• Discuss the following question with the people around you:
• What controls the distribution of fossils through time in the rock record?
What is Stratigraphy?
• Temporal and spatial relationships of layered rocks
DEPOSITIONAL ENVIRONMENTS AND SEDIMENTARY FACIES
• What does a layer of rock represent and why does it change laterally?
• Sedimentary Facies
– Total aspect of the rock
• Depositional Environments
– Have limited lateral extent and grade into one another
T & R and Facies Patterns
• Why are sedimentary rocks/strata layered?
• Facies shift positions through time
• Transgression - landward shift
• Regression - seaward shift
Walther’s Law
• Vertically stacked facies were once adjacent environments
• Only applies within conformable intervals of rock
• Does this interval represent a transgression or regression?
Local vs. Worldwide T&R’s
• Global Changes in Sea Level = Eustatic Changes
• Mechanisms
• Plate tectonics
• Changes in Global Ice Volume
Local vs. Worldwide T&R’s
• Local Changes in Sea Level = Relative Change
• Change along any coastline function of
• Eustacy
• Sediment supply
• Tectonics - subsidence and uplift
• Coastal configuration
Biostratigraphy
• Since formations and facies change laterally - how do we keep track
of time?
• Biostratigraphy
• Biozones (index fossils)
• Range of occurrence
• FAD’s and LADS
• Concurrent range zones
Biostratigraphy
• What are the requirements of a good index fossil
• Common
• Widespread
• Distribution not determined by environment - facies fossils
• Short lived (as a species)
Biostratigraphy
• Common Groups
– Ammonites
– Conodonts
– Foraminifera
Rocks and Time
• How well do intervals of layered rock record time?
• Factor = sedimentary accumulation rates
Stratigraphic Completeness
• The temporal record in layers of rock?
• Which environments are more complete
– Terrestrial or Marine?
• Marine - 15 - 70%
• Terrestrial - 9 - 54%