Home

Tectonics (General)

29 Apr

2nd Edition: Geological Process-Based Forward Modeling AAPG Call For Abstracts Expires in 5 days

litutmMedium

View All Deadlines ...

Explorer Article By Barry Friedman

Array Unlocks Sub-Secrets

Going deeper: EarthScope’s USArray project is doing just that, by taking a CAT scan of the earth’s subsurface – and providing a better look of the crust and upper mantle beneath the United States.

Added on 01 February, 2013

Explorer Article By Louise Durham

Monterey Shale Continues to Tempt and Tease

It don’t come easy: The oil rich Monterey Shale has proved to be the biggest conventional resource provider in California, and it promises even more – but the formation’s complex geology is just as intimidating as its potential is huge.

Added on 01 February, 2013

Bulletin Discussion

Carbonate porosity creation by mesogenetic dissolution: Reality or illusion?: Reply

We do not dispute that the pores shown in the photomicrograph of figure 8G of Beavington-Penney et al. (2008; reproduced here as Figure 1) could have formed at least partly by poststylolite dissolution, but we do not agree that this photomicrograph constitutes evidence for porosity creation by mesogenetic dissolution in the El Garia Formation of offshore Tunisia. Our skepticism is based on two main considerations: (1) that the multiple possible origins of the pores shown in Figure 1 cannot be determined with any meaningful degree of objective certainty and (2) that Figure 1 appears to be unrepresentative of pore types in the El Garia Formation, based on comparison with numerous other published images from this unit.

Added on 31 January, 2013

Bulletin Article

Handling natural complexity in three-dimensional geomechanical restoration, with application to the recent evolution of the outer fold and thrust belt, deep-water Niger Delta

Volumetric restoration can provide crucial insights into the structural evolution of three-dimensional (3-D) petroleum systems. A major limitation to its widespread application is the need to include complex architectures and realistic mechanics such as flexural slip. We apply an implicit approach that allows for, including unconformities, thin and/or pinched-out layers in the models but that cannot explicitly localize slip along horizons. To take advantage of this approach while accounting for flexural slip in 3-D restoration, we investigate new geomechanical properties. We consider flexural slip folding as a result of stacked rigid and thin weak layers, which can be modeled using transversely isotropic properties. We compare restorations of an anticline using transversely isotropic properties, isotropic properties, and a stack of rigid isotropic layers with nonfrictional slip between the layers. Our results show that transversely isotropic properties reasonably approximate flexural slip folding. We use these new tools to model the evolution of a complex system located in the Niger Delta toe. The system includes a detachment fold, a fault-bend fold, and a structural wedge formed in series. Growth stratigraphy and erosional surfaces delimit the kinematics of deformation. Regional erosive surfaces, 3-D gradients of fault slip, and vertical variations in mechanical strength motivated the use of our new restoration techniques. Restoring two growth units results not only in reinforcing the interpretation that the area is behaving as a deforming thrust sheet at critical taper, but also in highlighting coeval activity on both the hinterland structures and the toe of the thrust belt.

Added on 31 December, 2012

Bulletin Article

Assessing the extent of carbonate deposition in early rift settings

Select lacustrine and marine depositional settings show a spectrum of styles of carbonate deposition and illustrate the types of carbonates, with an emphasis on microbialites and tufa, to be expected in early rift settings. Early rift lake examples examined in this review article are all from East Africa: Lakes Turkana, Bogoria, Natron and Magadi, Manyara, and Tanganyika. Other lake examples include four from the western United States (Great Salt Lake and high lake level Lake Bonneville, Mono Lake and high lake level Russell Lake, Pyramid Lake and high lake level Lake Lahontan, and Searles Lake) and two from Australia (Lakes Clifton and Thetis). Marine basin examples are the Hamelin Pool part of Shark Bay from Australia (marginal marine) and the Red Sea (marine rift). Landsat images and digital elevation models for each example are used to delineate present and past lake-basin margins based on published lake-level elevations, and for some examples, the shorelines representing different lake levels can be compared to evaluate how changes in size, shape, and lake configuration might have impacted carbonate development. The early rift lakes show a range of characteristics to be expected in lacustrine settings during the earliest stages of continental extension and rifting, whereas the Red Sea shows well advanced rifting with marine incursion and reef–skeletal sand development. Collectively, the lacustrine examples show a wide range of sizes, with several of them being large enough that they could produce carbonate deposits of potential economic interest. Three of the areas—Great Salt Lake and high lake level Lake Bonneville, Pyramid Lake and high lake level Lake Lahontan, and the Red Sea—are exceedingly complex in that they illustrate a large degree of potential depositional facies heterogeneity because of their size, irregular pattern, and connectivity of subbasins within the overall basin outline.

Added on 31 December, 2012

Bulletin Article

Subsidence controls on foreland basin development of northwestern offshore Cuba, southeastern Gulf of Mexico

We reviewed the tectonostratigraphic evolution of the Jurassic–Cenozoic collision between the North American and the Caribbean plate using more than 30,000 km (18,641 mi) of regional two-dimensional (2-D) academic seismic lines and Deep Sea Drilling Project wells of Leg 77. The main objective is to perform one-dimensional subsidence analysis and 2-D flexural modeling to better understand how the Caribbean collision may have controlled the stratigraphic evolution of the offshore Cuba region. Five main tectonic phases previously proposed were recognized: (1) Late Triassic–Jurassic rifting between South and North America that led to the formation of the proto-Caribbean plate; this event is interpreted as half grabens controlled by fault family 1 as the east-northeast–south-southwest–striking faults; (2) Middle–Late Jurassic anticlockwise rotation of the Yucatan block and formation of the Gulf of Mexico; this event resulted in north-northwest–south-southeast–striking faults of fault family 2 controlling half-graben structures; (3) Early Cretaceous passive margin development characterized by carbonate sedimentation; sedimentation was controlled by normal subsidence and eustatic changes, and because of high eustatic seas during the Late Cretaceous, the carbonate platform drowned; (4) Late Cretaceous–Paleogene collision between the Caribbean plate, resulting in the Cuban fold and thrust belt province, the foreland basin province, and the platform margin province; the platform margin province represents the submerged paleoforebulge, which was formed as a flexural response to the tectonic load of the Great Arc of the Caribbean during initial Late Cretaceous–Paleocene collision and foreland basin development that was subsequently submerged during the Eocene to the present water depths as the arc tectonic load reached the maximum collision; and (5) Late Cenozoic large deep-sea erosional features and constructional sediment drifts related to the formation of the Oligocene–Holocene Loop Current–Gulf Stream that flows from the northern Caribbean into the Straits of Florida and to the north Atlantic.

Added on 31 December, 2012

Explorer President’s Column By Ted Beaumont

'Communities' Concept Starts to Grow

One of the AAPG Executive Committee’s priorities during the first five months of this fiscal year has been to study the Association’s science program with the goal of creating new conduits for generating and disseminating scientific content.

Added on 01 December, 2012

Explorer Emphasis Article By Louise Durham

Geosteering Keeps Drillers On the Right Track

It’s all about staying on target: Technological advances are helping to make geosteering an increasingly valuable tool for geologists involved in horizontal wells.

Added on 01 December, 2012

Explorer Emphasis Article By David Brown

Oklahoma Geologists are Basement-Bound

A new well in Oklahoma may be the most historic and geologically interesting project in the entire country – and for a bonus, it may involve a new helium province.

Added on 01 December, 2012

Explorer Article By Susan Eaton

Scientists Will Explore a Frozen Classroom

One more time: The AAPG Foundation’s “explorer-in-residence,” Susan Eaton, is returning to Antarctica again on a scientific expedition to study the geology and the climate found at the Bottom of the World.

Added on 01 December, 2012

DL Abstract By John Suppe

Probing What Makes the Crust Strong (or Weak): Insight from Boreholes, Earthquakes, Active Fault Systems, and Toy Models

For well over a century there have been conflicting indications of the strength of the crust and of faults and what controls them. Much of our ignorance comes quite naturally from the general inaccessibility of the crust to measurement--in contrast with our understanding of the atmosphere, which is much more accessible to observation as well as more rapidly changing. Crustal strength is best understood in deforming sedimentary basins where the petroleum industry has made great contributions, particularly in deforming petroleum basins because of the practical need to predict. In this talk we take a broad look at key issues in crustal strength and deformation and what we can learn from boreholes, earthquakes, active fault systems, and toy models.

Request a visit from John Suppe!

Added on 14 September, 2023

VG Abstract By Juan I. Soto

Salt versus Shales in Continental Margins and Orogens

In comparison with the known boundary conditions that promote salt deformation and flow in sedimentary basins, the processes involved with the mobilization of clay-rich detrital sediments are far less well established. This talk will use seismic examples in different tectonic settings to document the variety of shale geometries that can be formed under brittle and ductile deformations.

Request a visit from Juan I. Soto!

Added on 26 June, 2019

DL Abstract By Kurt W. Rudolph

Tectonic Controls on Source Rock Deposition

While there are many habitats that are associated with the deposition of organic-rich marine and lacustrine source rocks, one important pathway is linked to the onset of increased basin subsidence associated with major tectonic events. A key aspect is that this subsidence is spatially variable, with the uplift of basin flanks contemporaneous with the foundering of the basin center, resulting in a steeper basin profile.

Request a visit from Kurt W. Rudolph!

Added on 14 September, 2023

Tectonics (General)

Related Interests

See Also ...

STAY CONNECTED: