Origin and enhancement of gravity and magnetic signatures of the continental‐oceanic boundary (COB): examples from West Africa Passive Margin

2008 ◽  
Author(s):  
Serguei Goussev ◽  
Gordon Shields ◽  
Jeff Rowe ◽  
Afif Saad
Keyword(s):  
West Africa ◽  
Passive Margin ◽  
Gravity And Magnetic ◽  
Magnetic Signatures

scholarly journals Evidence of Lithospheric Boudinage in the Grand Banks of Newfoundland from Geophysical Observations

Geosciences ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 55
Author(s):  
Malcolm D. J. MacDougall ◽  
Alexander Braun ◽  
Georgia Fotopoulos
Keyword(s):  
Passive Margin ◽  
Eastern Canada ◽  
Grand Banks ◽  
Long Wavelength ◽  
Passive Margins ◽  
Multi Stage ◽  
Crustal Thinning ◽  
Gravity And Magnetic ◽  
Magnetic Signatures ◽  
Seismic Sections

The evolution of the passive margin off the coast of Eastern Canada has been characterized by a series of rifting episodes which caused widespread extension of the lithosphere and associated structural anomalies, some with the potential to be classified as a result of lithospheric boudinage. Crustal thinning of competent layers is often apparent in seismic sections, and deeper Moho undulations may appear as repeating elongated anomalies in gravity and magnetic surveys. By comparing the similar evolutions of the Grand Banks and the Norwegian Lofoten-Vesterålen passive margins, it is reasonable to explore the potential of the same structures being present. This investigation supplements our knowledge of analogous examples in the Norwegian Margin and the South China Sea with a thorough investigation of seismic, gravity and magnetic signatures, to determine that boudinage structures are evident in the context of the Grand Banks. Through analysis of geophysical data (including seismic, gravity and magnetic observations), a multi-stage boudinage mechanism is proposed, which is characterized by an upper crust short-wavelength deformation ranging from approximately 20–80 km and a lower crust long-wavelength deformation exceeding 200 km in length. In addition, the boudinage mechanism caused slightly different structures which are apparent in the block geometry and layeredness. Based on these results, there are indications that boudinage wavelength increases with each successive rifting phase, with geometry changing from domino style to a more shearband/symmetrical style as the scale of deformation is increased to include the entire lithosphere.

scholarly journals The hidden sedimentary basin underneath the Quaternary volcanic unit in Bogor and Kendeng area

2021 ◽  
Vol 47 (2) ◽  
pp. 25-47
Author(s):  
Erlangga Septama ◽  
C. Prasetyadi ◽  
A Abdurrokhim ◽  
T. Setiawan ◽  
P.D. Wardaya ◽  
...  
Keyword(s):  
Oil And Gas ◽  
Sediment Supply ◽  
Passive Margin ◽  
Magnetic Data ◽  
Rock Samples ◽  
Petroleum Systems ◽  
The North ◽  
Gravity And Magnetic ◽  
Gravity And Magnetic Data ◽  
East West

The Java Island is an active volcanic arc that experiences several volcanism episodes, which gradually changes from South to North from the Late Oligocene to Pleistocene, following the subduction of the Australian plates underneath the Eurasian plates. During the Eocene, the southern and northern part of Java was connected as one passive margin system with the sediment supply mainly comes from Sundaland in the north.  The compressional tectonics creates a flexural margin and a deep depression in the central axis of Java Island and acts as an ultimate deep-sea depocenter in the Neogene period. In contrast to the neighboring Northwest and Northeast Java Basins in the Northern edges of Java Island, the basin configuration in the East-West trending depression in median ranges of Java (from Bogor to Kendeng Troughs) are visually undetected by seismic due to the immense Quaternary volcanic eruption covers.Five focused window areas are selected for this study. A total of 1,893 Km sections, 584 rock samples, 1569 gravity and magnetic data, and 29 geochemical samples (rocks, oil, and gas samples) were acquired during the study. Geological fieldwork was focused on the stratigraphic unit composition and the observable features of deformation products from the outcrops. Due to the Paleogene deposit exposure scarcity in the Central-East Java area, the rock samples were also collected from the mud volcano ejected materials in the Sangiran Dome.The distinct subsurface configuration differences between Bogor and Kendeng Troughs are mainly in the tectonic basement involvement and the effect of the shortening on the formerly rift basin. Both Bogor and Kendeng Troughs are active petroleum systems that generate type II /III Kerogen typical of reduction zone organic material derived from transition to the shallow marine environment. The result suggests that these basins are secular from the neighboring basins with a native petroleum system specific to the palaeogeographical condition during the Paleogene to Neogene periods where the North Java systems (e.g., Northwest and Northeast Java Basin) was characterized by oxidized terrigenous type III Kerogen.

Gravity and magnetic signatures of the Ackley Granite Suite, southeastern Newfoundland: implications for magma emplacement

1989 ◽  
Vol 26 (12) ◽  
pp. 2697-2709 ◽  
Author(s):  
H. G. Miller ◽  
J. Tuach
Keyword(s):  
Gravity Anomaly ◽  
Magma Chamber ◽  
Volcanic Rocks ◽  
Gravity Survey ◽  
Bouguer Gravity ◽  
Density Data ◽  
Bouguer Gravity Anomaly ◽  
Gravity And Magnetic ◽  
Magnetic Signatures ◽  
Granite Suite

A detailed gravity survey (255 stations over an area of 3000 km2) over the posttectonic, Devonian, Ackley Granite Suite in southeastern Newfoundland suggests that a set of northwest-trending geophysical lineations, interpreted as faults, controlled the bottom morphology of the magma chamber during emplacement.The main negative Bouguer gravity anomaly over the Ackley Granite Suite trends in a north–south direction across the trace of the Dover – Hermitage Bay Fault, the boundary between the Gander and Avalon terranes. Inversion of the gravity and density data indicates that the thickness of the granite suite varies between 2 and 8 km.Magnetic interpretation and modelling suggest that the southeast portion of the suite is underlain by mafic volcanic rocks typical of the Avalon Terrane. The magnetically determined depth to the top of these is consistent with that calculated from the gravity data.The combined geophysical models are indicative of a process of megablock stoping in which large crustal blocks were displaced downwards in midcrustal regions to permit the emplacement of what is now the Ackley Granite Suite and associated plutons.

scholarly journals Gravity and Magnetic Signatures of Different Types of Spreading at the Mid-Atlantic Ridge

2018 ◽  
Author(s):  
Gabriella Alodia ◽  
Chris Green ◽  
Andrew McCaig ◽  
Douglas Paton ◽  
Simon Campbell
Keyword(s):  
Gravity And Magnetic ◽  
Different Types ◽  
Magnetic Signatures ◽  
Mid Atlantic Ridge

U-shaped slope gully systems and sediment waves on the passive margin of Gabon (West Africa)

2013 ◽  
Vol 337 ◽  
pp. 80-97 ◽  
Author(s):  
Lidia Lonergan ◽  
Nur Huda Jamin ◽  
Christopher A.-L. Jackson ◽  
Howard D. Johnson
Keyword(s):  
West Africa ◽  
Passive Margin ◽  
Sediment Waves
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