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71-402: The Otway Basin is a northwest trending sedimentary basin located along the southern coast of Australia . The basin covers an area of 150,000 square kilometers and spans from southeastern South Australia to southwestern Victoria , with 80% lying offshore in water depths ranging from 50-3,000 meters. Otway represents a passive margin rift basin and is one of a series of basins located along

142-552: A 6.5 Ma hiatus, rifting renewed and rift-related subsidence began in the Turonian . This rifting phase is marked by a change in crustal extension direction from north-south to northeast-southwest resulting in the deposition of large and deep depocenters in the mid- and off-shore basin. Syn-rift deposition includes ~1300 meters of fluvial and deltaic sediments that comprise the Shipwreck Group. A major marine transgression in

213-412: A continental shelf, continental slope, continental rise, and abyssal plain. The morphological expression of these features are largely defined by the underlying transitional crust and the sedimentation above it. Passive margins defined by a large fluvial sediment budget and those dominated by coral and other biogenous processes generally have a similar morphology. In addition, the shelf break seems to mark

284-422: A convergent plate tectonic boundary in the gap between an active volcanic arc and the associated trench , thus above the subducting oceanic plate. The formation of a forearc basin is often created by the vertical growth of an accretionary wedge that acts as a linear dam, parallel to the volcanic arc, creating a depression in which sediments can accumulate. Trench basins are deep linear depressions formed where

355-417: A crustal boundary between oceanic lithosphere and continental lithosphere is a plate boundary . Active margins are found on the edge of a continent where subduction occurs. These are often marked by uplift and volcanic mountain belts on the continental plate. Less often there is a strike-slip fault , as defines the southern coastline of West Africa . Most of the eastern Indian Ocean and nearly all of

426-514: A high probability of preservation. In contrast, sedimentary basins formed on oceanic crust are likely to be destroyed by subduction . Continental margins formed when new ocean basins like the Atlantic are created as continents rift apart are likely to have lifespans of hundreds of millions of years, but may be only partially preserved when those ocean basins close as continents collide. Sedimentary basins are of great economic importance. Almost all

497-459: A large three-dimensional body of sedimentary rock . They form when long-term subsidence creates a regional depression that provides accommodation space for accumulation of sediments. Over millions or tens or hundreds of millions of years the deposition of sediment , primarily gravity-driven transportation of water-borne eroded material, acts to fill the depression. As the sediments are buried, they are subject to increasing pressure and begin

568-445: A load is placed on the lithosphere, it will tend to flex in the manner of an elastic plate. The magnitude of the lithospheric flexure is a function of the imposed load and the flexural rigidity of the lithosphere, and the wavelength of flexure is a function of flexural rigidity of the lithospheric plate. Flexural rigidity is in itself, a function of the lithospheric mineral composition, thermal regime, and effective elastic thickness of

639-606: A million, and their sedimentary fills range from one to almost twenty kilometers in thickness. A dozen or so common types of sedimentary basins are widely recognized and several classification schemes are proposed, however no single classification scheme is recognized as the standard. Most sedimentary basin classification schemes are based on one or more of these interrelated criteria: Although no one basin classification scheme has been widely adopted, several common types of sedimentary basins are widely accepted and well understood as distinct types. Over its complete lifespan

710-465: A number of ways: The high velocities (V p > 7 km) and large thicknesses of the LCBs are evidence that supports the case for plume-fed accretion (mafic thickening) underplating the crust during continental breakup. LCBs are located along the continent-ocean transition but can sometimes extend beneath the continental part of the rifted margin (as observed in the mid-Norwegian margin for example). In

781-485: A particular period of geologic time, a 'stratigraphic succession', that geologists continue to refer to as a sedimentary basin even if it is no longer a bathymetric or topographic depression. The Williston Basin , Molasse basin and Magallanes Basin are examples of sedimentary basins that are no longer depressions. Basins formed in different tectonic regimes vary in their preservation potential . Intracratonic basins, which form on highly-stable continental interiors, have

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852-658: A result of the closing of a major ocean through continental collision resulting from plate tectonics. As a result the sedimentary record of inactive passive margins often are found as thick sedimentary sequences in mountain belts. For example the passive margins of the ancient Tethys Ocean are found in the mountain belts of the Alps and Himalayas that formed when the Tethys closed. Many authors recognize two subtypes of foreland basins: Peripheral foreland basins Retroarc foreland basins A sedimentary basin formed in association with

923-561: A result of two major, basin-wide rifting phases. At the onset of major north-south rifting in the late Jurassic several east-west trending extensional depocenters developed in the onshore part of the basin to define the Inner Otway Basin. Renewed rifting in the late Cretaceous was driven by a change in crustal extension style from north-south to northeast-southwest resulting in the structurally different, northwest-southeast trending Torquay, Morum, Nelson, and Hunter Sub-basins in

994-575: A single sedimentary basin can go through multiple phases and evolve from one of these types to another, such as a rift process going to completion to form a passive margin. In this case the sedimentary rocks of the rift basin phase are overlain by those rocks deposited during the passive margin phase. Hybrid basins where a single regional basin results from the processes that are characteristic of multiple of these types are also possible. Terrestrial rift valleys Proto-oceanic rift troughs Passive margins are long-lived and generally become inactive only as

1065-404: A subducting oceanic plate descends into the mantle, beneath the overriding continental (Andean type) or oceanic plate (Mariana type). Trenches form in the deep ocean but, particularly where the overriding plate is continental crust they can accumulate thick sequences of sediments from eroding coastal mountains. Smaller 'trench slope basins' can form in association with a trench can form directly atop

1136-525: Is a piece of rubber, which thins in the middle when stretched.) An example of a basin caused by lithospheric stretching is the North Sea – also an important location for significant hydrocarbon reserves. Another such feature is the Basin and Range Province which covers most of Nevada, forming a series of horst and graben structures. Tectonic extension at divergent boundaries where continental rifting

1207-587: Is accompanied by little mantle melting and volcanism. Non-volcanic transitional crust consists of stretched and thinned continental crust. Non-volcanic margins are typically characterized by continentward-dipping seismic reflectors (rotated crustal blocks and associated sediments) and low P-wave velocities (<7.0 km/s) in the lower part of the transitional crust. Volcanic margins form part of large igneous provinces, which are characterised by massive emplacements of mafic extrusives and intrusive rocks over very short time periods. Volcanic margins form when rifting

1278-651: Is accompanied by significant mantle melting, with volcanism occurring before and/or during continental breakup. The transitional crust of volcanic margins is composed of basaltic igneous rocks , including lava flows, sills , dykes , and gabbro . Volcanic margins are usually distinguished from non-volcanic (or magma-poor) margins (e.g. the Iberian margin, Newfoundland margin) which do not contain large amounts of extrusive and/or intrusive rocks and may exhibit crustal features such as unroofed, serpentinized mantle. Volcanic margins are known to differ from magma-poor margins in

1349-550: Is characterized by abandoned rifts and continental blocks, such as the Blake Plateau , Grand Banks , or Bahama Islands offshore eastern Florida. A fourth way to classify passive margins is according to the nature of sedimentation of the mature passive margin. Sedimentation continues throughout the life of a passive margin. Sedimentation changes rapidly and progressively during the initial stages of passive margin formation because rifting begins on land, becoming marine as

1420-500: Is found on the south-facing coast of west Africa. Sheared margins are highly complex and tend to be rather narrow. They also differ from rifted passive margins in structural style and thermal evolution during continental breakup. As the seafloor spreading axis moves along the margin, thermal uplift produces a ridge. This ridge traps sediments, thus allowing for thick sequences to accumulate. These types of passive margins are less volcanic. This type of passive margin develops where rifting

1491-488: Is known as transitional lithosphere. The lithosphere thins seaward as it transitions seaward to oceanic crust. Different kinds of transitional crust form, depending on how fast rifting occurs and how hot the underlying mantle was at the time of rifting. Volcanic passive margins represent one endmember transitional crust type, the other endmember (amagmatic) type is the rifted passive margin. Volcanic passive margins also are marked by numerous dykes and igneous intrusions within

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1562-591: Is large enough and long-lived enough to create a sedimentary basin often called a pull-apart basin or strike-slip basin. These basins are often roughly rhombohedral in shape and may be called a rhombochasm . A classic rhombochasm is illustrated by the Dead Sea rift, where northward movement of the Arabian Plate relative to the Anatolian Plate has created a strike slip basin. The opposite effect

1633-709: Is not marked by a strike-slip fault or a subduction zone . Passive margins define the region around the Arctic Ocean , Atlantic Ocean , and western Indian Ocean , and define the entire coasts of Africa , Australia , Greenland , and the Indian Subcontinent . They are also found on the east coast of North America and South America , in Western Europe and most of Antarctica . Northeast Asia also contains some passive margins. The distinction between active and passive margins refers to whether

1704-521: Is oblique to the coastline, as is now occurring in the Gulf of California . Transitional crust, separating true oceanic and continental crusts, is the foundation of any passive margin. This forms during the rifting stage and consists of two endmembers: volcanic and non-volcanic. This classification scheme only applies to rifted and transtensional margin; transitional crust of sheared margins is very poorly known. Non-volcanic margins are formed when extension

1775-553: Is occurring can create a nascent ocean basin leading to either an ocean or the failure of the rift zone . Another expression of lithospheric stretching results in the formation of ocean basins with central ridges. The Red Sea is in fact an incipient ocean, in a plate tectonic context. The mouth of the Red Sea is also a tectonic triple junction where the Indian Ocean Ridge, Red Sea Rift and East African Rift meet. This

1846-458: Is particularly measurable and observable with oceanic crust, as there is a well-established correlation between the age of the underlying crust and depth of the ocean . As newly-formed oceanic crust cools over a period of tens of millions of years. This is an important contribution to subsidence in rift basins, backarc basins and passive margins where they are underlain by newly-formed oceanic crust. In strike-slip tectonic settings, deformation of

1917-553: Is that of transpression , where converging movement of a curved fault plane causes collision of the opposing sides of the fault. An example is the San Bernardino Mountains north of Los Angeles, which result from convergence along a curve in the San Andreas Fault system. The Northridge earthquake was caused by vertical movement along local thrust and reverse faults "bunching up" against the bend in

1988-416: Is the only place on the planet where such a triple junction in oceanic crust is exposed subaerially . This is due to a high thermal buoyancy ( thermal subsidence ) of the junction, and also to a local crumpled zone of seafloor crust acting as a dam against the Red Sea. Lithospheric flexure is another geodynamic mechanism that can cause regional subsidence resulting in the creation of a sedimentary basin. If

2059-466: Is thus an important area of study for purely scientific and academic reasons. There are however important economic incentives as well for understanding the processes of sedimentary basin formation and evolution because almost all of the world's fossil fuel reserves were formed in sedimentary basins. All of these perspectives on the history of a particular region are based on the study of a large three-dimensional body of sedimentary rocks that resulted from

2130-699: The Australian Southern Rift System . The basin dates from the late Jurassic to late Cretaceous periods and formed by multi-stage rifting during the breakup of Gondwana and the separation of the Antarctic and Australian plates. The basin contains a significant amount of natural gas and is a current source of commercial extraction. The Otway Basin developed along the Australian Southern Rift System during late Jurassic to Cenozoic breakup of eastern Gondwana as Antarctica began rifting away from Australia . The basin lies at

2201-571: The Campanian produced ~5000 meters of deltaic and marine Sherbrook Group sediments. In the late Cretaceous rifting transitioned to seafloor spreading marking the onset of post-rift passive margin conditions within the Otway Basin. As Australian - Antarctic plate clearance continued and the passive margin developed further the basin experienced widespread thermal subsidence leading to an increase in accommodation space. Deposition from

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2272-642: The Crayfish Group. In the Aptian the basin experienced widespread thermal subsidence where ~4000 meters of fluvial and lacustrine sediments of the Eumeralla Formation were deposited in the progressively widening sag basin. The first phase of rifting ceased in the Albian at which time the basin underwent an erosive compressional period leading to the basin wide Otway unconformity . After

2343-618: The Pacific Ocean margin are examples of active margins. While a weld between oceanic and continental lithosphere is called a passive margin, it is not an inactive margin. Active subsidence, sedimentation, growth faulting, pore fluid formation and migration are all active processes on passive margins. Passive margins are only passive in that they are not active plate boundaries. Passive margins consist of both onshore coastal plain and offshore continental shelf -slope-rise triads. Coastal plains are often dominated by fluvial processes, while

2414-485: The transport and deposition of sand, silt, and clay by rivers via deltas and redistribution of these sediments by longshore currents . The nature of sediments can change remarkably along a passive margin, due to interactions between carbonate sediment production, clastic input from rivers, and alongshore transport. Where clastic sediment inputs are small, biogenic sedimentation can dominate especially nearshore sedimentation. The Gulf of Mexico passive margin along

2485-482: The associated accretionary prism as it grows and changes shape creating ponded basins. Pull-apart basins is are created along major strike-slip faults where a bend in the fault geometry or the splitting of the fault into two or more faults creates tensional forces that cause crustal thinning or stretching due to extension, creating a regional depression. Frequently, the basins are rhombic, S-like or Z-like in shape. A broad comparatively shallow basin formed far from

2556-425: The continental domain, there are still open discussion on their real nature, chronology, geodynamic and petroleum implications. Examples of volcanic margins: Examples of non-volcanic margins: Passive margins of this type show a simple progression through the transitional crust, from normal continental to normal oceanic crusts. The passive margin offshore Texas is a good example. This type of transitional crust

2627-422: The continental shelf is dominated by deltaic and longshore current processes. The great rivers ( Amazon , Orinoco , Congo , Nile , Ganges , Yellow , Yangtze , and Mackenzie rivers) drain across passive margins. Extensive estuaries are common on mature passive margins. Although there are many kinds of passive margins, the morphologies of most passive margins are remarkably similar. Typically they consist of

2698-463: The density of the lithosphere and elevates the lower crust and lithosphere. In addition, mantle plumes may heat the lithosphere and cause prodigious igneous activity. Once a mid-oceanic ridge forms and seafloor spreading begins, the original site of rifting is separated into conjugate passive margins (for example, the eastern US and NW African margins were parts of the same rift in early Mesozoic time and are now conjugate margins) and migrates away from

2769-401: The earth's surface over time. Regional study of these rocks can be used as the primary record for different kinds of scientific investigation aimed at understanding and reconstructing the earth's past plate tectonics (paleotectonics), geography ( paleogeography , climate ( paleoclimatology ), oceans ( paleoceanography ), habitats ( paleoecology and paleobiogeography ). Sedimentary basin analysis

2840-425: The edge of a continental craton as a result of prolonged, broadly distributed but slow subsidence of the continental lithosphere relative to the surrounding area. They are sometimes referred to as intracratonic sag basins. They tend to be subcircular in shape and are commonly filled with shallow water marine or terrestrial sedimentary rocks that remain flat-lying and relatively undeformed over long periods of time due to

2911-439: The effect is believed to be twofold. The lower, hotter part of the lithosphere will "flow" slowly away from the main area being stretched, whilst the upper, cooler and more brittle crust will tend to fault (crack) and fracture. The combined effect of these two mechanisms is for Earth's surface in the area of extension to subside, creating a geographical depression which is then often infilled with water and/or sediments. (An analogy

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2982-427: The external characters. Beneath passive margins the transition between the continental and oceanic crust is a broad transition known as transitional crust. The subsided continental crust is marked by normal faults that dip seaward. The faulted crust transitions into oceanic crust and may be deeply buried due to thermal subsidence and the mass of sediment that collects above it. The lithosphere beneath passive margins

3053-405: The fill of one or more sedimentary basins over time. The scientific studies of stratigraphy and in recent decades sequence stratigraphy are focused on understanding the three-dimensional architecture, packaging and layering of this body of sedimentary rocks as a record resulting from sedimentary processes acting over time, influenced by global sea level change and regional plate tectonics. Where

3124-480: The formation of passive margins: Passive margins are important exploration targets for petroleum . Mann et al. (2001) classified 592 giant oil fields into six basin and tectonic-setting categories, and noted that continental passive margins account for 31% of giants. Continental rifts (which are likely to evolve into passive margins with time) contain another 30% of the world's giant oil fields. Basins associated with collision zones and subduction zones are where most of

3195-448: The initial stage, the continental crust and lithosphere is stretched and thinned due to plate movement ( plate tectonics ) and associated igneous activity. The very thin lithosphere beneath the rift allows the upwelling mantle to melt by decompression. Lithospheric thinning also allows the asthenosphere to rise closer to the surface, heating the overlying lithosphere by conduction and advection of heat by intrusive dykes. Heating reduces

3266-614: The late Maastrichtian to present day is marked by a succession of marine and carbonate accumulations of the Wangerrip, Nirranda, Heytesbury, and Whalers Bluff Groups, separated by distinct unconformities associated with basin-wide compression events. Sedimentary basin Sedimentary basins are region-scale depressions of the Earth's crust where subsidence has occurred and a thick sequence of sediments have accumulated to form

3337-425: The lithosphere occurs primarily in the plane of Earth as a result of near horizontal maximum and minimum principal stresses . Faults associated with these plate boundaries are primarily vertical. Wherever these vertical fault planes encounter bends, movement along the fault can create local areas of compression or tension. When the curve in the fault plane moves apart, a region of transtension occurs and sometimes

3408-405: The lithosphere. Plate tectonic processes that can create sufficient loads on the lithosphere to induce basin-forming processes include: After any kind of sedimentary basin has begun to form, the load created by the water and sediments filling the basin creates additional load, thus causing additional lithospheric flexure and amplifying the original subsidence that created the basin, regardless of

3479-478: The long-lived tectonic stability of the underlying craton. The geodynamic forces that create them remain poorly understood. Sedimentary basins form as a result of regional subsidence of the lithosphere, mostly as a result of a few geodynamic processes. If the lithosphere is caused to stretch horizontally, by mechanisms such as rifting (which is associated with divergent plate boundaries) or ridge-push or trench-pull (associated with convergent boundaries),

3550-412: The maximum Neogene lowstand, defined by the glacial maxima. The outer continental shelf and slope may be cut by great submarine canyons , which mark the offshore continuation of rivers. At high latitudes and during glaciations, the nearshore morphology of passive margins may reflect glacial processes, such as the fjords of Greenland and Norway . The main features of passive margins lie underneath

3621-583: The mid- and off-shore. Following each rifting episode the basin underwent compressional phases resulting in the inversion and wrenching of pre-existing structures. Eight distinct and regionally mappable stratigraphic groups define the Otway Basin fill. Basin rift system initiated at the onset of north-south extension between the Australian and Antarctic plates in the late Jurassic . Growing extensional structures were filled with ~5000 meters of continental and fluvio-lacustrine sediments that comprise

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3692-471: The original cause of basin inception. Cooling of a lithospheric plate, particularly young oceanic crust or recently stretched continental crust, causes thermal subsidence . As the plate cools it shrinks and becomes denser through thermal contraction . Analogous to a solid floating in a liquid, as the lithospheric plate gets denser it sinks because it displaces more of the underlying mantle through an equilibrium process known as isostasy . Thermal subsidence

3763-413: The otherwise strike-slip fault environment. The study of sedimentary basins as entities unto themselves is often referred to as sedimentary basin analysis . Study involving quantitative modeling of the dynamic geologic processes by which they evolved is called basin modelling . The sedimentary rocks comprising the fill of sedimentary basins hold the most complete historical record of the evolution of

3834-466: The presence of salt domes , as are common along the Texas and Louisiana passive margin. Sediment-starved margins produce narrow continental shelves and passive margins. This is especially common in arid regions, where there is little transport of sediment by rivers or redistribution by longshore currents. The Red Sea is a good example of a sediment-starved passive margin. There are three main stages in

3905-464: The processes of compaction and lithification that transform them into sedimentary rock . Sedimentary basins are created by deformation of Earth's lithosphere in diverse geological settings, usually as a result of plate tectonic activity. Mechanisms of crustal deformation that lead to subsidence and sedimentary basin formation include the thinning of underlying crust; depression of the crust by sedimentary, tectonic or volcanic loading; or changes in

3976-483: The relationship between rift orientation and plate motion, the second describes the nature of transitional crust, and the third describes post-rift sedimentation. All three perspectives need to be considered in describing a passive margin. In fact, passive margins are extremely long, and vary along their length in rift geometry, nature of transitional crust, and sediment supply; it is more appropriate to subdivide individual passive margins into segments on this basis and apply

4047-428: The remaining giant oil fields are found. Passive margins are petroleum storehouses because these are associated with favorable conditions for accumulation and maturation of organic matter. Early continental rifting conditions led to the development of anoxic basins, large sediment and organic flux, and the preservation of organic matter that led to oil and gas deposits. Crude oil will form from these deposits. These are

4118-405: The rift opens and a true passive margin is established. Consequently, the sedimentation history of a passive margin begins with fluvial, lacustrine, or other subaerial deposits, evolving with time depending on how the rifting occurred and how, when, and by what type of sediment it varies. Constructional margins are the "classic" mode of passive margin sedimentation. Normal sedimentation results from

4189-429: The rocks directly and also very importantly allow paleontologists to study the microfossils they contain ( micropaleontology ). At the time they are being drilled, boreholes are also surveyed by pulling electronic instruments along the length of the borehole in a process known as well logging . Well logging, which is sometimes appropriately called borehole geophysics , uses electromagnetic and radioactive properties of

4260-574: The rocks surrounding the borehole, as well as their interaction with the fluids used in the process of drilling the borehole, to create a continuous record of the rocks along the length of the borehole, displayed as of a family of curves. Comparison of well log curves between multiple boreholes can be used to understand the stratigraphy of a sedimentary basin, particularly if used in conjunction with seismic stratigraphy. Passive margin Passive margins are found at every ocean and continent boundary that

4331-486: The sedimentary rocks comprising a sedimentary basin's fill are exposed at the earth's surface, traditional field geology and aerial photography techniques as well as satellite imagery can be used in the study of sedimentary basins. Much of a sedimentary basin's fill often remains buried below the surface, often submerged in the ocean, and thus cannot be studied directly. Acoustic imaging using seismic reflection acquired through seismic data acquisition and studied through

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4402-410: The shelf edge and its migration through time is critical to the development of a passive margin. The location of the shelf edge break reflects complex interaction between sedimentation, sealevel, and the presence of sediment dams. Coral reefs serve as bulwarks that allow sediment to accumulate between them and the shore, cutting off sediment supply to deeper water. Another type of sediment dam results from

4473-523: The southern United States is an excellent example of this, with muddy and sandy coastal environments down current (west) from the Mississippi River Delta and beaches of carbonate sand to the east. The thick layers of sediment gradually thin with increasing distance offshore, depending on subsidence of the passive margin and the efficacy of offshore transport mechanisms such as turbidity currents and submarine channels . Development of

4544-400: The specific sub-discipline of seismic stratigraphy is the primary means of understanding the three-dimensional architecture of the basin's fill through remote sensing . Direct sampling of the rocks themselves is accomplished via the drilling of boreholes and the retrieval of rock samples in the form of both core samples and drill cuttings . These allow geologists to study small samples of

4615-432: The subsided continental crust. There are typically a lot of dykes formed perpendicular to the seaward-dipping lava flows and sills. Igneous intrusions within the crust cause lava flows along the top of the subsided continental crust and form seaward-dipping reflectors. Passive margins are characterized by thick accumulations of sediments. Space for these sediments is called accommodation and is due to subsidence of especially

4686-464: The thickness or density of underlying or adjacent lithosphere . Once the process of basin formation has begun, the weight of the sediments being deposited in the basin adds a further load on the underlying crust that accentuates subsidence and thus amplifies basin development as a result of isostasy . The long-term preserved geologic record of a sedimentary basin is a large scale contiguous three-dimensional package of sedimentary rocks created during

4757-566: The threefold classification to each segment. This is the typical way that passive margins form, as separated continental tracts move perpendicular to the coastline. This is how the Central Atlantic opened, beginning in Jurassic time. Faulting tends to be listric : normal faults that flatten with depth. Sheared margins form where continental breakup was associated with strike-slip faulting . A good example of this type of margin

4828-626: The transition from a normal-obliquely rifted continental margin to the west to a transform continental margin to the southeast. This transition zone is dominated by transtensional faulting that contributes to the basin's complex structural and depositional history. The margin developed through repeated episodes of extension and thermal subsidence leading up to, and following, the commencement of seafloor spreading between Australian and Antarctica . The basin includes five significant depocenters . The Inner Otway Basin, Torquay Sub-basin, Morum Sub-basin, Nelson Sub-basin, and Hunter Sub-basin formed as

4899-432: The transitional crust. Subsidence is ultimately caused by gravitational equilibrium that is established between the crustal tracts, known as isostasy . Isostasy controls the uplift of the rift flank and the subsequent subsidence of the evolving passive margin and is mostly reflected by changes in heat flow . Heat flow at passive margins changes significantly over its lifespan, high at the beginning and decreasing with age. In

4970-546: The world's natural gas and petroleum and all of its coal are found in sedimentary rock. Many metal ores are found in sedimentary rocks formed in particular sedimentary environments. Sedimentary basins are also important from a purely scientific perspective because their sedimentary fill provides a record of Earth's history during the time in which the basin was actively receiving sediment. More than six hundred sedimentary basins have been identified worldwide. They range in areal size from tens of square kilometers to well over

5041-435: The zone of mantle upwelling and heating and cooling begins. The mantle lithosphere below the thinned and faulted continental oceanic transition cools, thickens, increases in density and thus begins to subside. The accumulation of sediments above the subsiding transitional crust and lithosphere further depresses the transitional crust. There are four different perspectives needed to classify passive margins: The first describes

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