Lecture-9_diagenesis - Diagenesis Lithification of...

Info icon This preview shows pages 1–9. Sign up to view the full content.

View Full Document Right Arrow Icon
Click to edit Master subtitle style 11 Lithification is the conversion of unconsolidated sediments into rock Diagenesis & Lithification of Sedimentary Deposits Diagenesis is any physical, chemical or biological alteration of sediments after its initial deposition and during and after its lithification The main results of diagenesis are : 1) Lithification, 2) Reduction of primary porosity, and 3) Production of secondary porosity Reading Assignment: Boggs, Chapter 5
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Click to edit Master subtitle style 22 Diagenesis begins early (1-105 y) and at shallow depths (<1-100 m). Diagenesis Takes place at temperatures higher than those of the near- surface weathering environment, but lower than those producing metamorphism. Generally agreed upon boundary is < 300° C.
Image of page 2
33 = geostatic or lithostatic pressure = hydrostatic pressure Representative pressure fields in sedimentary basins
Image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Click to edit Master subtitle style 44 Idealized Porosity versus Depth curves (Angevine, Heller, & Paola, 1990). z = The main physical process associated with diagenesis is mechanical compaction —the loss of porosity by rearrangement of the grain framework due to overburden pressure.
Image of page 4
55 Important point : Compaction requires sediment deposit to expel water that is filling pore space. Causes thinning of deposit. 41% porosity 37% porosity
Image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Schematic relationship between compaction state and excess pore- fluid pressure. Under-compacted sedimentary deposits tend to have pore-fluid pressure in excess of the hydrostatic pressure. These excess pressures drive subsurface fluid flow and destabilize deposits. 66 Burial Depth
Image of page 6
Click to edit Master subtitle style 77 ODP Leg 180 Site 1115 Depth (meters below sea floor) 1) Porosity change connected to compaction 2) Porosity change connected to compaction + geochemical processes
Image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Click to edit Master subtitle style 88 A & B : Grain contacts start off as point contacts. A → B : As the sediment is buried and compacted, grains are rotated and pushed closer together, and pore space is reduced. C : Pressure can produce grain deformation and fracture. D : Grains start to dissolve in the pore waters at their contacts ( grain contact dissolution ): concavo- convex contacts become important. E : Grain-contact dissolution continues, grain boundaries become irregular or sutured , and original grain shapes are destroyed. Various types of grain contacts found in sandstones .
Image of page 8
Image of page 9
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

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