SEQUENCE STRATIGRAPHIC INTERPRETATION OF CARBONATE WIRELINE LOG MOTIFS: AN EXAMPLE FROM THE NORTH WEST SHELF OF AUSTRALIA

1998 ◽  
Vol 38 (1) ◽  
pp. 188 ◽  
Author(s):  
J.N.F. Hull ◽  
S.A. Smith ◽  
H.C. Young
Keyword(s):  
Sharp Increase ◽  
Passive Margin ◽  
Log Analysis ◽  
North West ◽  
Sequence Stratigraphic ◽  
Carbonate Sedimentation ◽  
The North ◽  
Wireline Logs ◽  
Definition Of ◽  
Sequence Boundaries

An integrated biostratigraphic, wireline and seismic sequence stratigraphic study has been conducted to constrain the timing and evolution of Late Cretaceous to Tertiary depocentres along the North West Shelf of Australia. During this study a model for the sequence stratigraphic interpretation of wireline logs in this carbonate-dominated regime has been developed.A series of readily identifiable, lowstand clastic deposits interspersed within the predominantly carbonate passive margin section of the North West Shelf provide well-defined correctable events with which to divide the section. Biostratigraphic data have indicated the presence of missing section at the base of these clastic deposits and their shelfal equivalents. These events have been correlated to define sequence boundaries that are represented on wireline log data by a sharp increase in the gamma signature. Lowstand systems tracts exhibit an irregular sonic and upwardly increasing gamma signature. Transgressive systems tracts show characteristically upward-decreasing gamma and sonic profiles. Maximum flooding surfaces have been identified as the point of cleanest carbonate sedimentation represented by gamma minima on wireline logs. Log motifs exhibiting little character have been interpreted as highstand systems tracts. On seismic these sequence stratigraphic events are represented by stratal geometries that would be expected for these systems tracts.The model has enabled the definition of a higher resolution chronostratigraphic framework for the Mid Cretaceous to Recent section of the North West Shelf than has previously been possible. Forty basin-wide events have been identified from the biostratigraphic and wireline log analysis, thirty of which can be tied throughout the Barrow, Dampier and Roebuck basins.

THE MIDDLE CRETACEOUS TO RECENT SEQUENCE STRATIGRAPHIC EVOLUTION OF THE EXMOUTH-BARROW MARGIN, WESTERN AUSTRALIA

2001 ◽  
Vol 41 (1) ◽  
pp. 381 ◽  
Author(s):  
H.C. Young ◽  
N.M. Lemon ◽  
J.N.F Hull
Keyword(s):  
Passive Margin ◽  
Outer Shelf ◽  
Early Miocene ◽  
Early Pliocene ◽  
North West ◽  
Sequence Stratigraphic ◽  
The North ◽  
Stratigraphic Model ◽  
Sequence Boundaries ◽  
Stratigraphic Evolution

Five supersequences have been revealed by a regional sequence stratigraphic study conducted in the Albian (109 Ma) to Recent section of the Exmouth-Barrow passive margin. The interpretation utilises a new sequence stratigraphic model developed for mixed siliciclasticcarbonate lithofacies. A high degree of resolution is brought to the study by identification of 37 regional sequence boundaries controlled by biostratigraphic, wireline and seismic data. Ditch cutting analysis, integrated into the new chronostratigraphic framework, provided detailed lithofacies maps.The five supersequences, named the Gallic, Senonian, Palaeogene, Middle Neogene and Pliocene, are based upon regional lowstand, transgressive and highstand phases. The Gallic Supersequence (late Tithonian–latest Cenomanian) represents a marine incursion of siliciclastic sediments coincident with the rifting and accelerated movement of India away from Australia. A Senonian Supersequence (latest Cenomanian–middle Maastrichtian) truncates the previous supersequence with incised canyons developed on the outer shelf. The evolution of the Senonian section corresponds to the Australian separation from Antarctica and the first appearance of carbonates.The Palaeogene Supersequence (middle Maastrichtian– late Early Miocene) dominates much of the Tertiary and is identified by a basinward shift of facies following a Maastrichtian–Paleocene sea level fall. Enhanced subsidence on the outer shelf during the Eocene created a forced transgression with carbonate mudstonesiltstone deposition. A highstand during the Oligocene– Early Miocene formed the distinctive prograding carbonate shelf recognised throughout the North West Shelf.A Middle Neogene Supersequence (late Early Miocene– Early Pliocene) is identified by an erosive base and the development of a thin lowstand fan on the outer shelf. The supersequence is largely characterised by backstepping reefs following a Middle Miocene transgression. A Late Miocene eustatic stillstand restricted reef development to the inner shelf, generating coarsegrained carbonate progrades from highstand-shedding. The final Pliocene Supersequence (Pliocene–Recent) was initiated by a eustatic fall during the Early Pliocene and was followed by the development of a transgressive, aggrading shelf.

Definition of tectono-sedimentary elements for rifted continental margins of the Norwegian and Greenland seas

2021 ◽  
pp. M57-2021-31
Author(s):  
Harald Brekke ◽  
Halvor S. S. Bunkholt ◽  
Jan I. Faleide ◽  
Michael B. W. Fyhn
Keyword(s):  
Lower Jurassic ◽  
Passive Margin ◽  
Continental Margins ◽  
Axial Line ◽  
Continental Breakup ◽  
The North ◽  
Tectonic Development ◽  
Definition Of ◽  
Conjugate Margins ◽  
Greenland Margin

AbstractThe geology of the conjugate continental margins of the Norwegian and Greenland Seas reflects 400 Ma of post-Caledonian continental rifting, continental breakup between early Eocene and Miocene times, and subsequent passive margin conditions accompanying seafloor spreading. During Devonian-Carboniferous time, rifting and continental deposition prevailed, but from the mid-Carboniferous, rifting decreased and marine deposition commenced in the north culminating in a Late Permian open seaway as rifting resumed. The seaway became partly filled by Triassic and Lower Jurassic sediments causing mixed marine/non-marine deposition. A permanent, open seaway established by the end of the Early Jurassic and was followed by the development of an axial line of deep marine Cretaceous basins. The final, strong rift pulse of continental breakup occurred along a line oblique to the axis of these basins. The Jan Mayen Micro-Continent formed by resumed rifting in a part of the East Greenland margin in Eocene to Miocene times. This complex tectonic development is reflected in the sedimentary record in the two conjugate margins, which clearly shows their common pre-breakup geological development. The strong correlation between the two present margins is the basis for defining seven tectono-sedimentary elements (TSE) and establishing eight composite tectono-sedimentary elements (CTSE) in the region.

Stratigraphy of the Birdrong: an integrated approach

2012 ◽  
Vol 52 (2) ◽  
pp. 684
Author(s):  
Jessica Trainor ◽  
Jeffery Goodall ◽  
Kathryn Amos
Keyword(s):  
Integrated Approach ◽  
Predictive Tool ◽  
Palynological Analysis ◽  
North West ◽  
The North ◽  
Study Interval ◽  
Depositional Systems ◽  
Northern Carnarvon Basin ◽  
Facies Modelling ◽  
Sequence Boundaries

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.

scholarly journals The Hell Creek Formation, Montana: A Stratigraphic Review and Revision Based on a Sequence Stratigraphic Approach

Geosciences ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 435
Author(s):  
Denver Fowler
Keyword(s):  
South Dakota ◽  
Lake Area ◽  
Sequence Stratigraphic ◽  
Hell Creek Formation ◽  
Accommodation Space ◽  
The North ◽  
Marine Influence ◽  
Sequence Boundaries ◽  
North And South ◽  
Upper Maastrichtian

The Upper Maastrichtian fluvial Hell Creek Formation of the Fort Peck Lake area, Montana (and regional equivalents) is notable for its vertebrate fossils and for the K-Pg mass extinction at or near its upper contact. Despite intense study, internal stratigraphy of the Hell Creek Formation is still poorly constrained, hindering study. This work reviews the stratigraphy of the Hell Creek Formation, as currently understood, and proposes important revisions to the recently proposed type section, particularly concerning complexity of the Hell Creek Formation basal contact. This work also subdivides the Montanan Hell Creek Formation into four 4th order depositional sequences, superimposed over a 3rd order marine transgression. Sequence boundaries are defined by four, laterally continuous disconformities formed by pauses in the creation of accommodation space, marked by overlying amalgamated channel complexes, or less commonly, correlative interfluve paleosols. Cyclicity in Montana may be correlative with similar 4th order cyclicity and marine influence documented in North and South Dakota, Alberta, and Saskatchewan. Magnetostratigraphy and new biostratigraphic data support correlation of the upper Montanan sequence with the North Dakotan Cantapeta tongue (and overlying fines) and Canadian Scollard and Frenchman Formations.

GEOLOGICAL FRAMEWORK OF THE GREAT AUSTRALIAN BIGHT

1969 ◽  
Vol 9 (1) ◽  
pp. 60
Author(s):  
R. Smith ◽  
P. Kamerling
Keyword(s):  
Middle Eocene ◽  
Early Stage ◽  
Upper Jurassic ◽  
The South ◽  
The West ◽  
Offshore Area ◽  
North West ◽  
Carbonate Sedimentation ◽  
The North ◽  
Great Australian Bight

Geophysical exploration carried out in the Great Australian Bight since 1966, combined with geological fieldwork in the adjacent land areas, has made it possible to outline the broad geological framework of the area.The "basement" consists of two major units, an offshore extension of the locally metamorphic Cambrian Kanmantoo Group in the south-east and the extension of the West Australian Archaean shield in the north-west. The boundary is thought to follow a trend extending westerly from the Cygnet-Snelling fault zone on Kangaroo Island.In two areas the basement has been downfaulted, thus creating depositional areas for thick sequences of sediments, namely the Elliston trough to the west of Eyre Peninsula and the Duntroon basin, south of Eyre Peninsula and west of Kangaroo Island.The geological setting of the Duntroon basin appears to be comparable with the Otway basin and a Jurassic- Cretaceous age is assumed for the folded sequence of sediments overlying the basement and underlying the Tertiary with angular unconformity. The basin was possibly partially and temporarily closed to the south and open to marine influences from the west.In the Elliston trough the lower part of the section which has low to medium velocity seismic character, is probably Mesozoic, as is evidenced by the Upper Jurassic encountered in its onshore extension. Proterozoic-Cambrian sediments may overlie the basement in the eastern part of the trough. Deformation of the Mesozoic is limited to the mouth of the trough where there is indication of a base- Tertiary unconformity. This trough was probably also open to marine influences to the west.Along the continental margin between the basins and also south of the Eucla basin a thin Mesozoic section, conformably underlying the Tertiary, is probably present, gradually thickening towards the continental slope.In the onshore area Tertiary sedimentation started with local deposition of clastics during the Middle Eocene, which also may have been the case off the Eucla basin, in the Elliston trough and in the Duntroon basin. Carbonate sedimentation took place from the Middle-Upper Eocene onwards, to reach its widest areal extent during the Lower Miocene. A hiatus during the Oligocene may have occurred in the western part of the Bight as is the case in the Eucla basin.Only weak deformation of the Tertiary in the offshore area has been observed. This generally occurs over Mesozoic structures in the Duntroon basin and as draping over topographic basement highs at the mouth of the Elliston trough.No significant hydrocarbon indications are known from the surrounding land areas, but the well-documented bitumen strandings along the coast point to offshore seepages indicating generation of hydrocarbons in the general area.At this stage prospects must be regarded as speculative.although a folded probable Mesozoic sequence forms an objective in the Duntroon basin while prospective Mesozoic-Tertiary section appears to be present in the Elliston trough, where structural evaluation is still at a relatively early stage.

Neoproterozoic slope deposits, Mackenzie Mountains, northwestern Canada: implications for passive-margin development and Ediacaran faunal ecology

2000 ◽  
Vol 37 (7) ◽  
pp. 997-1020 ◽  
Author(s):  
Robert B MacNaughton ◽  
Guy M Narbonne ◽  
Robert W Dalrymple
Keyword(s):  
Thermal Relaxation ◽  
Passive Margin ◽  
Sequence Stratigraphic ◽  
Facies Associations ◽  
Windermere Supergroup ◽  
Sea Level Oscillations ◽  
Relative Inability ◽  
Sequence Boundaries ◽  
Major Sequence ◽  
Water Facies

The youngest formations of the Neoproterozoic Windermere Supergroup in northwestern Canada (Gametrail, Blueflower, and Risky formations) record the transition from slope to shelf deposition on a prograding passive margin. Eleven facies associations are recognized, representing environments ranging from carbonate- and siliciclastic-dominated continental slope to open carbonate shelf and siliciclastic shoreface. Seven simple sequences are recognized, which can be grouped into three composite sequences. Combination of the data presented here with previous work on underlying and overlying formations indicates that the sequence-stratigraphic record is least detailed in the deepest-water facies and most detailed in shelf facies, reflecting the relative inability of high-frequency relative sea-level oscillations to affect deposition in deep-water settings. Falling-stage deposits are especially common in the upper slope region. Several major sequence boundaries (unconformities) are clustered in the interval a short distance below the Precambrian-Cambrian boundary. The most significant of these occurs high in the Blueflower Formation, not at the top of the Risky Formation as commonly inferred. This interval containing several surfaces may reflect thermal uplift related to the rifting recorded in rocks of this age in the southern Canadian Cordillera. Renewed subsidence (thermal relaxation) commenced just prior to the Neoproterozoic-Cambrian boundary, giving rise to a thick succession of shelf to nonmarine basal-Cambrian deposits. Ediacaran body fossils previously reported from the studied units occur in a range of slope to shoreface environments, including some facies that were deposited below the photic zone. The most common taxa occur across a spectrum of facies and were apparently ecological generalists.

New sequence stratigraphic framework on a ‘passive’ margin: Implications for post-breakup depositional environment and onset of glaciomarine conditions in Northeast Greenland

2020 ◽  
pp. jgs2020-128
Author(s):  
Thomas G. Petersen
Keyword(s):  
Late Eocene ◽  
Passive Margin ◽  
Tectonic Activity ◽  
Sequence Stratigraphic ◽  
Submarine Fans ◽  
The North ◽  
Tectonic Forces ◽  
Stratigraphic Evolution ◽  
Erosional Event ◽  
The Impact

Detailed sequence stratigraphic frameworks have been produced for most of the Cenozoic deposits around the North Atlantic and Greenland Sea. However, the sequence stratigraphic evolution of the Northeast Greenland shelf, a significant part of the Atlantic Ocean margin, has so far never been interpreted. This study provides for the first time, a detailed sequence stratigraphic interpretation of the Northeast Greenland shelf since the late Eocene. Tectonic evolution, eustatic sea level change and the impact of glaciations are integrated into a consistent geological history. Based on the identification of pronounced unconformities and their correlative conformities, 10 stratigraphic sequences are identified. The onset of deposition is defined by a pronounced erosional event, where late Palaeocene tectonic activity caused mass wasting of the uplifted footwall of the Danmarkshavn Ridge along ca. 200 km section of the ridge. During the mid Miocene, a second pronounced unconformity developed across the margin, which caused forced regressive submarine fans to prograde across the margin. The following tectonic quiet period is overlain by glaciomarine deposits, with evidence of ice deformation reaching the present day shelf break. Finally, unknown superregional plate tectonic forces are suggested as a driver of sequence formation based on correlation with the Canadian Arctic.

scholarly journals Young Adult Perceptions of Internet Communications and the Grooming Concept

SAGE Open ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 215824402091457
Author(s):  
Amy C. Wood ◽  
Jacqueline M. Wheatcroft
Keyword(s):  
Young Adults ◽  
Young People ◽  
Vulnerable Groups ◽  
Youth Organizations ◽  
Structured Interviews ◽  
North West ◽  
Young Males ◽  
Perceptions Of Risk ◽  
The North ◽  
Definition Of

Research of young people shows a lack of understanding of the term grooming in online communications and that internet risks are taken because internet literacy is poor for this group. However, limited research has investigated the perceptions of young adults in this context. The aim of this study was to understand young adults’ perceptions of risk, their internet behaviors, and understanding of the grooming concept. Furthermore, to understand the types of risk behaviors young people engage in online, whether they perceive these behaviors as risky, and what implications this has for vulnerability to negative experiences. An examination of internet communication perceptions and the grooming concept focused on 10 young males and females aged between 18 and 23 years. Semi-structured interviews were conducted at open access youth organizations in the North West of England, UK, and the duration of each interview was approximately 30 min. The data were transcribed and analyzed using thematic analysis. Emergent themes were (a) grooming as a concept, (b) virtual lives, and (c) perception of risk. The findings concur there is limited understanding of the term grooming but that explanations may not be simply confined to literacy. Risks being taken online were not always perceived as risky. Recommendations include the need for a more nuanced definition of the term grooming and that more information is available to children and caregivers. Further work should focus on younger participants’ perceptions of grooming to address wider issues, together with a focus on risk taking behaviors among other vulnerable groups.

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