Northward view over lagoonal setting in which the Llanelly Formation is developing around 340 million years ago, just south of the equator.

Looking south over the lagoon in which the Llanelly Formation is developing. Beyond the lagoon barrier islands formed of sand, shell and crinioid debris almost cut off the lagoon from the open sea. High temperatures produce high rates of evaporation of sea water, concentrating salt to produce hypersaline conditions, which are inhospitable to life except the bacteria and algae which form the stromatolies, which are very common in the Llanelly Formation. The concentration of sea water also leads to the depoistion of lime and dolomite mud directly on the lagoon floor.

Aerial view of the Llanelly Formation depositional environment.

Below, sectional view of features which are to be found in detailed studies of the Llanelly Formation.