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 ◽  
...  

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

2019 ◽  
Vol 59 (4) ◽  
pp. 656-669
Author(s):  
A. Zabanbark ◽  
L. I. Lobkovsky

At the limit of the East-Canadian continental margin there are three oil and gas regions from north to south: Labrador Sea shelves, margins of the Great Newfoundland Bank and the continental margin of Nova Scotia. In each of these distinguishing regions are a number of sedimentary basins completely plunging under the water. At the shelf of Labrador Sea distinguishing the following large sedimentary basins: Saglek, Hopdale and Havke, at the margin of Newfoundland Bank it is known the basins: Jeanne d’Arc, Flemish Pass and Orphan. At the Nova Scotia shelf there are Nova Scotian and Sable basins. It is remarkable at the lofty latitude like of Labrador Sea region the age of the productive sediments beginning from more ancient rocks (Paleozoic), than in basins situated in law latitude (Mesozoic). In consequence of this the stratigraphy diapason of oil and gas bearing of the north latitude is considerably wide. The prospect of oil and gas bearing in all region is related principally with continental slopes and turbidites sediments in its. Late Jurassic and early Cretaceous reservoirs would be the aim for deep drilling sediments. Wide distribution of late Cretaceous and early Tertiary prospects reservoirs of oil and gas is quite really so far as they are bedded in the shallow horizons. Also the prospect of oil and gas bearing at the margin of the basin is related to late Cretaceous and Tertiary sediments, to deposits of fan and diapirs salt.


2020 ◽  
Vol 67 ◽  
pp. 1-21 ◽  
Author(s):  
Ulrik Gregersen ◽  
Paul C. Knutz ◽  
Henrik Nøhr-Hansen ◽  
Emma Sheldon ◽  
John R. Hopper

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.


2015 ◽  
Vol 41 ◽  
pp. 5-10
Author(s):  
M.-T. Apoloner ◽  
G. Bokelmann

Abstract. The Vienna Basin in Eastern Austria is a region of low to moderate seismicity, and hence the seismological network coverage is relatively sparse. Nevertheless, the area is one of the most densely populated and most developed areas in Austria, so accurate earthquake location, including depth estimation and relation to faults is not only important for understanding tectonic processes, but also for estimating seismic hazard. Particularly depth estimation needs a dense seismic network around the anticipated epicenter. If the station coverage is not sufficient, the depth can only be estimated roughly. Regional Depth Phases (RDP) like sPg, sPmP and sPn have been already used successfully for calculating depth even if only observable from one station. However, especially in regions with sedimentary basins these phases prove difficult or impossible to recover from the seismic records. For this study we use seismic array data from GERES. It is 220 km to the North West of the Vienna Basin, which – according to literature – is a suitable distance to recover PmP and sPmP phases. We use array processing on recent earthquake data from the Vienna Basin with local magnitudes from 2.1 to 4.2 to reduce the SNR and to search for RDP. At the same time, we do similar processing on synthetic data specially modeled for this application. We compare real and synthetic results to assess which phases can be identified and to what extent depth estimation can be improved. Additionally, we calculate a map of lateral propagation behavior of RDP for a typical strike-slip earthquake in our region of interest up to 400 km distance. For our study case RDP propagation is strongly azimuthally dependent. Also, distance ranges differ from literature sources. Comparing with synthetic seismograms we identify PmP and PbP phases with array processing as strongest arrivals. Although the associated depth phases cannot be identified at this distance and azimuth, identification of the PbP phases limits possible depth to less than 20 km. Polarization analysis adds information on the first arriving Pn wave for local magnitudes above 2.5.


2014 ◽  
Vol 2 (2) ◽  
pp. T69-T78 ◽  
Author(s):  
Ahmed Salem ◽  
Chris Green ◽  
Samuel Cheyney ◽  
J. Derek Fairhead ◽  
Essam Aboud ◽  
...  

Magnetic depth estimation methods are routinely used to map the depth of sedimentary basins by assuming that the sediments are nonmagnetic and underlain by magnetic basement rocks. Most of these methods generate basement depth estimates at discrete points. Converting these depth estimates into a grid or map form often requires the application of qualitative methods. The reason for this is twofold: first, in deeper parts of basins, there is generally a scarcity of depth estimates and those that have been determined tend to be biased toward the shallower basement structures close to the basin edge; and second, depth estimates intrinsically relate to magnetic anomalies that emanate from the top edges of basement faults/contacts resulting in a shallow depth bias. Thus, simple grid interpolation of these depth estimates often forms a shallower and structurally unrepresentative map when evaluated in detail. To overcome these problems of qualitative and/or simple grid interpolation of these point-depth estimates into a regular grid, we use the pseudogravity field transform response of the magnetic field to constrain this interpolation using inversion methods together with the relationship between the point-depth estimates and their pseudogravity values. The pseudogravity transformation converts a grid of magnetic data such that the resulting grid has the same simple relationship to magnetic susceptibility that a gravity grid has to density. The pseudogravity map is thus straightforward to visualize in terms of basement structure, but it only maps the magnetic properties of the subsurface and is not related to the gravity anomaly or the density. We describe a practical approach to invert pseudogravity grids using gravity inversion software to produce a 3D basin model assuming a constant susceptibility basement. The approach is initially tested on the Bishop 3D model and then applied to an example from the northern North Sea. This approach can be considered complementary to 3D gravity inversion and has the advantage that the pseudogravity response is not affected by structure within the sediments or effects such as sediment compaction, inversion, or isostatic compensation, all of which often complicate the gravity response of sedimentary basins.


1982 ◽  
Vol 22 (1) ◽  
pp. 283 ◽  
Author(s):  
J. J. Veevers ◽  
J. G. Jones ◽  
C. McA. Powell

Two morphotectonic features dominated the development of Australia's Phanerozoic sedimentary basins: a rifted arch on the divergent western and southern margins, such as exists today in East Africa-Arabia, and a volcanic arc on the convergent eastern margin, such as the present Andaman-Sumatran Arc. A presumed rifted-arch system, associated on one side with the growth of the Tethyan Ocean and on the other with failed arms, developed in northwest Australia from the beginning of the Phanerozoic. A second system developed in the same area and extended southward between Greater India and Australia in the Late Carboniferous and evolved in the Late Jurassic and Early Cretaceous into the eastern Indian Ocean. Also in the Late Jurassic a rifted-arch system developed along the southern margin between Antarctica and Australia and in the Late Cretaceous evolved into the southeast Indian Ocean. On both margins the rifted-arch system was succeeded for some 30 to 40 Ma by rim basins confined between the continent and an uplifted rim alongside the continent-ocean boundary, so that restricted marine sediment was deposited over a terrain of rift-valley fluvial sediment cut into fault blocks in a configuration favourable to petroleum accumulation. In the Ceduna Plateau depocentre of the Great Australian Bight Basin a very thick rim basin was deposited in a saddle of the rifted-arch system from a copious provenance in the ancestral Eastern Highlands. On both margins the rim basins were overlain by open marine deposits, mainly carbonate, of varying thickness.The convergent eastern margin started also at the beginning of the Phanerozoic, and developed through marginal sea opening and filling behind an island arc; widespread deformation then followed, and led in the Early Silurian to the development of a basin-and- range terrain. In the Late Devonian, a volcanic arc appeared along the continental margin, and subsequently jumped eastward twice to the mid-Cretaceous. The succession of jumps generated a vertical sequence of basins that at any one time existed side by side, so that the fore-arc basin is overlain by the foreland, in turn overlain by the pericratonic basin. The foreland and pericratonic basins, on the landward side of the volcanic arc, received volcanogenic sediment, prone to be marine, from the arc, and quartzose sediment, prone to be fluvial, from the craton; the foreland basin was subjected to shearing from transcurrent motion along the arc, so that growth structures provided receptacles for petroleum generated by heat flow from the arc. The marginal marine volcanogenic sediment was the main source and the interfingering fluvial quartz sand the reservoir.Three tectonic regimes can be recognized, and are characterized by intervals of relatively constant latitude, climate, depositional facies, and plate configuration. A Pre-Gondwanan regime, 570 to 320 Ma ago, of low latitude, started with plate divergence on the northwest and convergence on the east, and ended with widespread deformation in the east and centre, of an age and kind similar to that affecting the ancestral Rocky Mountains of North America. A Gondwanan regime, from 320 to 95 Ma, of high latitude, with rare evaporites and carbonates, started with a rift-valley system along the western margin that developed into the Indian Ocean 160 to 125 Ma ago, and an arc jump on the east; and ended with the separation of Antarctica and Australia (by the splitting of a rifted arch) on the south, and of Australia and Lord Howe Rise (by the splitting of an arc) on the east. A Post-Gondwanan regime, 95 to 0 Ma ago, of diminishing latitude, has restored carbonates to Australia along its divergent margins, and in the north, in New Guinea, a continental margin volcanic arc, similar to the Gondwanan arcs, has led to uplift in the Neogene.


1998 ◽  
Vol 1 (05) ◽  
pp. 476-484 ◽  
Author(s):  
Richard Morgan ◽  
Colm Murphy

This paper (SPE 51828) was revised for publication from paper SPE 38503, first presented at the 1997 SPE Offshore Europe Conference, Aberdeen, 9-12 September. Original manuscript received for review 9 September 1997. Revised manuscript received 6 July 1998. Paper peer approved 10 July 1998. Summary Fundamental geological and environmental differences exist between the basins of the North Sea and the basins of the northwest European continental margin, and strategies for success in the North Sea have not necessarily transferred directly to the continental margin. As a result, exploration outcomes to date have been somewhat disappointing, with one or two notable exceptions. Furthermore, a change in the approach to acreage evaluation places increasing levels of reliance on seismic data, specifically three-dimensional (3D) data, to tie down prospects before drilling. This approach focuses down rapidly to the prospect scale, and, although allowing detailed analysis of target structures, there is a risk of creating a gap in understanding between the geological processes observed at the basin scale and those at the prospect scale. A strategy to bridge this gap has drawn upon the wider family of geophysical data, namely gravity and magnetic data, in conjunction with a conventional, broad, regional grid of two-dimensional (2D) seismic data. These data have been worked together to construct a basin scale framework into which 3D seismic data acquisition can be planned and the results interpreted.At the regional scale, satellite-derived gravity coverage has enabled the removal of the effects of Tertiary seafloor spreading, allowing structures on the northwest European continental margin to be viewed in context with the geology of East Greenland.At the basin scale, basinal elements have been identified and correlated among seismic, gravity, and magnetic data. Controlling faults have been mapped, and the timing of basin formation inferred from trend and geometry, with implications for source rock distribution.At the license block scale, the segmentation of basin margins has been revealed by high spatial resolution magnetic data with implications for both trapping potential and the control of sediment supply into the basins. The fusion of interpretations made from the different types of geophysical data creates a scale of observation range that stretches from tectonic plates to prospective structures. The resulting geological framework has sufficient scale overlap to relate immediately to the level of detail available from 3D seismic data. Moreover, the broader perspective may ensure that those seismic data are acquired in the correct part of the basin in the first place. P. 476


Author(s):  
Jesper Kresten Nielsen ◽  
Mikael Pedersen

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Kresten Nielsen, J., & Pedersen, M. (1998). Hydrothermal activity in the Upper Permian Ravnefjeld Formation of central East Greenland – a study of sulphide morphotypes. Geology of Greenland Survey Bulletin, 180, 81-87. https://doi.org/10.34194/ggub.v180.5090 _______________ Bituminous shales of the Ravnefjeld Formation were deposited in the subsiding East Greenland basin during the Upper Permian. The shales are exposed from Jameson Land in the south (71°N; Fig. 1) to Clavering Ø in the north (74°20′N) and have attracted considerable attention due to their high potential as hydrocarbon source rocks (Piasecki & Stemmerik 1991; Scholle et al. 1991; Christiansen et al. 1992, 1993a, b). Furthermore, enrichment of lead, zinc and copper has been known in the Ravnefjeld Formation on Wegener Halvø since 1968 (Lehnert-Thiel 1968; Fig. 1). This mineralisation was assumed to be of primary or early diagenetic origin due to similarities with the central European Kupferschiefer (Harpøth et al. 1986). Later studies, however, suggested base metal mineralisation in the immediately underlying carbonate reefs to be Tertiary in age (Stemmerik 1991). Due to geographical coincidence between the two types of mineralisation, a common history is a likely assumption, but a timing paradox exists. A part of the TUPOLAR project on the ‘Resources of the sedimentary basins of North and East Greenland’ has been dedicated to re-investigation of the mineralisation in the Ravnefjeld Formation in order to determine the genesis of the mineralisation and whether or not primary or early diagenetic base metal enrichment has taken place on Wegener Halvø, possibly in relation to an early period of hydrothermal activity. One approach to this is to study the various sulphides in the Ravnefjeld Formation; this is carried out in close co-operation with a current Ph.D. project at the University of Copenhagen, Denmark. Diagenetically formed pyrite is a common constituent of marine shales and the study of pyrite morphotypes has previously been successful from thermalli immature parts of elucidating depositional environment and thermal effects in the Alum Shale Formation of Scandinavia (Nielsen 1996; Nielsen et al. 1998). The present paper describes the preliminary results of a similar study on pyrite from thermally immature parts of the Ravnefjeld Formation which, combined with the study of textures of base metal sulphides in the Wegener Halvø area (Fig. 1), may provide an important step in the evaluation of the presence or absence of early thermal activity on (or below) the Upper Permian sea floor.


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