Thank you for an interesting critique. You are right. Both the Elliott and the Clarens Formations are part of the Karoo Supergroup in the geological Main Karoo Basin but the towns of Elliott and Clarens, after which they were named, are not in the geographical Karoo after which the Karoo Supergroup was named. I am not sure what you mean by "... unlikely to be non-biogenic." and "... organic unloading". The structures are not essentially biogenic in origin and are the result of downward weathering and erosion of the sandstone along joint planes and even along some negatively weathering dolerite dykes.
The rifting and subsequent fragmentation of Gondwana was post-Clarens in origin. Is your Subject Geology? You must really visit sometime. I am sure you will find the landscape very interesting and beautiful.
Clarens Formation (22)