Interpretation of gravity and magnetic data from southwestern Newfoundland and their correlation with Lithoprobe East seismic lines 89-11 and 89-12

Several Newfoundland Appalachian terranes converge in the southwest corner of the island. The recent Lithoprobe East deep seismic reflection profiles imaged the crust along a transect across this area. In this paper, we present the gravity and magnetic data for the area and process them using shaded relief, horizontal and vertical gradient, upward continuation, and layer stripping techniques to interpret the more subtle features of the fields.Traditional two and one-half dimensional gravity and magnetic modelling is undertaken using constraints from the reflection data to develop a model of the crust in this region. The results from the processing are then used to interpret the crustal structure away from the seismic line.In general, we find that the major features on the gravity and magnetic anomaly maps can be explained by sources in the upper crust. The major faults in the area bound terranes that differ in potential field character. A minor change to the location of one terrane boundary is suggested. The rest correlate well with the geophysical data.

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Offshore extensions of the Avalon Zone of Newfoundland

Canadian Journal of Earth Sciences ◽

10.1139/e85-119 ◽

1985 ◽

Vol 22 (8) ◽

pp. 1163-1170 ◽

Cited By ~ 7

Author(s):

H. G. Miller ◽

A. K. Goodacre ◽

R. V. Cooper ◽

D. Halliday

Keyword(s):

Strong Correlation ◽

Sedimentary Basin ◽

Magnetic Data ◽

Two Dimensional ◽

Gravity And Magnetic ◽

Magnetic Modelling ◽

Dimensional Gravity ◽

Gravity And Magnetic Data ◽

Avalon Peninsula ◽

Block Faulting

Gravity and magnetic data from the nearshore region of the Avalon Zone of Newfoundland provide evidence of the nature of a sedimentary basin immediately east of the Avalon Peninsula. The data also suggest a strong correlation between the arcuate magnetic patterns of the offshore portion of the Avalon Zone and the Precambrian mafic volcanics mapped onshore. The offshore basin is interpreted to have been formed by Precambrian block faulting and subsequently filled by sediments derived from surrounding paleotopographic highs. Two-dimensional gravity and magnetic modelling results suggest the presence of mafic material beneath the modelled 9+ km of sediment in the basin.

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Automatic 3-D interpretation of potential field data using analytic signal derivatives

Geophysics ◽

10.1190/1.1444149 ◽

1997 ◽

Vol 62 (1) ◽

pp. 87-96 ◽

Cited By ~ 56

Author(s):

Nicole Debeglia ◽

Jacques Corpel

Keyword(s):

Signal Amplitude ◽

Vertical Gradient ◽

Analytic Signal ◽

Magnetic Data ◽

Practical Implementation ◽

Potential Field Data ◽

Gravity And Magnetic ◽

Second Derivatives ◽

Gravity And Magnetic Data ◽

Derivatives Of

A new method has been developed for the automatic and general interpretation of gravity and magnetic data. This technique, based on the analysis of 3-D analytic signal derivatives, involves as few assumptions as possible on the magnetization or density properties and on the geometry of the structures. It is therefore particularly well suited to preliminary interpretation and model initialization. Processing the derivatives of the analytic signal amplitude, instead of the original analytic signal amplitude, gives a more efficient separation of anomalies caused by close structures. Moreover, gravity and magnetic data can be taken into account by the same procedure merely through using the gravity vertical gradient. The main advantage of derivatives, however, is that any source geometry can be considered as the sum of only two types of model: contact and thin‐dike models. In a first step, depths are estimated using a double interpretation of the analytic signal amplitude function for these two basic models. Second, the most suitable solution is defined at each estimation location through analysis of the vertical and horizontal gradients. Practical implementation of the method involves accurate frequency‐domain algorithms for computing derivatives with an automatic control of noise effects by appropriate filtering and upward continuation operations. Tests on theoretical magnetic fields give good depth evaluations for derivative orders ranging from 0 to 3. For actual magnetic data with borehole controls, the first and second derivatives seem to provide the most satisfactory depth estimations.

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Crustal structure in the Campanian region (Southern Apennines, Italy) from potential field modelling

Scientific Reports ◽

10.1038/s41598-021-93945-8 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Y. Kelemework ◽

M. Milano ◽

M. La Manna ◽

G. de Alteriis ◽

M. Iorio ◽

...

Keyword(s):

Potential Field ◽

Carbonate Platform ◽

Vertical Gradient ◽

Magnetic Data ◽

Potential Field Data ◽

Gravity And Magnetic ◽

Significant Depression ◽

Mountain Chain ◽

Surrounding Areas ◽

Gravity And Magnetic Data

AbstractWe present a 3D model of the main crustal boundaries beneath the Campanian region and the onshore and offshore surrounding areas, based on high-resolution potential field data. Our main objective is the definition of the main structural interfaces in the whole Campanian region from gravity and magnetic data, thanks to their ability to define them on a regional and continuous way. The complex morphology of the Mesozoic carbonate platform, which is fundamental to constrain the top of geothermal reservoir, was reconstructed by inverting the vertical gradient of gravity. We assumed local information from seismic models and boreholes to improve the model. We modeled the deep crustal structures by spectral analysis of Bouguer gravity and magnetic data. The inferred depth estimates indicate a shallow crystalline basement below the Tyrrhenian crust and the Apulian foreland and a significant depression beneath the Bradanic foredeep. The map of the Moho boundary shows a NE-SE verging trough below the Southern Apennine chain and two pronounced uplifts beneath the foreland and the Tyrrhenian crust. We also estimated the depth to the magnetic bottom, showing a thick magnetic crust below the mountain chain and shallow depths where the crustal heat flow is high. The models were compared with seismic sections along selected profiles; a good agreement was observed, despite of some inherent lower resolution for the gravity modelling from spectral methods. The regional covering and the continuity of our estimated crustal interfaces make it a new and valid reference for further geological, geophysical and geothermal studies, especially in areas such as northern and eastern Campania, where there is an incomplete geophysical and geological information.

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3D constrained inversion of gravity and magnetic data to image basement and plutonic bodies: A case study from Dood Arale Basin, eastern Somaliland

Geophysics ◽

10.1190/geo2020-0578.1 ◽

2021 ◽

pp. 1-57

Author(s):

Mohammed Y. Ali ◽

Meixia Geng ◽

James Derek Fairhead ◽

Ahmed Adan

Keyword(s):

Gravity Anomalies ◽

Geothermal Gradient ◽

High Density ◽

Density Model ◽

Magnetic Data ◽

Airborne Gravity ◽

Near Surface ◽

Gravity And Magnetic ◽

Seismic Reflection Profiles ◽

Gravity And Magnetic Data

We have developed 3D inversion models derived from airborne gravity and magnetic data, which are constrained by seismic and well data, in eastern Somaliland. The density model reveals a northwest–southeast-trending basin, 125 km long and 25 km wide and called the Dood Arale Basin. The basin comprises two subbasins separated by a basement high and is infilled by up to 2500–3200 m of sediments. Smaller and shallower subbasins are also identified to the west of Lafaweyne and northeast of Dararweyne. The density model shows that the top basement in the platform areas is at approximately 1500–1700 m in depth and shallows to approximately 300 m at the Bur Anod, Hagraajin and Hagrin Ranges and northwest of Eil Afwein. The basement depths in these areas are more uncertain and could be deeper because they occur in areas of high gravity anomalies caused by a combination of near-surface high-density sediments and high-density plutonic bodies within the basement. The susceptibility model indicates that the basement consists of very weakly magnetized metasediments of the Inda Ad Complex intruded by three northeast–southwest-trending magnetic bodies with upper surfaces at depths of approximately 300–3000 m. These magnetic bodies are interpreted as plutonic complexes of similar age and composition to the Lower Cretaceous syenite intrusions outcropping at Gorei in the Shilah Madu Range. Seismic reflection profiles image the sedimentary sequences, but they do not clearly map the top basement or detect any of the plutonic bodies. The plutonic bodies could have controlled the location of the basin’s border faults and contributed to the high geothermal gradient recorded at the Faro Hills-1 well. The Upper Cretaceous Gumburo and Jesomma Formations in the basin could potentially have reached maturation close to and above the plutonic bodies within the center of the basin.

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