Preservation of late Palaeozoic glacial rock surfaces by burial prior to Cenozoic exhumation, Fleurieu Peninsula, southeastern Australia

2021 ◽  
pp. jgs2020-250
Author(s):  
Simon P. Holford ◽  
Paul F. Green ◽  
Ian R. Duddy ◽  
Richard R. Hillis ◽  
Steven M. Hill ◽  
...  
Keyword(s):  
Sedimentary Cover ◽  
South Australia ◽  
Early Permian ◽  
Glacial Erosion ◽  
Metasedimentary Rocks ◽  
Southeastern Australia ◽  
Australian Continent ◽  
Geomorphic Features ◽  
Granitic Intrusions ◽  
Early Palaeozoic

The antiquity of the Australian landscape has long been the subject of debate, with some studies inferring extraordinary longevity (>108 Myr) for some subaerial landforms dating back to the early Palaeozoic. A number of early Permian glacial erosion surfaces in the Fleurieu Peninsula, southeastern Australia, provide an opportunity to test the notion of long-term subaerial emergence, and thus tectonic and geomorphic stability, of parts of the Australian continent. Here we present results of apatite fission-track analysis (AFTA) applied to a suite of samples collected from localities where glacial erosion features of early Permian age are developed. Our synthesis of AFTA results with geological data reveals four cooling episodes (C1-4), which are interpreted to represent distinct stages of exhumation. These episodes occurred during the Ediacaran to Ordovician (C1), mid-Carboniferous (C2), Permian to mid-Triassic (C3) and Eocene to Oligocene (C4).The interpretation of AFTA results indicates that the Neoproterozoic-Lower Palaeozoic metasedimentary rocks and granitic intrusions upon which the glacial rock surfaces generally occur were exhumed to the surface by the latest Carboniferous-earliest Permian during episodes C2 and/or C3, possibly as a far-field response to the intraplate Alice Springs Orogeny. The resulting landscapes were sculpted by glacial erosive processes. Our interpretation of AFTA results suggests that the erosion surfaces and overlying Permian sedimentary rocks were subsequently heated to between ∼60 and 80°C, which we interpret as recording burial by a sedimentary cover comprising Permian and younger strata, roughly 1 kilometre in thickness. This interpretation is consistent with existing thermochronological datasets from this region, and also with palynological and geochronological datasets from sediments in offshore Mesozoic-Cenozoic-age basins along the southern Australian margin that indicate substantial recycling of Permian-Cretaceous sediments. We propose that the exhumation which led to the contemporary exposure of the glacial erosion features began during the Eocene to Oligocene (episode C4), during the initial stages of intraplate deformation that has shaped the Mt Lofty and Flinders Ranges in South Australia. Our findings are consistent with several recent studies, which suggest that burial and exhumation has played a key role in the preservation and contemporary re-exposure of Gondwanan geomorphic features in the Australian landscape.

Between Greenhouse and Icehouse

2012 ◽  
Author(s):  
Jan Zalasiewicz ◽  
Mark Williams
Keyword(s):  
Sixteenth Century ◽  
Early Permian ◽  
Late Archaean ◽  
Climate Modes ◽  
The Earth ◽  
The World ◽  
Per Se ◽  
Early Palaeozoic ◽  
Pieter Bruegel ◽  
Pieter Bruegel The Elder

There is a celebrated Flemish painting by Pieter Bruegel the Elder in the Kunsthistorisches Museum in Vienna. It depicts the age-old battle between Carnival and Lent. Carnival—a time of high spirits, led in this vision by a fat man on a beer-barrel, carousing and brandishing a pig’s head on a spit—is opposed by Lent, deflating the happy excitement and bringing in a time of sobriety and abstinence. Bruegel’s understanding of these opposed rhythms of rural life in the sixteenth-century Netherlands was acute: he was nicknamed ‘Peasant Bruegel’ for his habit of dressing like the local people, to mingle unnoticed with the crowds, all the better to observe their lives and activities. Bruegel’s vision of the age-old rhythm of life, in the form of an eternal oscillation between two opposing modes, may be taken to a wider stage. From the late Archaean to the end of the Proterozoic, the Earth has alternated between two climate modes. Long episodes of what may be regarded as rather dull stability, best exemplified by what some scientists refer to as the ‘boring billion’ of the mid-Proterozoic, are punctuated by the briefer, though more satisfyingly dramatic, glacial events. This alternation of Earth states persisted into the last half-billion years of this planet’s history—that is, into the current eon, the Phanerozoic. If anything, the pattern became more pronounced, as if it had become an integral part of the Earth’s slowly moving clockwork. There were three main Phanerozoic glaciations—or more precisely, there were three intervals of time when the world possessed large amounts of ice—though in each of these, the ice waxed and waned in a rather complex fashion, and none came close to a Snowball-like state. Thus, these intervals often now tend to be called ‘icehouse states’ rather than glaciations per se. Between these, there were rather longer intervals—greenhouse states—in which the world was considerably warmer; though again, this warmth was variable, and at times modest amounts of polar ice could form. Of the Earth’s Phanerozoic icehouse states, two are in the Palaeozoic Era: one, now termed the ‘Early Palaeozoic Icehouse’ centred on the boundary between the Ordovician and Silurian periods, peaking some 440 million years ago; and a later one centred on the Carboniferous and early Permian periods, 325 to 280 million years ago.

PLATE TECTONICS AND THE EVOLUTION OF THE TIMOR SEAR NORTHWEST AUSTRALIA

1973 ◽  
Vol 13 (1) ◽  
pp. 13 ◽  
Author(s):  
B. J. Warris
Keyword(s):  
Early Cretaceous ◽  
Rift Valley ◽  
Plate Tectonics ◽  
Ocean Basin ◽  
Complete Separation ◽  
The North ◽  
Australian Continent ◽  
Early Palaeozoic ◽  
Oceanic Plates ◽  
Shelf Sedimentation

The Browse and Bonaparte Gulf Basins in northwestern Australia contain sedimentary sections which range in age from early Palaeozoic to Recent. These basins developed as a result of the rifting and break up of Gondwanaland into two continents. The sedimentary and tectonic histories of these basins clearly reflect the relative movements of these continents.In pre-Permian times, the earliest postulated rifting may have been early Palaeozoic associated with the north-south separation of Gondwanaland from Eurasia which produced the Tethyan Sea. This was followed by Middle Palaeozoic rifting which affected the Bonaparte Gulf Basin, Fitzroy Graben and perhaps also the Browse Basin.A Late Carboniferous-Early Permian rift valley developed between the Kimberley Block and a western landmass. Alternate marine and fluvio-deltaic deposits characterised sedimentation in this rift valley until Early Jurassic time. Marine transgressions inundated from the north where the rift valley opened into the Tethyan Sea.During the Late Jurassic and Early Cretaceous, the western landmass was detached from the Australian continent along a major right lateral wrench fault. At this time the Indian Ocean Basin appeared as a distinct morphological unit and inundated the Browse Basin. Associated with these movements were the emergence of the Ashmore-Sahul Block and Northeast Londonderry Ridge and the development of the Scott Reef-Buccaneer trend. Marine volcanics at Scott Reef and Ashmore Reef may be related to the formation of new ocean crust.At the end of the Early Cretaceous, tectonic events associated with the complete separation of the western landmass from Australia, resulted in a regional northwesterly tilt of the basin and a major marine transgression.During the Tertiary, Australia moved north, away from Antarctica, and eventually collided with the Southeast Asian and West Pacific oceanic plates. Timor uplifted as a Tertiary melange of Australian sediments behind a north-dipping sub-duction zone along the Timor Trough. The Timor Sea remained relatively stable and was the site of carbonate shelf sedimentation.

PREDICTION OF CARBONATE RESERVOIRS AND TRAPS BY APPLYING SEQUENCE STRATIGRAPHY IN THE EASTERN WARBURTON BASIN, SOUTH AUSTRALIA

1998 ◽  
Vol 38 (1) ◽  
pp. 380 ◽  
Author(s):  
X.W. Sun
Keyword(s):  
Seismic Reflection ◽  
South Australia ◽  
High Amplitude ◽  
Carbonate Reservoirs ◽  
Source Rocks ◽  
Shelf Edge ◽  
Secondary Porosity ◽  
Sandy Limestone ◽  
Potential Reservoir ◽  
Early Palaeozoic

The Early Palaeozoic eastern Warburton Basin unconformably underlies the Cooper and Eromanga Basins. Four seismic sequence sets (I−IV) are interpreted. Among them, sequence set II is subdivided into four Cambro-Ordovician depositional sequences. Sequence 1, the oldest, is a shallow shelf deposit that occurs only in the Gidgealpa area. Sequences 2 and 3 were deposited in a wider area; from west to east, environments varyied from deep siliciclastic ramp, carbonate inner-shelf, peritidal, shelf edge, and slope-to-basin. Their seismic reflection configurations are high-amplitude, regionally parallel-continuous, layered patterns, locally mounded geometry, as well as divergent-fill patterns. Sequence 4, the youngest, was deposited in a mixed siliciclastic and carbonate, storm-dominate shelf. Its seismic reflection configurations are moderate amplitude, parallel-layered patterns, decreasing in amplitude upwards.Boundaries between the four sequences generated good secondary porosity in the carbonates. Karst development is interpreted to have generated much of this porosity in shelf and peritidal carbonates, and carbonate build-ups. Shoal-water sandy limestone and calcareous sandstone of Sequence 4 may be other potential reservoir rocks. Potential source rocks comprise mudstone and shale of slope and basin lithofacies. There are two kinds of stratigraphic trap. One is in Sequences 2 and 3, associated with high-relief carbonate build-ups encased in lagoonal mudstone and shelf edge sealed by transgressive siltstone and shale. The other is a transgressive marine shale enclosing porous dolostone of the karstified Sequence 1. In addition, petroleum may have migrated from Permian source rocks of the Cooper Basin to karstified carbonate reservoirs of the Warburton Basin at unconformities.

scholarly journals Simulations of atmospheric methane for Cape Grim, Tasmania, to constrain southeastern Australian methane emissions

2015 ◽  
Vol 15 (1) ◽  
pp. 305-317 ◽  
Author(s):  
Z. M. Loh ◽  
R. M. Law ◽  
K. D. Haynes ◽  
P. B. Krummel ◽  
L. P. Steele ◽  
...  
Keyword(s):  
Climate Models ◽  
Atmospheric Model ◽  
Methane Emissions ◽  
Atmospheric Methane ◽  
Austral Spring ◽  
Southeastern Australia ◽  
Australian Continent ◽  
The Impact ◽  
Methane Concentrations ◽  
Cape Grim

Abstract. This study uses two climate models and six scenarios of prescribed methane emissions to compare modelled and observed atmospheric methane between 1994 and 2007, for Cape Grim, Australia (40.7° S, 144.7° E). The model simulations follow the TransCom-CH4 protocol and use the Australian Community Climate and Earth System Simulator (ACCESS) and the CSIRO Conformal-Cubic Atmospheric Model (CCAM). Radon is also simulated and used to reduce the impact of transport differences between the models and observations. Comparisons are made for air samples that have traversed the Australian continent. All six emission scenarios give modelled concentrations that are broadly consistent with those observed. There are three notable mismatches, however. Firstly, scenarios that incorporate interannually varying biomass burning emissions produce anomalously high methane concentrations at Cape Grim at times of large fire events in southeastern Australia, most likely due to the fire methane emissions being unrealistically input into the lowest model level. Secondly, scenarios with wetland methane emissions in the austral winter overestimate methane concentrations at Cape Grim during wintertime while scenarios without winter wetland emissions perform better. Finally, all scenarios fail to represent a~methane source in austral spring implied by the observations. It is possible that the timing of wetland emissions in the scenarios is incorrect with recent satellite measurements suggesting an austral spring (September–October–November), rather than winter, maximum for wetland emissions.

scholarly journals Potential Effects of the Loss of Native Grasses on Grassland Invertebrate Diversity in Southeastern Australia

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Roger Edgcumbe Clay
Keyword(s):  
South Australia ◽  
Grass Cover ◽  
Native Plant ◽  
Native Grass ◽  
Native Plant Species ◽  
Grassland Community ◽  
European Settlement ◽  
Southeastern Australia ◽  
Invertebrate Diversity ◽  
Invertebrate Biodiversity

Reduction in area of the southeastern temperate grasslands of Australia since European settlement has been accompanied by degradation of remaining remnants by various factors, including the replacement of native plant species by introduced ones. There are suggestions that these replacements have had deleterious effects on the invertebrate grassland community, but there is little evidence to support these suggestions. In the eastern Adelaide Hills of South Australia, four grassland invertebrate sampling areas, in close proximity, were chosen to be as similar as possible except for the visible amount of native grass they contained. Sample areas were surveyed in four periods (summer, winter, spring, and a repeat summer) using pitfall traps and sweep-netting. A vegetation cover survey was conducted in spring. Morphospecies richness and Fisher’s alpha were compared and showed significant differences between sample areas, mainly in the summer periods. Regression analyses between morphospecies richness and various features of the groundcover/surface showed a strong positive and logical association between native grass cover and morphospecies richness. Two other associations with richness were less strong and lacked a logical explanation. If the suggested direct effect of native grass cover on invertebrate diversity is true, it has serious implications for the conservation of invertebrate biodiversity.

Structure of the Paleozoic basement in the Senegalo-Mauritanian basin (West Africa)

2015 ◽  
Vol 186 (2-3) ◽  
pp. 193-203 ◽  
Author(s):  
Michel Villeneuve ◽  
François Fournier ◽  
Simonetta Cirilli ◽  
Amalia Spina ◽  
Matar Ndiaye ◽  
...  
Keyword(s):  
Sedimentary Cover ◽  
West African ◽  
Thrust Belt ◽  
Early Permian ◽  
West African Craton ◽  
Seismic Surveys ◽  
Northern Area ◽  
Tectonic Events ◽  
Late Palaeozoic ◽  
Unit Unit

Abstract The interpretation of 2D seismic surveys from the Senegalo-Mauritanian basement and the reappraisal of rock-samples from oil exploration drillings provide new insights into the structure of the Appalachian-Mauritanian belts and the overlying Carboniferous and Permian basins. Two different units have been evidenced below the Mesozoic sedimentary cover : a lower unit (Unit 1 : basement) and an upper unit (Unit 2 : Late Palaeozoic basins). Unit 1 shows two distinct tectonic areas : the northern area with two different belts evidenced on both sides of the Senegalese block and the southern area exhibiting various tilted blocks making part of the Palaeozoic (Ordovician to Devonian) Bové basin. In the northern area the Western Thrust Belt is thrust over the Senegalese block while to the east, the so-called Mauritanian belt is thrusted over the West African craton. In the Mauritanian belt area, the youngest deformed sediments belonging to the outcropping Bove basin are Famennian in age. The Mauritanian inner belt underwent two tectono-metamorphic events (circa 330 and 270 Ma). Unit 2 which is unconformably capping both the Western Thrust Belt and the southern tilted blocks of the Paleozoic Bové basin (Casamance basin) is locally affected by eastward and westward-verging thrusts. Unit 2 is dated to the Early Permian by palynomorphs, and could have formed between the early (340–320 Ma) and late (270 Ma) Variscan tectonic events. The subsurface Late Palaeozoic basins from Senegal and Mauritania are interpreted as intra Variscan belt basins, similar to those suspected by seismic investigations off shore Guinea and Mauritania.

Reassessment of the seismic stratigraphy of the Early Palaeozoic Stansbury Basin, Gulf St Vincent, South Australia

1998 ◽  
Vol 45 (4) ◽  
pp. 547-557 ◽  
Author(s):  
T. Flöttmann ◽  
P. W. Haines ◽  
C. D. Cockshell ◽  
W. V. Preiss
Keyword(s):  
South Australia ◽  
Seismic Stratigraphy ◽  
Early Palaeozoic

scholarly journals Comparative geochemical study on Furongian–earliest Ordovician (Toledanian) and Ordovician (Sardic) felsic magmatic events in south-western Europe: underplating of hot mafic magmas linked to the opening of the Rheic Ocean

Solid Earth ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 2377-2409
Author(s):  
J. Javier Álvaro ◽  
Teresa Sánchez-García ◽  
Claudia Puddu ◽  
Josep Maria Casas ◽  
Alejandro Díez-Montes ◽  
...  
Keyword(s):  
Western Europe ◽  
Magmatic Arc ◽  
Rheic Ocean ◽  
Metasedimentary Rocks ◽  
Eastern Pyrenees ◽  
Structural Framework ◽  
Geochemical Study ◽  
Mafic Magmas ◽  
Arc Setting ◽  
Early Palaeozoic

Abstract. A geochemical comparison of early Palaeozoic felsic magmatic episodes throughout the south-western European margin of Gondwana is made and includes (i) Furongian–Early Ordovician (Toledanian) activities recorded in the Central Iberian and Galicia–Trás-os-Montes zones of the Iberian Massif, and (ii) Early–Late Ordovician (Sardic) activities in the Eastern Pyrenees, Occitan Domain (Albigeois, Montagne Noire and Mouthoumet massifs) and Sardinia. Both phases are related to uplift and denudation of an inherited palaeorelief, and stratigraphically preserved as distinct angular discordances and paraconformities involving gaps of up to 22 million years. The geochemical features of the predominantly felsic Toledanian and Sardic activities point to a predominance of magmatic byproducts derived from the melting of metasedimentary rocks, rich in SiO2 and K2O and with a peraluminous character. Zr ∕ TiO2, Zr ∕ Nb, Nb ∕ Y and Zr vs. Ga ∕ Al ratios, and rare-earth element (REE) and εNd(t) values suggest the contemporaneity, for both phases, of two geochemical scenarios characterized by arc and extensional features evolving to distinct extensional and rifting conditions associated with the final outpouring of mafic tholeiite-dominant lava flows. The Toledanian and Sardic magmatic phases are linked to neither metamorphism nor penetrative deformation; on the contrary, their unconformities are associated with foliation-free open folds subsequently affected by the Variscan deformation. The geochemical and structural framework precludes subduction-generated melts reaching the crust in a magmatic arc-to-back-arc setting and favours partial melting of sediments and/or granitoids in the lower continental crust triggered by the underplating of hot mafic magmas related to the opening of the Rheic Ocean.

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