A geological reconnaissance of the Radok Lake area, Amery Oasis, Prince Charles Mountains

1990 ◽  
Vol 2 (1) ◽  
pp. 53-66 ◽  
Author(s):  
B.C. McKelvey ◽  
N.C.N. Stephenson
Keyword(s):  
Granulite Facies ◽  
Alluvial Fan ◽  
Lake Area ◽  
Granulite Facies Metamorphism ◽  
Metamorphic Basement ◽  
Beaver Lake ◽  
Proterozoic Basement ◽  
Uplift And Erosion ◽  
Lambert Glacier ◽  
Coal Measures

At Radok Lake, northern Prince Charles Mountains, more than 2500 m of Permian Amery Group strata in the Beaver Lake graben are downfaulted against a Proterozoic metamorphic basement. An irregular blanket of late Cenozoic Pagodroma Tillite, up to 100 m thick, overlies the Permian strata and Proterozoic basement. The metamorphic basement comprises repeatedly deformed, high-grade felsic, mafic, aluminous and minor calc-silicate rocks derived from igneous and sedimentary precursors. Low- to medium-pressure granulite-facies metamorphism, assumed to be the ~1000 Ma event widely recorded in the East Antarctic Shield, was followed by incipient to moderate amphibolite-facies retrogression. Three folding events are recognized. Sporadic occurrences of pseudotachylite in the basement represent seismic faulting after substantial uplift and erosion. At the southern end of Radok Lake the Permian coarse alluvial fan facies, the Radok Conglomerate, is overlain disconformably by the Dart Fields Conglomerate, a basal member of the Bainmedart Coal Measures. Five kilometres along strike the deltaic Panorama Point beds, containing sideritic ironstone strata, are overlain conformably by arkosic sandstones of the basal Bainmedart Coal Measures. The Amery Group is intruded by two alnöite sills and at least five altered alkaline mafic dykes. The Pagodroma Tillite contains reworked marine microfossils and records the erosion of higher latitude Cenozoic marine sequences by an expanding ancestral Lambert Glacier.

Rubidium–strontium age and origin of uraniferous granite, Molson Lake – Red Sucker Lake area, northwestern Superior Province, Manitoba

1987 ◽  
Vol 24 (3) ◽  
pp. 471-478 ◽  
Author(s):  
G. S. Clark ◽  
W. Weber
Keyword(s):  
Granulite Facies ◽  
Lake Area ◽  
Initial Ratio ◽  
Calc Alkaline ◽  
Small Bodies ◽  
Zircon Age ◽  
Granulite Facies Metamorphism ◽  
The World ◽  
Facies Metamorphism ◽  
Data Points

Late Archean, post-kinematic, uraniferous granite and alaskite occur as several discrete large and small bodies in the 250 km long Molson Lake – Red Sucker Lake batholithic belt, in the western Gods Lake subprovince. Sampled over this length, this unit gave a Rb–Sr whole-rock age of 2495 ± 30 Ma with an initial 87Sr/86Sr ratio of 0.7053 ± 0.0023. The excellent fit of the data points suggest a common, isotopically homogeneous source of magma for the analyzed granite bodies. The initial ratio is consistent with an origin from partial melting of older calc-alkaline rocks, and evidence suggests this event accompanied granulite-facies metamorphism. Based on recent U–Pb zircon ages, this event could have occurred as much as 200 Ma prior to closure of the Rb–Sr isotopic system.An older, monzonite–quartz diorite unit gives a less well-defined age of 2690 Ma, consistent with a U–Pb zircon age from the same unit. This pluton is intrusive into older, tonalitic gneisses and is part of a widespread suite of granitoid plutonic rocks in this subprovince. This pluton gives a low, mantle-like initial ratio, indicating juvenile additions to the crust during this period of batholithic development, consistent with findings for calc-alkaline granitoids in Archean shield areas elsewhere in the world.

Exhumation of high-grade terranes—a review

1992 ◽  
Vol 29 (4) ◽  
pp. 737-745 ◽  
Author(s):  
Jacques Martignole
Keyword(s):  
High Temperature ◽  
Shear Zones ◽  
Granulite Facies ◽  
High Grade ◽  
Granulite Facies Metamorphism ◽  
Magmatic Underplating ◽  
Show Evidence ◽  
Juvenile Crust ◽  
Uplift And Erosion ◽  
Lower Crustal

High-grade (granulite-facies) terranes are brought to the surface by a combination of uplift and erosion (exhumation). The reported mechanisms and durations of exhumation are variable and depend partly on the mode of formation of a given high-grade terrane. In this paper, we consider the case of granulite-facies conditions that are attained (i) in juvenile crust, in the roots of magmatic arcs (e.g., Kohistan, Fiordland), (ii) around deep-seated high-temperature plutonic complexes, and (iii) in the lower parts of thickened continental crust. In the case of the roots of magmatic arcs, Phanerozoic examples suggest that they are exhumed along shallow-dipping contraction faults or shear zones that developed during continental obduction in a convergent tectonic regime. This process is not fundamentally different from processes leading to the exhumation of high-pressure (blueschist, eclogite) terranes. In contrast, deep-seated high-temperature plutonic complexes are thermostructural domes, analogous to the lower levels of core complexes, which may also have contributed to the uprise of high-grade terranes. Such domes should be sought for around anorthositic or mafic plutons, where their ascent may also have been favoured by continental extension. These modes of exhumation are compatible with a monocyclic evolution. However, many high-grade terranes show evidence of a polycyclic evolution and, in such cases, the nature of the thermal perturbation responsible for granulite-facies metamorphism is still debated. Thermal modelling based on heat conduction in collision orogens shows that granulites cannot form at mid-cristal levels, namely those exposed after isostatically driven denudation. Thus, magmatic underplating and crustal extension have been suggested as causes of steepened geotherms. Underplating (or intraplating) supplies the heat and thickens the crust from below. Postcollisional extension has also been considered as a mechanism providing a heat pulse emanating from the asthenosphere, probably after the "detachment" of a relatively cold thermal boundary layer. Finally, isolated crustal-scale intracratonic thrusting may favour the rise of intermediate to lower crustal wedges (e.g., the Kapuskasing wedge, uplifted prior to the trans-Hudson collision).

Sedimentology of the Permian Radok Conglomerate in the Beaver Lake area of MacRobertson Land, East Antarctica

1995 ◽  
Vol 132 (1) ◽  
pp. 51-63 ◽  
Author(s):  
C. R. Fielding ◽  
J. A. Webb
Keyword(s):  
Sediment Accumulation ◽  
East Antarctica ◽  
Upper Permian ◽  
Rift System ◽  
Flow Sheet ◽  
Lake Area ◽  
Organic Sediment ◽  
Sediment Gravity Flow ◽  
Beaver Lake ◽  
Coal Measures

AbstractThe mid- to Upper Permian Radok Conglomerate, the lowermost formation of the Permo-Triassic Amery Group, crops out in the Beaver Lake area of the northern Prince Charles Mountains, East Antarctica. Outcrop is confined to a north-south elongate, fault-bounded corridor interpretedas a remnant of a continental extensional basin formed during Late Palaeozoic times. This basinforms a small part of the much larger Lambert Graben, a major continental rift system. The RadokConglomerate consists of interbedded conglomerates, argillaceous sandstones, siltstones, and minor, thin carbonaceous siltstones and coals. Textural, petrographic, palaeocurrent and other data suggestlocal derivation from Precambrian massifs to the immediate west, during a period of fault activity.The unit is a minimum of 400 m thick, the base being unexposed, and grossly fines upward. It isabruptly overlain by quartzo-feldspathic sandstone-dominated rocks of the Upper Permian Bainmedart Coal Measures. Seven recurrent lithofacies have been recognized with the Radok Conglomerate, and are interpreted as the products of poorly-confined stream flow, sheet flow and sediment gravity flow processes, suspension fallout in shallow standing water, and organic sediment accumulation in peat-forming wetlands. The unit as a whole is interpreted as having accumulated as a coarse alluvial apron along the western margin of a ?graben extensional trough. Similar, though poorly exposed, facies are exposed on the eastern margin of the basin and may reflect similar depositional systems. Towards the top of the Radok Conglomerate, typical Radok lithologies are interbedded with quartzo-feldspathic sandstones derived from the south, precursors of the overlying Bainmedart Coal Measures. Interference between transverse (Radok) and axial (Bainmedart) drainage is possibly related to progressive infilling of extensional topography, thereby allowing axially flowing rivers to avulse increasingly into the Beaver Lake region from the main Lambert Graben.

Lake and inland dunes as interconnected Systems: The story of Lake Tresssee and an adjacent dune field (Schleswig-Holstein, North Germany)

The Holocene ◽  
2020 ◽  
pp. 095968362098168
Author(s):  
Christian Stolz ◽  
Magdalena Suchora ◽  
Irena A Pidek ◽  
Alexander Fülling
Keyword(s):  
Water Level ◽  
Bronze Age ◽  
Environmental Changes ◽  
High Water ◽  
Alluvial Fan ◽  
Water Levels ◽  
Lake Area ◽  
Dune Field ◽  
The North ◽  
Sand Drift

The specific aim of the study was to investigate how four adjacent geomorphological systems – a lake, a dune field, a small alluvial fan and a slope system – responded to the same impacts. Lake Tresssee is a shallow lake in the North of Germany (Schleswig-Holstein). During the Holocene, the lake’s water surface declined drastically, predominately as a consequence of human impact. The adjacent inland dune field shows several traces of former sand drift events. Using 30 new radiocarbon ages and the results of 16 OSL samples, this study aims to create a new timeline tracing the interaction between lake and dunes, as well, as how both the lake and the dunes reacted to environmental changes. The water level of the lake is presumed to have peaked during the period before the Younger Dryas (YD; start at 10.73 ka BC). After the Boreal period (OSL age 8050 ± 690 BC) the level must have undergone fluctuations triggered by climatic events and the first human influences. The last demonstrable high water level was during the Late Bronze Age (1003–844 cal. BC). The first to the 9th century AD saw slightly shrinking water levels, and more significant ones thereafter. In the 19th century, the lake area was artificially reduced to a minimum by the human population. In the dunes, a total of seven different phases of sand drift were demonstrated for the last 13,000 years. It is one of the most precisely dated inland-dune chronologies of Central Europe. The small alluvial fan took shape mainly between the 13th and 17th centuries AD. After 1700 cal. BC (Middle Bronze Age), and again during the sixth and seventh centuries AD, we find enhanced slope activity with the formation of Holocene colluvia.

A Discussion on global tectonics in Proterozoic times - Late Proterozoic cratonization in southwest Saudi Arabia

1976 ◽  
Vol 280 (1298) ◽  
pp. 517-527 ◽  
Keyword(s):  
Saudi Arabia ◽  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Granulite Facies ◽  
Greenschist Facies ◽  
Arabian Shield ◽  
Granulite Facies Metamorphism ◽  
Quartz Monzonite ◽  
Facies Metamorphism ◽  
Global Tectonics

Early cratonal development of the Arabian Shield of southwestern Saudi Arabia began with the deposition of calcic to calc-alkalic, basaltic to dacitic volcanic rocks, and immature sedimentary rocks that subsequently were moderately deformed, metamorphosed, and intruded about 960 Ma ago by dioritic batholiths of mantle derivation (87Sr/86Sr = 0.7029). A thick sequence of calc-alkalic andesitic to rhyodacitic volcanic rocks and volcanoclastic wackes was deposited unconformably on this neocraton. Regional greenschistfacies metamorphism, intensive deformation along north-trending structures, and intrusion of mantle-derived (87Sr/86Sr = 0.7028) dioritic to granodioritic batholiths occurred about 800 Ma. Granodiorite was emplaced as injection gneiss about 785 Ma (87Sr/86Sr = 0.7028- 0.7035) in localized areas of gneiss doming and amphibolite to granulite facies metamorphism. Deposition of clastic and volcanic rocks overlapped in time and followed orogeny at 785 Ma. These deposits, together with the older rocks, were deformed, metamorphosed to greenschist facies, and intruded by calc-alkalic plutons (87Sr/86Sr = 0.7035) between 600 and 650 Ma. Late cratonal development between 570 and 550 Ma involved moderate pulses of volcanism, deformation, metamorphism to greenschist facies, and intrusion of quartz monzonite and granite. Cratonization appears to have evolved in an intraoceanic, island-arc environment of comagmatic volcanism and intrusion.

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