An Improved Impregnation Technique for Studying Structure of Unlithified Cohesive Sediments

Swartz, James F.; Lindsley‐Griffin, Nancy

doi:10.2973/odp.proc.sr.112.198.1990

Cited by 7 publications

(7 citation statements)

References 3 publications

(22 reference statements)

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“…Mineralogy (bulk and clay‐size fraction) of ∼6 cm 3 subsamples from each whole round core was determined following standard XRD methods. Thin sections for petrographic characterization were prepared following Swartz and Lindsley‐Griffin [1990].…”

Section: Methodsmentioning

confidence: 99%

Tectonic signatures in centimeter‐scale velocity‐porosity relationships of Costa Rica convergent margin sediments

Gettemy

Tobin

2003

J. Geophys. Res.

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[1] The Costa Rica convergent margin, investigated during Ocean Drilling Program Leg 170, offers a unique opportunity to compare the tectonic effects of rapid subduction on incoming oceanic sediments to their laterally equivalent underthrust counterparts and to terrestrially derived wedge materials. Elevated pressure laboratory measurements of ultrasonic compressional and shear wave velocity, and porosity, are used to examine the importance of tectonic, lithologic, and diagenetic controls on physical and elastic properties of sediments in these three key tectonic domains. Depositional and stress path histories of the three domains, for example, can be distinguished by (1) trends of in situ velocity-porosity (and derived measurements) correspondence and (2) the mechanical response of representative materials to isotropic consolidation. A compressional wave velocity-porosity model, critical for the application of seismic imaging to margin-wide physical property and mass balance estimates, is developed from the laboratory measurements and shown to be consistent with the information derived from LWD bulk density and migrated seismic reflection data. This consistency of the velocityporosity model over the large range of both frequency and length measurement scales is a key result, supporting the assertion that core and borehole physical property measurements can be extrapolated to larger domains. Finally, dewatering and overpressure effects, critical factors in subduction zone and fault process dynamics and increasingly common multiphase/converted wave imaging targets, are discussed in terms of laboratoryestimated in situ compressional and shear wave velocity relationships. INDEX TERMS:5114 Physical Properties of Rocks: Permeability and porosity; 8105 Tectonophysics: Continental margins and sedimentary basins (1212); 3022 Marine Geology and Geophysics: Marine sediments-processes and transport; KEYWORDS: subduction zones, elastic properties, dewatering Citation: Gettemy, G. L., and H. J. Tobin, Tectonic signatures in centimeter-scale velocity-porosity relationships of Costa Rica convergent margin sediments,

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Section: Methodsmentioning

confidence: 99%

Tectonic signatures in centimeter‐scale velocity‐porosity relationships of Costa Rica convergent margin sediments

Gettemy

Tobin

2003

J. Geophys. Res.

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“…Standard operating conditions were 15kV acceleration voltage and 20 nA beam current. For BSE imaging, samples were fi rst impregnated using the acetone-replacement method of Swartz and Lindsley-Griffi n (1990) and then polished and carbon coated. The acetone-replacement technique was used to avoid disruption of the sample texture, which would result if samples were allowed to desiccate prior to impregnation.…”

Section: Petrographic Analysismentioning

confidence: 99%

Diagenesis, sediment strength, and pore collapse in sediment approaching the Nankai Trough subduction zone

Spinelli

Mozley

Tobin

et al. 2007

Geological Society of America Bulletin

118

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A minor amount of opal cement inhibits consolidation of sediment approaching the Nankai Trough subduction zone at Ocean Drilling Program Sites 1173 and 1177. Secondary and backscattered electron images of sediments from Site 1173 reveal a low-density, silica phase (opal-CT) coating grain contacts. The grain-coating cement is more widespread in the upper Shikoku Basin facies than in the lower Shikoku Basin facies. Numerical models of opal-CT content display increases with depth through the cemented upper Shikoku Basin section. Once temperature increases above ~55 °C, the rate of opal-CT dissolution outpaces precipitation, the cement can no longer support the overburden, and the open framework of the sediment begins to collapse. Cementation followed by cement failure is consistent with observed anomalies in porosity, seismic velocities, and shear rigidity. Porosity is anomalously high and nearly constant near the base of the upper Shikoku Basin facies, whereas seismic velocity increases with depth in the same interval. Across the boundary between the upper Shikoku Basin facies and the lower Shikoku Basin facies, there are step decreases in porosity from ~60% to ~45%, P-wave velocity from ~1800 m/s to ~1650 m/s, and S-wave velocity from ~550 m/s to ~300 m/s. Similar cementation and porosity collapse may be important in other locations where heating of hemipelagic deposits, with minor amounts of opal, is suffi cient to trigger opal diagenesis.

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“…Partially lithified sediments were impregnated with epoxy and allowed to harden before being cut into thin sections. Impermeable unlithified sediments were hardened with a low-viscosity resin, using the techniques described by Swartz and Lindsley-Griffin (1990) and then were cut into thin sections 40 to 50 µm thick. A greater thickness of sections was necessary because soft sediments have a tendency to pluck and grind unevenly, even when impregnated.…”

Section: Preparation Of Thin Sectionsmentioning

confidence: 99%

Textures, Microstructures, and Lithologies of Japan Sea Sediments from the Lower Portion of Hole 799B, Leg 128

Griffin¹,

Lindsley‐Griffin²

1992

Proceedings of the Ocean Drilling Program

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Textures, microstructures, and major lithologies of samples from 750 to 1081 mbsf of Hole 799B, Leg 128, Japan Sea, were studied in 40 thin sections. The study provided evidence for the sequence of diagenetic mineralization for the lower portion where the sediments become well-lithified. The diagenetic sequence for the lower portion of Hole 799B revealed from crosscutting relationships in textures and structures is (1) hard, round, "D-phosphate" nodules and glauconite grains transported and deposited with the sediments; (2) "F-phosphate" streaks and pyrite framboids; (3) clay minerals; (4) rotation, flattening, and compaction; and (5) irregular glauconite grains. Fabric that has been defined by the subparallel to parallel optical orientation of clay minerals becomes more pronounced with increasing depth. Compaction enhances clay mineral fabric by flattening soft F-phosphate nodules, burrows, and microfossils (like the sponge Sagarites makiyama or Makiyama titanni).

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An Improved Impregnation Technique for Studying Structure of Unlithified Cohesive Sediments

Cited by 7 publications

References 3 publications

Tectonic signatures in centimeter‐scale velocity‐porosity relationships of Costa Rica convergent margin sediments

Tectonic signatures in centimeter‐scale velocity‐porosity relationships of Costa Rica convergent margin sediments

Diagenesis, sediment strength, and pore collapse in sediment approaching the Nankai Trough subduction zone

Textures, Microstructures, and Lithologies of Japan Sea Sediments from the Lower Portion of Hole 799B, Leg 128

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