scholarly journals The stratigraphy and deformation of the Precambrian rocks of the Grænseland area, South-West Greenland

1970 ◽  
Vol 86 ◽  
pp. 1-210
Author(s):  
E Bondesen
Keyword(s):  
Sedimentary Basins ◽  
Explosive Volcanism ◽  
Tectonic Activity ◽  
Carbonaceous Shale ◽  
Pillow Lavas ◽  
Carbonate Sedimentation ◽  
Carbonaceous Shales ◽  
Basic Volcanics ◽  
Thrust Zone ◽  
Orogenic Cycle

The Grænseland area exhibits a middle Precambrian (Ketilidian) succession of unusually well preserved sediments, basic volcanics, and intrusives. A Ketilidian type lithostratigraphy is established and the evolution of the sedimentary basins is reconstructed. The sedimentation began on a weathered gneiss surface with residual gravel and arkoses. An early carbonate sedimentation led to a severe alteration of the gneiss substratum. Varved pelites and a magnetite-conglomerate with chert pebbles transgressed the earlier deposited sediments and the gneiss substratum; orthoquartzites were thereafter deposited in two basin structures. The deposition of dolomitic shales and pelites appears to indicate progressively increasing depth. Large amounts of graded greywackes, interpreted as turbitides, bear witness of unstable tectonic conditions and a subaqueous tallus indicates nearby fault activity. Filled with greywackes the basins appear to have stabilized, and a comparatively uniform euxenic facies of carbonaceous shales and dolomites with preserved organic remnants prevailed independent of the earlier basins in a period of tectonic quiescence. A considerable thickness of pillow lavas then appears to have been extruded under conditions of quiet subsidence during the euxenic conditions shown by the existence of an anthracite-carbonaceous shale layer and the local facies relations on top of the pillow lavas. A new phase of sedimentation appears to have taken place under conditions of tectonic activity and explosive volcanism. The total thickness of the Ketilidian strata in Grænseland is approximately 4400 m. This succession is compared with other areas of Ketilidian deposits in SouthWest Greenland. The Ketilidian deposits were deformed in two periods of folding, accompanied by thrusting and metamorphism under low greenshist facies conditions. The first deformation is a local drag in incompetent horizons and is possibly related to the tilting and twisting of the basement surface. The second deformation is of regional importance but of very different development depending on the material affected and its position in relation to the sedimentary basins and earlier formed structures. Some areas are virtually undeformed. The basement reacted to the deformations by brecciation and faulting. An analysis of lineations in a thrust zone indicates that the initially formed lineations were twisted and bent towards the direction of tectonic transport. A correlation, based on deformation of metadykes, is attempted with other areas of Ketilidian activity and it is suggested that the second deformation occurred close to 1635 m.y. and corresponds thus to the Sanerutian plutonic episode. The Ketilidian (1800 m.y.? -1500 m.y.) is envisaged as an orogenic cycle of deposition, folding and metamorphism beginning at and ending with major uncomformities. The basement gneisses are shown to contain evidence for two older (pre-Ketilidian) orogenic cycles.

Voluminous crustal degassing and immiscible sulfide genesis caused by magma-shale interaction in Large Igneous Provinces

2020 ◽  
Author(s):  
Frances Deegan ◽  
Jean Bédard ◽  
Valentin Troll ◽  
Keith Dewing ◽  
Harri Geiger ◽  
...  
Keyword(s):  
Large Scale ◽  
Sedimentary Basins ◽  
High Arctic ◽  
Large Igneous Province ◽  
Carbonaceous Shale ◽  
Canadian High Arctic ◽  
Oceanic Anoxic Event ◽  
Igneous Provinces ◽  
Basin Scale ◽  
Sulfide Melt

<p><span>Large Igneous Province (LIP) activity is hypothesized to impact global volatile cycles causing climate changes and environmental crises deleterious to the biosphere. Recent work suggests that the potential of LIPs to impact climate is magnified where they intrude organic-rich (i.e. shale-bearing) sedimentary basins. However, the chemical and degassing dynamics of magma-shale interaction are not well understood. Here we present the first experimental simulations of disequilibrium interaction between LIP magma and carbonaceous shale during upper crustal sill intrusions in the Canadian High Arctic LIP (HALIP), the latter of which were co-eval with oceanic anoxic event 1a. Experiments show that magma-shale interaction results in intense syn-magmatic degassing and simultaneous precipitation of sulfide droplets at the ablation interface. Magma-shale interaction on a basin-scale can thus generate substantial amounts of climate-active H-C-S volatiles, while the presence of strongly reducing volatiles may also increase the likelihood of magma to segregate a sulfide melt. These findings have fundamental consequences for our understanding of both large-scale Earth outgassing and metal prospectivity in sediment-hosted LIPs.</span></p>

How syn-rift sedimentation promotes the formation of hyper-extended margins

2020 ◽  
Author(s):  
Susanne Buiter
Keyword(s):  
Sedimentary Basins ◽  
Surface Processes ◽  
Tectonic Activity ◽  
Tectonic Deformation ◽  
Continental Margins ◽  
Rifted Margins ◽  
Continental Rifts ◽  
Break Up ◽  
Mountain Belts ◽  
Sediment Layers

<p>Seismic observations show that some rifted continental margins may have substantial amounts of offshore sediments. For example, sediment layers of several kilometres thick are found on the margins of Mid Norway, Namibia and Angola. Intriguingly, these margins are wide, being characterised by distances of several hundreds of kilometres from typical continental crustal thicknesses of 30-40 km to clearly identifiable oceanic crust. On the other hand, some margins that are sediment-starved, such as Goban Spur, Flemish Cap and Northern Norway, have short onshore-to-offshore transitions. Variations in the amount of sediments not only impact the development of offshore sedimentary basins, but the changes in mass balance by erosion and sedimentation can also interact with extensional tectonic processes. In convergent settings, such feedback relationships between erosion and tectonic deformation have long been highlighted: Erosion reduces the elevation and width of mountain belts and in turn tectonic activity and exhumation are focused at regions of enhanced erosion. But what is the role played by surface processes during formation of rifted continental margins?</p><p>I use geodynamic finite-element experiments to explore the response of continental rifts to erosion and sedimentation from initial rifting to continental break-up. The experiments predict that rifted margins with thick syn-rift sedimentary packages are more likely to form hyper-extended crust and require more stretching to achieve continental break-up than sediment-starved margins. These findings imply that surface processes can control the style of continental break-up and that the role of sedimentation in rifted margin evolution goes far beyond the simple exertion of a passive weight.</p>

Kaolin polytype evidence for a hot-fluid pulse along Caledonian thrusts during rifting of the European Margin

2004 ◽  
Vol 68 (3) ◽  
pp. 419-432 ◽  
Author(s):  
J. Parnell ◽  
G. Watt ◽  
H. Chen ◽  
H. Wycherley ◽  
A. Boyce ◽  
...  
Keyword(s):  
Heat Flow ◽  
Meteoric Water ◽  
Direct Evidence ◽  
Sedimentary Basins ◽  
High Heat ◽  
Crustal Extension ◽  
Palaeomagnetic Data ◽  
Thrust Zone ◽  
O Isotope ◽  
Isotope Analyses

AbstractSedimentary basins developed along the European margin during the earliest, Permian, stage of proto-Atlantic rifting, during a phase of high heat flow. The proximity of some basins to Caledonian thrusts has implied that rifts locally utilized the basement fabric. New mineralogical and palaeomagnetic data show that thrust planes in the Moine Thrust Zone channelled a pulse of hot fluid in Permian time. The fluids precipitated kaolin in fractures in the thrust zone, and with decreasing intensity away from the zone. The high-temperature polytype dickite is largely confined to major thrust planes. Stable H and O isotope analyses indicate that the parent fluid included meteoric water involved in a hydrothermal system. Coeval hydrothermal hematite has a chemical remanence that dates the fluid pulse as Permian. This is direct evidence for post-orogenic activity in the thrust zone, in which the thrusts vented excess heat during regional crustal extension. The example from the European margin exemplifies the importance of deep-seated structures in the release of heat, and the value of kaolinite polytype mapping as a tool to record anomalous palaeo-heat flow.

scholarly journals Impact of volcanic and post volcanic activity on fluvial relief

2019 ◽  
pp. 49-66
Author(s):  
E. V. Lebedeva
Keyword(s):  
Explosive Volcanism ◽  
Hydrothermal Activity ◽  
River Network ◽  
Tectonic Activity ◽  
Lava Tubes ◽  
Near Surface ◽  
Volcanic Material ◽  
Mud Volcanism ◽  
High Erosion Rate ◽  
Characteristic Features

The characteristic features of the river network, the structure and functioning of the valleys affected by effusive and explosive volcanism, volcano-tectonic phenomena, gas hydrothermal activity and mud volcanism are revealed. It has been established that within flows and covers of effusives, the formation of new streams channels can occur not only due to backward erosion, but also as a result of the collapse of the roof of the near-surface lava tubes, which are actively used by underground runoff. A high erosion rate, a large volume of solid runoff, and a significant role of deflation in the transformation of the fluvial relief are characteristic for regions of domination of explosive activity. There valleys become zones of accumulation of volcanic material, which is gradually processed by mudflow, alluvial, aeolian and other processes. Volcanic-tectonic activity changes the rivers position, direction of streams and morphology of the valleys, leading to numerous reorganizations of the river network, as a result of which the valleys of modern watercourses often consist of uneven-age fragments. Valleys of hydrothermal zones are characterized by the active development of slope processes, which leads to the formation in them not only of sinter terraces, but also numerous landslide ones. Mud volcanic processes periodically lead to the filling and blocking of the valleys with mud breccia flows, which affects both the composition of the alluvium of watercourses and the morphology of the valleys.

scholarly journals TOURMALINE MINERALIZATION IN CARBONACEOUS SHALE OF THE BAIKAL DEPOSIT (SOUTH URAL)

2021 ◽  
Author(s):  
A.V. Snachev ◽  
◽  
A.V. Kolomoets ◽  
M.A. Rassomakhin ◽  
V.I. Snachev ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Black Shale ◽  
Gold Mineralization ◽  
Geological Structure ◽  
Orogenic Gold ◽  
Carbonaceous Shale ◽  
Sulfide Deposits ◽  
Carbonaceous Shales ◽  
Gold Sulfide

The article discusses the geological structure of the Baikal deposit, located within the Kumak ore field and confined to the black shale of the Bredy Formation (C1bd). It has been established that the gold mineralization within the occurrence is confined mainly to the members of quartz-mica-tourmaline metasomatically altered carbonaceous shales. Gold is noted here in intergrowth with tourmaline. In terms of their chemical composition, tourmalines belong to dravite and foitite and are close to those of orogenic gold and gold-sulfide deposits. The close intergrowth of thin needle- like tourmaline and gold indicates the synchrony of their formation and allows the manifestation of Baikal deposit to be attributed to the quartz-tourmaline formation.

scholarly journals Optical (visual) Kerogen assessment of Enugu Shale, Anambra Basin, Southeastern Nigeria: Implications for source rock potential and thermal maturation

2021 ◽  
Vol 19 (1) ◽  
pp. 123-132
Author(s):  
Osita Igwebuike Chiaghanam ◽  
Okechukwu Nicodemus Ikegwuonu ◽  
Chikodi Jennifer Ekwegbalu ◽  
Emmanuel Ude Aniwetalu ◽  
Kingsley Chukwuebuka Chiadikobi
Keyword(s):  
Source Rock ◽  
Sedimentary Basins ◽  
Geochemical Data ◽  
Carbonaceous Shale ◽  
Thermal Alteration ◽  
Southeastern Nigeria ◽  
Petroleum Potential ◽  
Anambra Basin ◽  
Kerogen Type ◽  
Rock Eval

Palynological analysis was carried out on Ten (10) samples from outcrops of the Campanian Enugu Formation, a component  lithostratigraphic unit of the Anambra Basin, using the acid maceration techniques for recovering acidinsoluble organic-walled microfossils. Two main lithological units were encountered, which include: carbonaceous shale and siltstone. Result from kerogen  laboratory examination reveals two (2) main groups of palynofacies association namely; palynofacies (A and B), based on the change in particulate organic matter constituents of organic residue extract. Palynofacies A is characterized by abundant opaques debris with common terrestrial phytoclasts, which occupy the southwestern and northwestern parts of the studied area, whereas palynofacies B  dominates in the northeastern part, characterised by abundant phytoclasts followed by frequent opaques debris. Kerogen type III with gas-prone material is suggested for both palynofacies. The examined exine of spore/ pollen grain are pale yellow – yellow, with Thermal Alteration Index TAI of 1+ to 2- and Vitrinite Reflectane (R o) (0.3 % - 0.4 %) in palynofacies A, and yellow – yellow brown, with Thermal Alteration Index TAI of 2- to 2, and Vitrinite Reflectane (R o) of 0.3% - 0.5% in palynofacies B. These revealed source rock that is thermally immature to slightly mature but has potential to generate mainly gas. The kerogen data generated using transmitted light microscopy correlated well with geochemical data obtained using rock-eval pyrolysis method, and this shows the method a reliable tool for assessing  petroleum potential in any given sedimentary basins.

scholarly journals Late Cretaceous and Danian limestone

1982 ◽  
Vol 8 ◽  
pp. 49-62
Author(s):  
Kirsten Lieberkind ◽  
Inger Bang ◽  
Naja Mikkelsen ◽  
Erik Nygaard
Keyword(s):  
North Sea ◽  
Late Cretaceous ◽  
Tectonic Activity ◽  
Calcareous Nannoplankton ◽  
Carbonate Sedimentation ◽  
The North ◽  
The North Sea ◽  
Early Cretaceous Period ◽  
Sea Area ◽  
Cretaceous Period

At the termination of the Early Cretaceous period, the sea transgressed large earlier land areas. The transgression, the reduced relief of the continents, the generally diminished tectonic activity, the climatic change, and the enormous production of calcareous nannoplankton in the oceans profoundly changed the gross facies pattern in the North Sea region. The elastic sedimentation was replaced during Late Cretaceous time by offshore relatively deep water carbonate sedimentation. This resulted in the deposition of a chalk sequence reaching a thickness of 1-2 km in the Danish Subbasin and the North Sea area.

scholarly journals Cosmogenic nuclide dating of the sediments of Bulmer Cavern: Implications for the uplift history of southern Northwest Nelson, South Island New Zealand

2021 ◽  
Author(s):  
◽  
Gavin Holden
Keyword(s):  
Late Miocene ◽  
Plate Boundary ◽  
Sedimentary Basins ◽  
Tectonic Activity ◽  
Published Data ◽  
Uplift Rate ◽  
Cosmogenic Nuclide ◽  
Alpine Fault ◽  
Uplift Rates ◽  
Rapid Uplift

<p>The landscape of Northwest Nelson shows evidence of significant tectonic activity since the inception of the Austro-Pacific plate boundary in the Eocene. Evidence of subsidence followed by rapid uplift from the Eocene to the late Miocene is preserved in the sedimentary basins of Northwest Nelson. However, the effects of erosion mean there is very little evidence of post-Miocene tectonic activity preserved in the Northwest Nelson area. This is a period of particular interest, because it coincides with the onset of rapid uplift along the Alpine Fault, which is located to the south, and the very sparse published data for this period suggest very low uplift rates compared to other areas close to the Alpine Fault.  Cosmogenic nuclide burial dating of sediments preserved in Bulmer Cavern, indicate an uplift rate of 0.13mm/a from the mid-Pliocene to the start of the Pleistocene and 0.067mm/a since the start of the Pleistocene.  The Pleistocene uplift rate is similar to other published uplift rates for this period from the northern parts of Northwest Nelson, suggesting that the whole of Northwest Nelson has experienced relative tectonic stability compared to other areas close to the Alpine Fault during this period. The mid-Pliocene uplift rate is possibly the first precisely constrained uplift rate in the area for this period, and suggests that there has been a progressive decrease in uplift rates from much higher rates in the late Miocene.</p>

Tectonic activity of sedimentary basins as a natural stage of their evolution

2002 ◽  
Vol 8 (2-3) ◽  
pp. 142-143
Author(s):  
V.G. Pazynych ◽  
◽  
N.V. Pazynych ◽  
Keyword(s):  
Sedimentary Basins ◽  
Tectonic Activity
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