Deepwater Exmouth Plateau, North Carnarvon Basin: preliminary investigations into ridge and furrow features

2010 ◽  
Vol 50 (2) ◽  
pp. 731 ◽  
Author(s):  
Kevin Day ◽  
Julie Gale ◽  
John Smallwood
Keyword(s):  
Seabed Sediment ◽  
Shallow Subsurface ◽  
Exmouth Plateau ◽  
The North ◽  
Seismic Resolution ◽  
Plateau Area ◽  
Gravity Driven ◽  
Sediment Deformation ◽  
Sigsbee Escarpment ◽  
Lower Slope

Numerous fields of long, shallow subsurface linear ridge and furrow features were mapped during the interpretation of a 3D seismic dataset covering Hess Exploration Australia Pty Ltd’s WA–390–P deepwater Exmouth Plateau permit. These kilometre scale features are often slope parallel and have separations of between 100 to 400 metres between ridge crests. Heights range from the limit of seismic resolution up to approximately nine metres. Similar linear shallow subsurface features have been interpreted in the North Falkland Basin in Desire Petroleum’s Tranches C and D permits. Initial investigations suggest that these features appear similar to the Holocene and older mega furrows/palaeo-mega furrows identified along the lower slope/rise in the Gulf of Mexico, most notably along the base of the Sigsbee Escarpment, and along other continental slope/rise settings. Evidence of seabed and shallow sub-seabed sediment instability in the form of slumps and slides together with the effects of shallow sediment deformation and dewatering are also visible across the WA-390-P area. Ridge and furrow features from the deepwater Exmouth Plateau area are described in detail alongside examples from the North Falkland Basin. It is suggested that interaction between gravity driven downslope processes, sediment dewatering and alongslope sedimentary processes could be a possible mechanism of formation for these features. Horizontal and vertical delineation of these features can contribute towards regional understanding of subsurface sediment instability.

scholarly journals The origin of till sequences by subglacial sediment deformation beneath mid-latitude ice sheets

1996 ◽  
Vol 22 ◽  
pp. 75-84 ◽  
Author(s):  
G. S. Boulton
Keyword(s):  
North American ◽  
Large Scale ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Glacial Cycle ◽  
Erosion And Deposition ◽  
The North ◽  
Sediment Deformation ◽  
Source Materials ◽  
The Last Glacial

A theory of erosion and deposition as a consequence of subglacial sediment deformation over beds of unlithified sediment is reviewed and applied to large-scale till sequences formed on the southern flanks of the North American and British and European ice sheets during the last glacial cycle. The distribution of till thickness, till lithology in relation to source materials and intra-till erosion surfaces along a flowline in the Michigan lobe of the North American ice sheet are shown to be compatible with the deformational theory but not with other modes of till genesis. It is then demonstrated, in the case of the British ice sheet, how the assumption of a deformational origin for tills can be used to infer time-dependent patterns of ice-sheet dynamic behaviour. By reference to an example from the Netherlands, it is argued that many till sequences interpreted as melt-out tills are more likely to have formed by subglacial sediment deformation.

THE ROLE OF AMPLITUDE VERSUS OFFSET TECHNOLOGY IN PROMOTING OFFSHORE PETROLEUM EXPLORATION IN AUSTRALIA

2007 ◽  
Vol 47 (1) ◽  
pp. 163 ◽  
Author(s):  
P. E. Williamson ◽  
F. Kroh
Keyword(s):  
Petroleum Exploration ◽  
Gas Field ◽  
North West ◽  
Preliminary Results ◽  
Exmouth Plateau ◽  
The North ◽  
Amplitude Versus Offset ◽  
Cable Lines ◽  
The Cost ◽  
Amplitude Versus

Amplitude versus offset (AVO) technology has proved itself useful in petroleum exploration in various parts of the world, particularly for gas exploration. To determine if modern AVO compliant processing could identify potential anomalies for exploration of open acreage offshore Australia, Geoscience Australia reprocessed parts of four publicly available long cable lines. These lines cover two 2006 acreage release areas on the Exmouth Plateau and in the Browse Basin on the North West Shelf. An earlier study has also been done on two publicly available long cable lines from Geoscience Australia’s Bremer Basin study and cover areas from the 2005 frontier acreage release on the southern margin. The preliminary results from these three reprocessing efforts produced AVO anomalies and were made publicly available to assist companies interested in assessing the acreage. The results of the studies and associated data are available from Geoscience Australia at the cost of transfer.The AVO data from the Exmouth Plateau show AVO anomalies including one that appears to be at the Jurassic level of the reservoir in the Jansz/Io supergiant gas field in adjacent acreage to the north. The AVO data from the Caswell Sub-basin of the Browse Basin show an AVO anomaly at or near the stratigraphic zone of the Brecknock South–1 gas discovery to the north. The geological settings of strata possibly relating to two AVO anomalies in the undrilled Bremer Basin are in the Early Cretaceous section, where lacustrine sandstones are known to occur. The AVO anomalies from the three studies are kilometres in length along the seismic lines.These preliminary results from Geoscience Australiaand other AVO work that has been carried out by industry show promise that AVO compliant processing has value—particularly for gas exploration offshore Australia—and that publicly available long-cable data can be suitable for AVO analysis.

Faulting in Mars Polar Layered deposits modeled by HCA method

2020 ◽  
Author(s):  
Paola Cianfarra ◽  
Costanza Rossi ◽  
Francesco Salvini ◽  
Laura Crispini
Keyword(s):  
Cross Section ◽  
Hydrothermal Activity ◽  
Geological Mapping ◽  
Normal Faults ◽  
Natural Material ◽  
Shallow Subsurface ◽  
Ice Caps ◽  
The North ◽  
Wide Range ◽  
Polar Layered Deposits

<p>The polar layered deposits (PLD) of Mars constitute the water ice stratigraphy of polar spiral troughs up to several kilometers thick (Phillips et al., 2011; Smith et al. 2015). PLD cross section profiles from the Shallow Subsurface Radar (SHARAD) instrument on NASA’s Mars Reconnaissance Orbiter, show the presence of internal discontinuities within these layers (Foss et al., 2017; Putzig et al., 2017). The mechanisms responsible for these deformations are still an open issue (Guallini et al., 2017) and this work represents the contribution of stress-related deformations. Layered ice is simulated by a mesh of cells within a HCA grid build replicating the physical properties and preserving volumes following balanced cross-section principles. Three major types of link exist among adjacent cells: 1. intra-layer relations link cells belonging to the same layer; 2. inter-layer relations regulate the relationships among adjacent layers; 3. discontinuity relations correspond to the presence of ruptures such as faults (Salvini et al., 2001). The HCA method allows to replicate the natural material anisotropies, such as rocks and ice sheet internal layering, and to simulate complex tectonic evolutionary paths (Cianfarra and Salvini, 2016; Cianfarra and Maggi, 2017). The models allow simulating the kinematics of the internal architecture of the layered deposits from both the north and the south Martian ice caps. In particular the observed stratigraphy (geometries and thickness of the ice layers) is replicated as resulting from the relative, normal movement among blocks separated by listric shaped normal faults and minor inversions.</p><p>The used HCA numerical methodology revealed an effective tool to support planetary geological mapping and 3D subsurface geological reconstructions. Through the integration of a net of spatially distributed along- and across- strike (balanced) sections it is possible to simulate the 4D (3D plus time) geological evolution of buried and/or topographic structures. Results have a wide range of applications including the optimal selection of landing sites for scheduled and future planetary exploration missions, as well as unravelling the geological and structural setting of enigmatic features on the planetary surfaces affected, for example, by salt tectonism, volcano-tectonics, tectonically-related hydrothermal activity, fluid storage and release, and ice tectonics.</p>

scholarly journals Integrated uppermost Campanian–Maastrichtian calcareous nannofossil and foraminiferal biostratigraphic zonation of the northwestern margin of Australia

2003 ◽  
Vol 22 (1) ◽  
pp. 29-62 ◽  
Author(s):  
R. W. Howe ◽  
R. J. Campbell ◽  
J. P. Rexilius
Keyword(s):  
Planktonic Foraminifera ◽  
Petroleum Exploration ◽  
Calcareous Nannofossil ◽  
Ocean Drilling Program ◽  
Exmouth Plateau ◽  
Ocean Drilling ◽  
The North ◽  
Northwestern Margin ◽  
Upper Maastrichtian ◽  
Upper Campanian

Abstract. During the latest Campanian–Maastrichtian the northwestern Australian margin was situated between the cool-water Austral Province to the south and the warm-water Tethyan Province to the north. The transitional nature of calcareous microfossil assemblages on the margin makes application of Tethyan biostratigraphic zonation schemes awkward, as many marker-species are missing or have different ranges. This study presents an integrated uppermost Campanian–Maastrichtian calcareous microfossil zonation based on two Ocean Drilling Program (ODP) holes on the Exmouth Plateau and eight petroleum exploration wells from the Vulcan Sub-basin. The zonation is refined and revised from the previously unpublished KCN (nannofossils), KPF (planktonic foraminifera), KBF (benthonic foraminifera) and KCCM (composite nannofossil and planktonic foraminifera) zonations, which are commonly used for petroleum exploration wells drilled on the northwestern margin. Revision of the zonations has highlighted a major Upper Campanian to lower Upper Maastrichtian disconformity on the Exmouth Plateau, which went largely unnoticed in previous examinations of the ODP material, but had been recorded previously elsewhere on the northwestern margin. The duration of the disconformity in the Vulcan Sub-basin is unclear, since intervals of the succession may be condensed in this area.

Soil temperature regime in a forested Appalachian watershed

1986 ◽  
Vol 16 (3) ◽  
pp. 624-629 ◽  
Author(s):  
S. J. Tajchman ◽  
C. M. Minton
Keyword(s):  
Surface Temperature ◽  
Soil Temperature ◽  
Soil Layer ◽  
The North ◽  
Soil Temperature Regime ◽  
Temperature Ranges ◽  
The Mean ◽  
The Difference ◽  
Topographic Positions ◽  
Lower Slope

Daily and seasonal variations in soil temperature at various topographic positions in a forested catchment are compared. The experimental sites were designed as ridgetop, north-facing lower slope, south-facing lower slope, and southwest-facing slope. On sunny days during the growing season, the surface temperature had the greatest amplitude (7.8 °C) at the south-facing upper slope and the smallest amplitude (4.0 °C) at the north-facing slope; the remaining sites were intermediate. The maximum surface temperature was observed in the afternoon at all sites. With increasing depth, daily soil temperature ranges diminished and, below 10 cm depth, they were less than 1 °C. Under overcast conditions, daily soil temperature fluctations lessened. For individual months, the mean temperatures of the 2–30 cm soil layer generally varied among all sites by less than 1 °C and never the difference exceeded 1.8 °C. The surface temperature variations and their differences among sites appear to be the most distinguished feature of the soil thermal regime and they seem to be aspect related.

scholarly journals Towards a framework for the quantitative assessment of trawling impact on the seabed and benthic ecosystem

2015 ◽  
Vol 73 (suppl_1) ◽  
pp. i127-i138 ◽  
Author(s):  
A. D. Rijnsdorp ◽  
F. Bastardie ◽  
S. G. Bolam ◽  
L. Buhl-Mortensen ◽  
O. R. Eigaard ◽  
...  
Keyword(s):  
Benthic Community ◽  
Ecological Impact ◽  
Biological Traits ◽  
Fishing Gear ◽  
Ecological Role ◽  
Seabed Sediment ◽  
The North ◽  
Biological Trait ◽  
The Individual ◽  
The Impact

Abstract A framework to assess the impact of mobile fishing gear on the seabed and benthic ecosystem is presented. The framework that can be used at regional and local scales provides indicators for both trawling pressure and ecological impact. It builds on high-resolution maps of trawling intensity and considers the physical effects of trawl gears on the seabed, on marine taxa, and on the functioning of the benthic ecosystem. Within the framework, a reductionist approach is applied that breaks down a fishing gear into its components, and a number of biological traits are chosen to determine either the vulnerability of the benthos to the impact of that gear component, or to provide a proxy for their ecological role. The approach considers gear elements, such as otter boards, twin trawl clump, and groundrope, and sweeps that herd the fish. The physical impact of these elements on the seabed, comprising scraping of the seabed, sediment mobilization, and penetration, is a function of the mass, size, and speed of the individual component. The impact of the elements on the benthic community is quantified using a biological-trait approach that considers the vulnerability of the benthic community to trawl impact (e.g. sediment position, morphology), the recovery rate (e.g. longevity, maturation age, reproductive characteristics, dispersal), and their ecological role. The framework is explored to compare the indicators for pressure and ecological impact of bottom trawling in three main seabed habitat types in the North Sea. Preliminary results show that the Sublittoral mud (EUNIS A5.3) is affected the most due to the combined effect of intensive fishing and large proportions of long-lived taxa.

scholarly journals Sedimentology and sequence stratigraphy of paralic and shallow marine Upper Jurassic sandstones in the northern Danish Central Graben

2003 ◽  
Vol 1 ◽  
pp. 367-402 ◽  
Author(s):  
Peter N. Johannessen
Keyword(s):  
Sea Level ◽  
Upper Jurassic ◽  
High Energy ◽  
Salt Dome ◽  
The South ◽  
The West ◽  
Relative Sea Level ◽  
Shallow Marine ◽  
The North ◽  
Plateau Area

Paralic and shallow marine sandstones were deposited in the Danish Central Graben during Late Jurassic rifting when half-grabens were developed and the overall eustatic sea level rose. During the Kimmeridgian, an extensive plateau area consisting of the Heno Plateau and the Gertrud Plateau was situated between two highs, the Mandal High to the north, and the combined Inge and Mads Highs to the west. These highs were land areas situated on either side of the plateaus and supplied sand to the Gertrud and Heno Plateaus. Two graben areas, the Feda and Tail End Grabens, flanked the plateau area to the west and east, respectively. The regressive–transgressive succession consists of intensely bioturbated shoreface sandstones, 25–75 m thick. Two widespread unconformities (SB1, SB2) are recognised on the plateaus, forming the base of sequence 1 and sequence 2, respectively. These unconformities were created by a fall in relative sea level during which rivers may have eroded older shoreface sands and transported sediment across the Heno and Gertrud Plateaus, resulting in the accumulation of shoreface sandstones farther out in the Feda and Tail End Grabens, on the south-east Heno Plateau and in the Salt Dome Province. During subsequent transgression, fluvial sediments were reworked by high-energy shoreface processes on the Heno and Gertrud Plateaus, leaving only a lag of granules and pebbles on the marine transgressive surfaces of erosion (MTSE1, MTSE2). The sequence boundary SB1 can be traced to the south-east Heno Plateau and the Salt Dome Province, where it is marked by sharp-based shoreface sandstones. During low sea level, erosion occurred in the southern part of the Feda Graben, which formed part of the Gertrud and Heno Plateaus, and sedimentation occurred in the Norwegian part of the Feda Graben farther to the north. During subsequent transgression, the southern part of the Feda Graben began to subside, and a succession of backstepping back-barrier and shoreface sediments, 90 m thick, was deposited. In the deep Tail End and Feda Grabens and the Salt Dome Province, sequence boundary SB2 is developed as a conformity, indicating that there was not a significant fall in relative sea level in these grabens, probably as a result of high subsidence rates. Backstepping lower shoreface sandstones overlie SB2 and show a gradual fining-upwards to offshore claystones that are referred to the Farsund Formation. On the plateaus, backstepping shoreface sandstones of sequence 2 are abruptly overlain by offshore claystones, indicating a sudden deepening and associated cessation of sand supply, probably caused by drowning of the sediment source areas on the Mandal, Inge and Mads Highs. During the Volgian, the Gertrud Plateau began to subside and became a graben. During the Late Kimmeridgian – Ryazanian, a long-term relative sea-level rise resulted in deposition of a thick succession of offshore claystones forming highstand and transgressive systems tracts on the Heno Plateau, and in the Gertrud, Feda and Tail End Grabens.

scholarly journals A synthetic map of the northwest European Shelf sedimentary environment for applications in marine science

2017 ◽  
Author(s):  
Robert J. Wilson ◽  
Douglas C. Speirs ◽  
Alessandro Sabatino ◽  
Michael R. Heath
Keyword(s):  
Grain Size ◽  
North Sea ◽  
Sedimentary Environment ◽  
International Investment ◽  
Marine Policy ◽  
Continuous Variables ◽  
Seabed Sediment ◽  
The North ◽  
Wide Range ◽  
The North Sea

Abstract. Seabed sediment mapping is important for a wide range of marine policy, planning and scientific issues, and there has been considerable national and international investment around the world in the collation and synthesis of sediment data sets. However, in Europe at least, much of this effort has been directed towards seabed classification and mapping of discrete habitats. Scientific users often have to resort to reverse-engineering these classifications to recover continuous variables such as mud content and median grain size that are required for many ecological and biophysical studies. Here we present a new set of 0.125 by 0.125° resolution synthetic maps of continuous properties of the northwest European sedimentary environment, extending from the Bay of Biscay to the northern limits of the North Sea and the Faroe Islands. The maps are a blend of gridded survey data, and statistically modelled values based on distributions of bed shear stress due to tidal currents and waves, and bathymetric properties. Recent work has shown that statistical models can predict sediment composition in British waters and the North Sea with high accuracy, and here we extend this to the entire shelf and to the mapping of other key seabed parameters. The maps include percentage compositions of mud, sand and gravel; porosity and permeability; median grain size of the whole-sediment and of the sand and the gravel fractions; carbon and nitrogen content of sediments; percentage of seabed area covered by rock; mean and maximum depth-averaged tidal velocity and wave-orbital velocity at the seabed; and mean monthly natural disturbance rates. A number of applications for these maps exist, including species distribution modelling and the more accurate representation of seafloor biogeochemistry in ecosystem models. The data products are available from doi:10.15129/07bc686e-a354-40de-8c08-372ced7aad64.

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