Geology
The site is located near Derby, Western Australia. The shale bed extends inland from King Sound at the coast, forming claypans where it is rarely exposed, with exploratory drilling indicating it is between 650 and 1,000 metres (2,130 and 3,280 ft) thick. The upper parts of the bed are finer layers sediments; these are evident in some ridges of the Erskine range. Outcrops are rather rare, and no type section described, as the formation is only known via infillings within loy-lying synclinal areas, which have not been dissected to any depth suitable for measurement. Outside of drilling, the greatest thickness in any of the localities is 3–6.1 metres (9.8–20.0 ft). It is because of these factors that it is often impossible to deduce which layer of a regular section the beds belong, as these beds are usually isolated exposures. The drilling logs previously recorded are useless in establishing standard sections, because these logs are not detailed enough for precise work.
Despite its name, the Blina Shale is not infact entirely shale, however predominant the ferruginous shale rock is. Some of the basal beds, (not exactly the oldest of the formation) located along the boundary of the synclinal deposition basins comprise of Isaura coquinites. Even more intriguing, a bone bed which may be approximately 3 metres (9.8 ft) is known from these outcrops. Younger beds are often quite sandy and still possess phosphatic intercalation, however these lack bone beds. It is this more sandy composition of the Isaura shales which were given the name "Wonjil Shale", however there is no clear division between the two lithological types, and both hold a similar fossil fauna, and thus the term "Wonjil Shale" is a synonym of Blina Shale.
