The Carnarvon Basin is a geological basin located in the north west of Western Australia which extends from the Dampier Archipelago to the Murchison bioregion, and is the main geological feature that makes up the North West Shelf . The onshore part of the Carnarvon Basin covers about 115,000 km and the offshore part covers approximately 535,000 km with water depths up to 3,500 metres. It is separated into two major areas - the Northern Carnarvon Basin, and the Southern Carnarvon Basin.
27-676: The Northern Carnarvon Basin includes the Exmouth Plateau , Wombat Plateau (on the northern part of the Exmouth Plateau), Investigator Sub-basin, Rankin Platform, Exmouth Sub-basin, Barrow Sub-basin, Dampier Sub-basin, Beagle Sub-basin, Enderby Terrace, Peedamullah Shelf and the Lambert Shelf. The main sub-basins for petroleum exploration in the basin have been Dampier, Exmouth and Barrow. The Southern basin consists of
54-581: A location in Western Australia is a stub . You can help Misplaced Pages by expanding it . This article about a specific Australian geological feature is a stub . You can help Misplaced Pages by expanding it . Exmouth Plateau The Exmouth Plateau is an elongate northeast striking extensional passive margin located in the Indian Ocean roughly 3,000 meters offshore from western and northwestern Western Australia . The plateau makes up
81-464: A system of listric normal faults near the eastern region of the Exmouth Plateau. These listric faults were a product from the development of a major low angle detachment fault between a sedimentary base of Permian-Triassic upper crust and the mid-crustal horizon. As a result, brittle deformation and crustal thinning in the upper crust of the eastern Exmouth Plateau occurred, while in the west,
108-584: Is a low-energy, offshore-marine deposit in a period when input of the terrigenous sediments to the offshore was low minimal. Norian The Norian is a division of the Triassic Period . It has the rank of an age ( geochronology ) or stage ( chronostratigraphy ). It lasted from ~227 to 208.5 million years ago . It was preceded by the Carnian and succeeded by the Rhaetian . The Norian
135-689: The Gascoyne, Merlinleigh, Bidgemia and Byro Sub-basins and Bernier Platform and is flanked to the east by the Archaean Pilbara Block. The Gnargoo structure , which has remarkable similarities to Woodleigh crater , is a proposed 75 km impact crater on the Gascoyne Platform, Southern Carnarvon Basin with an estimated age of 100-300 Ma. 24°48′24″S 115°13′29″E / 24.80667°S 115.22472°E / -24.80667; 115.22472 This article about
162-727: The Mungaroo laid down only for a short period of time between the beginning of the Rhaetian to the Early Hettangian . Due to the thickness of fluvial deltaic deposits from the Mungaroo Formation, the transgressional sequence of the Brigadier Formation is correlated with the subsidence of sub-basins across region during the Middle and Late Triassic . The distribution of sediment packages throughout
189-872: The Northern Carnarvon Basin and Exmouth Plateau varies with location during the Jurassic. By the Pliensbachian , the general beginning structure of the Northern Carnarvon Basin was formed, creating the Exmouth, Barrow, and Dampier sub-basins along the proximal end of the northwestern Australian margin. Rapid subsidence of the Northern Carnarvon sub-basins ensued the deposition of the Dingo Claystones. These Claystones are thick marine shale deposits separated into two sequence,
216-646: The Permian extension that occurred just prior to the late Triassic extension event across the northwestern margin of Australia. Lying atop unconformable unit of Paleozoic sediments, the Locker Shale is composed of marine sediments deposited in a transgressional environment during the Late Permian extension. These marine sediments were deposited at the base of the Late Triassic and continued up until
243-559: The Upper and Lower Dingo Claystones. The Lower Dingo sequence cannot be found in the Exmouth Plateau, because deposition During the Early to Middle Jurassic was restricted to sediments filling in the empty troughs of the Northern Carnarvon sub-basins. As deposition continued through the Middle and Late Jurassic , the troughs of sub-basins filled allowing more of the Dingo sediment overflow into
270-771: The Winning Group atop the Valanginian unconformity. The Winning Group consists of Muderong Shale, Windalia Radiolarite, and Gearle Siltstone. The Muderong Shale is actually considered a siltstone and was deposited in a low energy, offshore-marine environment. The deposition of these sediments makes a good seal for gas buildups in the Exmouth Plateau and the surrounding sub-basins of the Northern Carnvon Basin. The Windalia Radiolarite are primarily carbonate marine deposits commonly containing poorly preserved radiolarians and forminiferas. The Gearle Siltstone
297-616: The base (a GSSP ) had in 2009 not yet been appointed. The top of the Norian (the base of the Rhaetian) is at the first appearance of ammonite species Cochloceras amoenum . The base of the Rheatian is also close to the first appearance of conodont species Misikella spp. and Epigondolella mosheri and the radiolarid species Proparvicingula moniliformis . In the Tethys domain ,
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#1732772950790324-478: The central and southern margins of the Exmouth Plateau now known as the Gascoyne and Cuvier Abyssal Plains. As Australia continued to diverge away from the Antarctic land mass, it migrated in a northeastern direction and rotated counterclockwise to it present location, leaving the Exmouth Plateau along the continent's western margin. In the begin of the late Triassic , high volumes of sediments accumulate off of
351-458: The continental break up at the southern margin of the Exmouth Plateau. This followed seafloor spreading at the Gascoyne and Cuvier Abyssal Plains and erosion at the surface of the Exmouth, Dampier and Barrow sub-basins and an unconformity at the top of the early to middle Valanginian . By the middle to late Valanginian and through the Cretaceous major transgression occurred with deposit of
378-543: The distal margins of Exmouth Plateau. In the Late Jurassic , Gondwanaland begins to break apart creating Western Gondwana, which was composed of the South American and African continental land masses, and Eastern Gondwana. The Eastern Gondwanian continent was composed of Madagascar, Greater India, Antarctica, and Australia. During this period of time Australia shared its southern margin with Antarctica and
405-555: The distal margins of the region. This depositional sequence characterizes the Upper Dingo Claystones, which are found as thick proximal sequences in the Northern Carnarvon sub-basins and thinner distal sequences in the Exmouth Plateau. During the late Tithonian to early Valanginian there were major changes in depositional patterns, specifically associated with the Barrow Group. At this period of time there
432-426: The distal portions of the Northern Carnarvon Basin furthest offshore. One of the primary gas source for the Exmouth Plateau and Northern Carnarvon Basin, the Mungaroo Formation contains thick successions of siltstone , sandstone , and coal . The Mungaroo Formation is capped by thin transgressive sequence of shallow marine claystone and limestone called the Brigadier Formation. This is a much thinner formation than
459-572: The end of Anisian age when it transitioned in the Mungaroo Formation. The Mungaroo Formation is an intricate fluvial environment of meandering and braided stream deposits laid down in the Ladinian (~241 Mya) to Norian ages (~209 Mya) during the pre-rift active margin of the Northwestern Australian Shelf. It is one of the thickest formations in the region and becomes progressively thicker (approximately 3,000 m thick) in
486-521: The lower crystalline crust and lithosphere experienced shear stress and thinning. The formation of the fault system closer to the coast caused the initial development of the Exmouth, Barrow, and Dampier sub-basins of the Northern Carnarvon Basin. Carbonate marine sediment, primarily marls, continued to be deposited at this time on the central and western portions of the plateau. Closer to the shoreline siliciclastic mud and silt were deposited from marine and deltaic environments. As extension continued in
513-465: The mid to late Jurassic, multiple pull-apart basins and oblique right-lateral strike-slip faulting in the eastern margin of the Exmouth Plateau continued to dominate. The simple shear stress of the Exmouth detachment fault between the base of the upper crust, and the lower crust had been reduced in the east plateau. This reduction in simple shear was in part caused by the deformation that developed series negative flower structures and half-graben systems in
540-488: The overall structural morphology of the Exmouth Plateau had taken shape, aside from the post-breakup subsidence that occurred afterward from the Late Cretaceous to present day. Activity at the eastern Exmouth Plateau's detachment system had likely ceased which is reason for the completion of the plateau's morphology. The Locker Shale and Mungaroo formation are associated with the syn-rift and post-rift sequences of
567-543: The shoreline of western Australia to the northern extend of the Exmouth Plateau by the Mungaroo Deltas. The Carnian (237-228 Ma) to Norian (228-209 Ma) aged fluviodeltaic sediments deposited were siliciclastic claystones and sandstones, and detritus which would late make up the coals found in Mungaroo Formation. As extensional rifting between Greater Indian and the Australian continued, magmatic intrusion along
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#1732772950790594-434: The west plateau. By this time, the lithospheric thinning that had been initiated during the early Jurassic was now considerably thinner. At this period, a magmatic intrusion between the lower crystalline crest and the lithosphere been introduce, underplating this region. In Early Cretaceous , pure shear deformation at the ocean-continental boundary completed the final continental breakup and sea-floor spreading. By this time
621-625: The western margin (now the Exmouth Plateau) with Greater India. The formation of the Exmouth's northern margin, the Argo Abyssal Plain, was not initiated until 155 million years ago when Australia broke apart from a continental fragment of the Burma Plate that's present location is argued to be subsumed under Asia. It wasn't until 20 million years later that the Greater Indian land mass broke from western Australia, forming
648-528: The westernmost section of the Exmouth Plateau caused further rifting to the outer margins. By the end of the Late Triassic (209-201 Ma) tectonic activity had relatively slowed down and less deltaic sediments were deposited compared to the Carnian and Norian . More marine sedimentary deposit such as carbonates are found during this time period. During the early Jurassic, extension at the west Australian margin initiated simple shear mechanics creating
675-608: The westernmost structural unit of the Northern Carnarvon Basin , which comprises the Exmouth, Barrow, Dampier, and Beagle Sub-basins, and the Rankin Platform. The Exmouth Plateau was once a part of the northern shore of eastern of Gondwanaland until it broke away during Late Jurassic to Early Cretaceous , leaving behind the oceanic crust of the Argo, Cuvier, and Gascoyne abyssal plains that now surround
702-576: Was large uplift of the Cape Range Fracture Zone that provided sediments from the Barrow Delta prograde northward past Barrow Island and across the Exmouth Plateau. The sediments of the Barrow Group are composed of interbedded shale and fluvial-deltiac sands that were extensively deposited into Exmouth and Barrow sub-basins. Eventually, deposition of the Barrow Delta's sediment ceased during the early or middle Valanginian due to
729-544: Was named after the Noric Alps in Austria . The stage was introduced into scientific literature by Austrian geologist Edmund Mojsisovics von Mojsvar in 1869. The Norian Stage begins at the base of the ammonite biozones of Klamathites macrolobatus and Stikinoceras kerri , and at the base of the conodont biozones of Metapolygnathus communisti and Metapolygnathus primitius . A global reference profile for
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