Lecture-9_diagenesis

Lecture-9_diagenesis - Diagenesis Lithification of...

Info iconThis 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 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
Background image of page 1

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

View Full DocumentRight 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.
Background image of page 2
33 = geostatic or lithostatic pressure = hydrostatic pressure Representative pressure fields in sedimentary basins
Background image of page 3

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

View Full DocumentRight Arrow Icon
Click to edit Master subtitle style 44 Idealized Porosity versus Depth curves 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.
Background 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
Background image of page 5

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

View Full DocumentRight 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
Background image of page 6
Click to edit Master subtitle style 77 ODP Leg 180 Site Depth (meters below sea floor) 1) Porosity change connected to compaction 2) Porosity change connected to compaction + geochemical processes
Background image of page 7

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

View Full DocumentRight Arrow Icon
Click to edit Master subtitle style 88 : 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 .
Background image of page 8
Image of page 9
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 10/04/2010 for the course GEO 26750 taught by Professor Kocurek during the Fall '10 term at University of Texas.

Page1 / 29

Lecture-9_diagenesis - Diagenesis Lithification of...

This preview shows document pages 1 - 9. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online