The middle-upper Cretaceous Ceduna River system traversed continental Australia from the NE coast to the centre of the southern coast. At its mouth, it formed a vast delta system that is similar in scale to the Niger ...The middle-upper Cretaceous Ceduna River system traversed continental Australia from the NE coast to the centre of the southern coast. At its mouth, it formed a vast delta system that is similar in scale to the Niger delta of West Africa. The delta system is composed of two main lobes that represent different phases of delta construction. A recent hypothesis has challenged the traditional idea that both lobes of the delta were derived from a transcontinental river system by suggesting that the upper lobe （Santonian -Maastrichtian） is instead derived from a restricted catchment within southern Australia. Hf isotopic data presented here fingerprint the original source of the upper delta lobe zircons to NE Australia, with data comparing well with similar U-Pb and Lu-Hf isotopic data from the Lachlan Orogen, the New England Orogen, the eastern Musgraves Province and the northern Flinders Ranges. These data do not preclude a model where the lobe is derived from recycled Eromanga Basin sediments during a phase of late Cretaceous inland Australian uplift, but when coupled with reconnaissance low-temperature thermochronometry from the region of the Ceduna River course indicating widespread Triassic-Jurassic exhumation, and comparisons with detrital zircon data from the Winton Formation upstream of any proposed uplift, we suggest that both lobes of the Ceduna Delta are likely to be derived from a transcontinental Ceduna River.展开更多
Apatite U-Pb thermochronology was applied to granitoid basement samples across the northern Gawler Craton to unravel the Proterozoic, post-orogenic, cooling history and to examine the role of major fault zones during ...Apatite U-Pb thermochronology was applied to granitoid basement samples across the northern Gawler Craton to unravel the Proterozoic, post-orogenic, cooling history and to examine the role of major fault zones during cooling. Our observations indicate that cooling following the ~2500 Ma Sleaford Orogeny and ~1700 Ma Kimban Orogeny is restricted to the Christie and Wilgena Domains of the central northern Gawler Craton. The northern Gawler Craton mainly records post-Hiltaba Event(~1590 Ma) U-Pb cooling ages. Cooling following the ~1560 Ma Kararan Orogeny is preserved within the Coober Pedy Ridge,Nawa Domain and along major shear zones within the south-western Fowler Domain. The Nawa Domain samples preserve U-Pb cooling ages that are >150 Ma younger than the samples within the Coober Pedy Ridge and Fowler Domain, indicating that later(~1300 Ma) fault movement within the Nawa Domain facilitated cooling of these samples, caused by arc collision in the Madura Province of eastern Western Australia. When compared to^(40)Ar/^(39) Ar from muscovite, biotite and hornblende, our new apatite U-Pb ages correlate well, particularly in regions of higher data density. Our data also preserve a progressive younging of U-Pb ages from the nucleus of the craton to the periphery with a stark contrast in U-Pb ages across major structures such as the Karari Shear Zone and the Southern Overthrust, which indicates the timing of reactivation of these major crustal structures. Although this interpolation was based solely on thermochronological data and did not take into account structural or other geological data, these maps are consistent with the structural architecture of the Gawler Craton and reveal the thermal footprint of known tectonic and magmatic events in the Gawler Craton.展开更多
基金part of an Honours project at University of Adelaide,in part funded by the Geological Survey of South AustraliaARC Future Fellowship grant FT120100340IGCP projects #628 and #648
文摘The middle-upper Cretaceous Ceduna River system traversed continental Australia from the NE coast to the centre of the southern coast. At its mouth, it formed a vast delta system that is similar in scale to the Niger delta of West Africa. The delta system is composed of two main lobes that represent different phases of delta construction. A recent hypothesis has challenged the traditional idea that both lobes of the delta were derived from a transcontinental river system by suggesting that the upper lobe （Santonian -Maastrichtian） is instead derived from a restricted catchment within southern Australia. Hf isotopic data presented here fingerprint the original source of the upper delta lobe zircons to NE Australia, with data comparing well with similar U-Pb and Lu-Hf isotopic data from the Lachlan Orogen, the New England Orogen, the eastern Musgraves Province and the northern Flinders Ranges. These data do not preclude a model where the lobe is derived from recycled Eromanga Basin sediments during a phase of late Cretaceous inland Australian uplift, but when coupled with reconnaissance low-temperature thermochronometry from the region of the Ceduna River course indicating widespread Triassic-Jurassic exhumation, and comparisons with detrital zircon data from the Winton Formation upstream of any proposed uplift, we suggest that both lobes of the Ceduna Delta are likely to be derived from a transcontinental Ceduna River.
基金funded by the Geological Survey of South Australia and was made possible through an Australian Research Council grant (ARC LE150100145)
文摘Apatite U-Pb thermochronology was applied to granitoid basement samples across the northern Gawler Craton to unravel the Proterozoic, post-orogenic, cooling history and to examine the role of major fault zones during cooling. Our observations indicate that cooling following the ~2500 Ma Sleaford Orogeny and ~1700 Ma Kimban Orogeny is restricted to the Christie and Wilgena Domains of the central northern Gawler Craton. The northern Gawler Craton mainly records post-Hiltaba Event(~1590 Ma) U-Pb cooling ages. Cooling following the ~1560 Ma Kararan Orogeny is preserved within the Coober Pedy Ridge,Nawa Domain and along major shear zones within the south-western Fowler Domain. The Nawa Domain samples preserve U-Pb cooling ages that are >150 Ma younger than the samples within the Coober Pedy Ridge and Fowler Domain, indicating that later(~1300 Ma) fault movement within the Nawa Domain facilitated cooling of these samples, caused by arc collision in the Madura Province of eastern Western Australia. When compared to^(40)Ar/^(39) Ar from muscovite, biotite and hornblende, our new apatite U-Pb ages correlate well, particularly in regions of higher data density. Our data also preserve a progressive younging of U-Pb ages from the nucleus of the craton to the periphery with a stark contrast in U-Pb ages across major structures such as the Karari Shear Zone and the Southern Overthrust, which indicates the timing of reactivation of these major crustal structures. Although this interpolation was based solely on thermochronological data and did not take into account structural or other geological data, these maps are consistent with the structural architecture of the Gawler Craton and reveal the thermal footprint of known tectonic and magmatic events in the Gawler Craton.
