The Murray Basin is a Cenozoic sedimentary basin in south eastern Australia. The basin is only shallow, but extends into New South Wales, Victoria and South Australia. It takes its name from the Murray River which traverses the Basin from east to west.
One theory for the formation of the basin is that it is dynamic topography due to a sinking slab of oceanic crust. This slab was subducted during latest Cretaceous and Early Cenozoic periods to the north of the Australian continent underneath New Guinea. The slab broke off and was gradually overridden by the Australian plate moving north. The sinking slab has a trace in the P-wave velocity in the mantle which is higher from 800 to 1200 km deep below the Murray basin, and also the Lake Eyre Basin. The velocity anomaly is oriented northwest-southeast and extends from 135°E 26°S to 144°E35°S. The sinking has dragged down the rock above it to make a hollow which is the basin. This hollow has moved south over the last 50 million years. If this theory is correct, then the Murray basin will move south over the next tens of millions of years and disappear under the Southern Ocean. [1] Modelling using the Underworld program by Moresi indicates that the slab would be sinking at 8.5 mm per year and cause a depression on the surface 200 m deep around 2500 km wide. In the past the basin depression was narrower but deeper in this model. [1]
After Australia separated from Antarctica, the Murray Basin was formed. The basin floor only subsided slowly over time. [2] The basin became filled with up to 600 metres (1,970 ft) of sediments during the Cenozoic Era. [3]
From Paleocene to the Eocene Epoch, the western side was flooded with seawater and deposited the Warina sand. [4] The sea withdrew, and later in the Eocene, silt and clay of the Olney Formation [5] were deposited. One minor sea incursion in the Late Eocene resulted in the Buccleuch Formation [6] in South Australia. The group of deposits is termed the Renmark Group and was earlier known as the Knight Group. [7]
The sea level rose again in Late Oligocene to mid Miocene, forming the Murray Group of sediments, with marl and limestone in the deeper locations, and the Geera Clay [8] in the shallow waters. The rock units formed in the deeper water included the Ettric Formation (see cross-section image), [9] the Winnanbool Formation [10] and the Mannum Formation limestone [11] with Gambier Limestone in South Australia. [12] [13] When the sea level fell again in mid-Miocene, the deposited Geera clay and Olney Formation moved westward over the limestone. [2]
During Upper Miocene to Pliocene, the sea rose and fell several times. The first sea rise formed the Murravian Gulf and resulted in clay and marl in the west, called the Bookpurnong Formation, [14] with the Calivil Formation [15] river and lake sand in the east. When the sea retreated in Early Pliocene, the Loxton Sands, [16] also informally known as Loxton-Parilla Sands, were formed on the beach on the shore of the emergent land. Locally heavy minerals have been concentrated by wave action, including rutile zircon and ilmenite, forming economic mining opportunities. [17]
The Murray River became dammed by uplift of over 250 metres (820 ft) in the Grampians in Victoria during the Pleistocene about 2.5 Mya. The dam formed Lake Bungunnia, which reached 40,000 square kilometres (15,000 sq mi) and deposited the Blanchetown Clay therein. [18] Higher rainfall of at least 500 millimetres (20 inches) per year kept the lake filled at first, but during later times, rainfall was insufficient, and saline lakes formed, depositing dolomite. Even today, some saline lakes remain as a remnant of the vast lake. [19] The Murray River carved out a new path to the sea via Murray Bridge, replacing its previous exit at Portland, Victoria. The lake was gone by about 0.7 Mya.
The Pooraka Formation [20] formed in the north west due to increased erosion, resulting in colluvium depositing. The colluvium forms fans, cones and scree slopes, and often contains clay and breccia. In the flat areas, the Shepparton Formation [21] also resulted from river deposits of floodplain clay. [2]
Most of the existing surface dates from Quaternary period. The river deposits from the east have been progressively overlaying the marine deposits further west, as the shore line receded. Within the Pleistocene deposits are three layers of sand that are aquifers, deposited during higher rainfall periods of the interglacials. The floodplain deposits from the current rivers are the Coonambidgal Formation, however this term is used informally for the older Pleistocene flood deposits as well. [22] During the dryer glacial periods the area was arid. [23]
Coquina is a sedimentary rock that is composed either wholly or almost entirely of the transported, abraded, and mechanically sorted fragments of the shells of mollusks, trilobites, brachiopods, or other invertebrates. The term coquina comes from the Spanish word for "cockle" and "shellfish".
Dorset is a county in South West England on the English Channel coast. Covering an area of 2,653 square kilometres (1,024 sq mi); it borders Devon to the west, Somerset to the north-west, Wiltshire to the north-east, and Hampshire to the east. The great variation in its landscape owes much to the underlying geology, which includes an almost unbroken sequence of rocks from 200 to 40 million years ago (Mya) and superficial deposits from 2 Mya to the present. In general, the oldest rocks appear in the far west of the county, with the most recent (Eocene) in the far east. Jurassic rocks also underlie the Blackmore Vale and comprise much of the coastal cliff in the west and south of the county; although younger Cretaceous rocks crown some of the highpoints in the west, they are mainly to be found in the centre and east of the county.
The Sydney Basin is an interim Australian bioregion and is both a structural entity and a depositional area, now preserved on the east coast of New South Wales, Australia and with some of its eastern side now subsided beneath the Tasman Sea. The basin is named for the city of Sydney, on which it is centred.
The Bluesky Formation is a stratigraphic unit of Lower Cretaceous age in the Western Canada Sedimentary Basin. It takes the name from the hamlet of Bluesky, and was first described in Shell's Bluesky No. 1 well by Badgley in 1952.
The Hanau-Seligenstadt Basin is a subbasin of the Upper Rhine Graben southeast of Frankfurt am Main.
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The Clarence Moreton Basin is a Mesozoic sedimentary basin on the easternmost part of the Australian continent. It is located in the far north east of the state of New South Wales around Lismore and Grafton and in the south east corner of Queensland. It is the part of the Great Artesian Basin that extends to the east coast in Australia's central eastern lowlands.
The Norwich Crag Formation is a stratigraphic unit of the British Pleistocene Epoch. It is the second youngest unit of the Crag Group, a sequence of four geological formations spanning the Pliocene to Lower Pleistocene transition in East Anglia. It was deposited between approximately 2.4 and 1.8 million years ago, during the Gelasian Stage.
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The Crag Group is a geological group outcropping in East Anglia, UK and adjacent areas of the North Sea. Its age ranges from approximately 4.4 to 0.478 million years BP, spanning the late Pliocene and early to middle Pleistocene epochs. It comprises a range of marine and estuarine sands, gravels, silts and clays deposited in a relatively shallow-water, tidally-dominated marine embayment on the western margins of the North Sea basin. The sands are characteristically dark green from glauconite but weather bright orange, with haematite 'iron pans' forming. The lithology of the lower part of the Group is almost entirely flint. The highest formation in the Group, the Wroxham Crag, contains over 10% of far-travelled lithologies, notably quartzite and vein quartz from the Midlands, igneous rocks from Wales, and chert from the Upper Greensand of southeastern England. This exotic rock component was introduced by rivers such as the Bytham River and Proto-Thames.
The Columbus Basin is a foreland basin located off the south eastern coast of Trinidad within the East Venezuela Basin (EVB). Due to the intensive deformation occurring along the Caribbean and South American plates in this region, the basin has a unique structural and stratigraphic relationship. The Columbus Basin has been a prime area for hydrocarbon exploration and production as its structures, sediments and burial history provide ideal conditions for generation and storage of hydrocarbon reserves. The Columbus Basin serves as a depocenter for the Orinoco River delta, where it is infilled with 15 km of fluvio-deltaic sediment. The area has also been extensively deformed by series of north west to southeast normal faults and northeast to southwest trending anticline structures.
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The geology of South Dakota began to form more than 2.5 billion years ago in the Archean eon of the Precambrian. Igneous crystalline basement rock continued to emplace through the Proterozoic, interspersed with sediments and volcanic materials. Large limestone and shale deposits formed during the Paleozoic, during prevalent shallow marine conditions, followed by red beds during terrestrial conditions in the Triassic. The Western Interior Seaway flooded the region, creating vast shale, chalk and coal beds in the Cretaceous as the Laramide orogeny began to form the Rocky Mountains. The Black Hills were uplifted in the early Cenozoic, followed by long-running periods of erosion, sediment deposition and volcanic ash fall, forming the Badlands and storing marine and mammal fossils. Much of the state's landscape was reworked during several phases of glaciation in the Pleistocene. South Dakota has extensive mineral resources in the Black Hills and some oil and gas extraction in the Williston Basin. The Homestake Mine, active until 2002, was a major gold mine that reached up to 8000 feet underground and is now used for dark matter and neutrino research.
The geology of Kentucky formed beginning more than one billion years ago, in the Proterozoic eon of the Precambrian. The oldest igneous and metamorphic crystalline basement rock is part of the Grenville Province, a small continent that collided with the early North American continent. The beginning of the Paleozoic is poorly attested and the oldest rocks in Kentucky, outcropping at the surface, are from the Ordovician. Throughout the Paleozoic, shallow seas covered the area, depositing marine sedimentary rocks such as limestone, dolomite and shale, as well as large numbers of fossils. By the Mississippian and the Pennsylvanian, massive coal swamps formed and generated the two large coal fields and the oil and gas which have played an important role in the state's economy. With interludes of terrestrial conditions, shallow marine conditions persisted throughout the Mesozoic and well into the Cenozoic. Unlike neighboring states, Kentucky was not significantly impacted by the Pleistocene glaciations. The state has extensive natural resources, including coal, oil and gas, sand, clay, fluorspar, limestone, dolomite and gravel. Kentucky is unique as the first state to be fully geologically mapped.
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The geology of Kuwait includes extremely thick, oil and gas-bearing sedimentary sequences from the Mesozoic and Cenozoic. Kuwait is a country in Western Asia, situated in the northern edge of Eastern Arabia at the tip of the Persian Gulf.
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34°11′20″S142°09′30″E / 34.18889°S 142.15833°E Coordinates: 34°11′20″S142°09′30″E / 34.18889°S 142.15833°E