scholarly journals A fresh look at Gulf of Mexico tectonics: Testing rotations and breakup mechanisms from the perspective of seismically constrained potential-fields modeling and plate kinematics

2020 ◽  
Vol 8 (4) ◽  
pp. SS31-SS45
Author(s):  
Daniel Minguez ◽  
E. Gerald Hensel ◽  
Elizabeth A. E. Johnson
Keyword(s):  
Gulf Of Mexico ◽  
Seismic Data ◽  
Gravity Data ◽  
Seafloor Spreading ◽  
Plate Motion ◽  
Rock Properties ◽  
Satellite Gravity ◽  
Spreading Model ◽  
Breakup Mechanism ◽  
Mantle Exhumation

Interpretation of recent, high-quality seismic data in the Gulf of Mexico (GOM) has led to competing hypotheses regarding the basin’s rift to drift transition. Some studies suggest a fault-controlled mechanism that ultimately results in mantle exhumation prior to seafloor spreading. Others suggest voluminous magmatic intrusion accommodates the terminal extension phase and results in the extrusion of volcanic seaward dipping reflectors (SDRs). Whereas it has been generally accepted that the plate motions between the rift and drift phases of the GOM are nearly perpendicular to each other, it has not been greatly discussed if the breakup mechanism plays a role in accommodating the transition in plate motion. We have developed a plate kinematic and crustal architecture hypothesis to address the transition from rift to drift in the GOM. We support the proposition of a fault-controlled breakup mechanism, in which slip on a detachment between the crust and mantle may have exhumed the mantle. However, we stress that this mechanism is not exclusive of synrift magmatism, though it does imply that SDRs observed in the GOM are not in this case indicative of a volcanic massif separating attenuated continental and normal oceanic crust. We support our hypothesis through a geometrically realistic 2D potential field model, which includes a magnetic seafloor spreading model constrained by recent published seismic data and analog rock properties. The 2D model suggests that magnetic anomalies near the continent-ocean transition may be related to removal of the lower continental crust during a phase of hyperextension prior to breakup, ending in mantle exhumation. The kinematics of breakup, derived from recent satellite gravity data and constrained by our spreading model and the global plate circuit, suggests that this phase of hyperextension accommodated the change in plate motion direction and a diachronous breakup across the GOM.

scholarly journals Comparing global tomography-derived and gravity-based upper mantle density models

2020 ◽  
Vol 221 (3) ◽  
pp. 1542-1554 ◽  
Author(s):  
B C Root
Keyword(s):  
Seismic Tomography ◽  
Upper Mantle ◽  
Seismic Data ◽  
Gravity Data ◽  
Heterogeneous Data ◽  
Clear Correlation ◽  
Data Sets ◽  
Satellite Gravity ◽  
Similar Density ◽  
Similar Peak

SUMMARY Current seismic tomography models show a complex environment underneath the crust, corroborated by high-precision satellite gravity observations. Both data sets are used to independently explore the density structure of the upper mantle. However, combining these two data sets proves to be challenging. The gravity-data has an inherent insensitivity in the radial direction and seismic tomography has a heterogeneous data acquisition, resulting in smoothed tomography models with de-correlation between different models for the mid-to-small wavelength features. Therefore, this study aims to assess and quantify the effect of regularization on a seismic tomography model by exploiting the high lateral sensitivity of gravity data. Seismic tomography models, SL2013sv, SAVANI, SMEAN2 and S40RTS are compared to a gravity-based density model of the upper mantle. In order to obtain similar density solutions compared to the seismic-derived models, the gravity-based model needs to be smoothed with a Gaussian filter. Different smoothening characteristics are observed for the variety of seismic tomography models, relating to the regularization approach in the inversions. Various S40RTS models with similar seismic data but different regularization settings show that the smoothening effect is stronger with increasing regularization. The type of regularization has a dominant effect on the final tomography solution. To reduce the effect of regularization on the tomography models, an enhancement procedure is proposed. This enhancement should be performed within the spectral domain of the actual resolution of the seismic tomography model. The enhanced seismic tomography models show improved spatial correlation with each other and with the gravity-based model. The variation of the density anomalies have similar peak-to-peak magnitudes and clear correlation to geological structures. The resolvement of the spectral misalignment between tomographic models and gravity-based solutions is the first step in the improvement of multidata inversion studies of the upper mantle and benefit from the advantages in both data sets.

Gravity and Magnetic Methods

2000 ◽  
Author(s):  
Richard M. Carruthers ◽  
John D. Cornwell
Keyword(s):  
Large Scale ◽  
Gravity Data ◽  
Integrated Approach ◽  
Rock Properties ◽  
Magnetic Data ◽  
Satellite Gravity ◽  
Fully Integrated ◽  
Continental Shelves ◽  
Gravity And Magnetic ◽  
Gravity And Magnetic Data

Lateral variations in the density and magnetization of the rocks within the crust give rise to "anomalies" in the Earth's gravity and magnetic fields. These anomalies can be measured and interpreted in terms of the geology both in a qualitative sense, by mapping out trends and changes in anomaly style, and quantitatively, by creating models of the subsurface which reproduce the observed fields. Such interpretations are generally less definitive in themselves than the results from seismic surveys (see chapter 12), but the data are widely available and can provide information in areas where other methods are ineffective or have not been applied. As the different geophysical techniques respond to specific rock properties such as density, magnetization, and acoustic velocity, the results are complementary, and a fully integrated approach to data collection and interpretation is generally more effective than the sum of its parts assessed on an individual basis. Gravity and magnetic data have been acquired, at least to a reconnaissance scale, over most of the world. In particular, the release into the public domain of satellite altimetry information (combined with improved methods of data processing) means that there is gravity coverage to a similar standard for most of the offshore region to within about 50 km of the coast. Magnetic anomalies recorded from satellites provide global coverage, but the high altitude of the observations means that only large-scale features extending over many 10s of kilometers are delineated. Reconnaissance aeromagnetic surveys with flight lines 10-20 km apart provide a lateral anomaly resolution similar to that of the satellite gravity data. Oceanographic surveys undertaken by a variety of academic and research institutions are another valuable source of data in remote regions offshore which supplement and extend the more detailed coverage obtained over the continental shelves, for example, by oil companies in areas of hydrocarbon interest. Surveys over land vary widely in terms of acquisition parameters and quality, but some form of national compilation is available from many countries. A number of possible applications of the potential field (i.e., gravity and magnetic) data follow from the terms set out by UNCLOS. Paragraph 4(b) of article 76 states, "In the absence of evidence to the contrary, the foot of the continental slope is to be determined as the point of maximum change in the gradient at its base" (italics added).

Cenozoic gravity tectonics in the northern Gulf of Mexico induced by crustal extension. A new interpretation of multichannel seismic data

2008 ◽  
Vol 179 (2) ◽  
pp. 117-128 ◽  
Author(s):  
Claude Rangin ◽  
Xavier Le Pichon ◽  
Nicolas Flotté ◽  
Laurent Husson
Keyword(s):  
Gulf Of Mexico ◽  
Seismic Data ◽  
Gravity Data ◽  
Passive Margin ◽  
Lateral Motion ◽  
Crustal Extension ◽  
High Penetration ◽  
Crustal Thinning ◽  
New Interpretation ◽  
Multichannel Seismic Data

Abstract The Gulf of Mexico margin in Texas is one of the most impressive examples of starved passive margin gravity collapse systems. Growth faults developed upslope and are compensated down slope by toe folding and thrusting. On the basis of new multi-channel seismic data with high penetration (down to 11 s-twtt) we present evidences for deep crustal extension and rifting that have enhanced superficial sliding. This hypothesis is supported by a significant heat flow anomaly and crustal thinning independently deduced from gravity data. This Cenozoic rifting episode is tectonically linked to left lateral motion along the Rio Bravo fault, a reactivated branch of the Texas lineament.

Cooperative inversion of geophysical data

Geophysics ◽  
1988 ◽  
Vol 53 (1) ◽  
pp. 8-20 ◽  
Author(s):  
Larry R. Lines ◽  
Alton K. Schultz ◽  
Sven Treitel
Keyword(s):  
Seismic Data ◽  
Field Model ◽  
Gravity Data ◽  
Geophysical Data ◽  
Rock Properties ◽  
Model Parameters ◽  
Borehole Data ◽  
Geophysical Inversion ◽  
Sonic Logs ◽  
Cooperative Inversion

Geophysical inversion by iterative modeling involves fitting observations by adjusting model parameters. Both seismic and potential‐field model responses can be influenced by the adjustment of the parameters of the rock properties. The objective of this “cooperative inversion” is to obtain a model which is consistent with all available surface and borehole geophysical data. Although inversion of geophysical data is generally non‐unique and ambiguous, we can lessen the ambiguities by inverting all available surface and borehole data. This paper illustrates this concept with a case history in which surface seismic data, sonic logs, surface gravity data, and borehole gravity meter (BHGM) data are adequately modeled by using least‐squares inversion and a series of forward modeling steps.

3-D Seismic Mapping and Amplitude Analysis: A Gulf of Mexico Case History

1992 ◽  
Vol 10 (4-5) ◽  
pp. 259-280 ◽  
Author(s):  
Robert L. Kidney ◽  
Ronald S. Silver ◽  
H.A. Hussein
Keyword(s):  
Gulf Of Mexico ◽  
Seismic Data ◽  
Seismic Survey ◽  
Rock Properties ◽  
Amplitude Analysis ◽  
Seismic Amplitude ◽  
Energy Company ◽  
Amplitude Anomaly ◽  
Key Steps ◽  
Seismic Anomalies

Utilization of 3-D seismic data and Direct Hydrocarbon Indicators led to the successful drilling of appraisal and development wells in the Gulf of Mexico block South Timbalier 198 (ST 198). These seismic technologies, which are routinely used by Oryx Energy Company, significantly reduced the time and cost to appraise the ST 198 discovery. Based on 2-D seismic mapping, a Pliocene Lower Buliminella (L BUL) prospect was drilled in ST 198. Although the expected reservoir was not found, an Upper Buliminella (U BUL) gas sandstone was encountered. An appraisal well of the U BUL interval confirmed this discovery. Following the drilling of these two wells, it became apparent that the structural complexities and the seismic amplitude anomalies of the area could not be adequately resolved using the 2-D seismic grid. A 3-D seismic survey was shot to delineate the discovery and evaluate the remaining potential of the South Timbalier Block 198 (ST 198). Direct Hydrocarbon Indicators (DHIs), which are seismic anomalies resulting from the hydrocarbon effect on rock properties, are generally expected from these age sands. While the 3-D survey shows a seismic amplitude anomaly associated with the U BUL reservoir, the areal extent of the seismic anomaly did not match the findings of the two wells. A DHI study was performed to determine if this inconsistency could be explained and if the amplitude anomaly could be used in the well planning. The two key steps which confirmed that this amplitude anomaly is a DHI were properly calibrating the seismic data to the well control and determining the theoretical seismic response of the gas sandstones. The DHI study along with the 3-D mapping led to the successful development of the ST 198 U BUL reservoir and to setting up a successful adjacent fault block play. Finally, 3-D mapping also identified a L BUL trap updip from the original L BUL prospect which resulted in a successful drilling effort.

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