Deformation Patterns in Western Offshore Libya: Partial Decoupling of Strike-Slip and Salt Tectonics

The Frade field, located within the Campos Basin in the southeastern Brazilian margin, is a key oil field that produces from Oligo-Miocene turbidite reservoirs that derived their structural positioning due to the presence of an underlying salt diapir. The evolution of the Frade salt structure was examined using well data, selected 2D lines, and a 3D volume that were interpreted in detail focusing on the Aptian evaporite interval and its influence on the overburden. Analysis of the salt-sediment interaction indicated a complex deformation history that included five main stages of deformation, some assisted by tectonic reactivation episodes. (1) Post-Albian reactivation of a nearby north–northwest-south–southeast basement fault caused the Albian carbonate interval to fault, forming a west–northwest-east–southeast shear zone with a dextral strike-slip component. This movement initiated thin-skinned tectonics that offset the Albian carbonates and formed a pull-apart basin that accommodated a thick Late Cretaceous interval, which weakened the overburden and allowed for the initial formation of the Frade salt diapir. (2) Renewed diapir growth thickened and redistributed the Cenomanian-Maastrichtian sedimentary package proximal to the Frade salt anticline. (3) An initial and localized collapse of the Frade salt anticline occurred during early Paleogene extension. (4) Paleogene shortening caused the salt to flow, resulting in salt withdrawal in the southeast and diapir rejuvenation near its present-day apex, forming several inversion structures. In addition, the Paleogene shortening resulted in a low-relief anticlinal structure that rotated the turbidites into geometries favoring hydrocarbon accumulation. (5) A return to an extensional regime occurred during the late Oligocene/early Miocene. The results of this study provide a new insight into the development of strike-slip salt tectonic structures and show for the first time within the Campos Basin an Albian-level pull-apart basin that formed in association with salt tectonics.

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New evidence for Cretaceous strike-slip faulting in the United States Cordillera and implications for terrane-displacement, deformation patterns, and plutonism

American Journal of Science ◽

10.2475/ajs.301.2.150 ◽

2001 ◽

Vol 301 (2) ◽

pp. 150-181 ◽

Cited By ~ 54

Author(s):

S. J. Wyld

Keyword(s):

United States ◽

The United States ◽

Strike Slip ◽

Deformation Patterns ◽

New Evidence

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Geometric Variation in the Surface Rupture of the 2018 Mw7.5 Palu Earthquake from Subpixel Optical Image Correlation

Remote Sensing ◽

10.3390/rs12203436 ◽

2020 ◽

Vol 12 (20) ◽

pp. 3436

Author(s):

Chenglong Li ◽

Guohong Zhang ◽

Xinjian Shan ◽

Dezheng Zhao ◽

Xiaogang Song

Keyword(s):

Shear Strain ◽

Surface Deformation ◽

Horizontal Displacement ◽

Strike Slip ◽

Image Correlation ◽

Displacement Fields ◽

Surface Rupture ◽

The North ◽

Deformation Patterns ◽

Geometric Variation

We obtained high-resolution (10 m) horizontal displacement fields from pre- and post-seismic Sentinel-2 optical images of the 2018 Mw7.5 Palu earthquake using subpixel image correlation. From these, we calculated the curl, divergence, and shear strain fields from the north-south (NS) and east-west (EW) displacement fields. Our results show that the surface rupture produced by the event was distributed within the Sulawesi neck (0.0974–0.6632°S) and Palu basin (0.8835–1.4206°S), and had a variable strike of 313.0–355.2° and strike slip of 2.00–6.62 m. The NS and EW displacement fields within the Palu basin included fine-scale displacements in both the near- and far-fault, the deformation patterns included a small restraining bend (localized shortening), a distributed rupture zone, and a major releasing bend (net extension) from the curl, divergence, and shear strain. Surface rupture was dominated by left-lateral strike-slip from initiation to termination, with a localized normal slip component peaking at ~3.75 m. The characteristics and geometric variation of the ruptured fault controlled both the formation of these surface deformation patterns and sustained supershear rupture.

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