The first fossilized evidence of sexual reproduction in eukaryotes is from the Stenian period, about 1 to 1.2 billion years ago.

They date to the end of the Ectasian and start of the Stenian period, about 1,200 million years ago.

In the Rocky Cape Block west of Wynyard and north of Granville Harbour, the Precambrian rocks consist of the Rocky Cape group from the Stenian period, with Cowrie Siltstone, Detention Subgroup, Irby Siltstone, and Jacob Quartzite.