Transcript 455_3_06

Who we are
Geologic materials
Rocks (including high
and low porosity &
crystalline), unlithified
or poorly lithified
sediments, and soils
Primary versus Secondary
Form when the rock
forms, thus provide a
record of geologic
May be present in
volcanic, and
intrusive rocks
The former two cases
generally have better
way-up indicators
Modify - sometimes
obliterate - primary
Commonly, though
not always, oblique to
primary structures
May be continuous
(pervasive) or
Why we care about primary structures
in a structural geology class
Being able to distinguish
primary from secondary
structures is critical to
reading rock record
Geologic history
Way-up indicators
Material controls on
What is the rock type?
 What do structures look like (e.g. shape,
continuous or discontinuous, etc.)?
 Is it homogeneous or heterogeneous?
Isotropic or anisotropic?
 Is it primary or secondary?
 How would you interpret this structure?
Can it be used as a way-up indicator?