Geology is a tricky thing. What you see around you is not the remains of an ancient forest but a geological feature.
The theory for tube formation goes like this. The features are solution pipes formed through the exposure of the local limestone capstone rock to weak acidic solutions. The dissolved limestone (calcium carbonate) in the solution seeps through a sand dune and cements it together to form a hard pipe. The dune formation becomes rock. Subsequent erosion removes the soft rock around the pipe. What is left looks like the petrified trunk of a tree.
Questions for you to answer. Do not post the answers in your logs.
Q1. What is the typical diameter of the solution pipes?
Q2. What force is eroding the softer stone?
Q3. What part of the "petrified forest" suggests that the feature is not formed by trees?
Q4. Describe the weather conditions at the time of your visit. What is the contribution of these conditions to the geology?
Q5. What have you learned from this earthcache experience.
Ref: Syngenetic Karst in Australia: a review, Ken G. Grimes