1. Posting Geometric Observation
The ABC Method
Tr = Truncation
Tp = Toplap
C = Concordant
On = Onlap
Dn = Downlap
C = Concordant
A - B C
p = parallel m = mounded ob = oblique progradation
sub = subparallel w = wavy sig = sigmoid progradation
div = divergent rf = reflection free sh = shingled
SLIDE 5
We need a method to make geometric observations and post them on a map before we can make predictions
The method we use is called the ABC method
Although it looks like a formula, it is more a template for recording observations
The A term is the type of termination pattern at the top of the sequence
erosional truncation, toplap, or concordance, i.e., no terminations
The B term is the type of termination pattern at the base of the sequence
onlap, downlap, or concordance, i.e., no terminations
The C term is the internal reflection pattern, e.g., parallel
The next few slides show some common internal reflection patterns
A way to remember the code is to think:
A = Above; B = Below; C = Center
A = Termination Pattern at the Upper Sequence Boundary
B = Termination Pattern at the Lower Sequence Boundary
C = Internal Reflection Pattern
Courtesy of ExxonMobil
L 11 – Stratigraphic Analysis