Добірка наукової літератури з теми "Tookoonooka"

This paper examines proven, probable, possible and speculative impact structures in Australian Phanerozoic strata and their petroleum potential. There are two classes of crater: simple and complex. The former usually assumes a bowl shaped depression with a raised and overturned rim with a diameter rarely more than three kilometres, with complex structures generally occurring above diameters of two kilometres in sedimentary rocks and four kilometres in crystalline rocks. Complex craters are characterised by a central uplifted area and a classic 'sombrero' structure and can be very large and have diameters of over 800 km. Criteria for the identification of terrestrial impact structures include: (a) circular plan; (b) faulted rim structure; (c) flat floor with central uplift (may not always be present) or interior ring(s); (d) negative gravity anomaly; (e) magnetic low with subdued magnetic relief; (f) brecciated crater fill; (g) low seismic velocities in the crater fill; (h) shock metamorphism (coesite, multiple sets of planar shock lamellae in quartz grains, shatter cones); (i) meteoric material; (j) presence of melt rock; (k) distal ejecta; and occurrence of an annular trough between the central uplift and the outer faulted rim.Proven impact features, like Gosses Bluff and Mt Toondina, are well exposed, contain indisputable evidence of shock metamorphism, and have had extensive geophysical surveys conducted over them: these structures provide models to interpret completely buried structures. Subsurface impact structures have been detected in areas where there has been intensive seismic surveying in the search for hydrocarbons. The Tookoonooka, Talundilly and Mulkarra structures all occur in the Cooper-Eromanga Basin, an area of high intensity exploration. The best known wholly subsurface impact feature is the 66 km diameter Tookoonooka Structure in southwestern Queensland, which exhibits several of the accepted criteria for an impact origin, including shock metamorphism, and is classified as a probable complex type impact structure. The Talundilly Structure, a possible impact feature, lies 300 km to the northeast of the Tookoonooka Structure and is of the same general age. The two structures could reflect the impact of fragments of the same bolide. The Yallallie Structure lies in a moderately explored hydrocarbon province in the central Perth Basin. It has a classic 'sombrero' shape in section view with a central uplift and evidence of shock metamorphism. Yallallie is a probable complex impact structure. The Mulkarra Structure, located in northeastern South Australia, has been classified as a simple type of impact crater lacking a central uplift, but recent geophysical work indicates a probable complex impact origin. Other possible and speculative impact related features described here owe their recognition to good quality seismic surveying.'there are yet some geologists who, adhering to Lyellian dogma, devoutly refuse to accept that large objects fall out of the sky.' (Shoemaker, 1997).

Tookoonooka and Talundilly are two large meteorite impact structures buried in the sedimentary rocks of central Australia, and are among the largest impact structures known on Earth. They are shown to be a rare example of an ancient marine impact event and are also an extremely rare terrestrial example of a probable binary impact event. A preserved marine impact ejecta horizon, interpreted to span a vast area of the continent and corresponding to the extent of a Cretaceous epicontinental sea, is used to biostratigraphically constrain the impact age to the Barremian-Aptian boundary (125 +/- 1 Ma) in the Lower Cretaceous. Evidence is presented that the Wyandra Sandstone Member petroleum reservoir overlying the horizon is, in part, a binary impact tsunamiite. Analyses of drill core, subsurface drilling data, and geological outcrops over >805,000 km² show that the base of the Wyandra Sandstone Member is an impact horizon: a widespread scour surface that is attributed to impact-related excavation and tsunami scour mechanisms. The impact horizon is underlain by seismites and overlain by very poorly sorted sediment with highly polymictic exotic clasts, imbricated pebbles, and intraformational cobble rip-up clasts. Exotic clasts are predominantly interpreted as impactoclasts, and include complex accretionary and armoured impactoclasts of vapour plume origin, shock-metamorphosed lithic fragments, and altered melt impactoclasts. Some lithic fragments resemble basement lithologies from the Tookoonooka and Talundilly target rock sequences. The stratigraphy of the Wyandra Sandstone Member contains elements characteristic of impact tsunami deposition including ejecta entrained in high flow regime bedforms, pebble to boulder-sized clasts, >16m thick beds, and cyclic sedimentation of tsunami couplets, across five depositional realms. These elements are in stark contrast to the persistently low-energy nature of the ambient sedimentation and overlying quiescent marine shales, but are consistent with the intense seismicity, high energy seiche action and rapid deposition expected from a marine impact in a mostly enclosed basin. A dual impact source is indicated, based on sediment distribution patterns in combination with the proximity of the impact structures in age and location. The Wyandra Sandstone Member records both marine impact depositional processes as well as the waning of the event; the upper part of the Wyandra returns to background depositional energies and intense bioturbation and is conformably overlain by transgressive marine shales. The Tookoonooka-Talundilly impact event may be an extreme prototype, as very few doublet craters, marine craters, impact tsunamiites, or economic impactites are individually known or preserved on Earth, yet this crater pair may represent all four. This impact crater pair provides a model for binary marine impact sedimentation and highlights the significance of ancient impact sediments to petroleum basins. Sedimentation patterns evidence a dual crater source even in a marine impact scenario where reworking and burial complicate the interpretation of depositional indicators; observations suggest that Tookoonooka-Talundilly may be the largest doublet crater discovered on Earth.
Thesis (Ph.D.) (Research by Publication) -- University of Adelaide, Australian School of Petroleum, 2015.