Conjugate, cataclastic deformation bands in the Lower Devonian Muth Formation (Tethyan Zone, NW India): evidence for pre-Himalayan deformation structures

The purpose of this study is to use the mechanisms of deformation band formation to help with interpreting the timing of phases of deformation in an area with a complex geological history. Deformation bands and zones of deformation bands are described from the quartzites of the Lower Devonian Muth Formation in the Pin Valley, NW Himalayas. Thin-section analyses show that the deformation bands in the Muth Formation formed early in the diagenetic history before porosity was lost. Deformation mechanisms involved cataclasis, translation, rotation of quartz grains and effective porosity reduction. The orientations of the deformation bands cannot be reasonably grouped with the orientations of faults related to Himalayan deformation in the Pin Valley. Additionally, the deformation bands are deformed by Eo-Himalayan (Eocene) folds, which in turn are cut by later faults. The later faults that cross-cut the Eo-Himalayan folds developed in the already-cemented Muth Formation at much higher temperature and pressure conditions by crystal plastic deformation mechanisms, indicated by quartz crystals with undulatory extinction, abundant kink bands, dislocation glide, elongated subgrains, slightly curved deformation lamellae and pronounced shape-preferred orientation. These two completely contrasting deformation mechanisms on the microstructural scale characterize two distinct fault sets that formed at different depths in the crust. Based on these differences, a pre-Himalayan origin of the deformation bands is concluded, thus representing a set of rare pre-Himalayan deformation structures. After unfolding to remove Eo-Himalayan crustal shortening, the orientation of the deformation bands and restored relative offsets of sedimentary bedding are most compatible with ∼ E–W-oriented shortening associated with N–S extension. The age of the deformation bands in the Muth Formation is bracketed by an early Devonian sedimentation age of the Muth Formation and a middle Cretaceous age of considerable cementation as deduced from compiled burial histories. Accepting a pre-middle Cretaceous age of the deformation bands, maximum conditions of about 80°C and 60 MPa lithostatic pressure during their formation are estimated from the amount of overburden during the middle Cretaceous. We suggest the deformation bands are a result of either the Neo-Tethys rifting event beginning in the early Carboniferous or the extension related to late Carnian/early Norian rapid subsidence, although a hitherto unknown deformation event cannot be excluded.

Download Full-text

Analysis of deformation bands associated with the Trachyte Mesa intrusion, Henry Mountains, Utah: implications for reservoir connectivity and fluid flow around sill intrusions

10.5194/se-2020-71 ◽

2020 ◽

Author(s):

Penelope I. R. Wilson ◽

Robert W. Wilson ◽

David J. Sanderson ◽

Ian Jarvis ◽

Kenneth J. W. McCaffrey

Keyword(s):

Fluid Flow ◽

Host Rock ◽

Deformation Band ◽

Seismic Structure ◽

Deformation Bands ◽

Hydrocarbon Reservoir ◽

Deformation Structures ◽

Porosity Reduction ◽

Igneous Intrusions ◽

Henry Mountains

Abstract. Shallow-level igneous intrusions are a common feature of many sedimentary basins, and there is increased recognition of the syn-emplacement deformation structures in the host rock that help to accommodate this magma addition. However, the sub-seismic structure and reservoir-scale implications of igneous intrusions remain poorly understood. The Trachyte Mesa intrusion is a small (~ 1.5 km2), NE–SW trending satellite intrusion to the Oligocene-age Mount Hillers intrusive complex in the Henry Mountains, Utah. It is emplaced within the highly porous, aeolian Entrada Sandstone Formation (Jurassic), producing a network of conjugate sets of NE–SW striking deformation bands trending parallel to the intrusion margins. The network was characterized by defining a series of nodes and branches, from which the topology, frequency, intensity, spacing, characteristic length, and dimensionless intensity of the deformation band traces and branches were determined. These quantitative geometric and topological measures were supplemented by petrological, porosity and microstructural analyses. Results show a marked increase in deformation band intensity and significant porosity reduction with increasing proximity to the intrusion. The deformation bands are likely to impede fluid flow, forming barriers and baffles within the Entrada reservoir unit. A corresponding increase in Y- and X- nodes highlights the significant increase in deformation band connectivity, which in turn will significantly reduce the permeability of the sandstone. This study indicates that fluid flow in deformed host rocks around igneous bodies may vary significantly from that in the undeformed host rock. A better understanding of the variability of deformation structures, and their association with intrusion geometry, will have important implications for industries where fluid flow within naturally fractured reservoirs adds value (e.g. hydrocarbon reservoir deliverability, hydrology, geothermal energy and carbon sequestration).

Download Full-text

Analysis of deformation bands associated with the Trachyte Mesa intrusion, Henry Mountains, Utah: implications for reservoir connectivity and fluid flow around sill intrusions

Solid Earth ◽

10.5194/se-12-95-2021 ◽

2021 ◽

Vol 12 (1) ◽

pp. 95-117

Author(s):

Penelope I. R. Wilson ◽

Robert W. Wilson ◽

David J. Sanderson ◽

Ian Jarvis ◽

Kenneth J. W. McCaffrey

Keyword(s):

Fluid Flow ◽

Host Rock ◽

Deformation Band ◽

Seismic Structure ◽

Deformation Bands ◽

Hydrocarbon Reservoir ◽

Deformation Structures ◽

Porosity Reduction ◽

Igneous Intrusions ◽

Henry Mountains

Abstract. Shallow-level igneous intrusions are a common feature of many sedimentary basins, and there is increased recognition of the syn-emplacement deformation structures in the host rock that help to accommodate this magma addition. However, the sub-seismic structure and reservoir-scale implications of igneous intrusions remain poorly understood. The Trachyte Mesa intrusion is a small (∼1.5 km2), NE–SW trending satellite intrusion to the Oligocene-age Mount Hillers intrusive complex in the Henry Mountains, Utah. It is emplaced within the highly porous, aeolian Entrada Sandstone Formation (Jurassic), producing a network of conjugate sets of NE–SW striking deformation bands trending parallel to the intrusion margins. The network was characterized by defining a series of nodes and branches, from which the topology, frequency, intensity, spacing, characteristic length, and dimensionless intensity of the deformation band traces and branches were determined. These quantitative geometric and topological measures were supplemented by petrological, porosity and microstructural analyses. Results show a marked increase in deformation band intensity and significant porosity reduction with increasing proximity to the intrusion. The deformation bands are likely to impede fluid flow, forming barriers and baffles within the Entrada reservoir unit. A corresponding increase in Y- and X-nodes highlights the significant increase in deformation band connectivity, which in turn will significantly reduce the permeability of the sandstone. This study indicates that fluid flow in deformed host rocks around igneous bodies may vary significantly from that in the undeformed host rock. A better understanding of the variability of deformation structures, and their association with intrusion geometry, will have important implications for industries where fluid flow within naturally fractured reservoirs adds value (e.g. hydrocarbon reservoir deliverability, hydrology, geothermal energy and carbon sequestration).

Download Full-text

Lacustrine Slope-Related Soft-Sediment Deformation Structures in the Cretaceous Gyeokpori Formation, Buan Area, SW Korea, and Volcanism-Induced Seismic Shocks as Their Possible Trigger

Minerals ◽

10.3390/min11070721 ◽

2021 ◽

Vol 11 (7) ◽

pp. 721

Author(s):

Ukhwan Byun ◽

A.J. (Tom) van Loon ◽

Kyoungtae Ko

Keyword(s):

Facies Analysis ◽

Deformation Mechanisms ◽

Volcanic Area ◽

Cohesive Sediments ◽

Soft Sediment ◽

Deformation Structures ◽

Sediment Deformation ◽

Soft Sediment Deformation ◽

Siliciclastic Rocks ◽

Sediment Layers

The Gyeokpori Formation in the Buan volcanic area primarily contains siliciclastic rocks interbedded with volcanoclastics. These sediments are characterized by a variety of soft-sediment deformation structures (SSDS). The SSDS in the Gyeokpori Formation are embedded in poorly sorted conglomerates; slump folds are also present in the formation. The deformation mechanisms and triggers causing the deformation are not yet clear. In the present study, the trigger of the SSDS in the Gyeokpori Formation was investigated using facies analysis. This included evaluation of the reworking process of both cohesive and non-cohesive sediments. The analysis indicates that the SSDS are directly or indirectly associated with the alternation of conglomerates and mud layers with clasts. These layers underwent non-cohesive and cohesive deformation, respectively, which promoted SSDS formation. The slump folds were controlled by the extent of cohesive and non-cohesive deformation experienced by the sediment layers in the slope environment. The SSDS deformation style and morphology differ, particularly in the case of reworking by slump activity. This study contributes to the understanding of lacustrine slope-related soft-sediment deformation structures.

Download Full-text

Limitations of soft-sediment deformation structures as indicator for paleo-earthquakes in formerly periglacial and glaciated areas

10.5194/egusphere-egu2020-5399 ◽

2020 ◽

Author(s):

Katharina Müller ◽

Jutta Winsemann ◽

Thomas Lege ◽

Thomas Spies ◽

Christian Brandes

Keyword(s):

Soft Sediment ◽

Deformation Bands ◽

Trigger Mechanism ◽

Deformation Structures ◽

Freeze And Thaw ◽

Potential Trigger ◽

Sediment Deformation ◽

Flame Structures ◽

Soft Sediment Deformation ◽

Trigger Mechanisms

During the last years many studies focused on soft-sediment deformation structures (SSDS) to identify past seismic events. However, in regions that were affected by glaciations and periglacial processes like northern and central Europe, the use of SSDS as paleo-earthquake indicator is challenging. Interpretations require great care. Earthquakes are only one possible trigger mechanism of many that can cause liquefaction and/or fluidization of sediments, which leads to the formation of e.g. sand volcanoes, clastic dykes, flame structures, or ball-and-pillow structures.SSDS triggered by seismic shaking are so-called seismites. Originally the term &#8216;seismites&#8217; was used by Sailacher (1969) and only referred to sediment beds that were deformed by earthquake-related shaking. Pleistocene seismites are described from former glaciated areas in Germany, Denmark, Sweden, Poland, Latvia, and Lithuania.However, ice-sheet loading, glaciotectonism as well as freeze and thaw processes in periglacial environments are also potential trigger mechanisms causing the formation of similar looking types of SSDS, which can be easily mistaken for seismites. Therefore, it is important to use a set of clear criteria to recognize seismites in the field.Extensive studies of Pleistocene sediments in northern Germany have shown that deformation bands are a suitable indicator for paleo-fault activity. Deformation bands that are developed close to the tip line of a fault in combination with e.g. sand volcanoes, clastic dykes, flame structures, or ball-and-pillow structures is the most robust indicator for paleo-earthquakes.&#160;References&#160;Seilacher, A. (1969). Fault-graded beds interpreted as seismites. Sedimentology, 13, 155-159.

Download Full-text

Description and origin of banded deformation structures. II. Rheology and the growth of banded perturbations

Canadian Journal of Earth Sciences ◽

10.1139/e77-217 ◽

1977 ◽

Vol 14 (11) ◽

pp. 2510-2523 ◽

Cited By ~ 124

Author(s):

P. R. Cobbold

Keyword(s):

Rheological Properties ◽

Strain Softening ◽

Shear Zones ◽

Progressive Deformation ◽

Kink Bands ◽

Natural Processes ◽

Deformation Structures ◽

Mechanical Explanation ◽

Deformation Hardening ◽

Deformation Stress

This paper offers a generalized mechanical explanation for the origin and development of bandlike deformation structures such as shear zones, mylonite zones, kink bands, 'pressure-solution' seams, extension gashes, and similar folds.Methods of continuum mechanics are used to examine permissible variations in strain rate, stress, and rheological properties across a region containing ideal banded perturbations. For bands to develop, the rheological properties must vary across the banding. The physical basis for this variation is a corresponding variation in microstructure or chemical composition, influenced in turn by finite deformation, stress, and temperature. Many rocks are likely to soften or harden during progressive deformation and these changes may be enhanced by thermal or other agents. Deformation softening (including strain softening and rotation softening) is a cause of instability and has two effects: first, the deformation tends to accelerate under constant stress; second, the deformation tends to become locally perturbed. Deformation hardening has compensatory effects.Banded perturbations do not appear spontaneously in a deforming rock, but evolve towards an ideal banded form by processes of nucleation and propagation. Evidence for these processes comes from theoretical analysis, experimental data, and observation of bandlike structures that have formed as a result of natural processes of deformation.

Download Full-text

Deformation of Polysynthetically Twinned (PST) Crystals of TiAl in Tension and Compression at Room Temperature

MRS Proceedings ◽

10.1557/proc-213-569 ◽

1990 ◽

Vol 213 ◽

Cited By ~ 2

Author(s):

H. Inui ◽

A. Nakamura ◽

M. Yamaguchi

Keyword(s):

Electron Microscope ◽

Room Temperature ◽

Tensile Axis ◽

Tensile Elongation ◽

Deformation Mechanisms ◽

Deformation Structures ◽

Room Temperature Ductility ◽

Tension And Compression

ABSTRACTPolysynthetically twinned (PST) crystals of TiAl have been grown and deformed in tension and compression at room temperature. A room temperature tensile elongation of 12.8% which is far larger than any other reported values of room temperature ductility was obtained for a specimen whose tensile axis is inclined at 51° to the lamellar boundaries. Deformation mechanisms of PST crystals of TiAl are discussed on the basis of the results of electron microscope observations of deformation structures.

Download Full-text

Axial-Compressive Behavior, Including Kink-Band Formation and Propagation, of Singlep-Phenylene Terephthalamide (PPTA) Fibers

Advances in Materials Science and Engineering ◽

10.1155/2013/329549 ◽

2013 ◽

Vol 2013 ◽

pp. 1-15 ◽

Cited By ~ 12

Author(s):

M. Grujicic ◽

S. Ramaswami ◽

J. S. Snipes ◽

R. Yavari ◽

C.-F. Yen ◽

...

Keyword(s):

Detrimental Effect ◽

Mechanical Response ◽

Topological Defects ◽

Kink Band ◽

Coarse Grained ◽

Computational Investigation ◽

Band Formation ◽

Longitudinal Tensile Strength ◽

Kink Bands

The mechanical response ofp-phenylene terephthalamide (PPTA) single fibers when subjected to uniaxial compression is investigated computationally using coarse-grained molecular statics/dynamics methods. In order to construct the coarse-grained PPTA model (specifically, in order to define the nature of the coarse-grained particles/beads and to parameterize various components of the bead/bead force-field functions), the results of an all-atom molecular-level computational investigation are used. In addition, the microstructure/topology of the fiber core, consisting of a number of coaxial crystalline fibrils, is taken into account. Also, following our prior work, various PPTA crystallographic/topological defects are introduced into the model (at concentrations consistent with the prototypical PPTA synthesis/processing conditions). The analysis carried out clearly revealed (a) formation of the kink bands during axial compression; (b) the role of defects in promoting the formation of kink bands; (c) the stimulating effects of some defects on the fiber-fibrillation process; and (d) the detrimental effect of the prior compression, associated with fiber fibrillation, on the residual longitudinal-tensile strength of the PPTA fibers.

Download Full-text

Influence of the Quartz Deformation Structures for the Occurrence of the Alkali–Silica Reaction

Materials ◽

10.3390/ma11091692 ◽

2018 ◽

Vol 11 (9) ◽

pp. 1692 ◽

Cited By ~ 2

Author(s):

Francieli Tiecher ◽

Renata Florindo ◽

Geilma Vieira ◽

Márcia Gomes ◽

Denise Dal Molin ◽

...

Keyword(s):

Atomic Scale ◽

Alkali Silica Reaction ◽

Deformation Bands ◽

Deformation Degree ◽

Deformation Structures ◽

Before And After ◽

Accelerated Mortar Bar Test ◽

High Alkalinity ◽

Mortar Bar ◽

Alkali Hydroxides

Defects in the crystalline structure of quartz facilitate the connection with the alkali hydroxides, since under a high alkalinity condition (e.g., in concrete), the Si-O bonds of quartz are easily broken. This study set out to investigate the influence of the deformation structures of quartz on its susceptibility to the alkali–silica reaction. A granite, a protomylonite, and a mylonite were selected for this study. Using optical microscopy, the quartz grains contained in these rocks were quantified and their texture characterized. The quartz samples extracted from the rocks were analyzed by magnetic nuclear resonance, to evaluate their potential for dissolving silica as well as changes in their atomic scale before and after the reaction with alkali hydroxides. These analyses were compared with the results of the accelerated mortar bar test. The study showed that the quartz with intense undulatory extinction and deformation bands denotes the most favorable condition to the development of the alkali–silica reaction. However, on an atomic scale, the slightly deformed grains were highly prone to react. Thus, in a high alkalinity condition, over a long period of time, any quartz tends to develop the alkali–silica reaction, regardless of the deformation degree of the grain.

Download Full-text

POROSITY AND PERMEABILITY OF RESERVOIRS AND CAPROCKS IN THE EROMANGA BASIN, SOUTH AUSTRALIA

The APPEA Journal ◽

10.1071/aj85020 ◽

1986 ◽

Vol 26 (1) ◽

pp. 202

Author(s):

D.I. Gravestock ◽

E.M. Alexander

Keyword(s):

Grain Size ◽

Gamma Ray ◽

Size Variation ◽

South Australia ◽

Clay Content ◽

Effective Porosity ◽

Overburden Pressure ◽

Porosity Reduction ◽

Porosity And Permeability ◽

Eromanga Basin

When effective porosity and permeability are measured at simulated overburden pressure, and grain size variation is taken into account, two distinct relationships are evident for Eromanga Basin reservoirs. Reservoirs in the Hutton Sandstone and Namur Sandstone Member behave such that significant porosity reduction can be sustained with retention of high permeability, whereas permeability of reservoirs in the Birkhead Formation and Murta Member is critically dependent on slight porosity variations. Logging tool responses are compared with core-derived data to show in particular the effects of grain size and clay content on the gamma ray, sonic, and density tools, where clay content is assessed from cation exchange capacity measurements. Sonic and density crossplots, constructed to provide comparison with a water-saturated 'reference' reservoir, are advantageous in comparing measured effective porosity from core plugs at overburden pressure with porosity calculated from logs. Gamma ray and sonic log responses of the Murta Member in the Murteree Horst area are clearly distinct from those of all other reservoirs, perhaps partly due to differences in mineralogy and shallower depth of burial compared with other formations.

Download Full-text