The lower two members of the Jurassic to Triassic Kunga Group, the Sadler and Peril formations, represent the main limestone resource of the Queen Charlotte Islands, particularly the basal Sadler limestone. Its thickness varies from less than 30 metres to more than 200 metres.

Massive grey limestone of the Upper Triassic Sadler Formation covers the whole of Limestone Island, a small island covering 700 by 700 metres just east of Louise Island. The limestone is extensively folded and faulted in places and the beds strike northwest and dip gently to the northeast. The analysis of three chip samples representing a 60-metre stratigraphic section on the southwest shore of the island averaged 54.45 per cent CaO, 0.06 per cent MgO and 2.37 per cent insolubles (Bulletin 54, p.175).