Function mergeFormationIntervals

Merge into a single column, where higher levels takes precedence over lower levels:

• Sort the intervals by ascending entry depth and ascending stratigraphy unit level
• Start with a stack containing the first item from the sorted list and keep track of the entry depth
• iterate to find the next item that has an entry depth lower than current depth
• define a range limit from the current depth and the entry of the item with a lower entry depth
• pop the stack and draw sections while adjusting the current depth and keep doing this until the current depth reaches the range limit
• any items on the stack with an exit md greater than the limit gets pushed back on the stack
• the current item is pushed to the stack and the iteration continues