Laramide structures and basement block faulting: Two examples from the Big Horn Mountains, Wyoming

Palmquist, John C.

doi:10.1130/mem151-p125

Cited by 14 publications

(7 citation statements)

References 6 publications

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“…Heim 1922;Ill & Work 1978;Palmquist 1978;Stearns & Stearns 1978). For instance, such thin-skinned tectonics have seldom been described from any of the great intracontinental rift systems.…”

mentioning

confidence: 99%

Extensional forced folding and décollement of the pre-rift series along the Rhine graben and their influence on the geometry of the syn-rift sequences

Maurin

Nivière

1999

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On the western margin of the Rhine graben, forced folding and d6collement of competent Dogger strata occurred during the latest Eocene-Early Oligocene (Priabonian) as a result of normal faulting in the basement. The Dogger series are represented by NNEstriking thick layers of oolitic limestones strongly disrupted by extensional structures and incipient boudinage. To the east, the overlying Priabonian (syn-rift) sequences exhibit divergent onlaps, steeply dipping intraformational unconformities and a general drag syncline geometry. These syn-depositional structures attest to a close control by the progressive tilting and normal dip-slip sliding of the Dogger strata. Interpretation of a shallow seismic reflection profile reveals that this tilting is related to an underlying master normal fault which dips 60-70 ~' to the east. This fault offsets the Variscan crystalline basement and the gently dipping Triassic cover by about 2 km. To be balanced, the structural arrangement requires the presence of a d~collement layer located between the top of the Triassic series and the Dogger series, corresponding to the Late Triassic incompetent gypsiferous clays and marls. The response of the competent Dogger to the imposed forced folding is through the development of a lai~ge-scale extensional syncline in the hangingwall of the master detachment, compensated by the development of a piggy-back half-graben in the footwall. In the light of this new interpretation, a mechanical hypothesis is proposed including a two-stage evolution model of extension and subsidence for the Rhine graben.

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“…Heim 1922;Ill & Work 1978;Palmquist 1978;Stearns & Stearns 1978). For instance, such thin-skinned tectonics have seldom been described from any of the great intracontinental rift systems.…”

mentioning

confidence: 99%

Extensional forced folding and décollement of the pre-rift series along the Rhine graben and their influence on the geometry of the syn-rift sequences

Maurin

Nivière

1999

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“…M.Sc. thesis, Texas A & M Univ., 1976;Palmquist, 1978;Stearns, 1978). This is illustrated in Figure 13.…”

Section: Geo 128mentioning

confidence: 93%

Possible forced folding in the Taurus–Zagros Belt of northern Iraq

Ameen¹

1991

Geol. Mag.

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The folds in the Taurus–Zagros Belt of northern Iraq have generally been considered to be decollement buckle folds. This implies the presence of a decollement horizon at or near the base of the sedimentary cover, the ‘Infra-Cambrian Hormuz Salt’ and a passive role of the Precambrian basement in the tectonic evolution of the folded belt. Structural, stratigraphic, geophysical and remote sensing evidence suggests that forced folding, due to faulting in the basement, has played a significant role in the development of many of the folds in this region. This is clear from the substantial evidence of basement faulting, the lack of any convincing evidence for the presence of an extensive and regional decollement horizon (i.e. the Hormuz Salt) between the basement and the cover rocks, and the geometries of the folds and related mesostructures. The study shows that in the Taurus Foothills Zone, the folds are short, oval in plan shape, and arranged in an en echelon pattern along two sets of dislocation zones in the basement. However, the folds in the Zagros Foothills Zone are longer, linear and arcuate in plan shape. Many of the studied folds show similar features to those observed in the Rocky Mountains, U.S.A.

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“…These faults often offset earlier-formed faults until they too deactivate and are offset, either by newly formed faults or by the propagating master fault (e.g. Palmquist, 1978; "Growth folds above propagating normal faults" by Coleman et al Patton et al, 1998;Sharp et al, 2000a;Berg and Skar, 2005;Egholm et al, 2007). These earlier faults, depending on their orientation and geometry, may even inhibit or promote the propagation of the underlying normal fault to the surface (Bonini et al, 2015).…”

Section: Secondary Structures In Growth Foldsmentioning

confidence: 99%

Growth folds above propagating normal faults

Coleman¹,

Duffy²,

Jackson³

2018

Preprint

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Growth folds above the upper tips of normal faults are ubiquitous in extensional settings, especially during the early phases of extension and in salt-rich basins. As slip accumulates on the underlying normal fault, the geometry and size of the fold changes. These changes reflect the dip, throw, displacement and propagation rate of the underlying normal fault, as well as the thickness and rheology of the overlying cover. These changes also have a marked impact on the architecture and distribution of synkinematic sediments, as well as the styles of secondary deformation accommodating strain within the growing fold. Here, we analyse a large dataset of natural, and physically- and numerically-modelled growth folds to: (i) characterise their diagnostic features; (ii) investigate the controls on their geometry, size and differences; and (iii) describe how they grow with increasing extensional strain. We demonstrate that larger fault throws and a thicker and weaker cover are associated with larger growth folds. In contrast, small fault throws as well as thin and strong brittle cover are associated with smaller growth folds. We show that the geometry and size of growth folds vary through time; the width (and thus, the wavelength) of the fold is established relatively early during fold growth, whereas fold amplitude increases gradually with increasing fault throw. Fold width and amplitude become increasingly similar during fold evolution, until the fold is breached by the underlying normal fault. We also derive a number of preliminary empirical relationships between readily observable structural and stratigraphic parameters in our dataset that may help estimate the geometry and size of poorly exposed (i.e. in the field) or imaged (i.e. in the subsurface) growth folds. In addition, we discuss how fault growth models (i.e. constant-length vs. propagating) may impact the three-dimensional evolution of growth folds. Finally, our work shows that growth folds are likely more common than previously thought. For example, although they are well-documented in areas characterised by weak, ductile cover strata and low strain rates, our dataset illustrates that growth folds may also occur in brittle, relatively strong rocks and in regions with high strain rates. However, the underlying controls on fold occurrence remain elusive.

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Laramide structures and basement block faulting: Two examples from the Big Horn Mountains, Wyoming

Cited by 14 publications

References 6 publications

Extensional forced folding and décollement of the pre-rift series along the Rhine graben and their influence on the geometry of the syn-rift sequences

Extensional forced folding and décollement of the pre-rift series along the Rhine graben and their influence on the geometry of the syn-rift sequences

Possible forced folding in the Taurus–Zagros Belt of northern Iraq

Growth folds above propagating normal faults

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