MARGIN-SCALE, BASEMENT-INVOLVED COMPARTMENTALISATION OF AUSTRALIA'S NORTH WEST SHELF: A PRIMARY CONTROL ON BASIN-SCALE RIFT, DEPOSITION AL AND REACTIVATION HISTORIES

1999 ◽  
Vol 39 (1) ◽  
pp. 40 ◽  
Author(s):  
G.W. O'Brien ◽  
M. Morse ◽  
D. Wilson ◽  
P. Quaife ◽  
J. Colwell ◽  
...  
Keyword(s):  
Transition Zone ◽  
Fault Reactivation ◽  
Small Displacement ◽  
Driving Mechanism ◽  
Fracture System ◽  
Primary Control ◽  
North West ◽  
Seal Failure ◽  
Lithospheric Flexure ◽  
Basin Scale

Australia's North West Shelf is segmented into four discrete margin-scale compartments which have distinct rift and reactivation histories. Two of the margin segments, the Carnarvon and Bonaparte compartments, are very wide (500–600 km), marginal plateau systems, whereas the other two segments, the Canning and Browse compartments, are narrower and steeper. The boundaries between individual rift compartments appear to be controlled by Proterozoic fracture systems.The Browse-Bonaparte transition zone is a major, northwest-trending Proterozoic fracture system which has a series of igneous intrusions along its length. These intrusions are located where the fracture system is cut by younger, northeast-trending extensional faults. This transition zone is a margin-scale fault relay zone, with intense fault overlap along the transition resulting in the zone being a long-lived, syn-rift high. Moreover, the transition zones between adjacent wide and narrow margins are prime locations for the entry point of siliciclastics into the rift or post-rift margin system. As a result, well-developed channel systems often cut through these boundaries and high quality reservoirs (particularly low-stand fans) are developed.Neogene fault reactivation, associated with convergence of the Australasian and Eurasian plates, is evident along the North West Shelf. The style of this reactivation is, however, closely controlled by the margin- scale architecture. In the Browse and Carnarvon basins, Neogene inversion is common, but at the leading edge of the collisional system, the Bonaparte compartment, the fault style is exclusively extensional. It appears that lithospheric flexure, associated with localised foreland development (i.e. the Timor Trough), has been the driving mechanism for the extensional faulting within the Bonaparte compartment. Crustal convergence seems to have been accommodated completely by thrusting on the northwestern margin of Timor and by foreland formation. In contrast, the Browse and Carnarvon compartments lacked a 'buffering' foreland system and, being adjacent to rigid and thin oceanic crust which transmits stress well over long distances, the inversional stresses were transmitted directly into these compartments.As a result of these margin-scale processes, the Bonaparte compartment is characterised by a thin regional seal (often 100 ms) on Neogene extensional faults—a combination which strongly favours fault seal failure and trap breach. In contrast, the Browse compartment is characterised by thick seals and small displacement Neogene faults, and thus the probability of fault seal failure is much less.

scholarly journals Trends in coastal upwelling intensity during the late 20th century

Ocean Science ◽  
2010 ◽  
Vol 6 (3) ◽  
pp. 815-823 ◽  
Author(s):  
N. Narayan ◽  
A. Paul ◽  
S. Mulitza ◽  
M. Schulz
Keyword(s):  
20Th Century ◽  
Wind Stress ◽  
Coastal Upwelling ◽  
Meridional Wind ◽  
Steady Increase ◽  
Late 20Th Century ◽  
North West ◽  
Basin Scale ◽  
Upwelling Intensity ◽  
Instrumental Records

Abstract. This study presents linear trends of coastal upwelling intensity in the later part of the 20th century (1960–2001) employing various indices of upwelling, derived from meridional wind stress and sea surface temperature. The analysis was conducted in the four major coastal upwelling regions in the world, which are off North-West Africa, Lüderitz, California and Peru. The trends in meridional wind stress showed a steady increase of intensity from 1960–2001, which was also reflected in the SST index calculated for the same time period. The steady cooling observed in the instrumental records of SST off California substantiated this observation further. It was also noted that the trends in meridional wind stress obtained from different datasets differ substantially from each other. Correlation analysis showed that basin-scale oscillations like the Atlantic Multidecadal Oscillation (AMO) and the Pacific Decadal Oscillation (PDO) could not be directly linked to the observed increase of upwelling intensity off NW Africa and California respectively. The relationship of the North Atlantic Oscillation (NAO) with coastal upwelling off NW Africa turned out to be ambiguous due to a negative correlation between the NAO index and the meridional wind stress and a lack of correlation with the SST index. Our results give additional support to the hypothesis that the coastal upwelling intensity increases globally because of raising greenhouse gas concentrations in the atmosphere and an associated increase of the land-sea pressure gradient and meridional wind stress.

Three-dimensional geometry and growth of a basement-involved fault network developed during multiphase extension, Enderby Terrace, North West Shelf of Australia

2021 ◽  
Author(s):  
Hongdan Deng ◽  
Ken McClay
Keyword(s):  
Three Dimensional ◽  
Sedimentary Basins ◽  
Fault Reactivation ◽  
Late Triassic ◽  
Seismic Reflection Data ◽  
North West ◽  
Reflection Data ◽  
Data Volume ◽  
Vertical Linkages ◽  
Fault Network

<div>Basement fault reactivation, and the growth, interaction, and linkage with new fault segments are fundamentally three-dimensional and critical for understanding the evolution of fault network development in sedimentary basins. This paper analyses the evolution of a complex, basement-involved extensional fault network on the Enderby Terrace on the eastern margin of the Dampier sub-basin, NW Shelf of Australia. A high-resolution, depth-converted, 3D seismic reflection data volume is used to show that multiphase, oblique extensional reactivation of basement-involved faults controlled the development of the fault network in the overlying strata. Oblique reactivation of the pre-existing faults initially led to the formation of overlying, en échelon Late Triassic – Middle Jurassic fault segments that, as WNW–directed rifting progressed on the margin, linked by breaching of relay ramp to form two intersecting fault systems (F1 and F2-F4). Further reactivation in the Latest Jurassic – Early Cretaceous (NNW–SSE extension) produced an additional set of en échelon fault arrays in the cover strata. The final fault network consists of main or principal faults and subordinate or splay faults, together with branch lines that link the various components. Our study shows that breaching of relay ramps and/or vertical linkages produces vertical and horizontal branch lines giving complex final fault geometries. We find that repeated activity of the basement-involved faults tends to form continuous and planar fault architectures that favor displacement transfer between the main constituent segments along strike and with depth.</div>

Structural style of the White Pointer and Hammerhead Delta—deepwater fold-thrust belts, Bight Basin, Australia

2010 ◽  
Vol 50 (1) ◽  
pp. 487 ◽  
Author(s):  
Justin MacDonald ◽  
Rosalind King ◽  
Richard Hillis ◽  
Guillaume Backé
Keyword(s):  
Supercritical Co2 ◽  
Large Scale ◽  
Qualitative Evaluation ◽  
Seal Failure ◽  
Structural Style ◽  
Thrust Belts ◽  
Strong Positive Relationship ◽  
Basin Scale ◽  
Gas Chimneys ◽  
Gippsland Basin

GeoScience Victoria and partners have undertaken the first detailed basin-wide study of the regional top seal in the Gippsland Basin. The Gippsland Basin is an attractive site for geological carbon storage (GCS) because of the close proximity to emission sources and the potential for large-scale storage projects. This top seal assessment involved the analysis of seal attributes (geometry, capacity and mineralogy) and empirical evidence for seal failure (soil gas geochemical anomalies, gas chimneys, hydrocarbon seepage and oil slicks). These datasets have been integrated to produce a qualitative evaluation of the containment potential for GCS, and also hydrocarbons, across the basin. Mineralogical analysis of the top seal has revealed that the Lakes Entrance Formation is principally a smectite-rich claystone. The geometry of the top seal is consistent with deposition in an early post-rift setting where marine sediments filled palaeo-topographic lows. The seal thickness and depth to seal base are greatest in the Central Deep and decrease toward the margins. There is a strong positive relationship between seal capacity column heights, seal thickness, depth to seal base and smectite content. At greater burial depths (below 700 m) and where smectite content is greater than 70%, seal capacity is increased (supportable column heights above 150 m). Natural hydrocarbon leakage and seepage onshore and offshore is correlated with fault distribution and areas of poor seal capacity. This study provides a framework for qualitatively evaluating seal potential at a basin scale. It has shown that the potential of the regional top seal over the Central Deep, Southern Terrace, central eastern Lake Wellington Depression and the southern to central near shore areas in the Seaspray Depression are most suitable for the containment of supercritical CO2. Further toward the margin of the regional seal in both onshore and offshore areas, containment of supercritical CO2 is less likely.

scholarly journals Trends in coastal upwelling intensity during the late 20th century

2010 ◽  
Vol 7 (1) ◽  
pp. 335-360 ◽  
Author(s):  
N. Narayan ◽  
A. Paul ◽  
S. Mulitza ◽  
M. Schulz
Keyword(s):  
20Th Century ◽  
Wind Stress ◽  
Coastal Upwelling ◽  
Meridional Wind ◽  
Steady Increase ◽  
Late 20Th Century ◽  
North West ◽  
Basin Scale ◽  
Upwelling Intensity ◽  
Instrumental Records

Abstract. This study presents linear trends of coastal upwelling intensity in the later part of the 20th century (1960–2001) employing various indices of upwelling, derived from meridional wind stress and sea surface temperature. The analysis was conducted in the four major coastal upwelling regions in the world, which are off North-West Africa, Lüderitz, California and Peru respectively. The trends in meridional wind stress showed a steady increase of intensity from 1960–2001, which was also reflected in the SST index calculated for the same time period. The steady cooling observed in the instrumental records of SST off California substantiated this observation further. Correlation analysis showed that basin-scale oscillations like the Atlantic Multidecadal Oscillation (AMO) and the Pacific Decadal Oscillation (PDO) could not be directly linked to the observed increase of upwelling intensity off NW Africa and California respectively. The relationship of the North Atlantic Oscillation (NAO) with coastal upwelling off NW Africa turned out to be ambiguous due to a negative correlation between the NAO index and the meridional wind stress and a lack of correlation with the SST index. Our results give additional support to the hypothesis that the coastal upwelling intensity increases globally because of raising greenhouse gas concentrations in the atmosphere and an associated increase of the land-sea pressure gradient and meridional wind stress.

scholarly journals Explanatory notes to the Geological map of Greenland, 1:500 000, Thule, Sheet 5

2006 ◽  
pp. 1-100 ◽  
Author(s):  
Peter R. Dawes
Keyword(s):  
Raw Materials ◽  
Late Quaternary ◽  
Regional Metamorphism ◽  
Fault Reactivation ◽  
Detrital Zircons ◽  
Dyke Swarm ◽  
Baffin Bay ◽  
West Greenland ◽  
North West ◽  
Geological Map

Abstract Dawes, P.R. 2006: Explanatory notes to the Geological map of Greenland, 1:500 000, Thule, Sheet 5. Geological Survey of Denmark and Greenland Map Series 2, 97 pp. + map These explanatory notes cover part of North-West Greenland defined by latitudes 75°15'N and 78°N and longitudes 57°W and 73°W, a region with appreciable ice cover. The bedrock is dominated by two Precambrian provinces that extend across Baffin Bay into Canada: the highgrade Archaean-Palaeoproterozoic shield overlain by the intracratonic Mesoproterozoic-?Neoproterozoic Thule Basin. Map units are systematically described and introductory sections cover the physical environment, logistics, data sources and geoscientific research. The crystalline shield embraces seven complexes: three of Archaean age, two of Archaean-?Palaeoproterozoic age and two of Palaeoproterozoic age. Isotopic ages of c. 2900 Ma indicate that Neoarchaean orthogneisses are present in part of the region while the existence of Mesoarchaean crust is indicated by c. 3200 Ma detrital zircons. The high-grade orthogneisses and paragneisses of the Thule mixed-gneiss complex were intruded by two plutonic suites, the Kap York meta-igneous complex at c. 2700 Ma and the Smithson Bjerge magmatic association that includes a major anorthosite body. Subsequent deformation, metamorphism and migmatisation led to the formation of gneisses recognised within the Melville Bugt orthogneiss complex . Palaeoproterozoic sedimentation and volcanism represented by the Prudhoe Land supracrustal complex took place after c . 2250 Ma but had ceased by c. 1985 Ma when the Prudhoe Land granulite complex was emplaced. Rocks within the Lauge Koch Kyst supracrustal complex may correlate with the Palaeoproterozoic Karrat Group of West Greenland. Polyphase deformation with isoclinal folding, and regional metamorphism up to granulite-facies grade, affected the region c. 1900 Ma ago, with cooling until c . 1650 Ma. Extensional faulting, intracratonic basin formation and periods of basaltic magmatism occurred during the last 1000 million years of Proterozoic time. After regional dyking at c . 1630 Ma ( Melville Bugt dyke swarm ) followed by mature peneplanation, the Thule Basin developed as an interior fracture and sag depocentre across the area that is now northernmost Baffin Bay. Defined by the unmetmorphosed Thule Supergroup at least 6 km thick, the basin records fluvial to shallow-marine sedimentation and tholeiitic volcanism at least 1270 million years old. The basin is dissected by the Thule half-graben system dominated by WNW-ESE-trending faults thought to have developed during the final tectono-magmatic period dated at c. 700650 Ma. Conspicuous products of this are a major sill complex ( Steensby Land sill complex ) and a regional dyke swarm that parallels the half-grabens ( Thule dyke swarm ). Fault reactivation is probably related to the late Phanerozoic tectonic evolution of Baffin Bay. In addition to the four metallic commodities included on the map - magnetite, copper, iron suphides, ilmenite - there is potential for gold and other mineralisations. The Neoarchaean magnetite province, traceable for over 400 km through the map region, is spatially the largest in Greenland and it is a correlative of the Mary River iron deposits of Baffin Island, Canada. Several raw materials have potential for local handicraft industries, including soapstone and agate. The region hosts a multi-event glacial and marine Middle-Late Quaternary stratigraphy dating back to at least the Saalian/Illinoian (pre-130 ka B.P.). The entire region was probably overriden by the Inland Ice during the Weichselian/Wisconsinian glacial maximum and deglaciated in the early Holocene, 11 000 to 9000 years ago.

scholarly journals COMPARAISON DES RESULTATS DE L’APPROCHE PAP/CAR ET LE MODELE USLE DANS LA CARTOGRAPHIE ET L’ESTIMATION QUALITATIVE DE L’EROSION HYDRIQUE DANS LE BASSIN VERSANT DE L’OUED AMLIL, (PRERIF - MAROC).

2021 ◽  
Author(s):  
Hili Aiman ◽  
Yahia El Khalki ◽  
Hanane Reddad ◽  
Jaouad Gartet ◽  
Mohamed Abahrour
Keyword(s):  
Action Plan ◽  
Water Erosion ◽  
Intense Rainfall ◽  
North West ◽  
North East ◽  
The North ◽  
Basin Scale ◽  
Natural Data ◽  
Bassin Versant ◽  
Very High

Este trabajo presenta los resultados de nuestro estudio sobre la cartografía y la estimación de la erosión del agua utilizando dos tipos de métodos. El primero es el del PAP/RAC 1998 que actúa en el marco del Plan de Acción para el Mediterráneo (PAM) del PNUMA, el segundo es el del modelo empírico de WISCHMEIER y SMITH 1978 (USLE).En la cuenca del Oued Amlil (153,7 km²) situada al noroeste de Taza (noreste de Marruecos) se dan todas las condiciones para que se desencadene y se acelere la erosión hídrica, las formaciones litológicas margosas blandas e impermeables (71,5%), una cobertura vegetal muy limitada (13,2%) y unas precipitaciones agresivas e intensas. El análisis de los datos naturales de la cuenca por el método PAP/CAR ha identificado cinco tipos principales de erosión (erosión muy alta 23%, erosión alta 48%, la clase de erosión significativa representa el 22%, 6% y 1% para las clases de erosión baja y muy baja respectivamente. Luego, las pérdidas de suelo fueron estimadas por el método USLE, los resultados obtenidos permiten identificar sectores a escala de cuenca donde las pérdidas tienen valores altos de 62.3% (alto riesgo entre 66 y 102 t/ha/año (34%), y muy altos (26.2%) entre 102 y 355.6 t/ha/año) This work presents the results of our study on mapping and estimating water erosion using two types of methods. The first is that of PAP/RAC 1998 acting within the framework of the UNEP Mediterranean Action Plan (MAP), the second is that of the empirical model of WISCHMEIER and SMITH 1978 (USLE). In the catchment area of the Oued Amlil (153.7 km²) located to the North-West of Taza (North-East Morocco), all the conditions for triggering and accelerating water erosion are present, soft and impermeable marl lithological formations (71.5%), very limited vegetation cover (13.2%), and aggressive and intense rainfall. The analysis of the natural data of the watershed by the PAP/CAR method has identified five main types of erosion (very high erosion 23%, high erosion 48%, notable erosion class represents 22%, 6% and 1% for low and very low erosion classes respectively. Then, soil losses were estimated by the USLE method, the results obtained allow the identification of sectors at the basin scale where the losses have high values 62.3% (high risk between 66 and 102 t/ha/year (34%), and very high (26.2%) between 102 and 355.6 t/ha/year). Le présent travail expose les résultats de notre étude concernant la cartographie et l’estimation de l’érosion hydrique selon deux types de méthodes. La première, est celle de PAP/CAR 1998 agisse dans le cadre du Plan d'action pour la Méditerranée (PAM) du PNUE, la seconde est celle du modèle empirique de WISCHMEIER et SMITH 1978 (USLE). Dans le bassin versant de l’Oued Amlil (153.7 km²) situé au Nord-Ouest de Taza (Nord-Est du Maroc), toutes les conditions de déclenchement et d’accélération de l’érosion hydrique sont présentent, des formations lithologiques marneuses tendres et imperméables (71.5%), un couvert végétal très limité (13.2%), et des précipitations agressives et intenses. L'analyse des données naturelles du bassin versant par la méthode de PAP/CAR a permis d’identifier cinq principaux types d’érosion (érosion très élevée 23%, 48% pour l’érosion élevée, la classe d’érosion notable représente 22%, 6% et 1% pour les classes d’érosion faibles et très faible respectivement. Ensuite, les pertes en sol ont été estimées par la méthode d’USLE, les résultats obtenus permettent l’identification des secteurs à l’échelle du bassin où les pertes connaissent des valeurs élevées 62.3% (risque forte entre 66 et 102 t/ha/an (34%), et très fort (26.2%) entre 102 et 355.6 t/ha/an).

REASSESSING POTENTIAL ORIGINS OF SYNTHETIC APERTURE RADAR (SAR) SLICKS FROM THE TIMOR SEA REGION OF THE NORTH WEST SHELF ON THE BASIS OF FIELD AND ANCILLARY DATA

2005 ◽  
Vol 45 (1) ◽  
pp. 311 ◽  
Author(s):  
A.T. Jones ◽  
G.A. Logan ◽  
J.M. Kennard ◽  
N. Rollet
Keyword(s):  
Synthetic Aperture Radar ◽  
Transition Zone ◽  
Environmental Data ◽  
Synthetic Aperture ◽  
Shelf Area ◽  
North West ◽  
The North ◽  
Timor Sea ◽  
Natural Hydrocarbon ◽  
Aperture Radar

The Timor Sea region of the North West Shelf is one of natural hydrocarbon accumulation and seepage, which has been investigated by integrated remote sensing studies in the past 10 years. One of the primary tools incorporated in these studies has been Synthetic Aperture Radar (SAR). During a recent Geoscience Australia marine survey to the Yampi Shelf area, active hydrocarbon seepage was directly observed in the form of gas plumes rising from the sea-floor. Active seepage was not observed in areas associated with dense clusters of elongated to irregularshaped features in the SAR data, which have previously been interpreted as natural hydrocarbon seepage slicks. These slicks, and another dense cluster of slicks across the Browse–Bonaparte Basin Transition Zone, are reassessed in the context of alternative formational processes.Mapping of bathymetric channels directly beneath the SAR slicks using multi-beam swath bathymetry and measurement of tidal currents using an acoustic doppler current profiler indicates that tidal current flows may have contributed to slick formation over the Yampi Shelf headland. In contrast, coral spawning may have contributed to the formation of annular to crescent-shaped SAR slicks associated with submerged reefs and shoals over the nearby transition zone. Subsequent to identifying potential alternative origins for these two types of SAR features, the remaining slicks across the area were re-categorised on the basis of their size and shape in the context of ancillary hydrographic and environmental data. An alternative nonseepage origin was established for most of the 381 SAR slicks previously identified as being related to natural hydrocarbon seepage. This may necessitate a significant downgrading of the extent and frequency of active hydrocarbon (particularly oil) seepage in the region.

Three-dimensional geometry and growth of a basement-involved fault network developed during multiphase extension, Enderby Terrace, North West Shelf of Australia

2021 ◽  
Author(s):  
Hongdan Deng ◽  
Ken McClay
Keyword(s):  
Three Dimensional ◽  
Sedimentary Basins ◽  
Fault Reactivation ◽  
Late Triassic ◽  
Seismic Reflection Data ◽  
North West ◽  
Reflection Data ◽  
Data Volume ◽  
Vertical Linkages ◽  
Fault Network

Basement fault reactivation, and the growth, interaction, and linkage with new fault segments are fundamentally three-dimensional and critical for understanding the evolution of fault network development in sedimentary basins. This paper analyzes the evolution of a complex, basement-involved extensional fault network on the Enderby Terrace on the eastern margin of the Dampier sub-basin, North West Shelf of Australia. A high-resolution, depth-converted, 3-D seismic reflection data volume is used to show that multiphase, oblique extensional reactivation of basement-involved faults controlled the development of the fault network in the overlying strata. Reactivation of the pre-existing faults initially led to the formation of overlying, en échelon Late Triassic−Middle Jurassic fault segments that, as WNW-directed rifting progressed on the margin, linked by breaching of relay zones to form two intersecting fault systems (F1 and F2−F4). Further reactivation in the latest Jurassic−Early Cretaceous (NNW-SSE extension) produced an additional set of en échelon fault arrays in the cover strata. The final fault network consists of main or principal faults and subordinate or splay faults, together with branch lines that link the various components. Our study shows that breaching of relay ramps and/or vertical linkages produces vertical and horizontal branch lines giving complex final fault geometries. We find that repeated activity of the basement-involved faults tends to form continuous and planar fault architectures that favor displacement transfer between the main constituent segments along strike and with depth.

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