GEOLOGIC HISTORY OF THE BASS BASIN

1974 ◽  
Vol 14 (1) ◽  
pp. 45 ◽  
Author(s):  
V. A. Robinson
Keyword(s):  
Early Cretaceous ◽  
Middle Eocene ◽  
Central Area ◽  
Structural Features ◽  
Northern Coast ◽  
Geologic History ◽  
Lower Tertiary ◽  
Structural Style ◽  
Late Tertiary ◽  
Structural Growth

The Bass Basin is located offshore between the southern coast of Victoria and the northern coast of Tasmania. It is bounded on the west by King Island and on the east by Flinders Island and the Bassian Rise. Water depths throughout the basin rarely exceed 270 feet (82 metres) and the area has been actively explored for hydrocarbons since 1963.The oldest sedimentary rocks encountered whilst drilling are Early Cretaceous, but the greatest volume of sediment was deposited during the Tertiary. Lithologies vary from continental sandstone, siltstone, shale, and coal in the older, non-marine Cretaceous to Middle Eocene section to limestone, marl, mudstone, and shale in the younger, marine Late Eocene to Recent section. Drilling and seismic data indicate that there was a considerable amount of volcanic activity in the Bass Basin throughout its history.Three distinctively different structural provinces can be recognised in the basin. These provinces are referred to as- a) southeastern area, b) central area, and c) northwestern area.The southeastern area exhibits the earliest structural growth (Early Cretaceous) whereas the structural growth in the central and northwestern areas occurred in Early and Late Tertiary respectively. Structural style also varies from tilted fault blocks with thousands of feet of vertical displacement in the southeastern area, to low relief, small anticlinal folds and minor faults in the northwestern area. Most of the prominent structural trends are oriented in a northwest-southeast direction which is parallel or sub-parallel to the present basin axis.Seismic and E-log correlations within the non-marine Cretaceous and Lower Tertiary section are extremely difficult and palynology is used to differentiate time-rock units. Five separate zones are identifiable within the Eocene and Paleocene, and the Cretaceous has been sub-divided into ten zones which can be related to the time-rock units in the adjacent Otway and Gippsland Basins.Non-commercial accumulations of hydrocarbons have been found in three different structural features: Pelican, Cormorant and Bass −3. These accumulations are from within the Lower Tertiary non-marine sequence known as the Eastern View Group.

COMPRESSIONAL GROWTH OF THE MINERVA ANTICLINE, OTWAY BASIN, SOUTHEAST AUSTRALIA—EVIDENCE OF OBLIQUE RIFTING

2004 ◽  
Vol 44 (1) ◽  
pp. 463 ◽  
Author(s):  
C.L. Schneider ◽  
K.C. Hill ◽  
N. Hoffman
Keyword(s):  
Early Cretaceous ◽  
Normal Faults ◽  
Sediment Distribution ◽  
East Central ◽  
Sea Floor ◽  
Structural Style ◽  
Isopach Maps ◽  
Structural Growth ◽  
Oblique Rifting ◽  
Sea Floor Spreading

Shipwreck Trough, east-central Otway Basin, evolved through Early Cretaceous to Santonian extension, followed by Campanian–Paleocene and Miocene to Recent pulses of compression.Onshore to offshore correlation of seismic sequences combined with 3D seismic mapping reveals that the Minerva anticline is located above an Early Cretaceous, northeast trending, basement-involved, graben. The graben-forming, northeast and north–south trending faults became largely inactive prior to the end of the Early Cretaceous. During the Turonian to Santonian, the northeast trending Point Ronald anticline and newly formed east–west trending normal faults controlled sediment distribution. The structural style changed in the Campanian as the northeast trending Minerva anticline began to form with a coeval, northwest-trending, axial-perpendicular fault array located along the crest of the fold. The location and orientation of this fault set is consistent with a compressional mechanism for fold growth. Similar compressional folding events during the Miocene–Recent modified and tightened the fold. Isopach maps show that during the Campanian to Maastrichtian, sediment thinned onto the nascent Minerva anticline, but accommodation rate outpaced structural growth, preserving a continuous sedimentary sequence.The timing of compressional fold growth is enigmatic. Campanian–Maastrichtian compression at the Minerva anticline was synchronous with over 10 km of extension accommodated by the Tartwaup–Mussel hingeline, 50 km to the south. Although the compression may be far-field effects associated with Tasman Basin sea floor spreading, we speculate that the Minerva anticline grew by transpression within a larger left-lateral transtensional Shipwreck Trough.

Surface and subsurface structural study of the Wadi El Rayan area, Southwest Fayoum, Egypt

1983 ◽  
Vol 120 (1) ◽  
pp. 59-66
Author(s):  
M. M. Youssef ◽  
H. M. El Khashab
Keyword(s):  
Structural Study ◽  
Middle Eocene ◽  
Structural Features ◽  
Aerial Photographs ◽  
Field Observations ◽  
Geologic Map

SummaryThe surface geologic map of the Wadi El Rayan area, based on the study of aerial photographs and field observations, is correlated with seismic structural two-way time maps for the basement, the top of Cenomanian and the base of Tertiary horizons. Major structural features comprise a northeasterly faulted plunging anticlinal stretch traversing the NW-SE Wadi El Rayan depression. Three sets (ENE-WSW, NW-SE and NE-SW) of faults dissect the area. Folding movement was still active at least to the end of Middle Eocene epoch. ENE-WSW faults affecting the basement, and traced in higher levels, have the same trend as the fold axes. It is thus possible that compressional features appearing on the surface and subsurface horizons are in part due to thrusting in deeper levels that took place parallel to folding.

scholarly journals Late Tertiary Geologic History of the Continental Shelf off Northwestern Palawan, Philippines

1973 ◽  
Vol 6 ◽  
pp. 165-176 ◽  
Author(s):  
E.V. Tamesis ◽  
◽  
E.V. Manalac ◽  
C.A. Reyes ◽  
L.M. Ote
Keyword(s):  
Continental Shelf ◽  
Geologic History ◽  
Late Tertiary ◽  
History Of

Interplay between tectonic inheritance and salt tectonics in the tectono-sedimentary evolution of the Sahel basin (eastern Tunisia): implications for hydrocarbon prospectivity

2021 ◽  
Author(s):  
Wajdi Belkhiria ◽  
Haifa Boussiga ◽  
Imen Hamdi Nasr ◽  
Adnen Amiri ◽  
Mohamed Hédi Inoubli
Keyword(s):  
Early Cretaceous ◽  
Late Cretaceous ◽  
Gravity Data ◽  
Hydrocarbon Exploration ◽  
Passive Margin ◽  
Growth Strata ◽  
Tectonic Inheritance ◽  
Sedimentary Evolution ◽  
Structural Style ◽  
Half Graben

<p>The Sahel basin in eastern Tunisia has been subject for hydrocarbon exploration since the early fifties. Despite the presence of a working petroleum system in the area, most of the drilled wells were dry or encountered oil shows that failed to give commercial flow rates. A better understanding of the tectono-sedimentary evolution of the Sahel basin is of great importance for future hydrocarbon prospectivity. In this contribution, we present integration of 2D seismic reflection profiles, exploration wells and new acquired gravity data. These subsurface data reveal that the Sahel basin developed as a passive margin during Jurassic-Early Cretaceous times and was later inverted during the Cenozoic Alpine orogeny. The occurrence of Triassic age evaporites and shales deposited during the Pangea breakup played a fundamental role in the structural style and tectono-sedimentary evolution of the study area. Seismic and gravity data revealed jointly important deep-seated extensional faults, almost along E-W and few along NNE–SSW and NW-SE directions, delimiting horsts and grabens structures. These syn-rift extensional faults controlled deposition, facies distribution and thicknesses of the Jurassic and Early cretaceous series. Most of these inherited deep-seated normal and transform faults are ornamented by different types of salt-related structures. The first phase of salt rising was initiated mainly along these syn-extensional faults in the Late Jurassic forming salt domes and continued into the Early and Late Cretaceous leading to salt-related diapir structures. During this period, the salt diapirism was accompanied by the development of salt withdrawal minibasins, characterized important growth strata due the differential subsidence. These areas represent important immediate kitchen areas to the salt-related structures. The later Late Cretaceous - Cenozoic shortening phases induced preferential rejuvenation of the diapiric structures and led to the inversion of former graben/half-graben structures and ultimately to vertical salt welds along salt ridges. These salt structures represent key elements that remains largely undrilled in the Sahel basin. Our results improve the understanding of salt growth in eastern Tunisia and consequently greatly impact the hydrocarbon prospectivity in the area.</p>

Replacement phenomena in tantalum minerals from rare-metal pegmatites in South Africa and Namibia

1989 ◽  
Vol 53 (373) ◽  
pp. 571-581 ◽  
Author(s):  
Joy R. Baldwin
Keyword(s):  
South Africa ◽  
Electron Microprobe ◽  
Marginal Zone ◽  
Central Area ◽  
Rare Metal ◽  
Structural Features ◽  
Variable Composition ◽  
Scattered Electron ◽  
Intermediate Composition

AbstractManganotantalite replacement by (1) microlite and (2) ferrotantalite, and changes in composition of uranoan microlite from rare-metal pegmatites in South Africa and Namibia have been investigated with the electron microprobe. A uranmicrolite from Karibib, Namibia contained 14.35% UO2, 1.03% PbO, 56.12% Ta2O5, 13.18% Nb2O5, 0.58% Fe2O3, 6.87% CaO, 0.54% SrO, 0.59% MnO, 0.86% Na2O and 0.47% F. Analyses along traverses across a 1.3 mm uranoan microlite, Tantalite Valley, Namibia, revealed two essentially distinct compositions: a more hydrated rim area of 200 µm radius containing 7% higher Ta2O5, 10% lower CaO and 1.3% lower F than a main central area of slightly variable composition. Back-scattered electron images reveal zoning and distinctive subspheroidal structures. New data and structural features are given for radioactive uranoan microlite from Namaqualand, South Africa. These crystals contain remnants of a bismuth phase and are in various stages of replacement. In the microlites replacing manganotantalite, the microlite reflects the composition of the replaced mineral. At Rubicon Mine, Karibib, a narrow marginal zone of mangantantalite is replaced by ferrotantalite along cleavages; a zone of intermediate composition is apparent. Detailed traverses have been completed across all of these crystals.

Building Utopia

2020 ◽  
pp. 582-596
Author(s):  
Marcus Waithe
Keyword(s):  
Built Environment ◽  
Structural Features ◽  
Medieval Architecture ◽  
Structural Style ◽  
Conscious Effort

William Morris’s News from Nowhere (1890) contains many detailed descriptions of buildings. As products of the utopian society described, most of these buildings are new. Yet their form is evidently ‘medieval’, or ‘medievalist’ (and therefore at odds, in some sense, with our preconceptions of the ‘new’). This chapter asks what such terms mean, or might mean, in the context of a built environment that stands outside the margin of known history. In the process, it describes the structural features to which Morris draws attention, with more historical and conceptual precision than has yet been attempted. At the heart of this discussion is a concern to classify a future architecture that resembles medieval architecture without any conscious effort of stylistic homage on the part of its builders. The problematic implication is that ‘medieval’ architecture will always be the natural, or ‘structural’, style of a happy and liberated people.

Pre-, syn-, and post-imbrication deformation of carbonate slices along the southern Quebec Appalachian front – implications for hydrocarbon exploration

2007 ◽  
Vol 44 (4) ◽  
pp. 543-564 ◽  
Author(s):  
Stephan Séjourné ◽  
Michel Malo
Keyword(s):  
Strain Relaxation ◽  
Structural Features ◽  
Strike Slip ◽  
Hydrocarbon Exploration ◽  
Normal Faults ◽  
Structural Style ◽  
Slip Planes ◽  
Bed Thickness ◽  
Seismic Scale ◽  
Extensional Structures

Thrust-imbricated shelf-carbonate slices form a wide but poorly understood part of the southernmost Quebec Appalachian structural front. Comprehensive structural analysis of two slices exposed at surface, the Saint-Dominique and Philipsburg slices, shows that pre- and post-imbrication structures are important in defining the final architecture of the slices. The dominant structural style is characterized by thrusts and associated asymmetrical folds, tear faults, oblique ramps and incipient backthrusts developed during WNW–ESE shortening. A forward-breaking (piggy-back) sequence of thrusting is recognised, as well as minor out-of-sequence thrusting. The complexity and diversity of contractional structures is directly influenced by lithology (bed thickness and shale content). Bedding-parallel slip planes are important in the concentration (activation and reactivation) of deformation, in that there are the loci for veining, faulting, and folding. Recognition of lithostructural units provides guidelines for the identification of sub-seismic-scale structural traps in subsurface investigations. Extensional structures (normal faults, veins, tension gashes) are found within all carbonate slices, as well as within the footwall of their basal thrusts. Only a few pre-imbrication normal faults have been identified, one of which is a growth fault. Post-imbrication extensional structures are linked with strain relaxation after overthrusting. A widespread front-parallel strike-slip faulting event postdates all other structural features and can have a major impact on the compartmentalization of potential hydrocarbon reservoirs.

Permineralized fruits and seeds from the Princeton chert (Middle Eocene) of British Columbia: Vitaceae

1990 ◽  
Vol 68 (2) ◽  
pp. 288-295 ◽  
Author(s):  
Sergio R. S. Cevallos-Ferriz ◽  
Ruth A. Stockey
Keyword(s):  
British Columbia ◽  
Middle Eocene ◽  
Outer Zone ◽  
Structural Features ◽  
Anatomical Structure ◽  
Thin Walled ◽  
Polyhedral Cells ◽  
A New Species

Four permineralized vitaceous seeds are described from the Middle Eocene Princeton chert, Allenby Formation, British Columbia. Three distinct types of ruminate perchalazal seeds are recognized, one is described as a new species Ampelocissus similkameenensis Cevallos-Ferriz et Stockey sp.nov., while the remaining seeds are referred to as type 1 and type 2 seeds. Five integumentary zones are recognized in each seed: zone 1 is an outer zone of thin-walled rectangular to polyhedral cells; zone 2 is a zone of thick-walled sclereids; zone 3 is a zone of cells with spiral thickenings; zone 4 is a zone of rectangular thin-walled cells (when preserved); and zone 5 is a zone of tangentially elongated thin-walled cells with dark contents. The chalaza in seeds of A. similkameenensis and the type 1 seed has three distinct zones, while in the type 2 seed it contains cells similar to integumentary zone 2. These Princeton seeds illustrate that structural features of Eocene Vitaceae include characters unlike those of extant taxa. This information contributes to our knowledge of anatomical structure within the group as a whole and underscores the need for review of both fossil and extant Vitaceae. Paucity of vitaceous seeds in the Princeton chert compared to the large number of preserved aquatic and semiaquatic remains suggests that they represent plants that grew in a nearby environment. Abrasion of the integument suggests that like extant seeds, they may have been dropped after passing through the gut of a bird.

Models of the Bouguer gravity and geologic structure at Yucca Flat, Nevada

Geophysics ◽  
1988 ◽  
Vol 53 (2) ◽  
pp. 231-244 ◽  
Author(s):  
John F. Ferguson ◽  
Roger N. Felch ◽  
Carlos L. V. Aiken ◽  
John S. Oldow ◽  
Holly Dockery
Keyword(s):  
Structural Information ◽  
Three Dimensional ◽  
Structural Features ◽  
Bouguer Gravity ◽  
Three Dimensional Model ◽  
Geologic History ◽  
The West ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Low Pass

The Bouguer gravity anomaly at Yucca Flat, Nevada, has been modeled by two different techniques: the Cordell‐Henderson and Parker‐Oldenburg methods. The three‐dimensional model has incorporated known density and structural information where possible. These models predict the structural relief on the Cenozoic‐Paleozoic contact to within 150 m or about 15 percent of the actual depth. The three‐dimensional Parker‐Oldenburg method has been found to be efficient in an application involving a large (9000 sample) data base. Numerical stability was ensured by the application of a consistent regularization (a low‐pass filter tuned to suppress the noise‐dominated portion of the data spectrum) of the downward continuation operator. The use of a single regularizing filter for the entire model is not completely satisfactory due to the oversmoothing of shallow regions of the basin. The model is useful in the delineation of the geologic history of the area. Structural features in the model support the hypothesis that regional stress fields rotated significantly during the Tertiary. Major structural elements of the basin are well defined on the Cenozoic‐Paleozoic interface. The principal basin‐bounding fault is the large‐throw Carpetbag fault on the west. This fault was most active during the earliest phases of subsidence. The Yucca fault is seen to be a much smaller feature in the model presented here. The basin is rotated down to the west, with normal hinge faults on the eastern margin.

SEISMIC EVIDENCE FOR REVERSE AND WRENCH FAULT TECTONICS—CLIFF HEAD OIL FIELD, PERTH BASIN

2005 ◽  
Vol 45 (1) ◽  
pp. 381 ◽  
Author(s):  
C.C. Hodge
Keyword(s):  
Early Cretaceous ◽  
Seismic Data ◽  
Experimental Models ◽  
Oil Field ◽  
Fracture Density ◽  
Injection Wells ◽  
Structural Style ◽  
Fault Tectonics ◽  
Wrench Fault ◽  
Transfer Zone

Seismic interpretation of the Cliff Head oil field has shown it to be structurally complex with reverse faults, wrench faults and listric faults mapped at both field and reservoir scale within the Permo-Triassic section.The Cliff Head field overlies the Abrolhos Transfer Zone and has strong similarity to the progressive evolution, internal structure and rhomboid map geometry in experimental models of restraining stepovers in strikeslip systems. It is concluded that the Cliff Head oil field is a pop-up structure formed during the Permian and early Cretaceous within a restrained convergent wrench system—the result of sinistral transpression.A similar style of faulting could be applied when mapping seismic data in other offshore areas and especially the onshore Perth Basin with its poorer seismic data quality.Interpretation of prospects with a strong reverse or wrench component has implications for the timing of hydrocarbon emplacement and the potential for seal breach and leakage. Furthermore, paleo-structural style will determine fracture density and orientation and may be critical in determining optimum design of producer and injection wells during field development.It is recommended that interpreters of seismic data in the Perth Basin treat the fault patterns and structural trends of the Permian and early Cretaceous as different structural packages. The two should only be linked when it is very clear that there is a strong early Cretaceous overprint.

Sign in / Sign up

Export Citation Format

Share Document