have a good correspondence with lowstand (LST), transgressive (TST), and highstand (HST) systems tracts of PGS, which reflect changes in sand composition and sand provenance under the effects of tectonism, volcaniclastic input, sedimentary processes, and relative sea-level variations. Petrofacies A is feldspatho-litho-quartzose to feldspatho-quartzo-lithic in composition. It records the erosion and influx of siliciclastic and carbonate rock detritus without volcanic input into the LST fluvial and coastal sands of the PGS. Petrofacies B is characterized by a modal composition varying from feldspathic to litho-feldspathic and feldspatho-quartzo-lithic. It characterizes the TST of the PGS and reflects the abrupt and rapid introduction of volcaniclastic sediment into the system. Petrofacies C is feldspatho-quartzo-lithic in composition. This petrofacies characterizes the HST of PGS and, with respect to the other two petrofacies, better records the effects of downstream transport and river-mouth sedimentary processes. Sand samples collected from ancient deposits are similar in composition to the modern Tiber River, suggesting provenance from a similar river system. Results show that tectonism during middle–upper Pleistocene volcanic activity in the Sabatini, Cimini, and Vulsini volcanic complexes played a major role controlling stream-network reorganization in the Tiber drainage basin and resulted in enhanced volcaniclastic input from ash fall and recycling of pyroclastic flows. Volcanic input (volcanic lithics and associated phenocrysts) and postdepositional alteration during paleosol development define pre-, syn-, and post-volcanic compositions in the high-rank Ponte Galeria depositional sequence. In low-rank depositional sequences, several processes produced variable quartz/feldspar and quartz/lithic ratios, as well as textural changes; these include hydraulic sorting during fluvial and coastal transport and postdepositional in situ weathering processes. Weathering and pedogenic processes in the source area (catchment) potentially remove provenance information, reducing correlation potential of petrographic signatures of proximal successions in the Tiber River sedimentary basin. This work tests the effectiveness of using variation in sand composition as a tool in sequence stratigraphy.

The Glossifungites Ichnofacies and Sequence Stratigraphic Analysis: A Case Study from Middle to Upper Eocene Successions in Fayum, Egypt

ABSTRACTThe Glossifungites Ichnofacies was erected by Dolf Seilacher (the father of modern ichnology) in the mid-nineteen sixties to encompass burrows excavated into firm or compacted substrates. Correspondingly, this firmground ichnofacies has been used extensively in the identification of omission surfaces and the identification and interpretation of sequence stratigraphic discontinuities. A case study from Eocene strata in the Fayum depression of Egypt presents an opportunity to showcase a genetic approach for classifying occurrences of the Glossifungites Ichnofacies. More than twenty-five Glossifungites Ichnofacies–demarcated surfaces are documented and examined in this study. Based on the origin and character of these discontinuities, the examined surfaces are grouped into two main types: those of autogenic origin and those of allogenic derivation. The allogenically generated expressions of the Glossifungites Ichnofacies are associated with key-stratigraphic discontinuities of sequence stratigraphic significance and are the most common in the Eocene succession. Such surfaces are attributed, herein, to transgressively modified sequence-bounding discontinuities (FS/SU), systems tract-bounding surfaces (maximum flooding surfaces, MFS, and transgressive surfaces, TS), and finally parasequence-bounding surfaces (flooding surfaces, FS). These Glossifungites Ichnofacies-demarcated surfaces have proven to be crucial in the sequence stratigraphic interpretation of the middle to upper Eocene succession in the Fayum depression.

Comment on Non‐unique stratal geometries: implications for sequence stratigraphic interpretations, by: P.M. Burgess and G.D. Prince,Basin Research(2015) 27, 351–365

AbstractThe non‐unique variability highlighted by Burgess & Prince (Basin Res. 2015,27, 351) (i.e. the origin and timing of maximum flooding surfaces, maximum regressive surfaces and subaerial unconformities; the process of topset aggradation in relation with the various types of shoreline trajectory; and the multiple controls that may affect the progradation and retrogradation of a shoreline) is irrelevant to the workflow of sequence stratigraphy. What is relevant is the observation of the unique stratal geometries that are diagnostic to the definition of all units and surfaces of sequence stratigraphy. In downstream‐controlled settings, these unique stratal stacking patterns relate to the forced regressive, normal regressive and transgressive shoreline trajectories. Multiple controls interplay during the formation of each type of stacking pattern, including accommodation, sediment supply and the energy of the sediment‐transport agents. This interplay explains the non‐unique variability, but does not change the unique criteria that afford a consistent application of sequence stratigraphy. Failure to rationalize the non‐unique variability within the context of unique stratal geometries is counterproductive, and obscures the simple workflow of sequence stratigraphy.

Reply to Comment of O. Catuneanu and M. Zecchin on Non-unique stratal geometries: implications for sequence stratigraphic interpretations, by: P. M. Burgess and G. D. Prince, Basin Research (2015) 27, 351-365

Reply to Comment of O. Catuneanu and M. Zecchin on Non-unique stratal geometries: implications for sequence stratigraphic interpretations, by: P. M. Burgess and G. D. Prince, Basin Research (2015) 27, 351-365

Stratigraphic evolution of an estuarine fill succession and the reservoir characterization of inclined heterolithic strata, Cretaceous of southern Utah, USA

Abstract This study documented the architecture of a paralic succession using outcrops of the Upper Cretaceous John Henry Member of the Straight Cliffs Formation, southern Utah (USA). The 65 m thick interval of interest includes a basal succession of elongate tidal bars, which sits unconformably on the Calico Bed of the Smoky Hollow Member. These barforms are overlain by carbonaceous estuarine bay fill with tidal deposits, a bayhead delta and, ultimately, a coastal plain succession. The estuarine succession demonstrates a decreasing tidal influence through time and this is interpreted to reflect evolution from a mixed-energy to a wave-dominated estuary as a result of the changing morphology of the estuary and/or the migration of barrier islands across its mouth. The regional correlations are also discussed, with implications for sequence stratigraphic interpretations. A detailed interpretation of the ancient bayhead delta highlights the internal architecture and provides data for statistical comparison between this feature, which is dominated by inclined heterolithic strata, and a previously published study of fluvial point bar inclined heterolithic strata. The results emphasize distinct grain size trends from these two examples, as well as differences in the continuity and spatial distribution of mudstone drapes, which act as both baffles and barriers to fluid flow.

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.

The discovery and significance of a sedimentary hiatus within the Carboniferous Taiyuan Formation, northeastern Ordos Basin, China: Reply

We thank Zheng et al. (2016) for their comments on our previous work of sedimentary hiatus within the Carboniferous Taiyuan Formation, northeastern Ordos Basin, China (Jiang et al., 2012). Zheng et al. (2016) have different opinions on sedimentary facies and sequence stratigraphy interpretation in the study area. They question our interpretation based on their understanding of sedimentary facies, seismic geometry, orientation of sand body, and sand body thickness. Here, we provide additional evidence to reinforce our interpretation. The structure of this reply follows the order of the questions raised by Zheng et al. (2016). The interpretation of depositional environment for sand bodies in the Upper Pennsylvanian Taiyuan Formation (Ct2) has been controversial for decades. Some previous studies suggested that Ct2 represents a barrier–lagoon–tidal flat system (e.g., Hao et al., 2007; Wang et al., 2007). Zheng et al. (2016) also made such an interpretation. However, northeast–southwest-trending sand bodies in Ct2 were interpreted as fluvial–deltaic channels by many other studies (e.g., Li et al., 1995; Liu, 1998; Fu et al., 2003; Guo et al., 2009; Zhang et al., 2009; Luo et al., 2011). The braided stream fills of the incised valley were documented by extensive erosional surfaces, conglomerate and/or mud clast fluvial lag deposits, and trough cross bedding. Erosional surfaces are one of the most common features observed in cores of Ct2 interval (Figure 1; see also figure 4 in Jiang et al., 2012). The poorly sorted gravels are aligned in various directions, indicating a rapid deposit without significant tidal reworking (Figure 1E). In contrast, the sedimentary structures that Zheng et al. (2016) interpreted as tidal–barrier island signatures, such as mud drapes and cross bedding, can be also found in fluvial deposits. Figure 1. Sedimentary features of fluvial deposit in the …

The link between tectonics and sedimentation in back-arc basins: New genetic constraints from the analysis of the Pannonian Basin

The architecture of sedimentary basins reflects the relationship between accommodation space and sediment supply, their rates and localization being variable during basin evolution. The mechanisms driving the interplay between tectonics and sedimentation in extensional back-arc basins overlying rheological weak zones inherited from an earlier orogenic evolution are less understood. A typical example is the Pannonian back-arc basin of Central Europe. It is floored by continental lithosphere and was affected by large amounts of extension driven by the subduction rollback that took place in the Carpathians and/or Dinarides. A novel kinematic and seismic sequence stratigraphic interpretation calibrated by wells allows the quantification of the link between the formation of half grabens and coeval sedimentation in the Great Hungarian Plain part of the basin. While the lower order tectonic-induced cycles characterize the main phases of extension in various subbasins, the higher-order cyclicity and associated unconformities define individual moments of fault (re)activation. Our novel interpretation of a temporal and spatial migration of extension during Miocene times explains the contrasting present-day strike of various subbasins as a result of their gradual clockwise rotation. Incorporating the observed asymmetry, in particular the associated footwall exhumation, infers that the amount of extension is much larger than previously thought. The quantitative link between tectonics and sedimentation has allowed the definition of a novel model of sedimentation in asymmetric basins that can be ported to other natural scenarios of similarly hyperextended back-arc basins observed elsewhere.

Sequence development, depositional filling evolution, and prospect forecast in northern Aryskum Depression of South Turgay Basin, Kazakstan

Jurassic to Cretaceous clastic rocks of the South Turgay Basin were deposited in the typical Mesozoic rift basin formed during the late Triassic collision between the Kazakstan and Siberia plates. In this study, we used more than 140 wells and 2400 km2 of 3D seismic data in the northern Aryskum Depression to produce a detailed sequence stratigraphic interpretation of the South Turgay Basin. Guided by sequence stratigraphy, sedimentology, and structural geology, lower Jurassic-lower Cretaceous strata of the northern Aryskum Depression in the South Turgay Basin, Kazakhstan were subdivided into 10 third-order sequences based on geological and geophysical data. Combined with tectonic evolution characteristics, sequence developments in the basin can be divided into four stages: early rift stage (SQ1–SQ3), late rift stage (SQ4–SQ6), fault to depression transition stage (SQ7–SQ8), and depression stage (SQ9–SQ10). Through comprehensive analysis of seismic sequence configuration, sequence stacking pattern, and depositional filling characteristics, we established the depositional model of the Aryskum Depression in the South Turgay Basin. It is indicated that there are differences in depositional compositions of sequences formed in different stages. Four stages can be clearly identified: filling stage of fan delta facies–lacustrine facies (Stage I) corresponding to the rapid filling in the early rift stage, filling stage of fan delta facies–lacustrine facies–normal delta facies (Stage II) corresponding to trichotomous characteristics of internal systems tracts in the late rift stage, filling stage of braided river delta facies–normal delta facies–lacustrine facies (Stage III) corresponding to the development of high-stand systems tracts in the fault to depression transition stage, and filling stage of fluvial facies–normal delta facies–lacustrine facies (Stage IV) corresponding to binary characteristics of internal systems tracts in the depression stage. Finally, optimization of favorable exploration strata and prospects in the Aryskum Depression are proposed.

New insight of sedimentological and geochemical characterization of siliciclastic-carbonate deposits (Alveolina Limestone Formation, Graus-Tremp basin, Spain)

Abstract This article is a first attempt of combining sedimentological analysis and geochemical systematics of the Alveolina Limestone Formation as a tool to identify the major stratigraphic surfaces, and to improve the sequence stratigraphy interpretation. This formation is Early Eocene in age and crops out in several well-exposed cliffs in the Serraduy – Roda de Isabena area (Graus-Tremp basin, NE Spain). Within this succession, nineteen carbonate and siliciclastic facies have been identified and grouped in environmental facies associations (based on their vertical stacking and lateral relationships): 1) coastal plain; 2) clastic deltaic complex; 3) shallow carbonate inner-ramp; 4) mid-ramp; 5) outer-ramp; 6) reefal facies. The depositional architectures studied in the Serraduy area can be directly assessed on the field, and a 3D reconstruction is proposed. This enables us to build a synthetic depositional model and to identify five small-scale T/R cycles, bounded by different kinds of sedimentary discontinuities : angular unconformity, firmground, erosional surface… In parallel, geochemical analyses (C and O isotopes, major, minor and trace elements) were carried out to help at hierarchizing the cycles and the boundaries previously identified. Four of them may be considered as major stratigraphic surfaces, corresponding either to regional-scale angular unconformities, or to exposure surfaces. The latter are characterized by a selective dissolution, a slight but sharp decrease in δ13CV-PDB and in Mg, Fe and Sr contents below the surface. The absence of typical sedimentary criteria of exposure (with the exception of these geochemical signatures) may be explained by short-term exposure, an arid to semi-arid climate, and a dominant low-magnesian calcite original mineralogy, precluding the development and the preservation of widespread vadose diagenetic products. A new sequence stratigraphy model for the Alveolina Limestone Fm is finally proposed and discussed.

Towards a sequence stratigraphic solution set for autogenic processes and allogenic controls: Upper Cretaceous strata, Book Cliffs, Utah, USA

Upper Cretaceous strata exposed in the Book Cliffs of east–central Utah are widely used as an archetype for the sequence stratigraphy of marginal-marine and shallow-marine deposits. Their stratal architectures are classically interpreted in terms of accommodation controls that were external to the sediment routing system (allogenic), and that forced the formation of flooding surfaces, sequence boundaries, and parasequence and parasequence-set stacking patterns. Processes internal to the sediment routing system (autogenic) and allogenic sediment supply controls provide alternatives that can plausibly explain aspects of the stratal architecture, including the following: (1) switching of wave-dominated delta lobes, expressed by the internal architecture of parasequences; (2) river avulsion, expressed by the internal architecture of multistorey fluvial sandbodies and related deposits; (3) avulsion-generated clustering of fluvial sandbodies in delta plain strata; (4) ‘autoretreat’ owing to increasing sediment storage on the delta plain as it lengthened during progradation, expressed by progradational-to-aggradational stacking of parasequences; (5) sediment supply control on the stacking of, and sediment grain-size fractionation within, parasequence sets. The various potential allogenic controls and autogenic processes are combined to form a sequence stratigraphic solution set. This approach avoids anchoring of sequence stratigraphic interpretations on a specific control and acknowledges the non-unique origin of stratal architectures.

The use of chemostratigraphy to refine ambiguous sequence stratigraphic correlations in marine mudrocks. An example from the Woodford Shale, Oklahoma, USA

Application of sequence stratigraphy to fine-grained lithologies has previously been hindered by the difficulty of identifying distinct facies shifts within mudrocks. Three cores from Lincoln, Pottawatomie and Pontotoc Counties in Oklahoma and two outcrops at the Hunton Anticline Quarry in Murray County, OK record both proximal and distal regions of the Arkoma Basin. Handheld X-ray fluorescence data and gamma-ray profiles together with lithological descriptions can be used to develop sequence-stratigraphic interpretations. Stratigraphic successions that are challenging to correlate based on gamma-ray (GR) profiles alone can be correlated accurately by utilizing surfaces that are recognized within chemostratigraphic profiles. Within the Arkoma Basin, Oklahoma, the chemostratigraphic profile of the Woodford Shale is interpreted within a sequence-stratigraphic framework using the following general criteria. The Lowstand Systems Tract (LST) is defined by increasing concentrations of Ti, Zr, Al and K as well as high levels of Mo and V. The Transgressive Systems Tract (TST) is defined by declining concentrations of Ti and Zr, although Al and K may remain elevated; Mo and V also show general declines. The Highstand Systems Tract (HST) is defined by increasing concentrations of Ti, Zr, Al and K, but is distinguished from the LST by low levels of Mo and V. Supplementary material: Chemofacies profiles are available at http://doi.org/10.6084/m9.figshare.c.2849599 .

Structures and sequence stratigraphy of the Miocene successions, southwestern Gulf of Suez, Egypt

The subsurface structural evolution, facies changes and sequence stratigraphic interpretations of the Miocene successions of the southwestern part of the Gulf of Suez, Egypt, were studied by seismic reflection data of Twenty seven 3D seismic sections supported by the composite, velocity and vertical seismic profiles (VSP) logs of eight wells. Among them five sections and two geoseismic cross sections were selected to reveal the structural framework and depositional history of the study area. The analysis of depth-structure contour maps revealed that the Miocene strata are dissected by two major faults trends: The NW–SE trending faults (Clysmic trend) and the NE–SW trending cross faults running nearly perpendicular to the Clysmic faults. The facies changes of the syn-depositional Miocene units are controlled by the structural framework of the southern part of the Gulf of Suez being evolving diapiric structure of South Gharib Formation. The Miocene units are subdivided into two major 3rd order depositional sequences: S1 and S2.

New insights into the petroleum prospectivity of the Browse Basin: the results of a multi-disciplinary study

The Browse Basin hosts large gas accumulations, some of which are being developed for conventional liquefied natural gas (LNG). Extensive appraisal drilling has been focused in the central Caswell Sub-basin at Ichthys and Prelude, and along the extended Brecknock-Scott Reef Trend; whereas elsewhere the basin remains underexplored. To provide a better understanding of regional hydrocarbon prospectivity, the sequence stratigraphy of the Cretaceous succession and structural framework were analysed to determine the spatial relationship of reservoir and seal pairs, and those areas of enhanced source rock development. The sequence stratigraphic interpretation is based upon a common North West Shelf stratigraphic framework that has been developed in conjunction with industry, and aligned with the international time scale. Sixty key wells and 2D and 3D seismic data have been interpreted to produce palaeogeographic maps and depositional models for the Cretaceous succession. Geochemical analyses have characterised the molecular and stable isotopic signatures of fluids and correlated them with potential source rocks. The resultant petroleum systems model provides a more detailed understanding of source rock maturity, organic richness and hydrocarbon-generation potential in the basin. The model reveals that many accumulations have a complex charge history, with the mixing of hydrocarbon fluids from multiple Mesozoic source rocks, including the Lower–Middle Jurassic J10–J20 supersequences (Plover Formation), Upper Jurassic–Lowermost Cretaceous J30–K10 supersequences (Vulcan Formation), and Lower Cretaceous K20–K30 supersequences (Echuca Shoals Formation). Burial history and hydrocarbon expulsion models, applied to these Jurassic and Cretaceous supersequences, suggest that numerous petroleum systems are effective within the basin. For example, hydrocarbons are interpreted to have been generated from several source pods within the southern Caswell Sub-basin with migration continuing onto the Yampi Shelf, an area of renewed exploration interest.

Mississippian (Early Carboniferous) sequence stratigraphy of the Rhenish Kulm Basin, Germany

1. IntroductionThe relation between sea-level variations and sedimentary sequences that are bound by erosional unconformities was already elucidated by Sloss et al. (1949) and Sloss (1963) concerning the cratonic sequences of the conterminous U.S. (see also Sloss, 1988). However, only introduction of sequence stratigraphy on a seismic scale (Vail et al., 1977) caused a revolution of stratigraphic studies (Van Wagoner et al., 1987, 1989; Vail et al., 1991). It was a major step to understand the lateral genetic relationships of rock units in platform‑slope‑basin transects as well as their vertical genetic superposition, both based on the unifying aspect of relative sea-level changes. In the meantime, a plethora of studies is available from all kinds of sedimentary lithotypes throughout geological times, ranging from the sequence stratigraphic interpretation of single sections to seismic scale basins. However, most studies are devoted to shallow-marine platform settings. Sequence stratigraphic approaches to continental and basinal settings are underrepresented, and for the latter are almost completely confined to siliciclastic turbidite fan systems. Case studies and principles for deeper marine settings were reviewed by Catuneanu (2006) and Catuneanu et al. (2009, 2011), but miss an example of a complex deeper water foreland basin with differentiated lithosomes, as seen in the European and Northwest African Kulm basins.Herein, the sequence stratigraphic development of the Missis

Geomorphology and seismic stratigraphy of the early Cretaceous delta in the Vlaming Sub-basin and implications for seal quality

The early Cretaceous South Perth Shale has been previously identified as the regional seal in the offshore Vlaming Sub-basin. The South Perth Shale is a deltaic succession, which infilled a large palaeotopographic low in the Early Cretaceous through a series of transgressive and regressive events. A study undertaken at Geoscience Australia has shown that the seal quality varies greatly throughout the basin and in places has very poor sealing properties. A re-evaluation of the regional seal based on seismic mapping determined the extent of the pro-delta shale facies within the South Perth Shale succession, which provides effective sealing capacity. New sequence stratigraphic interpretation, seismic facies mapping, new and revised biostratigraphic data and well log analysis were used to produce palaeogeographic reconstructions which document the distribution of depositional facies within the South Perth Shale and reveal the evolution of the early Cretaceous deltas. Our study documents spatial variations in the seal quality and re-defines the extent and thickness of the regional seal in the offshore central Vlaming Sub-basin. It provides an explanation for the lack of exploration success at some structural closures and defines constraints on the possible location of valid plays.

Sediment Transport Model For the Eocene Escanilla Sediment-Routing System: Implications For the Uniqueness of Sequence Stratigraphic Architectures

Abstract Stratigraphic architectures are fundamentally controlled by the interplay at different temporal and spatial scales of accommodation and sediment supply, modulated by autogenic responses of the sediment routing system and its constituent segments. The flux and caliber of sediment supply is a function of climate, catchment area, and tectonics in the source regions, and unraveling these forcing mechanisms from the observed stratigraphic architecture remains a key research challenge. The mid-to-late Eocene Escanilla sediment routing system had its source regions in the south-central Pyrenean orogen, northern Spain, and transported sediment from wedge-top basins along tectonic strike to marine depocenters. By constructing a volumetric budget of the sedimentary system, it has been demonstrated that there were marked changes in the grain-size distribution released from the sediment sources and also in the position of the gravel front, across three ∼ 2.6 Myr time intervals from 41.6 to 33.9 Ma. Classical sequence stratigraphic interpretations would relate the movement of depositional boundaries such as the gravel front to changes of base level, either in isolation or in combination with sediment supply. Herein, we explore the possibility that the position of the gravel front was primarily driven by variability of grain-size distributions released from the source regions as a result of changes in catchment uplift rate and/or surface run-off. Using a simple model of sediment transport that captures first-order processes, we simulate the lateral movement of gravel deposition in the proximal part of the Escanilla sediment-routing system. Movement of the gravel front is a function of both accommodation generation and the transport capacity of the sediment routing system. We assume that the transport capacity is a linear function of the local slope and the water flux. By assuming that the observed thickness of deposits is equivalent to the accommodation available during deposition, we then use the stratigraphic architecture to constrain the change in catchment size and water flux over the three time intervals of the Escanilla paleo–sediment-routing system. Multiple scenarios are investigated in order to find the most plausible tectonic and climatic history. Model results indicate that during the mid-Eocene there was an increase in catchment length and sediment flux, most likely driven by tectonic uplift in the Pyrenean orogen. Subsequent marked progradation of the gravel front during the late Eocene was the consequence of reduced transport capacity due to a reduction in surface run-off. The latter model result is in agreement with records of pollen taxa that indicate increased climatic aridity in the late Eocene. The combination of a sediment transport model with a full sediment budget makes it possible to test the non-uniqueness of these results.