Lithospheric flexure and the evolution of sedimentary basins

1982 ◽  
Vol 305 (1489) ◽  
pp. 249-281 ◽  
Keyword(s):  
Gravity Anomalies ◽  
Sedimentary Basins ◽  
Oceanic Lithosphere ◽  
Oceanic Islands ◽  
Geological Time ◽  
Lithospheric Flexure ◽  
Free Air ◽  
Apparent Decrease ◽  
Basin Formation ◽  
Free Air Gravity

The sediments that have accumulated in sedimentary basins during geological time represent a load on the lithosphere that should respond by flexure. Simple elastic and viscoelastic (Maxwell) plate models have been used to examine quantitatively the contribution of flexure to basin formation. The models have been used to predict the stratigraphy and gravity anomalies associated with basins for different thermal and loading histories. The predictions of the models have been compared with observed stratigraphy and free-air gravity anomalies from interior and cratonic basins. The best overall fit to the observations is for an elastic plate model in which the flexural strength of the lithosphere increases with age. A similar model has recently been used successfully to explain observations from continental margin basins, oceanic islands and seamounts, and deep-sea trench - outer rise systems. This model explains the increase in the overall width of basins during their evolution as well as the stratigraphy of the basin edges. The apparent decrease in the widths of some basins through time can be explained by the model if sediment deposition is followed by erosion of the basin and its edges. The models results suggest that the flexural properties of continental and oceanic lithosphere are generally similar and that flexure is an important factor to consider in backstripping studies in which the tectonic subsidence of a basin is isolated and stratigraphic studies in which relative changes of sea level are estimated.

5. Gravity and the figure of the Earth

2018 ◽  
pp. 69-91
Author(s):  
William Lowrie
Keyword(s):  
Accurate Determination ◽  
Measurement Techniques ◽  
Gravity Anomalies ◽  
Dynamic Processes ◽  
The Core ◽  
The Earth ◽  
Free Air ◽  
Figure Of The Earth ◽  
Free Air Gravity

‘Gravity and the figure of the Earth’ discusses the measurement of gravity and its variation at the Earth’s surface and with depth. Gravity is about 0.5 per cent stronger at the poles than at the equator and it first increases with depth until the core–mantle boundary and then sinks to zero at the Earth’s centre. Using satellites to carry out geodetic and gravimetric observations has revolutionized geodesy, creating a powerful geophysical tool for observing and measuring dynamic processes on the Earth. The various measurement techniques employed fall in two categories: precise location of a position on the Earth (such as GPS) and accurate determination of the geoid and gravitational field. Bouguer and free-air gravity anomalies and isostasy are explained.

Empirical Determination of the Gravity Anomaly Covariance Function in Mountainous Areas

1980 ◽  
Vol 34 (3) ◽  
pp. 251-264 ◽  
Author(s):  
Gerard Lachapelle ◽  
K. P. Schwarz
Keyword(s):  
Gravity Anomaly ◽  
Covariance Function ◽  
Physical Geodesy ◽  
Gravity Anomalies ◽  
Mountainous Areas ◽  
The North ◽  
Regression Parameters ◽  
Free Air ◽  
Vening Meinesz ◽  
Free Air Gravity

An evaluation of the empirical gravity anomaly covariance function using over 95 000 surface gravity anomalies in the North American Western Cordillera was carried out. A regression analysis of the data exhibits a strong and quasi-linear correlation of free air gravity anomalies with heights. This height correlation is removed from the free air anomalies prior to the numerical evaluation of the gravity anomaly covariance function. This covariance function agrees well with that evaluated previously by the authors for the remainder of Canada. A possible use for such a covariance function of ‘height independent’ gravity anomalies in mountainous areas is described. First, the height independent gravity anomaly at a point of known height is evaluated by least squares prediction using neighboring measured height independent gravity anomalies. Secondly, the part caused by the height correlation is calculated using linear regression parameters estimated previously and added to the predicted height independent gravity anomaly to obtain a predicted standard free air anomaly. This technique can be used to densify the coverage of free air anomalies for subsequent use in integral formulas of physical geodesy, e.g., those of Stokes and Vening Meinesz. This method requires that point topographic heights be given on a grid.

Free air gravity anomalies over the oceans from Seasat and GEOS 3 altimeter data

Eos ◽  
1987 ◽  
Vol 68 (2) ◽  
pp. 17 ◽  
Author(s):  
G. Balmino ◽  
B. Moynot ◽  
M. Sarrailh ◽  
N. Valès
Keyword(s):  
Gravity Anomalies ◽  
Altimeter Data ◽  
Free Air ◽  
Free Air Gravity

Gravity and Deep Structure of the Continental Margin of Banks Island and Mackenzie Delta

1975 ◽  
Vol 12 (3) ◽  
pp. 378-394 ◽  
Author(s):  
L. W. Sobczak
Keyword(s):  
Continental Margin ◽  
Coastal Plain ◽  
Deep Structure ◽  
Gravity Anomalies ◽  
Sedimentary Basins ◽  
Drill Hole ◽  
The Arctic ◽  
Mackenzie Delta ◽  
Arctic Coastal Plain ◽  
Free Air Gravity

Regional and deep structure supported by drill hole, gravity, and seismic evidence is interpreted along five profiles—one across the Mackenzie Delta and four across the continental margin. Isostatic compensation has reduced the gravity effect of most structures but gravity anomalies are still sufficient to outline two major sedimentary basins—one very extensive and thick (>10 km) underlying the continental margin and Mackenzie Delta and the other narrow and shallow east and southeast of the Arctic Coastal Plain. A basement ridge separating these basins along the eastern side of the Arctic Coastal Plain is outlined by a trend of relative gravity highs.An arcuate belt of prominent elliptically-shaped free air gravity highs (peak values >100 mgal) over the continental break outlines an uncompensated region of mass excesses. These mass excesses are explained by pro-grading wedges (>2 km thick) of Quaternary and possibly Tertiary sediments that have displaced seawater and act as a load on the crust rather than by the alternative concepts of an uncompensated ridge or high density material in the basement.

Sea floor topography modeling by cumulating different types of gravity information

2020 ◽  
Author(s):  
Lucia Seoane ◽  
Benjamin Beirens ◽  
Guillaume Ramillien
Keyword(s):  
New England ◽  
Gravity Data ◽  
Gravity Anomalies ◽  
Geoid Height ◽  
Extended Kalman Filtering ◽  
Sea Floor ◽  
Single Beam ◽  
Free Air ◽  
Free Air Gravity ◽  
Great Meteor Seamount

<p>We propose to cumulate complementary gravity data, i.e. geoid height and (radial) free-air gravity anomalies, to evaluate the 3-D shape of the sea floor more precisely. For this purpose, an Extended Kalman Filtering (EKF) scheme has been developed to construct the topographic solution by injecting gravity information progressively. The main advantage of this sequential cumulation of data is the reduction of the dimensions of the inverse problem. Non linear Newtonian operators have been re-evaluated from their original forms and elastic compensation of the topography is also taken into account. The efficiency of the method is proved by inversion of simulated gravity observations to converge to a stable topographic solution with an accuracy of only a few meters. Real geoid and gravity data are also inverted to estimate bathymetry around the New England and Great Meteor seamount chains. Error analysis consists of comparing our topographic solutions to accurate single beam ship tracks for validation.</p>

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