what an ichnofacies is o ichnofacies assemblage of trace fossils that provide

What an ichnofacies is o ichnofacies assemblage of

This preview shows page 4 - 5 out of 5 pages.

what an ichnofacies is o ichnofacies= assemblage of trace fossils that provide an indication of the conditions that their formative organisms inhabited 28. what are siliciclastic sedimentary rocks o sedimentary rocks composed mainly of silicate particles derived by the weathering breakdown of older rocks (into clasts) comprise ¾ of all sedimentary rocks in the geologic record important source rock and reservoirs 29. mudrock vs shale o mudrock= contains more than 50% mud (silt + clay), siliciclastic grains less than 0.063 mm (or 4phi) in size o shale= laminated mudrock 30. black shale definition, its source of carbon o dark-colored shale containing Organic Matter (OM)
Image of page 4

Subscribe to view the full document.

31. Sandstone: framework and matrix o Framework= sand-sized (1/16-2mm) grains o Matrix= smaller minerals grains present within interstitial pore space (<0.03mm) 32. Sandstone classification: Dott 1964 ternaary diagrams o two defining parameters: relative percentage of framework and matrix & composition of framework grains o four- component diagram: a ternary diagram showing relative volume of quartz, feldspar, and rock fragments, which are the end members of framework gains o an extra dimension for matrix volume 33. Sandstone maturity o Maturity is applied to sandstone in two different ways: Compositional maturity= relative abundance of stable (quarts) and unstable framework grains (feldspar, rock fragments) Textural maturity= relative abundance of matrix and the degree of rounding and sorting 34. Diagenesis: pressure and temperature range o Temperature: 0-200C o Pressure: 1-2000 bars 35. Diagenesis: shallow to deep burial differences o Shallow Sandstone at <0-10 m depth Under oxidizing condition iron oxide may be precipitated out as coatings Carbonates or evaporates may be precipitated out in high evaporation area Under reducing condition, pyrite may form cement Calcite cementation: source is biogenic carbonate= marine organisms composed of aragonite Compaction= significantly reduces porosity and bed thickness Mechanical/physical compaction= due to overburden stress (pressure); results in grain reorientation and grain breakage Chemical compaction= increased pressure at the contact point between grains increases the solubility of the grains at contact o Intermediate Sandstone at 2-3.5 km, 50-120C Onset of quartz cementation as temperature increase to 70-80C Initial quartz cement strengthens the sandstone, will effectively shut down further mechanical compaction Dissolution of smectite and precipitation of illite o Deep Sandstone at >3.5-4 km, >120C Dissolution of kaolinite and precipitation of illite Once quartz overgrowth has formed, quartz cementation does not stop until nearly all the porosity is lost 36. Diagenesis: mechanical/physical and chemical o Dissolution o Quartz cementation: stylolite
Image of page 5

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern

Ask Expert Tutors You can ask 0 bonus questions You can ask 0 questions (0 expire soon) You can ask 0 questions (will expire )
Answers in as fast as 15 minutes