Sedimentary Structures: • Features in Sedimentary Rocks That Reflect Depositional Or Diagenetic Processes

Sedimentary Structures: • Features in Sedimentary Rocks That Reflect Depositional Or Diagenetic Processes

Sedimentary Structures: • Features in sedimentary rocks that reflect depositional or diagenetic processes. – Diagenesis: • physical and/or chemical changes to sediments following deposition and up to metamorphism. Sedimentary Structures: • Sedimentary structures can sometimes yield information on: – paleocurrent direction, and – stratigraphic “up” direction • Latter is useful if working in folded and potentially overturned rocks. Sedimentary Structures: • 1) bedding: – sediments deposited in layers (most commonly parallel to Earth’s surface) a bed If layers are thinner than 1 cm, typically termed “laminations”! Sedimentary Structures: • 2) graded bedding: – coarser sediments on bottom Deposition from a waning current Sedimentary Structures: • 2) graded bedding: Sedimentary Structures: • 2) graded bedding: Sedimentary Structures: • 2) graded bedding: Sedimentary Structures: • 3) imbricated clasts: – flattened clasts imbricated in stream bottom: current direction Can’t be used for stratigraphic “up” Sedimentary Structures: • 3) imbricated clasts: Sedimentary Structures: • 3) imbricated clasts: Sedimentary Structures: • 4) Sole Marks & Casts: – Sedimentary structures preserved on the underside of a bed – Typically an infilling (cast) of a depression in the underlying bed Original structure! (e.g., groove)! Cast of original structure! (e.g., groove cast)! Sedimentary Structures: • 4) Sole Marks I; flute casts – Scoured out depressions in mud (usually associated with turbidity currents). sand mud mud up sand paleocurrent Steep side faces current! Sedimentary Structures: • 4) flute casts: Sedimentary Structures: • 4) flute casts: Sedimentary Structures: • 4) flute casts: Sedimentary Structures: • 4) Sole Marks II: groove casts Sedimentary Structures: • 5) current ripple marks: Current ripples are asymmetric… current erosion deposition not equal Sedimentary Structures: • 5) current ripple marks: Sedimentary Structures: • 5) current ripple marks: trough cross-bedding Three-dimensional ripples Sedimentary Structures: • 6) oscillation ripple marks: oscillation ripples are symmetric… current up Sedimentary Structures: • 6) oscillation ripple marks : Sedimentary Structures: • 7) cross beds : – Internal structure of ripples or dunes current Note: beds are truncated on their tops up Sedimentary Structures: • 7) cross beds : Sedimentary Structures: • 7) cross beds : Sedimentary Structures: • 7) cross beds : Sedimentary Structures: • 8) herringbone cross beds: Common in areas with tidal influence… Sedimentary Structures: • 8) herringbone cross beds: Sedimentary Structures: • 9) mudcracks : – Formed in drying mud. contracts on top first mud up Sedimentary Structures: • 9) mudcracks: Sedimentary Structures: • 9) mudcracks in rocks: .

View Full Text

Details

  • File Type
    pdf
  • Upload Time
    -
  • Content Languages
    English
  • Upload User
    Anonymous/Not logged-in
  • File Pages
    30 Page
  • File Size
    -

Download

Channel Download Status
Express Download Enable

Copyright

We respect the copyrights and intellectual property rights of all users. All uploaded documents are either original works of the uploader or authorized works of the rightful owners.

  • Not to be reproduced or distributed without explicit permission.
  • Not used for commercial purposes outside of approved use cases.
  • Not used to infringe on the rights of the original creators.
  • If you believe any content infringes your copyright, please contact us immediately.

Support

For help with questions, suggestions, or problems, please contact us