The Bouma Sequence
Recently me and my friends were discussing about the turbidity flow and its application on the sedimentary deposits and we came across the Bouma sequence .
That brings us to what are turbidity currents – turbidity currents are a kind of sediment gravity flow where turbulence is the dominating mechanism. Turbulence is the strong movement of air or fluid (in this case water)
What is Bouma sequence?
The Bouma sequence is named after Arnold H. Bouma. The Bouma sequence gives us a five sets of beds which are deposited by turbidity currents. These turbidities are of a medium grained type which are found on the continental slope setting.
This sequence contains 5 beds from A to E. Where A is at the bottom and E is on top. One of its examples is shown below (which contains all the 5 beds)
The above rock shows all the 5 beds of Bouma sequence.
A typical Bouma sequence is shown below.
The above image gives us a fine perspective about the Bouma sequence.
As we go down the energy level increases. Thus according to the turbidity we get
A – sands to gravel at the bottom.
B – Parallel laminae
C – Ripples a convolute bedding , cross laminated sands
D – Parallel laminated silts
E – Muds , ungraded which are Hemiplagic towards the top. Turbidite mud towards bottom.
Above E we get pelagic sedimentation.
My next blog is about “is the Bouma sequence obsolete?”