Reconstructing Geologic History
- describe rocks
- establish sequence of events - principles & fossils
- interpret environments = sedimentary facies
Specific sites within basin =>Depositional Environments
* 2 categories
a) marine, and b) continental
=> sediment texture, composition, and fabric - reflects depositional environment
Interpreting Sedimentary Environments
1. Texture
grain size
shape
- sorting
2. Fossils
- environments and
climate….
- marine vs. continental
3. Fabric = Sedimentary Structures
A. Ripples -
slow-moving fluids….moving sand
B. Cross-Bedding -
movement of large amounts of sand - dunes or bars
Sand Waves
Sedimentary Structures (continued) - other feaures
C. Dessication = mud cracks
D. Activities of organisms =
Trace Fossils
Lateral and Vertical Relationship of Facies (Time & Space)
=> Stratigraphy
=> How does this history recorded in these rocks relate to the region and the rest of the world? - Correlation
Stratigraphic Terminology -
Lithostratigraphy - Units = Group, Formation, Member, Bed
Correlation of stratigraphic units
Types
lithostratigraphic
correlation
similar rock types
Formations
Event Correlation
uses marker beds
ash beds/bentonites
After correlation
can reconstruct regional changes in environments, sea level,
and climate