scholarly journals Tectonostratigraphy and evolution of the West Greenland continental margin

2020 ◽  
Vol 67 ◽  
pp. 1-21 ◽  
Author(s):  
Ulrik Gregersen ◽  
Paul C. Knutz ◽  
Henrik Nøhr-Hansen ◽  
Emma Sheldon ◽  
John R. Hopper
Keyword(s):  
Oceanic Crust ◽  
Continental Margin ◽  
Volcanic Rocks ◽  
Sedimentary Basins ◽  
Magnetic Data ◽  
The West ◽  
Seismic Reflection Data ◽  
Baffin Bay ◽  
West Greenland ◽  
North East

Large structural highs and sedimentary basins are identified from mapping of the West Greenland continental margin from the Labrador Sea to the Baffin Bay. We present a new tectonic elements map and a map of thickness from the seabed to the basement of the entire West Greenland margin. In addition, a new stratigraphic scheme of the main lithologies and tectonostratigraphy based on ties to all offshore exploration wells is presented together with seven interpreted seismic sections. The work is based on interpretation of more than 135 000 km of 2D seismic reflection data supported by other geophysical data, including gravity- and magnetic data and selected 3D seismic data, and is constrained by correlation to wells and seabed samples. Eight seismic mega-units (A–H) from the seabed to the basement, related to distinct tectonostratigraphic phases, were mapped. The oldest units include pre-rift basins that contain Proterozoic and Palaeozoic successions. Cretaceous syn-rift phases are characterised by development of large extensional fault blocks and basins with wedge-shaped units. The basin strata include Cretaceous and Palaeogene claystones, sandstones and conglomerates. During the latest Cretaceous, Paleocene and Eocene, crustal extension followed by oceanic crust formation took place, causing separation of the continental margins of Greenland and Canada with north-east to northward movement of Greenland. From Paleocene to Eocene, volcanic rocks dominated the central West Greenland continental margin and covered the Cretaceous basins. Development of the oceanic crust is associated with compressional tectonics and the development of strike-slip and thrust faults, pull-apart basins and inversion structures, most pronounced in the Davis Strait and Baffin Bay regions. During the late Cenozoic, tectonism diminished, though some intra-plate vertical adjustments occurred. The latest basin development was characterised by formation of thick Neogene to Quaternary marine successions including contourite drifts and glacial related shelf progradation towards the west and south-west.

Integrated Geophysical Interpretation of Kerio Valley Basin Stratigraphy, Kenya Rift

2016 ◽  
Author(s):  
Godfred Osukuku ◽  
Abiud Masinde ◽  
Bernard Adero ◽  
Edmond Wanjala ◽  
John Ego
Keyword(s):  
Gravity Data ◽  
Gravity Anomalies ◽  
Fault System ◽  
Magnetic Data ◽  
Data Sets ◽  
Seismic Profiles ◽  
The West ◽  
Seismic Reflection Data ◽  
Basement Rocks ◽  
Western Side

Abstract This research work attempts to map out the stratigraphic sequence of the Kerio Valley Basin using magnetic, gravity and seismic data sets. Regional gravity data consisting of isotactic, free-air and Bouguer anomaly grids were obtained from the International Gravity Bureau (BGI). Magnetic data sets were sourced from the Earth Magnetic Anomaly grid (EMAG2). The seismic reflection data was acquired in 1989 using a vibrating source shot into inline geophones. Gravity Isostacy data shows low gravity anomalies that depict a deeper basement. Magnetic tilt and seismic profiles show sediment thickness of 2.5-3.5 Km above the basement. The Kerio Valley Basin towards the western side is underlain by a deeper basement which are overlain by succession of sandstones/shales and volcanoes. At the very top are the mid Miocene phonolites (Uasin Gishu) underlain by mid Miocene sandstones/shales (Tambach Formation). There are high gravity anomalies in the western and southern parts of the basin with the sedimentation being constrained by two normal faults. The Kerio Valley Basin is bounded to the west by the North-South easterly dipping fault system. Gravity data was significantly of help in delineating the basement, scanning the lithosphere and the upper mantle according to the relative densities. The basement rocks as well as the upper cover of volcanoes have distinctively higher densities than the infilled sedimentary sections within the basin. From the seismic profiles, the frequency of the shaley rocks and compact sandstones increases with depths. The western side of the basin is characterized by the absence of reflections and relatively higher frequency content. The termination of reflectors and the westward dip of reflectors represent a fault (Elgeyo fault). The reflectors dip towards the west, marking the basin as an asymmetrical syncline, indicating that the extension was towards the east. The basin floor is characterized by a nearly vertical fault which runs parallel to the Elgeyo fault. The seismic reflectors show marked discontinuities which may be due to lava flows. The deepest reflector shows deep sedimentation in the basin and is in reasonable agreement with basement depths delineated from potential methods (gravity and magnetic). Basement rocks are deeper at the top of the uplift footwall of the Elgeyo Escarpment. The sediments are likely of a thickness of about 800 M which is an interbed of sandstones and shales above the basement.

scholarly journals Investigations of Tertiary volcanic rocks along the south coast of Nûgssuaq and in eastern Disko, 1987

1988 ◽  
Vol 140 ◽  
pp. 28-32
Author(s):  
L.M Larsen ◽  
A.K Pedersen
Keyword(s):  
Volcanic Rocks ◽  
Field Work ◽  
South Coast ◽  
The West ◽  
West Greenland ◽  
Early Tertiary ◽  
Composite Section ◽  
Greenland Basin ◽  
Volcanic Facies ◽  
Integrated Study

As a continuation of an integrated study of sedimentary and volcanic facies in the Cretaceous to Tertiary West Greenland basin (G. K.Pedersen, 1987; A. K. Pedersen & Larsen, 1987) early Tertiary volcanic rocks were studied in 1987 along a NW-SE trending composite section, about 120 km in length; on Niigssuaq and Disko. The study attempts to establish and describe lithostratigraphic volcanic units in the Tertiary volcanic formations, and through a combination of field mapping, photogrammetry and geochemistry to establish chronostratigraphic horizons through the early Tertiary deposits of the region. In this respect it is essential to identify the same eruptive units as subaeriallava facies and as subaqueous lava or hyaloclastite facies, and to trace subaerial tufts throughout the area. In the first part of the season localities along the Vaigat coast of Nûgssuaq from Kugssinerssuaq in the east to Nûssap qâqarssua in the west were investigated. In the second part of the season very poorly known areas in the western and southem part ofthe Kvandalen region on east Disko were investigated. The field work was supported by the Arctie Station in Godhavn and its cutter Porsild as well as by GGU's cutter J. F. Johnstrup.

scholarly journals An ultrabasic pipe in the eastern Sukkertoppen region, southern West Greenland

1980 ◽  
Vol 100 ◽  
pp. 69-73
Author(s):  
R.P Hall
Keyword(s):  
Granulite Facies ◽  
The South ◽  
The West ◽  
West Side ◽  
West Greenland ◽  
North East ◽  
The North ◽  
South West ◽  
Unusual Occurrence ◽  
Anorthosite Complex

An unusual occurrence of ultrabasic material was located in the eastern Sukkertoppen region during the reconnaissance mapping programme of 1977, the findings of which were described by Allaart et al. (1978). It occurs on a small exposure on the west side of a north-pointing peninsula in the middle of the large nunatak Majorqap alangua (65°53'N, 50°40'W), to the north-east of the Majorqaq valley (Hall, 1978, fig. 21). The area is composed predominantly of a suite of granulite facies granitic gneisses which contain numerous enclaves of pyroxene-bearing amphibolites, and locally anorthositic and gabbroic rocks similar to those seen in the Fiskenæsset anorthosite complex (Myers, 1975). The gneisses in the centre af the nunatak are highly irregular in orient at ion, occupying the complex interseclion af closures af at least two major fold phases. A belt af amphibolitcs forms the cliff at the south-west tip af Majorqap alangua. Related rocks occur in arnphibolite facies in the acea around the lakc Qardlit taserssuat immediately to the soulh (Hall, 1978).

An Index of the Relative Abundance of Wintering Belugas, Delphinapterus leucas, and Narwhals, Monodon monoceros, off West Greenland

1993 ◽  
Vol 50 (11) ◽  
pp. 2323-2335 ◽  
Author(s):  
M. P. Heide-Jørgensen ◽  
H. Lassen ◽  
J. Teilmann ◽  
R. A. Davis
Keyword(s):  
Relative Abundance ◽  
Delphinapterus Leucas ◽  
Late Winter ◽  
The West ◽  
Baffin Bay ◽  
West Greenland ◽  
Abundance Estimate ◽  
Monodon Monoceros ◽  
Pack Ice ◽  
Ice Conditions

Systematic aerial surveys of the wintering grounds of belugas, Delphinapterus leucas, and narwhals, Monodon monoceros, in southern Baffin Bay and northern Davis Strait were conducted in late winter of 1981, 1982, 1990, and 1991. Most belugas were found between 67°N and 69°N and none were seen more than 80 km off the coast of West Greenland. Compared with the surveys in 1981 and 1982, a decline in relative abundance of belugas along West Greenland was evident in 1991. This decline was significant at a probability level of 0.13 of the bootstrapped distribution of the combined abundance estimate. Pod sizes declined significantly between the 1981–82 and 1990–91 surveys. The variations in ice conditions between years did not seem to affect the distribution, clumping, or pod sizes of the belugas. Narwhals were widely distributed in the close pack ice offshore between 65°N and 72°N. Along the West Greenland coast, narwhals were primarily seen at the mouth of Disko Bay. No change in relative abundance or pod sizes could be detected for narwhals.

scholarly journals Oceanic Boundary Conditions for Jakobshavn Glacier. Part II: Provenance and Sources of Variability of Disko Bay and Ilulissat Icefjord Waters, 1990–2011

2015 ◽  
Vol 45 (1) ◽  
pp. 33-63 ◽  
Author(s):  
Carl V. Gladish ◽  
David M. Holland ◽  
Craig M. Lee
Keyword(s):  
Atlantic Water ◽  
Temperature Cycle ◽  
Freshwater Flux ◽  
The West ◽  
Baffin Bay ◽  
West Greenland ◽  
Water Fraction ◽  
West Greenland Current ◽  
Current Water ◽  
Polar Water

AbstractJakobshavn Glacier, west Greenland, has responded to temperature changes in Ilulissat Icefjord, into which it terminates. Basin waters in this fjord exchange with neighboring Disko Bay waters of a particular density at least once per year. This study determined the provenance of this isopycnic layer for 1990–2011 using hydrographic data from Cape Farewell to Baffin Bay. The warm Atlantic-origin core of the West Greenland Current never filled deep Disko Bay or entered the fjord basin because of bathymetric impediments on the west Greenland shelf. Instead, equal parts of Atlantic water and less-saline polar water filled the fjord basin and bathed Jakobshavn Glacier. The polar water fraction was often traceable to the East/West Greenland Current but sometimes to the colder Baffin Current. The huge annual temperature cycle on West Greenland Current isopycnals did not propagate into deep Disko Bay or the fjord basin because isopycnals over the west Greenland shelf were depressed during the warm autumn/winter phase of the cycle.Ilulissat Icefjord basin waters were anomalously cool in summer 2010. This was not because of the record low NAO index winter of 2009/10 or atmospheric anomalies over Baffin Bay but, possibly, because of high freshwater flux through the Canadian Arctic and a weak West Greenland Current in early 2010. Together, this caused cold Baffin Current water to flood the west Greenland shelf. Subpolar gyre warming associated with the NAO anomaly in winter 2009/10 was more likely responsible for the record warm Disko Bay and Ilulissat Icefjord basin waters of 2011/12.

scholarly journals Early Tertiary, low-potassium tholeiites from exploration wells on the West Greenland shelf

1987 ◽  
Vol 136 ◽  
pp. 1-25
Author(s):  
N Hald ◽  
J.G Larsen
Keyword(s):  
Baffin Island ◽  
Quaternary Sediments ◽  
The South ◽  
The West ◽  
Baffin Bay ◽  
West Greenland ◽  
Early Tertiary ◽  
Davis Strait ◽  
Low Potassium

Data on the Tertiary basalts in the Davis Strait region are reported from two exploration wells drilled by Arco and Mobil on the West Greenland shelf. Hellefisk 1 (67°53 'N, 56°44'W), situated only 60 km east of the mid-line in Davis Strait, penetrated the upper 690 m of a subaeriallava sequence continuous with the onshore volcanics of Disko and situated beneath 2.3 km of Paleocene to Quaternary sediments. The lavas are feldspar microporphyritic tholeiites and mostly unmetamorphosed despite the presence of laumontite and prehnite in the vesicular top zones. Nukik 2 (65°38'N, 54°46'W) penetrated 150 m of hyaloclastites and tholeiitic olivine dolerite sheets, presumably sills, some 200 km further to the south. These vo1canics are also deeply buried and are of unknown extension. The drilled rocks, except for the much altered hyaloclastites in the Nukik 2 well, have low contents of Ti02 (0.99-2.03%), K2O (0.09-0.18%) and P2O5 (0.08-0.21%), La/Sm ratios less than one and 87Sr/86Sr ratios of 0.7032 to 0.7044. Chemically they are related to the MORB-like picrites of Baffin Island rather than the less depleted tholeiites of West Greenland. In both areas the MORB affinity may be related to eruptions through a strongly attenuated lithosphere associated with the opening of Baffin Bay and Davis Strait.

scholarly journals Precambrian tectonic inheritance control of the NE Brazilian continental margin revealed by Curie point depth estimation

2021 ◽  
Vol 64 (2) ◽  
Author(s):  
Jefferson Tavares Cruz Oliveira ◽  
José Antonio Barbosa ◽  
David de Castro ◽  
Paulo Correia ◽  
José Ricardo Magalhães ◽  
...  
Keyword(s):  
Continental Margin ◽  
Curie Point ◽  
Sedimentary Basins ◽  
Depth Estimation ◽  
Geothermal Gradient ◽  
Magnetic Data ◽  
Tectonic Inheritance ◽  
The North ◽  
Gravimetric Data ◽  
Moho Depths

An investigation of Curie point depths (CPD) based on spectral analysis of airborne magnetic data was carried out in the NE Brazilian continental margin. The studied region represents a narrow hyper-extended margin with three sedimentary basins. Regional geothermal gradient and heat flow were also calculated. CPD results were integrated with interpretation of 2D deep seismic data and with estimated isostatic Moho depths. The results reveal that the narrow hyper-extended crust is 150 km wide in the southern sector and 80 km wide in the north, with a narrow ocean-continental transition (OCT) zone that varies from 50 km wide in the south sector to 30 to 20 km wide in the north. The CPD isotherm showed the strong influence of the three main continental blocks of Borborema ́s Shield in the tectonic evolution of the three marginal basins. The CPD analysis corroborated models provided by gravimetric data and successfully demonstrated the sharp control of basement compartments on the thermal properties of the marginal basins domains

scholarly journals A seismic and gravity study of the western part of the Cretaceous-Tertiary sedimentary basin of central West Greenland

1975 ◽  
Vol 69 ◽  
pp. 5-9
Author(s):  
J.W Elder
Keyword(s):  
Sea Level ◽  
Distinctive Feature ◽  
Strong Evidence ◽  
Sedimentary Basin ◽  
The West ◽  
Baffin Bay ◽  
West Greenland ◽  
Reflection And Refraction ◽  
Seismic Methods ◽  
Refraction Seismic

In the summer of 1972 a GGU seismic group working on land measured the thickness of sediments in the western part of the Nugssuaq peninsula, West Greenland, by explosion reflection and refraction seismic methods. In the region crudely bounded by Ikorfat, Ubekendt Bjland and Hareøen Cretaeeous-Tertiary sediments extend about 1-3 km below sea level and rest on the granodioritie gneiss basement. The basin shallows gradually toward the west where it is sharply hidden beneath Tertiary basalts. There is strong evidence for continuity of the Cretaeeous-Tertiary sediments aeross Umanak Fjord as far as Ubekendt Bjland. The most distinctive feature of the basement strueture is a ridge, running roughly N-S through the western part of the area, and rising about 2 km above the deeper parts of the basin. This ridge appears as a northerly continuation of the Disko gneiss ridge. The gravity pattern over a 100 km X 50 km strip centred on the western part of the basin shows rapid westward thinning of the earth's crust, and suggests that the basin has its origin in an incompletely rifted structure marginal to the crustal rifting responsible for Baffin Bay.

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